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Tidal Back River Greening

Award-winning project allows significant reduction of the pollution created by constructions built in the last 50 years in the Baltimore County.

In the Chesapeake Bay region, municipalities are under constant pressure to reduce pollutants and improve water quality to protect the Chesapeake Bay. The project, an initiative of the Baltimore County Department of Environmental Protection and Sustainability, consisted of nine sites within the Tidal Back River watershed in eastern Baltimore County.

The project required extensive coordination with stakeholders, including the school system, the County's department of Parks and Recreation, and the Maryland Transportation Authority, which runs the commuter park and ride lot. Design was completed in spring 2013 and construction began in June 2013. Construction and final plantings were completed in the spring of 2014.

Bioretention facility post construction


The nine sites included in this project were designed prior to the implementation of stormwater management requirements. One of the main goals was to improve water quality by constructing stormwater best management practices (BMPs) and urban plantings to retrofit portions of the watershed developed before the current stormwater management regulations.

The Tidal Back River watershed has been identified as impaired for various pollutants of concern, and the Baltimore County Environmental Protection & Sustainability needed to take action to decrease the amount of pollution flowing into the Tidal Back River.

The sites consist of seven schools, the Back River Community Center, and the Essex Park and Ride Commuter Lot. WSP | Parsons Brinckerhoff worked closely with Baltimore County Environmental Protection & Sustainability and County schools to design and implement the construction of eight bioretention facilities treating 7.7 acres of urban land; 4 acres of tree plantings, including street trees, shade trees, and riparian buffer enhancement; 1+ acre of impervious removal; replacement of existing asphalt pavement with pervious pavers; and 460 linear feet of channel enhancements.


Our team developed base mapping, conducted field assessments and reviewed current as-built drawings at each of the sites. With this information, we analyzed the existing drainage patterns at each site and developed green infrastructure implementation concepts that would provide the maximum water quality benefit feasible at each site.

The deliverable for the project’s conceptual phase included conceptual sketches at each of the sites, a cost estimate for the proposed green infrastructure implementation, and quantification of the potential water quality benefits that could be realized in pounds of nitrogen, phosphorus and sediment removed from the Tidal Back River annually.

Once the conceptual design phase was completed, Baltimore County was able to receive grant funding from the Maryland Department of the Environment (MDE) and the Maryland Department of Natural Resources (DNR) for final design and construction. The scope for the final design of the Tidal Back River Greening project involved developing detailed drainage and water quality design deliverables for 85 percent and 100 percent design submittal packages.

Our team coordinated with the various stakeholders, including the Baltimore County Public Schools, MDE, and the Maryland Transit Administration. Through this coordination, we completed the design on a fast-track schedule, in order for the project to be constructed during the summer vacation period of the school. Beginning in June 2013, our staff provided construction support services.

The Tidal Back Greening Project took the unique approach of providing green infrastructure to areas that were already developed, in order to eliminate pollution that was already occurring.

Before and after restoration


Through the installation of green infrastructure at developed sites, we were able to significantly reduce the pollution being shed from existing parking lots, roadways, and other impervious areas that had been constructed during the last 50 years.

The major benefit of the project is the reduction of nitrogen, phosphorus and sediment into the Chesapeake Bay from the previously untreated drainage area of the project. In total, the project removes 52 kg (115 lbs) of nitrogen, 9 kg (20 lbs) of phosphorus, and 4,633 kg (10,213 lbs) on an annual basis that count towards the overall watershed restoration effort in the Tidal Back River watershed.


  • Watershed planning and assessment
  • Hydraulics and hydrology analysis
  • Green infrastructure design
  • Preparation of design documents (plans, specifications and estimate)
  • Stakeholder coordination
  • Environmental permitting
  • Landscape architecture
  • Construction oversight