Delta Diablo (District) prioritizes the repair and replacement of its equipment and facilities via a comprehensive Capital Improvement Program (CIP).  This reflects strong fiscal responsibility ensuring successful, long-term rehabilitation of our infrastructure and investment of ratepayer funds to provide essential community wastewater services to residents and businesses in Antioch, Bay Point, and Pittsburg.

Secondary Process Improvements 

The Secondary Process Improvements Project has been implemented to address aging infrastructure at the wastewater treatment plant, add secondary treatment capacity for population growth in the service area, and to incorporate advanced nutrient removal technologies into the plant processes. The project is strategically divided into two phases to ensure expeditious completion of near-term facility needs while allowing time to better align the overall project goals with the emerging nutrient removal regulations being developed over the next five years. The initial phase will focus on decommissioning the aging trickling tower filters and construct additional aeration basins to ensure reliable secondary treatment. To support these improvements, ancillary facilities including a secondary clarifier, blower building and pumping stations are also to be constructed. These facilities not only support the Phase 1 infrastructure but are designed to seamlessly integrate with the nutrient removal facilities planned for the future expansion. The second phase of construction will include additional deep well aeration basins and the repurposing of the existing aeration basins to optimize their functionality within the nutrient removal processes.

CEQA Environmental Review for the Secondary Process Improvements

The District is currently seeking public comments on the Draft Initial Study/Mitigated Negative Declaration for the Secondary Process Improvements Project.  The public may review and provide comments on this document from August 21, 2024 to September 20, 2024. The District anticipates adopting the Mitigated Negative Declaration at its Board of Directors Meeting on November 6, 2024

Notice of Availability and Intent to Adopt a Mitigated Negative Declaration.pdf

Draft Initial Study/Mitigated Negative Declaration.pdf

Point of Contact:  Sean Williams, Associate Engineer, seanw@deltadiablo.org 

Project Status: Design

Anticipated Start of Construction: Spring 2026

Estimated Construction Cost: $80M-$115M

Recycled Water Master Plan & RWF Condition Assessment

The District initiated the Recycled Water Master Plan & RWF Condition Assessment Project to develop an integrated, strategic planning focused guidance document with in-depth analysis in key areas to inform RWF infrastructure investment decisions in the near and long term. In addition, the project will focus on: 1) conducting a condition assessment of all recycled water production and distribution facilities and assets to determine replacement and rehabilitation needs along with estimated costs, 2) identifying potential new recycled water customers and associated recycled water distribution system infrastructure investment needs, including development of an updated hydraulic model, 3) identifying, evaluating, and recommending potential recycled water quality improvement opportunities associated with expanded recycled water use, 4) identifying, evaluating, and recommending potential strategies to reduce effluent nutrient loading to receiving waters via expanded recycled water use for irrigation purposes, and 5) identifying applicable grant or low-interest loan programs at the local, state, and federal level to support implementation of future capital projects and recycled water program expansion.

Point of Contact:  Thanh Vo, Senior Engineer, thanhv@deltadiablo.org

Project Status: Planning

Cogeneration System Improvements

The District operates an existing cogeneration system at the Wastewater Treatment Plant capable of generating heat for the anaerobic digesters as well as producing energy to reduce the amount of power needed to be purchased from the grid to run the plant. The existing gas treatment system and cogeneration engine are nearing the end of their useful life and require replacement. The Cogeneration System Improvements project will include the replacement of the existing cogeneration engine and gas conditioning equipment as well as upgrades to electrical and control infrastructure. The project is eligible for federal tax credits for the District under the Inflation Reduction Act, but specific requirements must be met by both the District and Contractor under the IRS regulations regarding labor, scheduling, and domestic content to maintain the integrity of the Inflation Reduction Act. Projects like the Cogeneration Systems Improvement project are instrumental in enhancing the District’s resource recovery capabilities and promoting more efficient and reliable performance.

Point of Contact:  Stephen Cardiel, Associate Engineer, stephenc@deltadiablo.org

Project Status: Construction

Antioch Pump Station and Conveyance System Improvements

The District established the multi-year Antioch Pump Station and Conveyance System Improvements Project to assess the Antioch Conveyance System, which consists of two 24-inch force mains (i.e., AFM 101 and AFM 102). The initial phase will identify portions of the force mains that need to be repaired immediately to ensure near-term operational reliability. The future phases will include conducting design activities related to the Antioch conveyance system, including the Antioch and Bridgehead pump stations, to develop a major project to address deficiencies in these systems to ensure long-term operational reliability. The District is currently pursuing the development of an alternative project approach (e.g., progress design-build) to mitigate project risks and potentially accelerate the overall project completion schedule. The estimated project cost has been updated to $22.0 million in the District’s new 5-year Capital Improvement Program for FY24/25-FY28/29.

Point of Contact:  Thanh Vo, Senior Engineer, thanhv@deltadiablo.org

Project Status: Planning (Predesign)

Anticipated Start of Construction: Summer 2026

Estimated Construction Cost: $15M-$20M

Manhole, Gravity Interceptor, and Easement Road Improvements Phase 2

The 2020 Final Report for the Facility Condition Assessment Project identified the assets associated with the Shore Acres Interceptor system as a high priority. Failure of this system with limited site access can lead to sanitary sewer overflows and potential adverse public health and environmental impacts due to insufficient and/or unreliable conveyance capacity. As a result, in 2022, the District initiated the multi-phase Manhole, Gravity Interceptor, and Easement Road Improvements Project to address infrastructure needs, conduct sewer condition assessment, and improve access to critical assets in the Shore Acres Interceptor system. Phase 1, currently in construction, primarily involves planning, designing, and constructing of approximately 30 critical manholes and rehabilitating approximately 200 feet of 20-inch reinforced concrete pipe (RCP) and 650 feet of 30-inch RCP using structural cured-in-place (CIPP) liner. The Project is the next phase of the Phase 1 project that will address the remaining infrastructure needs in the Shore Acres Interceptor System and also include the evaluation and rehabilitation of the Willow Pass Interceptor and the two junction structures located at the intersection of Arcy Lane and the Pittsburg-Antioch Highway near the entrance to the District’s WWTP. The District’s new 5-year Capital Improvement Program (CIP) for FY24/25-FY28/29 will include the $11.0 million Phase 2 project.

Point of Contact:  Thanh Vo, Senior Engineer, thanhv@deltadiablo.org

Project Status: Planning (Predesign)

Anticipated Start of Construction: Summer 2026

Estimated Construction Cost: $8M-$10M