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1 <br /> Oregon Association of Clean Water Agencies <br /> REQUEST FOR PROPOSALS <br /> Stormwater Best Management Practices (BMPs) Effectiveness Review <br /> Introduction <br /> Over the past decade, Oregon's larger municipalities have devoted significant resources to <br /> addressing National Pollutant Discharge Elimination System (NPDES) and Total Maximum <br /> Daily Load (TMDL) requirements under the Clean Water Act. This work has included the <br /> development of Stormwater Management Plans (under the NPDES program) and water quality <br /> management plans (under the TMDL program) to reduce pollutant discharges from municipal <br /> separate storm sewer systems (MS4s). Some medium-sized Oregon municipalities have also <br /> developed or are developing Stormwater Management Plans under Phase II of the MS4 program. <br /> Also, many municipalities have developed Stormwater Management Plans as part of the <br /> regulatory requirements for Underground Injection Control (iJIC) devices. <br /> The Stormwater Management Plans include lists of Best Management Practices (BMPs) that <br /> municipalities select and then implement to reduce pollutants in urban runoff (from construction <br /> sites and from developed sites including new or redevelopment as well as existing developed <br /> areas). BMPs can be structural in nature including detention ponds, retention ponds, swales, <br /> infiltration trenches, underground devices (including many proprietary devices), and wetlands; <br /> and they can benon-structural in nature including maintenance activities (e.g., street sweeping, <br /> catch basin cleaning, etc.), public education, source controls and low impact development <br /> techniques. Precise quantitative measurement of the effectiveness, sustainability, and <br /> maintenance requirements of BMPs is very challenging. While the intrinsic benefits of the <br /> BMPs are intuitively obvious (for instance the value of street sweeping for reducing the sediment <br /> and contaminant load in stormwater), the inherent variability in site-specific conditions and <br /> stormwater characteristics makes quantifying the direct linkage between any specific BMP and <br /> receiving water quality very difficult. These uncertainties present major challenges when <br /> developing the package of BMPs to be included in Stormwater quality management plans. As <br /> information of pollutant reduction effectiveness is highly variable, it is difficult to select and <br /> prioritize the most appropriate BMPs for achieving goals, and it is difficult to precisely estimate <br /> the ultimate effectiveness of these BMPs. Quantifying the water quality impacts from BMP <br /> implementation is especially challenging with respect to the documentation requirements of the <br /> TMDL program. <br /> To gain knowledge regarding BMP performance, many monitoring studies have been conducted <br /> both locally and nationally. Typically, monitoring studies have been focused on structural BMPs <br /> and they have included measurements of pollutant concentrations and loads flowing into and out <br /> of the BMP. There are many issues associated with these BMP studies, including the following: <br /> • Studies are expensive to conduct properly. Less expensive, simplistic studies may yield <br /> results that do not provide a sound basis for decision making, but few municipalities are <br /> <br /> PAGE 1 REQUEST FOR PROPOSALS - - Stormwater BMP Effectiveness Review <br /> <br /> February, 2003 <br /> <br />