1920 GRAND AVE Geotech Report 2022-10-25

Mr. Bill Messner ES-6132 October 5, 2018 Page 4 A factor of safety of 1.5 has been applied to the passive resistance value listed above. An earth pressure distribution for the active earth pressure condition is provided on Plate 3 (Earth Pressure Detail). Allowable soldier pile deflections for walls subjected to active earth pressures should be limited to one inch. Soldier Piles Soldier pile installation should be observed by a representative of ESNW to verify pile depths and soil conditions. Appropriate pile lengths and embedment depths shall be determined by the project structural engineer. 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. As indicated in the following Tieback Anchors section of this letter, soldier piles embedded at least 10 feet into dense native soils may be designed with an end bearing capacity of 10,000 psf. Timber Lagging Lagging should be installed in four-foot maximum lifts as the excavation is advanced. A representative of ESNW should observe the shoring excavation to assess the stability of the cut. The lagging should be backfilled as the excavation is advanced to minimize voids between the lagging and cut face and to reduce the potential for ground subsidence behind the shoring wall. Where sloughing of the excavation results in the development of a void behind the lagging, injection of lean-mix concrete into the voided area should be considered. If the shoring wall is designed as a temporary system, a 50-percent reduction in lateral earth pressure may be assumed. Permanent lagging may be designed with a 25-percent reduction in lateral earth pressure. Tieback Anchors Where necessary, tiebacks should be located as high on the wall as possible and should be designed based on the following preliminary parameters: • Allowable anchor pullout 1,500 psf(dense native soil) • Declination angle (from horizontal) 15 to 20 degrees • Embedment (minimum) 10 feet • Soldier pile end bearing capacity 10,000 psf (dense native soil) • No load zone See Plate 4 Earth Solutions NW,LLC