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projects > determination of groundwater-flow direction and rate beneath florida bay, the florida keys, and reef tract > 1999 proposal

Determination of Groundwater-Flow Direction and Rate Beneath Florida Bay, the Florida Keys and Reef Tract

Project Proposal for 1999

Project number: 7242-37654
USGS Geologic Division
Continuing Project Work Plan - FY 1999

Project title: Determination of Groundwater-Flow Direction and Seepage in Florida Bay, the Florida Keys and Reef Tract
Geographic area: Florida Bay and Reef Tract
Project start date: FY 1996
Project end date: FY 1999
Project chief: E. A. Shinn
Region/Division/Team/Section: Eastern/Geologic/Marine and Coastal/St. Petersburg
Phone: (813) 893-3100 ext. 3030
Fax: (813) 893-3333
Mail address: 600 4th St. S., St. Petersburg, FL 33701
Program: INATURES:
Program element/task: Element 7. Task 7.2

Project summary:
Sewage disposal and nutrient excess are a national if not global problem. In the Florida Keys, treated sewage is injected into the porous and permeable limestone via on-site disposal systems (OSDs). OSDs include 30,000 septic tank systems, approximately 10,000 cesspools, and approximately 1,000 shallow (class 5) injection wells. Excessive algal growth, increasing coral diseases and marine grass and sponge mortality are perceived to be caused by sewage nutrients in ground water seeping from the porous limestone on both sides of the Florida Keys. This project is aimed at determining: 1) the rate and direction of saline ground water movement beneath the Keys, 2) the origin of nutrients in groundwater, and 3) the volume and composition of groundwater seeping upward into Florida Bay and the reef tract. The results of this study are critical to understanding the fate and effects of subsurface wastewater disposal and for developing future sewage management strategies for the Florida Keys and anywhere where there are coastal fisheries and marine disease outbreaks.

Project objectives and strategy:
This project has been revised as a result of a recent peer-review panel examination. The revised objectives are: 1) to conduct additional dye and natural tracer experiments in existing monitoring-well clusters to refine lateral flow-rate calculations, 2) to evaluate standard seepage-meter designs and continue development of new meter designs, 3) to use seepage meter data to estimate daily/annual seepage volume in eastern Florida Bay, 4) to quantify major nutrient composition of seeping ground water, and 5) to determine seaward extent of groundwater seepage.  Our strategy includes incorporation of data from chemical and isotope studies being conducted by 1) J. K. Bohlke, Niel Plummer and Tyler Copelan at the USGS National Research Center, 2) Lee Kump at Penn State University (EPA funded project), 3) bacteriological studies conducted by John Paul and Joan Rose of the U. of South Florida Marine Research Center in St. Petersburg, and 4) work in close collaboration with the dozen or more other studies being conducted in Florida Bay and Florida Keys.

Potential impacts and major products:
Our results and ongoing monitoring activities provide input to models that potentially will evaluate the effectiveness of the massive South Florida Water Management District/Army Corps of Engineers ìreplumbingî of the Everglades system. We will provide, as we have in the past, additional environmental information to Everglades National Park and Monroe county officials for the purpose of redesigning sewage disposal systems in the Florida Keys. Recent regulation changes concerning the installation of disposal wells in the Florida Keys were a direct result of our groundwater studies. Monroe County (Fla. Keys) environmental officials continue to monitor this study closely. Results of our work have affected and will likely continue to affect the direction of EPA-funded research in the Florida Keys.

Collaborators, clients:
Collaborators include: South Florida Water Management District, Florida Marine Research Institute, University of South Florida, Florida State University, Penn State University, University of Miami, and Florida International University.

Internal collaborators include, PIs of all USGS projects conducted in Florida Bay and the southern Everglades. We work closely with NOAAís Marine Sanctuary Program and Undersea Research Program.

Clients include: State of Florida Department of Environmental Protection, US Environmental Protection Agency (Region 4), National Park Service, Army Corps of Engineers, Florida Keys National Marine Sanctuary, Monroe County government, and the State Department of Transportation.

Time line (FY 1999 to project end): We have installed more than 90 monitoring wells in south Florida and have monitored water chemistry from 15 offshore (reef tract) and another 30 wells within Florida Bay. Additional wells have been installed for South Florida Water Management District and two University of Miami projects funded by SFWMD. We will conduct one additional tracer study in existing well clusters and existing onshore (working) disposal wells. We have installed and will monitor remote pressure transducers to obtain long-term water-level data from both sides of the Florida Keys. Seepage meters were tested with pressure transducer installed both inside and outside the meters. The tests demonstrated that seepage meters artificially pump water in the presence of surface waves thus the volume data is bogus. We have installed and conducted preliminary tests on a newly developed flexible meter.

1998 (in progress)
1. Perform a tracer experiment in existing well clusters.
2. Sample all wells biannually for nutrient and other contaminants.
3. Drill additional wells if needed (four wells were recently installed to create a transect across Key Largo).
4. Conduct additional tests to evaluate existing seepage meter designs quantitatively (initial quantitative test prove artificial pumping in the presence of waves).
5. Develop and install new ìflexibleî seepage meters as mandated by project review (provided further testing proves their reliability).
6. Determine seepage volume using new seepage meter design.
7. Integrate new seepage and water-level data (from transducers) and attempt a simple cross-keys groundwater-flow and tidal-pumping model.
8. Begin synthesis of results (Shinn, Reich, Hickey and Tihansky) for presentations at annual meetings.
9. Negotiate for addition of experienced academic hydrologist to collaborate with team in FY 1999.
10. Begin evaluation of new radium isotope method for determining groundwater seepage and mixing.

FY 1999 deliverables/products:
Deliverable products from work to be conducted in 1999 include a major Open-File synthesis of research results. Papers addressing various aspects of our study will be extracted from this Open-File Report and submitted to peer-reviewed journals and both national and regional meetings. Papers will address: 1)tidal pumping, 2) isotope chemistry, 3) nutrient chemistry, 4) seepage rates and chemistry, 5) evaluation of seepage meters, 6) a nitrogen budget for the Florida Keys, 7) groundwater flow rates, and 8) groundwater salinity patterns beneath Florida Bay (i.e. the ìriver of sand hypothesis" which states that nutrient-rich fresh water from, underlying sandy aquifers is seeping phosphate-rich water into Florida Bay).

FY 1999 activities:
Field work to be undertaken in FY 1999 includes a dye-tracer study using the newly completed transect of wells across Key Largo. Collaboration with EPA-funded projects and University of South Florida on-site sewage disposal-well tracer studies. Twice-yearly sampling and chemical analyses of ground waters collected from existing wells. Drill additional wells if needed. An ongoing part of the study will be analysis for four isotopes of radium, for determining groundwater seepage and mixing.

New directions or major changes for FY 1999: We will continue analysis of four natural isotopes of radium that have a half-life ranging from few days to 1600 years. The techniques have been used successfully to quantify and trace mixing events/rates on time scales of a few days to several weeks. To implement this suite of tracers, we will quantify groundwater and bottom water Ra activities thoroughly, not only within Florida Bay, but also within adjacent water bodies (Atlantic Ocean, Biscayne and Floridan aquifers, Taylor Slough, etc.). We will utilize existing wells and coordinate our research efforts with similar, ongoing efforts (eg., Harvey/Price/Burnett/Chanton). This technique will advance our understanding of the role of subaqueous water flows into Florida Bay. The work will complement ongoing research efforts within Florida Bay by both USGS and outside agency scientists to quantify source/sink functions for nutrients and contaminants. This data will allow us to wrap-up the problem of seepage.

FY 1998 accomplishments and outcomes, including outreach:
1) Ongoing survey of groundwater salinity indicates presence of hypersaline water beneath Florida Bay; thus, upwelling of fresh water from below is unlikely.
2) Groundwater-flow studies using dye tracer, and SF6 indicate groundwater flow near the Keys is away from Florida Bay (to the east) at rates of up to 2 in/day. Collaborative studies around Keys onshore disposal wells show rates of up to 20 in/day.
3) Five new wells were installed, on North Key Largo and 4 new wells were completed in central Key Largo for this study and for a collaborative study with U. of S. Florida hydrologists. The wells will be used to track groundwater tracers and to groundtruth surface conductivity measurements (using GM 60). The purpose of the USF study is to determine the amount of wastewater, versus rainwater, that enters the Florida Keys system. Our tracer studies will determine the preferred direction of movement from a central position in Key Largo not affected by urban development or canal systems.

Outreach has been ongoing and abundant. The PI has represented the USGS in several videos shown on TV. One of the TV shows has national distribution. The show is Scientific American Frontiers with Alan Alda. We have talked to several civic groups, delinquent teenagers, and a group of 10,000 at a recent graduation ceremony. Our local CBS weatherman reporting from the White House Lawn said "Gene Shinn of the USGS told him that a 3-ft rise in sea level will flood 70% of the Florida Keys.î The PI recently received complimentary letters from Congressman Bill Young, and Senator Connie Mack regarding USGS research in the Florida Keys. We could go on and on with this outreach stuff but I will stop here.

FY 1998 deliverables, products completed:

Halley R.B., Vacher, H. L., and Shinn, E. A., 1997, Geology and hydrogeology of the Florida keys, Chapter 5, Geology and Hydrogeology of Carbonate Islands, Developments in Sedimentology 54, edited by H. L. Vacher and T. Quinn, 1997 Elsevier Science B. V. pp 217-248.

Shinn E. A., Reich C. D., Hickey, D. T., Bohlke, J. K., Plummer, L. N., Coplen, T. B., Busenbeberg, E., Chanton J., Burnett, W., Dillon, K., Corbett, R., 1996, Assessing the Origin and Fate of Ground Water in the Florida Keys, Florida Bay Science Conference, Program and Abstracts.

Reich, C. D., 1997, 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. 5., 1995, Hydrogeologic aspects of sewage disposal in the Florida Keys: GSA annual meeting New Orleans, abstract

Shinn, E. A., Reich, C. D., Tihansky, A. B., and Bholke, J. K., 1998, Tidal pumping drives groundwater flow and seepage of nutrient-rich water in the Florida Keys. AGU annual meeting, San Diego, CA

Paul, J. H., Rose, J. B., Brown, J., Shinn, E. A., Miller, S., and Farrah, S. R., 1995, Viral tracer studies indicate contamination of marine waters by sewage disposal practices in Key Largo, Florida: Applied and Environmental Microbiology, vol. 61, No. 6, p. 2230-2234.

Paul, J. H., Rose, J. B., Jiang, S., Kellogg, C., and Shinn, E. A., 1995, Occurrence of fecal indicator bacteria in surface waters and the subsurface aquifer in Key Largo, Florida: Applied and Environmental Microbiology, vol. 61, no. 6, p. 2235-2241.

Shinn, E. A., 1997, Coral reef demise: flushing toilets or African dust. presented at Penn State University (Dec. 1997)

Shinn, E. A. 1997, Coral reef demise: flushing toilets or African dust, presented at Eckerd College.

Shinn, E. A., 1998, Coral reef demise: flushing toilets or African dust, 9th Bahamian Geology Meeting-San Salvador.
Reich, C. D., Shinn, E. A. and Halley, R. B. 1998, Groundwater conductivity beneath Florida Bay: Does the Biscayne Aquifer discharge into Florida Bay? (abs.) Florida Bay Science Conference, Miami, Fl, May 12-14, 1998

Names and of key project staff:
1998-99, Thomas Juster (University of South Florida hydrologist) hydrology and modeling consulting.
1998-99 Peter Swarzenski (Post-Doctoral ECO employee, St. Petersburg, FL.) analysis and interpretation of new radium (223,224,228,226Ra) analyses for determining rate and mixing of subaqueous groundwater seepage.

Other required expertise for which no individual has been identified: None

Major equipment/facility needs: None

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