The recently completed Tidal Back River Greening Project was much more than planting trees and grass along the Back River watershed east of Baltimore, Maryland.
The USD $2 million green infrastructure project was a carefully planned and executed effort to significantly reduce pollutants carried by stormwater runoff to the river, which feeds the Chesapeake Bay. It involved the treatment of 6.9 hectares (17 acres) of impervious area through the implementation of green infrastructure and low-impact development techniques, covering nine sites throughout Baltimore County’s Back River watershed. Work was performed at a park-and-ride, a community center, and seven schools.
The green infrastructure measures employed on this project include bioretention, impervious cover removal, channel enhancement, tree planting, and stream buffer restoration.
The Back River watershed had been identified as impaired in the Maryland 303(d) list for various pollutants of concern, and action was necessary to decrease the amount of pollution flowing into the Back River.
“This project will immediately provide habitat enhancement and expand tree canopy coverage in a highly developed and densely populated portion of the county,” says Kelly Lennon, Project Manager.
The project incorporated low-impact techniques to treat runoff from existing impervious areas. For example, bioretention areas were set up to catch runoff before it could be carried into nearby tidal waters, eventually collecting in the Chesapeake. The water seeps through a soil mix that removes pollutants before it is filtered into the ground or conveyed, via underdrains, back to the storm drain system.
The green infrastructure improvements include the design and construction of eight bioretention areas treating 3.1 hectares (7.7 acres), .4 hectare (1 acre) of impervious cover removal, 139 meters (457 feet) of channel enhancement, and almost 1.6 hectares (4 acres) of tree plantings. These improvements will ultimately remove 115 pounds of nitrogen, 20 pounds of phosphorus, and 10,213 pounds of total suspended solids per year from the local waterways.
“Many of the facilities are located on public school property, providing an opportunity for water quality education to youth,” Lennon adds.
Parsons Brinckerhoff originally identified these projects as part of a comprehensive small watershed action plan (SWAP) for Baltimore County’s Department of Environmental Protection and Sustainability (EPS). As part of the plan, the team identified restoration opportunities that led to the creation of a workable plan to reduce pollution throughout the watershed. The project supports the county in fulfillment of its National Pollutant Discharge Elimination System permit and helps it meet its Chesapeake Bay pollutant load-reduction goals.
After completion of the SWAP, Parsons Brinckerhoff was asked to prepare conceptual and final design plans and construction-phase support services, including on-site construction inspection.
“The biggest challenge for the project was meeting the schedule,” says Everett Gupton, Senior Water Resources Engineer for the project. “As most of the sites were located on school property, design had to be complete by summer for construction to begin on time. This left only eight months to complete the final design.”
Conceptual design work was conducted in the spring of 2012 and final design began in November 2012, with construction beginning as schools went on summer break in June 2013. The project was unveiled to the public in November 2013, and final work was completed in late January 2014.
Retrofit projects like the Tidal Back River Greening Project are particularly challenging due to the constraints of the existing infrastructure and surrounding land uses.
“Parsons Brinckerhoff assisted the client throughout the process in not only overcoming the technical challenges, but also in communicating with and managing stakeholder expectations throughout the process,” Gupton says. “We were able to develop custom details for this project and collaborated with the public school district in the area to ensure that all parties would be pleased with the final outcome.”
Stakeholders included permitting agencies, Baltimore County Public Schools, the Maryland Transit Administration, and Baltimore County Recreation and Parks Department. Baltimore County Department of Environmental Protection and Sustainability (EPS) was the client.
Although the project is complete, critical environmental work in this region continues. The Parsons Brinckerhoff team that worked on this project is now conducting another watershed assessment, assessing streams and upland areas, and identifying retrofit potential in another Baltimore County watershed area. In addition, the team is also involved in the design of 3.2 kilometers (2 miles) of stream restoration in Baltimore County.
“Many of the obstacles faced previously with the stakeholders will be familiar,” says Katherine Klavon, Water Resources Engineer. “By fostering open communications with the school district in particular on this project, Baltimore County EPS knows the district’s preferences and concerns much better, and we can assist EPS in developing more efficient designs in the future.”