5700 23RD DR W 2018-06-28 - Laserfiche WebLink

November 29,2016 Project No.T-5922-6 3.3 Groundwater We observed light, perched groundwater seepage in Test Pits TP-101 and TP-102 at depths of 2.5 feet and 2 feet, respectively. Perched seepage was also noted in Test Pits TP-2 and TP-4 at depths of 6 inches and one-foot below November 2010 ground surface elevations. Previously excavated Test Pit TP-3 observed groundwater seepage within the Advance outwash sands at a depth of 10.5 feet below the previous surface elevations. Fluctuations in groundwater seepage levels will occur and should be expected on a seasonal and annual basis. Typically,groundwater seepage reaches maximum levels during and shortly following the wet winter months. 4.0 GEOLOGICALLY HAZARDOUS AREAS 4.1 Landslide Hazard Areas We reviewed the criteria for landslide hazard areas contained in Section 19.37.080A.1. of the City of Everett Municipal Code(EMC). The site lies within an area shown on City of Everett-Landslide Hazard Critical Areas Map 2 as having a low landslide hazard(slopes<25%in"other" geologic units). Though 15 percent or greater slopes exist at the site,the slopes were created through past legal grading activities and are therefore not considered landslide hazard areas per Section 19.37.080A.1. of the EMC. Based on our on- site observations of the site slopes, subsurface explorations, and document review, it is our opinion that the site does not meet the criteria of a landslide hazard area as defined by the EMC. 4.2 Erosion Hazard Areas Review of the City of Everett — Erosion Hazard Critical Areas Map 3 indicates that the project site is located within an area with all slopes less than 25 percent having a low erosion hazard. Existing site slopes are inclined at approximately 33 percent; however,were constructed during past legal grading activities at the site. In addition, the slopes are thickly vegetated with grasses and showed no indications of erosion or soil instability. In light of the above, it is our opinion that the site is not an erosion hazard area as defined by the EMC. The site soils will be susceptible to erosion when exposed during construction. In our opinion, proper implementation and maintenance of Best Management Practices (BMPs) for erosion prevention and sedimentation control will adequately mitigate the erosion potential in the planned development area. Erosion protection measures as required by the City of Everett will need to be in place prior to and during grading activity on the site. Page No.3