1315 PACIFIC AVE 2018-01-01 MF Import

There may be problems with the stability of the soldier pile holes due to the upper loose fill conditions and perched groundwater. The contractor shall be prepared to use a slurty or to cazc the hole to see that the hole docs not collapse during the pile construction. Concrete for the soldier piles shall be placed by tremie at the bottom af the hole until the concrcte is above the goundwater levcl to reduce segregation of the concrete. 'I'he contractor should also bc prepared to dwl with possible debris and other obs[ructions in the fill soils during drilling. Laqging. Wc rccommend that the temporary timber lagging thickness(roughcut)be sized using the Uble below as a function of soldier pile clear span and excavation depth. The lagging thicknesses presented in the following table arc based on procedures oudined in the Federal Highway Adminislration's Geotechnical Lngineering Circular No.4 and on expericnce from similar excavations. Iboa��d�d�aOyNp 71�IoMn�(�eu01�aA)lor CNn�M d: � 5h�t �h�t 1fNt �Mt •fNt 1�MR 0 to 25 2 inches 3 inches 3 inches 3 inches 4lnches 4 inches 25 to 700 3 inches 3 inches 3lnches 4 inches 4 inches 5 inches Thc spacc bchind the lagging should be filled with soil or permcable sand slurry as soon aa pmctical. Placcmcnt of this malerial will help reduce thc risk of voids dcvcloping behind the wall and rcsultant damagc to cxisting improvcments locatcd bchind thc wall. The workmanship associated with lagging installation is important for maintaining the imegrity of the cxcavation. Lagging should be installed promptly aflcr cxcacation, especially in arcas whcrc perched groundwater is present or where clean sand and gravcl soils arc present and caving soils conditions am likcly. Urainage. A suitablc drainagc system should bc installcd to prcvcnt thc buildup of hydrostatic groundwatcr pressures bchind thc soldicr pile and lagging wall. It may bc necessary to cut wcep holes through thc lagging in wet arcas. Scepage (lows at the bottom of thc cxcavation should be contained and controlled. Drainage should be providcd at thc base of thc wall and bcneath the Ooor slab as described in follou•ing sections"Slab-on-Grade"and"Subsurfacc Walls." Underpinntnp of Adjecent Structuros Thc foundation of thc Snohomish Health District building may not cxtend to the dcpth of the proposed cxcavation. The shoring walls may necd to bc Jesigned to support the loads from adjacent Snohomish Health District building. The shoring wnlls can resist the loads as lateral surchargcs, comp�ted using f'igure 5, or as underpinning. Undeminning transfcrs loads to thc shoring system directly, as vertical surchargcs., Direct undcrpinning can bc designed using cast-in•place concrcte support or convcntional slant pile �echniqucs dcscribcd bclow: 1. Gxcavatc to thc cxisting foundation clevation, 2. Drill a shafl for thc soldicr pilc at a battcr on lhc ordcr of 2H:12V (actual baner will depend on thc soldicr pilc Icngth), 3. Rcam thc sidc of thc soldicr pilc shafl locatcd bclow thc cxisting foundation, 4. Install the soldier pilc and align it vertically bclow the exis�ing foundation, 5. Place strucwral concrete in thc soldier pile shafl�o the elevation of the planned excavation, 6. Placc Ican concrcte in Ihe upper portion of the soldier pile shaR, i�i�,�,,. nn�-nni-nn Pa,4e 8 GtoEMe�rt[a� hmr L.;OOR �Z