Here’s one more comment on EPA’s proposed Effluent
Limitations Guidelines (probably not the last, but at least the last for a
while). Two weeks ago I summarized
some of the discussion that took place at IECA’s annual conference in Reno about
the proposal. One of the participants in that discussion was Eric Berntsen of
the California State Water Resources Control Board, who briefly discussed his
state’s upcoming new permit. He explained that, unlike most other states’
construction general permits, it uses a risk-level framework; watershed risk and
receiving water risk are combined to give an overall risk level. At risk level
3—the highest level—a site might need to take suspended sediment concentration
measurements (not total suspended solids measurements… but that’s a separate
discussion).
Berntsen also emphasized that
California does take into account background turbidity measurements when setting
turbidity limits for sites, based on various eco-regions throughout the state.
In contrast, Jesse Pritts of
USEPA, who was on hand to explain many of the points in the proposed ELG, said
that because of the way the Clean Water Act is written, the flexibility really
doesn’t exist for EPA to consider background turbidity or the condition of
individual water bodies. Instead, the new guidelines are technology-based—and,
he noted, since “turbidity” is classified as a nonconventional pollutant,
regulated under the Best Available
Technology Economically Achievable (BAT) effluent guidelines, that’s what the
EGL addresses. (TSS, on the other hand, is on the Clean Water Act list of
conventional pollutants.)
It’s unlikely that this framwork is going to change—the ELG in its final form next December might have some changes, but taking background turbidity into account almost certainly won’t be one of them—but, given that situation, how much does background turbidity affect what operators do onsite? As Pritts noted, only sites with certain characteristics, such as a clay content of 10% or more, will be subject to the 13-NTU limit. Still, among the sites that are covered, there will be significant variation. What will the likely ranges be in the costs of treatment with the technologies EPA has mentioned (electrocoagulation, filtration, and chemically enhanced settling)?
You can find the complete proposed ELG and related material here.