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.
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.
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.