9702 19TH AVE SE Geotech Report 2024-03-28

Pacific Ridge — DRH, LLC ES-7829.01 August 26, 2021 Page 8 Permanent slopes should be planted with vegetation to both enhance stability and minimize erosion and should maintain a gradient of 2H:1 V or flatter. The presence of perched groundwater may cause localized sloughing of temporary slopes. An ESNW representative should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations as necessary. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. 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 (minimum) 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 of and compaction. ** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction. 'Minimum relative compaction of 90% may be feasible for mass grading activities and should be evaluated by ESNW during construction. 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. In-situ and Imported Soil The in-situ soils encountered at the subject site have a high sensitivity to moisture and were generally in a moist condition at the time of exploration. Soils anticipated to be exposed on site will degrade if exposed to wet weather and construction traffic. Compaction of the soils to the levels necessary for use as structural fill may be difficult or impossible during wet weather conditions. Soils encountered during site excavations that are excessively over the optimum moisture content will likely require aeration or treatment prior to placement and compaction. Conversely, soils that are substantially below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. Areas of existing fill may be unsuitable for reuse as structural fill due to composition and/or deleterious material. An ESNW representative should determine the suitability of in-situ soils for use as structural fill at the time of construction. Earth Solutions NW, LLC