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

Geotechnical Report - Revised Proposed Apartments: 1002, 1006, and 1008 Broadway Street, Everett, Washington May 12, 2015 Point loads located close to tltie top of the wall, such as outriggers of heavy ci-anes, may apply additional loads to the lagging. These loads, if applicable may need to be individually analyzed. We recommend voids behind the lagging be bscktilked with CDF. S.4 ECOLOGY BLOCK SIIORINC Ecology blocks consist of concrete blocks with a iypical dimension of 2 feet high, 2 feet deep and 6 feet long. Based on the encountered soil conditions, in our opinion, ecology blocks can Ue used to shore the lower portion of the west excavation with a maximum height of tluee blocks, or G feet, with a 6V:1H (Vertical:Ho�izontal) batter. The blocks should be placed in a running bond pattern and the space between the blocks and excavation backfilIed with clean crushed rock meeting the requirements for Permeable Baliast in the WSDOT Standard Specifications, Section 9-03.9(2) (WSDOT, 2014), or an approved equivalent. Clean rounded gravel such as pea gravel or washed gravel/drain rock should not be used to backiill the block wall. The base course of blocks should be embedcled at least one f'oot below the construction subgi•ade elevation. The grade above the wal) may be sloped at a 1 H:1 V inclination. The ecology block shoring may be placed in alignment with the walls of the building and can be used as the backl'orm for the permanent basement watls. The joints between the blocks will allow groundwater to seep tiu�ough the shoring. As the wall will be faced by the concrete basement walls, it will be necessary to provide drainage to collect the seepage and pi•event hydrostatic pressures from building up behind the wall and concrete facing. For this application, a geotextile s4ieet drain incorporating a filter fabric such as Miradrain b000, or equivalent, siiould be used. The sheet drain should connect to piping extending t}u•ough the basement wall thai connect to a collector pipe on the inside edge of the perimeter foundation. We recommend the ecology blocks be stockpiled on site before commencing with the excavation. This will allow for placing the blocks as the excavation progresses. PanGEQ personnel sliould also be on site to observe the stabi(ity of the exc�vation and to monitor the ecology block wall constiuction. 15-p43 1008 Broadway, Revised Page 12 PanGEO, [ne.