Agenda - Council Work Session - 02/23/2021

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Over time, much of the naturally vegetated, wetland -rich landscape of the Lower Rum River watershed has been converted to residential and other developed land uses (see Section 2.3). Development and the associated increase in impervious surface (i.e., surfaces through which water cannot infiltrate) results in increased stormwater runoff rates and volumes. Imperviousness and land disturbance (e.g., construction) result in increased amounts of nutrients, chloride, sediment, and other pollutants carried in stormwater runoff (i.e., loading). Increased stormwater runoff rates and volumes resulting from impervious area also contribute to erosion, threaten existing infrastructure, and increase flood risk. During Plan development, the CAC identified direct (i.e., untreated) stormwater discharges to the Rum River as a concern. Development also limit the natural ability of the landscape to mitigate the negative environmental impacts of stormwater runoff by reducing infiltration and retention. Infiltration or retention of stormwater runoff is the most effective means of limiting the impacts of urbanization, as these methods reduce the total volume of runoff to the downstream receiving waterbodies. In areas of concentrated development, existing structures, utilities, and land ownership further restrict the opportunities for the LRRWMO and cities to implement cost-effective stormwater best management practices (BMPs). Redevelopment provides an opportunity to retrofit stormwater BMPs in areas that may not currently receive adequate treatment. Further development and urbanization of the LRRWMO is anticipated into the future (see Section 2.3), emphasizing the need for systems to mitigate the negative impacts of stormwater runoff, including regulation, education, and projects (e.g., best management practices, or BMPs). Each of the Cities within the LRRWMO maintains a Municipal Separate Storm Sewer System (MS4) permit that details measures that the cities use to mitigate the negative impacts of stormwater runoff (see Section 2.7.5). In addition, the LRRWMO implements performance standards to mitigate the impacts of development of stormwater runoff. Private developers, cities, the LRRWMO, and other partners have constructed BMPs to improve the quality and reduce the volume of stormwater runoff. Proper operation and maintenance of these BMPs is necessary to achieve the intended benefits. As stormwater management infrastructure continues to age, maintenance, repair, and eventual replacement of infrastructure may place additional financial burden on cities and owners of private infrastructure. The lakes, streams, and rivers within the LRRWMO are valued resources that provide recreational and ecological benefits. Protecting the water quality of these resources by reducing pollutant loading is key to ensuring these benefits. The sources of water pollution in the LRRWMO are many and varied. Potential pollutant sources in the watershed include permitted sources, potentially contaminated sites, leaking above- and below -ground storage tanks, unsealed wells, and non -point sources such as stormwater runoff (see Section 3.2.1). For 3-3