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resources is a challenge, particularly considering the urban nature of the <br />RWMWD. Water quality is closely linked to land use and conditions in the <br />surrounding watershed. Stonnwater runoff can carry significant amounts of Current and historical water <br />sediment and phosphorus from the watershed into the water body, along with quality data informs the <br />' <br />other pollutants. As urbanization continues, the resultant land disturbance and District <br />s water resource <br />management decisions. <br />additional impervious surfaces (e.g., parking lots, roofs, roads, and driveways) <br />increase the amount of pollutants carried in stormwater runoff. Projects are successfiil <br /> in maintaining or <br />Water quality ponds and other BMPs are effective in removing particulate phosphorus improving water quality <br />in nmoff. However, the ponds require significant land resources and are relatively as demonstrated by water <br /> <br />ineffective at removing soluble phosphorus, which continues to be problematic quality trends. <br />for several RWMWD lakes. Due to the difficulty in removing soluble phosphorus The District understands and <br /> <br />from stormwater runoff and surface waters, it will be necessary to explore innovative maintains water quality to <br />support the existing uses of <br />BMPs and treatment techniques in the future to achieve water quality goals. each lake. <br />The RWMWD is giving special consideration to stormwater infiltration and water quality improvement <br />chemical treatment to minimize soluble phosphorus. The following paragraphs projects are appropriately <br />describe the benefits and challenges associated with these two BMPs. maintained and fimctional. <br /> <br />a _ Infiltration is effective in removing fine sediment Impaired water bodies are <br />removed from the Minnesota <br />and pollutants,. while also providing groundwater recharge and reducing Pollution Control Agency's <br />runoff volume and peak discharge. Successful infiltration basins require (MPCA) impaired waters list. <br />soils with moderate to high infiltration rates and suitable groundwater levels District office site is <br />(i.e., not too high). hlfiltration of stormwater is also dependent on available maintained to demonstrate <br />land area. Since much of the RWMWD is considered fully developed, it is ~ BMPs and monitored for <br />difficult to obtain land sufficient to treat stormwater runoff through infiltration, long-term perfom,ance. <br />particularly considering the extra space required for pretreatment of inflows. District rules and standards <br /> <br />In addition to the physical constraints, there are often public misconceptions are successfully implemented <br />i <br />i <br />i <br /> <br />to overcome such as fears of potential groundwater contamination, structural ~ to ma <br />nta <br />n or <br />mprove water <br />qua[iry. <br />problems with roadways and buildings, and increased water problems in New erosion and sediment <br />basements and underground levels of buildings. These public perceptions can <br />~ control practices and <br />be addressed through project design or education efforts. innovative stormwater BMPs <br /> <br />While implementing are used on construction <br />i <br /> tes. <br />s <br />BMPs may be effective in reducing phosphorus loading from the watershed, <br />intental hos horus sources uni ue to each water bod ma still cause <br />P p q Y y Permit compliance improves <br />through contractor education <br />phosphorus levels to be higher than desired. Currently, available treatment and effective inspection and <br />techniques for removing soluble phosphorus from surface waters are enforcement. <br />quite limited. Chemical treatment is an option, typically in the form of i _ _ Research completed by the <br />alum treahnent. However, chemical treatment is expensive, and the public District, or in cottaboration <br />perception of chemical use in surface waters is often negative. with others, advances <br /> understanding of stormwater <br />Another major deterrent is the cost associated with implementing BMPs and BMPperformanceand <br />other treatment technologies. Since much of the RWMWD is fully developed, watershed science. <br />improvements in water quality often require significant investments to <br />retrofit existing public and private infrastructure and acquire land for BMP <br />implementation. <br />www. rwmwd.org Page 4 <br />