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Title: Independent cost analysis of porous groin installations at Eglin Air Force Base, Florida
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Title: Independent cost analysis of porous groin installations at Eglin Air Force Base, Florida
Series Title: Independent cost analysis of porous groin installations at Eglin Air Force Base, Florida
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Table of Contents
    Half Title
        Half Title
    Title Page
        Title Page
    Table of Contents
        Page i
        Page ii
        Page iii
    Executive summary
        Page iv
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Selected photographs of the Eglin Air Force Base installations
        Page A-1
        Page A-2
        Page A-3
        Page A-4
        Page A-5
        Page A-6
        Page A-7
        Page A-8
        Page A-9
Full Text




UFL/COEL-2003/007


INDEPENDENT COST ANALYSIS OF POROUS GROIN
INSTALLATIONS AT EGLIN AIR FORCE BASE, FLORIDA

FINAL REPORT






by



Robert G. Dean
and
Subarna Malakar


Prepared For:

Bureau of Beaches and Wetland Resources
Marjorie Stoneman Douglas Building
3900 Commonwealth Boulevard
Tallahassee, FL 32399-3000


July 10, 2003









INDEPENDENT COST ANALYSIS
OF POROUS GROIN INSTALLATIONS
AT EGLIN AIR FORCE BASE, FLORIDA
(FINAL REPORT)




July 10, 2003







Prepared For:

Bureau of Beaches and Wetland Resources
Marjorie Stoneman Douglas Building
3900 Commonwealth Boulevard
Tallahassee, FL 32399-3000







Prepared By:

Robert G. Dean and Subarna Malakar
Department of Civil and Coastal Engineering
University of Florida
Gainesville, FL 32611








TABLE OF CONTENTS

EXECUTIVE SUMMARY ........................... .......................... ii

1.0 INTRODUCTION ......... .................................................. 1

2.0 PHOTOGRAPHS ................... ............... .................... 2

3.0 ANALYSIS OF SURVEY DATA ........................... ..... .......4
3.1 Available Survey Data ................................................ 4
3.2 Analysis M methods ............................................................. 6
3.3 Shoreline Changes ........................... ......... ............. 6
3.4 Volume Changes ..................................................... 7
3.5 Site 1 Shoreline and Volume Changes ................................... 7
3.5.1 Site 1 Shoreline Changes ..................................... 7
3.5.2 Site 1 Volume Changes ......................................... 8
3.6 Site 2 Shoreline and Volume Changes ................... .... ......... 10
3.6.1 Site 2 Shoreline Changes ..................................... 10
3.6.2 Site 2 Volume Changes ...................................... 11

4.0 COST ANALYSIS ................ ........................................ 12

4.1 General Discussion .................................................12
4.2 Costs of the Porous Groin Installation ................... .... ......... 13
4.3 Rationale for Cost Comparisons ..................... ................ 13

5.0 SUMMARY AND CONCLUSIONS ........................................ 16

6.0 REFERENCES ................................... ....... ................ 17


LIST OF TABLES


Page

Table 1 Characteristics of Survey Data ............................................. 5

Table 2 Average Shoreline Change Characteristics .................................. 8

Table 3 Average Volume Change Characteristics ................................... 9

Table 4 Cost Information for PGS Installations at Sites 1 and 2 ........................ 14








LIST OF TABLES (Continued)

Table 5 Development of Unit Costs of Sand Accumulated ............................ 15

Table 6 Comparison of Costs of Sand by Conventional Methods and by PGS ............. 16

LIST OF FIGURES
Page
Figure 1. Location Map for Two Installation Sites .................................. 1

Figure 2. Aerial Photograph Looking East With Site 2 in Foreground. Destin Pass in
Background. Photograph by Benedict Engineering, March 6, 2001 ....................... 2

Figure 3. Aerial Photograph of Site 1, Looking East. Photograph by Benedict Engineering,
March 6, 2001 .............................................................. 3

Figure 4. Aerial Photograph of Site 2, Looking West. Photograph by Benedict Engineering,
March 6, 2001 .............................................................. 3

Figure 5. Schematic of Porous Groin Installation ............... .................... 4

Figure 6. Illustrating Case in Which More Than One NGVD Shoreline Exists ............. .6

Figure 7. Average Shoreline Changes Inside and Adjacent to the Porous Groin System. Site 1 7

Figure 8. Average Volume Changes Inside and Adjacent to the Porous Groin System. Site 1 .. 9

Figure 9. Average Shoreline Changes Inside and Adjacent to the Porous Groin. System. Site 2 10

Figure 10. Average Volume Changes Inside and Adjacent to the Porous Groin System. Site 2 11

Figure A.1. Aerial Photograph Looking East With Site 2 in Foreground. Destin Pass in
Background. Photograph by Benedict Engineering, March 6, 2001 ................... A -2

Figure A.2. Aerial Photograph Looking East With Site 1 in Foreground. Destin Pass in
Background. Photograph by Benedict Engineering, March 6, 2001 .................... A-3

Figure A.3. Aerial Photograph of Site 2, Looking East. Photograph by Benedict Engineering,
March6,2001 ........................................................ A-3

Figure A.4. Site 2, Looking West, December 5, 2000.
Photography by Benedict Engineering ....................................... A-4








LIST OF FIGURES (Continued)

Figure A.5. Site 2, Looking West, December 14, 2000.
Photography by Benedict Engineering ........................................ A 4

Figure A.6. Site 2, Looking East, Photograph Taken on March 22, 2001 by FDEP ...... A 5

Figure A.7. Site 2, Looking West, Photograph Taken on May 14, 2001 by FDEP ....... A 5

Figure A.8. Site 2, Looking East, Photograph Taken on May 14, 2001 by FDEP ........ A 6

Figure A.9. View of Configuration of Porous Groins at Site 2. Photograph
TakenMay 14,2001by FDEP ............................................... A-6

Figure A.10. Site 2, Looking East, Photograph Taken August 16, 2001 by FDEP.
Tropical Storm Barry Made Landfall at Destin on August 6, 2001 ................... A 7

Figure A.11. Site 2, Looking West, Photograph Taken August 16, 2001 by FDEP.
Tropical Storm Barry Made Landfall at Destin on August 6, 2001 ................... A 7

Figure A.12. View Looking East as Site 2.
Photograph Taken by PBS&J on October 25, 2001 .............................. A- 8

Figure A.13. View Looking West as Site 2.
Photograph Taken by PBS&J on October 25, 2001 ............................... A- 8

Figure A.14. Site 2. Looking East, Photograph Taken in December 2001 .............. A 9

Figure A.15. Site 2. Looking West, Photograph Taken in December 2001 ............. A 9









EXECUTIVE SUMMARY

This report presents an analysis of shoreline and volume changes at the two Porous Groin
System (PGS) installation sites on Eglin Air Force property in western Florida and a cost
comparison of the PGS methodology and more conventional nourishment methodology. The
groins were installed at two sites. Site 1 was located at the Eglin Air Force Beach Club and
Site 2 is at a radar base some two miles west of Site 1. The PGSs were installed in November
2000 and the system was removed from Site 1 in April 2001 and removed from Site 2 in
March 2002. A total of sixteen surveys are available commencing in December 2000 and
extending to November 2002. The porous groin installations consisted of sixteen shore
perpendicular groins, spaced at 100 feet, thereby occupying a longshore length of 1,500 feet.
The total surveyed longshore length was 3,600 feet at each site including a longshore length of
1,050 feet on either side of each set of PGS. The areas adjacent to the groins serve as
"controls" for comparison purposes.

The shorelines and volume changes were averaged over the 1,500 feet longshore length of the
PGS installation and the 150 feet length of the individual groins. These results are compared
with corresponding quantities in the adjacent control areas.

The data suggest that the PGSs were installed when the beaches were in an eroded condition
as the shorelines and volumes generally increased both within and adjacent to the groins
during the surveyed period. Comparison of the average shoreline and volume changes did not
reveal a strong, clearly identifiable effect of the groins with the increases within the groin field
at some locations and times being greater than in the control areas and in other locations or
times, less. Rather, the comparison was more indicative of irregular shoreline and volume
changes superposed on natural seasonal shoreline and volume changes. Thus, on this basis, it
is difficult to attribute a volume gain or loss to the PGS. Three volume increase bases were
adopted with the most generous being the average increase within the groin limits irrespective
of those in adjacent areas.

Costs for nourishment were based on trucking since, by any definition, volume increases
within the groin field were small and would not justify mobilization of a dredge. A range of
trucking costs from $ 12.00 per cubic yard to $ 15.00 per cubic yard was considered. Several
costs for the installations had been developed by others and were employed herein. Using the
most generous definition of the volume increases, the costs of truck haul nourishment were
less than those for the PGS. Additionally, in evaluating these results, it should be recalled that
truck haul introduces additional sediment into the nearshore system whereas a PGS
installation can, at best, simply rearrange the sediment residing within the active nearshore
system.







INDEPENDENT COST ANALYSIS
OF POROUS GROIN INSTALLATIONS
AT EGLIN AIR FORCE BASE, FLORIDA
(FINAL REPORT)

1.0 INTRODUCTION
This report completes the data analysis and cost evaluation of the two porous groin installations
at Eglin Air Force Base, FL. The two sites are located as shown in Figure 1 and include Site 1
which was located at the Eglin Air Force Base Beach Club and Site 2 located at a radar site
approximately 2 miles west of Site 1. These porous groin systems (PGS) were installed in
November 2000 and removed at Site 1 on April 27, 2001 and removed at Site 2 in early March
2002. A previous interim report has been published by Dean and Malakar (2001).
The purpose of the present report is to present: (1) An updated analysis of the survey data, and
(2) The results of a cost analysis comparing the PGS with more conventional approaches in
which sand is added to the system through beach nourishment which could be by either truck
haul or dredging.


1 J


Choctawhatchee Bay

0 5,000
Scale (ft)


Destin


Site 2


Site 1


Figure 1. Location Map For Two Installation Sites.








2.0 PHOTOGRAPHS


Photographs can provide qualitative information useful in supplementing the analysis results of
the survey data. Figure 2 is an aerial photograph looking east with Site 2 in the immediate
foreground. Figures 3 and 4 show Sites 1 and 2 respectively. Appendix A presents a series of
photographs depicting the site conditions at various times.


Figure 2. Aerial Photograph Looking East With Site 2 in
Foreground. Destin Pass in Background. Photograph by
Benedict Engineering, March 6, 2001.





























Figure 3. Aerial Photograph of Site 1, Looking East. Photograph by Benedict
Engineering, March 6, 2001.


.01 45 i

Figure 4. Aerial Photograph of Site 2, Looking West. Photograph by Benedict
Engineering, March 6, 2001.








3.0 ANALYSIS OF SURVEY DATA


This section presents the results of the survey data analysis and will be used in the second major
task which is the cost comparison.

3.1 Available Survey Data

Table 1 summarizes the available survey data. It is seen that a total of 16 surveys were conducted
with some of these surveys encompassing both sites and others only one site. The PGS consisted
of 16 groins at each site and occupied an alongshore length of 1,500 feet and the surveys
included this region and extended 1,050 feet on either side of the groins for a total surveyed
length of 3,600 feet. The 1,050 sections on either side of the groin are considered here as "control
regions", which on average, are not affected by the groin installation. Figure 5 presents a
schematic of the installations. Each porous groin is 150 feet long.



4 3,600 Feet Surveyed Area

J,050 Feet Westl 1.500 Feet Consisting lJ,050 Feet East,
control Area of 16 Porous Groins -'Control Area


--11------------








Figure 5. Schematic of Porous Groin Installation.

It is seen from Table 1 that the number of profiles surveyed during the various surveys ranged
from 21 to 43. The method of analysis employed in the previous report (Dean and Malakar,
2001) required use of the same profile lines for comparison. For purposes here, all 16 surveys
were analyzed by a method that did not require the use of common lines for all surveys. In some
cases, the profile lines extended gulfward a shorter distance than 300 feet, the nominal distance
to which profile lines had been analyzed in previous reports. These profiles were extended
approximately and analyzed in the cross-shore distance to 300 feet; however, the confidence in
the results is reduced due to the lack of adequate survey data. Therefore, the cross-shore analyses
are only presented for the 150 foot length encompassed by the groins.









Table 1


Characteristics of Survey Data


Survey Date Survey Purpose Sites Surveyed Number of Profiles Surveyed
December 2000 Pre-Installation Sites 1 and 2 Site 1: 42; Site 2:42
January 2001 Document Changes Sites 1 and 2 Site 1: 43; Site 2:43
February 2001 Document Changes Sites 1 and 2 Site 1: 42; Site 2:42
April 2001 Document Changes Sites 1 and 2 Site 1: 33; Site 2:33
July 2001 Document Changes Sites 1 and 2 Site 1: 42; Site 2:42
August 2001 Document Changes Site 2 Only Site 2:43
October 2001 Document Changes Sites 1 and 2 Site 1: 43; Site 2:43
March 2002 Document Changes Site 2 Only Site 2:43
April 2002 Document Changes Site 2 Only Site 2:43
May 2002 Document Changes Site 2 Only Site 2:33
June 2002 Document Changes Site 2 Only Site 2:21
July 2002 Document Changes Site 2 Only Site 2:21
August 2002 Document Changes Site 2 Only Site 2:33
September 2002 Document Changes Site 2 Only Site 2:21
October 2002 Document Changes Site 2 Only Site 2:21
November 2002 Document Changes Site 2 Only Site 2:32








3.2 Analysis Methods


As noted, a previous report (Dean and Malakar, 2001) relating to the porous groin installations
at Eglin Air Force Base has presented analysis results including shoreline and volume changes
and the patterns of these changes. The patterns can assist in determining the processes that
caused the shoreline and volume changes, in particular the differential effect in the installation
areas as compared to the adjacent shorelines. Because the purpose of the present report is to
establish overall performance of the installations at the two sites, the emphasis will be on total
volume and shoreline changes inside and adjacent to the regions occupied by the porous groin
systems. As noted, this allows use of more of the survey data than was possible for the study of
patterns of changes. Thus, the patterns of shoreline and volumetric change are not the focus here
and are not presented in this report. Common to both shoreline and volume changes, the analysis
determined the averages within the 1,500 feet shoreline segment encompassed by the nets and the
2,100 feet segment adjacent to the nets. The volume changes accounted for the 150 feet lengths
(perpendicular to the shoreline) of the individual groins. In the control areas, the volumes were
computed over the Gulfward 150 feet from the baseline.

3.3 Shoreline Changes

The shoreline changes are based on NGVD elevations. In some cases, a bar was present which
resulted in multiple locations of this shoreline as shown in Figure 6. A limited comparison (12
surveys) of shoreline changes was conducted for the most gulfward and the most landward
shoreline positions. It was found that the average of the most gulfward positions could be
significantly greater than the average most landward shoreline positions. However, the overall
average within groin field shoreline changes minus adjacent average control shoreline changes
was within 5.1 feet for the most landward and seaward shoreline positions. Therefore the results
presented here are based on the more landward shoreline positions. Shoreline changes were
determined by subtracting the shorelines for the December survey from the shorelines for each
subsequent survey being considered


Most Shoreward NGVD Shoreline
F r --Most Seaward NGVD Shoreline
NGVD Elevation



Bar


Figure 6. Illustrating Case in Which More Than One NGVD Shoreline Exists.









3.4 Volume Changes

As noted, the average volume changes were determined within: (1) The 1,500 feet longshore and
the 150 feet cross-shore dimension of the groin field, and (2) The 2,100 feet longshore dimension
of the control areas and a cross-shore distance of 150 feet from the baseline. Volume changes
were determined by subtracting the volumes for the December survey from the volume for each
subsequent survey being considered.

Shoreline and volume change results are presented in the following sections.

3.5 Site 1 Shoreline and Volume Changes

3.5.1 Site 1 Shoreline Changes

The average shoreline positions within the 1500 feet longshore distance of the groin field and
within the 2,100 feet longshore distance of the adjacent control areas are presented for Site 1 in
Figure 7 over the period of surveys at Site 1. It is seen that the average shorelines both inside the
limits of the groin fields and in the adjacent control areas increased after installation with the
shorelines inside the groin field generally increasing more than outside the groin field. The
average shoreline inside the groin commenced retreating prior to removal of the groins and the
shorelines inside and outside of the groin field continued to decrease after groin removal.


60

S50
U,
0) 40
r_
C
o 30

S20
0
C) 10
a,
0)
E2 o
()


0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Years After Installation

Figure 7. Average Shoreline Changes Inside and Adjacent to the Porous
Groin. Site 1.


.......... : .. . . ... ... .


** **- --- |- --| -- -i- -- ^ |- | -i -| - -i '-- r j- - i
.... ..... .. ... ...g .... .... ... .... .. . ...... ..... .... ....... ....|. ...


.... ...... .... .... ..... .. ...... .....; .. .. ............. .... ............ ............ ..j....
..........



: ''..Inside Groin Unmits






;............. ..... ..... ...... .........


-nL








In interpreting these overall shoreline changes with time, it appears that the PGS was installed
when the shoreline was in a recessed condition (November 2000). The generally close tracking of
the two average shorelines suggests that the changes were due primarily to natural effects and not
to the groins although at one time (February 2001), the average shoreline inside the groin field
had advanced 20 feet more than the average shoreline adjacent to the groin field.

Table 2 presents the time averaged shoreline change results including the changes inside the
groin field and outside the groin field (2,100 foot control area) over the period of groin
installation and the average at the time of groin removal. For Site 1, it is seen that the averages
over the period of installation are 20.1 feet and 14.9 feet advancement within and outside of the
groin limits, respectively. At the time of removal, the averages are 21.9 feet advancement both
within and outside of the groin limits.
Table 2

Average Shoreline Change Characteristics


Average Shoreline Change Over Average Shoreline Change at Time
Period of Installation of Groin Removal
(feet) (feet)
Site
Within Groin Within Control Within Groin Within Control
Field Areas Field Areas

1 20.1 14.9 21.9 21.9

2 30.4 22.8 47.7 20.0

3.5.2 Site 1 Volume Changes

The Site 1 volume changes, presented in Figure 8, parallel to some degree the shoreline changes
at this site and are suggestive of a seasonal cycle with the volumes within the groin field
increasing in the summer season and decreasing (sediment moving seaward of the 150 feet cross-
shore dimension of the groins) in the winter season. In this case, the volume increases outside the
groin field were generally slightly greater than within the 1,500 feet occupied by the groin field.

Table 3 presents the time averaged volume change results including the changes inside the groin
field and adjacent areas (2,100 foot control area) over the period of installation and the average
at the time of groin removal. For Site 1, it is seen that the averages over the period of installation
are 4.6 yd3/foot and 5.0 yd3/foot increase within and outside of the groin limits, respectively. At
the time of removal, the averages are increases of 6.4 yd3/foot and 9.7 yd3/foot within and
outside of the groin limits, respectively.








16
.................. ................ .......
1 4 ... .......... .... ...... ......
V,:: : i
) M ......................... ..... ............... ....

S 2 .... ....................... ....................................... ......................
19 .. .................... ........~.. .





-2






0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.
Figure 8. Average Volume Changes Inside and Adjacent to the Porouside Groin LiSystem.its
S....S ite 1..... ...... .... ...... ..... ....... ........................... .....
a) 4 .6 -- .... ..... .... ................. ..... ..........
0 5 .. ..... . ...... .... .... ... .. .. .. ... I ... . . .. .. ... ...... ......... .........
-2 ; i . . ; . I.




0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.
Years After Installation
Figure 8. Average Volume Changes Inside and Adjacent to the Porous Groin System.
Site 1.


Table 3

Average Volume Change Characteristics


Average Volume Change Over Average Volume Change at Time of
Period of Installation Groin Removal
(yd3/foot) (yd3/foot)
Site
Within Groin Within Control Within Groin Within Control
Field Areas Field Areas

1 4.6 5.0 6.4 9.7
2 4.8 10.0 7.5 8.4









3.6 Site 2 Shoreline and Volume Changes

3.6.1 Site 2 Shoreline Changes

The Site 2 shoreline change results are presented in Figure 9. The results are quite irregular with
the shoreline inside the groin field advancing more than that outside for the first two months, but
for the next seven months, the shoreline outside the groin field was more advanced, followed by
the remaining six months of groin installation during which the average shoreline inside the groin
field remained more advanced than outside the groin field. Also, of interest, the shoreline
generally continued to advance even after removal of the groins with average advancement
greater within the (previous) limits of the groin field than outside.


100



' 80
V)
0)
C
S 60
0
a)





a) 20



< 0


!n i


,-)


0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Years After Installation

Figure 9. Average Shoreline Changes Inside and Adjacent to the Porous Groin System. Site 2.









10


w i
S....... ......... ............... I
Inside Groin Limits .
.......... Outside Groin Limits

*N






i ;: . .... :. .
---- : ,



. ......... .:....'".


... .... ................ .. ..........









Table 2 has presented the average shoreline change results including the changes inside the groin
field and outside the groin field (2,100 foot control area) over the period of installation and the
average at the time of groin removal. For Site 2, it is seen that the averages over the period of
installation are 30.4 feet and 22.8 feet advancement within and adjacent to the groin field,
respectively. At the time of removal, the averages are 47.7 and 20.0 feet advancement within and
adjacent to the groin limits, respectively.

3.6.2 Site 2 Volume Changes

The volume change results for Site 2 are presented as Figure 10 and differ somewhat from the
shoreline change results (Figure 9). It is seen that the volumes generally increased both inside
and outside of the groin field with the volumes outside the groin field being greater than inside
the groin field, although the two volume changes start to converge before the groin removal in
March 2002. Subsequent to groin removal, both volume changes were approximately the same,
increasing from March 2001 to July 2001 and then decreasing, consistent with natural seasonal
changes.


414

C')
>'12

cr,
C 10

08
cil

E
2 6
0



2

0


... . . . . . . .. :. . . . . . . . . . ... . .. .... .... .. . . .. .


. -. . ... : .... ,- ... ..... ... .. ... .. ,.* ...: ..... .... . ...... .. . ..... . . -. .. .. .. .......
S..... .............






-. ^ .........: ...I ... ... ... .....I.. .is
..... .. .... .......... .. .... ... .... .



............. .. ................... .. .......... ....






Outside Groin Limits
K............... ........ ................
`''''"'''''''''''''"'''''''......... Outside Groin Limits''''"''~


-2
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.(
Years After Installation

Figure 10. Average Volume Changes Within and Adjacent to the Porous Groin System.
Site 2








In interpreting these results, it is difficult to identify conclusively an effect of the groin field. It
appears that most of the relative differences within and adjacent to the groin field are due to
natural changes in the system and the strongest case that can be made is for the changes being a
result of noise in the natural system combined with the seasonal effects. As discussed in previous
reporting of the survey results of this project, this general shoreline is known to be "noisy", that
is there are substantial natural undulations or oscillations of the shoreline and the differences in
Figure 10 are most likely dominantly due to these natural effects with any effects due to the groin
field being secondary. Aerial photographs (Figures 2 and 4) confirm that the Site 2 groin
installation area coincided with an erosional "trough" in the beach planform. Nevertheless, in this
case, the groin system was unable to stabilize the shoreline against these natural forces.

Table 3 has presented the average volume change results including the changes inside the groin
field and adjacent to the groin field (2,100 foot control area) over the period of installation and
the average at the time of groin removal. For Site 2, it is seen that the averages over the period of
installation are 4.8 yd3/foot and 10.0 yd3/foot increase within and outside of the groin limits,
respectively. At the time of removal, the averages are increases of 7.5 yd3/foot and 8.4 yd3/foot
within and outside of the groin limits, respectively.

4.0 COST ANALYSIS

4.1 General Discussion

In developing an appropriate basis for a cost analysis and comparison with the more conventional
methods discussed earlier, it is necessary to consider the processes induced by the porous groins
which could be considered appropriate for crediting the porous groin system with volume and/or
shoreline changes.

Beach nourishment, whether by dredge, truck haul, or other means adds sediment to the active
nearshore system from outside this system. The seaward limit of this active portion of the
nearshore system is usually defined approximately in terms of this closure depth and thus efforts
are made during nourishment operations to not remove sand from areas landward of this depth
limit. Otherwise, the sand will tend to return to the area from which it is removed. Estimates of
the closure depth have been developed for the Florida peninsula and, for the Florida Panhandle
areas are on the order of 13 to 17 feet (Dean and Grant, 1989). By contrast, any sand accumulated
within the PGS is removed from the active system and thus, this can be considered as a zero sum
process. Therefore, considerations of the cost effectiveness should recognize this difference
between beach nourishment which adds "new" sand to the system and a groin system which
sequesters sand from the active system. One could argue that dredging sand from seaward of the
closure depth isn't really adding new sand to the system and that over a very long time frame
(many decades to centuries) some of the nourishment sand will return to the deepened borrow
areas. However, it is the differences in degree of sediment transport activity in the areas from
which the sand was removed and the time frames for the sand to return that differs markedly for
these two methods of addressing local beach erosion.








The claim of the proponents of the porous groin system is that any sand deposited within the
groin field originates from offshore and therefore does not diminish the sand volume in the
nearshore system. This claim cannot be supported based on nearshore coastal engineering or
coastal science knowledge or principles. In order for the system to draw sand from offshore, the
portion of the system from which the sand is drawn must be active by definition and thus if sand
is removed from this active area, this portion of the profile would remove sand from adjacent
portions of the profile where the groins are not present and thus, based on well-accepted and field
proven concepts of equilibrium beach profiles, those portions of the beach system where the
groins were not present would experience erosion. In sum, the beach system is interconnected
(geologists call it a "sand sharing system") and if sand is removed from one portion of the active
system, another part of this sand sharing system will experience an equivalent loss. Thus, even
allowing the most generous interpretation of the mechanics by which the porous groin system
functions, but still retaining well-established physical fundamentals of nearshore processes, the
system still functions as a groin as indicated by its designation "Porous Groin System".

With the previous paragraphs as background, in order to conduct cost comparisons at all, it is
necessary to attribute some volume gain to the porous groin system. Inspection of Figures 8 and
10 combined with the foregoing discussions does not support a finding that the system has
caused the accumulation of sand from any source. The original contention was that the system
would accumulate sand from offshore and would not remove sand from the active nearshore
system. Nevertheless, in order to continue with the goal of developing cost comparisons, three
bases for "crediting" the PGS for volumetric increases will be considered with the first being the
general difference between the volumetric accumulation per unit length of beach within the PGS
relative to the adjacent control area and the second, to consider the average volume changes
within the limits of the PGS over the period of installation without regard to the adjacent control
area. The third basis is the volumetric increase within the groin field at the time of the groin field
removal.

4.2 Costs of the Porous Groin Installations

Attempts were made to summarize the available cost information for the two Eglin porous groin
installations. These data were obtained from the Florida Department of Environmental Protection
and Benedict Engineering, Inc. and reflect best efforts to include all costs which could be
documented. Table 4 summarizes the available estimated and actual cost information.

4.3 Rationale for Cost Comparisons

As noted, there are two issues which arise in the selection of an appropriate basis for comparison
of costs of the porous groin installation versus the more traditional method of beach
nourishment: (1) The volume or shoreline "credit" that should be assigned to the groin
installation based on the results of the monitoring data, and (2) The costs which should be
considered in the cost comparison. The volume credit issue has been addressed in Section 4.1.
The rational for selecting each of the cost bases is discussed below.








The total costs for the porous groin installations, which were to some extent experimental,
obviously included engineering, development and monitoring costs that are unique to this type of
project. Engineering and monitoring costs are also associated with more traditional nourishment
methods. For purposes here, the four cost estimates presented in Table 4 excluding monitoring
and reporting costs will be used as a basis.

Table 4

Cost Information for PGS Installations at Sites 1 and 2

Estimate Type of Cost
Number
and Basis Engineering Monitoring Materials Labor Contingency Total
for Estimate $ and $ $ $ $
Reporting
$

Estimate 1 186,000 143,000 138,424 100,000 57,214 624,638
Estimated
Costs for 481,638*
Both Sites
(Original
Test Plan)'

Estimate 2 230,790 152,059 202,312 109,280 NA 694,440
Actual Costs
for Both 542,381"*
Sites*

Estimate 3 213,380 184,404 17,331 26,394 NA 441,509
Actual Costs
for Radar 257,105"
Site*

Estimate 4 166,900 96,900 35,235 60,725 NA 359,760
Projected
Costs for 262,860"
One Site*
SCost Estimates Provided by FDEP and Benedict Engineering.
"Excluding Monitoring and Reporting Costs








Table 5 presents a summary of the costs without monitoring and, the volume credit adopted, and
the resulting costs per cubic yard associated with the most generous acceptance of volume
accumulated by the PGS. The costs per cubic yard were calculated by dividing the costs in
Column 2 of Table 5 by the total PGS length (3,000 feet for two sites and 1,500 feet for one site).
The costs of trucking in small amounts of good quality sand will be taken as the range from
$ 12.00 per yd3 to $ 15.00 per yd3.

Table 5
Development of Unit Costs of Sand Accumulated

Costs Amount of Volume Costs per cubic yard
Based on Cost (Without Increase Attributable to ($)
Estimate Monitoring PGS
(See Table 4) Costs, See (yd3/foot)
Table 2)
Tae) Minimum Maximum Maximum Minimum
($)


1 481,638 Nil 7.5* Not Possible to
Two Sites. Total Calculate, Very 21.41
PGS Length = High
3,000 feet
2 542,381 Nil 7.5* Not Possible to
Two Sites. Total Calculate, Very 24.11
PGS Length = High
3,000 feet
3 257,105 Nil 7.5 Not Possible to 22.85
One Site. Total Calculate, Very
PGS Length = High
1,500 feet
4 262,860 Nil 7.5 Not Possible to 23.37
One Site. Total Calculate, Very
PGS Length = High
1,500 feet
Taken as the Maximum of Sites 1 and 2 in Table 3







Table 6 compares the range of trucking costs per cubic yard with those developed for the four
cost estimates for the PGS. It is seen that with the most generous interpretation of volume
accumulation by the PGS, trucking is still less expensive. Additionally, as noted earlier, trucking
adds "new" sand to the nearshore system.

Table 6

Comparison of Costs of Sand by Conventional Methods and by PGS

Based on Cost Trucking Nourishment Porous Groin Costs
Estimate Costs ($/yd3) ($/yd3)
(See Table 2)
Minimum Maximum Minimum Maximum

1 12.00 15.00 21.41 Not Possible to Calculate,
Very High

2 12.00 15.00 24.11 Not Possible to Calculate,
Very High

3 12.00 15.00 22.85 Not Possible to Calculate,
Very High

4 12.00 15.00 23.37 Not Possible to Calculate,
Very High


5.0 SUMMARY AND CONCLUSIONS

The monitoring data from the porous groin installation do not support the contention that the
porous groin system has had a measurable beneficial effect in terms of volume accumulation over
and above the control area which comprised the 1,050 feet segments immediately adjacent to and
on either side of the Site 1 and Site 2 Eglin Air Force Base PGS installations. As discussed in our
previous report (Dean and Malakar, 2001), this may be due, in part, to the well-known "noisy"
character of the shorelines in the Panhandle area of Florida. Regardless, even ascribing the most
generous volume increases to the PGS, the costs of sand accumulation by the PGS is still greater
than by trucking from an interior source. Three additional points worth noting are: (1) Even if the
PGS did trap sand, there is no supporting evidence that this sand did not originate from within
the nearshore active zone. In fact, all accepted coastal engineering and science knowledge
supports the position that this accumulated sand did originate within the active nearshore system
and, as for any other groin system, will cause a deficit elsewhere, (2) Nourishment is normally
carried out through accessing sand that is well outside of the normal active nearshore zone and
thus does not incur a deficit within the active nearshore zone, and (3) The maximum amounts
which could possibly be ascribed to the PGS are much smaller that those associated with a
substantial beach nourishment project which are on the order of 100 yd3/ft as compared to the
approximately 8 yd3/ft, which is the upper limit for the PGS.








6.0 REFERENCES


Dean, R. G. and J. Grant (1989) "Development of Methodology for Thirty-Year Shoreline
Projections in the Vicinity of Beach Nourishment Projects", UFL/COEL-89/026, Coastal and
Oceanographic Engineering, University of Florida, Gainesville, FL.

Dean, R. G. and S. Malakar (2001) "Independent Analysis of Porous Groin Installation at Eglin
Air Force Base, FL; Interim Report", UFL/COEL-2001/013, Civil and Coastal Engineering
Department, University of Florida, Gainesville, FL.








APPENDIX A

SELECTED PHOTOGRAPHS OF THE EGLIN AIR FORCE BASE INSTALLATIONS


A-1








A.1 Introduction


This appendix presents selected photographs of the porous groin installations at the two Eglin Air
Force Base sites. The first three photographs are the aerial photographs presented as Figures 2, 3
and 4 in the main body of this report. The remainder are ground views looking east and west
from the two sites, where such photographs are available.


Figure A.1. Aerial Photograph Looking East With Site 2 in
Foreground. Destin Pass in Background. Photograph by
Benedict Engineering, March 6, 2001.


A-2





























Figure A.2. Aerial Photograph of Site 1, Looking East. Photograph by Benedict
Engineering, March 6, 2001.


Figure A.3. Aerial Photograph of Site 2, Looking West. Photograph by Benedict
Engineering, March 6, 2001.


A-3




















j .- - K


Figure A.4. Site 2, Looking West, December 5, 2000. Photography by
Benedict Engineering.


Figure A.5. Site 2, Looking West, December 14, 2000. Photograph by
Benedict Engineering.


A-4


..,..,



























Figure A.6. Site 2. Looking East. Photograph Taken on March 22, 2001 by
FDEP.


Figure A.7. Site 2. Looking West. Photograph Taken May 14, 2001 by FDEP.


A-5




























Figure A.8. Site 2. Looking East, Photograph taken on May 14, 2001
by FDEP.


Figure A.9. View of Configuration of Porous Groins at Site 2.
Photograph Taken May 14, 2001 by FDEP.


A-6





























Figure A.10. Site 2. Looking East. Photograph Taken August 16, 2001 by
FDEP. Tropical Storm Barry Made Landfall at Destin on August 6, 2001.


Figure A. 11. Site 2. Looking West. Photograph Taken August 16,
2001 by FDEP. Tropical Storm Barry Made Landfall at Destin on
August 6, 2001.


A-7





























Figure A.12. View Looking East at Site 2. Photograph Taken by PBS&J
on October 25, 2001.


Figure A. 13. View Looking West at Site 2. Photograph Taken by PBS&J on
October 25, 2001.


A-8






























Figure A.14. Site 2. Looking East, Photograph Taken in December 2001.


Figure A.15. Site 2. Looking West, Photograph Taken in December 2001.


A-9




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