Wastewater Treatment Plant Redundancy Project

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South San Luis Obispo County Sanitation District (SSLOCSD)

Project Name
Wastewater Treatment Plant (WWTP) Redundancy Project

Constructability Review
Construction Management
Construction Inspection
Office Engineering



The SSLOCSD owns and operates a wastewater treatment plant (WWTP) for processing wastewater from nine miles of sewer lines from the City of Arroyo Grande, City of Grover Beach, and Oceano Community Services District. The WWTP has a peak dry weather flow of 5-million-gallons-per-day (MGD) capacity, with current flows ranging from 2 to 3 MGD, and is National Pollutant Discharge Elimination System (NPDES) permitted. The existing treatment plant cannot meet effluent limits at the permitted design flow if the fixed film reactors (FFR) or the secondary clarifier is out of service and there are no redundant units for either process. The existing plant uses mechanical screens, primary clarifiers, FFR, one secondary clarifier, and chlorination to provide secondary treatment with disinfection to treat wastewater.

The Regional Water Quality Control Board (RWQCB) has had ongoing discussions with the District regarding the need for a redundant biological nutrient removal (BNR) train in case of a failure with a key component of the current process train. The goal of project is to allow major process units to be removed from service for maintenance or repairs without risking violation of effluent permit limits.

MNS is providing complete third-party construction management services from the pre-construction phase through post-construction activities over a 30-month project duration.

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