FEATURED PROJECT

BayLand was contracted to provide engineering analysis, design, permitting, and construction services for the comprehensive Cat Branch Stream Restoration, SWM Pond Retrofit and Outfall Retrofit project by Anne Arundel County DPW through the Magothy River SWM Pond and Outfall Retrofit Open-End Contract. The project provides impervious area treatment credit towards the County’s NPDES MS4 permit as well as sediment and nutrient removal credit towards the Chesapeake Bay TMDL. The site is located near the intersection of Cape St. Claire Road and College Parkway in Cape St. Claire, Maryland. 

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The project reaches had been significantly influenced by historical channel alterations and increasing urbanization of the watershed which is approximately 285 acres with 24% impervious area. There was geomorphic evidence of active stream degradation and hydrologic evidence of floodplain disconnection. The design approach included 1,460 LF of Floodplain Restoration with Base-flow Channels to increase geomorphic and floodplain complexity, enhance denitrification, promote sediment and nutrient trapping, and encourage the establishment of wetlands and mature and natural floodplain plant communities. The proposed design involved raising the elevation of the incised stream bed and shallow groundwater in addition to Legacy Sediment Removal (LSR) to increase the volume of runoff diverted onto the floodplain during storm events. 2D hydraulic modeling was performed to verify channel and floodplain dimension stability by determining resistance to shear stress. Approximately 200 LF of stream valley and wetlands were also restored upstream of the project area without any construction disturbance using a clay groundwater dam that raised the upstream water table and restored wetland hydrology. Onsite trees were also utilized extensively in the restoration area to provide grade control. 

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The project also included the installation a stormwater wetland downstream of two storm drain outfalls adjacent to the reach and an upstream infiltration BMP. The watershed wide approach maximized sediment and nutrient reduction to the headwaters of the Little Magothy River. The project also featured extensive re-planting with native species to improve habitat quality, quantity, and diversity. Overall, the project provides 65 acres of impervious area treatment and 621 pounds per year TN, 49 pounds per year TP, and 38 tons per year TSS removal. 

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Permits were obtained from USACE, MDE, Anne Arundel Department of Inspections and Permits, and Anne Arundel Soil Conservation District. A DNR grant was awarded for construction, and construction was completed in October 2019. The project was awarded honorable mention for Best Stream Restoration by the Chesapeake Stormwater Network for the BUBBA and is currently part of a joint research project between the County and the University of Louisville.