Harford County, MD
GTA provided wetland delineation, GPS location of wetland boundary, rare, threatened, and endangered species consultation, wetland permitting, and stream mitigation design services for the proposed 349 single-family and 397 townhome subdivision on a former 300-acre golf course. Following the completion of the wetland delineation, GTA submitted a Joint Federal/State Permit Application for proposed impacts to streams, wetlands, wetland buffers, and the 100-year floodplain. The proposed impacts included three road crossings of streams and wetlands, site grading, lot fill, utility line crossings of streams and wetlands, and stormwater management pond outfalls. The road crossings consisted of a 9-ft by 6-ft box culvert, a 72-inch reinforced concrete circular pipe culvert (RCCP), and a 48-inch RCCP culvert. The comments received from the Maryland Department of the Environment and the United States Army Corps of Engineers focused on avoidance and minimization of the proposed impacts resulting from the three road crossings. These agencies were firm in their comments to redesign the crossings using spanning structures such as bottomless arch culverts or bridges. In collaboration with the project engineer, GTA was able to successfully present definitive justifications for the use of the proposed box and RCCP culvert crossings. These justifications included:
an assessment of stream geometry;
location of large areas of wetlands both upstream and downstream of the proposed crossing locations, which would result in additional impacts to the site’s resources;
stream scour and public safety issues resulting from a spanning structure that would bend to mimic the stream geometry;
inadequate span length for bottomless arch culverts;
inadequate space for utilities within the road over spanning structures, which would result in additional utility crossings of the resources; and
small drainage areas contributing to the proposed culverts, which could be adequately conveyed through the culverts as proposed.
The approval of the proposed box and RCCP culverts resulted in an approximate construction cost savings of $600,000 to $850,000 for our client.
Additionally, GTA successfully negotiated with the reviewing agencies to accept stream bank enhancement plantings as a form of stream mitigation. These enhancement plantings will fill in gaps in open areas along the stream corridor to create a continuous forested stream corridor throughout the site, which will buffer the stream from the proposed development.