HIGHGATE — Thursday night the Highgate selectboard leant its support to two projects aimed at improving stormwater conditions in the town.
The board voted unanimously to do excavation work on private properties with ditches that carry water away from the Highgate Elementary School.
Also on the agenda was a project to reduce runoff on Mill Hill. Friends of Northern Lake Champlain (FNLC) and Stone Environmental have conducted stormwater reviews of several Franklin County communities, identifying projects with the greatest potential for improving water quality.
In Highgate, water from Mill Hill Road and a stormwater drain are eroding the sides of Mill Hill, with the nutrient-laden sediment going into the Missisquoi River and ultimately into Lake Champlain.
Julie Moore, the former director of the Center for Clean and Clear, now with Stone Environmental, showed the Messenger where stormwater flows off the road damaging the road edge and eroding the sides of the hill.
A small, unnamed stream carries the eroded sediment into the Missisquoi. The stream meanders through the heavily wooded middle areas on the hill, depositing some of the sediment it’s carrying until it reaches a culvert beneath a canoe portage along the river. Once the stream passes through the culvert, the water gains speed and becomes more centralized, quickly eroding the area below the culvert.
In addition to the roadside runoff, catch basins around Highgate Center collect stormwater from 33 acres of land and direct it into a pipe that comes out on Mill Hill.
“Where that outfall drops out there’s significant erosion,” said Moore.
FNLC and engineers from Stone Environmental are proposing to redirect some of that stormwater into the ground, so that it does not go cascading down the hill.
Redirecting the stormwater from Highgate Center will not stop the erosion along the side of the road, explained Moore, but it would be a first step in reducing the overall amount of water and sediment being carried into the lake from Mill Hill.
Sediment impairs water quality because the sediments within the soil encourage the growth of blue-green algae in warmer months.
FNLC presented the selectboard with several possible stormwater projects in Highgate Center that would address stormwater runoff where it initially falls, rather than sending it over the hill. The one it recommended was an 800-square-foot rain garden in the park between the town offices and library.
“You have fabulous sandy soils,” Moore told the selectboard. Those sandy soils allow water to infiltrate into the land quickly.
The rain garden would be built near Route 207 and would take advantage of the catch basin along the edge of the road. When rainfalls exceed the amount the garden could hold, the excess would flow into the catch basin.
The rain garden would be able to retain all of the water from storms with an inch or less of rainfall. That’s 90 percent of the storms in Vermont, said Moore.
“There’s a layer of clay below all the sand,” said selectboard chair Henry Rainville. When the soils become saturated, the water moves over that layer of clay and “the sand goes with it,” he explained.
There have been multiple landslides in Highgate in recent years.
Moore said the increased risk of landslides from this project was minimal, especially compared to the risks created by ongoing erosion on Mill Hill.
“The benefits of these projects far outweigh the risks,” said Moore.
Asked about approvals from the Agency of Transportation, Moore said the agency typically allows such projects as long as there is clear agreement about who is responsible for maintenance. Maintenance is “typically fairly limited” for rain gardens, said Moore.
Steve Bushey asked about the impact on residential wells. Moore replied that as part of the design for the project, Stone Environmental would make certain the project was at least 500 to 1,000 feet from any wells.
The project does not conflict with a conceptual design for a new sidewalk that would connect the town offices and library, although there will need to be communication as both projects move forward.
Once design for the rain garden is complete, FNLC will come back to the selectboard for approval before beginning installation.
The selectboard voted unanimously to give FNLC permission to create a rain garden design for the park.
Drainage at the school
For several years, the Highgate Elementary School has struggled with excess water on the school grounds. The school’s basement has flooded more than once, damaging the building and stored supplies.
Voters previously approved funding to address the problem and the school now has a design for a tile system to take water away from the building.
“We have to get the water away from the building,” said school board member Ron Tobin.
“Highgate School District is very concern about the building becoming wet again,” said Laura McAllister, a member of the school board.
“We’re committed to this. We have the money to do this project.”
The school is asking the town to assist by clearing out a ditch and potentially cleaning some culverts on private property that carry water from the school to Frog Pond.
Rainville was concerned the town would be setting a precedent for doing work on private property. “I firmly believe as a landowner you should take care of your land,” he said.
Selectboard member Luke Choinere moved to have the town provide excavating services for the project as necessary, but began his motion by stating the town was doing the work because of its importance to the school.
The board unanimously approved the motion.