4201 RUCKER AVE COMMUNITY HEALTH CENTER 2019-04-10

Geotechnical Engineering Report 6 May 25,2017 Central Everett CHC,Everett,Washington RGI Project No.2017-094 must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.3 SITE PREPARATION After removal of the existing improvements and prior to placement of structural fill for new pavement areas, RGI recommends proofrolling the pavement subgrades and areas to receive structural fill. These areas should be proofrolled under the observation of RGI and compacted to a firm and unyielding condition in order to achieve a minimum compaction level of 95 percent of the modified proctor maximum dry density as determined by the American Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557). Proofrolling and adequate subgrade compaction can only be achieved when the soils are within approximately ± 2 percent moisture content of the optimum moisture content. Soils may be proofrolled with a heavy compactor, loaded double-axle dump truck, or other heavy equipment under the observation of a RGI representative. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather, if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond what would be expected during the drier summer and fall months. 5.2.4 STRUCTURAL FILL The excavated soil will be suitable for use as structural fill if the moisture can be properly controlled. The native soil is moisture sensitive and will be difficult to compact if it is wet. If the construction occurs in winter, it is necessary to import clean, granular soils to complete site work that meets the grading requirements listed in Table 2. Table 2 Structural Fill Gradation U S Sieve Slze Percent sstn 4 inches 100 3/4 inch 70 minimum No.4 35 to 60 No. 200 Oto 5* *Based on minus 3/4 inch fraction. I ►, RILEYGROUP