Pinole's Wastewater Treatment Plant

Wastewater Treatment Plant

The Pinole-Hercules Water Pollution Control Plant is located at the foot of Tennent Avenue in the City of Pinole.

It was originally built in 1955 as a primary treatment facility. Since then, it has had two major expansions and several modifications in order to meet the needs of these cities' growing populations.

In 1972 the plant was upgraded from a primary to a secondary treatment facility, with a 2 MGD (million gallons per day) flow capacity. In 1985, the plant was again upgraded to handle a flow of 4.06 MGD. The plant serves a combined population of approximately 40,000, with an average daily flow of 3.5 million gallons.

In 2019, the City completed a full scale upgrade of nearly every treatment process. The construction was about $45 million and lasted over 1000 days. 

The plant process (activated sludge) removes approximately 97% of the waste from the water. The water is then disinfected with hypochlorite. Once the disinfection process is complete, the hypochlorite is then removed and the water is pumped into the deep waters of San Pablo Bay.

All operators are certified by the state, grade levels vary from 1 through 5. Some plant personnel also hold certificates in maintenance and laboratory analysis.



To operate this facility to the highest standards and in a professional manner protecting the community and the environment.

Should the City of Pinole recycle wastewater?
The Pinole-Hercules Wastewater Treatment Plant (WWTP), located at 11 Tennent Avenue, treats all of the residential and commercial wastewater generated in Hercules and most of the wastewater generated in Pinole. The plant removes solids from the wastewater and sanitizes the water, then discharges the wastewater into the Bay through a pipe in Rodeo.

It might be possible to use the treated wastewater for productive purposes, such as to recharge underground aquifers, provide irrigation water in specific instances, and for industrial purposes if it is processed further. The City is hiring an expert to assess the technical and financial feasibility of reusing the treated wastewater. The City would like to hear the community's thoughts and ideas on this matter:


Proposed Wastewater Service Charge Increase
2018 Sewer Rate Study Report
Proposed Sewer Rate Increase Prop 218 Notice

Pinole-Hercules Water Pollution Control Plant Upgrades Information
Project Plans 11X17 (Very Large File)
Part 1 Contract Requirements
Part 2 Technical Specifications
Preliminary Design Report (March 2013)
Preliminary Design Slides (March 2013)

Pinole-Hercules Water Pollution Control Plant RFP Information

Request for Proposals

I. June 2009 Report to Board from Dodson Psomas
Psomas June 1 2009 Report to the Board no Appendix
Psomas June 1 2009 Report to the Board

II. Draft Preliminary Engineering Report by HDR
Appendix A- Pinole-Hercules WPCP Upgrade Geotechnical Research Letter Report 2013-02-19
Executive Summary
Pinole Table of Contents
TM 01- Flows and Loads
TM 02- Waste Discharge Requirements
TM 03- Treatment Plant Modeling Steady State Mass Balance Model Calibration & Design Conditions
TM 04- Construction Phasing
TM 05- Headworks- Influent Pumps, Screening, and Grit Removal
TM 08- Flow Equalization, Aeration Basins, Blowers, Secondary Clarifiers, and RAS-WAS Pumping
TM 12- Disinfection System Alternative Analysis
TM 13- Solids Handling
TM 14- Effluent Pumping
TM 15- Hydraulic Profile
TM 17- Plant Control Strategies
TM 18- Electrical Distribution System and Plant SCADA System Configuration Evaluation
TM 19- Plant Utilities and Yard Piping
TM 20- Demolition and Site Work

III. June 2012 Order No. R2-2012-0059 NPDES Permit No. CA 0037769 Operating Permit for Plant
2012 Permit

IV. Standard Consultant Agreement with the City of Pinole
Standard Pinole Consulting Agreement

V. May 2009 Anti- Degregation Analysis for Proposed Wastewater Treatment Plant Discharge Modification
Antidegradation Analysis

VI. October 1, 2009 Technical Memorandum from Larry Wallker and Associates
Dilution Study

VII. Final Environmental Impact Report
Pinole-Hercules FEIR_06.30.10

VIII. Draft Environmental Impact Report by AECOM with Appendices
Pinole Hercules DEIR Appendices
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Pinole Hercules DEIR 03.15.2010

IX. Mitigation Monitoring Plan
Pinole-Hercules MMRP

X. Topographic Surveys
AutoCAD Trailer Park
PDF 1-26-09
Topo Survey - Wastewater Plant upgrades (1-21)
Topo Survey - Wastewater Plant upgrades (1-32)

XI. Value Engineering Report
December 2013 Value Engineering Report

Miscellaneous Information

June 1, 2009 Report to the Regional Water Quality Control Board

Frequently Asked Questions about the Pinole Hercules Water Pollution Control Plant (WPCP)

Fact Sheet about the Pinole Hercules Water Pollution Control Plant (WPCP)

City of Pinole Sewer Master Plan, May 2008

Exhibit of Areas to be Studied


Pinole/Hercules WPCP Wastewater Treatment Process

Preliminary Treatment

Screenings – Wastewater flows through an Envirocare® Plate Screen system that uses perforated plates on a conveyor type arrangement that removes large debris from the wastewater to protect downstream equipment.

Primary Treatment

Three primary clarifiers are used to remove settleable and floatable materials that are sent to the gravity sludge thickener for further processing.

Activated Sludge Process with BNR (Biological Nutrient Removal)

The activated sludge process uses aerobic microorganisms to further treat the wastewater by oxidizing carbonaceous biological matter. Bacteria living in the mixed liquor convert ammonia in the wastewater to nitrates, a form of nitrogen that is non-toxic. Treatment of nitrogenous matter or phosphate involves additional steps where the mixed liquor is left in anoxic condition (meaning that there is no residual dissolved oxygen).

Secondary Clarification

The secondary clarifiers slow the flow to allow the microorganisms and other solids to settle to the bottom of the clarifier where they can be returned to aeration tanks to continue treating the waste.  When the plants microorganism inventory gets too high a portion of this return flow is wasted to the solids handling process.  The clean water or supernatant flows over the top of the clarifier weir.

Disinfection Process

Sodium Hypochlorite is used to disinfect the plants effluent.  Sodium Hypochlorite is a liquid form of chlorine similar to household bleach that is used to kill pathogens in the water before it is released into San Pablo Bay.  Just prior to release, sodium bisulfite is added to the water to neutralize any remaining chlorine which is hazardous to marine life.

Solids Handling Process

Gravity Thickener

The Gravity Thickener is another settling tank that receives solids from the primary clarifiers and the waste activated sludge where it further separates solids from the liquid. The sludge from the bottom of the thickener is sent to the Rotary Drum Thickener for further thickening. The overflow of water from the thickener is sent back to the plant headworks.

Rotary Drum Thickener

The Rotary Drum Thickener (RDT) receives sludge from the gravity thickener at approximately 1% solids concentration or 10,000 mg/l.  The RDT further thickens the sludge to approximately 4% solids concentration or 40,000 mg/l before it is pumped to the Anaerobic Digesters.

Anaerobic Digesters

Sludge solids from the RDT are pumped into anaerobic digesters where bacteria, in an oxygen free environment, break down solids producing methane gas, carbon dioxide and stabilized organic solids. The methane gas is used to fuel the plant co-gen that provides electricity for plant equipment and the engine and exhaust heat are captured and used to heat the digesters.