Carlon Drive: Compensatory Wetland Not Working

Former City Councilor Mike Kirby kindly provides this article to us, a study of a “compensatory wetland” on Carlon Drive. We are concerned that the proposed wetlands ordinance places too much reliance on schemes like these, in exchange for letting developers encroach to within 10 feet of wetlands in our built-up areas.

Carlon Drive
by Mike Kirby

Us graybeards remember the flash floods that hit the Church Street area about five or six years ago. Rising groundwater in the marsh blocked the culvert carrying the Barrett Brook, and it surged east along its old course, flooding out many basements in the area.

Carlon Drive and the Barrett Street swamp are teaching lessons about what happens when you build on, or close to wetlands. When the subdivision that holds the fire station was put in, over the objections of neighbors, the city was told that the groundwater in the adjoining Barrett Street marsh was too high. Conventional ways of dealing with storm water runoff wouldn’t work.

On October 1983, the Northampton Conservation Commission warned Stop & Shop that the parcel was subject to the Wetlands Protection Act. “This area,” said former city planner Larry Smith, “has a past and recent history of urban flooding.” In 1991 a 3-3 vote by the Conservation Commission blocked the proposal.

But then seven years later, the City and Stop & Shop came back with another plan. This time the City Council president, Pat Goggins, was ram-rodding the deal. The city’s own consultant, Baystate Environmental, raised questions about what was going to happen if they built the detention pond within the floodplain of the swamp, but the conservation commission didn’t listen.

All they could hear was that approval of the subdivision would mean a new fire station, which the city desperately needed. Pollution? Damage to the surrounding swamp? They didn’t want to hear it.

Detention ponds have to operate independently of rising groundwater levels: they have to have to hold runoff from big storms for some time period, and then discharge it when the peak runoff time has passed. They have to be above the flood plain.

In Carlon Drive, they simply scooped out a hole in the swamp-bottom, and called it a detention structure. Today it is just a pond, and a stagnant smelly one. It was designed to have a dry forebay, and a shallow main chamber was supposed to have only about 6 inches of water in it. This was supposed to be a compensatory wetland, full of cattails and wildflowers. A rock check dam was supposed to hold back the “first flush” off the parking lots and trap pollutants, and outflow from it was supposed to feed the wet part of the detention pond. Here rain water pouring off the new parking areas and street was supposed to be stored, and discharged safely.

That was the plan. Today if you stand by the pond and look down into it, you’ll see the check dam is now about two feet underwater. You can’t even see where they planted the marshgrass and flowers. The area is under water. Even in a fairly dry summer, the detention pond is only about a foot and a half from the top of the bank. There’s no storage to speak of, no discharge, no filtering. As it is constructed now, grey water from the parking lots and the access street goes directly into the swamp and the Connecticut River.

I talked to Carolyn Misch of the Planning Department, and she said that she thinks the detention pond will work better when they dredge the Barrett Street Brook. When will they dredge the brook? As I understand it, DEP mandated an expensive method of dredging, and the city can’t afford it. So the years go by, paper is shuffled, deadlines are missed, and we mark time until the area gets a ten-year storm or one of the big ones, the 100-year storm. A realtor once told me that developers developed all the good stuff in the 70s and 80s; now we get political pressure to roll back the regs so the junky stuff with wetlands, vernal pools and ledge can be developed.

See also:

City of Northampton, Memo from Mayor Clare Higgins to City
Councilors, “FY 2009 Capital Improvements Program Recommendations”

Bridge Street School – Detention Basin/Sewer Tie-in – $22,000
Repairing the three dry wells at Bridge Street School was ranked as the
[Northampton Public Schools’] second highest priority. The wells are
filled with silt and the ground water backs up into the building. The
DPW has cleaned the wells but the problem still exists due to the lack
of slope and the deteriorated condition of the wells.

Alex Ghiselin, Letter to Gazette: “Don’t let development encroach on our wetlands”
The failure of the storm water system built as a part of the Northampton High School renovation six years ago illustrates why protecting wetlands is so important. Silt has filled the retention pond so there is no capacity to slow a storm surge which now flows unimpeded into the Mill River and contributes to flooding downstream. This accumulated silt also raised the water table and spills ground water into nearby basements…

Without maintenance, these [storm water mitigation] systems are part of the problem, not the solution…

Wetlands do not need to be maintained; they just need to be protected.

Flooding Around Barrett Street Marsh: Development Eyed as Factor
…The city has been sued over problems in the marsh and has a responsibility to maintain the area’s water infrastructure as part of a mediated agreement involving neighborhood residents…

Ward 1 City Councilor Maureen T. Carney, said residents around the marsh are anxious about the potential for flooding, particularly on Church Street, which was subject to heavy flooding and property damage years ago…

Several city residents are protesting the city’s actions and calling for public hearings. Some say the city has created the problem by the way it has allowed the area to develop.

“I suspect water problems will persist long after the beavers move on,” said Joanne Montgomery, a former Conservation Commission member, as she addressed the council Thursday.

Connecticut River Watershed Action Plan: Remove impervious surfaces within 50 feet of streams
To reduce nonpoint source pollution from stormwater runoff, the Connecticut River Strategic Plan proposes the removal of impervious surfaces within 50 feet of streams and the investigation of “functional replacements” (such as the use of permeable pavement) for impervious surfaces within 100 feet of streams, in developed areas (PVPC, 2001). In the urbanized areas, the removal or retrofitting of impervious areas and the implementation of Stormwater Best Management Practices (BMPs) could be beneficial in improving water quality.

Is the Proposed Wetlands Ordinance Similar to Current Buffer Zone Policy? Judge for Yourself
Some people appear to be consoling themselves that an increased amount of artificial or replacement wetlands will balance the harm from the stepped-up level of encroachment. Unfortunately, the failure rate for these mitigation schemes is high. See these pictures of mostly dead, polluted detention ponds from South Carolina…