2621 ROCKEFELLER AVE Geotech Report 2022-10-25

I Icontaining less than 5 percent fines, may be compacted in loose lifts not exceeding12 inches e s when placed below 5 feet of the finished ground surface. Each lift must be compacted prior to placing the I subsequent lift. Prior to compaction,the backfill should be moisture conditioned to within 3 percent of } the optimum moisture content, if necessary. The backfill should be compacted in accordance with the criteria discussed above. Figure 4 illustrates recommended trench compaction criteria under hardscape, pavement and non-structural areas. Weather Considerations IDisturbance of near-surface soils should be expected if earthwork is completed during periods of wet weather. During dry weather the soils will (1)be less susceptible to disturbance, (2)provide better support for construction equipment,and(3)be more likely to meet the required compaction criteria. The wet weather season generally begins in Octo ber and continues through May in western Washington; however, periods of wet weather may occur during any month of the year. For earthwork activities 1 during wet weather,we recommend that the following steps be taken: • The ground surface in and around the work area should be sloped so that surface water is directed away from the work area. The ground surface should be graded so that areas of ponded .11 water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface 1 water from the work area. • Earthwork activities should not take place during periods of moderate to heavy precipitation. • Slopes with exposed soils should be covered with plastic sheeting. • The contractor should take necessary measures to prevent on-site soils and soils to be used as fill from becoming wet or unstable. These measures may include the use of plastic sheeting, sumps with pumps, and grading. The site soils should not be left uncompacted and exposed to moisture; Sealing the surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will help reduce the extent that these soils become wet or unstable. I • The contractor should cover all soil stockpiles that will be used as structural fill with plastic sheeting. 11 • Construction activities should be scheduled so that the length of time that soils are left exposed to moisture is reduced to the extent practical. jErosion and Sedimentation Control Potential sources or causes of erosion and sedimentation depend upon construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. Implementing an erosion and sedimentation control plan will reduce the project impact on erosion-prone areas. The plan should be designed in accordance with applicable City of Everett and/or -° state standards. The plan should incorporate basic planning principles including: I • Scheduling grading and construction to reduce soil exposure. "Ri • Revegetating or mulching denuded areas. 111 • Directing runoff away from denuded areas. • Reducing the length and steepness of slopes with exposed soils. . File No.12547-001-00 Page 7GECENGINEER I E.0 February 3,2006