FLORIDA PROJECTS

• Aquifer Characterizations
• Aquifer Tests near Herbert Hoover Dike/Lake Okeechobee
• ASR and water supply development with sequence stratigraphy
• Borehole geophysical logging for the Florida Power & Light Turkey Point Plant
• Borehole Geophysical Logging Program
• Linking a conceptual karst model of Biscayne aquifer to GW flow
• Subregional Basin Hydrogeologic Characterization for CERP regional ASR

• Availability of Water

• Climate Change and Hydrologic Extreme Events

• Ecosystems

• Hydrologic Modeling

• Surface Water

• Water Quality Conditions

• Wetlands

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Results of aquifer tests conducted near the Herbert Hoover Dike at Lake Okeechobee in south-central Florida

Project Chief: Louis Murray
Cooperator:U.S. Army Corps of Engineers
Period of Project: October 2009 - September 2011

Problem Statement

Figure 1. Locations of aquifer tests near the southern and southwestern perimeters of Lake Okeechobee.

Lake Okeechobee, in south-central Florida, is the second-largest freshwater lake within the United States. The Herbert Hoover Dike (HHD) surrounds the perimeter of Lake Okeechobee. The HHD was originally constructed in the 1920s and 1930s by the United States Army Corps of Engineers (USACE) for regional flood control and to mitigate erosion of surrounding areas. Throughout its history, the HHD has experienced numerous seeps (slow leaks) along the toe during high water events, and plans to refurbish and rehabilitate the dike have been discussed since the 1980s. Proposed seepage controls include construction of a seepage berm on the land-side toe (base) of the dike and placement of a cut-off wall in the embankment along its foundation. However, information on the hydraulic characteristics of the underlying surficial aquifer system, which is needed for the design and successful placement of the berm and cut-off wall, was lacking.

Objectives

The objective of the project was to quantify hydraulic properties, particularly transmissivity, of the surficial aquifer system at selected aquifer-test sites located near the southern and southwestern perimeters of Lake Okeechobee. The test sites are spaced about 5 to 10 miles apart at Clewiston (HHD2-1), Moorehaven (HHD2-2), South Bay (HHD3-1), and Lake Harbor (HHD3-2) (fig. 1).

Approach

TLithologic and geophysical logs collected at each test site were examined to identify the principal hydrogeologic units comprising the surficial aquifer system. Monitoring wells were constructed to collect water-level information in permeable units identified from the logs. Four multi-well aquifer tests conducted by the U S. Army Corps of Engineers between September and December 2010 were analyzed by the USGS with a three-dimensional numerical model and parameter-estimation routine. Numerical analyses, as opposed to analytical analyses, were necessary to account for the influences of nearby canals and the effects of pumping-induced flow in fully-penetrating observations wells on water levels in nearby observation wells. The numerical approach was used to estimate hydraulic property values of individual hydrogeologic units, whereas analytical solutions are limited to estimating hydraulic properties for all hydrogeologic units combined. Model grids extended far enough from the pumping wells such that boundary effects were assumed to be negligible. The models were discretized vertically from the water table to the bottom of the surficial aquifer system or, for HHD2-2, to a thick layer of silty sand at 150 ft below land surface. Water levels measured in background wells were used to adjust drawdown at HHD3-1 to account for environmental influences and regional pumping effects.

Information Product

A USGS Open File Report (OFR) will summarize the results of aquifer tests conducted near the Herbert Hoover Dike at Lake Okeechobee in south-central Florida.