DFI designed and secured major subdivision approval for this 61 lot townhome development. The site is bisected by a Baltimore Gas and Electric (BGE) right-of-way and required coordination with BGE for placement of a recreational trail designed as part of the development. This was one of the first projects to be processed through Anne Arundel County utilizing ESD practices in accordance with the revised 2007 State Stormwater Management Design Manual. The project was designed to extensively utilize sheet flow to conservation credit as well as ESD practices such as bio-swales and gravel wetlands. Impervious areas were also minimized through the use of Low Impact Development (LID) techniques such as the use of pervious pavement, where these areas also drained via sheet flow to conservation property. The PE target value was met, thus eliminating the need for any large structural stormwater management practice. A Coastal Plain outfall was designed to stabilize the stream reach at the outfall of the gravel wetlands. The perennial stream immediately downstream of the proposed coastal plains outfall had poorly defined bed features (contained no pools) and was vertically unstable. The culvert beneath Marley Neck Boulevard would run dry preventing fish passage. DFI performed a geomorphic assessment of this downstream reach and recommended incorporating step pools into the restoration design prepared by DFI. This design included a pool on the downstream end of the culvert with a weir elevation that would backwater to create a 6” pool depth in the culvert, allowing for passage of fish and macro-invertebrates. The subdivision approval process required that a floodplain study be prepared to determine the change in elevation of the floodplain both on-site and downstream. The study involved delineation of the drainage area to the downstream reach, computing the RCN value based upon ultimate land use, and determining a time of concentration to enter into TR-20 and TR-55 hydrology modeling software to determine the ultimate flow rate for the 100-year storm event. Cross sections were pulled from proposed contours for the design of the stream channel as necessary to provide an accurate model of the proposed downstream reach. DFI performed boundary and topographic surveys, as well as provided full construction survey stake-out for infrastructure and new home construction.
Major and Minor Subdivisions
DFI employs an extremely knowledgeable staff with extensive experience with residential subdivision and land development. DFI has specialized for years planning, engineering and permitting large scale residential subdivisions. Our firm is experienced with planned unit developments, single family townhome duplex and apartment projects. DFI prides itself on designing developments that incorporate the natural environmental features of sites into the design of the communities allowing residents to enjoy features such as forest conservation areas, wetland preservation areas, streams, etc. DFI’s design experience with major subdivisions includes development layout, infrastructure design, environmental remediation plans, recreational amenity planning and landscape architecture design.