A new 2.1 million-gallon water tank now sits atop Carter Hill above Half Moon Bay, replacing two steel tanks that had served the region since the 1950s. The $12 million project was completed in June, according to the Coastside County Water District. The tank is expected to remain in service for 60 to 100 years.
U.S. Representative Sam Liccardo marked the occasion on social media, writing, “Congratulations to the Coastside community on the Water District’s successful launch of a water tank that will serve Coastside for generations,” in a post on X
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The board awarded the construction contract in July 2024. The project replaced two smaller steel tanks from the 1950s. The new tank measures 97 feet in diameter and 55 feet tall, and uses 21 miles of prestressing wire.
Why Prestressed Concrete Over Steel
The board awarded the primary $10,968,951 construction contract to DN Tanks, LLC in July 2024, waiving competitive bidding because project designer HDR, Inc. had engineered the prestressed concrete structure specifically around DN Tanks' proprietary construction methods, according to Coastside Buzz. The concrete design is built to withstand earthquakes and the outward pressure of stored water, and it requires less upkeep than steel, which typically needs recoating every 20 years. The design was also assessed in an 80-year lifecycle-cost comparison with steel.
Engineering and construction management firm Freyer and Laureta, Inc. oversaw construction, working directly adjacent to the district's Nunes Water Treatment Plant. The firm had previously managed an $8.6 million modernization project at the Nunes plant, per its own water resources page.
Fire Protection
The new tank's added capacity supports fire protection.
Aging Tanks Drove the Push
The two steel tanks at Carter Hill that were replaced were built in the 1950s, Coastside News reports. The district formed in 1947 and serves 7,700 connections and about 19,000 people.
The district financed the project with $8 million in COP proceeds.
District Storage Planning
A 1.5-million-gallon Half Moon Bay Tank #3 was built in 1963. The district authorized EKI Environment and Water, Inc. to prepare its Potable Water Storage Master Plan.
In March, U.S. Representative Liccardo submitted a $500,000 Fiscal Year 2027 federal Community Project Funding request to support engineering design and environmental permitting for that next phase, according to a letter filed with the U.S. House of Representatives. The completion also comes as General Manager Mary Rogren prepares to retire in March 2027 after leading the district since 2019, prompting the board to engage executive search firm Alliance Resource Consulting in mid-2026 to begin recruiting her replacement.
Coastside County Water District is one of 26 public agencies belonging to the Bay Area Water Supply and Conservation Agency, which collectively purchases water from the San Francisco Public Utilities Commission to serve roughly 1.8 million residents across San Mateo, Santa Clara and Alameda counties, according to BAWSCA. The Carter Hill project reflects a broader pattern among Northern California water utilities working to replace seismically vulnerable, mid-20th-century steel tanks before they reach the end of their service life.
