Conejo Wellfield Granular Activated Carbon Water Treatment Plant Project

Summary

SCH Number
2021080219
Lead Agency
Camrosa Water District
Document Title
Conejo Wellfield Granular Activated Carbon Water Treatment Plant Project
Document Type
MND - Mitigated Negative Declaration
Received
Present Land Use
Open Space/OS-40 (Open Space 40 acre)
Document Description
GAC is commonly employed as an adsorption media for the removal of a wide range of organic contaminants, including TCP, from drinking water. This treatment approach is currently being used at many drinking water treatment plants throughout the State. The water treatment benefits of GAC derive from the adsorption properties of the GAC material and the media’s high internal surface area, as opposed to filtration media, which captures contaminants between particles. Adsorption with GAC is a relatively “green” process in that the spent media is taken back by the supplier, captured contaminants are destroyed, and the carbon can then be reused in another treatment application. The proposed treatment system could be capable of reducing raw water TCP concentrations as high as 150 parts per trillion (ppt), much higher than current levels in the wells, and reduce TCP down to non-detectable levels. The Project proposes to construct a centralized GAC water treatment plant to remove the TCP from the water produced by the four potable water supply wells, which are all located near the Project treatment site (See Figure 3 5). The flow from the four wells supplying drinking water merges at the existing facility and combines before being sent to an existing storage tank and blending station for the reduction of nitrate levels. The new facility would intercept the flow from the wells, direct it through the GAC treatment process and return it to a new, water storage tank. The facility would require six 12-foot-diameter steel pressure vessels for the GAC media to treat the initial maximum flow rate of 2,350 gpm; however, the facility would be designed to accommodate the addition of another four vessels in the future, which could increase the overall treatment capacity to 3,150 gpm. The GAC media must be backwashed when it is first installed in the vessels and may need to be backwashed periodically once placed into service. The District intends to send this backwash water, which contains NSF-61 (drinking water contact) certified carbon fines and TCP levels comparable to the raw water to an equalization tank and then pump it into the District’s non-potable water distribution system. Because the water has high hardness (the simple definition of water hardness is the amount of dissolved calcium and magnesium in the water when heated, deposits of calcium carbonate can form) that may interfere with the GAC treatment, the District plans on reducing the pH of the water before it reaches the GAC using carbon dioxide and then raising the pH back up after treatment using sodium hydroxide. The existing well pumps would also need to be upgraded due to the additional pressure loss through the GAC system. In addition to the GAC treatment vessels, the facility would include a new treated-water tank, backwash equalization tank, non-potable water pumps, storm water detention basin, chemical feed systems, and other associated appurtenances. The Project would be capable of treating any combination of the wells at the same time including flow rates of up to 2,350 gpm initially (and up to 3,150 gpm should additional two vessel pairs ever be added) and would be designed to support a flow rate as low as 500 gpm in order to accommodate reduced speed pump operation during low demand periods, which typically occur late at night. Automated motor operated valves integrated with the site supervisory control and data acquisition (SCADA) system would be included at each vessel pair to make removing vessel pairs from service an automated process. The average volume of treated water expected to be produced is approximately 72 million gallons per month. The existing facility is approximately 0.5 acres, and the proposed new facilities would be approximately 2.5 acres. Specific Project components include: • Three pairs of GAC vessels (six total), expandable to five pairs of vessels in the future: 12-foot diameter; 18-foot tall; placed on a concrete foundation of 3,500 square feet; • Excavations for the foundation and infrastructure would occur up to approximately 5 feet in depth; • Backwash equalization tank: 126,000 gallons; 33 feet in diameter; 24 feet tall; ring wall footing; • Treated water storage tank: 85,000 gallons; 27 feet in diameter; 24 feet tall; ring wall footing; • Well pump replacements (four total): two 100 horsepower (hp) and two 125 hp; • Electrical service upgrade – to allow higher horsepower well pumps and non- potable pumps to operate; • Fixed standby generator; which will include an approximately 10,000-gallon diesel fuel tank for storage; • Chemical feed systems: One 5,000-gallon sodium hydroxide storage tank and feed system and one 14-ton carbon dioxide feed system; • One small diameter pipeline and electrical conduit between this main site and the existing Santa Rosa 8 well building to the south; • Piping, fittings, valves, and associated infrastructure; • Backwash (non-potable water) pumps: two 75 hp pumps; • Chain link fence: 8-feet tall with three strands of barbed wire; approximately 1,000 linear feet; and a new access gate off of Hill Canyon Road; and • Site surfacing of ag base under crushed rock; asphalt paved driveway with concrete pads at the offloading area for delivery trucks. • Total site improvements area: ˜ 108,000 square feet.

Contact Information

Name
Ian Prichard
Agency Name
Camrosa Water District
Contact Types
Lead/Public Agency / Project Applicant

Name
Dena Giacomini, Principal Planner, Environmental Project Manager
Agency Name
Provost & Pritchard Consulting Group
Contact Types
Consulting Firm

Location

Cities
Camarillo
Counties
Ventura
Regions
Citywide
Cross Streets
Santa Rosa Road
Zip
93012
Total Acres
2.5
Parcel #
520-018-024
Township
20N
Range
20W
Section
24&25
Base
MDB&M
Other Location Info
The Project is located in the community of Camarillo, in Ventura County, California, approximately 4.5 miles northeast of Moorpark and 6.2 miles south of Newberry Park. The Project is located along Santa Rosa Road on Assessor’s Parcel Number 520-018-024. The water treatment facility would be placed next to the existing drinking water facility as shown in Figure 2 3 of the CEQA document.
Other Information
The District operates potable, non-potable, and recycled water supply systems in southern Ventura County, California. The District’s service area encompasses approximately 31 square miles. The potable water system serves roughly 32,000 people and delivers approximately 15,000 acre-feet of water each year through more than 8,500 service connections in portions of the cities of Camarillo, Moorpark, and Thousand Oaks and unincorporated Ventura County. The District’s potable water system is regulated by the State Water Resources Control Board (SWRCB), Division of Drinking Water (DDW) as a community water system. In 2018, the State Water Board implemented a new maximum contaminant limit (MCL) for 1,2,3,–Trichlorpropane (TCP), a synthetic organic compound that was an impurity in certain soil fumigants used in agriculture, of 5 ppt. Upon testing, it was discovered above the MCL in three of the wellfield’s four wells, which were promptly removed from service. The fourth well was taken offline in early 2020. After an initial, ultimately unsuccessful attempt to resolve the TCP issue with blending, which turned out to be an ineffective strategy due to the very low MCL for TCP and the District’s inability to meet its blend plan objectives, CWD is now constructing a granular activated carbon (GAC) treatment plant to treat for the TCP. The plant is expected to be completed in FY2021-22. The wellfield will remain off until that time. (See Figure 3 5) The District has decided to move forward with a centralized 2,350-gallons per minute (gpm) GAC treatment plant to remove TCP from the Conejo 2, Conejo 3, Conejo 4, and the Santa Rosa 8 wells so that the wells can be returned to service.

Notice of Completion

Review Period Start
Review Period End
Development Types
Water Facilities (Water Treatment)(Type Water Treatment, MGD 72)
Local Actions
Other
Project Issues
Biological Resources, Cultural Resources, Hazards & Hazardous Materials, Tribal Cultural Resources, Wildfire
Reviewing Agencies
California Air Resources Board (ARB), California Department of Conservation (DOC), California Department of Fish and Wildlife, South Coast Region 5 (CDFW), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Transportation, District 7 (DOT), California Department of Water Resources (DWR), California Energy Commission, California Highway Patrol (CHP), California Native American Heritage Commission (NAHC), California Natural Resources Agency, California Regional Water Quality Control Board, Los Angeles Region 4 (RWQCB), Department of Toxic Substances Control, Office of Historic Preservation, State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Division of Drinking Water, District 6, State Water Resources Control Board, Division of Water Rights, State Water Resources Control Board, Divison of Financial Assistance

Attachments

Notice of Completion [NOC] Transmittal form

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