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projects >
quantification of ground-water seepage beneath levee 31N >
1998 proposal
Program: Fragile Environments Project Justification: Plans to restore historical hydrologic
conditions in the northeast section of ENP
include the raising of water levels in ENP and WCA 3B, which overlie the Biscayne
aquifer, an extremely permeable aquifer. The increase in water levels is likely to cause an increase in
seepage losses to the cast under Levee 30 and Levee 31N. Water supply for the urban areas to the east is
dependent on well fields in these areas. Application of real time data to a model and development of
empirical relationships between groundwater levels, stages in WCA3B and ENP, canal stages, and
seepage will improve management of water resources in the area, including pumping at the West Well
Field near Levee 31N and the Northwest Well Field near Levee 30.
Project Objectives: The objective of this project is to
evaluate methods for quantifying ground-
water seepage beneath Levee 30 and Levee 31N and analyze these methods with respect to data
requirements and computational effort. The use of different ground-water models will be
evaluated and empirical relationships between field data and ground-water seepage will be
developed, where possible. The data needs to determine the empirical relationships will be
evaluated. Accurate seepage data will enhance the accuracy of models of the Everglades and
coastal systems.
Overall Strategy, Study Design, and Planned Major Products:
The study area for this 5-year
effort (FY95 to FY99) is limited to a 3-mile reach of Levee 30 in north-central Dade County and
a 5-mile reach of Levee 31N in central Dade County. Hydrologic and geologic data will be
collected and utilized in the development and calibration of ground-water flow models to
determine seepage rates beneath Levee 30 and Levee 31N. Data collection will include ground-
water levels, surface-water stages, canal discharges, vertical infiltration rates, and geologic cores.
Oxygen isotope data will be used as a tracer at the Levee 31N study site. The models will include
flow nets, and cross sectional and three dimensional numerical models that will be developed
using the COE SEEP2D code and the USGS MODFLOW code. Empirical relationships will be
developed using the results of the ground-water flow models to determine the data needs to
provide real time seepage data to the regulatory and management agencies. The results for each
study site will be published in a separate water resources investigation report.
Work at the Levee 31N site will begin during the summer of 1997. This is required to obtain
sufficient data during the wet season to complete the project by the end of FY99. The existing
surface water stage, AVM discharge, and groundwater level recorder network for the West Well
Field will be supplemented with additional data collection from existing or newly drilled monitor
wells near the Levee 31N Canal. Additional wells are needed to determine the vertical head
gradients west of the levee. Infiltration meters will be installed at selected locations to measure
vertical seepage rates. Oxygen isotope data will be collected and analyzed under contract with
the University of Miami. Collected data will be utilized in the development and calibration of a
transient 3-dimensional groundwater/surface water model (MODBRANCH) to determine
seepage rates beneath Levee 31N. The MODBRANCH code will be modified to incorporate a
"reach transmissivity" leakage option between the river and groundwater. This "reach
transmissivity" relationship has been successfully used for steady conditions at this site in a
previous study.
Calculation of canal seepage rates and calibration of the Levee 31N flow model will be
completed by March 1999. An empirical relationship between field data and seepage rates will be
determined for the site. The water resources investigation report describing the results of the
Levee 31N study will be completed and published by the end of FY 1999.
All time series and miscellaneous water level, discharge, and water quality data collected for the
project will be stored in the USGS NWIS data base. Additional data will be published in the
reports and/or made available via the internet. Any cores obtained from drilling will be stored
either at the University of Miami core repository or the State of Florida core repository in
Tallahassee.
Planned Deliverables/Products:
Two water resources investigation report are planned which
will document the results of the study. The first report will be ready for colleague review by
April 1998 and will be available for distribution by the end of September 1998. The second
report will be ready for colleague review by April 1999 and will be available for distribution by
the end of September 1999. Both reports will include descriptions of the data collection and the
models developed.
Planned Outreach Activities:
Data will be made available to the SFWMD and Dade County,
when requested, for their modeling and management needs. Data will be available in the US6S
NWIS data base and via the internet. Both agencies have direct access to the NWIS data base.
Committee meetings will be attended and preliminary results will be discussed prior to approval
of the final reports.
Prior Accomplishments in Proposed Area of Work:
New Directions, Expansion of Continuing Project (if applicable):
The project, scheduled to end in FY98, is
being extended to a second site, Levee 31N. This site is more complex than the Levee 30 site
because of the presence of the West Well Field and the pumping station in the canal to the south
of the study site. This will require the use of a three dimensional flow model. A significant
amount of data is available at this site. Sources include the USGS Miami office (West Well Field
groundwater level and surface water stage and discharge monitoring network), the SFWMD,
Everglades National Park, and the University of Miami. It is anticipated that personnel from the
University of Miami Civil Engineering Department wilt be hired to assist with the data collection
and modeling of the Levee 31N site.
During FY97, data collected at the Levee 30 site was supplied to the SFWMD for use in the
development of a regional ground-water flow model. This model is being used for the
development of a "Lake Belt" plan for the area east of Levee 30 and Levee 31N. Data was
provided to the Seepage Management technical advisory committee of the Governor's
Commission for a Sustainable South Florida. Finally, data was also provided to the State
Department of Environmental Protection for use in the evaluation of a permit for a rock mine in
the vicinity of Levee 31N.
Deliverables, Products Completed:
An abstract is being written for the 1997 annual meeting.
Names of Key Project Staff: Major Equipment/Facility Needs:
None
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24 April, 2014 @ 01:01 PM
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