If local requirements are not as stringent as LEED requirements, are we still required to meet LEED requirements beyond local standards? My project is following the State of California San Francisco Bay Regional Water Quality Control Board Municipal Regional Permit (MRP). The MRP directs that the “first flush” of runoff be treated. In Santa Clara County, the first flush is generally defined as 10% of the 2 year storm or 0.2 inches. The LEED criteria for arid watersheds (defined as those receiving less than 20 inches of rainfall per year) defines 90% of the annual rainfall as 0.5 inches (see below). Using the LEED criteria, the stormwater treatment controls would need to be 250% larger than that required under the MRP. Therefore, this LEED credit will not be attained.

The architect spoke with another civil engineer and his interpretation is that we are treating 100% based on the C.3 requirements of State of California San Francisco Bay Regional Water Quality Control Board Municipal Regional Permit (MRP). His interpretation is that there are two approaches. One meet the standards which are established the State of California San Francisco Bay Regional Water Quality Control Board Municipal Regional Permit (MRP) and if there are no standards than meet the minimum requirements established by LEED.

Can someone help verify the correct approach? Thank you.