Commission authorizes $121,048 to install weir covers on wastewater secondary clarifiers to curb algae growth

The Atchison City Commission authorized staff Feb. 3 to hire IEC to supply and install weir covers on two secondary clarifiers at the city wastewater treatment plant to control algae growth, authorizing $111,848 for the work and up to $9,200 in additional mobilization fees if the contractor must come sooner than scheduled.

Clint McNamee described the clarifiers as circular tanks roughly 85–90 feet in diameter where sunlight, phosphorus and calm water create conditions conducive to algae. He said algae previously fouled the plant's UV disinfection system and caused about $18,000 in damage when bulbs were covered; staff chose a cover-based solution rather than ongoing chemical treatment.

McNamee reviewed the city's prior, less-expensive temporary covers — pool-style tarps installed about a decade ago — and explained that wind damage during a recent storm damaged those temporary covers and a catwalk. He said the newer weir-cover option under consideration covers only the peripheral weir area rather than the full tank and is less wind-susceptible and less likely to cause trapped-ammonia problems than prior full-surface covers. A vendor-provided quote in the staff report put rigid full covers at roughly $260,000; the canvas-style peripheral weir covers proposed from IEC were lower-priced.

Commissioners asked about timing, sunlight tolerance and long-term effectiveness; McNamee said the proposed covers had previously blocked sunlight successfully and that staff planned to push for an earlier mobilization if possible to avoid algae growth in warmer months.

The motion to authorize the IEC contract (base $111,848 plus up to $9,200 mobilization) passed on a voice vote. Staff said the item is in the current budget and that timing could affect the final price if mobilization is required.