Wastewater Treatment Improvements
City of Davis, California

West Yost was originally retained by the City to perform facilities planning, design, and construction services for a major expansion and upgrade to the City’s Water Pollution Control Plant (WPCP). The wastewater facilities planning process incorporated the City’s unique vision of combining natural treatment systems with conventional treatment processes to provide reliable effluent water quality while creating wetlands and other habitat features that serve as a showplace and resource for the region. This $13 million project involved expansion of virtually all pumping and treatment facilities, laboratory and personnel space, and provided for an improved level of secondary treatment to bring the plant into regulatory compliance and to increase plant capacity from 5.3 to 7.5 mgd.

Major plant improvements designed by West Yost included replacing the influent pump motors/ controls; improvements to screening, channels, and new primary clarifier; new anaerobic sludge digester and lagoon; pond improvements; overland flow system improvements; and laboratory/administration building expansion. West Yost also designed improvements to the existing influent pumping station including motor and control replacements, modifications to approach channels to existing screening facilities, gravity bypass to existing ponds, and effluent pumping station improvements including rotary screen additions.

In association with another engineering firm, West Yost was retained for  preparation of a Strategic Master Plan and a preliminary design for the City’s WPCP. The Strategic Master Plan identified and evaluated three major alternatives for expanding and upgrading the existing facility to address anticipated and potential NPDES permit requirements and to increase treatment system reliability. The preliminary design phase included verification of design and sizing parameters and addressing outstanding operational and performance issues related to the treatment processes decision, especially in the area of metals and organics removal.

The major role provided by West Yost under the preliminary design project included preliminary design of the headworks, primary treatment, solids treatment and disposal, and plant auxiliary systems; evaluation of the City’s wetland facility and its continued maintenance once it no longer served as part of the treatment train; evaluation of potential summer-season reuse options; and space planning for the operations, laboratory and maintenance buildings.

West Yost has also provided a number of services to the City in evaluating various reuse opportunities on areas surrounding the WPCP.