Mariposa County requests proposals from Contractors for sludge dewatering and hauling services at two of its wastewater treatment plants (WWTP). The work includes the removal of wet sludge, dewatering, and disposal of the biosolids at the Mariposa landfill per local, State and Federal requirements. Work also includes dewatering/bypass pumping for inspection and repair of facilities by others. The initial contract term will be for 2 years.

In Yosemite West, the selected Contractor shall pump the 10,000 gal. sludge tank, the 30,000 gal. clarifier and 125,0000 gal. of primary sludge from the lower aeration pond. In addition to sludge dewater and removal, the Contractor shall bypass and clean the clarifier for inspection by County staff. The clarifier’s arms and motor are damaged, and it’s expected the bypass to be in place for several weeks while repairs are made by others. The distance from Yosemite West to the County landfill is approximately 65 miles. Average inflow is approximately 60,000 gal/day.

In Mariposa Pines, the selected Contractor shall remove approximately 100,000 gal. of primary sludge from the aeration pond. In addition to sludge dewatering and removal, the Contractor shall construct a containment berm, bypass and drain the aeration pond for embankment repairs by others. It’s expected this bypass to be in place for several weeks while repairs are made by Others. The distance from Mariposa Pines to the County landfill is approximately 19 miles. The system serves 23 homes. Average inflow is approximately 275 gal/day in the summer.

Contractors may propose their preferred method of sludge dewatering. It’s anticipated the Contractor will use a mobile centrifuge or press but due to site constraints, the Contractor may choose to haul the wet sludge offsite prior to dewatering. The Contractor may propose alternative methods, if desired.

The project requires prevailing wage.

Technical questions should be directed to John Luthey at