Robert Zimmerman, executive director of the Charles River Watershed Association--a group which is urging the MWRA to include more funding for Charles River CSOs--agreed that CSOs are not the largest problem.

"Even if you eliminated the CSOs, it would not meet EPA standards [for swimming]," Zimmerman said.

Yet while he acknowledges that curbing CSO output is not the solution to the river's problems, Zimmerman advocates focusing more attention on the sewer outlets, arguing that it would still "dramatically" clean up the river.

Zimmerman said that the MWRA feels that because runoff problems are impossible to eliminate, EPA standards are impossible to achieve.

But the MWRA itself emphasizes that their plan, while it may only eliminate CSOs in Boston harbor, will still reduce some CSO output.

After all, CSO output will now only occur at a maximum of three and a half hours per year, according to Michael J. Hornbrook, the MWRA's director of sewage facilities development.

Hornbrook added that those who have criticized the MWRA have based their complaints upon numbers which are segmented from the authority's entire plan.

Although only $21 million of the $423 million clean-up budget will be spent on the Charles River, much of the budget will be spent on projects indirectly aiding the river.

"If we don't have the capacity at Deer Island, we start choking," Hornbrook says. "The more ability we have to get the sewage out there, the less it goes into the Charles basin."

But while officials at the EPA and CRWA acknowledge that the Deer Island plant will be helpful, they are skeptical about the MWPA's proposal to kill remaining bacteria flowing into the river with chlorine.

"We're not convinced that they can remove all the toxic chemicals from the water and we're also not convinced that the chlorine can remove all the pathogens," Moraff says.

Instead of treating CSO output with chlorine, Moraff and Zimmerman advocate eliminating CSOs by entirely disconnecting municipal storm drains from sewer lines, a process which for the Charles River alone would cost an estimated $200 million.