Many project teams are reluctant to attempt this credit because conventionally engineered solutions don’t always meet LEED requirements. Don’t be deterred. The best and easiest way to improve the quality of stormwater is to let water permeate the ground through increased landscaping and reduced impervious areas. As long as your soil type has a good infiltration rate, letting stormwater seep into the ground will treat 100% of the pollutants associated with the stormwater runoff. Let natural infiltration do as much of the work possible before using more expensive mechanical methods. In urban sites, infiltration options can be very limited and a rainwater cistern or green roof might be the best approach for credit compliance.
Pollution Prevention
This credit deals with the prevention of polluted runoff, and uses Total Suspended Solids (TSS) as the indicator of level of pollution. Nitrates and phosphates are not accounted for in the credit calculations. Projects can use biological or mechanical treatment methods for smaller and more frequent storms for credit compliance. In order to earn the credit you must be able to show your stormwater treatment system is effective at treating all rainstorms for any year up to 90% of the average annual rainfall event.
Numerous environmental benefits
Retaining and reusing stormwater on-site can provide numerous environmental benefits, along with LEED synergies. In addition to trapping suspended solids, capturing stormwater for reuse can reduce peak runoff rate and volume, helping with SSc6.1: Stormwater Design—Quantity Control, and help with water efficiency credits WEc1, WEc2, and WEc3.
