Maryland Transit Administration
- Geomorphic Assessment
- Biological Assessments
- Tracer Study
- Hydrology and Hydraulics
- Mitigation Planning & Design
- Agency Coordination
The Purple Line is a light rail transit project connecting Prince George’s and Montgomery Counties in Maryland. Unavoidable impacts to waters of the U.S., not including wetlands, will total 5,151 LF of perennial and intermittent streams and 355 LF of ephemeral channel. Project impacts to waters of the U.S. must be mitigated in accordance with the Clean Water Act.
Coastal Resources, Inc. (CRI) conducted an extensive site search within the affected watershed for suitable mitigation opportunities. A segment of Paint Branch near the confluence with Indian Creek was identified as the preferred compensatory mitigation stream restoration site for the Purple Line Project. The Paint Branch stream project is located in central Prince George’s County within the city of College Park, near the College Park Airport, Paint Branch Stream Valley Park, and Lake Artemesia. Paint Branch is a fourth order stream located within the Northeast Branch subwatershed of the Anacostia River watershed. Most of the project area is surrounded by parkland owned and managed by the Maryland-National Capital Park and Planning Commission (M-NCPPC).
CRI performed a detailed stream geomorphic assessment, a pebble tracer study, floodplain hydraulic analysis, wetland and forest stand delineations, water quality sampling, and habitat and biological data assessments including collecting fish and macroinvertebrates. These studies documented existing conditions and provided the basis for the restoration design.
CRI was the lead designer for the Paint Branch stream restoration project. The study area includes 3,511 linear feet of Paint Branch. The project focused on stabilization, floodplain connectivity, and habitat improvements. CRI developed the preliminary investigation and concept design (30%), semi final design (60%) and final design (90%) report, plans, specifications and estimate. CRI also presented the design strategy to stakeholders and review agencies at milestone meetings. In addition, contract documents (100%), including plans, specifications and estimates required for project advertisement were prepared. Coordination with the College Park Airport and M NCPPC in regard to access, safety briefings, design features, and vegetation and wildlife management was conducted extensively throughout the project.
The Prince George’s County Department of the Environment maintains a Stream Stage Gauge on the pedestrian bridge located over Paint Branch in the middle of the proposed restoration reach. The gauge is part of the county’s flood alert program. Data from the gauge site was obtained by CRI in order to verify the predicted flood frequency calculations. In addition, CRI performed detailed hydraulic modeling and prepared a hydraulic report to obtain floodplain approvals from the County.
CRI prepared the Federal/State Joint permit application and plates for impacts to obtain the waterway construction authorization associated with the stream restoration project. CRI also coordinated extensively with the USACE to obtain the Section 408 permit as the stream design is considered a minor modification to the flood risk management project currently in place. CRI developed post construction monitoring protocols and will provide designated specialist construction services during construction.