2/16/2012 SEWER COMMISSION Minutes

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Massachusetts Estuary Project(MEP) _ 11 _ Linked Watershed Embayment Model Peer Review The Panel was asked to review two TMDLs and the MEP modeling and analysis behind the development of those TMDLs. The two TMDLs reviewed were for Great, Green and Bournes Pond Embayment Systems(hereafter"Bournes"; Commonwealth of Massachusetts,2006)and for the Pleasant Bay System (hereafter"Pleasant Bay";Commonwealth of Massachusetts,2007),both addressing nitrogen as the pollutant of concern. In Section 4 above,the Panel has determined that the technical underpinning for the TMDLs and management plans that follow provided by the MEP is both scientifically defensible and functionally adequate. So,the science used to identify nutrient-related impairments, establish effects thresholds(or criteria), and develop the TMDL are adequate for that purpose, and for the implementation planning that will follow. It should be clear that there is no set standard for scientific adequacy under the CWA or established protocols for its determination during EPA review and approval of TMDLs. In 1998, a Federal Advisory Committee (FACA), established in November 1996 by the EPA,reported on its charge of "...recommending ways to improve the effectiveness and efficiency of State,Tribal and EPA programs under Sec. 303(d)of the Clean Water Act"and"...the science and tools needed to support the program" (U.S. EPA 1998). The Committee concluded: In developing TMDLs, States and EPA must ttse the highest degree of quantitative analytical rigor available. A reasonable minimum amount of reliable data is always needed.Decisions and assumptions based on best professional judgment must be well-documented. TMDLs for which a high degree of quantitative analytical rigor is notpossible in target identification and/or load allocation should contain relatively more rigor or detail in their implementation plans, including provisions fof•follow-up evaluation and potential revision based on the evaluation. The EPA FACA stressed rapid progress for restoring impaired waters,which they set at a high priority, further stating,"In cases of uncertainty,an iterative approach to TMDL development and implementation will assure progress toward water quality standards attainment." This report set the stage for developing TMDLs in accordance with the level of scientific certainty, and using phasing or adaptive management to take prudent steps forward, and improve on them later. However, as national TMDLs approved by EPA now exceed the 50,000 mark,with about 8,000 of them addressing nutrient-related impairments,phased or adaptive approaches are seldom realized in practice. Rigorous attainment of numerical standards through permit issuance is the usual outcome of a TMDL,emphasizing regulated point sources subject to the wasteload allocation. Because of the enforceable mechanisms and higher certainty of outcome for regulated sources under the wasteload allocation,EPA generally requires point source reductions be higher to compensate for the uncertainty of unregulated or voluntary nonpoint source management. In the cases of the Bournes and Pleasant Bay TMDLs,which technically represent 5 and 16 TMDLs, respectively,both have been approved by EPA—Bourns on July 18,2007 and Pleasant Bay on October 24,2007. There are 21 TMDLs because each represents an individual impaired waterbody segment,and a single estuary can contain multiple impaired segments. As adopted TMDLs,the target nitrogen reductions that meet the standards described in the TMDL analyses become the regulatory and management targets that define a"threshold"of health for each of the 21 impaired waterbodies within the two estuarine systems. These targets can only be changed with a revised TMDL, supported by scientific analysis that is deemed by EPA to warrant a change. The EPA approval process occurs at the regional office level,in this case the New England Region (Region 1) office in Boston. EPA staff provided a review memorandum for each TMDL that considered a set suite of 12 elements that include both technical and procedural or administrative requirements. Of special relevance to the Panel's charge on scientific review,both TMDL reports translated Massachusetts narrative standards for nutrients into site specific"threshold nitrogen concentrations"for each waterbody in both estuarine systems. These targets now have the force of adopted numeric criteria. The threshold concentrations were set using a"reference"approach(Howes et al. 2003,U.S.EPA 2001), as described in �� December 30,2011 25