1815 13TH ST SEATTLE CHILDRENS NORTH CLINIC 2019-07-08

CENTRAL UTILITY PLANT PARKING LOT Everett,Washington Permanent Cut and Fill Slopes We recommend that permanent cut or fill slopes be constructed at inclinations of 2H:1V or flatter, and be blended into existing slopes with smooth transitions. To achieve uniform compaction, we recommend that fill slopes be slightly overbuilt and cut back to expose well-compacted fill. To reduce erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of grading. Until the vegetation is established, some sloughing and raveling of the slopes should be expected. This may necessitate localized repairs and reseeding. Temporary covering, such as clear heavy plastic sheeting,jute fabric, or erosion control blankets may be used to protect the slopes during periods of rainfall. Utility Trenches Trench excavation, pipe bedding, and trench backfilling should be completed using the general procedures described in the 2012 WSDOT Standard Specifications or other suitable procedures specified by the project civil engineer. The silts and clays, glacial deposits, and fill soils encountered at the site are generally of low corrosivity based on our experience in the Puget Sound area. Utility trench backfill should consist of structural fill and should be placed in lifts of 1 foot or less (loose thickness) such that adequate compaction can be achieved throughout the lift. Each lift must be compacted prior to placing the 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. Sedimentation and Erosion Control In our opinion,the erosion potential of the on-site soils is low to moderate. Construction activities including stripping and grading will expose soils to the erosion effects of wind and water. The amount and potential impacts of erosion are partly related to the time of year that construction actually occurs. Wet weather construction will increase the amount and extent of erosion and potential sedimentation. Erosion and sedimentation control measures may be implemented by using a combination of interceptor swales, straw bale barriers, silt fences and straw mulch for temporary erosion protection of exposed soils. Disturbed areas should be finish graded and seeded as soon as practicable to reduce the risk of erosion. Erosion and sedimentation control measures should be installed and maintained in accordance with the requirements of the City of Everett. Pavement Recommendations Subgrade Preparation We recommend that the subgrade soils in new pavement and parking areas be evaluated as described above in the "Subgrade Preparation" portion of the "Earthwork" section of this report. We recommend that the upper 12 inches of the existing site soils be compacted to at least 95 percent of the MDD estimated in general accordance with ASTM D 1557 prior to placing pavement section materials. If the subgrade soils are loose or soft, it may be necessary to excavate the soils and replace them with structural fill. A layer of suitable woven geotextile fabric Page 8 October 17,2012 GeoEngineers,Inc. File No.10738-010-00