Installation of subsurface infiltration system

In 2015, the state legislature adopted the Vermont Clean Water Initiative, also known as Act 64, with the overarching goal of improving water quality across Vermont. Alongside farm pollution laws, the initiative adopted a comprehensive Stormwater Permitting Rule, prompting the development of General Permit 3-9050 and the identification of sites with three or more acres of impervious surface required to obtain permit coverage. Within the Lake Champlain Watershed, over seventy schools were required to comply. The Green School Initiative Program supplies funding from the State Agency of Natural Resources to assist schools with the design and construction of appropriate stormwater retention and treatment systems, and Otter Creek Engineering (OCE) had the opportunity to provide engineering design and permitting services for 22 of the identified schools.

Installation and setting of primary outlet structure with internal water treatment filters

During the summer of 2025, construction commenced for 12 of these schools. OCE provided engineering and construction review services for the schools, encompassing technical and engineering support for the installation of 20 structural treatment practices. The primary practices utilized included the following:

  • Bioretention Basins – Remove pollutants from runoff through a vegetated filter bed of sand, soil, and organic matter. Practices provide water quality treatment and aesthetic value.
  • Gravel Wetlands – Remove pollutants from runoff and maximize the uptake of nutrients through wetland vegetation.
  • Infiltration Practices – Capture and store stormwater runoff, allowing it to infiltrate into the soil. This practice reduces pollutants and total suspended solids via the physical filtering of the runoff through soil.

 

Installation of stormwater filter structure

Construction highlights

  • Installation of a 3,250 square foot subsurface R-tank storage system. This system replaced an overgrown and outdated wet pond. This area now provides usable green space for school activities.
  • Installation of a 2,250 square foot subsurface storage system with an impermeable liner connected to the school’s irrigation system. Runoff is collected directly from rooftops to this system and is used to water the athletic fields.
  • Installation of several subsurface infiltration systems and surface level infiltration basins. Subsurface systems were installed directly below parking lots, and athletic fields, a surface level infiltration basin was fully constructed before a severe flash rain in July. This basin did not overtop and was drained within 24 hours of the rain event.
  • Several proprietary filter systems installed inline and offline of existing stormwater conveyance practices. These systems minimized construction site disturbance to nearby utilities and infrastructure. Additionally, they will continue to operate with minimal maintenance and disturbance to school activities in the future.