Town of Cross City, FL

The Town of Cross City hired WET Engineering in 2008 to provide continuing engineering services for their various utility projects. Part of the contract includes addresses ongoing compliance problems at their water plant. The Town operates a 1.88 MGD water plant that utilizes aeration, settling, filtration, storage, disinfection, and high service pumping. The raw water supply is provided by groundwater with significant concentrations of naturally occurring organics, resulting in finished water with elevated TTHM and HAA5 concentrations.

In order to reduce the TTHM and HAA5 concentrations, WET Engineering reviewed and piloted several alternate treatment technologies and compared them based on performance, cost, operability, and historical applicability. Membrane and ion exchange pilots were performed at the plant. After evaluating all the options, membranes were identified as the prime method for the removal of TTHM and HAA5s precursors.

The cost of the project is estimated near $6.5 million, to include the membrane upgrade, two mile concentrate main, and 30 acre sprayfield expansion for the concentrate disposal. Because Cross City is a small rural town with low to moderate income levels, WET Engineering began the application process for funding options through various state agencies. In October 2010, the Town received funding through DCA’s Community Development Block Grant (CDBG) to expand the effluent sprayfield. In March 2011, the Town received and accepted an offer from USDA that included a grant and low interest loan to finance the membrane upgrades and concentrate main.

The design scope for the membrane upgrade includes: rehabilitating and converting the existing gravity sand filters to green sand filters for pretreatment; the addition of two nanofiltration skids with chemical addition, cartridge filtration, booster pumping; blending; aeration with the existing air stripper; pH adjustment; and a two mile concentrate main. WET Engineering is providing funding administration, design, permitting, project management, and construction administration services on this project. Part of the engineering services includes coordinating a new rate study, negotiating water rates with the Department of Corrections, and assisting the Town with user agreements and mandatory connection ordinances. Construction on the membrane upgrades and concentrate main is projected to begin in spring 2012 and the membranes should be operational by spring 2013.