Water levels in the Lake are currently regulated by a complex system of pumps, spillways, and locks according to a regulation schedule developed by the USACE. The regulation schedule attempts to achieve multiple-use purposes as well as provide seasonal lake level fluctuations. The schedule is designed to maintain a low lake stage to provide both storage capacity and flood protection for surrounding areas during the wet season. The schedule is also a guide for the management of high lake stages that might threaten the integrity of the Herbert Hoover Dike and thereby risk flooding of downstream lands. During the winter, lake water levels may be increased to store water for the upcoming dry season. This is facilitated by holding water that flows into the Lake from the Kissimmee River Basin and by backpumping from the EAA.
Water quality data indicate that the Lake is currently in a eutrophic condition, primarily due to excessive nutrient loads from the agricultural sources both north and south of the Lake. In the late 1960s and early 1970s, total phosphorus concentrations as low as 50 parts per billion (ppb) were measured. Currently, total phosphorus concentrations in the Lake have been measured in the 100 ppb range. It is likely that historic in-lake turbidity was much lower than current conditions as well.
The CERP presents a new operational plan for the Lake that maximizes water storage opportunities, enhances wildlife populations, restores the ecological health of the Lake, and protects coastal estuaries and public health. ASR technology provides storage - an important component that will contribute to the overall Everglades restoration. The CERP includes the construction of up to 200 ASR wells (with associated pre- and post- treatment facilities) installed adjacent to Lake Okeechobee, with a total combined pumping capacity of 1 billion gallons of water per day. Specifically, the CERP states:
“The purpose of this feature is to: (1) provide additional regional storage while reducing both evaporation losses and the amount of land removed from current land use (e.g. agriculture) that would normally be associated with construction and operation of above-ground storage reservoirs; (2) increase the Lake's water storage capability to better meet regional water supply demands for agriculture, Lower East Coast urban areas, and the Everglades; (3) manage a portion of regulatory releases from the Lake primarily to improve Everglades hydropatterns and to meet regulatory discharges to the St. Lucie and Caloosahatchee Estuaries; and (5) [sic] maintain and enhance the existing level of flood protection.”
ASR technology is proposed as a significant storage component in the CERP, with the FAS acting as a large underground reservoir. The advantages of using ASR technology for these objectives include:
Reduced costs compared with expensive, surface storage facilities
Eliminates detrimental discharges to the St. Lucie and Caloosahatchee estuaries
Nearly unlimited underground storage capacity eliminates water losses due to evapotranspiration and seepage
Wells can be located in areas of greatest need, reducing water distribution costs
Requires limited land acquisition
Provides the ability to recover large volumes of water during severe droughts, presumably when reservoir levels would be low
These advantages are particularly important in South Florida where land acquisition costs are high, the availability of water is seasonal, and the underlying FAS are geographically extensive.
The South Florida Ecosystem Restoration Task Force Working Group commissioned the development of an ASR Issue Team in 1998. The Team – consisting of members of the SFWMD, USACE, EPA, FDEP, USGS, other local governmental agencies, and private consultants – met to address the technical and regulatory uncertainties associated with the ASR technology and the scale at which it is proposed in the CERP. The ASR Issue Team identified seven (7) issues that should be addressed prior to full-scale implementation, as presented in their report (ASR Issue Team, July 1999). At least three (3) of these issues are regional in nature. While the ASR pilot projects themselves – including the subject Lake Okeechobee ASR Pilot Project – will not address all seven issues, they will provide valuable site-specific data, which can be used in the regional analyses (including model development) to address all seven issues. A more detailed discussion of the Issue Team items is contained in a subsequent section of this document.
The primary area of investigation for ASR implementation is the perimeter area around the northern rim of Lake Okeechobee, from the City of Moore Haven on the west to the City of Okeechobee to the north, to Port Mayaca on the east, as shown on Figure 2 [renumbered as Figure E-1 in this report]. The known occurrence of poorer quality water on the south side of the Lake due to EAA backpumping operations suggests that the remaining area along the Lake perimeter would be a secondary area of investigation.
The area of investigation adjacent to the Lake is characterized as lowland, at an elevation of between 10 to 20 feet above NGVD. Land use is primarily unimproved and improved pasture, wetlands, and occasional areas of planted field crops. State Road 441 runs along the northeast perimeter of the Lake, whereas State Road 78 runs along the northwest perimeter of the Lake.
The final locations and layout of the pilot ASR wells and monitor wells have not been determined at this time. Well siting must incorporate information regarding the proposed footprints of the pilot facilities and feasible conveyance systems to surface water bodies. Well locations and spacing will also be determined based on specific-capacity and aquifer test data obtained from the initial exploratory wells. For more information on the geologic and hydrogeologic setting of the Lake and the aquifers relevant to this project, the reader is referred to Section 4.