Polk Regional Water Cooperative Water Supply Feasibility Project

The communities within Polk County represent the second-fastest growing area in the U.S., with populations climbing by almost 20.5 percent since 2010. While this growth has fostered new boons for the County, it has also placed increasing burdens on the Upper Floridian aquifer (UFA), the traditional, but limited, source of water supply for all of Central Florida’s public water systems.

In 2015, the Central Florida Water Initiative (CFWI) released their Regional Water Supply Plan (RWSP), which projected the County’s water demand to be approximately 109 million gallons per day (mgd) by 2040. However, the UFA’s sustainable yield was estimated to be only 72 mgd, highlighting a devastating deficit that must be overcome through the diversification of water supplies. Excessive withdrawals from the UFA otherwise pose severe consequences to the region’s wetlands and other natural systems.

To meet the deficit and tackle other local water challenges, the 2020 CFWI RWSP followed up with recommendations to implement alternative water supply (AWS) projects, one common option being the use of brackish water from the Lower Floridian aquifer (LFA).

In response, Polk County and its fifteen municipal governments developed an inter-local agreement to form the Polk Regional Water Cooperative (PRWC), an independent special district that focuses on proactively identifying alternate water sources capable of meeting the region’s potable water needs while preserving the natural environment.

PRWC enlisted Carollo to lead the Water Supply Feasibility Project, a comprehensive effort to identify, refine, and implement the most viable AWS projects from an initial list of over 200 water supply concepts. After completing a collaborative evaluation process with PRWC’s member agencies, Carollo determined the feasibility of the following four projects:

• The 12.5-mgd Southeast Lower Floridan Aquifer Water Production Facility (SELFA WPF) and LFA wellfield.
• The 10-mgd West Polk Lower Floridan Aquifer (WPLFA) WPF and LFA wellfield.
• Peace Creek Integrated Water Supply Project (WSP).
• Peace River and Land Use Transitions (PRLUT) project.

The first two projects will construct large-capacity wellfields that supply brackish water from the LFA to the new SELFA and WPLFA WPFs, both of which will employ reverse osmosis (RO) as their desalination technology. Meanwhile, the Peace Creek Integrated WSP aims to increase and sustain the UFA’s water supply by implementing innovative surface water capture and aquifer recharge methods. Together, these three projects are estimated to secure more than 45 mgd in additional water supply.

Finally, the PRLUT project will involve surface water withdrawals of up to 85 mgd from the Peace River watershed. The surface reservoir system, at buildout, will offer approximately 5 billion-gallon (BG) of surface storage and direct water to a new surface water treatment, aquifer storage and recovery (ASR), or aquifer recharge and recovery (ARR) pretreatment system.

In addition to developing plans and specifications for these AWS projects, Carollo cultivated collaborative strategies to reduce costs and maximize opportunities for co-funding. Carollo recognized that, unlike in South Florida where brackish groundwater resources from the LFA are available in abundance, Central Florida’s inland location and hydrogeological conditions make establishing and treating brackish groundwater supplies prohibitively expensive for any single utility.

However, large, regional brackish water treatment facilities constructed by multiple utilities can realize a notable economy of scale. By taking a collaborative approach, PRWC has successfully earned a 50 percent share from the SWFWMD to fund the feasibility studies for the three projects alongside state appropriations and low-interest loans from the Clean Water State Revolving Fund (CWSRF) and the U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Finance and Innovation Act (WIFIA) program.

Today, Carollo has completed the preliminary designs of the SELFA and WPLFA WPF projects and expects to move forward with the final design in early 2022. The preliminary design report for the Peace Creek Integrated WSP is under review by PRWC members while the conceptual plan for the PRLUT project is anticipated to be completed in early 2022.

Carollo is also assisting PRWC in strategically deferring certain AWS-related investments to the future so the partner governments may secure sufficient resources without raising costs for customers. To this end, Carollo developed a regional demand development plan and identified conservation methods that set the stage for a financially justifiable AWS program.