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Geotechnical Information: <br /> Grades on the site generally run from west to east. Runoff sheet flows across this property <br /> with a minimal offsite flow from the neighboring developed properties. A site visit was <br /> conducted October 12, 2022, and the weather was mostly sunny with temperatures in the <br /> high 60's. It hasn't rain for four month and the site was very dry. No signs standing water, <br /> or any storm issues were observed. Also, did not observe any downstream problems or <br /> issues. <br /> The soil hydrologic types for this site have been identified as Type C from the Snohomish <br /> County Soil Survey Map, and Soil Resource Report. This soil, Alderwood Urban Complex is <br /> mostly gravelly sandy loam with limiting layer to transmit water and very low capability for <br /> infiltration. Refer to APPENDIX C— SOIL RESOURCE REPORT for the area of this <br /> project. <br /> During the site visit, we conducted a site reconnaissance and excavated two pits. Also, tried <br /> to perform a Simple Infiltration Test on both Pit#1 and 2. <br /> Pit#1: Location is south of the existing house (location is marked on the plans). <br /> Excavated approximately 3.0' deep. The soils observed in the test pits generally consisted <br /> of the following: Top 6" to 8" consist of the grass surface/topsoil, 8" to 2.5' hard, compacted <br /> soils with a very hard layer at 3.0'. Soils consist of dense, brown, silty, fine to medium sand <br /> with gravel. We stopped digging at 3.0' due to refusal by a hardpan. Although the soils <br /> encountered and the presence of hardpan were good indication that infiltration is not <br /> feasible we went ahead and we attempted to perform an infiltration test. Filled the pit with <br /> water to about 6" from the top and an hour later the water level was not changed. <br /> Pit#2: Location is about 15' north of the south property line and about 40 feet west of the <br /> east property line (location is marked on the plans). Excavated approximately 3.0 ' deep, <br /> soils observed are similar to soils in pit#1. Also attempted to perform infiltration test and we <br /> had the same result as in pit#1. <br /> Based on the above information and soils types, infiltration of stormwater runoff is not <br /> feasible. <br /> The project proposes the use of dispersion system (BMP T5.12) for driveway runoff, and <br /> onsite dispersion trench system (BMP T5.10B) for runoff from roof areas. <br /> The use of these systems dispersion systems (BMP T5.12 and BMP T5.10B) as located <br /> and shown on the plans are suitable for this project area and should have no impact to the <br /> adjacent area. <br /> Attached in Appendix C are the soil logs for pit 1, and 2. <br /> Drainage Report—9227 4t"Ave W Everett,WA 98204 <br /> Nov. 10,2022 Page 8 <br />