City awards $13.6 million construction contract to rehabilitate Lake Mary treatment plant sedimentation basins

Flagstaff City Council on Oct. 21 approved a construction contract for $13,600,000 with PCL Construction to rehabilitate two 1,000,000‑gallon sedimentation basins at the Lake Mary Water Treatment Plant.

Water Services project manager Justin Emmerich told the council the Lake Mary plant—originally constructed in 1941 with the basins added in 1963—provides a sizable portion of the city’s drinking water. A recent concrete condition assessment documented widespread degradation consistent with decades of service and water chemistry effects.

Emmerich said the project will replace mechanical rake assemblies that remove sediment from incoming lake water and install more energy‑efficient equipment. The work follows design completed with Brown and Caldwell and was procured using a construction manager at risk (CMAR) delivery; the council approved the construction phase GMP at the Oct. 21 meeting.

Council member questions

Council members asked about lining and longevity. Emmerich explained the basins are concrete structures with a concrete water‑sealing coating applied decades ago that is failing in places, allowing water to seep into cracks. He said modern concrete and polymer technologies used in the rehabilitation are expected to extend longevity beyond past service life.

Council action

The contract award for CMAR construction phase services with PCL was approved by council motion and vote on Oct. 21. Staff said an owner’s contingency is included and that contractor allowances were built into the negotiated GMP.

Ending

Staff said the rehabilitation is vital to maintain Lake Mary Water Treatment Plant output and reliability. Construction scheduling and contractor coordination will proceed under the CMAR agreement; staff will return with construction oversight updates as the work begins.