1004 BROADWAY EVCC STUDENT HOUSING - PUBLIC WORKS 2017-01-13

Geotecl�nical Repori - Revised Proposed Apartments: 1002, 1006, and 1008 Broadway Street, Everett, Washulgton May 12, 2015 5.2 TEMPORARY SHORING ln our opinion, soldier pile walls with timbei• lagging or ecology block walls arc appropriate temporary shoring options. The shoring system should be designed to provide adequate protection for the workers, adjacent stiuctures, utilities, and other facilities. Excavations shoutd be performed in accordance with the current requireinents of WISHA. Construction should proceed as rapidly as feasibte, to limit the time temporary excavations are ope�i. 5.3 SOLDIER P[LE TEi�iPORARY SEIORINC Soidier pile temporary shoring consists of vertical stee] beanls, typically spaced fi�om 6 to 8 feet apart along the proposed excavation alignment, spanned by timber lagging. Prior to the start of excavation, the steel beams are installed in holes drilled to a design depth and then backfilled with lean mix or structural concrete. As the excavation pr•oceeds downward and the steel piles are subsequentIy exposed, timber lagging is installed between the piles to further stabilize the walls of the excavation. Tiebacks are typically used for wall heights greater tlian about l 2 feet ta achieve a more economical design. With the planned excavation extendin� to a maxi�riirin cllepth of �tbout l0 fect, wc do not anticipate tie-backs will be neccicd. 5.3.1 Wa!! Design Yararueters The earth pressures depicted on Figure 3 may be used for the shoring desi�n. The vertical capacity of the soldier piles should be deternzined using an allowable skin friction value of 0.5 ksf for the portion of the pile below the bottom of the excavation, and an allowable end soil beai-ing capacity value of 10 ksf. _5.3.2 Lagging Lagging design recoinmendations are presented on Figure 3. Lagging located within 10 feet of the top of the shoring which may be subjected to surcharge koads from constivction equipment or matet7a] stoi-age should be designed for an additional uniform lateral surcharge pressure of 200 ps£ This pressure approximately corresponds to a vertical uniform surcharge Ioad of 500 psf at the top of the wall. I S-04S 1003 Broadway, Rcviscd Page 1 1 PanGEO, Inc.