With scores of new customers and a broad swath of North Monterey County brought under its wing, the Pajaro-Sunny Mesa Community Services District is ready to proceed with its plan for a desalination plant in Moss Landing.

District officials say they hope to get a hearing before the California Coastal Commission this summer for a pilot project.

It's all part of the district's plan to ensure a reliable and safe supply of drinking water for 7,000 customers in an area that stretches from Moss Landing to Prunedale, officials say.

"Our problem is we're 100 percent dependent on groundwater," said Marc Del Piero, the district's lawyer. "We're looking to fix the problem."

Underground water supplies are shrinking after decades of pumping more than is replaced by annual rainfall. Part of the district lies in the Pajaro Valley, where dropping freshwater levels have allowed seawater to infiltrate some coastal wells. Elsewhere in the district, wells have been contaminated with nitrates and arsenic.

Del Piero and general manager Joe Rosa started talking about desalination 15 years ago, but at an estimated $3,500 an acre foot of water -- roughly 326,000 gallons or enough to supply three average households for a year -- the cost was too high.

But since then the price has come down by about two-thirds, Del Piero said, and the opportunity to import water from outside the county has dried up. He estimates the district will be able to deliver desalinated water to residential customers for about $400 a year.

The addition of five small water systems through a purchase agreement approved by a federal judge Tuesday nearly doubled the district's customer base and will help spread the cost of the project.

The district's proposed pilot project follows two others: one by California American Water at the Moss Landing Power Plant and another at the UC Santa Cruz-Long Marine Lab, a joint project of the city of Santa Cruz and the Soquel Creek Water District.

For project management, the district has tapped Poseidon Resources Corp., which recently won conditional approval from the coastal commission to build a desalination plant to serve 300,000 people in San Diego County.

That success has encouraged Pajaro-Sunny Mesa officials, who say similar environmental issues have been raised regarding their project.

Tom Luster, an environmental scientist with the coastal commission, agreed some of the issues are the same. But, he said, each project is site specific. One issue for Pajaro-Sunny Mesa is the proximity to Elkhorn Slough. "We handle each facility on a case-by-case basis," Luster said. "Each one raises different issues."