2.2.2 Geology and Soils

The depth to bedrock within the subwatershed varies from 200 to 400 feet.  Quaternary deposits ? the surficial material overlaying the bedrock – in the western lake area are generally high relief New Ulm loamy till common to the upper watershed, with pockets of peat and muck and a few isolated pockets of clay deposits.  The southeastern shores of Lake Minnetonka, especially within the Eastern St. Croix moraine, include large areas of sandy till and glacial outwash, as well as some areas of finely-stratified deposits.  Soils within the watershed are predominantly classified as Natural Resources Conservation Service Hydrologic Soil Group B (loamy soils with moderate infiltration potential) and D (clayey soils with very low infiltration potential) (see Figure 3).  The Group D soils are found in low-lying areas and are generally hydric, or showing indications of inundation (see Figure 4) or are in areas of mucky soils.  There are also scattered areas of Group A soils, sandy with high infiltration potential, mostly in the eastern subwatershed in areas dominated by sandy till or outwash.