Designing an Alternative Water Supply for Central Florida

Planning, design and construction is under way in Central Florida to build a 470-million-gallon reservoir that will capture storm water and augment the region’s water supply as a sustainable alternative to traditional groundwater sources to meet the future water demands.

The Tohopekaliga Water Authority (TWA), along with other stakeholders, are collaborating to design an alternative water supply (AWS) reservoir on a 450-acre property, formerly known as Judge Farms, along the northern shore of Lake Tohopekaliga, also known as Lake Toho.

WSP USA is providing TWA with water resource consulting and engineering services to permit, design and implement the project. The team has completed conceptual design, analysis and water use permitting for the AWS infrastructure portions of the project. TWA’s project partner, Osceola County, is currently constructing the reservoir to provide storm water management as part of site development efforts.

“Due to environmental and regulatory constraints, the future use of traditional groundwater sources in the central Florida region will be limited,” said Dale Helms, project manager for WSP. “This project, when constructed, will provide up to six million gallons per day of new water supply to TWA’s 14,500 non-potable customer connections, impacting up to 35,000 residents.”

Once completed, the Judge Farms project will provide the region with multiple benefits, including regional flood control, storm water treatment, water quality improvements in Lake Toho, reuse system augmentation, and a public park.

“The new reservoir will harvest and store storm water and surface water for non-potable water system augmentation,” said Saurabh Srivastava, deputy project manager for WSP. “It will also provide nutrient removal from surface waters that discharge to Lake Toho and the Kissimmee River, part of the headwaters for the Florida Everglades.”

The Judge Farms project is one of the sustainable solutions included in the Central Florida Water Initiative regional water supply plan as a way to offset impacts from the overuse of traditional groundwater supplies.

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©2018 WSP USA

Dale Helms and Saurabh Srivastava are leading the WSP team that is providing conceptual design and other engineering services for the Judge Farms reservoir project.

Ideal Location

The western half of the property’s natural low topography, size and proximity to surface waters made it an ideal location to develop a regional reservoir. Two local tributaries—East City Ditch and Mill Slough—flow near the property and discharge into Lake Toho.

“Excess surface water flowing through the tributaries, along with storm water collected from the property itself following development, will be captured during periods of high flow and directed into the reservoir,” Helms said. “The captured surface water and storm water will be used as an alternative water source.”

“By diverting storm water before it enters Lake Toho, the reservoir and AWS use will also reduce the amount of pollutant nutrients that enter Lake Toho and other downstream surface water bodies,” Srivastava added.

The eastern half of the Judge Farms property, which is higher in elevation, is being developed as a major technology hub (NeoCity) for Osceola County. The development of the high-tech commercial and residential community will be integrated with the water resources management reservoir.

Osceola County is using excavated material from reservoir construction as fill for the site development.

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©THINKSTOCK

The Judge Farms reservoir will provide multiple benefits, including water quality improvements for Lake Tohopekaliga.

Pollution Control

As part of the conceptual-level design, WSP investigated options for the size, location and geometry of the reservoir; the available storage volume; the type and location of potential inflow/outflow structures and conveyance components; and the conceptual type, size and potential location of a water treatment facility.

“WSP developed several conceptual facility alternatives and performed an analysis of the reliability of supply for different water level control elevations,” Srivastava said. “This project could prevent thousands of pounds of nitrogen and phosphorus annually from being discharged into Lake Tohopekaliga and the Kissimmee River.”

WSP reviewed regulatory treatment requirements for use of the water stored in the reservoir for supplemental non-potable supply and investigated the potential location and types of intake, which determined that pumped intake would be most reliable.

The firm also assisted TWA to obtain a long-term water use permit for the project from the South Florida Water Management District (SFWMD).

“The WSP team used several analytical methods to provide reasonable assurance to SFWMD that the proposed diversion would not cause unacceptable impacts,” Helms said. “A continuous simulation water budget model was created to study the long-term operation of the entire AWS system, including the diversion of storm water and surface water, and operation of the reservoir between projected minimum and maximum water levels while meeting TWA’s demand needs.”

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The new water reservoir will cover 140 acres along the northern shore of Lake Tohopekaliga.

Uncommon Achievement

Hydrologic and hydraulic modeling of the watershed and tributaries—which simulated historical, current and proposed future flow and stage conditions for the Upper Kissimmee system—showed that the proposal will not have significant impacts on water resources, natural systems or existing legal water users.

“Groundwater flow modeling also provided assurances that the proposed operation of the reservoir will not cause unacceptable impacts to wetland systems near the project site,” Srivastava added.

As a result of WSP’s analysis, TWA received a 30-year water use permit (WUP) with a maximum annual allocation of three billion gallons of water per year, or an average of about eight million gallons per day.

“Issuance of water use permits for surface water systems like this are not common in Florida,” Helms said. “This WUP was issued concurrently with the environmental resource permit for the reservoir, which was secured by Osceola County. Significant collaboration was necessary to align the goals, expectations and deadlines of both permits.”

WSP has started work on final design of initial AWS project components—primarily the reservoir intake structure. Completion of reservoir construction is expected within the year, and final design and construction of TWA’s AWS infrastructure—including intakes, water treatment facility and distribution system—will follow in the upcoming years.

“WSP is working diligently to meet the client’s individual needs, and the needs that arise from the other stakeholders as the project progresses,” Srivastava said. “Under Dale’s leadership, WSP successfully navigated complex regulatory requirements to obtain a long term WUP for a project that has significant environmental and economic benefits. The client is pleased with our efforts. At the end of the day, a successful project means a happy client.”

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