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The National Pollution Discharge Elimination System (NPDES) program is a congressionally mandated program under the Clean Water Act. The program is a comprehensive two-phased national program for addressing the non-agricultural sources of storm water discharges that adversely affect water quality. The program is implemented locally through the Oregon Department of Environmental Quality (DEQ). DEQ issues permits to applicable entities which participate in and/or oversee activities which are recognized as potential sources of pollutants. Municipal Separate Storm Sewers Systems (MS4), Industrial Activities and Construction Activities all potentially require an NPDES permit.
The City of West Linn obtained its first permit under Phase 1 of the NPDES program in 1995. The City operates under a MS4 system which means that all storm water is collected and conveyed in a storm sewer system separate from the sanitary sewer system. In 2008, the City of West Linn was approved for their next Phase 1 MS4 NPDES permit. The latest version of the NPDES permit was approved on March 16, 2012. West Linn is one of the many co-permittees that comprise of the Clackamas County Group. The other entities are: the cities of Gladstone, Milwaukie, Oregon City, Happy Valley, and Rivergrove; Clackamas County, Clackamas County Service Distric #1, and Surface Water Management Agency of Clackamas County. Together these Cities and County entities have also undertaken a Comprehensive Clackamas County NPDES MS4 Stormwater Monitoring Plan, which was updated June 30, 2013.
As part of the permit the City has developed a Surface Water Management Plan (formally called the Stormwater Management Plan), or SWMP, that outlines Best Management Practices (BMPs) that the City will implement to improve and conserve water quality, as well as, prevent harmful pollutants from contaminating stormwater runoff and entering the MS4. The nuts and bolts of this program include identification of major outfalls and estimating pollutant loadings; detecting and eliminating non-storm water discharges to the MS4; reduction of pollutants in runoff from industrial, commercial and residential areas; control storm water discharges from new development & redevelopment and regular maintenance of the public storm water collection/ treatments systems. Compliance is essentially achieved by implementing the approved Stormwater Management Plan. Each permit holder is required to report annually the procedures, tasks and best management practices achieved that benefit water quality.
Additionally, DEQ has set Total Maximum Daily Loads (TMDLs) for water bodies located in the Willamette River Basin. Currently there are three parameters of concern - (high) temperature, bacteria, and mercury. A TMDL Implementation Plan is required to address these parameters. West Linn's SWMP serves as the implementation plan for bacteria and mercury and our 2009 TMDL Implementation Plan addresses temperature.