• TABLE OF CONTENTS
HIDE
 Front Cover
 Title Page
 Northwest Florida water management...
 Table of Contents
 List of Figures
 List of Tables
 Executive summary
 Existing stormwater related...
 Stormwater management alternat...






Group Title: Water resources assessment ; 94-2
Title: City of Quincy stormwater management plan
CITATION PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/AM00000214/00001
 Material Information
Title: City of Quincy stormwater management plan executive summary
Series Title: Water resources assessment
Alternate Title: Stormwater management plan
Physical Description: v, 34 leaves : maps ; 28 cm.
Language: English
Creator: Arteaga, Ruben
Bartel, Ronald L
Ard, Felton B
Northwest Florida Water Management District (Fla.)
Publisher: Northwest Florida Water Management District
Place of Publication: Havana Fla.
Publication Date: [1994]
 Subjects
Subject: Urban runoff -- Planning -- Florida -- Quincy   ( lcsh )
Flood control -- Planning -- Florida -- Quincy   ( lcsh )
Storm sewers -- Planning -- Florida -- Quincy   ( lcsh )
Watershed management -- Florida -- Quincy   ( lcsh )
Quincy (Fla.)   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Ruben Arteaga, Ronald L. Bartel and Felton B. Ard.
General Note: "May 1994."
 Record Information
Bibliographic ID: AM00000214
Volume ID: VID00001
Source Institution: Florida Agricultural and Mechanical University
Holding Location: Florida A&M University (FAMU)
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 31230059

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Page i
    Northwest Florida water management district governing board
        Page ii
    Table of Contents
        Page iii
    List of Figures
        Page iv
    List of Tables
        Page v
    Executive summary
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Watershed characteristics
            Page 6
            Geology
                Page 6
            Surface water
                Page 6
                Page 7
                Page 8
                Page 9
            Groundwater
                Page 10
            Land use
                Page 10
        Existing stormwater drainage system
            Page 11
            Quincy Creek watershed at state road 267
                Page 11
                Page 12
            Tanyard branch at Highway 268
                Page 13
            Experiment station road watershed
                Page 14
    Existing stormwater related problems
        Page 15
        Flooding problems
            Page 15
            Shelter St. and experiment station road
                Page 15
            Virginia Street drainage ditch
                Page 15
            Main Street and Washington Street
                Page 15
                Page 16
                Page 17
            12th Street and SAL Mine Spur Rail Road
                Page 18
            Quincy Creek and state road 267
                Page 18
            King Street and Monroe Street
                Page 18
            Tanyard branch at Adams Street, Stewart Street and Key Street
                Page 18
        Water supply problems
            Page 19
            Existing operations
                Page 19
            Alternative operations
                Page 20
                Page 21
        Water quality problems
            Page 22
            Quincy Creek
                Page 22
            Tanyard branch
                Page 22
        Stormwater quality evaluation
            Page 23
            Summary of water quality sampling results
                Page 23
                Page 24
            Water quality sampling results
                Page 25
            Lodaing rate relationships with existing land use
                Page 25
            Future land use loading projections
                Page 26
            Relationships to historical water quality data
                Page 26
                Page 27
    Stormwater management alternatives
        Page 28
        Flood reduction alternatives analysis
            Page 28
            Page 29
            Page 30
        Stormwater quality alternatives analysis
            Page 31
            Urban runoff pollution control alternatives
                Page 31
            Alternatives for improving the quality of raw water supplies
                Page 32
                Page 33
            Stormwater quality monitoring alternatives
                Page 34
Full Text



CITY OF QUINCY


STORMWATER MANAGEMENT PLAN


EXECUTIVE SUMMARY


NORTHWEST FLORIDA
WATER MANAGEMENT DISTRICT


WATER RESOURCES ASSESSMENT 94-2


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CITY OF QUINCY STORMWATER MANAGEMENT PLAN

EXECUTIVE SUMMARY













By

Ruben Arteaga, Ronald L. Bartel and Felton B. Ard



















Northwest Florida Water Management District
Water Resources Assessment 94-2


May 1994












NORTHWEST FLORIDA WATER MANAGEMENT DISTRICT


GOVERNING BOARD



Charles W. Roberts, Chairman
Hosford


E. Hentz Fletcher, Jr., Vice-Chairman
Quincy


Bennett T. Eubanks, Secretary/Treasurer
Blountstown


John O. DeLorge
Cantonment

John R. Middlemas, Jr.
Panama City


George Willson
Tallahassee

M. Copeland Griswold
Chumuckla


Robert L. Howell
Apalachicola

Roger H. Wright
Valparaiso


Douglas E. Barr- Executive Director


For additional information, write or call:

Northwest Florida Water Management District
Route 1, Box 3100
Havana, Florida 32333-9700
(904) 539-5999









TABLE OF CONTENTS
Page

LIST OF FIGURES.................................................................. .....................................................

LIST OF TABLES ..................................... ............. ................................................................. iii

EXECUTIVE SUMMARY ........................................................................................ ..................... 1
W watershed Characteristics................................................. .... ........................................... 6
Geology ........................................................ 6
Surface W after ....................................................... .................................................... 6
Groundwater .................................................................................................................... 10
Land Use .............................................................................. ..................................... 10
Existing Stormwater Drainage System ....................................... ....................................... 11
Quincy Creek W atershed at State Road 267 .................. .................................................. 11
Tanyard Branch at Highway 268....................................................................................... 13
Experiment Station Road W atershed.................................................................. 14

EXISTING STORMW ATER RELATED PROBLEMS............................................... ................ 15
Flooding Problems .......................................................................... ............................. 15
Shelfer St. and Experiment Station Road .................. ............................... .................. 15
Virginia Street Drainage Ditch................................................. 15
Main Street and W ashington Street............................................................................ 15
12th Street and SAL Mine Spur Rail Road.................................................................. 18
Quincy Creek at State Road 267.......................................................... ................ 18
King Street and Monroe Street..................................... ........................................ 18
Tanyard Branch at Adams Street, Stewart Street and Key Street............................... 18
W after Supply Problems ................................................... ................................................. 19
Existing Operations............... .............................. ................................................ 19
Alternative Operations................................................. ................................................ 20
W after Quality Problems.................................................... ................................................. 22
Quincy Creek.................................................................................................................... 22
Tanyard Branch......................................................................................... 22
Stormwater Quality Evaluation........................ ...................................... ................ 23
Summary of W ater Quality Sampling Results ...........................................--.............. 23
W ater Quality Sampling Results ............................................. ..... ...... .................... 25
Loading Rate Relationships with Existing Land Use........... ................................... ........... 25
Future Land Use Loading Projections..... ....................................................................... 26
Relationships to Historical W ater Quality Data.................. ................................ ................ 26

STORMW ATER MANAGEMENT ALTERNATIVES.................................. .............................. 28
Flood Reduction Alternatives Analysis................ ..... .... .. .......... ................... 28
Stormwater Quality Alternatives Analysis...................................................... .................... 31
Urban Runoff Pollution Control Alternatives............................................... ................. 31
Alternatives for Improving the Quality of Raw W ater Supplies ..................................... 32
Stormwater Quality Monitoring Alternatives................. ......................... 34











LIST OF FIGURES

Page

Figure 1 Map of Study Area.................................................................................................. 7

Figure 2 Subbasin Delineation of Study Area........................................... .......................... 8

Figure 3 Flood Prone Areas in Study Area.................................................... .................... 17









LIST OF TABLES


Page

Table 1 Existing and Projected Water Demand for Quincy Creek Water Users........................ 9

Table 2 Identified Problems Within City Limits and Proposed Recommendations.................. 16

Table 3 Evaluation of Flood Control Alternatives.............................................................. 29










EXECUTIVE SUMMARY


This report summarizes the findings and recommendations associated with the development of a
comprehensive stormwater management plan for the City of Quincy, Florida. The objective of this study
was to identify the most pressing stormwater problems that the City of Quincy experiences and
recommend a series of cost effective improvements that may be implemented in a timely manner
according to their priority. As identified in the scope of services of the main report', recommendations
were addressed for the most severe and urgent stormwater problems identified by City of Quincy officials
and local residents. The majority of these problems occur within City limits and can be categorized in
three groups. The first category of problems is associated with local flooding due to inadequacies of the
stormwater drainage system. The second category of problems is related to inadequacies of the city's
current water supply system. Finally, since little was known about the quality of the stormwater runoff in
the study area, water quality condition and problems in the study area needed to be identified and
assessed.

The study area is bounded by the City limits, however, because of modeling requirements, the
Upper Quincy Creek watershed above Highway 267 is also included (see Figure 1). This study is the first
of its kind in the study area and contains a number of features that include:


1. A detailed hydrologic and hydraulic computer model for the study area, calibrated and verified to
the extent the available data permitted. This model was the main tool for the development of
stormwater management strategies for both existing and future planning purposes.

2. The quantity and quality characteristics of stream flow were defined strictly on the basis of a
sampling program specifically for the study area.

3. Alternatives for flood control were based on cost and effectiveness.

4. The downstream impacts of flood control alternatives can be evaluated for existing and future
planning scenarios.

5. Water quality and water supply issues are considered in the plan.


The stormwater management models, the results of which are discussed herein, were designed
to provide a City-wide modeling capability for many structural and non-structural measures. Traditionally,
stormwater flooding problems are addressed at a localized scale without any regard for downstream
quantity or quality impacts. For this study, the finished product consists of watershed models (runoff,
transport and backwater models) that represent the major interconnections between subwatersheds and
a collection of data to address a broad range of problems throughout the study area.

Traditionally, the accuracy and reliability of deterministic hydrologic models depend on the quality
and quantity of the available data for calibration and verification. Prior to this study, minimal hydrologic
data existed making necessary the development of a new data collection program to meet the study's
specific needs. For long-term planning purposes, the models were designed to accurately simulate flows
and flood levels on a long-term-basis from 34 years of historical rainfall data from nearby weather
stations. The final version of the refined hydrologic model included 57 subbasins with one short-term
rainfall record and four flow rate calibration locations. Field data used to characterize the conveyance
system in the model was provided by the City staff.


1 Ruben Arteaga, Ronald B. Bartel and Felton B. Ard. City of Quincy Stormwater Management Plan, Northwest
Florida Water Management District, Water Resources Assessment 94-1, May 1994.











Only the most pressing flooding problems were considered for analysis. No damage analysis
was carried out to justify alternative expenditures. The costs of structural alternatives to alleviate flooding
problems were justified on the basis of cost and effectiveness. The unit cost of materials and labor for
alternative prioritization was based on best knowledge of current market prices. It must be recognized
that the final cost of implementing these alternatives may differ from those from the final engineering
analysis. All the flooding problem areas identified by City officials and residents are encompassed within
City limits.

Problems with the City's water supply are related to the upper portion of the Quincy Creek
drainage area northeast of the City. Further investigation along the major drainage runs was intended to
reveal the actual extent of flooding and water quality problems. This included estimates of flooding levels
and pollutant loadings on a subbasin scale. A detailed drought analysis for the upper portion of Quincy
Creek was carried out to analyze possible measures to upgrade the quality and reliability of Quincy Creek
as the City's surface water source.

Because of the limited amount of water quality data available prior to this report, a new sampling
effort was carried out as part of this study. However, due to budgetary restrictions, the sampling effort
was limited to four samples at four flow gauging locations. The water quality information generated
during this study, although sufficient for the purposes of this plan, does not necessarily produce an ample
picture of the water quality problems throughout the study area. Implementation of any of the
recommendations in this study would be better achieved if additional water quality data was obtained
before and after implementation takes place.

The principal tasks accomplished during this study include the following:

Development of a computerized hydrologic and geographic data base of the study area.

Measurement of stormwater flow and quality data at key locations within the drainage system.

Development of hydrologic and hydraulic computer models capable of accurately reproducing
streamflow conditions in the drainage system of the study area.

Estimates of flooding and water quality conditions associated with urban and non-urban
development in the study area.

Evaluation and recommendations of feasible structural and nonstructural measures to control
and mitigate flooding, water supply and water quality problems in the study area.


Problem areas were identified and prioritized on the basis of frequency and severity of structural
and street flooding. The prioritized problem areas in this study are:

Twelfth Street and Rail Road north of King Street (structural residential flooding)

King Street and Monroe Street (street flooding)

Main Street and Washington Street (street flooding)

Experiment Station Road and Shelfer Street (structural residential and industrial flooding)

Tanyard Branch at Adams, Stewart and Key Street (localized flooding and bank erosion)









Tanyard Branch at Adams Street (elevated zinc, cadmium, chromium, nutrients and turbidity
levels violate Class III standards)

Quincy Creek at water treatment plant (high turbidity)

Virginia Street Drainage Ditch (street flooding)


The recommended improvements for flood control were evaluated and ranked on the basis of
their effectiveness for reducing flooding. Since most of the flooding problems within the City limits are
associated with inadequate conveyances in the drainage system, it was important to evaluate
downstream impacts of proposed structural alternatives. Most flood control measures investigated in this
report consisted of conduit conveyance enlargements. The recommendations regarding culvert
enlargements were based on reducing the most frequent flooding (events with return period of five years
or less) since most of the flooding associated with the storm sewer system only floods streets and does
not produce significant structural damage. Large event flooding cannot be significantly reduced without
extensive modifications to the drainage system that most likely includes the addition of storage capacity
into the system; or without the risk of increasing downstream flooding to areas that did not experience
previous flooding.

Several alternatives were analyzed with the purpose of increasing the water availability and
quality to meet current and future water needs. The focal point of this analysis was the use of the
Interlocking Lakes as a supplemental source of water. Present water demand from Quincy Creek is 2.5
cfs in an average day and 3.5 cfs the maximum in one day. Water availability and quality analyses
revealed that flows from the lakes exceeded 3.5 cfs about 99.9 percent of an average 18-year period.
Results from the low flow analysis in Colson Creek indicate that an additional intake on Colson Creek
would be adequate in quantity and quality to supplement Quincy Creek's supply.

Water quality alternatives were analyzed on a subbasin scale using loading rates from the
literature and the flow characteristics as predicted with the model. Subbasins were examined and
prioritized under existing and future development conditions for pollutant load generation. After analyzing
land use changes from existing to future conditions and their effect in pollutant loadings, it was found that
there is little change in loading generation between existing and a future planning scenario (Year 2001).
This loading analysis revealed that most of the loading increases take place in the subbasins draining into
Quincy Creek west of State Road 268 and in the east in subbasins just south of the airport. The
increases in pollutant loadings were due to land use shifts from vacant or open land to residential,
commercial and industrial. Water supply alternatives were explored to increase the adequacy, in terms of
quantity and quality, of Quincy Creek as the main source of surface water for the City.

The following is a list of stormwater management alternatives considered in the development of
this plan indicating which alternatives are recommended for implementation.



1. Flood Control Alternatives

Nonstructural

Land purchase of affected structures at 12th Street and rail road (recommended).

Land use code application and enforcement within City limits to restrict development in
flood plain areas (recommended).










Structural

Storm sewer enlargements (see Stormwater Alternatives for details) on King Street East
Branch from railroad tracks to King Street.

Pipe enlargement on King Street West Branch along King Street sewer line (Alternative
"A") from Main Street and Washington Street to sewer outlet into Quincy Creek
(recommended).

Pipe enlargement on King Street West Branch West (Alternative "B") from Main Street
and Jefferson Street to sewer outlet into Quincy Creek.

Pipe enlargement on Monroe Street sewer line (Alternative "A") from King Street to
Washington Street (recommended).

Pipe enlargement on Adams Street sewer line (Alternative "B") from King Street to Clark
Street.

Cleanup and maintenance of stormwater drainage ditch between Experiment Station
Road and Hamilton Street. Preserve flood plain from development (recommended).

Cleanup and maintenance of stormwater drainage ditch from Virginia Street to Cox Creek
(recommended).



2. Surface Water Supply Alternatives

Nonstructural

Identify problem areas that may need further protection through the application and
enforcement of land use controls (recommended).

Explore the potential of watershed protection by land acquisition wherever possible in the
Colson Creek, Upper and Middle Quincy Creek watersheds (recommended).

Consider, with the County, stricter regulatory and enforcement programs for land use,
erosion and turbidity controls in the Upper Quincy Creek Watershed.

Investigate feasibility of paving dirt roads in the Upper and Middle Quincy Creek flood
plain.


Structural

Detailed reservoir capacity analysis, including storage volume and firm yield, for
additional water supply intake on Colson Creek (recommended).











3. Urban Runoff Pollution Control Alternatives


Nonstructural

*Application and enforcement of the Florida Administrative Code (F.A.C.) 17-25 for new
development and redevelopment. F. A. C. 17-25 addresses stormwater permitting for all
new stormwater discharges and modifications to existing development that increases
pollutant loading (recommended).

Structural

Consider regional treatment facilities to be paid for by future development and
redevelopment to meet F.A.C. regulations and possible future federal requirements.
Explore long-term funding mechanisms such as stormwater utility fees (recommended).



4. Stormwater Monitoring Alternatives

Short-term water quality monitoring of Colson Creek upstream of the lakes, at the lakes
and downstream of Interlocking Lakes (recommended).

Water quality monitoring of Quincy Creek upstream of the water treatment plant to
determine source and severity of water quality violations recommendedd).

Monitor Quincy Creek at State Road 267 and Colson Creek to extend the long-term
record and continued drought reliability and firm yield analysis (recommended).

Continuous monitoring of Tanyard Branch before it discharges into Quincy Creek to
monitor water quality improvements from the application of structural and nonstructural
control measures such as the removal of the effluents from the waste water treatment
plant.









Watershed Characteristics


The City of Quincy is located near the center of Gadsden County at the center of the Florida
Panhandle. The study area is comprised of the upper portion of Quincy Creek, Tanyard Branch and a
small portion of the upper Rocky Comfort Creek. The area considered covers approximately 28.25
square miles (18,028 acres) and contains most of the city and the upper portion of Quincy Creek as
shown in Figure 1. This is the contributing drainage area for Quincy Creek just downstream of the
sewerage treatment plant at the confluence of Quincy Creek and Tanyard Branch. The area of
investigation drains a portion of the Ochlockonee River Basin, hydrologic number 03120003 (Hydrologic
Unit Map -- 1974). Quincy Creek discharges into Little River, about 3 miles east of Quincy which in turn
drains into Lake Talquin, 8 miles south of Quincy. Eventually these waters are drained into the Gulf of
Mexico by the Ochlockonee River. For the purpose of this study, the study area was subdivided into 26
subbasins (Figure 2). This subdivision was necessary to analyze with more detail problem areas or areas
of interest.

Geology

The study area is in the region known as the Northern Highlands. Those portions of the Northern
Highlands found to the east of the Marianna Lowlands form the Tallahassee Hills. This physiographic
region is characterized by land surfaces high in elevation and generally above the piezometric surface.
Structurally, the area is part of an extensive depositional trough known as the Gulf Trough, which runs
through Quincy and extends to the northeast into Georgia and to the southwest into the Gulf of Mexico.
The study area lies on a portion of this trough in which the sediments underlying the area thicken to the
west. The main groundwater producing zone is about 600 feet deep and mainly made up of limestones.
Confining the upper surface of the aquifer is a layer of low permeability sediments approximately 200-feet
thick that restricts recharge into and discharge from the aquifer. As a consequece, saline groundwater
trapped in the bottom portion of the aquifer makes the water baring zone unreliable for water supply
purposes.

The study area encompasses two major geologic formations: the Hawthorn and the Miccosukee
Formations. The Hawthorn Formation is generally located near the ground surface beneath a thin cover
of residuum, soil or alluvium. It can be found along the major streams in the area such as Quincy Creek,
Tanyard Branch and their tributaries. This formation, which varies in depth from 100 to 250 feet, contains
highly productive deposits of fuller's earth, a valuable mineral used in industry as an absorbent. The
Miccosukee Formation is made up mostly of gravel, sand and clay and is more extensive and uniform
covering most of the area within City limits. This formation can be found at depths varying from 0 to 80
feet overlying the Hawthorn Formation.

Unconsolidated deposits extensively cover the preceding formations appearing as silt and muck
in swamp areas and sand and silt in the flood plain areas of streams.

Surface Water

Quincy Creek is the most significant surface water drainage feature located within the study area.
This stream drains an area of about 40.7 square miles before it joins the waters of the Little River.
Quincy Creek headwaters are located northwest of Quincy near the City of Gretna. This upper portion of
Quincy Creek drains approximately 5.3 square miles of land northwest of Highway 268. Most of the
surface waters drained by the upper Quincy Creek originate from runoff from undeveloped land used
mostly for agriculture, mining and silviculture. The middle portion of Quincy Creek as identified in this
study is located between Highways 268 and 12, and coincides with the northern border line of the City.
Urban runoff from an area of 620 acres in the northern portion of the City, drain into this portion of Quincy
Creek. The lower portion of Quincy Creek was designated in this study between Highway 12 and the
junction with Little River. It is in this segment of the creek where runoff from Tanyard Branch and the









Watershed Characteristics


The City of Quincy is located near the center of Gadsden County at the center of the Florida
Panhandle. The study area is comprised of the upper portion of Quincy Creek, Tanyard Branch and a
small portion of the upper Rocky Comfort Creek. The area considered covers approximately 28.25
square miles (18,028 acres) and contains most of the city and the upper portion of Quincy Creek as
shown in Figure 1. This is the contributing drainage area for Quincy Creek just downstream of the
sewerage treatment plant at the confluence of Quincy Creek and Tanyard Branch. The area of
investigation drains a portion of the Ochlockonee River Basin, hydrologic number 03120003 (Hydrologic
Unit Map -- 1974). Quincy Creek discharges into Little River, about 3 miles east of Quincy which in turn
drains into Lake Talquin, 8 miles south of Quincy. Eventually these waters are drained into the Gulf of
Mexico by the Ochlockonee River. For the purpose of this study, the study area was subdivided into 26
subbasins (Figure 2). This subdivision was necessary to analyze with more detail problem areas or areas
of interest.

Geology

The study area is in the region known as the Northern Highlands. Those portions of the Northern
Highlands found to the east of the Marianna Lowlands form the Tallahassee Hills. This physiographic
region is characterized by land surfaces high in elevation and generally above the piezometric surface.
Structurally, the area is part of an extensive depositional trough known as the Gulf Trough, which runs
through Quincy and extends to the northeast into Georgia and to the southwest into the Gulf of Mexico.
The study area lies on a portion of this trough in which the sediments underlying the area thicken to the
west. The main groundwater producing zone is about 600 feet deep and mainly made up of limestones.
Confining the upper surface of the aquifer is a layer of low permeability sediments approximately 200-feet
thick that restricts recharge into and discharge from the aquifer. As a consequece, saline groundwater
trapped in the bottom portion of the aquifer makes the water baring zone unreliable for water supply
purposes.

The study area encompasses two major geologic formations: the Hawthorn and the Miccosukee
Formations. The Hawthorn Formation is generally located near the ground surface beneath a thin cover
of residuum, soil or alluvium. It can be found along the major streams in the area such as Quincy Creek,
Tanyard Branch and their tributaries. This formation, which varies in depth from 100 to 250 feet, contains
highly productive deposits of fuller's earth, a valuable mineral used in industry as an absorbent. The
Miccosukee Formation is made up mostly of gravel, sand and clay and is more extensive and uniform
covering most of the area within City limits. This formation can be found at depths varying from 0 to 80
feet overlying the Hawthorn Formation.

Unconsolidated deposits extensively cover the preceding formations appearing as silt and muck
in swamp areas and sand and silt in the flood plain areas of streams.

Surface Water

Quincy Creek is the most significant surface water drainage feature located within the study area.
This stream drains an area of about 40.7 square miles before it joins the waters of the Little River.
Quincy Creek headwaters are located northwest of Quincy near the City of Gretna. This upper portion of
Quincy Creek drains approximately 5.3 square miles of land northwest of Highway 268. Most of the
surface waters drained by the upper Quincy Creek originate from runoff from undeveloped land used
mostly for agriculture, mining and silviculture. The middle portion of Quincy Creek as identified in this
study is located between Highways 268 and 12, and coincides with the northern border line of the City.
Urban runoff from an area of 620 acres in the northern portion of the City, drain into this portion of Quincy
Creek. The lower portion of Quincy Creek was designated in this study between Highway 12 and the
junction with Little River. It is in this segment of the creek where runoff from Tanyard Branch and the









Watershed Characteristics


The City of Quincy is located near the center of Gadsden County at the center of the Florida
Panhandle. The study area is comprised of the upper portion of Quincy Creek, Tanyard Branch and a
small portion of the upper Rocky Comfort Creek. The area considered covers approximately 28.25
square miles (18,028 acres) and contains most of the city and the upper portion of Quincy Creek as
shown in Figure 1. This is the contributing drainage area for Quincy Creek just downstream of the
sewerage treatment plant at the confluence of Quincy Creek and Tanyard Branch. The area of
investigation drains a portion of the Ochlockonee River Basin, hydrologic number 03120003 (Hydrologic
Unit Map -- 1974). Quincy Creek discharges into Little River, about 3 miles east of Quincy which in turn
drains into Lake Talquin, 8 miles south of Quincy. Eventually these waters are drained into the Gulf of
Mexico by the Ochlockonee River. For the purpose of this study, the study area was subdivided into 26
subbasins (Figure 2). This subdivision was necessary to analyze with more detail problem areas or areas
of interest.

Geology

The study area is in the region known as the Northern Highlands. Those portions of the Northern
Highlands found to the east of the Marianna Lowlands form the Tallahassee Hills. This physiographic
region is characterized by land surfaces high in elevation and generally above the piezometric surface.
Structurally, the area is part of an extensive depositional trough known as the Gulf Trough, which runs
through Quincy and extends to the northeast into Georgia and to the southwest into the Gulf of Mexico.
The study area lies on a portion of this trough in which the sediments underlying the area thicken to the
west. The main groundwater producing zone is about 600 feet deep and mainly made up of limestones.
Confining the upper surface of the aquifer is a layer of low permeability sediments approximately 200-feet
thick that restricts recharge into and discharge from the aquifer. As a consequece, saline groundwater
trapped in the bottom portion of the aquifer makes the water baring zone unreliable for water supply
purposes.

The study area encompasses two major geologic formations: the Hawthorn and the Miccosukee
Formations. The Hawthorn Formation is generally located near the ground surface beneath a thin cover
of residuum, soil or alluvium. It can be found along the major streams in the area such as Quincy Creek,
Tanyard Branch and their tributaries. This formation, which varies in depth from 100 to 250 feet, contains
highly productive deposits of fuller's earth, a valuable mineral used in industry as an absorbent. The
Miccosukee Formation is made up mostly of gravel, sand and clay and is more extensive and uniform
covering most of the area within City limits. This formation can be found at depths varying from 0 to 80
feet overlying the Hawthorn Formation.

Unconsolidated deposits extensively cover the preceding formations appearing as silt and muck
in swamp areas and sand and silt in the flood plain areas of streams.

Surface Water

Quincy Creek is the most significant surface water drainage feature located within the study area.
This stream drains an area of about 40.7 square miles before it joins the waters of the Little River.
Quincy Creek headwaters are located northwest of Quincy near the City of Gretna. This upper portion of
Quincy Creek drains approximately 5.3 square miles of land northwest of Highway 268. Most of the
surface waters drained by the upper Quincy Creek originate from runoff from undeveloped land used
mostly for agriculture, mining and silviculture. The middle portion of Quincy Creek as identified in this
study is located between Highways 268 and 12, and coincides with the northern border line of the City.
Urban runoff from an area of 620 acres in the northern portion of the City, drain into this portion of Quincy
Creek. The lower portion of Quincy Creek was designated in this study between Highway 12 and the
junction with Little River. It is in this segment of the creek where runoff from Tanyard Branch and the














































City Limits


Figure 1. Map of Study Area
















Sub- Area
bsin (Acres)
1 8643
2 1868
3 3W1
4 345
5 111

6 202



9 287


S11 221
12 66
13 96
14 1488
16 224


17 27


18 81





42 26 347




Figure 2. Subbasin Delineation of Study Area
24 2M
j 25 -"6
g V ^ 26 347








Figure 2. Subbasin Delineation of Study Area










effluents from the City's wastewater treatment plant meet just east of the municipal wastewater treatment
plant. A current project is under way that will allow the City to dispose the effluent from the wastewater
treatment plant in a more suitable fashion.

North of Quincy, Colson Creek drains the Interlocking Lakes into Quincy Creek. These man-
made lakes, a product of past mining operations, provide storage for stormwater runoff and groundwater
flow from an area of about 6,800 acres of pine forests, agricultural land and mineral mines. Waters
released from these lakes join Quincy Creek about half a mile upstream of the City's water treatment
plant. The Colson Creek subbasin is of special interest in this study because of its potential to supply
good quality water for the City. As it occurs several times per year, the current supply from Quincy Creek
becomes temporarily inadequate after significant storm events due to high turbidity levels in the creek's
waters.

About 400 feet downstream of the water treatment plant, on the east side of Highway 267, there
is a U.S. Geological Survey long-term discharge and water quality monitoring station which has operated
for the past 18 years. The discharge at this flow gauge is periodically affected by the withdrawals from
the water treatment plant and other upstream users. The major upstream users of water from the creek
and their water demands are identified in Table 1.

Historical data about severe floods in the Creek is very limited with only one flood with a return
period greater than 25 years while the stream has been monitored (March 3, 1991). The absolute peak
discharge (about 100-year return period) was associated with a hurricane on September 22, 1969.
Although the period of record does not extend back to the time of this storm, the U.S. Geological Survey
has determined a peak flow based on indirect methods and high water marks.









TABLE 1
Existing and Projected Water Demand for Quincy Creek Water Users

Existing Demand Projected Demand
Permitted Water Average Daily Maximum Daily Average Daily Maximum Daily
User GPD (cfs) GPD (fs) GPD (cfs) GPD (cfs)
City of Quincy 1,300,000 (2.0) 1,700,000 (2.6) 1,7000 (2.6) 3,290,000 (5.1)
Gadsden Co. Golf 175,802(0.3) 276,428 (0.4) 175,802 (0.3) 276,428 (0.4)
Manley Farms 109,000 (0.2) 326,000 (0.5) 109,000 (0.2) 326000 (0.5)
Total: 1,584,802 (2.5) 2,302428 (3.5) 1.953802 (3.1) 3,892,428 (6.0)










Groundwater


Groundwater in the study area exists in two main producing zones. The principal groundwater
source is the Floridan Aquifer formed by the lower carbonate and dolomitic limestones of the Hawthorn
Formation and the Tampa, Suwannee and Ocala formations. Low transmissivity values are characteristic
of the Floridan Aquifer in Gadsden County and is the main reason for the large spatial variation of the
resource throughout the area. Currently, the City owns three wells used to supplement the surface water
from Quincy Creek for the City's consumption. Well No. 2 penetrates the Floridan Aquifer to a depth of
1,198 feet below mean sea level (msl) and is cased to a depth of -184 feet msl. This well is pumped at
325 gallons per minute. The quality of the water from this well deteriorates rapidly with depth. Chloride
and dissolved solids concentrations below the -450 feet msl elevation range from 3,200 to 13,000. This
well is open to the aquifer for a distance of over 1,000 vertical feet, allowing highly mineralized waters
below -450 feet msl to be drawn upwards and contaminate the fresh water zone. Well No. 3 is currently
being tested as a possible replacement for well No. 2. Well No. 4, located 1.5 miles south of well No. 2,
has a bottom elevation of -435 feet msl and is cased to a depth -188 msl. This well is open to 247 feet of
the aquifer and does not penetrate the base of freshwater and is pumped at 350 gallons per minute. The
quality of the water from this well has been adequate and has not deteriorated with time. Increased
pumping from this or new wells in the vicinity may result in upcoming of highly mineralized water and, as a
consequence, contamination of the fresh water.


Land Use

Land use within the City limits has a wide variety of categories as expected in a sizable urban
area. The study area including the area within city limits and the Quincy Creek basin covers
approximately 28 square miles (18,082 acres). The area within City limits is about 6.2 square miles
(3,972 acres). The tributary area of Quincy Creek at the sewage plant is 23.25 square miles (14,880
acres). The land use information available for this study was provided by the Gadsden County and City
of Quincy planning departments. The information was processed, analyzed and entered into a
Geographic Information System (GIS) at the Northwest Florida Water Management District. Thirteen
major land use classifications were established by aggregating similar land uses into individual
categories. For the purpose of this study, the level of development which affects stormwater runoff was
directly related to impervious area. This is an important relationship to establish because accurate
projections of impervious areas are essential for planning future land use types and stormwater effects
associated with land use.










Groundwater


Groundwater in the study area exists in two main producing zones. The principal groundwater
source is the Floridan Aquifer formed by the lower carbonate and dolomitic limestones of the Hawthorn
Formation and the Tampa, Suwannee and Ocala formations. Low transmissivity values are characteristic
of the Floridan Aquifer in Gadsden County and is the main reason for the large spatial variation of the
resource throughout the area. Currently, the City owns three wells used to supplement the surface water
from Quincy Creek for the City's consumption. Well No. 2 penetrates the Floridan Aquifer to a depth of
1,198 feet below mean sea level (msl) and is cased to a depth of -184 feet msl. This well is pumped at
325 gallons per minute. The quality of the water from this well deteriorates rapidly with depth. Chloride
and dissolved solids concentrations below the -450 feet msl elevation range from 3,200 to 13,000. This
well is open to the aquifer for a distance of over 1,000 vertical feet, allowing highly mineralized waters
below -450 feet msl to be drawn upwards and contaminate the fresh water zone. Well No. 3 is currently
being tested as a possible replacement for well No. 2. Well No. 4, located 1.5 miles south of well No. 2,
has a bottom elevation of -435 feet msl and is cased to a depth -188 msl. This well is open to 247 feet of
the aquifer and does not penetrate the base of freshwater and is pumped at 350 gallons per minute. The
quality of the water from this well has been adequate and has not deteriorated with time. Increased
pumping from this or new wells in the vicinity may result in upcoming of highly mineralized water and, as a
consequence, contamination of the fresh water.


Land Use

Land use within the City limits has a wide variety of categories as expected in a sizable urban
area. The study area including the area within city limits and the Quincy Creek basin covers
approximately 28 square miles (18,082 acres). The area within City limits is about 6.2 square miles
(3,972 acres). The tributary area of Quincy Creek at the sewage plant is 23.25 square miles (14,880
acres). The land use information available for this study was provided by the Gadsden County and City
of Quincy planning departments. The information was processed, analyzed and entered into a
Geographic Information System (GIS) at the Northwest Florida Water Management District. Thirteen
major land use classifications were established by aggregating similar land uses into individual
categories. For the purpose of this study, the level of development which affects stormwater runoff was
directly related to impervious area. This is an important relationship to establish because accurate
projections of impervious areas are essential for planning future land use types and stormwater effects
associated with land use.









Existing Stormwater Drainage System


Generally speaking, a stormwater conveyance system for any basin is a complex network of
channels (natural and man-made), conduits, inlets, bridges and in-line storage that carries the stormwater
runoff from the uplands to the basin's outlet. Most of these drainage elements in the network are
interconnected in a tree-like fashion with the main channel having the largest capacity as it progresses
downstream. There are three main drainage channels that carry stormwater out of the study area. The
first and most significant of them, in terms of magnitude of flows, is Quincy Creek to the north of the City.
Tanyard Branch is the second largest channel which drains the downtown and southern portions of the
City. Cox Creek is the third channel which drains a small portion of the study area in the southeast
corner of the City southward. Each of these major watersheds was subdivided into subbasins so that a
more detailed runoff analysis could be performed in each of the major watersheds. Figure 2 shows the
subbasin delineation in the study area.

The stormwater drainage system in the City of Quincy consists mainly of a complex sewer
system which has been gradually upgraded over the years in an attempt to provide drainage to newly
developed areas in the City. The sewer system works exclusively under gravity since no lift stations exist
within the system. The sewer system is composed mostly of concrete and reinforced concrete pipes,
with some polyvinyl chloride (PVC) and vitrified clay (VC) conduits. Generally speaking, the
interconnection of conduits occurs at concrete and brick manholes and junction boxes. Stormwater
running off the streets is collected into the sewer by concrete catch basins covered by steel grates. Little
or no in-line or off-line storage exists within City limits. In some instances, in-line storage is created at the
upstream face of culverts under certain flow conditions due to high hydraulic head losses produced by the
bridge or culvert. This particular situation occurs upstream of the culvert that crosses the railroad tracks
near the intersection of Twelfth and King streets. Undeveloped areas outside the City limits are usually
naturally drained by swales, open channels, streets, highways, culverts and bridges. Several ponds,
including Interlocking Lakes and other mining pits, provide in-line and off-line storage to these areas.

Summarizing, the drainage system in the study area is a complex group of interconnected pipes,
channels, culverts and in-line storage ponds. In this study, the behavior of the system under different
hydrologic conditions was studied with a computer model. Because it was necessary to simplify the
system, only the most significant drainage components were incorporated into the model under the
assumption that most pipes, channels, or ponds of small size could be ignored with no effect on the
accuracy in the model's results. The following section presents a description of the main drainage
components of each of these three stormwater drainage areas.


Quincy Creek Watershed at State Road 267

The total contributing area of Quincy Creek above the U.S. Geological Survey flow gauge at S.R.
267 is 20.7 square miles (13,267 acres) of mostly forest, agricultural and mining land. Quincy Creek's
headwaters are located to the east of the City of Gretna, Florida, about 5 miles northwest of Quincy.
Ground slopes average 0.026 ft/ft indicative of steep uplands. Rainfall, which does not evaporate or
infiltrate down to become groundwater, runs off as overland flow conveyed downhill by small natural
channels. There are several small ponds originated by mining operations located between the uplands
and the main channel which capture some of the overland flow and later discharging it at a lower rate.

The Upper Quincy Creek above State Road 268 is about 3,020 acres in size of undeveloped
forest land. The main channel of the Upper Quincy Creek is about 3.6 miles from Highway 268 to the
creek's headwaters area near Gretna. The slope of the channel averages 0.005 ft/ft over its length.
Generally speaking, the elevation of the bottom of the channel (about 147 at Highway 268) lies below the
bottom of the upper confining unit, fully penetrating the surficial aquifer and partially penetrating the upper
confining unit. Baseflow in this section of Quincy Creek was recently monitored as a part of this study.
Flow records for the period of record 3/92 to 9/93 indicate a low flow value of 1.57 cubic feet per second.









Existing Stormwater Drainage System


Generally speaking, a stormwater conveyance system for any basin is a complex network of
channels (natural and man-made), conduits, inlets, bridges and in-line storage that carries the stormwater
runoff from the uplands to the basin's outlet. Most of these drainage elements in the network are
interconnected in a tree-like fashion with the main channel having the largest capacity as it progresses
downstream. There are three main drainage channels that carry stormwater out of the study area. The
first and most significant of them, in terms of magnitude of flows, is Quincy Creek to the north of the City.
Tanyard Branch is the second largest channel which drains the downtown and southern portions of the
City. Cox Creek is the third channel which drains a small portion of the study area in the southeast
corner of the City southward. Each of these major watersheds was subdivided into subbasins so that a
more detailed runoff analysis could be performed in each of the major watersheds. Figure 2 shows the
subbasin delineation in the study area.

The stormwater drainage system in the City of Quincy consists mainly of a complex sewer
system which has been gradually upgraded over the years in an attempt to provide drainage to newly
developed areas in the City. The sewer system works exclusively under gravity since no lift stations exist
within the system. The sewer system is composed mostly of concrete and reinforced concrete pipes,
with some polyvinyl chloride (PVC) and vitrified clay (VC) conduits. Generally speaking, the
interconnection of conduits occurs at concrete and brick manholes and junction boxes. Stormwater
running off the streets is collected into the sewer by concrete catch basins covered by steel grates. Little
or no in-line or off-line storage exists within City limits. In some instances, in-line storage is created at the
upstream face of culverts under certain flow conditions due to high hydraulic head losses produced by the
bridge or culvert. This particular situation occurs upstream of the culvert that crosses the railroad tracks
near the intersection of Twelfth and King streets. Undeveloped areas outside the City limits are usually
naturally drained by swales, open channels, streets, highways, culverts and bridges. Several ponds,
including Interlocking Lakes and other mining pits, provide in-line and off-line storage to these areas.

Summarizing, the drainage system in the study area is a complex group of interconnected pipes,
channels, culverts and in-line storage ponds. In this study, the behavior of the system under different
hydrologic conditions was studied with a computer model. Because it was necessary to simplify the
system, only the most significant drainage components were incorporated into the model under the
assumption that most pipes, channels, or ponds of small size could be ignored with no effect on the
accuracy in the model's results. The following section presents a description of the main drainage
components of each of these three stormwater drainage areas.


Quincy Creek Watershed at State Road 267

The total contributing area of Quincy Creek above the U.S. Geological Survey flow gauge at S.R.
267 is 20.7 square miles (13,267 acres) of mostly forest, agricultural and mining land. Quincy Creek's
headwaters are located to the east of the City of Gretna, Florida, about 5 miles northwest of Quincy.
Ground slopes average 0.026 ft/ft indicative of steep uplands. Rainfall, which does not evaporate or
infiltrate down to become groundwater, runs off as overland flow conveyed downhill by small natural
channels. There are several small ponds originated by mining operations located between the uplands
and the main channel which capture some of the overland flow and later discharging it at a lower rate.

The Upper Quincy Creek above State Road 268 is about 3,020 acres in size of undeveloped
forest land. The main channel of the Upper Quincy Creek is about 3.6 miles from Highway 268 to the
creek's headwaters area near Gretna. The slope of the channel averages 0.005 ft/ft over its length.
Generally speaking, the elevation of the bottom of the channel (about 147 at Highway 268) lies below the
bottom of the upper confining unit, fully penetrating the surficial aquifer and partially penetrating the upper
confining unit. Baseflow in this section of Quincy Creek was recently monitored as a part of this study.
Flow records for the period of record 3/92 to 9/93 indicate a low flow value of 1.57 cubic feet per second.









The magnitude of base flow at this location is relatively low if compared to the average base flow values
downstream at the U.S.G.S. gauge at Highway 267. A possible explanation for this is the local soil
composition in the area where clays are abundant restricting downward and lateral flow movement within
the soil. The geometric characteristics of the channel vary rapidly from headwaters to Highway 268 but in
general, the channel is 15-25 feet wide with an average slope of 0.0015. The culvert at Highway 268 is a
triple 8'x6' reinforced concrete box with a length of 28 feet. For this study, continuous flow stage and
rainfall recorders were placed on the left bank just upstream of the culvert.

Subbasin 3 (Figure 2) is the largest runoff contributing subbasin for this creek with 3,019 acres.
Subbasin 5, adjacent to Highway 268, has numerous mining pits providing storage to overland flows
before they reach Quincy Creek. Subbasins 4 and 6 drain portions of urban area in the northwest corner
of the City. Of these two, subbasin 6 drains a larger urban area of about 100 acres of land located
between U.S. Highway 90 and King Street. Runoff is collected and drained in two natural ditches running
parallel to each other south to north until they reach King Street. There, runoff is conveyed under King
Street in a 30-inch circular culvert and, to the east, the second ditch discharges under King Street
through two 18-inch circular pipes into a heavily vegetated wetland joining the streamflow at Quincy
Creek east of Highway 268.

North of the City, Interlocking Lakes detain stormwater runoff from a contributing area of 6,943
acres of agricultural, silvicultural and mining lands. The dam for this impoundment is an earth fill dam
constructed from past mining operations. Because attapulgite clay was mined at this location, the spoil
seems to be a good construction material of low permeability. In September of 1988, the principal
spillway system of the dam failed due to settlement and erosion beneath the pipes. In 1990, the City of
Quincy rehabilitated the dam with a new spillway and emergency spillway systems. The present dam is
200 feet long and 15 feet high with an 18-foot crest width and 12-foot depth. The primary spillway system
consists of two 48-inch re-enforced concrete pipes with a concrete 10' x 3' rectangular box inlet for the
riser covered with a steel grate. The outlet of the twin barrels discharges onto a concrete energy
dissipator of concrete baffles. The emergency spillway system consists of a 60-foot wide grassed
spillway and a concrete ogee type spillway at the end of an excavated channel about 200 feet long.
Limited topographic information about the size of these lakes is available, particularly below the normal
water level of 157 feet (NGVD).

An elevation-area-volume relationship of the lakes was constructed from contour maps and other
existing data about the dam and lakes. It was determined that at normal pool elevation (157.0 feet,
NGVD) the impoundment's capacity is about 550 acre-feet with a surface area of 91 acres. Water from
the spillway system discharges into Colson Creek which runs in a southeasterly direction until it reaches
Quincy Creek about a mile downstream of the dam. Below the dam, cross sectional data of Colson
Creek indicates a channel with a bottom width of about 20 feet with steep bank slopes. The creek's
average slope was estimated a 0.0073 ft/ft. This portion of Colson Creek drains the mostly undeveloped
subbasin 8. Flow records collected during this study indicate a flow range in the creek between 9.95 and
282.0 cubic feet per second.

Runoff from subbasin 7, mostly from the Hillcrest Cemetery in the northern portion of the City,
discharges directly into Quincy Creek through natural ridges and channels. Just downstream of the outlet
of subbasin 7, Colson Creek joins Quincy Creek. Subbasin 10, a mostly undeveloped area with some
low density residential development, also discharges directly into Quincy Creek by natural ridges and
channels. The east boundary of this subbasin is Highway 267 which serves as the outlet of Quincy
Creek at the bridge 400 feet downstream of the water treatment plant intake.










Tanvard Branch at Highway 268


This watershed consists of about 600 acres of downtown Quincy. Values of percent
imperviousness for subbasins 11, 12, 13 and 15 in the watershed area, range from 43.0 to 65.8 percent
making this area highly sensitive to rainfall input. Of all four, subbasin 11 is the most developed and it is
drained almost completely by stormwater sewers. It is also in this subbasin where most of the present
drainage problems exist due to inadequate conveyance in the sewer system. In the upper portion of this
subbasin, a portion of a 30.2 acres area adjacent to the railroad tracks is subject to flooding during severe
storms. Stormwater from the upper portion of the subbasin, including portions of Hillcrest Cemetery,
drains down along 13th Avenue and Rosewood Street until runoff reaches the railroad tracks. Then, this
runoff runs along the tracks towards the subbasin outlet, a 24-inch metal pipe with a metal screen at the
entrance. It is evident, from field observations, that significant head loses can be expected through this
inlet due to the amount of debris which rapidly accumulates at the entrance grate. After the railroad
culvert, the sewer's size is reduced to a 1-foot diameter for a length of 383 feet. Runoff from an
additional area of 5.2 acres enters this segment of sewer between the railroad tracks and King Street. It
is in this segment where sewer lines change size from 12 inches to 18 inches to 15 inches in a distance
of 900 feet. Runoff along King Street, from 14th to 10th streets, joins the main sewer carried by a 15-inch
pipe draining an area of approximately 15 acres of mostly residential area. At this point, the main sewer
changes to a 24-inch pipe for 84 feet and then to 27 inches for 538 feet. Stormwater from an additional
9.2 acres along Franklin Street is collected in this portion of sewer in 15-inch and 18-inch pipes from the
west. From the east, runoff from additional 22.3 acres are drained to this location in 18-inch and 24-inch
pipes. The total contributing area at the manhole between Franklin and Washington streets is about 94
acres of high to medium residential and commercial areas. This confluence of three sewer branches has
been identified in the flood hazard boundary map as a potential area of localized street flooding. The exit
pipe from this manhole increases to 30 inches in diameter and runs under 9th Street for a length of 324
feet at which point it changes into 36-inch pipe until it connects to the culvert under U.S. 90. An
additional 80 acres of mostly commercial land along Franklin and U.S. 90 are drained into the main
sewer. The culvert at U.S. 90 represents the outlet of this sewer line, discharging into Tanyard Branch.
This culvert is made of reinforced concrete with dimensions of 6.2'x5' and a length of approximately 100
feet.

Running in a southeasterly direction, Tanyard Branch crosses Crawford Street, Key Street and
Stewart Street before it reaches Highway 268, also known as Adams Street. The culvert at Crawford
Street consists of a basket-handle shape concrete culvert of 6.8 width and 4.82 height with skewed wing
walls and a length of 41 feet. At Key Street, the culvert consists of a 13'x5' arch-shaped corrugated
metal pipe with wing walls at both ends. A modified arch pipe made of corrugated metal runs under
Stewart Street for a length of 37 feet. The dimensions of this culvert are 11' x 7.5'. About 1,800 feet
downstream from Stewart Street, the culvert under Adams Street, a concrete box 15.8' x 8.7' with wing
walls, serves as the end outlet for portion of the study area. Stormwater runoff from an area of 394 acres
discharge into the open channel portion of Tanyard Branch between U.S. 90 and Adams Street. Of this
acreage, 51 acres north of U.S. 90, are collected by the Monroe Street sewer line which runs from King
Street to a free fall outlet just south of Clark Street. The 15-inch and 18-inch sewers between King Street
and Washington Street seem to be inadequate to convey runoff from severe storms with return periods
greater than 2 years, leading to frequent localized flooding at the intersection of King Street and Monroe
Street. At U.S. 90 and Monroe, runoff is diverted into a 21-inch sewer line which runs parallel to the main
sewer along Monroe Street and collected further downstream at Crawford Street where the main sewer
consists of a 30" and a 36" pipe. About 430 feet south, below Clark Street, the main sewers discharge
into a steep wooded area which leads to Tanyard Branch west of Adams Street.










Experiment Station Road Watershed


This 347-acre parcel of land is located in the southwest corner of the City and is identified as
subbasin 26 in Figure 2. This subbasin extends from U.S. 90 in the north to a 12-acre pond .4 miles
south of Experiment Station Road, and from Atlanta Street in the west to Cleveland Street to the east.
The northwest quadrant of the watershed with an area of 63 acres is mainly industrial and includes
Quincy's Industrial Park whereas the northeast quadrant is mostly residential and covers an area of about
63 acres. Stormwater runoff from the Industrial Park is collected and drained along Shelfer Street by a
30" and 36" single sewer line until it discharges in an open channel at the south side of Experiment
Station Road. Runoff from the northeast quadrant is drained in 18" and 24" pipes along Camilia Avenue,
Lucky Street, Caldwell Street and Inlet Street, where the sewer discharges into an open area drained by
an open ditch. This channel runs 400 feet until it reaches a double 36" pipe at Experiment Station Road
half filled with sediments. Downstream from this culvert, the channel, about 20 feet wide, discharges into
a single 30" pipe under Shelfer Street and is connected to a basket handle-shape 3' x 2' concrete culvert
which discharges into an open channel south of Flager Street. This 266-foot long reach of channel is
heavily vegetated and has a flat slope of .0004 ft/ft. Runoff from a low density residential area south of
Experiment Station Road, joins the flows from the upper portion of the watershed making the total
contributing area of 160 acres at Hamilton Street. Reported flooding problems during severe storms
occur within this area and can be associated to low conveyance capacity in the lower part of the basin,
between Experiment Station Road and Hamilton Street. The runoff from an additional 187 acres of
mostly agricultural and vacant land is collected along the channel between Hamilton Street and a grassy
pond considered to be the outlet of subbasin 26. Water released from the pond runs in a southerly
direction in an open channel called Cox Creek. This creek eventually discharges into Rocky Comfort
Creek about 4 miles south of City limits.










Existing Stormwater Related Problems


The focus in this study is on the most pressing stormwater related problems. These problems
can be classified under two categories: flooding and water quality problems. At the beginning of this
study, the problems were identified by District personnel, City officials and, in some instances, the
general public. The flooding problems identified are listed in Table 2 and their location is shown in Figure
3. Following is a short narrative description of each of the stormwater related problems.


Flooding Problems


Shelfer St. and Experiment Station Road

During the storm of Mach 3, 1991, as much as 15 inches of rain was reported in the area. At
Quincy, 9.96 inches of rain were recorded in a 24-hour period. This particular storm, with a return period
between 10 and 25 years, caused some flooding damages in Quincy and surrounding areas. The
southwest corner portion of the City experienced flooding along Shelfer Road from the Industrial Park to
Hamilton Road, south of Experiment Station Road. No particular flow, water level stage data is available
for this storm anywhere in the area. High water marks on the affected structures or landmarks, provide
the only information related to flooding for this event. Since no frequent flooding has been reported in the
area, this portion of the City can expect to be affected by flooding during very severe storm events of
return period larger than 10 years.

Virginia Street Drainage Ditch

In the southwest corner of the City is a small section of storm sewer that drains water from
Flager, Hamilton, and Virginia streets. Once collected, this water is piped down the east side of Virginia
Street and discharged into an existing open channel which terminates on the southern side of town in a
low area and eventually into Cox Creek. The problem with this conveyance is that the open channel is
silted up several yards down stream from the point where the storm sewer discharges and this causes
the discharged water to pond and run back onto Virginia Street. Recent development could be the cause
for the accelerated siltation in the channel. Currently the City does not have legal access to the channel
to perform maintenance work in the channel. This flooding problem is likely to continue until legal access
for dredging and maintenance in the channel can be arranged between the City and the property owner
and a periodic maintenance program established

Main Street and Washington Street

Frequent street flooding at the intersection of Main Street and Washington Street has been
identified by City officials. A multiple sewer connection loop at this intersection receives stormwater
runoff from an area of about 31 acres of highly impervious area and moderate slopes. The main sewer
line which runs south to north along 13th Street and the Athletic Field consists of a 21" pipe. The outlet
manhole at Washington Street receives runoff from the main 18" pipe and an additional 12" pipe.
Additional head losses can be expected at this intersection due to increase in pipe diameters and change
in directions at the junctions. The City has already studied this problem area and has proposed the
replacement of the 18" sewer by a 30" pipe from Washington Street to Franklin Street, a 42" pipe from
Franklin Street to the intersection of Graves Street and King Street, and 48" pipe from King Street to the
outfall west of the municipal swimming pool.










Existing Stormwater Related Problems


The focus in this study is on the most pressing stormwater related problems. These problems
can be classified under two categories: flooding and water quality problems. At the beginning of this
study, the problems were identified by District personnel, City officials and, in some instances, the
general public. The flooding problems identified are listed in Table 2 and their location is shown in Figure
3. Following is a short narrative description of each of the stormwater related problems.


Flooding Problems


Shelfer St. and Experiment Station Road

During the storm of Mach 3, 1991, as much as 15 inches of rain was reported in the area. At
Quincy, 9.96 inches of rain were recorded in a 24-hour period. This particular storm, with a return period
between 10 and 25 years, caused some flooding damages in Quincy and surrounding areas. The
southwest corner portion of the City experienced flooding along Shelfer Road from the Industrial Park to
Hamilton Road, south of Experiment Station Road. No particular flow, water level stage data is available
for this storm anywhere in the area. High water marks on the affected structures or landmarks, provide
the only information related to flooding for this event. Since no frequent flooding has been reported in the
area, this portion of the City can expect to be affected by flooding during very severe storm events of
return period larger than 10 years.

Virginia Street Drainage Ditch

In the southwest corner of the City is a small section of storm sewer that drains water from
Flager, Hamilton, and Virginia streets. Once collected, this water is piped down the east side of Virginia
Street and discharged into an existing open channel which terminates on the southern side of town in a
low area and eventually into Cox Creek. The problem with this conveyance is that the open channel is
silted up several yards down stream from the point where the storm sewer discharges and this causes
the discharged water to pond and run back onto Virginia Street. Recent development could be the cause
for the accelerated siltation in the channel. Currently the City does not have legal access to the channel
to perform maintenance work in the channel. This flooding problem is likely to continue until legal access
for dredging and maintenance in the channel can be arranged between the City and the property owner
and a periodic maintenance program established

Main Street and Washington Street

Frequent street flooding at the intersection of Main Street and Washington Street has been
identified by City officials. A multiple sewer connection loop at this intersection receives stormwater
runoff from an area of about 31 acres of highly impervious area and moderate slopes. The main sewer
line which runs south to north along 13th Street and the Athletic Field consists of a 21" pipe. The outlet
manhole at Washington Street receives runoff from the main 18" pipe and an additional 12" pipe.
Additional head losses can be expected at this intersection due to increase in pipe diameters and change
in directions at the junctions. The City has already studied this problem area and has proposed the
replacement of the 18" sewer by a 30" pipe from Washington Street to Franklin Street, a 42" pipe from
Franklin Street to the intersection of Graves Street and King Street, and 48" pipe from King Street to the
outfall west of the municipal swimming pool.










Existing Stormwater Related Problems


The focus in this study is on the most pressing stormwater related problems. These problems
can be classified under two categories: flooding and water quality problems. At the beginning of this
study, the problems were identified by District personnel, City officials and, in some instances, the
general public. The flooding problems identified are listed in Table 2 and their location is shown in Figure
3. Following is a short narrative description of each of the stormwater related problems.


Flooding Problems


Shelfer St. and Experiment Station Road

During the storm of Mach 3, 1991, as much as 15 inches of rain was reported in the area. At
Quincy, 9.96 inches of rain were recorded in a 24-hour period. This particular storm, with a return period
between 10 and 25 years, caused some flooding damages in Quincy and surrounding areas. The
southwest corner portion of the City experienced flooding along Shelfer Road from the Industrial Park to
Hamilton Road, south of Experiment Station Road. No particular flow, water level stage data is available
for this storm anywhere in the area. High water marks on the affected structures or landmarks, provide
the only information related to flooding for this event. Since no frequent flooding has been reported in the
area, this portion of the City can expect to be affected by flooding during very severe storm events of
return period larger than 10 years.

Virginia Street Drainage Ditch

In the southwest corner of the City is a small section of storm sewer that drains water from
Flager, Hamilton, and Virginia streets. Once collected, this water is piped down the east side of Virginia
Street and discharged into an existing open channel which terminates on the southern side of town in a
low area and eventually into Cox Creek. The problem with this conveyance is that the open channel is
silted up several yards down stream from the point where the storm sewer discharges and this causes
the discharged water to pond and run back onto Virginia Street. Recent development could be the cause
for the accelerated siltation in the channel. Currently the City does not have legal access to the channel
to perform maintenance work in the channel. This flooding problem is likely to continue until legal access
for dredging and maintenance in the channel can be arranged between the City and the property owner
and a periodic maintenance program established

Main Street and Washington Street

Frequent street flooding at the intersection of Main Street and Washington Street has been
identified by City officials. A multiple sewer connection loop at this intersection receives stormwater
runoff from an area of about 31 acres of highly impervious area and moderate slopes. The main sewer
line which runs south to north along 13th Street and the Athletic Field consists of a 21" pipe. The outlet
manhole at Washington Street receives runoff from the main 18" pipe and an additional 12" pipe.
Additional head losses can be expected at this intersection due to increase in pipe diameters and change
in directions at the junctions. The City has already studied this problem area and has proposed the
replacement of the 18" sewer by a 30" pipe from Washington Street to Franklin Street, a 42" pipe from
Franklin Street to the intersection of Graves Street and King Street, and 48" pipe from King Street to the
outfall west of the municipal swimming pool.










Existing Stormwater Related Problems


The focus in this study is on the most pressing stormwater related problems. These problems
can be classified under two categories: flooding and water quality problems. At the beginning of this
study, the problems were identified by District personnel, City officials and, in some instances, the
general public. The flooding problems identified are listed in Table 2 and their location is shown in Figure
3. Following is a short narrative description of each of the stormwater related problems.


Flooding Problems


Shelfer St. and Experiment Station Road

During the storm of Mach 3, 1991, as much as 15 inches of rain was reported in the area. At
Quincy, 9.96 inches of rain were recorded in a 24-hour period. This particular storm, with a return period
between 10 and 25 years, caused some flooding damages in Quincy and surrounding areas. The
southwest corner portion of the City experienced flooding along Shelfer Road from the Industrial Park to
Hamilton Road, south of Experiment Station Road. No particular flow, water level stage data is available
for this storm anywhere in the area. High water marks on the affected structures or landmarks, provide
the only information related to flooding for this event. Since no frequent flooding has been reported in the
area, this portion of the City can expect to be affected by flooding during very severe storm events of
return period larger than 10 years.

Virginia Street Drainage Ditch

In the southwest corner of the City is a small section of storm sewer that drains water from
Flager, Hamilton, and Virginia streets. Once collected, this water is piped down the east side of Virginia
Street and discharged into an existing open channel which terminates on the southern side of town in a
low area and eventually into Cox Creek. The problem with this conveyance is that the open channel is
silted up several yards down stream from the point where the storm sewer discharges and this causes
the discharged water to pond and run back onto Virginia Street. Recent development could be the cause
for the accelerated siltation in the channel. Currently the City does not have legal access to the channel
to perform maintenance work in the channel. This flooding problem is likely to continue until legal access
for dredging and maintenance in the channel can be arranged between the City and the property owner
and a periodic maintenance program established

Main Street and Washington Street

Frequent street flooding at the intersection of Main Street and Washington Street has been
identified by City officials. A multiple sewer connection loop at this intersection receives stormwater
runoff from an area of about 31 acres of highly impervious area and moderate slopes. The main sewer
line which runs south to north along 13th Street and the Athletic Field consists of a 21" pipe. The outlet
manhole at Washington Street receives runoff from the main 18" pipe and an additional 12" pipe.
Additional head losses can be expected at this intersection due to increase in pipe diameters and change
in directions at the junctions. The City has already studied this problem area and has proposed the
replacement of the 18" sewer by a 30" pipe from Washington Street to Franklin Street, a 42" pipe from
Franklin Street to the intersection of Graves Street and King Street, and 48" pipe from King Street to the
outfall west of the municipal swimming pool.










Existing Stormwater Related Problems


The focus in this study is on the most pressing stormwater related problems. These problems
can be classified under two categories: flooding and water quality problems. At the beginning of this
study, the problems were identified by District personnel, City officials and, in some instances, the
general public. The flooding problems identified are listed in Table 2 and their location is shown in Figure
3. Following is a short narrative description of each of the stormwater related problems.


Flooding Problems


Shelfer St. and Experiment Station Road

During the storm of Mach 3, 1991, as much as 15 inches of rain was reported in the area. At
Quincy, 9.96 inches of rain were recorded in a 24-hour period. This particular storm, with a return period
between 10 and 25 years, caused some flooding damages in Quincy and surrounding areas. The
southwest corner portion of the City experienced flooding along Shelfer Road from the Industrial Park to
Hamilton Road, south of Experiment Station Road. No particular flow, water level stage data is available
for this storm anywhere in the area. High water marks on the affected structures or landmarks, provide
the only information related to flooding for this event. Since no frequent flooding has been reported in the
area, this portion of the City can expect to be affected by flooding during very severe storm events of
return period larger than 10 years.

Virginia Street Drainage Ditch

In the southwest corner of the City is a small section of storm sewer that drains water from
Flager, Hamilton, and Virginia streets. Once collected, this water is piped down the east side of Virginia
Street and discharged into an existing open channel which terminates on the southern side of town in a
low area and eventually into Cox Creek. The problem with this conveyance is that the open channel is
silted up several yards down stream from the point where the storm sewer discharges and this causes
the discharged water to pond and run back onto Virginia Street. Recent development could be the cause
for the accelerated siltation in the channel. Currently the City does not have legal access to the channel
to perform maintenance work in the channel. This flooding problem is likely to continue until legal access
for dredging and maintenance in the channel can be arranged between the City and the property owner
and a periodic maintenance program established

Main Street and Washington Street

Frequent street flooding at the intersection of Main Street and Washington Street has been
identified by City officials. A multiple sewer connection loop at this intersection receives stormwater
runoff from an area of about 31 acres of highly impervious area and moderate slopes. The main sewer
line which runs south to north along 13th Street and the Athletic Field consists of a 21" pipe. The outlet
manhole at Washington Street receives runoff from the main 18" pipe and an additional 12" pipe.
Additional head losses can be expected at this intersection due to increase in pipe diameters and change
in directions at the junctions. The City has already studied this problem area and has proposed the
replacement of the 18" sewer by a 30" pipe from Washington Street to Franklin Street, a 42" pipe from
Franklin Street to the intersection of Graves Street and King Street, and 48" pipe from King Street to the
outfall west of the municipal swimming pool.
















TABLE 2
Identified Flooding Problems Within City Limits and Proposed Recommendations


Problem
Area No. Location Problem Description Recommended Alternative
Flooding along main drain channel from Experiment Station Regrade existing channel, ocean up existing culverts and
1 Shelfer St. and Experiment Station Rd. Road to Hamilton Street. Structural damage to homes and perform regular maintenance in drainage system. Keep further
buildings in flood plain. development off flood plain.
Localized street flooding at intersection disrupting traffic and Pipe enlargement on King Street West Branch from Main Street
2 Main Street and Washington Street causing hazardous driving conditions. and Washington Street to sewer outlet (see Table 3 for cost).

Localized flooding at the upstream side of railroad tracks. Purchase of affected land and structures. Prevent further
3 12th Street and SAL Mine Spur Rail Structural damage to homes in low lying areas. development in flood plain.
Road
Potential riverine flooding for large storm events. Backwater None
4 Quincy Creek at State Road 267 conditions upstream of bridge may affect water treatment plant
intake.
Localized street flooding at intersection disrupting traffic and Pipe enlargement along Monroe Street from King Street to
5 King Street and Monroe Street causing hazardous driving conditions. Washington Street (see Table 3 for cost).

Localized flooding along creek with high velocity flows. Potential Maintain channel dean of debris and prevent further
6 Tanyard Branch at Adams Street bank erosion. development on flood plain.

Localized flooding. Water may overtop road during sever storm Maintain channel clean of debris and prevent further
7 Tanyard Branch at Stewart Street events, development on flood plain.

Localized flooding. Water may overtop road during severe Maintain channel clean of debris and prevent further
8 Tanyard Branch at Key Street storm events, development on flood plain.

Localized flooding due to constricted culvert outlet. Water may Remove sediment plug in channel downstream of Virginia
9 Virginia Street Drainage Ditch overtop road during severe storm events. Avenue. Maintain drainage channel dean.
____________I _________________________________________






9


S---- Ci

t-0l. Ri





I~:~ I~ I


ty Limits
all Road
blood Prone


Figure 3. Flood Prone Areas in Study Area
(Source: Federal Insurance Administration, Gadsden County, 1976)


legend


- State Road

U.S. Road
--.- Stream


Branch


Stormwater Problem Areas
1. Shelfer and Experiment Station Rd.
2. Main and Washington Street
3. 12th Street and Rail Road
4. Quincy Creek at Adams Street
5. King and Monroe Street
6. Tanyard Branch at Adams Street
7. Tanyard Branch at Stewart Street
8. Tanyard Branch at Key Street
9. Virginia Avenue Ditch










12th Street and SAL Mine Sour Rail Road


This is one of the most pressing flooding problems in the study area due to its frequency of
occurrence in a residential area where a few houses located just upstream of the tracks flood during
severe storms. As previously discussed in an earlier section of this report, the flooding is caused by an
inadequate sewer line which contracts in size from the culvert at the rail road crossing to King Street
where the pipe becomes a 24" inch again. The inlet of the rail road culvert is protected by a metal screen
that rapidly clogs by debris carried by the stormwater.

The most obvious alternatives to alleviate the problems at this location are the purchase of the
affected land and property by the City and maintain it as preservation land, and the replacement of the
sewer lines from the rail road to Franklin Street with larger diameter pipes. Analyses of these alternatives
are included in the alternative section of this report.

Quincy Creek at State Road 267

The flooding problem along Middle Quincy Creek, from Highway 268 to Highway 12 is related to
riverine flooding associated with high return period storms. The Federal Emergency Management
Agency (FEMA) has developed.flood frequency maps for this section of the creek. These flood
elevations were used in evaluating the potential damages caused along this portion of the creek. Figure
16 shows the 100-year flood plain along Quincy Creek. According to FEMA, the only significant flooding
along this stretch of Quincy Creek occurs at State Road 267 and State Road 65 where the frequency of
road flooding is in the average, once every fifty years. Flooding upstream of State Road 267 may cause
problems for the water treatment plant whose intake structure is located about 200 feet from the bridge.
Structural damage to nearby structures has been minimal during the last two major storm events in
September of 1969 and March of 1991 when water overtopped this bridge.

King Street and Monroe Street

The problem of frequent street flooding at the intersection of King Street and Monroe Street is
due to the lack of conveyance capacity in the sewer system. This problem is also aggravated by a
ground depression at this location. The inadequacy of the sewer system is due to a large area, about 30
acres of highly impervious land, draining into three catchbasins at the Intersection of Monroe Street and
King Street. Furthermore, runoff from Monroe Street flows into these catchbasins from north and south
of Monroe Street and east and west of King Street. Therefore, water accumulates at the intersection
when the inflow rate of stormwater from the street exceeds the sewer conveyance capacity. The City has
studied the problem at this location and the.proposed drainage alternative is further investigated in this
study.

Tanyard Branch at Adams Street. Stewart Street and Key Street

Tanyard Branch is one of the main drainage elements in the City's drainage network. However,
little is known about the flow quantity and quality characteristics of this creek. Most of the downtown
area's stormwater runoff is discharged into this open ditch and carried out of City limits and discharged
into Quincy Creek just downstream of the municipal waste water treatment plant. Reported problems in
this creek include localized flooding and bank erosion during intense storm events. Being the receptor of
the runoff from a large impervious area, the response of this creek is very quick and as a consequence,
difficult to monitor and sample. For this study, flow and water quality recorders were placed in the creek
at the intersection with Adams Street. This monitoring location is particularly useful because it reflects
the effect of runoff and pollutants from the upper part of the watershed only, where most of the street
flooding problems and most of the urbanization occurs. High velocity flows upstream and downstream of
culverts may cause severe bank erosion. Street flooding problems are reportedly minimum and confined
along the stream banks, upstream of the culverts where debris rapidly accumulates. Water quality
problems may be expected in this stream because the nature of the urban land drained by it.










12th Street and SAL Mine Sour Rail Road


This is one of the most pressing flooding problems in the study area due to its frequency of
occurrence in a residential area where a few houses located just upstream of the tracks flood during
severe storms. As previously discussed in an earlier section of this report, the flooding is caused by an
inadequate sewer line which contracts in size from the culvert at the rail road crossing to King Street
where the pipe becomes a 24" inch again. The inlet of the rail road culvert is protected by a metal screen
that rapidly clogs by debris carried by the stormwater.

The most obvious alternatives to alleviate the problems at this location are the purchase of the
affected land and property by the City and maintain it as preservation land, and the replacement of the
sewer lines from the rail road to Franklin Street with larger diameter pipes. Analyses of these alternatives
are included in the alternative section of this report.

Quincy Creek at State Road 267

The flooding problem along Middle Quincy Creek, from Highway 268 to Highway 12 is related to
riverine flooding associated with high return period storms. The Federal Emergency Management
Agency (FEMA) has developed.flood frequency maps for this section of the creek. These flood
elevations were used in evaluating the potential damages caused along this portion of the creek. Figure
16 shows the 100-year flood plain along Quincy Creek. According to FEMA, the only significant flooding
along this stretch of Quincy Creek occurs at State Road 267 and State Road 65 where the frequency of
road flooding is in the average, once every fifty years. Flooding upstream of State Road 267 may cause
problems for the water treatment plant whose intake structure is located about 200 feet from the bridge.
Structural damage to nearby structures has been minimal during the last two major storm events in
September of 1969 and March of 1991 when water overtopped this bridge.

King Street and Monroe Street

The problem of frequent street flooding at the intersection of King Street and Monroe Street is
due to the lack of conveyance capacity in the sewer system. This problem is also aggravated by a
ground depression at this location. The inadequacy of the sewer system is due to a large area, about 30
acres of highly impervious land, draining into three catchbasins at the Intersection of Monroe Street and
King Street. Furthermore, runoff from Monroe Street flows into these catchbasins from north and south
of Monroe Street and east and west of King Street. Therefore, water accumulates at the intersection
when the inflow rate of stormwater from the street exceeds the sewer conveyance capacity. The City has
studied the problem at this location and the.proposed drainage alternative is further investigated in this
study.

Tanyard Branch at Adams Street. Stewart Street and Key Street

Tanyard Branch is one of the main drainage elements in the City's drainage network. However,
little is known about the flow quantity and quality characteristics of this creek. Most of the downtown
area's stormwater runoff is discharged into this open ditch and carried out of City limits and discharged
into Quincy Creek just downstream of the municipal waste water treatment plant. Reported problems in
this creek include localized flooding and bank erosion during intense storm events. Being the receptor of
the runoff from a large impervious area, the response of this creek is very quick and as a consequence,
difficult to monitor and sample. For this study, flow and water quality recorders were placed in the creek
at the intersection with Adams Street. This monitoring location is particularly useful because it reflects
the effect of runoff and pollutants from the upper part of the watershed only, where most of the street
flooding problems and most of the urbanization occurs. High velocity flows upstream and downstream of
culverts may cause severe bank erosion. Street flooding problems are reportedly minimum and confined
along the stream banks, upstream of the culverts where debris rapidly accumulates. Water quality
problems may be expected in this stream because the nature of the urban land drained by it.










12th Street and SAL Mine Sour Rail Road


This is one of the most pressing flooding problems in the study area due to its frequency of
occurrence in a residential area where a few houses located just upstream of the tracks flood during
severe storms. As previously discussed in an earlier section of this report, the flooding is caused by an
inadequate sewer line which contracts in size from the culvert at the rail road crossing to King Street
where the pipe becomes a 24" inch again. The inlet of the rail road culvert is protected by a metal screen
that rapidly clogs by debris carried by the stormwater.

The most obvious alternatives to alleviate the problems at this location are the purchase of the
affected land and property by the City and maintain it as preservation land, and the replacement of the
sewer lines from the rail road to Franklin Street with larger diameter pipes. Analyses of these alternatives
are included in the alternative section of this report.

Quincy Creek at State Road 267

The flooding problem along Middle Quincy Creek, from Highway 268 to Highway 12 is related to
riverine flooding associated with high return period storms. The Federal Emergency Management
Agency (FEMA) has developed.flood frequency maps for this section of the creek. These flood
elevations were used in evaluating the potential damages caused along this portion of the creek. Figure
16 shows the 100-year flood plain along Quincy Creek. According to FEMA, the only significant flooding
along this stretch of Quincy Creek occurs at State Road 267 and State Road 65 where the frequency of
road flooding is in the average, once every fifty years. Flooding upstream of State Road 267 may cause
problems for the water treatment plant whose intake structure is located about 200 feet from the bridge.
Structural damage to nearby structures has been minimal during the last two major storm events in
September of 1969 and March of 1991 when water overtopped this bridge.

King Street and Monroe Street

The problem of frequent street flooding at the intersection of King Street and Monroe Street is
due to the lack of conveyance capacity in the sewer system. This problem is also aggravated by a
ground depression at this location. The inadequacy of the sewer system is due to a large area, about 30
acres of highly impervious land, draining into three catchbasins at the Intersection of Monroe Street and
King Street. Furthermore, runoff from Monroe Street flows into these catchbasins from north and south
of Monroe Street and east and west of King Street. Therefore, water accumulates at the intersection
when the inflow rate of stormwater from the street exceeds the sewer conveyance capacity. The City has
studied the problem at this location and the.proposed drainage alternative is further investigated in this
study.

Tanyard Branch at Adams Street. Stewart Street and Key Street

Tanyard Branch is one of the main drainage elements in the City's drainage network. However,
little is known about the flow quantity and quality characteristics of this creek. Most of the downtown
area's stormwater runoff is discharged into this open ditch and carried out of City limits and discharged
into Quincy Creek just downstream of the municipal waste water treatment plant. Reported problems in
this creek include localized flooding and bank erosion during intense storm events. Being the receptor of
the runoff from a large impervious area, the response of this creek is very quick and as a consequence,
difficult to monitor and sample. For this study, flow and water quality recorders were placed in the creek
at the intersection with Adams Street. This monitoring location is particularly useful because it reflects
the effect of runoff and pollutants from the upper part of the watershed only, where most of the street
flooding problems and most of the urbanization occurs. High velocity flows upstream and downstream of
culverts may cause severe bank erosion. Street flooding problems are reportedly minimum and confined
along the stream banks, upstream of the culverts where debris rapidly accumulates. Water quality
problems may be expected in this stream because the nature of the urban land drained by it.










12th Street and SAL Mine Sour Rail Road


This is one of the most pressing flooding problems in the study area due to its frequency of
occurrence in a residential area where a few houses located just upstream of the tracks flood during
severe storms. As previously discussed in an earlier section of this report, the flooding is caused by an
inadequate sewer line which contracts in size from the culvert at the rail road crossing to King Street
where the pipe becomes a 24" inch again. The inlet of the rail road culvert is protected by a metal screen
that rapidly clogs by debris carried by the stormwater.

The most obvious alternatives to alleviate the problems at this location are the purchase of the
affected land and property by the City and maintain it as preservation land, and the replacement of the
sewer lines from the rail road to Franklin Street with larger diameter pipes. Analyses of these alternatives
are included in the alternative section of this report.

Quincy Creek at State Road 267

The flooding problem along Middle Quincy Creek, from Highway 268 to Highway 12 is related to
riverine flooding associated with high return period storms. The Federal Emergency Management
Agency (FEMA) has developed.flood frequency maps for this section of the creek. These flood
elevations were used in evaluating the potential damages caused along this portion of the creek. Figure
16 shows the 100-year flood plain along Quincy Creek. According to FEMA, the only significant flooding
along this stretch of Quincy Creek occurs at State Road 267 and State Road 65 where the frequency of
road flooding is in the average, once every fifty years. Flooding upstream of State Road 267 may cause
problems for the water treatment plant whose intake structure is located about 200 feet from the bridge.
Structural damage to nearby structures has been minimal during the last two major storm events in
September of 1969 and March of 1991 when water overtopped this bridge.

King Street and Monroe Street

The problem of frequent street flooding at the intersection of King Street and Monroe Street is
due to the lack of conveyance capacity in the sewer system. This problem is also aggravated by a
ground depression at this location. The inadequacy of the sewer system is due to a large area, about 30
acres of highly impervious land, draining into three catchbasins at the Intersection of Monroe Street and
King Street. Furthermore, runoff from Monroe Street flows into these catchbasins from north and south
of Monroe Street and east and west of King Street. Therefore, water accumulates at the intersection
when the inflow rate of stormwater from the street exceeds the sewer conveyance capacity. The City has
studied the problem at this location and the.proposed drainage alternative is further investigated in this
study.

Tanyard Branch at Adams Street. Stewart Street and Key Street

Tanyard Branch is one of the main drainage elements in the City's drainage network. However,
little is known about the flow quantity and quality characteristics of this creek. Most of the downtown
area's stormwater runoff is discharged into this open ditch and carried out of City limits and discharged
into Quincy Creek just downstream of the municipal waste water treatment plant. Reported problems in
this creek include localized flooding and bank erosion during intense storm events. Being the receptor of
the runoff from a large impervious area, the response of this creek is very quick and as a consequence,
difficult to monitor and sample. For this study, flow and water quality recorders were placed in the creek
at the intersection with Adams Street. This monitoring location is particularly useful because it reflects
the effect of runoff and pollutants from the upper part of the watershed only, where most of the street
flooding problems and most of the urbanization occurs. High velocity flows upstream and downstream of
culverts may cause severe bank erosion. Street flooding problems are reportedly minimum and confined
along the stream banks, upstream of the culverts where debris rapidly accumulates. Water quality
problems may be expected in this stream because the nature of the urban land drained by it.









Water Supply Problems


One of the most pressing problems that the City of Quincy currently faces is the adequacy of the
City's water supply. As the demand for a limited resource increases, the problem may worsen due to
natural or man made causes. Under present conditions the sources of water for municipal use are
adequate in quantity and quality most of the time. However, high turbidity levels in Quincy Creek
following significant storm events force the City to shut down its surface water intake for several days.
The City then supplements the supply with groundwater. A more difficult problem may be the
development of a reliable supply to meet future demands, especially during pronounced drought periods.
A number of possible alternatives to approach the City's water supply current and future needs have
been recently issued in a study for the City of Quincy by the consultant CH2M-Hill2. Six possible
alternatives to satisfy present and future demands are the improvement of the water treatment process,
development of new water supply wells, upstream relocation of the intake to draw water from Colson
Creek, management of the Interlocking Lakes to supplement the supply, watershed protection and
construction of a new water treatment plant. This report will examine the surface water aspects of these
alternatives, namely, the long-term low flow analysis of Colson Creek and its potential use as a water
supply.

Since 1948, Quincy Creek has been the City's primary source of water supply. The stream is a
Class I water body according to the State of Florida Water Quality Standards. Due to its hydrogeologic
setting in the middle of Gadsden County, this stream is characterized by low baseflows throughout the
year. Fortunately, extended drought periods are infrequent in the region and base flows can be sustained
for the duration of the droughts. According to flow records from 1974 to 1992, the stream at State Road
267 has never run dry. Drought frequencies are usually analyzed on the basis of long records of low
flows, usually, averaged on a daily basis. During the low flow analysis, the lowest daily flows are scanned
for each year of record. The scan is then applied to several averaging periods, namely, the 1, 3, 7, 30,
60, 90, 183, and 365-day average flows. Statistics such as the mean, standard deviation, and skew
coefficient are then computed for each sequence of averaged daily flows. Finally, these statistics are
fitted to the Log-Pearson Type III distribution to generate the frequency distributions for each set. All
these steps are carried out following the guidelines of the U.S. Water Resources Council. Drought
frequency curves for Quincy Creek at State Road 267 (U.S.G.S. station 02329534) were generated with
this procedure using the daily flow record from 1975 to 1992. The results from the frequency analysis are
available in the City of Quincy Stormwater Management Plan. These curves were used to study drought
recurrecnce in Quincy Creek over a long period of time. With these frequency curves, one can obtain, for
example, the probability that a flow of x magnitude will remain below this value during a period of n
consecutive days in any given year.


Existing Operations

Currently, the City obtains approximately 87 percent of its required annual water supply from
Quincy Creek. Long-term records of daily flows (1974 1992) indicate that the maximum yearly flow is
30.3 MGD (47 cfs), the mean is 18.1 MGD (28 cfs) and the minimum yearly flow is 11.2 MGD (17.3 cfs).
Historically, the City and other upstream users withdraw 1.58 MGD (2.5 cfs) in an average day and a
maximum in one day of 2.3 MGD (3.5 cfs). During the drought of 1985-1986, a record minimum flow of
2.3 cfs was recorded at the U.S.G.S. gauge on May 7, 1985. Records indicate that during May 7 and 8,
the water treatment plant withdrew 1.49 MGD (2.3 cfs). An adjusted value of base flow in the creek
should include all upstream users that withdrew water from the stream during this period. There is no
withdrawal data available about the other two permitted upstream users, Gadsden County Golf with an
average daily demand of 0.19 MGD (0.3 cfs) and Manley Farms with an average daily demand of 0.13
MGD (0.2 cfs). The adjusted value of minimum base flow value for the creek, under the assumption that
there were no other upstream withdrawals during this period, is 3.29 MGD (5.1 cfs). This adjusted value

2 CH2M-Hill, 1990. City of Quincy, Florida Water Resources Study Final Report, January 1990.
19









Water Supply Problems


One of the most pressing problems that the City of Quincy currently faces is the adequacy of the
City's water supply. As the demand for a limited resource increases, the problem may worsen due to
natural or man made causes. Under present conditions the sources of water for municipal use are
adequate in quantity and quality most of the time. However, high turbidity levels in Quincy Creek
following significant storm events force the City to shut down its surface water intake for several days.
The City then supplements the supply with groundwater. A more difficult problem may be the
development of a reliable supply to meet future demands, especially during pronounced drought periods.
A number of possible alternatives to approach the City's water supply current and future needs have
been recently issued in a study for the City of Quincy by the consultant CH2M-Hill2. Six possible
alternatives to satisfy present and future demands are the improvement of the water treatment process,
development of new water supply wells, upstream relocation of the intake to draw water from Colson
Creek, management of the Interlocking Lakes to supplement the supply, watershed protection and
construction of a new water treatment plant. This report will examine the surface water aspects of these
alternatives, namely, the long-term low flow analysis of Colson Creek and its potential use as a water
supply.

Since 1948, Quincy Creek has been the City's primary source of water supply. The stream is a
Class I water body according to the State of Florida Water Quality Standards. Due to its hydrogeologic
setting in the middle of Gadsden County, this stream is characterized by low baseflows throughout the
year. Fortunately, extended drought periods are infrequent in the region and base flows can be sustained
for the duration of the droughts. According to flow records from 1974 to 1992, the stream at State Road
267 has never run dry. Drought frequencies are usually analyzed on the basis of long records of low
flows, usually, averaged on a daily basis. During the low flow analysis, the lowest daily flows are scanned
for each year of record. The scan is then applied to several averaging periods, namely, the 1, 3, 7, 30,
60, 90, 183, and 365-day average flows. Statistics such as the mean, standard deviation, and skew
coefficient are then computed for each sequence of averaged daily flows. Finally, these statistics are
fitted to the Log-Pearson Type III distribution to generate the frequency distributions for each set. All
these steps are carried out following the guidelines of the U.S. Water Resources Council. Drought
frequency curves for Quincy Creek at State Road 267 (U.S.G.S. station 02329534) were generated with
this procedure using the daily flow record from 1975 to 1992. The results from the frequency analysis are
available in the City of Quincy Stormwater Management Plan. These curves were used to study drought
recurrecnce in Quincy Creek over a long period of time. With these frequency curves, one can obtain, for
example, the probability that a flow of x magnitude will remain below this value during a period of n
consecutive days in any given year.


Existing Operations

Currently, the City obtains approximately 87 percent of its required annual water supply from
Quincy Creek. Long-term records of daily flows (1974 1992) indicate that the maximum yearly flow is
30.3 MGD (47 cfs), the mean is 18.1 MGD (28 cfs) and the minimum yearly flow is 11.2 MGD (17.3 cfs).
Historically, the City and other upstream users withdraw 1.58 MGD (2.5 cfs) in an average day and a
maximum in one day of 2.3 MGD (3.5 cfs). During the drought of 1985-1986, a record minimum flow of
2.3 cfs was recorded at the U.S.G.S. gauge on May 7, 1985. Records indicate that during May 7 and 8,
the water treatment plant withdrew 1.49 MGD (2.3 cfs). An adjusted value of base flow in the creek
should include all upstream users that withdrew water from the stream during this period. There is no
withdrawal data available about the other two permitted upstream users, Gadsden County Golf with an
average daily demand of 0.19 MGD (0.3 cfs) and Manley Farms with an average daily demand of 0.13
MGD (0.2 cfs). The adjusted value of minimum base flow value for the creek, under the assumption that
there were no other upstream withdrawals during this period, is 3.29 MGD (5.1 cfs). This adjusted value

2 CH2M-Hill, 1990. City of Quincy, Florida Water Resources Study Final Report, January 1990.
19










of base flow represents a realistic value of the 1-day 18-year low flow or the absolute minimum baseflow
in the stream before being affected by water users for the period of record. Future water demands for
these three water users are 2.0 MGD (3.1 cfs) and 3.9 MGD (6.0 cfs) for the average daily and maximum
daily, respectively. From the frequency analysis, a return period of 50 years for a 3-day low flow and 100
years for a 7-day low flow period can be assigned to the minimum base flow of 2.3 cfs in the stream.
This means that in a given 100-year period, the creek cannot meet the maximum projected demand of
3.9 MGD (6.0 cfs) twice for a period of 3 days or once for a period of 7 consecutive days.

On occasions when extreme low flows occur, the City would be required to supplement water
taken from the creek with additional sources if the maximum projected demand is to be met at all times.
The other reason for a supplemental source of water is to provide flexibility to the system due to the
diminished water quality in Quincy Creek by natural or man-made causes. The CH2M-Hill report (1990)
recommends the development of new wells and the use of stored water in Interlocking Lakes as the most
feasible of alternative sources. In the next section, we will discuss the hydrology of the Colson Creek
basins and the potential ability of Interlocking Lakes to provide storage for water supply purposes
required further hydrologic study.


Alternative Operations

The operation of Interlocking Lakes as a storage reservoir for water supply purposes implies the
availability of enough natural base flow into the lakes so that a sizable amount of water can be released
during critical periods to replace or supplement the supply from Quincy Creek. To accomplish this goal
efficiently, it is necessary to understand the hydrologic response of the basin, in particular during drought
periods. Since there was no flow data at the outlet of the watershed, and little is known about the quality
of the water from the reservoir, a monitoring program was carried out for the duration of this study with
automatic flow recorders and water quality samplers. The two main purposes of this water sampling
effort was to determine the flow and quality characteristics of both Quincy Creek and Colson Creek
during the same rainfall events and to provide data for calibration of the hydrologic model.

Given state of the art hydrologic analysis tools, the best way to study the hydrologic response of
a watershed under different climate and man-made alternatives is with a properly calibrated hydrologic
model. The SWMM model can analyze the long-term effect of climate changes and structural and non-
structural management options. Among climate variables that can be altered are long-term precipitation
and evaporation patterns. For stormwater management purposes, the model can evaluate the effects of
structural controls such as modification, addition or removal of storage areas, flow conveyance elements
and flow control elements. Impacts on stormwater quantity and quality from non-structural measures
such as land use management and agricultural best management practices can also be analyzed by
altering the appropriate runoff parameters in the model. One current limitation of the TRANSPORT block
of the SWMM model, however, is the lack of evaporation computations during the routing of flows through
storage elements such as ponds or lakes. Because evaporation from a large reservoir such as the
Interlocking Lakes is an important factor in any long-term water budget, the code was modified to
accommodate evaporation losses from the lake based on monthly evaporation coefficients. These
coefficients were obtained from historical evaporation data available at the Jim Woodruff Dam, City of
Quincy, and other nearby weather stations.

In order to evaluate base flow yields for their ability to supply a reliable potable water supply, a
calibrated model at State Road 267 was used. A long-term precipitation record (1958-1991) of hourly
rainfall at Tallahassee and monthly evaporation coefficients were used as climate inputs into the model.
Since base flow yield analysis is the main purpose of this exercise, a time series or history of upstream
withdrawals must be incorporated into the model. No long-term daily withdrawal records exist that could
be used for this simulation. Therefore, to calibrate the model, historic flows for the period of record (1974
-1992) were used to determined base flows at the U.S.G.S. flow gauge. By assuming that the minimum
daily flow value of each month is representative of the base flow for that particular month, a time series of
base flows was generated and entered into the model as points discharging upstream of the U.S.G.S









gauge. Since these flows were recorded downstream of the water treatment plant, the recorded value of
flows reflects the effects of upstream withdrawals. The use of this assumed monthly-varied base flow
has the advantage over a constant value for example, of adding monthly seasonality to the base flow
input. One problem that arose during model calibration was the apportionment of base flow between the
Upper Quincy Creek and Colson Creek. By looking at the 10-minute recorded flow data at S284 and
S285 in terms of low flow conditions a value of about 60 percent of the total base flow at S286 is
contributed by Interlocking Lakes during this period of record (6 cfs out of 10 cfs at the right end of the
duration curves). Similar results would have been obtained if the fraction of the total contributing area
were applied to each gauge (38 percent for Upper Quincy Creek and 62 percent for Colson Creek). Low
flow duration curves developed for the data collection period show the effects of upstream withdrawals
from the creek at State Road 267 which shows the lowest baseflows of all three curves. In the other
hand, Interlocking Lakes is the largest contributor of base flows into Quincy Creek.

Results from the simulation using the history of base flows previously described were
summarized as a flow duration curve and compared to the duration curve from recorded flows for the
period of 1974 to 1991. Simulation results show good agreement between the modeled and recorded
duration curves for the 17-year simulation period. This also confirms the reasonableness of the assumed
monthly base flows obtained from the flow record at the S.R. 267 gage. Slight underestimation of base
flows by the model is apparent and possibly due to the fact that the absolute minimum recorded monthly
flows were used to account for base flows in the model. Because the model is being used to predict base
flow conditions, it is safe to use for long-term projections even if a slight underestimation of baseflows is
evident.

The first scenario simulated with the model was the long-term effect of Interlocking Lakes on the
base flows at S284. Flow duration curves were developed with the model for existing conditions and
existing conditions without lakes. From these curves, it is evident that the lake provides some attenuation
to high flows but little or no augmentation to low flows. This is probably due to the fact that the lakes
operate completely unregulated and were not designed for any purpose other than recreational. Another
interesting fact drawn from this analysis is that because of such little effect of storage on the lower portion
of the curve without lakes, it seems that there is no shortage of base flow into the lake over extended
periods of time. Apparently there is always, during the simulation, a running stream at S284 even without
lakes in place. For this case, it was assumed that the minimum flow recorded at the U.S.G.S. gage of
2.3 cfs would occur for a prolonged period (throughout the simulation period). This would be an extreme
case that is not likely to ever occur based on the current hydrologic data of the system.

In order to account for upstream withdrawals, it was assumed that 5.8 cfs of base flow entered
the system, 62 percent (3.596 cfs) of which entered the Interlocking Lakes and the remaining 38 percent
(2.204 cfs) entered the Upper Quincy Creek above State Road 268. All upstream Withdrawals (water
treatment plant, Gadsden Co. Golf and Manley Farms) occurred upstream of the U.S.G.S. gauge and
equaled 3.5 cfs. By subtracting this withdrawal figure from 5.8 cfs, one can account for the minimum
base flow of 2.3 cfs at the U.S.G.S. flow gauge. Flow duration curves for this hypothetical extreme
drought simulation for the period of 1958 to 1991 showed that minimum flows from Interlocking Lakes of
about 4.0 cfs can be maintained for over 99 percent of the time for an average period of about 32.7
years. The analysis also showed that the effect of the lakes is minimal in augmenting low flows but more
substantial for peak flow attenuation.











Water Quality Problems


Quincy Creek

The City of Quincy uses Quincy Creek as its primary source of potable water, therefore, Class I
quality standards must be maintained in the creek. Water availability in the creek is not only a function of
water quantity but also a function of the water quality maintenance in the stream. High turbidity levels in
the creek's waters, after significant storm events, make the water supply from the creek temporarily
inadequate forcing the City to supplement its supply with groundwater that is also limited in quality and
availability.

Turbidity is a physical quality parameter of water that indicates its tendency to scatter light
because of the presence of particulates. Turbidity is of concern because of its potential for interfering
with disinfection processes and microbiological analysis methods. It may affect disinfection by interfering
with formation of disinfectant residuals or by shielding pathogenic organisms from the disinfectant and it
may also cause false negative bacteriologic tests' results.

Current regulations for filtered water require daily turbidity measurements whose monthly average
may not exceed 1 NTU. In addition, turbidity may not exceed 5 NTU as an average of any two
consecutive days. New federal regulations also limit turbidity to less than 0.5 NTU in more than 5 percent
of the measurements in any month. City of Quincy water treatment plant operators have reported
turbidity levels in the Creek of about 10 NTU (unfiltered), and as high as 250 NTU after significant rainfall
events. Alum treatment to remove high levels of turbidity after high turbidity surges has often proven
inadequate. Lime application after filtration is now added to the treatment to increase alkalinity in the
water, and hence, coagulation and flocculation. All these additional treatment processes significantly
increase the operating costs of water purification and, when ineffective, the City utilizes groundwater
water to meet the demand. Further discussion of water quality is included in the Stormwater Quality
Evaluation section of this report.


Tanyard Branch

No previous information about the water quality in Tanyard Branch was available prior to this
study. A limited water quality sampling program was necessary to identify possible quality constituents in
violation of Class III standards. As expected, the quality of the waters in Tanyard Branch is typical runoff
from heavily urbanized areas with high levels of nutrients, turbidity, zinc, cadmium and chromium
according to Class III water quality standards.











Water Quality Problems


Quincy Creek

The City of Quincy uses Quincy Creek as its primary source of potable water, therefore, Class I
quality standards must be maintained in the creek. Water availability in the creek is not only a function of
water quantity but also a function of the water quality maintenance in the stream. High turbidity levels in
the creek's waters, after significant storm events, make the water supply from the creek temporarily
inadequate forcing the City to supplement its supply with groundwater that is also limited in quality and
availability.

Turbidity is a physical quality parameter of water that indicates its tendency to scatter light
because of the presence of particulates. Turbidity is of concern because of its potential for interfering
with disinfection processes and microbiological analysis methods. It may affect disinfection by interfering
with formation of disinfectant residuals or by shielding pathogenic organisms from the disinfectant and it
may also cause false negative bacteriologic tests' results.

Current regulations for filtered water require daily turbidity measurements whose monthly average
may not exceed 1 NTU. In addition, turbidity may not exceed 5 NTU as an average of any two
consecutive days. New federal regulations also limit turbidity to less than 0.5 NTU in more than 5 percent
of the measurements in any month. City of Quincy water treatment plant operators have reported
turbidity levels in the Creek of about 10 NTU (unfiltered), and as high as 250 NTU after significant rainfall
events. Alum treatment to remove high levels of turbidity after high turbidity surges has often proven
inadequate. Lime application after filtration is now added to the treatment to increase alkalinity in the
water, and hence, coagulation and flocculation. All these additional treatment processes significantly
increase the operating costs of water purification and, when ineffective, the City utilizes groundwater
water to meet the demand. Further discussion of water quality is included in the Stormwater Quality
Evaluation section of this report.


Tanyard Branch

No previous information about the water quality in Tanyard Branch was available prior to this
study. A limited water quality sampling program was necessary to identify possible quality constituents in
violation of Class III standards. As expected, the quality of the waters in Tanyard Branch is typical runoff
from heavily urbanized areas with high levels of nutrients, turbidity, zinc, cadmium and chromium
according to Class III water quality standards.











Water Quality Problems


Quincy Creek

The City of Quincy uses Quincy Creek as its primary source of potable water, therefore, Class I
quality standards must be maintained in the creek. Water availability in the creek is not only a function of
water quantity but also a function of the water quality maintenance in the stream. High turbidity levels in
the creek's waters, after significant storm events, make the water supply from the creek temporarily
inadequate forcing the City to supplement its supply with groundwater that is also limited in quality and
availability.

Turbidity is a physical quality parameter of water that indicates its tendency to scatter light
because of the presence of particulates. Turbidity is of concern because of its potential for interfering
with disinfection processes and microbiological analysis methods. It may affect disinfection by interfering
with formation of disinfectant residuals or by shielding pathogenic organisms from the disinfectant and it
may also cause false negative bacteriologic tests' results.

Current regulations for filtered water require daily turbidity measurements whose monthly average
may not exceed 1 NTU. In addition, turbidity may not exceed 5 NTU as an average of any two
consecutive days. New federal regulations also limit turbidity to less than 0.5 NTU in more than 5 percent
of the measurements in any month. City of Quincy water treatment plant operators have reported
turbidity levels in the Creek of about 10 NTU (unfiltered), and as high as 250 NTU after significant rainfall
events. Alum treatment to remove high levels of turbidity after high turbidity surges has often proven
inadequate. Lime application after filtration is now added to the treatment to increase alkalinity in the
water, and hence, coagulation and flocculation. All these additional treatment processes significantly
increase the operating costs of water purification and, when ineffective, the City utilizes groundwater
water to meet the demand. Further discussion of water quality is included in the Stormwater Quality
Evaluation section of this report.


Tanyard Branch

No previous information about the water quality in Tanyard Branch was available prior to this
study. A limited water quality sampling program was necessary to identify possible quality constituents in
violation of Class III standards. As expected, the quality of the waters in Tanyard Branch is typical runoff
from heavily urbanized areas with high levels of nutrients, turbidity, zinc, cadmium and chromium
according to Class III water quality standards.










Stormwater Quality Evaluation


As part of this study, the Northwest Florida Water Management District established four water
quality samplers, four streamflow and one rainfall recorder. One flow recorder and a water quality
sampler were established about 1,000 feet downstream of the dam. The recorder on Colson Creek
(S284) monitored the flow and quality conditions for the discharge from the reservoir. One flow/rain
recorder and quality sampler were also placed in Quincy Creek at State Road 268 (S285) about 3,500
feet upstream of the confluence on Quincy Creek and Colson Creek. These recorders provided
information about the flows upstream of the water treatment plant, before they combine with the flows
from Colson Creek. A third quality sampler was installed at Quincy Creek and State Road 267 to be used
in conjunction with the U.S.Geological Survey (U.S.G.S.) flow gauge. The combined effects of flows and
pollutants from the upper Quincy Creek basin, Colson Creek, and other upstream users can be seen at
this gauge (S286). In all, 17 months of data were continuously collected at 10-minute intervals. These
time series were used to characterize flows at locations of interest and to calibrate and verify a
continuous hydrologic model for the study area. The streamflow data collected consists of values of the
water surface elevation recorded at 10-minute intervals. Water elevations were subsequently translated
into flow rate by a rating curve developed for each sampling site.

The water quality data collected during this study consisted mainly of one composite sample per
site per event. A total of four events were sampled for water quality. The composite samples were
formed following U.S. Environmental Protection Agency (EPA) and Florida Department of Environmental
Protection (DEP) sampling and mixing field procedures. The samples were prepared and taken
immediately after each storm event to the DEP laboratory in Tallahassee for chemical analysis. A
summary of the water quality sampling program is presented and discussed in the water quality section of
the City of Quincy Stormwater Management Plan.

The stormwater sampling and water quality analysis were a preliminary monitoring program
intended to meet three main objectives. The primary objective was to evaluate water quality during storm
events upstream of the City's water treatment plant intakes; a second and closely related objective was to
characterize the quality of stormwater discharges with respect to State of Florida water quality standards;
and the third objective was to consider additional stormwater monitoring needs and alternatives for
stormwater pollution control.

In general, urban nonpoint pollutant sources that affect the quality of stormwater may include:
materials washed from urban surfaces; construction; industry; atmospheric deposition; golf courses;
fertilizer application; herbicide and pesticide application; storage tank leaks; and spills. Rural nonpoint
sources that are an additional concern related to the City's water supply include agriculture, mining, and
land clearing activities. The categories of contaminants that can be indicative of a problem from potential
nonpoint sources in the study area include suspended solids and turbidity, metals, nutrients, biological
oxygen demand, pesticides, toxic organic, oil and grease, and bacterial pathogens. The parameters
sampled for in stormwater under this scope of work include solids, turbidity, nutrients and metals. The
next section provides a summary of these sampling results that is used for later discussion of alternatives
for water quality treatment.


Summary of Water Quality Sampling Results

Water quality sampling was conducted at four locations that were strategically located according
to anticipated problem areas. Each of the sampling station locations coincides with the subbasins
monitored and stormwater flow measuring stations set up for the hydrologic analysis portion of this study.
This scope of work was limited to sampling at four stations. Thus, the overall approach for selecting
monitoring stations was to address water quality in a comprehensive manner and on a regional
watershed basis rather than to address the individual site specific problems that may contribute to
degraded water quality.










Stormwater Quality Evaluation


As part of this study, the Northwest Florida Water Management District established four water
quality samplers, four streamflow and one rainfall recorder. One flow recorder and a water quality
sampler were established about 1,000 feet downstream of the dam. The recorder on Colson Creek
(S284) monitored the flow and quality conditions for the discharge from the reservoir. One flow/rain
recorder and quality sampler were also placed in Quincy Creek at State Road 268 (S285) about 3,500
feet upstream of the confluence on Quincy Creek and Colson Creek. These recorders provided
information about the flows upstream of the water treatment plant, before they combine with the flows
from Colson Creek. A third quality sampler was installed at Quincy Creek and State Road 267 to be used
in conjunction with the U.S.Geological Survey (U.S.G.S.) flow gauge. The combined effects of flows and
pollutants from the upper Quincy Creek basin, Colson Creek, and other upstream users can be seen at
this gauge (S286). In all, 17 months of data were continuously collected at 10-minute intervals. These
time series were used to characterize flows at locations of interest and to calibrate and verify a
continuous hydrologic model for the study area. The streamflow data collected consists of values of the
water surface elevation recorded at 10-minute intervals. Water elevations were subsequently translated
into flow rate by a rating curve developed for each sampling site.

The water quality data collected during this study consisted mainly of one composite sample per
site per event. A total of four events were sampled for water quality. The composite samples were
formed following U.S. Environmental Protection Agency (EPA) and Florida Department of Environmental
Protection (DEP) sampling and mixing field procedures. The samples were prepared and taken
immediately after each storm event to the DEP laboratory in Tallahassee for chemical analysis. A
summary of the water quality sampling program is presented and discussed in the water quality section of
the City of Quincy Stormwater Management Plan.

The stormwater sampling and water quality analysis were a preliminary monitoring program
intended to meet three main objectives. The primary objective was to evaluate water quality during storm
events upstream of the City's water treatment plant intakes; a second and closely related objective was to
characterize the quality of stormwater discharges with respect to State of Florida water quality standards;
and the third objective was to consider additional stormwater monitoring needs and alternatives for
stormwater pollution control.

In general, urban nonpoint pollutant sources that affect the quality of stormwater may include:
materials washed from urban surfaces; construction; industry; atmospheric deposition; golf courses;
fertilizer application; herbicide and pesticide application; storage tank leaks; and spills. Rural nonpoint
sources that are an additional concern related to the City's water supply include agriculture, mining, and
land clearing activities. The categories of contaminants that can be indicative of a problem from potential
nonpoint sources in the study area include suspended solids and turbidity, metals, nutrients, biological
oxygen demand, pesticides, toxic organic, oil and grease, and bacterial pathogens. The parameters
sampled for in stormwater under this scope of work include solids, turbidity, nutrients and metals. The
next section provides a summary of these sampling results that is used for later discussion of alternatives
for water quality treatment.


Summary of Water Quality Sampling Results

Water quality sampling was conducted at four locations that were strategically located according
to anticipated problem areas. Each of the sampling station locations coincides with the subbasins
monitored and stormwater flow measuring stations set up for the hydrologic analysis portion of this study.
This scope of work was limited to sampling at four stations. Thus, the overall approach for selecting
monitoring stations was to address water quality in a comprehensive manner and on a regional
watershed basis rather than to address the individual site specific problems that may contribute to
degraded water quality.











The primary objective of this scope of work was to consider stormwater quality impacts on water
treatment plant operations. Three of the four monitoring stations S284, S285, and S286 were provided
specifically for this purpose. S284 and S285 was selected to quantify the differences in surface water
quality between the two main subbasins (Upper Quincy Creek and Colson Creek) which provide the City
with drinking water. Both stations are outside the City limits and consist of a land use mix which is mostly
agricultural and forested land. Surface mining for raw materials also takes place in the watershed above
station S285. Station S286 was selected because it is representative of the water supply plant intake on
Quincy Creek and the entire watershed area above the intake. Station S286 is also representative of
background water quality in Quincy Creek. Station S283, on Tanyard Branch was selected to quantify
the overall quality of stormwater discharging from the City into Quincy Creek. Station S283 was
particularly suited for this purpose because nearly all of the stormwater drainage from developed land
within the City discharges to Tanyard Branch through an extensive network of storm sewers. Land use in
the Tanyard Branch watershed is almost entirely urban.

Stormwater samples were collected by automatic ISCO samplers (Model 2700) which took
samples according to a pre-determined schedule., These sampling schedules were designed to obtain
more samples around the peak of the hydrographs. When a storm was anticipated, the samplers were
prepared with empty bottles. If the storm met the storm criteria established by EPA NPDES sampling
guidelines of at least 0.1 inches of rain and three dry weather days before the storm, the storm samples
were processed for laboratory analysis. Otherwise, the samples were discarded and the equipment reset
for the next storm event. After a successful event and the sample bottles had been collected, a flow-
weighted average sample was composite from the individual sample bottles. For this purpose, the
portion of the total volume associated with each sampling time determined the fraction of each bottle to
be added to the composite sample. Further details and references on the gaging and testing procedures
used in this study are provided in the NWFWMD Quality Assurance and Quality Control Comprehensive
Plan, the Florida Department of Environmental Regulation (FDER) Laboratory Quality Assurance and
Quality Control Comprehensive Plan, the U.S. EPA Stormwater Sampling guidelines and the operator's
manuals for the Handar 550 flow data recorder and ISCO autosampler.

The sampling program was designed to collect samples simultaneously at all four sampling sites
for each storm event sampled. This was accomplished for all of the events successfully sampled except
for one occasion (storm of June 29, 1993) when an equipment failure on Tanyard Branch prevented the
use of the sample collected there. A total of four storm events were sampled during this study. The
samples were analyzed by the FDEP laboratory in Tallahassee, Florida, and the sample analyses
reported by the laboratory were stored and archived in a digital format, in the NWFWMD water quality
data base.

The scope of this water quality sampling program was limited to performing laboratory chemical
analyses on three general categories of contaminants. Nutrients including nitrogen and phosphorous
determinations may be used to consider problems associated with eutrophication or nutrient imbalances
in surface water bodies that may result in noxious growths of algae and depressed oxygen levels for fish.
Turbidity and solids' determinations for this study are primarily directed at problems associated with
treatment of water for public consumption, related problems associated with exceeding water quality
standards for Class I waters, and impacts on receiving waters that support fish and wildlife. The selected
metals' determinations may be used to consider water quality standards violations. All of the laboratory
determinations may be utilized to help evaluate water quality problems associated with stormwater
discharges from urban or developed areas.









Water Quality Sampling Results


Concentration data reported by the FDEP laboratory for each constituent analyzed showed that
Class I water quality standards were only exceeded for turbidity. The Upper Quincy Creek watershed
station (S285) at SR 268 exceeded Class I standards on four sampling occasions. The Quincy Creek
station, S286 near the water plant intake, exceeded turbidity twice and was always much lower in turbidity
than the site at S285. The lowest turbidity values were found at Colson Creek (S284). Although the
differences between Upper Quincy Creek and Colson Creek turbidity could be because of watershed
differences, it is more likely that the lower values are due to the treatment effect afforded by the
Interlocking Lakes. There was one occasion when the Colson Creek discharge had slightly elevated
turbidity levels. However, turbidity at the plant intake remained low at this time. Localized stream bed
erosion and shallow channel depths during this sample period may have caused an instantaneously
higher reading than usual at the Colson Creek site.

The Tanyard Branch sampling site (S283) was not considered for Class I standards because the
discharge to Quincy Creek is below the public supply intakes and the wastewater treatment plant
discharge outfall However, it exceeded Class III water quality standards for turbidity and zinc on all three
of the occasions it was sampled. Other metals' concentrations from the Tanyard Branch discharge which
exceeded Class III standards were cadmium (twice) and chromium (once). The quality of water samples
from Tanyard Branch that exceed Class III water quality standards reflect the discharge of stormwater
from an area that is predominantly urban. Nutrient loadings to Tanyard Branch also appear elevated.
High nutrient loadings is of primary concern in this region due to the high recreational fishing value of the
Ochlockonee River and Lake Talquin. These water bodies ultimately receive the discharge of stormwater
from the study area.


Loading Rate Relationships with Existing Land Use

As a basis for comparing the sample data with literature based land use loading rates, the
sample concentration data at stations S283, S284, and S285, was multiplied by the storm event volumes
to obtain sample pollutant load estimates. The average of the storm event loads divided by the basin
area and the model computed annual average runoff amount above each station maybe used to estimate
the average annual loading rate in units of Ibs/acre/year. Due to the limited amount of sampling data, no
attempt was made to flow weight the sample loading estimates over a long-term annual basis.

The parameters for this water quality analysis were limited to the conventional type loading rates
most commonly found in the literature including total nitrogen, total phosphorus and total suspended
solids. The literature based values are land use loading rate estimates that have been developed for
other locations in the Northwest Florida Water Management District and therefore, can only be used to
evaluate land use changes on a relative basis.

Overall the loading estimates are in agreement with the sampling data on a relative basis except
for total suspended solids and total phosphorus load estimates at Colson Creek. It is suspected that the
Interlocking Lakes have a significant treatment effect that the land use loading estimating method does
not account for. It is well known that lake or reservoir systems can behave as significant sediment and
phosphorus traps. Elsewhere, the Tanyard Branch station and the upper Quincy Creek Station loading
rate estimates from the sample data are relatively in agreement with the literature values. Because the
results of these two watersheds are in relative agreement, the land use loading rates based on the
literature values are useful for estimating pollutant loads from urban and non-urban type land uses, at
least for preliminary planning purposes.









Water Quality Sampling Results


Concentration data reported by the FDEP laboratory for each constituent analyzed showed that
Class I water quality standards were only exceeded for turbidity. The Upper Quincy Creek watershed
station (S285) at SR 268 exceeded Class I standards on four sampling occasions. The Quincy Creek
station, S286 near the water plant intake, exceeded turbidity twice and was always much lower in turbidity
than the site at S285. The lowest turbidity values were found at Colson Creek (S284). Although the
differences between Upper Quincy Creek and Colson Creek turbidity could be because of watershed
differences, it is more likely that the lower values are due to the treatment effect afforded by the
Interlocking Lakes. There was one occasion when the Colson Creek discharge had slightly elevated
turbidity levels. However, turbidity at the plant intake remained low at this time. Localized stream bed
erosion and shallow channel depths during this sample period may have caused an instantaneously
higher reading than usual at the Colson Creek site.

The Tanyard Branch sampling site (S283) was not considered for Class I standards because the
discharge to Quincy Creek is below the public supply intakes and the wastewater treatment plant
discharge outfall However, it exceeded Class III water quality standards for turbidity and zinc on all three
of the occasions it was sampled. Other metals' concentrations from the Tanyard Branch discharge which
exceeded Class III standards were cadmium (twice) and chromium (once). The quality of water samples
from Tanyard Branch that exceed Class III water quality standards reflect the discharge of stormwater
from an area that is predominantly urban. Nutrient loadings to Tanyard Branch also appear elevated.
High nutrient loadings is of primary concern in this region due to the high recreational fishing value of the
Ochlockonee River and Lake Talquin. These water bodies ultimately receive the discharge of stormwater
from the study area.


Loading Rate Relationships with Existing Land Use

As a basis for comparing the sample data with literature based land use loading rates, the
sample concentration data at stations S283, S284, and S285, was multiplied by the storm event volumes
to obtain sample pollutant load estimates. The average of the storm event loads divided by the basin
area and the model computed annual average runoff amount above each station maybe used to estimate
the average annual loading rate in units of Ibs/acre/year. Due to the limited amount of sampling data, no
attempt was made to flow weight the sample loading estimates over a long-term annual basis.

The parameters for this water quality analysis were limited to the conventional type loading rates
most commonly found in the literature including total nitrogen, total phosphorus and total suspended
solids. The literature based values are land use loading rate estimates that have been developed for
other locations in the Northwest Florida Water Management District and therefore, can only be used to
evaluate land use changes on a relative basis.

Overall the loading estimates are in agreement with the sampling data on a relative basis except
for total suspended solids and total phosphorus load estimates at Colson Creek. It is suspected that the
Interlocking Lakes have a significant treatment effect that the land use loading estimating method does
not account for. It is well known that lake or reservoir systems can behave as significant sediment and
phosphorus traps. Elsewhere, the Tanyard Branch station and the upper Quincy Creek Station loading
rate estimates from the sample data are relatively in agreement with the literature values. Because the
results of these two watersheds are in relative agreement, the land use loading rates based on the
literature values are useful for estimating pollutant loads from urban and non-urban type land uses, at
least for preliminary planning purposes.











Future Land Use Loading Projections


The most distinct feature of the land use analysis previously discussed is that the net change in
land use type in the future is small relative to the existing land uses in the study area. With some
exceptions, therefore, it can be reasonably concluded that without any additional stormwater
management controls, future stormwater pollutant loads will be very similar to existing conditions. The
exceptions are where significant changes in planned land uses occur which result in the more intense use
of the land and a corresponding estimated increase in loading rate.

The primary areas where significant changes in land use are projected are in subbasins 3, 4, 8,
14, 20, 22, 23, 24, and 25 (see Figure 2). For most subbasins within City limits, the primary shift for
future development is from vacant or open land to residential and mining uses. The primary shift in
subbasin 14 is from vacant land to residential, commercial, and industrial land uses. The primary land
use shift in the rural areas is from vacant land to agricultural and mining uses. It is noteworthy to note the
change in land use type in subbasin 4. The future land use would result in changes in land use activities
but the intensity of land use and future loading rates would remain about the same. This is because the
planned change is from agricultural to residential and commercial land uses.


Relationships to Historical Water Quality Data

Historical data reported in the vicinity of the study area dates back to the 1970's through a
sampling program by the U.S. Geological Survey and a pilot project which was an element of the
statewide 208 Plan Nonpoint Source Assessment. The water quality data available in this report was of
limited use because it was collected for different purposes and different hydrologic conditions, and it is
somewhat outdated with regard to current land use and watershed conditions. Sampling technique,
sample locations and analyses in the 208 Study were also dissimilar to the current study, and focused on
the quality of stormwater runoff from agricultural and forested mixed uses rather than the quality of the
City's water supply and urban stormwater quality. Nevertheless, the review of historical water quality
concentration data was undertaken to determine if there were any large differences over time which might
be related to changes in watershed management activities, conservation practices, and land use
activities.

Only two sample locations used in the 208 study could be compared directly to the data collected
in the current study. The first comparable station was Quincy Creek at S. R. 267. The U.S. Geological
Survey data collected at this station represents instantaneous grab samples taken at various stream
flows and times over the period 1974 to 1987. Samples taken during the U.S.G.S. study were usually for
low flow conditions rather than for high flow stormwater conditions. However, when samples were
collected during higher flows, turbidity values have historically been elevated above 10 NTU (maximum of
45 NTU). Although not directly comparable with the flow weighted sampling techniques for stormwater
analysis, clearly higher turbidity has historically been a problem during higher flows. In the CH2M-Hill
report (1990), intermittently high turbidity was attributed to stormwater discharges and the mining of
Fuller's earth in the Quincy Creek headwaters. However, unpaved roads and agricultural tilling
operations are other potential sources for high turbidity.

Although no other trends in comparable historic data at the State Road 267 (S286) station were
remarkable, data collected at this station by the U.S.G.S. indicate that EPA secondary standards for raw
water supplies were almost always exceeded for iron and intermittently exceeded for manganese. The
surface waters in the study area have been known to be characteristically high in iron and manganese.
Water which exceeds these water quality standards is difficult to treat for public supply. Because the
station at State Road 267 represents a mix of both the Colson Creek watershed and the upper Quincy
Creek watershed it is not known if iron or manganese concentrations would be lower at upstream
locations.











Future Land Use Loading Projections


The most distinct feature of the land use analysis previously discussed is that the net change in
land use type in the future is small relative to the existing land uses in the study area. With some
exceptions, therefore, it can be reasonably concluded that without any additional stormwater
management controls, future stormwater pollutant loads will be very similar to existing conditions. The
exceptions are where significant changes in planned land uses occur which result in the more intense use
of the land and a corresponding estimated increase in loading rate.

The primary areas where significant changes in land use are projected are in subbasins 3, 4, 8,
14, 20, 22, 23, 24, and 25 (see Figure 2). For most subbasins within City limits, the primary shift for
future development is from vacant or open land to residential and mining uses. The primary shift in
subbasin 14 is from vacant land to residential, commercial, and industrial land uses. The primary land
use shift in the rural areas is from vacant land to agricultural and mining uses. It is noteworthy to note the
change in land use type in subbasin 4. The future land use would result in changes in land use activities
but the intensity of land use and future loading rates would remain about the same. This is because the
planned change is from agricultural to residential and commercial land uses.


Relationships to Historical Water Quality Data

Historical data reported in the vicinity of the study area dates back to the 1970's through a
sampling program by the U.S. Geological Survey and a pilot project which was an element of the
statewide 208 Plan Nonpoint Source Assessment. The water quality data available in this report was of
limited use because it was collected for different purposes and different hydrologic conditions, and it is
somewhat outdated with regard to current land use and watershed conditions. Sampling technique,
sample locations and analyses in the 208 Study were also dissimilar to the current study, and focused on
the quality of stormwater runoff from agricultural and forested mixed uses rather than the quality of the
City's water supply and urban stormwater quality. Nevertheless, the review of historical water quality
concentration data was undertaken to determine if there were any large differences over time which might
be related to changes in watershed management activities, conservation practices, and land use
activities.

Only two sample locations used in the 208 study could be compared directly to the data collected
in the current study. The first comparable station was Quincy Creek at S. R. 267. The U.S. Geological
Survey data collected at this station represents instantaneous grab samples taken at various stream
flows and times over the period 1974 to 1987. Samples taken during the U.S.G.S. study were usually for
low flow conditions rather than for high flow stormwater conditions. However, when samples were
collected during higher flows, turbidity values have historically been elevated above 10 NTU (maximum of
45 NTU). Although not directly comparable with the flow weighted sampling techniques for stormwater
analysis, clearly higher turbidity has historically been a problem during higher flows. In the CH2M-Hill
report (1990), intermittently high turbidity was attributed to stormwater discharges and the mining of
Fuller's earth in the Quincy Creek headwaters. However, unpaved roads and agricultural tilling
operations are other potential sources for high turbidity.

Although no other trends in comparable historic data at the State Road 267 (S286) station were
remarkable, data collected at this station by the U.S.G.S. indicate that EPA secondary standards for raw
water supplies were almost always exceeded for iron and intermittently exceeded for manganese. The
surface waters in the study area have been known to be characteristically high in iron and manganese.
Water which exceeds these water quality standards is difficult to treat for public supply. Because the
station at State Road 267 represents a mix of both the Colson Creek watershed and the upper Quincy
Creek watershed it is not known if iron or manganese concentrations would be lower at upstream
locations.













The second comparable station was on Quincy Creek at S. R. 268. The historical data for this
station was collected during the 208 study period in the late 1970's. The sampling technique used was
grab samples taken during discrete time intervals over a storm event and at low flow. This technique
differs somewhat than the composite sampling method, used in the current study to obtain one sample of
an entire storm event. However, in comparing like parameters between the two data sets including
nutrients, suspended solids, and turbidity, apparently the magnitude of the pollutant concentrations in the
upper Quincy Creek watershed is about the same today as in the 1970's. Both turbidity and nutrient
concentrations continue to be high.











Stormwater Management Alternatives


Flood Reduction Alternatives Analysis

The primary focus for selecting alternatives for the City of Quincy was to design affordable
effective stormwater conveyances and storage areas that can reduce flooding problems and where
possible, provide water quality benefits. Consideration of the use of storage areas and maintenance of
existing systems was prerequisite before any new structural improvements were considered.

The principal tools utilized to evaluate flooding in the drainage branches selected for this study
were the RUNOFF, TRANSPORT, EXTRAN and STATISTICS blocks of the SWMM model. The runoff
block was used to generate the surface runoff entering the drainage system based on predetermined
rainfall patterns. The TRANSPORT block was utilized to perform long-term routing of runoff in the
system. Frequency analysis of peak flows and surface water profile generation was then applied to the
simulated flow time series throughout the study area. The EXTRAN block was used to transport runoff
through the drainage system for short duration critical storms. The use of EXTRAN allowed for the
evaluation of dynamic flooding conditions along the drainage system. The STATISTICS block was used
as a post-processor of long-term simulation data from TRANSPORT to obtain frequency distribution of
flows.

The majority of the flooding in the study area is confined to street flooding in areas shown in
Figure 3. Flood damages to a few structures exist in the floodplain south of Experiment Station Road and
in a low area north of the railroad tracks near King and 12th streets (junction JKE9A in the model).
Flooding analysis of the area south of Experiment Station Road indicates that the existing open channel
and culverts are adequately sized but only under maintained conditions. Structures currently located in
the flood plain that occasionally flood cannot be protected without extensive increases in the conveyance
in the channel. These structures can be protected through less expensive flood proofing measures.
Relatively free of sedimentation and excessive plant growth, the existing conveyances should adequately
drain stormwater runoff up to the 25-year return period events. Future development in the floodplain
areas should be discouraged and prevented when possible.

Flooding has been recently reported by the City in the southwest corner of the study area due to
a constricted open drainage ditch. Stormwater runoff from about 100 acres north of Hamilton Street
between Atlanta and Virginia streets, is drained to the basin outlet by an open channel which starts at
Virginia Street and extends in a southeasterly direction towards Cox Creek. Increased sediment loading
from recent development in the basin has plugged the outlet ditch just downstream of a culvert under
Virginia Street preventing the runoff from the western portion of the subbasins to freely continue towards
the subbasin's outlet at Cox Creek. This problem can be relatively easily to address by the City by
regrading the channel and routine maintenance. It is recommended as part of this study that the City of
Quincy gain access to this area and remove the plug of fill from the channel. Permanent access to the
site will most likely be needed due to future sedimentation problems. Although no estimation of quantity
to be removed was made, the amount of fill to be removed appears to be small and the costs associated
with removal should be minor. All work could most likely be completed in two days by one light rubber
tired backhoe and a dump truck.

Upon review of the existing condition model output, structural and non-structural alternatives
were examined as possible solutions. The data from the alternatives modeled indicated that no structural
alternative of reasonable cost would eliminate all flooding up through the 25-year rainfall events so
alternatives that offered protection less frequently were examined for suitability. The list of structural
alternatives considered in this study is shown in Table 3 with recommended alternatives.

The recommended alternative for the East King Street Branch is the purchase of the property
that floods. This alternative was chosen because no economical conduit changes could be proposed that











Stormwater Management Alternatives


Flood Reduction Alternatives Analysis

The primary focus for selecting alternatives for the City of Quincy was to design affordable
effective stormwater conveyances and storage areas that can reduce flooding problems and where
possible, provide water quality benefits. Consideration of the use of storage areas and maintenance of
existing systems was prerequisite before any new structural improvements were considered.

The principal tools utilized to evaluate flooding in the drainage branches selected for this study
were the RUNOFF, TRANSPORT, EXTRAN and STATISTICS blocks of the SWMM model. The runoff
block was used to generate the surface runoff entering the drainage system based on predetermined
rainfall patterns. The TRANSPORT block was utilized to perform long-term routing of runoff in the
system. Frequency analysis of peak flows and surface water profile generation was then applied to the
simulated flow time series throughout the study area. The EXTRAN block was used to transport runoff
through the drainage system for short duration critical storms. The use of EXTRAN allowed for the
evaluation of dynamic flooding conditions along the drainage system. The STATISTICS block was used
as a post-processor of long-term simulation data from TRANSPORT to obtain frequency distribution of
flows.

The majority of the flooding in the study area is confined to street flooding in areas shown in
Figure 3. Flood damages to a few structures exist in the floodplain south of Experiment Station Road and
in a low area north of the railroad tracks near King and 12th streets (junction JKE9A in the model).
Flooding analysis of the area south of Experiment Station Road indicates that the existing open channel
and culverts are adequately sized but only under maintained conditions. Structures currently located in
the flood plain that occasionally flood cannot be protected without extensive increases in the conveyance
in the channel. These structures can be protected through less expensive flood proofing measures.
Relatively free of sedimentation and excessive plant growth, the existing conveyances should adequately
drain stormwater runoff up to the 25-year return period events. Future development in the floodplain
areas should be discouraged and prevented when possible.

Flooding has been recently reported by the City in the southwest corner of the study area due to
a constricted open drainage ditch. Stormwater runoff from about 100 acres north of Hamilton Street
between Atlanta and Virginia streets, is drained to the basin outlet by an open channel which starts at
Virginia Street and extends in a southeasterly direction towards Cox Creek. Increased sediment loading
from recent development in the basin has plugged the outlet ditch just downstream of a culvert under
Virginia Street preventing the runoff from the western portion of the subbasins to freely continue towards
the subbasin's outlet at Cox Creek. This problem can be relatively easily to address by the City by
regrading the channel and routine maintenance. It is recommended as part of this study that the City of
Quincy gain access to this area and remove the plug of fill from the channel. Permanent access to the
site will most likely be needed due to future sedimentation problems. Although no estimation of quantity
to be removed was made, the amount of fill to be removed appears to be small and the costs associated
with removal should be minor. All work could most likely be completed in two days by one light rubber
tired backhoe and a dump truck.

Upon review of the existing condition model output, structural and non-structural alternatives
were examined as possible solutions. The data from the alternatives modeled indicated that no structural
alternative of reasonable cost would eliminate all flooding up through the 25-year rainfall events so
alternatives that offered protection less frequently were examined for suitability. The list of structural
alternatives considered in this study is shown in Table 3 with recommended alternatives.

The recommended alternative for the East King Street Branch is the purchase of the property
that floods. This alternative was chosen because no economical conduit changes could be proposed that










would adequately prevent structural damage. The estimated purchase price does not include the
additional costs of removing the three existing structures which receive damage. The alternative for the
Monroe Street Branch should provide flood protection up to the statistical 5-year/12-hour rainfall event.
The recommended alternative for the West King Street Branch should provide flood protection up to the
statistical 1-year/12-hour rainfall event and significantly reduce the street flooding for most other rain
events.


TABLE 3

Evaluation of Alternatives


Advantages:


Disadvantages:


Advantages:


Disadvantages:


King St. East Branch Land Purchase
Alternative "A"
Estimated Cost $100,000


Eliminates all flooding damages by removing damaged structures from
low area

Reduces liability and risk of flooding related accidents in area

Minimal construction impacts on community

Land has potential as recreation area

If pondage of stormwater is allowed after implementation, potential
treatment to water quality can be drawn from this alternative.


High cost of construction


Periodic maintenance required for storage area to drain properly

Displacement of residents



King St. East Branch Conduit Enlargement
Alternative "B"
Estimated Cost $34,380

Lower cost than land purchase


Possible sewer surcharge flooding beyond 5-year/12-hour statistical
rainfall event.

Low structures in flood plain may still need to be purchased by City.





















Advantages:


Disadvantages:








Advantages:


Disadvantages:







Advantages:




Disadvantages:


Advantages:


Disadvantages:


TABLE 3
(Continued)

Evaluation of Alternatives


King St. West Branch Conduit Enlargement
Alternative "A"
Estimated Cost $163,980

Minimizes or eliminates street flooding up to the five year statistical
rainfall event.

High cost

Construction impacts on other utilities, traffic and community


King St. West Branch Conduit Enlargement
Alternative "B"
Estimated Cost $184,140

None


When modeled, this alternative caused an increase in downstream street
flooding.


Monroe St. Branch Conduit Enlargement
Alternative "A"
Estimated Cost $26,652

Eliminates street flooding up to five year statistical rainfall event

Low Cost


Does not totally correct street flooding problem up through 25-year
rainfall events

Construction impacts on community



Monroe St. Branch Conduit Enlargement
Alternative "B"
Estimated Cost $99,840

None


When modeled, this alternative caused an increase in downstream street
flooding.











Stormwater Quality Alternatives Analysis


Stormwater alternatives for water quality improvements in this plan fall into three categories as
follows:

1. Urban Runoff Pollution controls alternatives within City limits;
2. Water treatment plant alternatives; and
3. Stormwater monitoring alternatives.


Urban Runoff Pollution Control Alternatives

Within the City's urban services area it is very clear that the most significant problem concerning
pollutant loading to streams is the existing land use condition rather than the net change in land use due
to future growth. This is a common problem in well established communities throughout Florida and is
usually addressed through a stormwater treatment retrofit program. Under current regulatory guidelines
for most of the existing development within the City has essentially no regulatory requirements for
stormwater treatment on the state and federal level. The only exception is industrial sites which are
expected to meet the Nonpoint Pollution Discharge Elimination System (NPDES) requirements under
U.S. EPA's and FDEP's regulatory programs. There is also a possibility of future NPDES requirements
for municipalities if new legislation is passed under the federal Clean Water Act (regarding cities with
populations of less than 100,000 persons).

In recognition of a lack of stormwater treatment controls for existing development, it is also
important to recognize the overall impact of the urban development on Quincy Creek. To demonstrate
this effect, some simple mixing calculations were performed to represent the effect of stormwater
discharging from the City's urban area (Station S283) into Quincy Creek downstream of the City's water
treatment plant intake (Station S286). The mixing calculations were performed for parameters which
exceeded Class III water standards. For the purpose of this calculation, the wastewater treatment plant
which is downstream (S286) was assumed to be off-line. The results indicate that the mix of the cleaner
Quincy Creek discharges with the poorer quality water from Tanyard Branch would have only slightly
exceeded the Class III criteria for zinc on one occasion. Of course, this dilution effect does not result in
lower concentrations in Tanyard Branch or reduced mass loading which are desirable with respect to the
cumulative effects of nutrient loading into the Ochlockonee River and Lake Talquin.

For new development or redevelopment, the F.A.C. 17-25 regulations for stormwater treatment
are in affect. This rule provides for some exceptions such as individual homesites but requires treatment
for almost all other types of development or redevelopment within the City. Since this rule is already
included in the City's land development code, this alternative is currently in place. This regulatory
program requires active involvement by the FDEP but only minimal effort on the part of the City to
enforce. For the purpose of this study it is considered the least cost alternative for stormwater treatment.

Although the scope of this study did not include the financial aspects for stormwater
management, the only other alternative considered within City limits was a more proactive program which
would require a long-term funding mechanism. Such a program would require the City to build regional
retrofit facilities now and require redevelopment or future development to pay for discharge into these
facilities in the future to meet the F.A.C. 17-25 stormwater treatment requirements. The advantages of
such a program are that small on-site treatment facilities would not have to be built for every new
development or redevelopment and treatment for areas currently developed could begin immediately in a
retroactive fashion. Also there is an economy of scale for regional facilities with regard to construction
and maintenance costs. In order to implement such a program, the City would also have to establish a
system that would provide treatment credits to private land owners in a manner that is acceptable to the
FDEP.











Stormwater Quality Alternatives Analysis


Stormwater alternatives for water quality improvements in this plan fall into three categories as
follows:

1. Urban Runoff Pollution controls alternatives within City limits;
2. Water treatment plant alternatives; and
3. Stormwater monitoring alternatives.


Urban Runoff Pollution Control Alternatives

Within the City's urban services area it is very clear that the most significant problem concerning
pollutant loading to streams is the existing land use condition rather than the net change in land use due
to future growth. This is a common problem in well established communities throughout Florida and is
usually addressed through a stormwater treatment retrofit program. Under current regulatory guidelines
for most of the existing development within the City has essentially no regulatory requirements for
stormwater treatment on the state and federal level. The only exception is industrial sites which are
expected to meet the Nonpoint Pollution Discharge Elimination System (NPDES) requirements under
U.S. EPA's and FDEP's regulatory programs. There is also a possibility of future NPDES requirements
for municipalities if new legislation is passed under the federal Clean Water Act (regarding cities with
populations of less than 100,000 persons).

In recognition of a lack of stormwater treatment controls for existing development, it is also
important to recognize the overall impact of the urban development on Quincy Creek. To demonstrate
this effect, some simple mixing calculations were performed to represent the effect of stormwater
discharging from the City's urban area (Station S283) into Quincy Creek downstream of the City's water
treatment plant intake (Station S286). The mixing calculations were performed for parameters which
exceeded Class III water standards. For the purpose of this calculation, the wastewater treatment plant
which is downstream (S286) was assumed to be off-line. The results indicate that the mix of the cleaner
Quincy Creek discharges with the poorer quality water from Tanyard Branch would have only slightly
exceeded the Class III criteria for zinc on one occasion. Of course, this dilution effect does not result in
lower concentrations in Tanyard Branch or reduced mass loading which are desirable with respect to the
cumulative effects of nutrient loading into the Ochlockonee River and Lake Talquin.

For new development or redevelopment, the F.A.C. 17-25 regulations for stormwater treatment
are in affect. This rule provides for some exceptions such as individual homesites but requires treatment
for almost all other types of development or redevelopment within the City. Since this rule is already
included in the City's land development code, this alternative is currently in place. This regulatory
program requires active involvement by the FDEP but only minimal effort on the part of the City to
enforce. For the purpose of this study it is considered the least cost alternative for stormwater treatment.

Although the scope of this study did not include the financial aspects for stormwater
management, the only other alternative considered within City limits was a more proactive program which
would require a long-term funding mechanism. Such a program would require the City to build regional
retrofit facilities now and require redevelopment or future development to pay for discharge into these
facilities in the future to meet the F.A.C. 17-25 stormwater treatment requirements. The advantages of
such a program are that small on-site treatment facilities would not have to be built for every new
development or redevelopment and treatment for areas currently developed could begin immediately in a
retroactive fashion. Also there is an economy of scale for regional facilities with regard to construction
and maintenance costs. In order to implement such a program, the City would also have to establish a
system that would provide treatment credits to private land owners in a manner that is acceptable to the
FDEP.









It is recommended that this alternative be further explored through a detailed analysis of funding
mechanisms such as a stormwater utility fee for existing users of the stormwater management system or
new development/redevelopment impact fees. Other considerations for this alternative are development
of regional facilities which are attractive community features and serve a dual purpose such as a flood
control facility or a park for passive recreation. In addition to funding, this alternative would also require a
facility location study, cost estimates, detailed engineering designs, permitting, and construction.


Alternatives for Improving the Quality of Raw Water Supplies

The analysis of alternatives of the surface water used to supply raw water for the City's drinking
water requires both quantity and quality considerations. Historically, the City has had a dependable
supply of surface water from Quincy Creek. The withdrawal point on Quincy Creek has also been
conveniently located very near the water supply facility. The main problem has been high turbidity during
high flow periods or intermittently after storm events. This problem increases treatment costs and also
causes the plant operations to be temporarily shut down. Groundwater, which is of limited supply and
quality, is used during these periods as a backup supply. Although a detailed analysis of the water
supply system operations was beyond the scope of this study it is expected that these surface water
quality problems are costly with respect to the treatment plant operations and the general public
(consumers) over the long-term. To mitigate these problems, three basic types of stormwater
management alternatives were considered as follows:

1. Nonstructural
2. Treat stormwater discharges prior to the plant intake
3. Move the treatment plant intakes.

Alternative one is to some extent already in place in the form of state and federal regulatory
programs related to land clearing practices and stormwater industrial discharges. Stricter regulatory and
enforcement programs for erosion and turbidity controls in the basin area upstream of the plant uptake
would probably require greater participation on the part of local governments to develop their own set of
standards for best management practices (BMP's) and stormwater controls or enforcement programs.
Since most of the upper basin is outside City limits some of the financial burden for developing and
implementing such programs would fall upon the County. At a minimum this would probably require
some form of an agreement between the City and County. The main drawback of an enhanced
regulatory program is that it is not clear that such a program would result in a net improvement in water
quality. Historical water quality data for Quincy Creek do not show any trends towards improved surface
water supplies, with respect to treatment plant operations, in spite of existing regulations.

Land use controls are another nonstructural consideration. Land use controls would not
immediately solve the turbidity problems in Quincy Creek but may be highly effective for future
development. It is highly recommended that future development within the Upper Quincy Creek and
Colson Creek watershed be given the greatest amount of attention to preserve the existing quality of
surface water supplies. Examples of land use controls that can be effective include limits on unpaved
roads, creation of preservation or conservation buffer areas, reduced housing densities, and limits to the
amount of cleared land within developable areas. Unfortunately most of the watershed area is outside
the City limits and the City has no direct control over growth or land use activities in this area.

Another nonstructural type alternative is road improvements. Paved roadways with wide grassed
swales near and along streams would be highly beneficial for reducing sediment discharges and other
pollutants to drainage ways and streams. This alternative could be very expensive if done solely for the
purpose of controlling turbidity but may be cost effective if done in conjunction with other County or City
paving programs. Without further monitoring data on the effects of paved and unpaved roads it is not
possible to quantify the actual effects of this alternative. One final nonstructural alternative is the
acquisition of land to protect various parcels of land from further development. This alternative may be
32







used in combination with other alternatives such as land use controls. It would be especially beneficial
for parcels which are subject to new development and soil disturbances which increase turbidity. The
long-term benefits of land acquisition program could be highly cost effective if done in conjunction with
state lands preservation programs. This alternative is to some extent limited because it depends on a
willingness of private property owners to offer their land for preservation purposes.

The second alternative involves the construction of a large reservoir or a series of reservoirs
capable of storing and treating all the stormwater from upper Quincy Creek watershed. Such a reservoir
would have to be designed to have a high removal efficiency for suspended solids. The reservoirs would
need to regulate flows and allow for lake drawdowns for maintenance. For the purposes of analyzing this
alternative, a lake with the same storage characteristics as Interlocking Lakes was added to SWMM for
the model node below subbasin 3. The model results indicated stream flows could be augmented to
meet supply demands. Based on data for lakes of similar size and inflow pollutant loads raw water
quality would also be improved. The main constraint of this alternative is the high cost of construction.
Depending on the site(s) chosen for pond construction there could also be environmental permitting
constraints.

The third and most promising alternative for improving the raw surface water supply was to
provide an alternative site for the treatment plant intakes. Based on the hydrologic model and the water
quality sampling results of this study there appears to be a sufficient supply of better quality water from
the Colson Creek Watershed. The water treatment plant intakes could be extended to withdraw water
from below Interlocking Lakes, taking advantage of the lake treatment effects and the apparently cleaner
water from this watershed. In order to go forward with this alternative, a few additional details will need to
be considered.

First, the monitoring data collected for evaluating this alternative only considered the quality of
the outflow from Interlocking Lakes and sampling was limited to only four events. Since water quality
data were not taken concurrently for the lake inflow and the lake itself it is assumed that the lake will
continue to provide treatment. It is possible that flow into the lake was a lot cleaner during the sample
periods. Conversely, if the quality into the lake was very poor the long-term treatment effect of the lake
would need to be evaluated. These questions can be readily answered through additional monitoring.

Second, the supply of water during drought periods is not expected to be as dependable on
Colson Creek as it is further downstream at the current intake. For the purpose of evaluating streamflow
reliability, flow duration curves were developed using the SWMM model to simulate long-term conditions
on Colson Creek. The period chosen for model analysis from 1974 to 1991 included the lowest daily
observed flows on record near the current intake at station S286. Using this period of record model
results could be compared to actual data at the current intake. For Colson Creek the model was run by
computing runoff and baseflows. The base flows used were the observed baseflows at S286 weighted
according to the ratio of the area within the Colson Creek watershed to the entire Quincy Creek
watershed above the gage at S286. A severe case condition was also run for Colson Creek assuming
that base flow into Interlocking Lakes was constant throughout the period of record at 3 cfs. Both cases
for Colson Creek were also considered without the lake to determine the streamflow augmentation effects
caused by the lake.

The flow-duration analysis at S.R. 267 flow gauge (S286) includes an instream withdrawal
amount of 3.5 cfs. The flow-duration curve developed at this site with the model indicates that flows
exceed 2.5 cfs about 99.9 percent of the time. The model results for Colson Creek (S286) show that
without any withdrawals instream flows exceed an average daily flow of about 4 cfs (2.6 MGD) about 99.5
percent of the time It should be noted that further drawdown of the lake below the invert of the existing
outflow structure was not considered in this case. Thus, lake storage could possibly be used to further
augment low flows. In its current configuration, the lake apparently has very little effect on low flow
augmentation.









Even under severe drought cases, flow-duration curve analysis indicates instream flow of about 4
cfs exceeded about 50 percent of the time. Even if this hypothetical case was to occur it would still be
feasible to withdraw water from Colson Creek by installing a dual intake system. A dual intake system
would likely be recommended anyway to allow for withdrawals at the current location during low flow
periods. Water quality data collected at the current intake location indicates water quality is good under
low flow conditions.

The third factor to consider is cost effectiveness. This alternative is intended to reduce the long-
term treatment plant operating and materials (chemicals) costs. To quantify the costs savings, a detailed
engineering analysis is recommended to examine the annual plant expenditures that would result from
water quality improvements and the costs of extending an additional plant intake to Colson Creek. A firm
yield analysis which finds the most critical drought period and the optimal use of storage in a reservoir
would also be useful to determine if there is any need to improve the design of the lake outfall structure.
Additional cost savings and secondary benefits are those associated with improvement of the public
water supply in terms of reduced odor, better taste and appearance, and reduced staining problems.


Stormwater Quality Monitoring Alternatives

Water quality monitoring is an additional component of most stormwater management programs
which are used to audit the success of stormwater management system improvements, adjust or develop
new pollution controls, and to detect future problems which may require an additional course of action.
The most pressing monitoring need is that related to the City's water supply. Concurrent analyses of the
Colson Creek inflows and outflows of Interlocking Lakes are needed to further evaluate the water supply
potential of this watershed and the long-term treatment effect of the lake. The existing Colson Creek
station, S284, and two new stations, one on the lake and one at the lake inflow would be needed for this
purpose. Iron, Manganese, Solids, Nutrients, and Turbidity are the key parameters to sample for.
Monitoring of the lake inflows is also important to establish a monitoring baseline to evaluate future land
use and detect any watershed activities which may have an impact on the quality of raw water supplies.
The baseline data will also help to determine how important it is to preserve the watershed area above
the lake.

The Upper Quincy Creek watershed could also be monitored more closely to determine where
water quality violations for turbidity may be occurring. Field inspections as well as turbidity sampling
could be a useful monitoring approach to help identify key stormwater problem areas. Identification of
problem areas is essential before enforcement actions or remedial measures can take place. Additional
attention should be given to areas where new development or changes in land use are to occur. In view
of its expense and possible task overlapping with other state or federal agencies, it is suggested that the
City should seek assistance to monitor water quality in Quincy Creek upstream of the water treatment
plant to determine source and severity of water quality violations.

Additional monitoring that would provide useful information would be that which confirms the
mixing calculations downstream of Tanyard Branch. This would require an additional monitoring station
east of the City on Quincy Creek. However this type of monitoring is not recommended until the
wastewater treatment plant discharges to Quincy Creek cease. The treatment plant discharges would
tend to mask the overall effects of the projected water quality improvements. Additional monitoring on
Tanyard Branch would be recommended if new facilities are built to treat the urban runoff.




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