{"id":39277,"date":"2015-01-14T19:46:14","date_gmt":"2015-01-14T19:46:14","guid":{"rendered":"https:\/\/zonda-develop.go-vip.net\/concrete-construction\/article\/flow-based-surrogates-in-tmdls_o"},"modified":"2015-01-14T19:46:14","modified_gmt":"2015-01-14T19:46:14","slug":"flow-based-surrogates-in-tmdls_o","status":"publish","type":"post","link":"https:\/\/zonda-develop.go-vip.net\/concrete-construction\/projects\/infrastructure\/flow-based-surrogates-in-tmdls_o\/","title":{"rendered":"Flow-based surrogates in TMDLs"},"content":{"rendered":"<div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <\/div><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <p class=\"wp-block-paragraph\">In <a href=\"http:\/\/cdnassets.hw.net\/4f\/dd\/1c2e196d48eaafccd7bd5055c892\/epa-sw-tmdl-memo.pdf\" target=\"_blank\">November 2014<\/a>, EPA updated its <a href=\"http:\/\/cdnassets.hw.net\/d7\/64\/94dbd8c549ce9a42b78eee5efc58\/final-wwtmdl.pdf\" target=\"_blank\">2002 memorandum<\/a>, \u201cEstablishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs.\u201d The new memorandum is a final version of a <a href=\"http:\/\/cdnassets.hw.net\/79\/ee\/60f6094342478d9e89291f342401\/epaestablishingtmdlwla-revision.pdf\" target=\"_blank\">2010 memo<\/a> on the same topic that guided EPA regional offices on updates related to the role of stormwater runoff in total maximum daily loads (TMDLs).<\/p> <p class=\"wp-block-paragraph\">This article explains the evolution of regulated stormwater flows in the TMDL program and what this means moving forward.<\/p> <h3 class=\"wp-block-heading\">Stormwater in TMDLs: background<\/h3> <p class=\"wp-block-paragraph\">How regulated stormwater runoff has been addressed in the TMDL program requires a review of regulations and recent guidance from EPA.<\/p> <p class=\"wp-block-paragraph\">Initially, stormwater runoff wasn\u2019t included in the Clean Water Act (CWA). That changed, however, with the Water Quality Act of 1987. Those amendments led to the establishment of stormwater entities, known as municipal separate storm sewer systems (MS4s).<\/p> <p class=\"wp-block-paragraph\">The TMDL program identifies daily limits of regulated discharges (wasteload allocations, or WLAs) and unregulated discharges (load allocations, or LAs) allowable in a watershed while still meeting water quality standards for receiving waters. In the program\u2019s early days, regulated and unregulated stormwater discharges were often lumped together into LAs. A 2002 EPA memo sought to change this policy by proposing that:<\/p> <ul class=\"wp-block-list\"> <li>Discharges associated with MS4s should no longer be addressed as an LA but could be aggregated into the WLA component of a TMDL.<\/li> <li>While WLAs and LAs are to be expressed numerically, stormwater WLAs and LAs could be \u201cfairly rudimentary because of data limitations and variability in the system\u201d and<\/li> <li>numeric limits should be used \u201cin rare circumstances.\u201d<\/li> <li>Water quality-based effluent limits (WQBELs) could be expressed as technology-based (in terms of best management practices used) rather than performance-based.<\/li> <\/ul> <p class=\"wp-block-paragraph\">EPA\u2019s 2010 memo suggested disaggregating discharges from MS4s in WLAs, providing numerically based WQBELs \u201cwhere feasible\u201d for regulated stormwater discharges, and allowing for the use of surrogates when establishing targets for TMDL loads (more on surrogates later). The reasoning behind these proposed policy changes was that \u201cthe technical capacity to monitor stormwater and its impacts on water quality has increased\u201d and that \u201cTMDL writers have better data\u2026and have gained more experience since 2002 in developing TMDLs and WLAs in a less aggregated manner.\u201d<\/p> <p class=\"wp-block-paragraph\"><strong>Next page: Reaction to 2010 memo: lawsuits<\/strong><\/p><\/div> <!--nextpage--><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <\/div><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <h3 class=\"wp-block-heading\">Reaction to 2010 memo: lawsuits<\/h3> <p class=\"wp-block-paragraph\">There was a significant amount of pushback from the clean water and municipal government sectors on the 2010 memo.<\/p> <p class=\"wp-block-paragraph\">EPA received comments on the memo and sent it to the Office of Management and Budget (OMB) for review. In the meantime, legal actions related to stormwater TMDLs surfaced.<\/p> <p class=\"wp-block-paragraph\">Most notable was a federal court\u2019s ruling in <a href=\"http:\/\/www.washingtonpost.com\/blogs\/virginia-politics\/post\/fairfax-county-vdot-sue-epa-over-accotink-creek-watershed-regulations\/2012\/07\/12\/gJQAtzQ1fW_blog.html\" target=\"_blank\">Virginia Department of Transportation v. EPA<\/a> that EPA exceeded its authority in establishing a flow-based TMDL for Accotink Creek in Fairfax, Va. In this case, EPA Region 3 took over a sediment TMDL for the creek and applied streamflow as a surrogate for the pollutant of concern on the basis of the relationship between excessive runoff and sediment generated through stream erosion.<\/p> <p class=\"wp-block-paragraph\">The flow-based version would have required a 50% reduction in the one-year discharge in a 50-square-mile watershed. Considering the watershed is dominated by poorly drained soils and is highly urbanized (80% built-out and 25% impervious land cover), the technical and economic capacity to meet this reduction was almost impossible. These challenges compelled Fairfax County and the Virginia DOT to sue EPA.<\/p> <p class=\"wp-block-paragraph\">While the surrogate approach had been and continues to be used in elsewhere in the country, most notably EPA Region 1 (Northeast), there was no precedent for using flow or impervious cover as a surrogate for a pollutant of concern outside Region 1. In the Accotink Creek case, the judge simply stated that flow isn\u2019t a pollutant and therefore can\u2019t be limited via the TMDL program.<\/p> <p class=\"wp-block-paragraph\">Some see the ruling as specific to the TMDL program and not within the context of MS4 permits. This view is based upon a \u201clooser\u201d definition for stormwater treatment associated with Section 402 of the CWA \u2014 the National Pollutant Discharge Elimination System (NPDES) \u2014 which states that stormwater discharges are \u201cto be regulated to protect water quality.\u201d<\/p> <p class=\"wp-block-paragraph\">Others interpret the ruling more broadly. They question EPA\u2019s authority to regulate flow, even through NPDES, even though 18 states use some type of retention-based performance standard in their MS4 program. In fact, the national rulemaking that EPA deferred in March 2013 would probably have established the first national performance standard for stormwater based upon some type of runoff retention requirement.<\/p> <p class=\"wp-block-paragraph\"><strong>Next page: Final stormwater TMDL memo<\/strong><\/p><\/div> <!--nextpage--><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <\/div><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <h3 class=\"wp-block-heading\">Final stormwater TMDL memo<\/h3> <p class=\"wp-block-paragraph\">While the Accotink Creek case and other legal actions related to flow-based TMDLs were filed and the national stormwater rulemaking was moving forward, the 2010 memo remained parked at OMB until November 2014.<\/p> <p class=\"wp-block-paragraph\">The biggest difference between the two memos is the removal of language related to surrogates. Some think this signals that using surrogates in stormwater TMDLs is no longer valid. A closer review, however, questions this line of thinking.<\/p> <p class=\"wp-block-paragraph\">For instance, the 2014 memo states that numeric effluent limitations should be used \u201cwhere feasible\u201d and that \u201cnumeric WQBELs may include\u2026limits on pollutant discharges by specifying parameters such as on-site stormwater retention volume or percentage or amount of effective impervious cover.\u201d This clearly shows that the use of flow or impervious cover as a performance standard in an MS4 permit can occur, and because WQBELs may be associated with TMDLs (although not exclusively so), the connection between TMDLs and flow-based requirements still exists.<\/p> <p class=\"wp-block-paragraph\">In fact, the memo refers to <a href=\"http:\/\/cdnassets.hw.net\/d8\/a6\/fa71f36049e9bab9fec0cbe81e00\/sw-ms4-compendium.pdf\" target=\"_blank\">EPA\u2019s June 2014 compendium of MS4 permits<\/a>, such as Los Angeles County\u2019s 2012 systemwide permit, that utilize retention to comply with WQBELs. The surrogate language also may have been removed so EPA can consider additional actions related to the use of surrogates.<\/p> <p class=\"wp-block-paragraph\"><strong>Next page: What does it matter?<\/strong><\/p><\/div> <!--nextpage--><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <\/div><div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\"> <h3 class=\"wp-block-heading\">What does it matter?<\/h3> <p class=\"wp-block-paragraph\">Ultimately, MS4 program managers want to know how the guidance in these memos may impact their programs in the future.<\/p> <p class=\"wp-block-paragraph\">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.\u2019s 1.2-inch retention standard and Montgomery County, Md.\u2019s requirement to retrofit 20% of impervious cover (more than 2,000 acres!) within a single permit cycle. The agency\u2019s 2014 memo reinforces this trend.<\/p> <p class=\"wp-block-paragraph\">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\u2019s 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\u2019t rule out the use of surrogates as an approach.<\/p> <p class=\"wp-block-paragraph\">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.<\/p> <p class=\"wp-block-paragraph\"><em>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 <a href=\"http:\/\/www.wef.org\" target=\"_blank\">www.wef.org<\/a>; e-mail sbrown@wef.org.<\/em><\/p><\/div> ","protected":false},"excerpt":{"rendered":"<p>In November 2014, EPA updated its 2002 memorandum, \u201cEstablishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs.\u201d The new memorandum is a final version of a 2010 memo on the same topic that guided EPA regional offices on updates related to the role 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