Wal-Mart Antioch Detention Basin: Floc Logs Cut Turbidity from 8,960 NTU to 1.8

Local ordinances required a large detention basin on a new 25-acre Wal-Mart in Antioch, Illinois—330× 180to control stormwater release and trap sediment during grading and utilities. Water left through a perforated standpipe with gravel pack. Spring snowmelt and early rains filled the unfinished basin; raw side slopes and bottom kept feeding colloidal clay that would not settle, while wind waves eroded banks. Discharge reached environmentally sensitive wetlands around East and West Loon Lakes and failed Lake County Storm Water Management and Illinois EPA clarity standards.

Excavator Thelen Sand & Gravel worked with distributor Ero-Tex on a grit-pit plus baffle-grid train. The pit (~8 6 10) received a 15 pipe and settled heavy fractions; a downstream grid (~8′ × 30 2) held ten jute baffles. Both zones were stabilized with APS 705 Silt Stop® and jute. Sixteen APS 706b Floc Logs were placed in the upper reaches of the ~1,000′ of 15 pipe so polymer dissolved as water passedflocculating and chelating fines before the pit and baffles filtered remaining light floc.

Measured clarity: water entering the 15″ pipe at 8,960 NTU, after the first baffle 2.3 NTU, and final discharge 1.8 NTUmore than three orders of magnitude improvement with a simple, cost-effective Floc Log system that brought the basin into compliance for wetland discharge.