PROVIDENCE, R.I. Like some advanced race of moles, crews are boring a 3-mile-long tunnel under Rhode Island's capital city to capture raw sewage that is now jettisoned into waterways during heavy rains, often forcing authorities to close shellfish beds that are a lifeblood of the commercial fishing industry.
All it takes is a half-inch of rain to overwhelm the aged combined sewer and stormwater system some segments 134 years old that serves 360,000 residents of metropolitan Providence.
To relieve the backup, the contaminated water is released into local rivers, such as the Blackstone, Moshassuck, Providence, Seekonk and Woonasquatucket rivers. Those empty into Narragansett Bay, fouling the water with fecal coliform bacteria that effectively closes the shellfish beds.
The $318 million Combined Sewer Overflow Abatement project by the Narragansett Bay Commission is Rhode Island's effort to stem the spills and clean the water. It's also the state's largest public works project to date.
Work on the first phase began in May 2001 and is scheduled to be completed in spring 2008. Two other phases are planned, which would involve building another miles-long underground tunnel.
Scientists agree that the project will greatly reduce dangerous bacteria from local waters, but don't think it will meet federal requirements so the water can be used to fish and swim.
"I would definitely not say outright this will make (the bay) fishable, swimmable, but this is certainly a major step, the major step," said Ames Colt, assistant director with the Rhode Island Sea Grant College Program, a partnership among federal and state agencies and universities to research marine issues.
The fishing and swimming mandate comes from Congress and is the reason why the commission looked at the problem in the first place. Boston, Chicago, Portland, Ore., and Milwaukee each has shared sewer and stormwater pipes, and all have opted to construct tunnels to capture excess wastewater.
Atlanta, Detroit, St. Louis and Washington plan similar, multibillion-dollar projects.
"It is an excellent solution, a proven technology," said Alexandra Dunn, general counsel for the Association of Metropolitan Sewerage Agencies in Washington.
There are 745 communities in the United States with combined sewer systems, most of them older cities concentrated in the Northeast and Great Lakes regions, said Jim Hanlon, director of the office of wastewater management at the Environmental Protection Agency. As of July, about 59 percent of those municipalities adopted solutions and are starting construction, he said.
Newer communities have separate sanitary sewer and stormwater systems.
In Rhode Island, the tunnel under construction will stretch from the Field's Point wastewater treatment plant to a foundry complex just west of downtown. Its route roughly follows existing pipes along the Providence and Woonasquatucket rivers, then branches out under the south lawn of the Statehouse before ending at the foundry complex, where one of the most active outfall pipes is located.
Engineers will close the outfall points and connect them to the current combined sewer network. The crews also will build "drop shafts" that will carry the excess wastewater downward to the new tunnel. The wastewater will be held in the 30-foot diameter tunnel, lined with concrete, until the Field's Point plant can process it.
Environmental officials estimate about 2.2 billion gallons of untreated water is released annually into local rivers. The tunnel will be able to hold up to 65 million gallons, good enough to hold overflows except in the heaviest rains, expected about four times a year.
While ridding the water of disease-carrying bacteria, the project is expected to allow shellfish beds in upper Narragansett Bay to open for longer periods, welcome news to an industry crippled by the pollution's effect.
The state Department of Environmental Management closes as many as 11,000 acres in the upper bay when rainfall exceeds a half-inch, based on water quality standards set by the EPA. Those grounds are the most fertile in the entire bay, holding about 70 percent of the shellfish harvest, according to Art Ganz, supervising biologist in the Fish & Wildlife division at the DEM.
"If you're a (shellfisherman), you need to have those grounds," said Michael McGiveney, a shellfisherman from North Kingstown and president of the Rhode Island Shellfishermen Association.
The bay generates tens of millions of dollars to the 300 or so shellfishermen who work the beds, according to the DEM.
Everyone agrees the project will allow the beds to be open for longer periods. That means even shellfish in the polluted areas can be harvested, since they constantly filter water. What's unknown is how much longer the beds will be open than before. Once the first phase of the project is completed, work will be halted for at least two years so scientists can analyze how much the water has improved.
Two more phases are planned after that, and total cost for the project could reach $1 billion, said Jamie Samons, the bay commission's spokeswoman.
By the end of the project, possibly in 2020, the water would be clean enough for fishing and swimming, she said.
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