District News & Events:
Rain Gardens, Bioretention Areas, and Community
Lamoille County Conservation District, with generous help from the Town of Morristown, installed three Green Stormwater Infrastructure (GSI) projects this summer to decrease stormwater flows and improve water quality for landowners throughout Lamoille County. Another project at Johnson State College is in the planning stages. By implementing green infrastructure practices such as rain gardens, bioretention areas, or bioswales, etc. Lamoille County Conservation District’s (LCCD) goal is to reduce nonpoint source pollution in the form of stormwater runoff from developed land areas that eventually lead to waterways. The work was funded by a competitive grant from the State of Vermont Agency of Natural Resources, Department of Environmental Conservation Ecosystem Restoration Program (ERP).
With LCCDs oversight, Peoples Academy High School (PAHS), and the Town of Morristown, constructed “mini constructed wetlands” to capture runoff from parking lots and with it salt, sand, oil, etc. to then store, filter, and slowly release the water into nearby natural waterways. The partner’s goal was to improve the already accepted VT construction standards of their parking areas to progressively improve the capacity to capture and treat stormwater to protect water quality. At Johnson State College (JSC), LCCD worked with Watershed Consulting Associates, LLC to complete a feasibility study and alternatives analysis to improve runoff capture by retrofitting the parking lot.
Two projects were installed at Peoples Academy High School, a Bioretention Area within the grassy area of the sidewalk, and a Rain Garden near the amphitheater. Both projects were designed by Watershed Consulting Associates to capture 90% of the stormwater runoff from the acre parking lot and with it salt, sand, oil, etc. to be stored, filtered, and infiltrated into the ground. Before installation, the untreated stormwater flowed directly into the catch basins that led to a tributary of Ryder Brook, and then to the Lamoille River.
The idea for the school project was initiated by Sheila Tymon’s Envirothon students in 2012 who conceptualized an overall “Green” school plan including rain gardens, a green roof, and pervious pavement. To bring some of the student’s ideas to fruition, LCCD wrote and received FY13 ERP funds with support from Concept 2, Inc. for the conceptual design to capture the parking lot stormwater runoff, and in 2014 received additional FY14 ERP funds for construction.
The Town of Morristown Highway Crew excavated the PAHS site, and Gravel Construction retrofitted the existing grassy area of the sidewalk into the Bioretention Area. LCCD purchased native seeds and installed mostly native plants to assist in the prevention of erosion, filter pollutants, provide pollinator habitat, and for visual appeal. The Town of Morristown seeded the areas with a Hydroseeder, equipment purchased through a former LCCD grant.
Both the Rain Garden and Bioretention Areas consist of shallow a depression that uses vegetation and a calculated mix of soils to filter and absorb water. These depressions then enhance the infiltration, storage, and removal of pollutants from stormwater. A foundation for the design includes studying the amount of stormwater flow from the existing impervious area. These areas are designed to hold standing water for no longer than forty eight hours after the end of a rain event with maximum ponding depths of 6-12 inches.
Rain Gardens can be easily designed and installed by landowners following a simple set of protocols. Rain Gardens are similar to a perennial garden found in a wet depression. The gardens can include a gravel base, topped with a low percent of composted native soils, and planted with water loving perennials. These gardens collect storm flow from driveways and/or water spouts having a simple entrance where rainwater enters the garden and an above-ground overflow where excess water leaves. Upkeep is similar to any garden with the added responsibility to check flow especially after large storm events.
Bioretention Areas are generally larger systems that treat and infiltrate a specific amount of stormwater. Engineered to ensure the design function meets the exact criteria for the sites location, soils, slope, and amount of impervious flow. These areas have continual operational and maintenance requirements since they are part of a stormwater treatment and flow control system. The areas include soil mixes (sand, compost, and topsoil) and erosion control structures like under-drains to aid in the control of overflow, specific vegetation to filter sediment, and check dams or swales to slow the flow of water moving through the system.
Johnson State College’s Bentley Parking Lot conceptual plans include two options. Both options would capture the stormwater from an impervious area of approximately 3.26 acres in size and include re-grading the parking lot to diminish overland sheet flow, and replacing the existing catch basin with a larger basin to accommodate larger pipes and flow. LCCD will seek additional funds for construction Spring, 2015.
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