Maryland State Highway Administration – Environmental Programs Division
- Stream Assessment and Restoration Design
- Environmental Permitting
- Berm Removal
- Natural Resources Inventory/Wetland Delineation
- GIS Analysis
Coastal Resources, Inc. (CRI) provided design services for the Maryland State Highway Administration’s (SHA) Intercounty Connector (ICC) Environmental Stewardship (ES) stream restoration site IC-62. CRI provided geomorphic assessments, hydrologic and hydraulic analyses, stream restoration design services, natural resource inventories, wetland delineations, environmental permitting, and designated specialist/inspection services during construction. IC-62 is a second order urban stream located within the Indian Creek sub-watershed. The project reach is located in the Coastal Plain physiographic province, just downstream from the Piedmont, which is typically a dynamic, depositional area. The study area included approximately 2,000 feet of Indian Creek beginning at Powder Mill Road. The project goals include berm removal, reducing channel incision and sedimentation, improving/enhancing aquatic and riparian habitat, enhancing adjacent wetlands, and protecting adjacent infrastructure.
While the channel morphology has been historically influenced by urban development, deforestation and subsequent valley fill similar to most urban stream channels in the Mid-Atlantic, channel alterations associated with utility and road infrastructure seems to have also caused significant impacts to the project reach. In order to develop a broader understanding of former impacts on the evolution of the Indian Creek channel morphology, CRI located and examined aerial photographs from 1938, 1965, 1989, 1993, 1998, 2000, 2007, and 2009, along with the 1960 sewer main design plans. The sewer main design plans depict a berm which begins just downstream of the Powder Mill Road Bridge and continues for approximately 500 linear feet along the top of the left bank. It is believed that this berm was constructed from the spoils from over-excavation of the channel in the 1940’s to provide flood relief for the Powder Mill Road crossing. The sewer main design plans also show areas of channel re-alignment in preparation for the expansion of Edmonston Road to the east, which was never completed. The cleared sewer right-of-way, berm, and portions of the straightened channel can be seen in the 1965 aerial image. Then during the 1960’s and 70’s the watershed underwent considerable development, greatly increasing the amount of impervious surface within the watershed.
SHA’s main goal for the site is the removal of the berm located along the first 500 feet of the left bank along with stabilizing the overall project reach. CRI conducted hydraulic analyses to determine the storm event that overtops the berm and compared it to downstream, stable reaches that are not similarly confined. CRI also conducted geomorphic assessments to evaluate the current geomorphic condition of the stream and to compare to geomorphic data from previous assessments. Geomorphic measurements such as cross sections, profiles, and pebble counts were completed in the same locations as the previous assessment, and compared to determine the magnitude of instabilities within the reach. The degree of grading required for the stream to access the floodplain on the left bank was determined, and areas in need of restoration/stabilization were identified, including the relocation of the first meander downstream from the berm, where the stream was historically re-aligned. As the project reaches are located in a depositional area, CRI also determined that the proposed channel will need to have adequate sediment transport capacity to provide long-term stability and avoid future channel avulsions. Sediment transport capacity analysis was therefore conducted on supply reaches and for the proposed project reaches to ensure long-term sediment continuity and channel stability.
CRI prepared the Joint Permit Application, Semi Final (60% design), Final (90% design), and PS&E (100% design) submittals, and erosion and sediment control plans. CRI also presented the design strategy to review agencies at Interagency Workgroup (IAWG) meetings and acquired all environmental permits, and erosion and sediment control permits. Final Design Plans, Specifications, and Estimate for the restoration of the IC-62 site were completed in 2012. CRI will also provide Designated Specialist services during construction.