1130 RAINIER AVE WHOLE SITE DOCUMENTS 2016-01-01 MF Import

� Everett Housing Aulhority ��1ay 16, 2012 � J N 12080 Page 3 just above the existing grade. �Vhere overexcavations for the building foundations are expected to be approximately 6 feel or less, using conventional footings for the buildings that that are placed on the competent native soil or on slruclural fill placed over the competent nalive soil would be a standard (oundation option. However, �vhere deeper overexcavations would be needed to reach competent soil, avoiding the overexcavation and using a deep foundation system is likely a more economical system. Because the buildings are not tall and lhere is litlle slope at the site, �.ve believe lhat using driven pipe piles is a very feasible and economical foundalion system for this project; addilional inforinalion regarding the piles is given in a subsequent seclion of this reporl. Peat soil vias revealed in the test borings in approximately ihe area of ihe proposed eastern I;uildin9 and the eastern end of the soulhvdestern buddin9. T�is soil is highly crganic and thus is �-ery compressible. Based on the contlition of the lo�ver parking lol, it appears ihat settlemenl of the peat soil has be2n occurnng since fill soil was placed over it to construct ihe parking lol. SetUement of lhe peat will likely continue in the fulure; this would thus negatively aifect any tloor ;labs construcled for these bui!dings. For this reason, unless the peat is removed, the pipe piles should also be used to support slabs of these buildings. If a cra�vl space system is used, then the piles �vould just be needed for foundations. Projects involving placed against the engineer indicale in`ormation. small-diameter pipe piles otten includa the need (or lateral resistance from fill (oundations. Ii this is the case for this projecl, it is important that lhe structurel lhis requirement on lhe plans for the general and earthwork conlractor's Because of ihe existence of lhe peat soil on this site, it is Ilkely ihat some settlement of the ground surrounding pile-supported buildings will occur over time. In order to reduce the potentiai problems associated with this, we recommend lhe follotving: • Fill to the desired site grades severai months prior to constructing on-grade slabs, walk�vays, and pavements around the buildings. This allows the underlying soils to undergo some consolidation under the new soil loads before final c�ading is accomplished. Connect all in-ground utilities beneath the floor slabs to ihe pile-supported (loors or grade beams. This is intended to prevent utiliGes, such as sewers, from being pulled out of the (loor as the underlying soils setUe away irom the slab. Hangers or straps can be poured inlo the floors and grade beams to carry the pipinc�. The spacing of these supporting eloments will depend on the distance that the pipe material can span unsupported. • Censtruct all entrance �valk�vays as rein(orced slabs that are do�veied into lhe grade beam at the door thresholds. This will allow the walkways to ramp down and av.ay from the building as they setUe, wilhout causiny a downset al the threshold. • Isoiate on-grade elemenis, such as walkways or pavemenis, from pile-supported toundations and columns lo allow differential movement. The drainage andlor waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing ihrouyh concrete wails or slabs. Even in the absence of active seepage into and beneath structures, �vater vapor can migrate through walls, slabs, and f!oors from the surrounding soil, and can even be transmilted from slabs and foundation walls due to the concrele curing process. Water vaper also results from occupanl uses, such as cooking and GEOTFCH COMSULT�VTS. RJC.