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City of Puyallup Future Stormwater and SWMP Effectiveness Monitoring Plan Prepared for City of Puyallup, WA December, 2010 ---PAGE BREAK--- 2 Section 1 Monitoring Overview This section provides a brief overview of the monitoring requirements that are set forth in the Washington State Phase II Municipal Stormwater Permit for Western Washington (Phase II Permit). 1.1 Current Permit Monitoring Requirements The Phase II Permit regulates stormwater discharges for small municipal separate storm sewer systems (MS4s) as established in Title 40 CFR, part 122.26. The Phase II Permit, issued in 2007 and modified in 2009, includes requirements for permittees to prepare to conduct a monitoring program in future permits. The Phase II Monitoring Program described in Section S8.C includes two types of monitoring: 1. Stormwater Monitoring (S8.C.1.a) 2. Stormwater Management Program (SWMP) Effectiveness Monitoring/Targeted SWMP Effectiveness Monitoring (S8.C.1.b) Stormwater Monitoring (S8.C.1.a) requires permittees to identify sites suitable for monitoring stormwater discharges based on jurisdictional size and land use types, and on known water quality problems and/or targeted areas of interest for future monitoring. SWMP Effectiveness Monitoring (S8.C.1.b) requires permittees to identify questions that monitoring may answer to determine the effectiveness of specific components of their Stormwater Management Program (SWMP). The permittee must identify sites for monitoring and create monitoring plans to answer at least two effectiveness questions. This document covers effectiveness monitoring as required for S8.C.1.b; stormwater monitoring (S8.C.1.a) is described in a separate monitoring plan. 1.2 Future Permit Monitoring Requirements This monitoring plan was prepared to meet the requirements of the current (2007) Phase II Permit, as noted above. However, the next Phase II Permit, which is scheduled to be issued in 2012, may contain monitoring requirements substantially different from those envisioned in the current Permit. Thus, this monitoring plan should be regarded as tentative and subject to change based on the next Phase II Permit. In 2008, Ecology convened the Puget Sound Stormwater Workgroup (SWG) to develop a comprehensive, sustainable, stormwater monitoring strategy for Puget Sound, as well as monitoring requirements for the next municipal stormwater NPDES permits. The SWG members represent caucuses of local, state, and federal agencies, environmental and business organizations, tribes and agriculture. The SWG submitted the comprehensive strategy in July 2010 to Ecology (in a document titled 2010 Stormwater Monitoring and Assessment Strategy for the Puget Sound Region). Based on this strategy, the SWG submitted monitoring recommendations for the next NPDES Phase I and II permits on October 29, 2010, in a document titled Recommendations for Municipal Stormwater Permit Monitoring). ---PAGE BREAK--- 3 The SWG recommends that Ecology designate an independent entity to administer the stormwater- related monitoring and assessment activities in the next municipal stormwater permits. This recommendation is called the “pay-in” option. The SWG recommended receiving water monitoring rather than the outfall monitoring described in the current permits. Moreover, the SWG recommended that the regional entity (rather than by each permitee) administer the program effectiveness monitoring and focus on questions of regional significance. More information on the SWG is available at http://www.ecy.wa.gov/programs/wq/psmonitoring/swworkgroup.html. ---PAGE BREAK--- 4 Section 2 Targeted Stormwater Program Effectiveness Questions Phase II Permit condition S8.C.1.requires that each permittee prepare a monitoring plan to address two questions related to the effectiveness of the permittee’s stormwater management program. The monitoring plan must contain the following elements: • A statement of the question, an explanation of how and why the issue is significant to the permittee and a discussion of whether and how the results of the monitoring may be significant to other MS4s. • A specific hypothesis about the issue or management actions that will be tested. • Specific parameters or attributes to be measures. • Expected modifications to management actions depending on the outcome of hypothesis testing. The City’s proposed effectiveness questions and monitoring approach are described below. As noted above, the City understands that the next version of the Phase II Permit may contain monitoring requirements substantially different from those envisioned in the current Phase II Permit. The City may revise these effectiveness questions and/or monitoring strategies after the next Phase II Permit has been issued. Question 1- Will retrofitting alleys with porous pavement substantially reduce runoff? Problem Statement/Description: Creation of impervious surfaces has been identified as a major cause of the flooding, water pollution, and channel erosion problems that often accompany urbanization (National Academy of Sciences 2008). Porous pavement is designed to allow rainfall to infiltrate into the underlying soil, thereby minimizing surface runoff and related flooding, water pollution, and channel erosion problems. The City must devote substantial resources to meet NPDES flow and water quality control standards. Other MS4s are likely having similar issues. Hypothesis: Catchments with alleys covered by porous pavement will generate less surface runoff than catchments with alleys covered by traditional pavement. Specific parameters or attributes: The City will identify two small catchments with similar land uses, soils, and topography. The alleys in one of the catchments will be repaved using pervious material. The City will monitor runoff volumes from each catchment area and compare the results. Expected modifications: If monitoring determines that the areas with porous pavement substantially reduce runoff volumes then the City will more likely install porous pavement sections in alleys. ---PAGE BREAK--- 5 Question 2- Will installation of rain gardens in road rights-of-way substantially reduce runoff? Problem Statement/Description: Nearly all of the existing roads in Puyallup are covered with impervious pavement. In some areas, road runoff is directed to adjacent grassy areas with limited potential for flow and pollutant attenuation. Installing rain gardens in these grassy areas could increase infiltration and sedimentation, thereby reducing flow volumes and pollutant loads. Rain gardens are low-lying, vegetated depressions with absorbent soils that promote infiltration. Rain gardens are a popular form of stormwater mitigation, as they are easy retrofits for existing developments and are well suited for small sites, such as rights-of-ways. Many other MS4s use rain gardens and therefore are likely to have similar questions regarding their effectiveness in reducing runoff from road rights-of-way. Hypothesis: Catchments with rain gardens in the rights-of-way will have less runoff than catchments with grass in the rights-of-way. Specific parameters or attributes: The City will identify two small catchments with grass-covered rights-of- way and similar land uses, soils, and topography. Rain gardens will be installed he rights-of-way in one of the catchments. The City will monitor runoff volumes from each catchment area and compare the results. Expected modifications: If monitoring determines that the areas with rain gardens substantially reduce runoff volumes then the City may install more rain gardens in rights-of-ways in the City.