5109 CHINOOK DR 2018-12-21 - Laserfiche WebLink

2. EXISTING CONDITIONS SUMMARY The entire property consists of 0.38 acres. Runoff generated from the existing site sheet flows primarily in the northeastern direction onto the adjacent parcels. This project will not affect any off-site flows from passing through or around the site as in the existing conditions. Land use around the site is primarily single-family homes. The parcel associated with this project currently has no structures, but there is a slab on-site from an old garage. The grades on the site, in the area of the proposed SFR, are moderate and average approximately 11% down to the northeast. The vegetation found on the existing property consists of lawn and brush. A geotechnical engineering report, prepared by Battermann Geotechnical Consulting Pilo, which was prepared for the adjacent lot, indicates that there is a consistant layer of fine to medium sand to a depth of 6-7 feet below grade. The geotechnical report also state that"It is our opinion that a properly developed infiltration trench will allow the majority of storm water runoff to infiltrate back into the ground." USDA Web Soil Survey data was also looked at. The project site was shown to have Alderwood-Everett gravelly sandy loarns by the USDA website. General site slopes, in the area of disturbance, are moderated and average approximately 11% percent. Based on the existing soil information and the setbacks of the proposed improvements from any of the property lines or critical areas there is little potential for erosion or sedimentation during construction assuming the basic BMPs included in the SWPPP are installed and maintained properly. Refer to Figure 2 for an existing basin map. Chinook Dr SFR 17-0802 Revised: October 2017 Page 4