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KLE/NFELOER �Bright People.Right Solutions. When reference is made to swell or heave potential, it should be recognized that there also exists a potential for shrinking or settlement to occur due to decreases in soil moisture content or drying of the soil. We understand that the proposed structure will employ a floor slab with interior and exterior bearing wall/column footings. Given this system, several approaches can be taken to improve/modify the subgrade soil conditions and reduce the potential for post-construction heave. The most cost effective approaches (using non-expansive fill and lime stabilization of expansive soils) are discussed in the following subsection. These approaches have been used successfully in the project area. If there are questions regarding other potential subgrade improvement alternatives, risks, and life cycle costs, our firm can be consulted to provide additional recommendations. 5.6.2 Subgrade Preparation Based on the anticipated/assumed project details, we recommend the upper clay soils that are most susceptible to expansion be either replaced with non-expansive import soil or stabilized with lime (lime treated). These methods tend to provide some resistance to up-lift forces by increasing the dead load imposed on the underlying clay and often produce a relatively uniform heave pattern with minimal differential movement if the underlying clay were to swell. We have also found that for warehouses where significant concrete slab loads are anticipated, slab-on-grade perform better when low to non-expansive soils are stabilized with cement. These alternatives are discussed below. 5.6.2.1 Non-Expansive Fill This alternative involves the removal of the clay materials directly below the floor slab and replacement with non-expansive import fill. This procedure consists of placing at least 12 inches of non-expansive fill directly below the proposed floor slab system. The non-expansive fill should be moisture conditioned to a moisture content ranging from 1 to 4 percentage points above its optimum moisture content and compacted to at least 90 percent relative compaction. Specific requirements for import fill are presented in Section 5.2.5.2. The non-expansive soil pad can be prepared by removing and replacing the fill or native clay after rough grading, or placing non- expansive fill within the building pad area during rough grading. A capillary break or other slab support system placed directly below the floor slab should not replace, in whole or part, the non- expansive fill layer. The zone of non-expansive soil should extend laterally at least 5 feet outside 20210067.001A/ST020R111447 Page 20 of 37 May 11, 2020 ©2020 Kleinfelder www.kleinfelder.com