10930 HOLLY DR Geotech Report 2025-08-08

Helix Design Group,Inc.-Greenwood Heating&Air Conditioning,Everett,WA April 22,2022 Geotechnical Engineering Report Z0219 compacted to at least 95 percent(based on ASTM D-1557), and all soils below 2 feet should be compacted to at least 90 percent. Pavement Materials: For the base course, we recommend using imported crushed rock. For the subbase course, we recommend using imported, clean, well-graded sand and gravel such as recommended in Section 4.6. Conventional Asphalt Sections: A conventional pavement section typically comprises an asphalt concrete pavement over a crushed rock base course. Using the estimated design values stated above, we recommend using the following conventional pavement sections: Minimum Thickness Pavement Course Parking Areas Driveway Areas Areas Subject to Frequent Truck Traffic Asphalt Concrete Pavement 2 inches 3 inches 4 inches Crushed Rock Base 4 inches 6 inches 8 inches Granular Fill Subbase 12 inches 12 inches 12 inches Compaction and Observation: All subbase and base course material should be compacted to at least 95 percent of the Modified Proctor maximum dry density (ASTM D-1557), and all asphalt concrete should be compacted to at least 92 percent of the Rice value (ASTM D-2041). We recommend that an MGI representative be retained to observe the compaction of each course before any overlying layer is placed. For the subbase and pavement course,compaction is best observed by means of frequent density testing. For the base course, methodology observations and hand- probing are more appropriate than density testing. Pavement Life and Maintenance: No asphaltic pavement is maintenance-free. The above-described pavement sections present our minimum recommendations for an average level of performance during a 20-year design life; therefore, an average level of maintenance will likely be required. Furthermore,a 20-year pavement life typically assumes that an overlay will be placed after about 10 years. Thicker asphalt and/or thicker base and subbase courses would offer better long-term performance but would cost more initially; thinner courses would be more susceptible to "alligator" cracking and other failure modes. As such, pavement design can be considered a compromise between a high initial cost and low maintenance costs versus a low initial cost and higher maintenance costs. 4.7 Structural Fill The term"structural fill"refers to any material placed under foundations,retaining walls,slab-on- grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock, crushed rock,well-graded mixtures of sand and gravel(commonly called"gravel borrow"or"pit- run"),and miscellaneous mixtures of silt,sand,and gravel. Recycled asphalt,concrete,and glass, Migizi Group,Inc. Page 14 of 16