Having nearly completed its efforts to protect much of Boston's shoreline from sewage overflow and storm run-off, the Massachusetts Water Resources Authority (MWRA) is uncertain about how to undertake similar projects along Columbia Point and Carson Beach, making environmental watchdogs nervous about the prospects of finally ridding Dorchester Bay of the high bacteria levels that have plagued it for decades.

Currently, when enough rain drains into sewage pipes along the shore, the combined overflow is discharged into the Bay, creating the high bacteria levels that cause beach closings and a general fear of sewage in seawater off the city's shore. That problem was largely solved along much of Dorchester's coastline by the huge project of separating sewage pipes from storm drains that took place over the last few years. But the waters off Columbia Point and Carson Beach are still subject to sewage discharges during heavy rains, because of leaky sewage pipes and illegal sewage connections.

Planned projects there have been stalled by community resistance in South Boston to the large treatment plant that would be required to completely pump out the contents of the on-shore pipes. Now MWRA says it is looking at ways of preventing overflow that are less complete, but less disruptive and less expensive.

The MWRA has planned a public meeting next Thursday night in South Boston to explain the possible options.

"Community opposition to a large pump-out facility and the extraordinary associated cost has led to support for MWRA developing phased implementation approaches," said MWRA spokesman Jeffrey McLaughlin, in an announcement for the meeting. "It seems that many interested parties appreciate the advantages of a modular approach. It would allow MWRA to quickly achieve a high level of CSO ["combined sewage overflow"] control, while monitoring the beaches to confirm the incremental water-quality benefits. Another key point is that the phased approaches we are looking at preserve the option of CSO elimination in the future."

At least some interested parties are concerned that the MWRA is trying to take a cheaper and dirtier way out. The Conservation Law Foundation (CLF), for example, says the MWRA is reneging on its commitment, and its legal obligation, to protect completely the waters of Dorchester Bay from both sewer overflow and storm run-off.

CLF helped initiate the cleanup of Boston Harbor in the 1980s by filing a federal lawsuit, and the Dorchester Bay cleanup is subject to the same ongoing court case. CLF attorney Carol Lee Rawn says the MWRA is legally obligated to eliminate completely not just sewage overflow but also storm run-off from the city's beaches.

"MWRA has been backing off that commitment," Rawn said. "We're very concerned about that because the beaches are a very important resource for the city. … CSOs and swimming don't go together. And neither does stormwater. It carries garbage, chemicals, animal waste, oil and grease from cars - anything that is in the streets."

"They committed to eliminating CSO discharge and they no longer seem committed to that standard - they're talking now about reducing it," she said. "We feel like if a treatment plant gets us there, then so be it."

South Boston residents objected to a couple of proposed sites for a plant in that neighborhood, raising concerns similar to those aired by Dorchester officials two years ago when Boston Water and Sewer tried to site a facility on Columbia Point. Also, Massport has refused to give up any of its land at the Conley Shipping Terminal for a plant.

Rawn said Massport land could still be made available and she questions the diligence with which MWRA has pursued that option.

"I think they should take their commitment to the court seriously, and aggressively pursue a site for the plant" that is acceptable to the community, Rawn said.

Bruce Berman of Save the Harbor / Save the Bay, which initiated the first state lawsuit to clean up the Harbor, said the MWRA appears to be attempting to solve a problem without spending money.

"The MWRA is supposed to be the solution, not the problem," Berman said. "But in tough budget times, they are torn between the need to solve problems and pressure not to raise rates. … We have absolutely no intention of letting either the MWRA or the City out of their obligations under the Clean Water Act."

The environmental groups see the Dorchester Bay project as an unfinished component of the Harbor clean-up of which Boston is so proud.

"We feel this is one of the last pieces, and a critical piece," Rawn said. "To spend all this money to clean up the Harbor, and then to not be able to swim at the beaches every day - it doesn't make sense."

Rawn said MWRA's concerns about money are short-sighted. "It's false economics to spend all this money and then not make the final push."

MWRA Communications Director Jonathan Yeo responded to CLF's charges this week. "At this point, the MWRA is leaving no stone unturned and no option unstudied, that gets us to the goal of eliminating CSOs on the beaches while avoiding a bitter and lengthy fight over siting," Yeo told The Reporter. "We think it is quite possible that this goal can be achieved."

The MWRA claims that rainwater running off the streets is not its responsibility, and that solutions which include stormwater elimination require bigger, and therefore more disruptive and costly, projects.

The phased-in approaches to CSO elimination the MWRA is looking at now, meanwhile, earn some immediate relief from high bacteria levels, while avoiding burdening the community with a large treatment plant that would only be used during very large storms.

"We're committed to doing this project - it's under federal court order," Yeo said, adding that "This is really challenging for everyone."

Environmental activists acknowledge that there is as yet no agreement on the best way to stop sewage and storm pollution in the Bay, making it difficult for them to accuse MWRA of inaction.

"Finding the right location, then finding the right technology, then coming up with the money, together is a major challenge," said Vivien Li, executive director of the Boston Harbor Association, a group formed 30 years ago to protect the Harbor. "One of the concerns we have had is that it could get to the point where, if the planning process gets dragged out, that the will to fund the best solution might disappear. Unfortunately, we appear to be near that point."

"Economic times are such that it's going to be a challenge to find the money," she continued. "But money is not the main obstacle. … I don't think at this point there is a consensus about what type of solution is best. If we all had a consensus, we could all go to the MWRA board and push them to implement it."

"I'm starting to get a tiny bit discouraged," Li added. "The will is clearly there - the MWRA staff are near the point of just throwing their hands up and saying 'just tell us what you want and we'll try to do it.' … All we can agree on is that we want the CSOs stopped on all beaches."

But Li and Berman, and the MWRA, all are optimistic that movement toward a solution will occur this year. If it doesn't, they say, the waters of North Dorchester Bay might not be clean for years.

The MWRA's meeting will be held from 6:45-9 p.m. on Thursday, June 26, at the Curley Community Center in South Boston.