projects >
groundwater seepage in the florida
keys >
1998 proposal
Program: FRAGILE ENVIRONMENTS Project Justification:
The Florida Keys contain 25,000 septic tank systems, approximately 5,000
cesspools, and
1,000 class 5 injection wells. Depth of injection wells ranges from 10 to
30 m. Excessive algal
growth, coral diseases and both marine grass and sponge mortality is
perceived to be caused by
sewage nutrients leaking from groundwater on both sides of the Florida
Keys. Determining the
volume and composition of groundwaters seeping into the marine environment
from the sea floor is
vital to management decisions in the area. The data can be used for
I)planning future disposal
systems, 2) modeling the hydrology of Florida Bay, and 3) understanding the
distribution of benthic
flora and faunna. Project Objectives:
The
objective of this study
is to determine the volume and composition of groundwaters seeping upward
through the rock water
interface into Florida Bay and the coral reef tract. These studies are
necessary to determine 1) if the
level of nutrients and other contaminants is rising (i.e. baseline data) 2)
to provide data
for modeling efforts and 3) explain the mortality of certain benthic
organisms such as corals and
seagrass.
Overall Strategy, Study Design, and Planned Major Products:
The strategy of this study is to install seepage meters and measure
(quarterly) the volume
of groundwater seepage into the overlying marine environment. The waters
will be analyzed for major
nutrient levels. The primary product will be a set of volume values which
can be used by hydraulic
modelers to determine the source and movement of Florida Bay waters.
Submarine groundwater
input into Florida Bay has been ignored by modelers and results are current
models are likely to be
erroneous. An additional major product will be an improved seepage meter
design. Our experiments
indicate that those presently in use, including those designed previously
(by us) for this project
produce bogus results.
1997
1. Begin installing 50 new seepage meters.
1998
1. Continue installing the new design meters and
make modifications as needed.
1999
1. Sample meters biannually Planned Deliverables/Products:
Papers will
be given orally at national annual meetings Final products (report) will be
delivered to various
clients including State of Florida Department of Environmental Protection,
Federal EPA , NOAA,
(Florida Keys National Marine Sanctuary) Everglades National Park, and Monroe County waste water planning
department.
Planned Outreach Activities:
Ongoing outreach activities have already made this one of the more highly
visible
projects in south Florida. These outreach efforts will continue through
video, Television,
meetings with concerned groups, National Meetings, and the various
committees attended
by the investigators.
Prior Accomplishments in Proposed Area of Work:
Fifty five fiberglass seepage meter were installed on rock surfaces in
Florida Bay and
the reef tract and measurements of seepage were made for 6 months. Data
collection
ceased when tests indicated results were bogus. After much redesign and
testing we
developed a new meter which will be installed in the latter part of 1997
and early
1998.
New Directions, Expansion of Continuing Project (if applicable):
As a result of these tests we developed and tested two new seepage meter
designs. One
meter is a modification of the conventional oil drum type. To make these
the end is
removed and a clear flexible vinyl end is installed. The unit resembles a
large snare
drum. A port is positioned in the center for attaching the removable volume
collection
bag. These kinds of units are designed for insertion into sediment which is
the
application in all previously published seepage studies. The second design,
for
installation on hard rock surfaces, consists of a sheet of clear vinyl
plastic cemented
directly to the rock with hydraulic cement. A port for the volume
collection bag is
attached to the center. The unit flexes with each passing wave such that
the rock beneath
the meter "feels" the same wave-induced positive and negative pulses as the
surrounding bottom. Net outflow is channeled into the volume collection
bag. The recently completed sediment facies map of Florida Bay (see proposal by
Ellen Prager)
shows that more than 70 percent of the bottom in eastern Florida bay
consists of
Pleistocene rock. Preliminary results indicate that seeping groundwater may
replace all
of the water in eastern Florida Bay in less than 1 year. This information
has not been
incorporated in any hydraulic modeling attempts.
In our outreach efforts, a USGS video, titled "The Edge of the Continent"
highlights
this work as does a video on the Geology of Florida, produced by the State
Geological
Survey. The study has also been featured on PBS television.
Deliverables, Products Completed:
Reich, C. D., 1996, Diver-operated manometer simple device for measuring
hydraulic
head in underwater wells, Journal of Sedimentary Research Vol. 66, No.5,
p.1032-1034.
Shinn, E. A., Reich, C. D., Hickey, T. D., Tihansky, A. B. 1997, Geology
and tidal pumping
in the Florida Keys, AAPG annual meeting Dallas TX, abstracts p 106-107
Shinn, E. A., Reich C. D., Halley, R. B., Reese, R. S. 1995, Hydrogeologic
aspects of
sewage disposal in the Florida Keys GSA annual meeting New Orleans, abstract
Names of Key Project Staff: Major Equipment/Facility Needs:
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U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology This page is: http://sofia.usgs.gov/proposals/1998/grseepagep98.html Comments and suggestions? Contact: Heather Henkel - Webmaster Last updated: 11 October, 2002 @ 09:31 PM (KP) |