To reduce runoff volume and improve water quality by replicating the natural hydrology and water balance of the site, based on historical conditions and undeveloped ecosystems in the region.
In a manner best replicating natural site hydrology processes, manage on site the runoff from the developed site for the percentile of regional or local rainfall events listed in Table 1, using low-impact development (LID) and green infrastructure. Use daily rainfall data and the methodology in the U.S. Environmental Protection Agency (EPA) Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act to determine the percentile amounts listed in Table 1. The percentile rainfall event indicates the total volume to be retained on site.
Table 1. Points for retaining rainwater on siteProjects that earn at least 2 points under this credit may earn an additional point if the site meets one of the following criteria.
- The project is located on a previously developed site.
- The project achieves 1 point in SLL Credit Brownfield Remediation.
- The project is designed to be transit ready by achieving at least 2 points each under NPD Credit Walkable Streets, NPD Credit Compact Development, and NPD Credit Mixed-Use Neighborhoods.
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