On May 4, 2009, the Maryland Department of the Environment (MDE) enacted new stormwater regulations that mandate the use of Environmental Site Design (ESD) to the maximum extent possible (MEP). The goal of the regulations is to maintain the pre-developed site hydrology as nearly as possible after project development. Conservation of natural features, minimizing impervious surfaces and micro-scale practices to capture and treat and recharge runoff are encouraged. Traditional structural BMPs will no longer be allowed until all ESD options have been exhausted.
Prior to the anticipated regulation changes, GMB designed its first ESD development. Local developer Terra Firma sought GMB’s expertise in stormwater management to develop a 48 lot green community, Village Down River, along the Wicomico River, just outside Salisbury on Maryland’s Eastern Shore. The proposed stormwater plan needed to incorporate and preserve the site’s existing natural features while ensuring appropriate levels of treatment to protect the Wicomico River and ultimately, the Chesapeake Bay. In preparing for the stormwater management design, GMB considered all of the ESD practices recommended in Chapter 5 of the MDE Stormwater Design Manual.
This site design had to satisfy MDE’s water quality and recharge requirements as well as the requirements of the Chesapeake Bay Critical Area 10% Rule, which mandates reduction of post development pollution load to 10% below predevelopment load. Natural Area Conservation, Disconnection of Rooftop Runoff, Disconnection of Non-Rooftop Runoff, Sheet Flow to Buffers and Open Channel Use were all utilized to achieve the desired level of stormwater treatment while preserving the site’s natural features.
Road drainage is treated through bio-swales. Three (3) bioretention areas were installed to further manage water quality from roadway runoff. A “stepped”, or tiered, created wetlands system was utilized to treat additional road drainage at the project entrance, and at the connection to existing Riverside Drive. Existing shoreline buffers were retained to treat stormwater runoff that sheet flows from proposed lots, and preserve a natural buffer along the River. Natural resource areas were conserved to minimize development near the waterfront, protect the existing shoreline, and filter pollutants from surface and ground water. A two (2) foot wide stone trench filled with river rock surrounding the perimeter of each house will replace downspouts, and will ensure sheet flow is maintained to the buffer areas so that sediment and nutrients can be filtered before runoff reaches the Wicomico River.