Environmental Performance Benefits:
Estimated to remove 65% of total phosphorus with 2 rain gardens that treat 0.86 acres of impervious area.
Method: Information was obtained from the engineer’s stormwater narrative document for the project. The engineers used a technology-based approach to calculate what features were necessary to mitigate the on-site runoff.
Data: According to the engineer’s documents, the post-development condition results in a site that is 45% impervious; therefore the technology-based approach calls for a BMP that is at least 50% effective in removing Total Phosphorus. The rain gardens are designed to remove 65%. Rain garden 1 treats .6 acres of impervious area and rain garden 2 treats .264 acres of impervious area. The rain gardens are sized to treat the first 1” of rainfall over the impervious area within their drainage area.