Ocala Wetland Recharge Park: A Nature-Based Solution for Beneficial Reuse

BACKGROUND Silver Springs, located in North Central Florida, is one of the state's largest first-magnitude springs and has attracted visitors since the 19th Century. World famous for its crystal-clear waters, it is the ecological and economic engine in the area. However, flow and water quality data over the past nine decades show a significant decline in spring flow and increase in nutrient concentrations which has led to the ecological degradation of the Silver Springs and Silver River systems. OBJECTIVES While not yet required by regulation, the visionary City of Ocala, located within the Silver Springs springshed, constructed a treatment wetland designed for groundwater recharge to beneficially reuse their reclaimed water by offsetting their groundwater use and nutrient loads to Silver Springs associated with municipal wastewater management. Known as the Ocala Wetland Groundwater Recharge Park, this 35-acre infiltration wetland system receives and treats up to 5 million gallons per day (mgd) of reclaimed water and stormwater to recharge the Upper Floridan Aquifer (UFA), protects water quality, and recovers and enhances the flows to Silver Springs. The Silver Springs system is subject to restrictive Total Maximum Daily Load (TMDL) regulations for nitrate and has a recovery strategy to help meet its established Minimum Flows and Levels (MFL). The Ocala Wetland Groundwater Recharge Park project supports both nitrate load reductions and recharge to help augment flows in the springshed. The Florida Department of Environmental Protection (FDEP) listed the wetland park as one of the stakeholder projects to reduce nitrogen sources in the Silver Springs Basin Management Action Plan (BMAP) area and provided Springs Funding due to its benefit to the region (FDEP, 2012 and SJRWMD, 2017). METHODOLOGY In support of the design and permitting of this project, an onsite hydrogeologic investigation, consisting of soil borings and the construction of pumping and monitoring wells across the site, was conducted to produce site-specific data. A groundwater model was then calibrated to this site-specific data and was used to evaluate the site's capacity to recharge the aquifer and the fate of the applied water to recover flows in the Silver Springs System. These efforts included innovative applications of a calibrated groundwater model combined with a wetlands treatment model to quantify recharge while ensuring the protection of water quality. It was determined that this system would have a capacity of up to 5 mgd, infiltrate an average of 5 in/day, and reduce nitrate levels to background concentrations. The designed wetland system consists of 35 acres of infiltration wetlands divided into 3 cells to receive up to 5 mgd of reclaimed and stormwater on a project area of 60 acres. The design included organically shaped cells graded in-place without the need for import of export of material to construct berms. Wetland habitat diversity was maximized by creating different ecotones across the cells that range from deep open water to shallow wetlands, islands, and rookery areas. The design also included an innovative distribution header that controls flow to each cell independently based on water level setpoints in each wetland cell. This allows for seasonal operation of water levels to maximize recharge and wetland ecological value by mimicking wetland hydroperiods that are driven by seasonal rainfall patterns. RESULTS AND CONCLUSIONS As shown in Figure 1. nitrate concentrations in the monitoring wells located within the UFA, approximately 100 feet below the wetland park, show a downward trend following park start-up and wetland planting. Nitrate concentrations in the intermediate well (within the influence of the wetland) decreased from 0.5 mg/L to 0.1 mg/L and nitrate concentrations in the compliance well decreased from approximately 1 mg/L to 0.5 mg/L after the application of reclaimed water to the site and start-up of the park. In addition, onsite recharge rates average 5 in/day, achieving the infiltration rates predicted in the groundwater model (Figure 2). The Ocala Wetland Recharge Park provides a unique case study of beneficial reuse management that addresses water supply and water quality while also giving back to the community. Since opening in the September of 2020, the park has seen over 171 bird species and an average of 3,700 visitors per month. Designed to also serve the community, the Park includes 2.5 miles of ADA-accessible trails, interactive educational displays, and some of the best birding in the County as the park was designated a Great Florida Birding and Wildlife Trail site by the Florida Wildlife Commission in 2023. The City has also developed a website and social media for the wetland park to provide the public with park photos, activities, and educational information. Further serving as an amenity to the community, the park also hosts field trips for local schools and meetings for environmental organizations like the Marion Audubon Society. In 2021, the wetland recharge park's innovation was recognized by the National Recreation and Park Association as they awarded the park with both the Innovation in Conservation Award and the 2021 Best in Innovation Award. The park represents a multi-benefit nature-based solution that should be considered for other areas in need of addressing both water supply and water quality in an innovative and natural way.