1610 SE EVERETT MALL WAY Geotech Report 2022-10-25

Subsurface Exploration, Geologic Hazard, and Krebs Property Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations 9.2 Structural Fill Compaction 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 dry density using American Society for Testing and Materials (ASTM):D 1557 as the standard. Roadway and utility trench backfill should be placed and compacted in accordance with applicable municipal codes and standards. The top of the compacted fill should extend horizontally a minimum distance of 3 feet beyond the perimeter footings or pavement edges before sloping down at an angle no steeper than 2H:1V. Fill slopes should either be overbuilt and trimmed back to final grade or surface-compacted to the specified density. 9.3 Moisture-Sensitive Fill Soils in which the amount of fine-grained material (smaller than 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 favorable dry weather conditions. The on-site lodgement till sediments are suitable for use as structural fill, but generally contain significant amounts of silt and are considered moisture- sensitive. At the time of our exploration, portions of the till were observed to exhibit moisture contents over the optimum for achieving maximum compaction. These sediments are described on the attached logs as "very moist" or "wet." In addition, construction equipment traversing the site when the soils contain excessive moisture can cause considerable disturbance. If fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. 9.4 Structural Fill Testing The contractor should note that any proposed fill soils must be evaluated by Associated Earth Sciences, Inc. (AESI) prior to their use in fills. This would require that we have a sample of the material at least 3 business days in advance to perform a Proctor test and determine its field compaction standard. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in- place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. February 13, 2007 ASSOCIATED EARTH SCIENCES, INC. 7JP/Id-KE070023A1-Projects1200700231KEtWP Page 10