City of Soledad WWTP Upgrade and Expansion Project

The city of Soledad, a community of 26,000 people, was challenged to meet new stringent wastewater treatment goals, as well as expand its capacity in a short period of time. In August 2004, it was evident that the city’s treatment ponds might overflow. Additionally, the 2005 waste discharge requirement (WDR) issued requires the city to meet effluent limits of 10 mg/L BOD, 10 mg/L TSS, 5 mg/L ammonia and 5 mg/L nitrate by January 2010.

The 5.5-mgd upgrade and expansion project was designed to take the city from the existing pond system to a conventional system, increase capacity of the plant for future growth and meet WDR permit discharge requirements by January 2010. The facilities include pretreatment, secondary treatment, tertiary treatment and solids handling.

A project of this magnitude puts great financial pressure on a community of this size. The city worked diligently to acquire California Proposition 50 grant funds— applying once and being denied, and applying again and being awarded $4 million. The remainder of project funding comes from the California State Revolving Fund (SRF) low-interest loans. In order to qualify for these loans, the city needed to pass a sewer rate increase. The current economic climate made passing the rate increase very challenging. Additionally, construction of the new plant required one of the three existing treatment trains to be taken out of service. The city staff worked diligently with the Regional Water Quality Control Board to develop and execute a plan for operations during construction. The contractor was challenged with an 18-month construction schedule, where a project of this size could easily take 24 months. This schedule involved dewatering the existing two ponds, dredging them and excavating to a level below groundwater to even start construction. Through an effective partnership between the city, the design engineer and the contractor, the project has remained within budget and on
schedule despite challenges.

Owner: City of Soledad, Calif.
Designer: Black & Veatch
Contractor: Shimmick Construction Co., Inc.
Cost: $49 million
Size: 5.5 mgd; 14 million sq ft

SPS Spiral Clarifiers were installed on this project to provide the contractor with responsive service, timely delivery of high quality equipment with trouble free installation and project success for on time on budget performance. Contractor received honors as finalist for AGC Constructor
Awards for work on the Upgrade.


Partner with SPS Engineering for your upcomming project Success.

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