1329 MADRONA AVE Geotech Report 2022-10-25

Subsurface Exploration,Geologic Hazard,and Janowicz Property Geotechnicol Engineering Report Everett, Washington Preliminary Design Recommendations • 10.1 Subgrade Preparation Before fill is placed, any cotluvium or landslide deposits within proposed fill areas should be removed. After overexcavation/stripping has been performed to the satisfaction of the geotechnical engineer/engineering geologist,the upper 12 inches of exposed ground should be recompacted to standard firm and unyielding condition. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. 10.2 Structural Fill Type, Placement,and Compaction • After recompaction of the exposed ground is approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non-organic soil,acceptable to the geotechnical engineer,placed In maximum 8-inch loose lifts with each lift being compacted to at least 95 percent of the modified Proctor maximum density using ASTM D-1557 as the standard. In the case of roadway and utility trench filling, the backfill should be placed and compacted in accordance with current municipal standards. The top of the compacted fill should extend horizontally a minimum distance of 3 feet beyond the locations of building footings or roadway edges before sloping down at a maximum inclination of 2H:1V, 10.3 Fill on Slopes If fill is to be placed on slopes steeper than 5H:1V, the base of the fill should be tied to firm, stable subsoil by appropriate keying and benching that would be established in the field to suit the particular soil conditions at the time of grading. The keyway.will embed the toe of the new fill into the hillside and should be at least 8 feet wide. Level benches would then be cut horizontally across the hill following the contours of the slope. No specific width is required for the benches,although they are usually a few feet wider than the dozer being used to cut them. An AESI representative should observe any hillside fills on a full-time basis during construction. • 10.4 Monitoring The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. Use of moisture-sensitive soil in structural fills should be limited to May 10,2018 ASSOCIATED EARTH SCIENCES,INC. NS/W-170649E002-2-Projects1201706491KEOP Page 13