Woodland-Davis – Surface Water Supply Project

The Cities of Davis and Woodland, CA formed a joint partnership, the Woodland-Davis Clean Water Agency (WDCWA), to select a Design-Build-Operate (DBO) team to construct and operate a 30-mgd water treatment facility to produce potable water to largely replace their current groundwater supply. Trussell was hired by West Yost to assist with process train selection, preparation of the Request for Proposal (RFP), preparation of the DBO contract document, and permitting of this new Regional Water Treatment Facility (RWTF).

The first task completed by Trussell was preparation of a source water assessment sampling plan and subsequent detailed Water Quality Assessment Report. Based on this source water assessment, Trussell conducted a feasibility study of treatment alternatives for each step of the process train, and then prepared a conceptual design of the selected benchmark treatment train for the RWTF. The development of the process train was driven by regulatory requirements from the Division of Drinking Water (DDW) and also considered future regulations on the horizon, work led by Trussell. The benchmark treatment train is a conventional system, which includes grit removal, conventional flocculation and sedimentation with plate settlers, followed by ozonation for primary disinfection, filtration through a GAC biofilter, and final disinfection with chloramines. Primary treatment challenges for this source water include (a) fluctuating raw water turbidity, with long, continuous periods of elevated turbidity (>50 NTU), (b) minimizing DBP formation, and (c) providing best available technology for removal of synthetic organic chemicals.

Trussell conducted a series of bench-scale studies, in its Pasadena Lab Facility, evaluating (a) alternative coagulants to meet the enhanced coagulation requirements of EPA’s Disinfection By-Product Rule, and (b) the ozone demand of both raw and clarified water, needed for conceptual contactor design and cost estimation.

Trussell was also responsible for initial coordination with DDW to facilitate permitting this new water supply. Trussell prepared the required Title 22 Water Quality Assessment Report and the source water Cryptosporidium monitoring report required under EPA’s Long-Term 2 Enhanced Surface Water Treatment Rule. Trussell also assisted in preparation of the RFP, treatment performance specifications, DBO Service Contract, and review of design drawings and equipment specifications for the new RWTF.