Anne Arundel County Capital Projects Program
- Watershed Assessment
- SWM/BMP Assessment
- Data Management and Analysis
- Report Preparation
- GIS Analysis
As part of Open End A/E Professional Services Agreement #8553, Coastal Resources, Inc. (CRI) was contracted to provide a feasibility study of the Marley Creek 3 subwatershed to develop a list of potential projects that could assist Anne Arundel County’s in reaching their overall goal to meet their 2017 and 2025 Total Maximum Daily Load (TMDL) credit goals for the Chesapeake Bay Watershed. The previous Marley Creek 3 subwatershed study identified 17 outfall locations as viable projects. Upon further investigation for the Watershed Protection and Restoration Program, it was determined that some or all of these outfalls might not be feasible for restoration due to constructability constraints.
The goal of this feasibility assessment was to determine which of the previously identified outfall projects can move forward and to identify new projects. A holistic watershed based approach was used to identify new stormwater treatment Best Management Practice (BMP) opportunities that will maximize the amount of treated drainage and impervious area, and the number of TMDL credits as currently assessed by Maryland Department of the Environment (MDE) within the Marley Creek 3 subwatershed. The projects evaluated may include any combination of: environmental site designs, new BMPs, retrofits to existing stormwater management facilities, outfall retrofits, regenerative step pool storm conveyance, or stream restoration segments.
CRI obtained publicly available GIS data and determined the assessment area for each outfall site, by using GIS-generated drainage areas. During the desktop analysis, sites were examined for potential maintenance issues or contamination issues, such as being located within industrial areas. Areas within the drainage areas where additional potential treatment options may be implemented were identified for potential field investigation, including large impervious areas. Potential constraints and permitting requirements were also reviewed to inform the field investigation, including apparent utility conflicts, access to the outfalls, natural resources, and potential permitting issues.
CRI then conducted field investigations for all of the outfalls. Additional treatment areas identified during the preliminary desktop analysis were also investigated. The outfall watersheds were visually assessed during the field investigations, and some additional sites were selected for investigation while in the field based on apparent potential. Field investigation forms were completed for each potential treatment site.
Upon completion of the field investigations CRI evaluated property ownership for each of the sites. Property types for each potentially affected parcel were noted, and a list of property owners who would potentially be impacted was compiled. CRI also manually delineated preliminary drainage areas of the outfall sites utilizing GIS data available from Anne Arundel County, including 2’ contour files and shapefiles that show the existing drainage networks. These drainage networks were visually field verified during field investigations. The manually delineated drainage areas were compared against preliminary, GIS-generated drainage areas provided by the County.
Once the field investigations and desktop evaluations were completed, CRI ranked the sites. Several factors went into prioritizing treatment sites, including the percent impervious area that could be treated and any site constraints (including physical constraints, ownership information, easement acquisition needs, and permitting concerns). Field personnel discussed potential treatment areas to ensure consistency in scoring. Once the sites had been scored and ranked, CRI summarized the findings in a report.