Laserfiche WebLink
Inwood 10 LLC <br />Project B14-08413 <br />December 3, 2014 <br />Page 13 <br />D.7.Stormwater Management <br />Based on the provided conceptual sketch, it appears the design and construction of stormwater <br />management features are part of the development. These features appear to be large infiltration basins <br />located in the southwest corner of the site in the vicinity of soil boring ST-4 and near the center of the <br />development in the vicinity of AET’s soil borings 4 and 5. The soil profiles at soil boring locations ST-3 and <br />ST-4, dependent on final grades, may provide challenges to infiltration. Typically, the profiles in these <br />areas have layers of silty clayey sand, clayey sand and sandy lean clay which are not conducive to high <br />infiltration rates. AET boring 5 encountered sand with silt and sand with gravel 4 feet below the surface <br />to boring termination. This location may yield higher infiltration rates. Infiltration rates were estimated <br />for some of the soils we observed in our soil borings and are listed in Table 2. <br />Table 2. Estimated Design Infiltration Rates Based on Soil Classification <br />Soil Type <br />Infiltration Rate * <br />(in/hr) <br />Sands with less than 12% fines <br />Poorly graded or well graded sands 0.8 <br />Silty sands, silty gravelly sands 0.45 <br />Silts, very fine sands, silty or clayey fine sands 0.2 <br />Clayey sands and clays 0.06 <br />*From Minnesota Stormwater Manual Section 12.8 with December 16 updates. Rates may differ at individual sites. <br />In any case, infiltration rates can be calculated based on field testing with Double Ring Infiltrometer <br />testing (ASTM D3385). Additional soil borings and geotechnical evaluation should also be performed in <br />infiltration basins once the location and grades are determined. This geotechnical evaluation does not <br />constitute a review of site suitability for stormwater infiltration or evaluate the potential impacts, if any, <br />from infiltration of large amount of stormwater. <br />D.8.Additional Evaluation <br />This preliminary geotechnical evaluation is not considered sufficient to provide detailed geotechnical <br />design recommendations for the commercial buildings. Once the location, framing system, structural <br />loads, building layout, etc. have been finalized for each structure, additional borings and evaluation <br />should be done. The information contained in this report should be reviewed as part of the design <br />evaluation.