3214 BROADWAY SEPA 017 - 004 Geotech Report 2025-04-14

American Property Develor.,ient ES-0599.05 January 16, 2015 Page 8 Updated January 22, 2015 Active Earth Pressures A typical earth pressure distribution for an Active Earth Pressure condition is provided on Plate 3 of this study. Allowable soldier pile deflections for walls subjected to Active Earth Pressures should be limited to approximately one-inch. At-Rest Earth Pressures At-Rest pressures should be used where the shoring system will support adjacent foundation loads, and where deflection of the shoring wall and adjacent ground subsidence must be minimized. Where some defection is determined to be acceptable, an earth pressure based on a value that is between the At-Rest and Active values may also be considered, as recommended by the geotechnical engineer. Recommendations for allowable soldier pile deflections can be provided once the alignment and proximity of shoring walls to adjacent structures has been established. The geotechnical engineer should review the shoring wall design, and provide supplement earth pressure and building surcharge recommendations, as appropriate. Where At-Rest Earth Pressures are applied, a triangular distribution of pressure similar to the distribution illustrated on Plate 3 should be used. Multiple Tieback Walls Where deeper shored excavations will be necessary to construct the garage levels, a multiple tieback wall may be necessary. As illustrated on Plate 4 (Multiple Tieback Wall), an apparent earth pressure distribution should be used to design multiple tieback walls. The following design parameters should be used for multiple tieback walls: • Apparent Earth Pressure 19H (psf), where "H" is the height of excavation • Slope Surcharge Hs/2 (ft.), where "Hs" is the height of slope* • Traffic Surcharge (where applicable) 70 psf, rectangular distribution • Preliminary Building Surcharge 125 psf (rectangular distribution)** *Add "Hs" to excavation height in calculating apparent earth pressure value. See Plate 4 for distribution of apparent earth pressure **Building surcharge values should be reevaluated based on further assessment of adjacent building foundation levels, proximity, and loading Soldier Piles Soldier pile installation should be observed by the geotechnical engineer to verify pile depths and soil conditions. If sloughing of the soldier pile excavation occurs, the contractor should be prepared to case soldier pile excavations, as necessary. Where groundwater seepage is encountered in excavations, localized sloughing should be expected. Earth Solutions NW,LLC