The HHPLS identified the infiltration potential of the upland areas within the subwatershed as low to medium, with an area of high infiltration potential to the south and west of Langdon Lake in an area of ice-stratified sand and gravel till. Because of the organic nature of the soils in the wetland areas, in general infiltration potential there is variable (see Figure 16). The Hennepin County Geologic Atlas classifies most of the western subwatershed area as being of low sensitivity to pollution, while the area around Langdon Lake is variously medium to high to very highly sensitive, especially in the areas of gravel till deposits (see Figure 17).
Part of the Langdon Lake subwatershed has been designated by the Minnesota Department of Health as a Drinking Water Sensitivity Management Area (DWSMA) for a City of Minnetrista public well. The City of Minnetrista has completed its wellhead protection plan, and Figure 18 shows the DWSMA and associated Wellhead Protection Area for that well. While aquifer sensitivity is high in some parts of this DWSMA, the MDH has designated this area to be of low risk and low vulnerability to contamination of the drinking water supply. The County Well Index has records of fewer than 5 private, shallow wells within the subwatershed.