This credit is a combination of stormwater quality control and quantity control, and includes site-specific criteria for more frequent, low-intensity storm events. There’s even a pathway for zero-lot-line urban projects.

Executing this credit may be expensive, but it can also be economical; it varies greatly depending on site, soil, and project. Additionally, teams should take some time to better understand the historical conditions of the site; this is important as you’ll need to use low-impact development (LID) and green infrastructure strategies that mimic the site’s natural pre-development hydrology.

There’s a catch, though. This credit may be difficult to achieve even with LID and green infrastructure strategies in place. You will need to ensure that your strategies actually keep rainwater on the site. For example, a green roof or a rain garden that drains to a municipal storm sewer—which is common—won’t cut it! Many projects, especially urban ones that don’t have large vegetated site areas to work with, are likely to find this one out of reach unless rainwater is captured and reused on the site.

What’s New in the LEED v4.1 beta

• The term “manage” in v4, which was confusing, is replaced with “retain (i.e. infiltrate, evapotranspirate, or collect and reuse).”
• The thresholds for retaining rainwater have been reduced, where the lowest threshold is now the 80th percentile rainfall event as opposed to the 95th event , and the highest is now the 90th instead of the 98th.
• The thresholds for zero-lot-line projects also decreased.

What’s New in LEED v4

• This credit combines the LEED 2009 stormwater quality and quantity management credits.
• A specific credit path has been added that accommodates zero-lot-line projects with reduced rainwater management opportunities.
• An expanded multi-tenant complex path has been added for all types of projects in addition to just retail projects.
• Projects must use onsite low-impact development and green infrastructure rainwater management techniques.
• The credit now uses a metric for testing compliance that calculates the total volume of runoff for the 95th percentile of regional or local rainfall events, instead of one- and two-year storm events.