UNITED STATES .
o DEPARTMENT OF THE INTERIOR 19
FEBE 1970 1
N ch 3,^ GEOLOGICAL SURVEY
Water Resources Division U V i
500 Zack Street "
Tampa, Florida 33602
Feb. 2, 1970
Mr. L. M. Blain
Gibbons, Tucker, McEwen, Smith, Cofer & Taub
Attorneys at Law
606 Madison Street
Re: Southwest Florida Water Management District
Establishment of Mean Low Level for Ground Water
Attached herewith are my comments with respect to your memorandum covering
the above subject matter. These comments deal chiefly with items 5 to 10
and are made to reemphasize some of the technical problems involved. These
problems should be clearly understood so that procedures can be reasonably
adjusted with a minimum of conflict. Hopeful, additional discussions
will provide suggestions that will permit simplification of procedures
so that they do not become too cumbersome with respect to administration,
compliance, and enforcement.
J. S. Rosenshein
cc: Dale Twachtmann, Executive Director, Southwest Florida Water Management
Garald Parker, Chief Hydrologist, Southwest Florida Water Management
C. S. Conover, District Chief, U. S. Geological Survey
Item 5 Amount of drawdown at a well field perimeter will depend upon
at least the following variables: (1) hydraulic characteristics of the
aquifer and associated beds (transmissivity, storage coefficient, vertical
leakage, etc,); (2) distance of the pumping center from the observation
point; and (3) interference of other pumping wells on the perimeter observa-
tion well. Therefore, adoption of a constant figure to apply to all well
fields is not necessarily the most realistic hydrologic approach. My
impression of what is written under this item may not be what you actually
mean with respect to "constant".
Item 6 Not only should the key base wells not be affected by pumpage
from a proposed well field but, within reason, not be affected by any
nearby wells or well fields pumping sizeable quantities of water. If this
second hydrologic condition cannot be effectively met,this item will
A procedure should be built in so that key base wells can be changed
because of significant alteration of hydrologic conditions existing in the
vicinity of the base well owing to man's activity.
Item 7 Could be revised so that the item is dependent on determination
of daily low level at the end of the month in each key base well.
Item 8 Should change this to record "drawdown is then added to the monthly
Item 9 Believe what is meant is the following: the daily low water level
for each day in month is to be averaged to produce average monthly low in
the observation well.
Item 10 Note mean low level is measured from land surface down to water-
surface. Allowable drawdown should, therefore, be added to adjusted
reference base instead of being subtracted. This correction would change
calculated mean low level of P.S. to 17.9' m.s.l. not 11.9' m.s.l.
Note: Under calculations need several days lag time between end of
proceeding month and Chief Hydrologist announcement of average lows for
key base wells to allow for record collection and processing.