EPA announced last week the long-awaited proposed effluent
guidelines for construction sites and released a pre-publication version (you
can see it here).
Once the guidelines are published in the Federal Register, comments are due to
EPA within 90 days. For all of us who work in the erosion and sediment control
field and whose work might be affected, it’s worth taking a look at the full
document. But here, in a nutshell, are some of the highlights.
The full title of the proposed rule is “Effluent
Limitations Guidelines and Standards for the Construction and Development Point
Source Category,” and its intent is to tighten controls on discharges from
construction sites by establishing technology-based effluent limits and
performance standards.
First, the rule calls for non-numeric
limitations that require all dischargers to provide erosion and sediment control
BMPs, which are specified in the rule. Additionally, sites of 10 acres or more
would need to have a sediment basin, or something that controls sediment to the
same extent.
For certain sites, though—“large sites
located in areas of high rainfall energy and with soils with significant clay
content”—EPA proposes a numeric turbidity limit of 13 NTUs. Because this level
is hard to achieve with fine silty and clay soils by settling alone, EPA says
such sites will probably need to use active treatment systems, such as the
addition of chitosan or other polymers to promote flocculation, followed by some type of filtration. It
also mentions electrocoagulation as a technology capable of reducing turbidity
levels.
The sites subject to this 13-NTU limit would
include those of 30 acres or more with an average soil clay content of more than
10% and a rainfall erosivity factor (the “R” factor from the Revised Universal
Soil Loss Equation) of 50 or greater. (If you view the complete document, see
Option 2 for more details on which sites would be subject to the numeric limit
and what other possibilities EPA considered.) In areas for which the R factor hasn’t
been calculated, total annual rainfall will be used as a criterion. (Discharge
from rainfall exceeding the local 2-year, 24-hour storm, however, would be
exempt from the limit.)
The proposal addresses the concern that
polymers might be overused at some sites, and that discharges from those sites
would be toxic. It judges the likelihood of this problem occurring to be low,
however, citing the widespread use of polymers in wastewater treatment
facilities.
EPA is also asking for comment on setting a
turbidity limit in the range of 50 to 150 NTUs, based on passive treatment. See
the document for a discussion of this option.
EPA
says the rule will cost about $1.9 billion per year, and the document includes a
detailed discussion of how it arrived at this figure.
What
do you think of the guidelines as proposed? Will they improve water quality? Do
they go far enough?