Sewer System Assessment Planning and Design
Placer County, California

West Yost completed three separate but related projects for Placer County (County) within the Auburn Ravine Basin, including a Sewer System Condition Assessment, Collection System Recommended Improvement Plan, and the Auburn Ravine Basin Hydraulic Capacity Assessment. Timing for each project was critical since the County Redevelopment Agency’s North Auburn Commercial Infrastructure Development Program was providing partial funding for these projects under a challenging timetable. In addition, the County needed to comply with deadlines specified in the Statewide WDR, which include a System Evaluation and Capacity Assurance Plan, among other important provisions.

Relevant components of West Yost’s work included:

Sewer System Condition Assessment

The sewer condition assessment analyzed pipelines, lift stations, and manholes in the project area. Critical elements of the condition assessment included, using a quick-start approach to reduce risk in known trouble spots and to meet the accelerated project schedule, assuring the quality of field data, selecting the right rating scale for observed deficiencies, and developing the condition assessment methodology to be used in the County’s Sewer System Management Plan (SSMP), as required by the Statewide WDR.

Collection System Recommended Improvement Plan

The results of the system assessment were used to develop a Collection System Recommended Improvements Plan that summarized the condition of each pipeline, manhole, and lift station. Proposed improvement components include planning-level cost estimates for the proposed projects, and prioritize the schedule for improvements based on criteria developed by the County and West Yost.

Auburn Ravine Basin Hydraulic Capacity Assessment

This project determined design flow for the Auburn Ravine Lift Station, established the nature and timing of required collection system improvements, coordinated with the Condition Assessment work within the County’s funding timetable and regulatory requirements, and provided a reliable tool for assessing impacts of land-use changes. West Yost developed an innovative methodology for estimating peak-flow conditions at the Auburn Ravine Lift Station and within the collection system upstream of the lift station, even though no flow metering equipment functioned during the last peak wet weather event.