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Pacific Ridge — DRH, LLC ES-7852.01 March 15, 2022 Page 7 Wet Season Grading If earthwork activities occur during wet weather, additional drainage measures, cement treatment of site soil, and/or the use of select fill material will likely be necessary. Additionally, measures to protect structural subgrades should be considered if exposed during wet weather. Site specific recommendations can be provided at the time of construction and may include leaving cut areas several inches above design subgrade elevations, covering working surfaces with crushed rock, protecting structural fill soil from adverse moisture conditions, and additional TESC recommendations. ESNW can assist in obtaining a wet-season grading permit if required by the governing jurisdiction. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway, permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and compacted during site grading activities should meet the following specifications and guidelines: • Structural fill material Granular soil* • Moisture content At or slightly above optimum** • Relative compaction*** 95 percent (Modified Proctor) • Loose lift thickness (maximum) 12 inches * Existing soil may not be suitable for use as structural fill unless at(or slightly above)the optimum moisture content at the time of placement and compaction. ** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. ***Relative compaction of 90 percent can be considered for mass grading activities. With respect to underground utility installations and backfill, local jurisdictions may dictate the soil type(s) and compaction requirements. Unsuitable material or debris must be removed from structural areas if encountered. Excavations and Slopes The following allowable temporary slope inclinations, as a function of horizontal to vertical (H:V) inclination, may be used. The following Federal Occupation Safety and Health Administration and Washington Industrial Safety and Health Act soil classifications and maximum allowable temporary slope inclinations may be used: • Areas exposing groundwater seepage 1.5H:1V (Type C) • Loose soil 1.5H:1V (Type C) • Medium dense native soil 1 H:1 V (Type B) • Dense to very dense "hardpan" native soil 0.75H:1 V (Type A) Earth Solutions NW, LLC