HomePublic Project Finalist: Andorra Creek Floodplain Restoration Project

The Excellence in GSI Awards Ceremony (May 23) is the region’s only award that celebrates and elevates green stormwater infrastructure projects and innovations, the triple bottom line (TPL) benefits of a nature-based approach to stormwater management, and the partners who bring these projects to life in the Greater Philadelphia Area. Buy tickets.


On behalf of the Sustainable Business Network of Greater Philadelphia (SBN), the GSI Partners will be recognizing excellence in GSI in the following categories: Public, Private, and Innovation. Winning applications will highlight the TPL (environmental, social, and economic) benefits of a green infrastructure approach to stormwater management. 

Congratulations Andorra Creek Floodplain Restoration Project. 


Andorra Creek is located entirely within Whitemarsh Township, a 14.5-square-mile municipality located in Southeastern Montgomery County, PA. At approximately 1.2-miles-long, Andorra Creek flows southwest from Harts Lane and enters the Schuylkill River near Spring Mill Park. The primary land-use within the watershed is single-family residential properties and park land, with a total drainage area of 632-acres.


As the Andorra watershed developed, the volume and rate of stormwater runoff from storm events increased, causing the stream channel to undergo changes in an attempt to accommodate the greater flows. Because the stream was conveying greater flows more often and for longer periods, there was severe erosion to the stream banks.


These physical changes degraded stream habitat, producing substantial increases in sediment loads as a result of accelerated channel erosion. Additionally, two stormwater outfalls for the watershed’s storm sewer conveyance system discharge directly into the headwaters of the creek, resulting in water quality degradation, stream channel erosion, and loss of aquatic species.


To improve the stream’s performance while maintaining the integrity of its surrounding forest and parkland, a series of GSI features were designed to reduce sedimentation while infiltrating stormwater, increase flood storage and flow attenuation, improve filtration, reduce streambank erosion, sediment load, nutrient filtering, and biological uptake. All work performed for the project was in accordance with the Pennsylvania Stormwater Best Management Practices (BMP) Manual and the Keystone Stream Team’s Guidelines for Natural Stream Channel Design for Pennsylvania’s Waterways.


All these improvements help the municipality in achieving its MS4 goals, as well as in stabilizing and improving the creek’s habitat and reducing the community’s exposure to potential health risks. The project has also resulted in public recreation improvements, and protection of private property and critical infrastructure.


Congratulations to the partners who made this project an example of the kind of nature-based approach to stormwater management that has made the Greater Philadelphia Area a leader in GSI. 


County: Montgomery
Watershed: Andorra
Planning/Design Team: T&M Associates
Client: Whitemarsh Township
Construction/Maintenance/Monitoring: Scott Building Corporation and Whitemarsh Township Public Works Department


Join us on Thursday, May 23, along with the region’s industry professionals, local businesses, developers and property owners, government and non-profit institutions, decision-makers, and academics. It is the networking and celebration event for those in the GSI industry. Buy tickets. (SBN Members receive a discount on tickets.)