Antioch Brackish Water Desal Project
Antioch’s Need for Desalination
The City of Antioch’s current water supply system serves over 112,000 people within a 28.8 square-mile service area. The main sources of water for the City include water pumped from the San Joaquin River under the City’s senior (pre-1914) water right, and purchases from the Contra Costa Water District. The amount used from each source depends on the time of year and the type of year (dry or wet). The City uses river water as much as possible because it is less expensive than water purchased from CCWD. However, over the years the salinity of river water has increased steadily and forced the City to purchase more water from CCWD. The graph (below) shows the water supply trend.
To improve water supply reliability and operational flexibility while saving costs, especially during droughts and future changes in Delta water management, the City is implementing the Brackish Water Desalination Project. The Project will allow the City to use water from the river year-round, even when the salinity is above levels normally treated at the existing conventional Water Treatment Plant.
The main Project objectives include:
- Improve water supply reliability and water quality for customers.
- Develop a reliable, and drought-resistant water source to reduce dependency on purchased water supplies by maximizing the use and preserving the value of the City’s pre-1914 water rights.
- Maximize the use of existing infrastructure to minimize capital costs .
- Provide cost effective operational flexibility to allow the City to respond to changes in source water quality, emergencies, and changes in climate and California Bay-Delta conditions.
What is Brackish Water Desalination?
Desalination is the process of removing minerals and salts from water to produce a purified water. This is achieved by pushing water at a high pressure through reverse osmosis (RO) membranes (semipermeable membrane) to remove salt and other minerals.
The source water for desalination can come from a variety of sources including seawater, agricultural run-off, salty groundwater, or other brackish water sources. Brackish water refers to water that has higher concentrations of chlorides (salinity) and total dissolved solids (TDS) than freshwater, but is not as salty as ocean water. Ocean water has approximately 35,000 mg/L of TDS, while brackish water can range from 1,000 to 10,000 mg/L of TDS.
At certain times of year, the waters near the City of Antioch are considered brackish when San Joaquin River flows decrease and the salty Bay waters reach further upstream. Because brackish water has lower concentrations of TDS and nitrates, less energy is needed to push the water through the RO membranes. Brackish water desalination can produce potable water supply at less than half the energy usage of seawater desalination.
The Antioch Brackish Water Desalination Project utilizes existing infrastructure to the degree possible and also includes new facilities and infrastructure to improve the City’s water supply reliability and operational flexibility. The completed desalination facility will have a capacity of 6 million gallons per day, producing up to 5,500 acre feet per year (ac-ft/yr) which will offset purchases of more expensive CCWD water.
City of Antioch’s Brackish Water Desalination – Project Components
The Antioch Brackish Water Desalination Project consists of the following components:
- New river intake pump station to replace the existing San Joaquin River intake pump station. The pump station will consist of three 8 mgd pumps (16 mgd firm capacity) each with a fish screen that meets the protective criteria of the California Department of Fish and Wildlife and National Marine Fisheries Service.
- New 3,000 foot pipeline connecting the City’s existing raw water pipeline to the City’s Water Treatment Plant to allow a direct connection and maximize the use of existing infrastructure
- New 6 mgd desalination facility (reverse osmosis, post-treatment systems, chemical feed and storage facilities, brine conveyance facilities, and other associated non-process facilities).
- Approximately 4.3 miles of a new brine disposal pipeline to convey discharge brine the Delta Diablo Wastewater Treatment Plant for disposal into the San Joaquin River through an existing outfall. Discharge of brine water into the San Joaquin River will result in minor local increases in salinities that are within the tolerance range of native species.
Existing facilities that are utilized in this project include the:
- Existing raw water pipeline – to convey river water to the treatment plant.
- Existing Water Treatment Plant – to provide pretreatment of the raw water before reverse osmosis instead of constructing a new microfiltration facility.
- Existing Wastewater Treatment Plant effluent water – will be blended with discharge brine to reduce the salinity and meet river discharge requirements.
- Existing Wastewater Treatment Plant Outfall – used to convey brine water to the San Joaquin River.
The Project facilities will predominately be located in the City of Antioch, California. The desalination facility will be located within the fence line of the City’s existing water treatment plant at 401 Putnam Street, Antioch and the pipeline routes will follow road right-of-ways. The brine will be conveyed to the Delta Diablo Wastewater Treatment Plant in Pittsburg, CA and then discharged to the San Joaquin River west of the Dow Wetlands Preserve using the existing WWTP outfall.
Water treated at the City of Antioch’s Brackish Water Desalination Facility will enter the City’s drinking water distribution system and benefit all residents who receive water from the City of Antioch, approximately 112,000 people.
Project Cost and Financing
The total capital cost of the Project is approximately $63 million which will be financed through a variety of sources. Potential sources include the EPA Water Infrastructure Finance and Innovation Act (WIFIA) loan, the Department of Water Resources Proposition 1 Desalination Grant, a State Revolving Fund loan, and the City of Antioch’s Capital Improvement Budget.
- 2017 08 08 Update – Initiate Environmental
- 2017 08 15 NOP Filed with County Clerk
- 2018 10 25 NOD Filed with County Clerk
January 26, 2016
- 2016 01 26 Minutes
- 2016 01 26 Resolution Auth $1 Mil SRF Loan with SWRCB
- 2016 01 26 Staff Report Auth SRF $1 Mil Loan App with SWRCB & Reso
April 12, 2016
- 2016 04 12 Minutes
- 2016 04 12 Resolution Pledge Revenues
- 2016 04 12 Staff Report Pledged Revenue Funds & Designate City Mgr & Reso
July 25, 2017
- 2017 07 25 Minutes
- 2017 07 25 Resolution Auth $10 Mil Grant App with DWR
- 2017 07 25 Staff Report $10 Mil DWR Grant App & Reso
August 8, 2017
September 5, 2017
December 12, 2017
June 26, 2018
- 2018 06 26 Minutes
- 2018 06 26 Resolution Auth App for SRF Loan
- 2018 06 26 Staff Report $55 Mil Loan App to SWRCB
July 24, 2018
- 2018 07 24 Minutes
- 2018 07 24 Resolution (Reimb) SWRCB SRF $55 Mil Loan
- 2018 07 24 Staff Report Reimb Reso $55 Mil SWRCB Loan App
August 1, 2018
- 2018 08 01 Minutes from PC
- 2018 08 01 Power Point DEIR Comments for Planning Commission.pptx
- 2018 08 01 Staff Report to PC for Draft EIR
August 14, 2018
- 2018 08 14 Minutes
- 2018 08 14 Resolution USBR WIIN Grant
- 2018 08 14 Staff Report USBR WIIN $15,750,000 Grant App
October 9, 2018
October 23, 2018