11807 SILVER LAKE DR 2024-01-05 - Laserfiche WebLink

JULY2022 I STORMWATER SITE PLAN 10 PERTEET 1.1 Site Soils According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Web Soil Survey (WSS), the project area is comprised of Alderwood-Urban land complex, two to eight percent slopes. This soil is in the hydrologic soil group B, is classified as "moderately well drained,' and the Ksat of the most restrictive layer is approximately 0.00 to 0.06 inches/hour. A brief geotechnical report (dated 12/04/2022, written by Materials Testing & Consulting, Inc.), was submitted to the City of Everett under separate cover. The boring logs indicate that native soils on -site are primarily gravel and or sand with varying degrees of silt. Borings were advanced to 15-23 inches and groundwater was only encountered at boring TP-7 at a depth of 18 inches. While the on -site soil classification appears suitable for exploring infiltration based best management practices (BMPS), the presence of silt combined with observed signs of erosion, sedimentation, channeli:ation, and perched stormwater, make further exploration unwarranted. See Section 4.2- Field Investigation for more information. Based on the limiting Ksat, the silt content noted in the baring lags, and Per eer s on -site observations, Perteet does not recommend infiltration BMPs beyond the use of permeable pavement, where proposed, without a more thorough geotechnical investigation. The proposed impacts do not result in flow control or water quality treatment thus such geotechnical investigation is not deemed necessary or appropriate at this time.