2320 RAILWAY AVE INTERWEST CONSTRUCTION INC Geotech Report 2023-02-17

I Interwest Construction Co.-Railway Avenue Improvements, Everett,WA Feb. 14,2019/Revised Feb. 7,2020 IGeotechnical Engineering Report P1486-T18 12 percent fines) sands. This material can be adequately reused as structural fill during most Iweather conditions. It should be expected that during extended periods of wet weather that some of the on-site soils will I become saturated from shallow groundwater. The contractor should be prepared to spread and windrow these soils to the extent necessary to dry them back to a condition suitable for compaction. Any soils too wet to compact should be exported from the site. I We recommend that a representative from our firm be present during backfilling. Our representative will evaluate the adequacy of the subgrade soils and identify any areas needing Ifurther work, perform in-place moisture-density tests to determine if the work is being done in compliance with the compaction specifications and the intent of our recommendations,and advise on any modifications to procedure which might be appropriate for the prevailing conditions. 4_3 Asphalt Pavement I Since asphalt pavements will be extensively used in this project,we offer the following comments and recommendations for pavement design and construction. ISubgrade Preparation: All soil subgrades should be thoroughly compacted,then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over excavated to a minimum depth of 12 inches and Ireplaced with a suitable structural fill material. All structural fill should be compacted according to our recommendations given in the Structural Fill section. Specifically, the upper 2 feet of soils underlying pavement section should be compacted to at least 95 percent(based on ASTM D-1557), d so below 2 feet should be compacted to at least percent. Pavement Materials: For the base course, we recommend using importe wased crued ro , suchan as Crushed Surfacing Base Course per WSDOT Standard Speci I I fication 9 h03.9(3)but with ck a fines contentils of less than 5 percent passing the No. 200 Sieve. For the subbase course, we recommend using imported, clean, well-graded sand and90 gravel such as "Ballast" or sh"Gravel Borrowall " per WSDOT Standard Specifications 9-03.9(1) and 9-03.14, respectively. IConventional Asphalt Sections: A conventional pavement section typically comprises an asphalt concrete pavement over a crushed rock base course. We recommend using the following I conventional pavement section, or thicker if required by the City of Everett: Minimum Thickness Pavement Course Driveways,Truck Parking,and High Traffic Areas Asphalt Concrete Pavement 4 inches Crushed Rock Base 8 inches Granular Fill Subbase 24 inches IMigizi Group, Inc. Page 10 of 13 .