The Glay Parking Lot stormwater management system is comprised of eight bioretention basins and an underground infiltration system located beneath the parking surface. The system is expected to reduce peak runoff rates and runoff volumes to the city’s Eaton Street storm sewer.

The bioretention basins can store up to nine inches of water above the filter bed before spilling into overflow structures that are connected to the infiltration system. Forebays dissipate the energy of stormwater entering the basins, while treatment occurs by filtration through aged, shredded hardwood mulch, the soil media filter, biological activity, plant uptake of nutrients, sediment retention, and infiltration.

The infiltration system consists of rows of open-bottom chambers encompassed by clean, crushed stone and non-woven geotextile. A pre-treatment row is lined entirely by filter fabric to capture sediment, simplify maintenance, and prevent clogging of the infiltration trenches.