Residents, developers clash over environmental impacts of North Haven school proposal

NORTH HAVEN — Environmental consultants warn the construction of a proposed private school on Ridge Road would harm nearby wetlands, threatening vulnerable species and leading to possible algal blooms.

But the project applicant, Slate School, which already has one North Haven location, contends the project would have no negative wetlands impact, and claims calculations used to inform the concerns are “erroneous.”

The environmental analysis and calculations, which suggest the development would load nitrogen into adjacent wetlands at concentrations significantly higher than a healthy stream can handle, were commissioned on behalf of residents opposed to the construction.

With a vote set for Wednesday evening on whether to forward the project to the Planning & Zoning Commission, members of the North Haven Inland Wetlands Commission will decide which side they believe.

A petition opposing the development has gained roughly 150 signatures from residents of North Haven and neighboring Hamden, according to Gary de Simone, who lives next-door to the proposed site and has helped lead efforts against the development.

If approved, Slate School would repurpose a decommissioned church at 5100 Ridge Road and construct a second building to create Slate Upper School, serving approximately 90 students in grades 7-12.

The campus would act as the counterpart to Slate Lower School, Slate’s nearby K-6 campus at 124 Mansfield Road, which also drew opposition when it was proposed in 2017.

Slate School’s learning model is centered around the environment. The organization has won multiple awards for environmental stewardship at its Mansfield Road campus, according to an email signed by founder Jennifer Staple Clark and Head of School Julie Mountcastle.

“As we had done since inception at our Lower School campus at 124 Mansfield Road, we are specifically working to improve the ecological health of the property at 5100 Ridge Road,” the email said, also pointing out the project had received more than 200 letters of support.

Environmental concerns

To the north of the Ridge Road property, a narrow stream makes its way past a row of pine trees. According to Sigrun Gadwa, a soil scientist, botanist and former executive director of the Quinnipiac River Watershed Association, that watercourse feeds into a larger stream that supports vulnerable species including caddisflies, black flies and stoneflies.

The surrounding wetlands also are home to native plants including fern, skunk cabbage, sedge tussocks and a variety of trees, she said.

Megan Raymond, a wetlands scientist advising Slate School, testified at an IWC public hearing that there will be no negative consequences to the wetlands system northwest of the site.

“There’ll be no adverse impacts on the physical characteristics of this wetlands system as a result of the proposed project,” she said during the Feb. 24 meeting, online footage shows.

She further argued that the existing development, which includes the church and a parking lot, has no stormwater management system.

“We’re seeking to implement modern and effective management tools to protect the water quality of this receding wetland that does exist to the northwest,” she said.

But Gadwa believes the proposed development could seriously damage the wetlands.

While she did not testify at the public hearing, Gadwa is an associate of George Logan, a consultant hired by those opposed to the project, who offered the IWC an assessment similar to hers.

If Slate School goes forward, according to Gadwa, nitrogen loading from the septic system could overfertilize adjacent wetlands, causing invasive species such as phragmites to outcompete native plants. Nitrate contamination of the headwater stream also likely would lead to eutrophication and algal blooms, she said.

Gadwa based her analysis on calculations performed by Clinton Brown of Loureiro Engineering Associates, a firm hired on behalf of the residents opposed to the project. Brown estimated that under proposed conditions, nitrates would enter the wetlands at a concentration of 32.4 mg/L.

The Environmental Protection Agency’s safe drinking water limit is 10 mg/L. And according to Gadwa, clean streams typically have nitrate levels of 1 mg/L or less.

A dispute over calculations

Thomas Daly, an engineer working on the Slate School proposal, called Brown’s calculations “erroneous.” He said they failed to account for an offsite watershed area that would further dilute the nitrate concentrations before they reached the wetland.

He also challenged Brown’s methodology, which was based on a 2006 manual from the Department of Energy & Environmental Protection, titled “Guidance for Design of Large-Scale On-Site Wastewater Renovation Systems.”

“The methodology can’t be extrapolated to such a small system,” he said, contending that method is intended for systems handling more than 7,500 gallons per day, as opposed to Slate School’s proposed 990 gallons per day.

The engineer likened the scenario to applying the Department of Transportation’s highway construction guidelines to a parking lot.

On the other hand, Brown, who did not return requests for comment, defended his calculation methods during the February public hearing.

“It is the opinion of the authors of the 2006 (DEEP) documents that the principals of that document apply to all systems …regardless of size,” he said, according to footage of the meeting.

Meanwhile, Logan said Slate School could have performed its own nitrogen loading analysis.

“They could have counteracted it and said, ‘you’ve done it wrong,’” Logan said.

But Daly said the project size did not require such an analysis.

“Why should we be held to a standard that nobody else in the state of Connecticut is held to?” he said. “The reason why you don’t do that is because the public code for smaller systems has been developed in a way that’s … highly conservative.”

Next steps

If the IWC approves Slate School’s proposal Wednesday, approval from the Planning & Zoning Commission represents the last major hurdle to construction, according to North Haven Town Planner Alan Fredricksen.

The project’s septic system also would need final approval from the Quinnipiack Valley Health District, according to Director Karen Wolujewicz.

An exemption from the state Department of Public Health, which is required because the project would use a single septic system for two buildings, already has been granted, the agency confirmed.

Staff for the DEEP were not aware of any proposal elements requiring the agency’s approval, according to spokesman Will Healey.

“Wetlands are in the town’s jurisdiction,” he noted.

Because the proposed site is within an Aquifer Protection Area, however, the DEEP did seek assurances from the town that “the groundwater will continue to be a priority and protected,” Healey said.

Information on how to view Wednesday night’s IWC meeting, scheduled to be held at 7 p.m. via Zoom, can be found on North Haven’s website.

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