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TranSystems Corporation - LGM Construction

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8.2.4 <strong>Construction</strong> Considerations<br />

Where footings are located adjacent to below-grade structures, other new footings, or<br />

underground utilities, they should bottom below an imaginary 45 degree plane projected<br />

upward from the bottom of adjacent footings or underground utilities, in order to reduce<br />

imposing a surcharge pressure on them.<br />

Where underground utilities cross through or below perimeter footings, the trench<br />

backfill should consist of lean concrete, as discussed in the “Earthwork” Section of this<br />

report, in order to help reduce migration of water beneath the building.<br />

Concrete for footings should be placed neat against soil. It is important that exposed<br />

material in footing excavations be maintained in a moist condition until concrete is<br />

placed. If shrinkage cracks appear in the footing excavations, the excavations should<br />

be thoroughly moistened to close all cracks prior to concrete placement. If excessive<br />

shrinkage cracks develop, other mitigation measures may be required. Soft or loose<br />

materials, if encountered at the bottom of the footing excavations, should be removed<br />

and replaced with lean concrete or engineered fill.<br />

A Kleinfelder representative should check footing excavations for adequate bearing soil,<br />

adequate moisture of exposed soil, and proper cleanout of footing excavations before<br />

reinforcing steel is placed. Kleinfelder should also be present during any overexcavation<br />

performed for footings.<br />

8.3 2007 CBC SEISMIC DESIGN PARAMETERS<br />

8.3.1 Site Classification for Seismic Design Purposes<br />

For developing seismic design criteria recommendations, the characteristics of the soils<br />

underlying the site are important input to evaluate the site response. Based on our<br />

investigation, the site is generally underlain by a layer of very loose to loose sand<br />

ranging from about 13 to 19 feet bgs. Groundwater was encountered in our borings<br />

within the upper 10 feet bgs, although general regional groundwater in the site vicinity is<br />

less than 5 feet bgs. Based on the presence of shallow groundwater and some very<br />

loose to loose sand layers, the site has liquefiable soils that would generally indicate<br />

Site Class ‘F’ which typically needs a site-specific response analysis. However, the<br />

94240/1(OAK8R061)/es Page 22 of 29 June 13, 2008<br />

© 2008 Kleinfelder

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