Designing a Complex Project on a Small Site

The Pinole-Hercules Water Pollution Control Plant was upgraded on a small site to expand its capacity, meet new discharge requirements and provide wet weather treatment capabilities. Virtually all treatment processes were updated without interruption to plant operations, safety violations or permit violations.

Given climate change, sea level rise and close proximity to San Pablo Bay and Pinole Creek Levee, the design team evaluated whether a flood wall was needed around the water pollution control plant site. It was determined that additional flood protection measures were not needed for the project.

Because the existing solids handling facility was undersized, aged and in need of replacement, it had to be relocated to make room for the expansion of the aeration basins. The existing dewatering centrifuge was reused and relocated, thus avoiding the need to purchase two new pieces of equipment that would require more materials to construct. There are two centrifuges, one new and one relocated. 

HDR provided predesign, design, bidding and engineering services during construction of improvements to upgrade the plant, which is operated by the City of Pinole, but serves the City of Hercules as well. These improvements met new conditions in the renewed National Pollutant Discharge Elimination System discharge permit that entail the elimination of blending of peak wet weather flows and use of the emergency outfall for peak wet weather flows less than 14.6 mgd. Improvements included influent pumping station, headworks, primary clarifier, aeration basins, three new secondary clarifiers, return activated sludge/waste activated sludge pumping, disinfection, solids handling (centrifuge dewatering), effluent pumping, odour control, and electrical facilities. 

Comprehensive planning was provided to overcome considerable construction challenges which included maintaining an uninterrupted, fully functional, treatment process that satisfied treatment plant discharge permit requirements regardless of external impacts, including but not limited to weather and unforeseen utility conflicts. To accommodate operational constraints the project was executed in three independent stages. The existing plant lacked redundant treatment facilities, so temporary facilities were built to facilitate the shutdowns. Every single treatment process had to be updated, except for digestion.

Steps were taken to preserve and protect the environment during design and construction and to continue to be a good neighbour in the community. Odour control measures minimized complaints from the public and adjacent landowners.