3620 BROADWAY VERIZON 2019-01-11

l f Geotechnical Engineering Evaluation NGA File No,983917 Stadium Flowers Addition March 10,2017 Everett,Washington Page 5 Specific development plans for the site were not available at the time this report was prepared. Proposed grading within should minimize cuts and fills on the sloping potions of the site. All cuts and fills should be supported using retaining walls. We should be retained to review grading and retaining wall plans once development plans are finalized. Fill should be placed according to engineering analysis and specific recommendations by NGA. We recommend that construction take place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays could be expected due to the wet.conditions. Additional expenses could include the need for potentially placing a blanket of rock spalls on exposed subgrades, construction traffic areas, and paved areas prior to placing structural fill. We do not recommend the use of the anthropogenic on-site soils as structural fill, as they will be very difficult to compact to structural fill specifications. The underlying native`clean' sand may be used given moisture conditions are carefully controlled to optimum levels during compaction. Further information has been included within the Structural Fill subsection of this report. We should be retained to evaluate proposed structural fill materials prior to construction. We recommend that temporary and final site grading be designed to direct surface water away from existing structures. We recommend that all stormwater generated on the site be collected in tightlines and transported to an appropriate stormwater system. This is further described in the Site Drainage subsection of this report. We recommend that NGA be retained to review final project plans and provide consultation regarding structure placement, site grading, and foundation support. We also recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and foundation installation activities comply with contract plans and specifications. Erosion Control and Slope Protection Measures The erosion hazard for the native, on-site soils are listed as slight, but the actual hazard will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site. Stockpiles NELSON GEOTECHNICAL ASSOCIATES, INC.