4841 GLENWOOD AVE 2021-06-09 - Laserfiche WebLink

Retaining Wall Recommendations Page 3 August 21,2019 Everett,Washington RGI Project No.2016-072 modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. Excavations All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse.The site soils consist of existing fill soils and very dense native soils. Accordingly, for excavations more than 4 feet but less than 20 feet in depth,the temporary side slopes should be laid back with a minimum slope inclination of 1.5H:1V(Horizontal:Vertical)in the existing fill and 3/4H:1V in the native soils. In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately,the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. Structural Fill RGI anticipates that the native soils will be reusable as structural fill provided they can be moisture conditioned and compacted. The native soils are moisture sensitive and will require moisture conditioning(drying out) prior to use as 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 may be necessary to import soils to complete the earthwork. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level 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). The site soils may require moisture conditioning prior to use as structural fill and we expect some of the onsite soils will need to be exported. If the on-site soils are or become unusable, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill in wet weather. The fines content can be increased to 15 percent in dry weather conditions. Table 1 Structural Fill Gradation U.S.Sieve Size Percent Passing 4 inches 100 No.4 sieve 75 percent No. 200 sieve 5 percent * *Based on minus 3/4 inch fraction. Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 10 inches and compacted as specified in Table 3. The soil's maximum density and optimum moisture should be determined by ASTM D1557. 111 I Ill RILEYGROUP