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Oversize Culvert and Redztced Slope at Outfall: The last section of culvert will be <br />enlarged from 21 -inches to 36-inches and include an apron and rip-rap to lower velocities <br />and dissipate the energy at the discharge point. This will minimize the potential for scour <br />and erosion. <br /> <br />Directional Boring to Install Culvert: If possible, the culvert will be placed within the <br />river bank by directional boring rather than an open cut. This will reduce the need to <br />remove shoreline vegetation and will minimize the area of disturbance. Erosion control <br />measures will be implemented where soil is disturbed. All disturbed areas will 'be <br />replanted to native trees, shrubs, grasses and forbs and if appropriate, a temporary cover <br />crop will be established. <br /> <br /> Item 13 Mitigation Element. Because the RTC site is within a DWSMA, special <br /> precautions are needed to protect groundwater resources. To make sure this occurs, any <br /> discharge of runoff into an area dedicated to infiltration will be pre-treated through such <br />· practices as particulate settling, vegetative filtration, skimming, installation of compact, <br /> sub-grade treatment (ex. catch basin inserts, cyclonic separators, filters), and various <br /> types of pre-treatment soil filtering systems. These practices will be routinely maintained <br /> and inspected to make sure these pre-treatment practices do not Provide a pathway for <br /> contamination of groundwater. Areas that are potential major sources of contamination <br /> ("hot-spots") will be identified during construction and special precautions added. These <br /> areas would include any location where pollutant-spills are more likely to occur (service <br /> stations, public workS/police/fire fueling operations, significant chemical storage).' <br /> <br />Within WHPAs, the use of conventional underground storage tanks to store anything <br />other than water is restricted, tf underground tanks are utilized in these areas they must <br />be double-walled with interstitial sensors and a network of monitoring wells must be <br />installed to assess potential groundwater contamination. In addition, an emergency <br />response plan should be developed for the immediate remediation of any spills or leaky <br />tanks. <br /> <br />When assembling the issues that Were to be addressed as part of this AUAR, it was noted <br />by the Anoka Conservation District and by the DNR that there is a possible connection <br />between the increased demand for municipal groundwater and the observed lowering of <br />wetlands in the vicinity of Municipal Wells 3, 4 and 5. Appendix F was prepared to <br />assess' the general magnitude of the problem and the solutions required to address the <br />issue. It is now apparent that the wetlands in question experience natural drying during <br />periods of relative low precipitation. The photographic history included as part of the <br />Wetland Delineation report shows wetlands in the vicinity of the RTC site disappearing <br />during the mid to late 1980's which is pr/or to the development of the municipal wells. <br />This same phenomenon occurs again in the mid to late 1990's and prior to the installation <br />of Wells 4 and 5. The evaluation also found, as stated earlier, that drawdown levels in the <br />FIG unit are minimal and, therefore, could not be influencing the wetlands. To verify <br />these finding, however, it is recommended that long tenn monitoring be performed. <br /> <br />241 <br /> <br /> <br />