5.2. SR 08-08-2011 - Laserfiche WebLink

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No. 3 a 15-inch gravity sewer line would be required. For Scenario No. 1 a 10- inch diameter sewer would be recommended to serve the area along the west side of TH 10. For Scenarios No. 2 and No. 3 a 15-inch gravity sewer line is recommended for carrying the projected flows from the portion of the study area west of TH 10 to allow for potential future development south of the study area. Wastewater from the portion of the study area between TH 10 and the Burlington Northern Railroad could be conveyed north and connected to the existing 15-inch sewer just south of 171St Avenue that extends north to 173ra Avenue. For all three scenarios, a 10-inch gravity sewer would be large enough to convey the estimated peak hour flow from the portion of the study area between TH 10 and the Burlington Northern Railroad. However, because the current urban service area boundaries extend beyond the limits of the study area, a 12-inch sanitary sewer is recommended to provide additional capacity for future development. 19. Geologic hazards and soil conditions. a. Approximate depth (in feet) to groundwater: 13 minimum; 65 average Approximate depth (in feet) to bedrock: 151 minimum; 175 average b. Describe any of the following geologic site hazards to ground water and also identify them on the site map: sinkholes, shallow limestone formations or karst conditions. Describe measures to avoid or minimize environmental problems due to any of these hazards. Information from the MPCA indicates that the study area is not in an active karst area. No limestone, sinkholes or karst conditions are known at the site. c. Describe the soils on the site, giving NRCS (SCS) classifications, if known. Discuss soil granularity and potential for groundwater contamination from wastes or chemicals spread or spilled onto the soils. Discuss any mitigation measures to prevent such contamination. The soils within the study area, as in other areas of Elk River, are sandy and are conducive to infiltration. Most of the area has a hydrologic soils group of A with some areas of B/D. (See Item 17 for more information about soil infiltration rates.) This high infiltration rate can pose a risk to groundwater. Table 19-1 lists the soils present on the site and Figure 16-1 shows the location of these soils. The Minnesota Geological Survey indicated the bedrock for the majority of the site is between 151-200 feet below the surface. The Sherburne County Water City of Elk River Draft Alternative Urban Areawide Review July 2011 Page SI of 84