SWANSEA — Last summer, when the Swansea Water District declared a water emergency, it was so bad officials worried that parts of town would literally run out of water.

It wasn’t the first time the Water District had declared an emergency because of water-supply woes, just the most recent.

The district may have found a permanent solution to what has become a chronic problem.

Yesterday, district Supt. Robert A. Marquis, town officials and others broke ground on a desalination plant that will take millions of gallons of saltwater from the Palmer River each day and turn it into clean drinking water.

The dignitaries stood on muddy ground off Vinnicum Road, and as they prepared to dig in their ceremonial gold-colored shovels, Marquis declared that the new facility would atone for past failures to fix the longstanding water shortage.

“Right now,” he said, “I’m anxious to turn the dirt and turn the tide.”

The plant would be the first such facility owned and managed by a municipality in the Northeast. A Spanish company is currently building a private desalination plant in North Dighton that will supply as much as a fifth of nearby Brockton’s drinking water.

The Swansea facility is expected to open in April 2009 and will cost an estimated $15 million.

It comes after three water emergencies in Swansea in the past eight years. Watering restrictions are still in place after the last emergency was declared in June and won’t be lifted until the end of next month.

Residential and commercial development is placing more and more pressure on the town’s supplies of groundwater. Officials recognized the potential problem as far back as the 1960s when they proposed creating a regional wastewater system with Somerset, but voters rejected the plan, Marquis said. In the 1970s, residents twice turned down a plan to build a municipal reservoir.

Since then, Swansea has grown from a predominantly rural community to a suburban one. Water usage has increased along the way. Because of more roads and paved lots, rainwater is being lost as runoff rather than seeping into the ground.

“Now, we suffer from reduced groundwater levels,” Marquis said.

A year ago, voters authorized borrowing up to a combined $18 million through a state revolving fund to lay pipes and build the plant and related facilities. The first pipes were placed soon afterward.

The water for the desalination plant will come from the Palmer River, which runs south from Rehoboth and is two miles away from the facility’s location.

Because water with a lower salt content is cheaper to purify, water from the river would be pumped to the 14,000-square-foot facility every day at low tide when the salinity level is at its lowest. Over six hours, the plant will take in 4 million gallons of water and will process it into 1.2 million gallons of freshwater.

The remaining 2.8 million gallons of water, which will have a higher salt content, will be discharged back into the river over six hours at high tide. The salinity level in the river is naturally higher then, so, as required by Massachusetts environmental regulations, the discharged water will not be any saltier than the river water at that time of day.

The Water District is in talks with the Massachusetts Highway Department to bury pipes to the river underneath the Route 195 median. If that proposal falls through, the pipes would run under local roads, Marquis said.

The Virginia-based HDR Engineering designed the facility, which will be built on five acres adjacent to Route 195. On Oct. 24, the construction contract was awarded to Waterline Industries Corporation, of Seabrook, N.H.

As the groundbreaking took place, a solitary backhoe cleared rocks and roots from the dirt lot. Cars whizzed by on the highway.

After the ceremony, Marquis looked around the property and saw potential.

“The mistakes aren’t being made today,” Marquis said. “This will be the end to Swansea’s water shortage.”

akuffner@projo.com