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KLE/NFELOER �Bright People.Right Solutions. structural engineer should provide the final design floor slab thickness and reinforcement requirements. Care should be taken to place, consolidate, and cure concrete in accordance with American Concrete Institute (ACI) standards and criteria. Within the project area, the subgrade improvement alternatives discussed in Section 5.6.2 have performed well in reducing the potential for post-construction heave to within generally accepted or tolerable levels. These approaches are contingent upon our assumption that drainage criteria discussed in Section 5.11 will be implemented during and following construction. Poor drainage, inadequate landscaping, and leaking pipelines can still potentially trigger some isolated slab heave as the moisture content of the native clay increases. The degree and risk of potential heaving varies depending on the quality control followed during construction. If the preference is to provide a performance standard higher than currently assumed for the proposed project, the level of subgrade preparation should be increased and/or the floor slab should be stiffened by thickening the slab and/or reinforcing it with steel bars. Kleinfelder can provide revised recommendations to increase the performance standard, upon request. 5.7 EXTERIOR CONCRETE Per our discussion in Section 5.6.1, most of the near-surface soil underlying the site will likely consist of clay soils that can exhibit significant shrink-swell (expansion) characteristics, thus posing a risk for post-construction movement and cracking of exterior flatwork. In order to reduce this risk, the subgrade soil conditions in all areas to support exterior concrete flatwork, i.e., sidewalks and the like, should be prepared per the recommendations presented in Section 5.6.2. In some cases, isolated "edge" cracking or heaving forms along the outside portions of exterior flatwork because of seasonal or man-made wetting and drying of the subgrade soil. This potential can be reduced by placing lateral cutoffs, i.e., inverted curbs, heavy plastic membranes, or manufactured composite drains, along the outside edges of the flatwork. The lateral cutoffs typically extend vertically 12 to 18 inches into the subgrade soils. Another approach is to strengthen or stiffen the flatwork by increasing the thickness of the concrete and/or reinforcing the flatwork with steel bars rather than wire mesh. 20210067.001A/ST020R111447 Page 24 of 37 May 11, 2020 ©2020 Kleinfelder www.kleinfelder.com