Along the coast in California’s Santa Barbara County, Carpinteria Valley is a region known for its beaches and avocado orchards. The Carpinteria Valley Water District (CVWD) is responsible for providing potable water through 90 miles of distribution pipeline to nearly 16,000 people. With the unpredictability of surface water supply and lengthy time for groundwater recharge, CVWD has partnered with the Carpinteria Sanitary District (CSD) to establish the Carpinteria Advanced Purification Project (CAPP), which will provide a locally managed and controlled water supply, even during times of prolonged drought and water supply shortages.
CVWD currently relies on three water sources to meet its service area demand. The bulk of CVWD’s supply comes from the Cachuma Project, drawing an allotted 2.5 million gallons per day (MGD) from Lake Cachuma plus 356,000 gallons per day (GPD) due to an exchange with the Santa Ynez Water Conservation District. CVWD is allotted an additional 1.8 MGD from the California State Water Project, but the supply reliability varies based on drought conditions. The third source also varies based on available groundwater from the Carpinteria Valley Groundwater Basin, with average pumping at 2.0 MGD. In theory, the Cachuma Project and State Water Project constitute three-quarters of the district’s supply. However, in addition to drought, factors such as competing demands and seismic activity can impact supply availability. During the recent extended drought, these two supply sources met roughly one-quarter of CVWD’s demand.
CAPP, which is expected to be operational in 2028, will provide one-quarter of CVWD’s supply to close that demand gap and remove climate impacts and other factors from the variability of this resource. Woodard & Curran was hired by CVWD to conduct a feasibility study and prepare environmental documentation, preliminary design services, and final design of the 1.2 MGD advanced water purification facility located at CSD’s wastewater treatment plant. The treatment process includes equalization tank, microfiltration, reverse osmosis, and an advanced oxidation process. The design also includes a purified water pump station, 6,100 feet of 10-inch conveyance pipeline from the purified water pump station to a well lateral split point, 2,000 feet of 8-inch conveyance pipeline from the well lateral split point to two individual injection wells, and two 14-inch-diameter injection wells with backwash pumps. Our scope of services also includes final design of the injection wells and three sets of monitoring wells. Once the CAPP is complete, it will capture 100 percent of CSD’s valuable effluent previously discharged to the Pacific Ocean and utilize it to replenish the Carpinteria Valley Groundwater Basin, creating a reliable and sustainable water source.
Since CAPP is the first of its kind potable reuse project, the design team faced several challenges that required creative solutions while tailoring the CAPP design. The new advanced water treatment facility will capture 100 percent of effluent from CSD. Secondary effluent from the processes will be diverted to a buried 200,000-gallon equalization tank for reuse by CAPP through its reverse osmosis (RO) trains, ramping up or down depending on flowrates. From an operational standpoint, there were concerns whether CSD’s chlorine contact basin could handle seasonal peak wet weather flows or CAPP downtime. Based on this operational feedback, the design team adjusted sampling locations to keep critical chlorine residual and oxidation-reduction potential (ORP) equipment wet year-round and operational. In order to maintain plant water flows to the existing primary and secondary treatment systems, additional plant water pumps were constructed in the equalization tank as the existing pumps draw off the chlorine contact basin which will be empty 95 percent of the year.
The project site also prompted the design team to consider climate resiliency measures, especially considering the area is already prone to coastal flooding. While the preliminary design called for raising all critical infrastructure on to elevated pads, concerns were raised about Carpinteria’s building height requirements, the added expense, and the lack of flood proofing around the rest of the facility, including the electrical room and electrical transformers. To address these concerns, the final design incorporates a passive flood gate at CSD’s main entrance to protect the entire facility, including CAPP, from flood risks.
In addition to designing with plant resiliency in mind, obtaining necessary permanent easements proved to be a major hurdle for the project. One specific challenge included losing a key site for an injection well and backwash storage tank, which required the team to devise a creative alternative. Based on our experience working with the cities of Malibu and Oceanside, the project team opted to place the injection wellhead within a city right-of-way in a buried vault. Furthermore, the team considered public input on the preliminary design and adjusted the need for an above-grade 42,000-gallon backwash tank. The final design includes an oversized buried piping network to avoid additional land acquisition for the tank footprint and eliminate any visual impact a tank of that size would have caused. This approach also allows backwash to be sent back to CSD’s sewer system and CAPP for groundwater recharge instead of discharging to the nearby creek.
The success of this project has hinged on a collaborative partnership between Woodard & Curran, CVWD, CSD, and the community. Woodard & Curran facilitated workshops between CVWD and CSD, resulting in a memorandum of understanding for project ownership and operation. District staff will split and track their time between the wastewater treatment and advanced water treatment facilities under this memorandum. As such, CSD supported their existing operations staff in the process of obtaining their AWT Grade 3 certification.
In addition to the partnership with CSD, the project team helped CVWD with public outreach and education. CVWD launched a website for CAPP with the option for the public to register for newsletter updates. This website explains in layman’s terms what the project is, the difference between indirect and direct potable reuse, and impact the community may experience during construction. CVWD leveraged a series of meetings, as well as mailings, press, and social media updates, to further educate area residents and encourage public input. The project’s Environmental Impact Report is available on CVWD’s website, assuring the community of minimal impacts during construction.
Woodard & Curran provided regulatory and permitting support for CAPP with the Division of Drinking Water, Regional Water Quality Control Board, and CEQA. A unique aspect of CAPP was ocean plan compliance for discharge of 100 percent RO concentrate with no dilution of secondary effluent. Additionally, the team successfully obtained permitting from the California Coastal Commission, which requires a 50-foot setback from Carpinteria Creek for all permanent infrastructure, including buried pipelines.
The anticipated construction capital cost of $53 million once CAPP is complete, among all its bid packages, will be paid for through a combination of state and federal grants and loans, as well as water user rate revenue. Woodard & Curran assisted CVWD’s pursuit of a low-interest loan by providing a 50 percent design of the project, and helped prepare grant and financing applications, including an opportunity with the U.S. Bureau of Reclamation. There are continued efforts to source funding, thereby minimizing any rate increases passed on to customers.
Woodard & Curran partnered with Carollo Engineers, Inc. for support on the Advanced Water Purification Facility process and Pueblo Water Resources, Inc. for support on the injection and monitoring wells drilling and construction.
In addition to the project team listed below, the following Woodard & Curran employees provided critical input on this project:Sally Johnson, Project Manager (permitting); Donna Rammell, Senior Technical Manager (electrical advisor); Kris McAlpine, Technical Manager (electrical lead); Jon Havrilesko, Technical Manager (structural lead); Erika Wilson, Project Engineer (conveyance lead); Elisa Lee, Project Engineer (NPDES permitting); Robert Speyrer, Project Engineer (controls lead); Brian Ling, Engineer (civil/mechanical support); Kyle Tracy; Senior Delivery Specialist (controls advisor); Mike Matson, Senior Delivery Leader; Kris Rosner, Cost Estimator; Christy Kennedy, Client Manager; and Tom Richardson, Principal in Charge.