1901 W MUKILTEO BLVD Geotech Report 2022-10-25

Scriven Residence Improvements-REVISED NGA File No 974316 1901 West Mukilteo Boulevard November 29,2016 Everett,Washington Page 9 water from flowing off the site. Stockpiles should be avoided. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential for areas not stripped of vegetation should be low to moderate. Disturbed areas outside of the proposed development areas should be replanted with vegetation at the end of construction. The vegetation should be maintained until it is established. Final grading should incorporate permanent erosion control measures and should be designed to route stormwater runoff to appropriate discharge locations away from the structures and sloping ground. Protection of the steep slope should be performed as required by the City of Everett. No material of any kind should be placed on the slope or be allowed to reach the slope, such as excavation spoils, lawn clippings, and other yard waste, trash, or soil stockpiles. Replacement of vegetation should be performed in accordance with City code. Any future proposed development within or near the slope should be the subject of a specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slope either during construction or on a permanent basis after construction has been completed. All irrigation systems on or near the slope should be avoided. Future yard waste, grass clippings, or any other waste material or household trash should never be cast over the slope or piled near the walls. Such activity could lead to future slope instability. Additionally, drainpipes associated with the new retaining walls and existing residence, should all be tightlined to an approved stormwater management system, as described later in this report. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping any loose soils to expose medium dense or better native soil in hard surface areas. Also, the top of the slope could be cut down a few feet using large excavator equipped with smooth buckets. The stripped materials should be removed from the site. Stockpiles should be kept away from the top of the steep slopes and should be covered with plastic during wet weather. If the exposed subgrade, after site stripping, should appear to be loose, it should be compacted to a non- yielding condition. Areas observed to pump or weave during compaction should be over-excavated and replaced with properly compacted structural fill or rock spalls. If loose soils are encountered in the subgrade, the loose soils should be removed and replaced with rock spalls or granular structural fill. If NELSON GEOTECHNICAL ASSOCIATES, INC.