NEWPORT — Julia Forgue gazes out at the slowly curling, blue waves as they crash ashore at Easton’s Beach, a broad expanse of sandy shoreline with a carousel and large pavilion, all in view of the Cliff Walk and the city’s illustrious mansions.

It’s a jewel of a beach, right in the heart of this tourist mecca. But on a handful of days every summer, pollution levels spike and state health officials order it closed to swimming.

The primary culprit is a stream close to where Forgue, the city’s public utilities director, stands. It lazily flows past her, trickling over the sand and into the surf. After heavy rains, runoff from miles and miles away rushes down the stream, contaminating the beach with bacteria from animal waste.

Easton’s woes contributed to a lawsuit brought against the city last year by environmentalists. Now the city is recommending an unusual solution to the problem: a $5.1-million mini-plant to treat the runoff with ultraviolet light.

“We have no other viable options,” Forgue says.

The project, which employs old disinfection technology in a new way, has already received a $2.5-million state grant. But the project still has its skeptics.

Some wish the city could have found a “greener” solution to the problem, one that would allow runoff to be filtered naturally. Some complain that the facility wouldn’t be able to handle the strongest storms and that the plan doesn’t address all the sources of bacteria that reach the beach.

“We could have a UV system and the beaches are still closed,” said David McLaughlin, a member of an ad-hoc city commission on wastewater and storm water issues and a surfer who founded Clean Ocean Access, a volunteer group that monitors water quality at Easton’s and other area beaches.

WHEN FUSS & O’NEILL began studying how to deal with the storm water problem at Easton’s, the Providence engineering firm took its usual approach of “let’s look at every potential way we can handle this,” said vice president Dean Audet. Even so, when one of the engineers suggested the idea of ultraviolet treatment, it struck the rest of the staff as a bit wacky.

“We were sort of making fun of her,” Audet admitted. Ultraviolet light is commonly used in large plants to disinfect wastewater and drinking water, he said, but “it’s an innovative use to apply it to runoff.”

Audet knows of only a few similar installations, including a couple in California. Newport, it turned out, presented challenges that also made it suitable for such UV treatment.

The source of Easton’s pollution is a manmade stream that locals call the “moat.” It runs around the perimeter of the built-up earthen sides of Easton Pond, a reservoir across the street from the beach, and was originally designed as a spillway for the dams serving the pond. Today, storm drains from neighborhoods extending all the way toward Broadway discharge into the moat. Less than a foot deep in dry weather, but a couple feet deeper during storms, it flows south, beneath a small bridge at Memorial Boulevard and out to Easton’s Beach. Near the bridge, the Middletown fork of the moat meets the Newport branch.

Audet said his team explored “greener alternatives,” such as creating a landscaped area where runoff could be sent and then submerged underground to be filtered naturally. A similar idea involved constructing a wetland to filter the water before it flows to the beach.

The wetland concept would have required 10 acres where there is virtually no such space, unless the reservoir were to be reduced in size. And the soils are not very permeable, making underground filtration impractical, unlike a similar project Fuss & O’Neill is working on at the Narrow River in Narragansett.

Once UV treatment emerged as a practical option, the city undertook a pilot project, using trailer-mounted UV equipment near the beach. It demonstrated the technique could effectively kill bacteria in the runoff.

Earlier this month, the state Department of Environmental Management awarded Newport a $2.5-million grant (from a $70-million environmental bond) that the city will match with a low-interest loan from the state Clean Water Finance Agency. Since it’s not “shovel-ready,” Forgue said, the project is not eligible for federal economic stimulus funds.

On Wednesday, the City Council awarded a $478,000 contract to Fuss & O’Neill that includes completing the final design of the plant. The project will then go out to bid, with construction possibly beginning this year.

WHILE BATHERS at Easton’s lather on sunscreen to fight the damage ultraviolet light does to skin, the city will be going to great effort to beam intense doses of the very same light at runoff bound for the beach.

Preliminary plans call for a gate to automatically drop down into the moat, on the reservoir side of Memorial Boulevard, during heavy rain. The water will then be pumped through an uncovered, U-shaped concrete channel. First, a screen will remove any large objects. Then the water will flow under a series of long, skinny UV lights.

“It almost looks like a fluorescent light bulb,” said Audet.

The water, which only requires a few seconds of exposure, will then be returned to the moat and flow to the beach.

The entire facility, which will include a small building housing controls, will be able to handle 1.2 inches of rain in a 24-hour period, or 93 percent of all storms. It’s expected to kick into operation for 54 storms a year.

“The idea is to treat the first flush, when you get that first rush of bacteria,” Forgue said.

The UV facility will cost an estimated $200,000 to $400,000 a year to run, most of which will be spent on electricity to power the light.

Forgue said the city hopes that Middletown and the state, both of whose pipes contribute about 20 percent of the runoff to the beach, will eventually agree to help finance the facility. But the city — pressured to curb its harbor and beach discharges by EPA storm water regulations, the federal lawsuit brought by two environmental groups and four citizens and the desire to protect Easton’s reputation — is pressing on without any such commitments.

“We have a meeting with them planned for later this month,” said Mayor Jeanne-Marie Napolitano. In the meantime, she said, “We’re taking this on ourselves.”

ONE OF THE citizen activists who sued the city hasn’t bought into UV as the solution at Easton’s Beach.

“The UV plant is very expensive and there is no guarantee that it will keep the beaches open during major rain events,” said Peter Fagan. “A natural system is preferable to an expensive mechanical system requiring maintenance and a lot of electricity to run. By ignoring the sources of the pollution — outfall pipes, storm drains, filthy streets, animal waste, construction sites, parking lots — we are trying to treat the symptoms of the problem and not the causes.”

He also called it a “fool’s errand” to go ahead without Middletown’s involvement in the plant. McLaughlin, founder of Clean Ocean Access, echoed his concern, noting that a pipe off Esplanade Road in Middletown discharges onto the beach, not far from the moat, and is not addressed by the UV facility. In its monitoring program, his group repeatedly found unsafe levels of bacteria in the area of the moat and the Esplanade pipe, even during dry weather.

“This really begs the question,” said McLaughlin, of whether the beaches will still have to be closed regardless of “how effective UV will be.”

Middletown Town Administrator Shawn J. Brown emphasized that his community is “100 percent committed” to keeping the beach open. But Fuss & O’Neill determined that the Esplanade pipe could not be tied into the UV facility because it would cause flooding. The town also studied, and then rejected, extending the pipe far out into Easton Bay.

Middletown, said Brown, is not yet prepared to join in the UV project because it hopes to find something “more cost effective than treating the water with energy.” The town has hired a consultant to study ways to prevent contaminated runoff from reaching the moat and the Esplanade pipe.

“The approach the town is taking is to first look upstream,” he said.

Middletown, he said, might eventually consider small-scale UV treatment near the end of the Esplanade pipe.

rsalit@projo.com