Description

Mill Creek Sink Water Quality Improvement Project

The Mill Creek Sink Water Quality Improvement project site is located northeast of the intersection of Interstate 75 and State Road 441 in the City of Alachua, Florida. The project site is adjacent to Mill Creek Swallet and Mill Creek Sink, a karst system that drains a 23 square mile watershed.

Prior to project implementation, stormwater runoff from four commercial properties and portions of Interstate 75 and State Road 441 received minimal treatment prior to flowing through the project site towards Mill Creek Swallet. Mill Creek Swallet and Sink directly recharge the Upper Floridan aquifer and are hydrologically connected to an underground conduit network that flows towards the Santa Fe River. Dye trace studies conducted in 2005 found that water entering Mill Creek Sink travels to Hornsby Spring on the Santa Fe River within about 12 days (Butt et al. 2006).

The designed system consists of a treatment train that includes 1) lined swales that capture large debris, 2) pre-treatment basins or catchment areas that slow down stormwater and increase retention time so that sediments and sediment-associated contaminants have time to settle out of the water column, and 3) a treatment wetland that facilitates denitrification. Nutrient load reductions are estimated to range from 54-77% for total nitrogen and 84-91% for total phosphorus. The modeled results demonstrate that the project prevents 129 lb/yr and 26 lb/yr TN and TP, respectively, from entering Mill Creek Swallet and Sink, the Upper Floridan aquifer, and springs along the Santa Fe River. Project funding was provided through grants from both the Suwannee River Water Management District and the Florida Department of Environmental Protection.

Presenter: Jennifer Sagan

Jennifer Sagan is a senior project manager and associate scientist with WSP USA. She has a B.S. degree in zoology and a M.S. in microbiology with an emphasis on bioremediation. For over twenty-five years she has been involved in the monitoring, assessment, and restoration of aquatic systems in Florida. She is currently managing restoration and resiliency projects throughout Florida for the FDEP, USFWS, FWC, UF, and local municipalities. She leads engineering and scientific teams that incorporate ecological targets, modeling, and civil, structural, and geotechnical engineering into restoration project design. She has designed sampling plans for wetland habitats that serve both as baseline data and project planning data that informs the engineering design for restored habitats and ensures projects are permittable. Jennifer currently lives in Gainesville, Florida and loves that the surrounding area provides quick access to so many beautiful natural systems.

View north of lined swale, east-most catchment basin, and treatment wetland (MIll_Creek)

Details of treatment wetland plantings

View west of inflow structure from west-most catchment basin and overflow structure from treatment wetland into adjacent wetland