Meeting the New Effluent Limit Guidelines
By Scott M. Taylor
I came across a book entitled The Worst-Case Scenario Survival Handbook on the used bookrack at the secondhand bookstore in my town. I purchased the only copy, immediately recognizing its potential value, and because it was 75 cents. Turns out, it was money well spent. The book details how to wrestle with an alligator, how to perform an emergency tracheotomy, what to do if your parachute fails, how to land an airplane if the pilot is passed out, how to deliver a baby in a taxi—all practical stuff. What was missing, though, was how to comply with the EPA’s numeric effluent limit guidelines (ELG) for turbidity on construction sites. Thankfully, we now have a bit more time—about 18 months—to come up with a cost-effective strategy for the reduction of construction site turbidity.
We have temporarily dodged a bullet on the ELG from the EPA, but that does not mean the issue has disappeared. The EPA has agreed to rework the process and issue a new ELG for construction site turbidity by the winter of 2012. Both the National Association of Home Builders and the Small Business Administration have challenged the ELG by submitting detailed comments and petitioning the EPA under the Administrative Procedure Act to reconsider the guidelines. Apparently, in the development of the guidelines, the EPA used data from active treatment systems (coagulation followed by filtration) rather than from passive coagulant application systems (the technology chosen for the ELG), resulting in an artificially low number of 280 nephelometric turbidity units (NTUs). The SBA analysis indicates that a more appropriate number, based on the EPA’s data, is at least 800 NTU. In addition, both the NAHB and the SBA took issue with the EPA’s assessment of compliance cost, asserting that the EPA’s assumption of passive technologies was not consistent with the data used to set the numeric limit.
Some states, such as California and Washington, have numeric limits in place for turbidity on construction sites now. Construction general permit compliance costs in these states are relatively high, the technologies for turbidity reduction are imperfect, physical challenges at construction sites vary widely, and the experience level of site personnel relative to erosion control can also be a problem. What is clear, however, is that numeric limits for turbidity for construction are here to stay, and we need to develop cost-effective tools to meet the challenge.
Clearly, better erosion control techniques are the answer. The North Carolina State University Soil Science Department (www.soil.ncsu.edu) has done some excellent research in the passive application of polyacrylamide (PAM). Good results can be achieved using PAM with such traditional erosion and sediment control tools as straw blankets, wattles, check dams, and sediment basins. More field experience is needed with these techniques. There also remains some question about the toxicity of PAM in receiving waters. Again, research at NCSU would appear to show toxicity is not an issue at appropriate application rates, but the regulatory community is concerned about the potential for overapplication in the field.
Another potential solution is improved site drainage design during various phases of construction. The engineer typically addresses site drainage only when the site has achieved rough grade condition, leaving the vast majority of construction operations, from clear and grub to rough grade, at the discretion of the contractor. The contractor’s objective is to build the project per the construction drawings and the stormwater pollution prevention plan (SWPPP). Consequently, there may be little thought put into controlling site drainage during the majority of the construction process. Including a drainage and sediment and erosion control professional as part of the SWPPP implementation team may be a practical reality in the near term.
The project owner must also rethink how erosion and sediment control is treated in the bid process. Most of the contracts I see for small- and medium-size jobs (and many large ones) include SWPPP preparation and implementation as a lump-sum bid item. This results in conflict when there is a difficult rainy season, or when the construction schedule is longer than anticipated. We must have bid items for perishable erosion and sediment control practices such as binders, straw wattles, and silt fence. This way, the contractor will be paid when the erosion or sediment control practice has passed beyond its useful life, and compliance with the construction NPDES permit, or ELG, will be less of a struggle.
We are in a significant period of flux for the erosion and sediment control industry. Good ideas are desperately needed, and practical, cost-effective solutions seem in short supply. We can reduce turbidity in construction site runoff. It will be more costly than it has been to date, and not all construction sites will be perfect. Rabbi Tarafon, in the second century BCE, noted, “Although you are not expected to complete the task of perfecting the world, you must not cease from doing all you can.” I think 280 NTU was a bit too optimistic; let’s see what round two brings.
Scott M. Taylor, P.E., is a senior vice president with RBF Consulting in Irvine, CA. He is currently the chair of the California Stormwater Quality Association.
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