Somerset Trust Company: Hempfield Hub Office
Greensburg, PA: Fall 2023
Project Highlights: RAFT footprint is less than 1% while intercepting 37% of the total areas stormwater runoff, Integrates with Additional Solutions, Series of Connected Planters, State Approved Non-Proprietary BMP
In this project, a series of three RAFT urban bioretention planters were deployed to handle a large stormwater runoff drainage area. Approximately 36% of the total drainage area (0.62 of 1.7 acres) is intercepted by RAFT planters covering less than 1% of the site’s surface area (0.015 acres). This serves as an excellent precedent where urban bioretention planters can efficiently treat and mitigate large runoff loads while occupying a miniscule site footprint.
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The three RAFT bioretention planters were installed on site and occupy 678 square feet (0.015 acres). Two planters (interior 5’W x 40’L x 4’D each) capture and treat runoff from approximately 21,350 square feet (0.49 acres) of area, with a majority of that being parking and roadway. An additional planter (interior 5’W x 30’L x 4’D) captures and treats runoff from approximately 5,700 square feet (0.13 acres) of parking area. The design team specified 24” of bioretention soil mix (PA Stormwater Best Management Practices Manual - BMP 6.4.5 bioretention soil mix guidelines) within the RAFT planter and connected the system to a separate underground detention zone via underdrain and overflow.
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The flexibility of RAFT’s modular post and panel system made it easy for the design team to dimension three planters that could intercept a large portion of site runoff and integrate with additional stormwater management interventions such as permeable pavers and underground storm detention tanks.