The 201 Facilities Plan completed for Lake City in 1977 recommended termination of discharge of the City's treated wastewater (effluent) to Alligator Lake, to be replaced by spray irrigation on an upland tract(s) some five miles southwest of the St. Margaret Road Wastewater Facilities (WWF). After a long series of grant problems, land use zoning issues, and reassessments by the U.S. Environmental protection Agency (EPA) of alternate discharge methods to area surface waters (e.g., Suwannee River), use of spray irrigation on the site designated in the 201 Plan was still considered the most feasible method of effluent disposal. Construction of the effluent irrigation system began in February 1986 with installation of the effluent transfer pipeline. The entire system was completed September 1987.
A primary objective of the spray irrigation system is to protect the area's groundwater. Because Alligator Lake occasionally drains completely to the underlying aquifer via sinkholes, discharge of effluent to the lake represents a potential threat to drinking water. The irrigation system safeguards groundwater by allowing the effluent to slowly filter through 5 feet of sand over approximately 350 acres of land before it enters the ground-water. Eliminating effluent discharge to the lake will also improve water quality by reducing nitrogen loading. The nitrogen in the effluent will now be used to enhance the growth of grass for hay.
General Process and Facilities Description
Secondary effluent from the St. Margaret Road Water Reclamation Facility (WRF) is chlorinated and continuously pumped by two 6,300 gallons-per-minute (gpm), variable speed transfer pumps through 4 miles of 24-inch pipeline to the effluent irrigation site. The site facilities include a 45-million-gallon (MG) reservoir to accommodate effluent flows during normal non-application periods and for up to 15 days during periods of high rainfall.
Effluent is applied to the treatment fields through an irrigation system consisting of four 2,100-gpm constant speed pumps, a system of distribution pipes and valves, and 70 fixed gun type sprinklers. An under drain system captures the percolate water passing through the root zone, as well as rising groundwater, and conveys the water to the Floridian aquifer through four soil profile modification pits. Crops grown on the application site include Bermuda grass and ryegrass.