Mark down 2012 and 2013, give or take, a potentially very significant years for the Gowanus Canal. Last night, the Department of Environment Protection and the Army Corps of Engineers made presentations at a Community Board 6 Environment Committee meeting about the scope of the environmental problems in the Gowanus, the possible remedies and the potential timetables. In short, the problems are as bad as you think and they are going to take a long, long time to address, even if things go well.

First, the problems. “There are still a lot of issues remaining,” said DEP’s Kevin Clark. Those issues include more than 300 million gallons a year of what are technically called “combined sewage outflows”–raw sewage mixed with storm runoff–that still end up in the canal each year. “Even a modest rainstorm,” Mr. Clark said, results in raw sewage flowing into the canal. They also include a low level of oxygen in the water, sediment at the bottom of the canal that range from settled sewage to accumulated toxins and “floatables,” which are everything from plastic bottles to discarded condoms.

The DEP plans to spend up to $125 million–with money coming from city water and sewer fees–on cleaning up the Gowanus mess. Solutions include the planned modernization of the flushing tunnel that draws water from New York Harbor into the canal with “a much more robust, reliable pumping system” and an upgrade of the sewage pump that directs sewage away from the canal and toward the Red Hook treatment plant from the current 20 million gallons a day to 30 million gallons daily. There might also be a “floatables vessel” that would go around after bad storms and skim “floatables” from the surface and there could be dredging of 750 feet of the end of the canal past the Union Street Bridge to remove “sediment” left in the canal when raw sewage flows into it. Underground retention tanks to hold storm runoff until it can be handled have been dismissed as costing too much and requiring too much land. (There was an early proposal to use the toxic parcel known as Public Place for holding tanks, but the land is now supposed to become a mid-rise, mixed use project with hundreds of units of housing.)

The very technical goal is to have 3mg of oxygen per liter of water, which is the minimum needed to keep fish alive, with the hope of reaching 4mg per liter, which would allow for fish to thrive and breed.

In any case, the flushing tunnel will likely be shut down for a long period of renovation and repair next September and the dredging could happen “early in the next decade,” meaning sometime between 2010 and 2013. A planned three-year-long Army Corp of Engineers study of the Gowanus, meanwhile, will soon enter its seventh year. The Corp’s Mark Lulka said that he hoped for a final report in 2009 about the “ecosystem restoration” that it will do. He said that the city needs to do its part of the work first and that clean up options include widescale dredging and capping of sediment in some areas.

Mr. Lulka said that “Before we can do a sustainable, worthwhile, ecosystem restoration project…all that good work the city has laid out is going to have to be done.” He added that “Ecosystem restoration is the icing on the cake. The jewel following these things the Department of Environmental Protection puts into place. It’s about improving habitat for fish and birds and improving sediment quality.”

The slow pace of the studies and delays in cleanup have frustrated some residents, many of whom expressed skepticism at the meeting. The head of the CB6 Environmental Committee suggest that there is “some left over skepticism about whether and when these upgrades will happen and whether they will be maintained after the fact.” He added that “I suspect if Gowanus becomes more residential there will be a lot of pressure to increase the scope and the vision.”

All of which raises the interesting question of how luxury residential housing will coexist with a canal that continues to absorb massive flows of raw sewage during rainstorms and a clean up process that could easily stretch to 2020, given that official timetables from the Army Corps of Engineers (which has seen a three year study turn into what will likely be a nine-year undertaking) run to 2013 for the start of work.