Construction Management for Water Treatment Plant and Subsequent Expansion
Mountain House Community Services District, California

West Yost provided construction management (CM) and inspection services for the new water treatment plant and subsequent expansion of the plant to 15 mgd. West Yost’s construction management included successfully addressing continuous operations during construction, shut downs and tie-ins, site safety and security, and complex electrical system integration.

The original plant construction included two Trident filters with a 2.5 mgd treatment capacity, expandable to 20 mgd. Two miles of 36-inch diameter steel pipe were installed to transmit the water from the pump station to the treatment plant. The project included a 4 MG steel raw water tank that was constructed to hold an emergency supply of water and a 4.3 MG steel finished water tank that was constructed for storage capacity and fire protection. The new treatment plant used free chlorine as the disinfectant. A booster pump station with a pumping capacity of 5 mgd was constructed to deliver water to the community.

West Yost also provided the CM and inspection for a substantial expansion of the original plant, increasing the plant’s reliable production capacity to 15 mgd. This project consisted of additional pumping capacity, a third high-rate clarifier-filter package, an ultraviolet light disinfection system, and ammonia storage and feed facilities. The new 15 mgd Water Treatment Plant includes jet mixers, flocculators, inclined plate settlers, settled sludge collectors, granular media filters containing activated carbon, and an ultraviolet light disinfection system. Storage and feed systems are provided for the following water treatment chemicals: alum, aqueous ammonia, cationic polymer, nonionic polymer, sodium hydroxide (caustic), sodium hypochlorite, and potassium permanganate. Solids handling facilities for the pretreatment sludge and filter backwash wastewater include equalization basins and dewatering lagoons. Related improvements include additional pumps and standby power at the existing raw water pump station, a replacement low-lift pump station and wetwell, additional standby power capacity, and an integrated SCADA system for process control and data logging.