Updates to the Industrial Stormwater General Permit

When the usual grey Washington weather turns to dry summertime in July and August, stormwater is likely the last thing on anyone’s mind.  That could become a problem for companies holding a newly updated Industrial Stormwater General Permit (“ISGP”).

ISGPs are issued by the Washington State Department of Ecology (“Ecology”) for periods of four years.  The most recent updated permit went into effect on January 1, 2020.  The ISGP requires that permittees sample stormwater discharges at least once per quarter.  Generally, the quarterly sample can be collected at anytime within the quarter.  One of the more significant changes from the previous permit is the requisite sampling date for the “first fall storm event.”  Previously, the first fall storm event was defined as any time on or after October 1^st that precipitation occurs.  The first fall storm event date has edged earlier, to September 1^st.

Typically, July and August tend to be relatively dry in Western Washington compared to the remainder of the year.  This can cause pollutants to accumulate at a facility.  Those pollutants will then be picked up in the stormwater after the summer, increasing the chances of an exceedance of a sampling parameter benchmark.  The shifting of the first fall storm event to the third quarter increases the likelihood of having a benchmark exceedances in that quarter, which in turn increases the overall likelihood of having exceedances in multiple quarters, thereby elevating the level responses that must be implemented.

It also cannot be overstated that facilities have become used to sampling the first fall storm event on or after October 1^st.  The failure to sample the first fall event that may occur between September 1^st and September 30^th would result in a permit violation.

So, what can companies do to avoid a permit violation associated with the new fall storm event date?  They can take a look at their operational best management practices (“BMPs”) and determine what can be done between now and September 1^st to assist in achieving benchmarks.  For example, that may mean shifting a facility’s sweeping and catch basin vacuuming schedule from September to August.  If any changes are made, be sure to update your Stormwater Pollution Prevention Plan accordingly.

Another new change that may catch permittees off guard concerns “consistent attainment.”  Previously, when a permittee met the sampling benchmarks for eight consecutive quarters, the permittee was considered to have met “consistent attainment” and could suspend sampling for those parameters for a period of three years.  Now, while the eight consecutive quarter standard remains unchanged, consistent attainment means that the permittee may only reduce sampling for those parameters to once a year for a period of three years.  Moreover, the ISGP specifies that the annual sample must be collected during the fourth quarter.

There are other modifications in the updated permit that our Environmental practice group would be happy to discuss.  Please contact Holly Stafford at Chmelik Sitkin & Davis P.S. at 360-671-1796 or HStafford@Chmelik.com for more information.