What does it matter?
Ultimately, MS4 program managers want to know how the guidance in these memos may impact their programs in the future.
Generally, the sector is moving toward retention as a performance metric, and this includes using retrofits to meet permit requirements. This can be seen in recently adopted permits, such as Washington, D.C.’s 1.2-inch retention standard and Montgomery County, Md.’s requirement to retrofit 20% of impervious cover (more than 2,000 acres!) within a single permit cycle. The agency’s 2014 memo reinforces this trend.
EPA has been consistent in its intent to strengthen the stormwater program by addressing the high rate of expired permits in both the Phase I and Phase II programs. Also, the agency continues to point out the high percentage of MS4s that discharge into impaired waters, which signals that there’s likely to be an increase in WLAs in MS4 permits. The 2014 memo and the MS4 compendium spell out how this is likely to be done, and we can’t rule out the use of surrogates as an approach.
It remains to be seen exactly if and how EPA wants to address the topic of surrogates. Promoting their use through an additional memo or other policy action in the near future will confirm the approach is still alive and well. Considering the recent legal rulings on using surrogates, applications of this approach are likely to be done in instances where a strong causality exists and is thoroughly documented.
Seth Brown is stormwater program and policy director for the Water Environment Federation, an organization of engineers and industry related to wastewater, water, and water reuse. Visit www.wef.org; e-mail sbrown@wef.org.
