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Phelan Development Holly Master Plan - Buildings H & 1 15188.000.006 Geotechnical Exploration satisfactory, and that placement and compaction of the fills have been performed in accordance with our recommendations and the project specifications. Sufficient notification to us prior to earthwork is important. If we are not retained to perform the services described above, then we are not responsible for any party's interpretation of our report. 5.0 EARTHWORK RECOMMENDATIONS As used in this report, relative compaction refers to the in-place dry unit weight of soil expressed as a percentage of the maximum dry unit weight of the same soil, as determined by the ASTM D1557 laboratory compaction test procedure, latest edition. Compacted soil is not acceptable if it is unstable; it should exhibit only minimal flexing or pumping, as observed by an ENGEO representative. The term "moisture condition" refers to adjusting the moisture content of the soil by either drying if too wet or adding water if too dry. We define "structural areas" as any area sensitive to settlement of compacted soil. These areas include, but are not limited to building pads, sidewalks, pavement areas, and retaining walls. 5.1 EXISTING FILL REMOVAL Undocumented fill was encountered in our explorations in the eastern portion of the site in the vicinity of Building I, specifically in the areas with historic basins onsite. Additionally, existing buildings with buried foundation systems as well as slabs and footing systems from previous structures are present in the western portion of the site. We recommend complete removal of undocumented fill and any existing buried structures to competent native soil and replace with engineered fill, as evaluated by ENGEO. Figure 4 displays the approximate lateral extent of existing fill associated with the previous basin, as well as buried features known to us at this time. The lateral extent and depth of fill are expected to vary. Consult the exploration logs in Appendix B for fill depths at specific locations. Additional potholing of the site prior to grading operations may aid preliminary estimates of fill volumes provided in this report. ENGEO should be present during the subexcavation of the non-engineered fill to confirm the depth and lateral extent of removal. The non-engineered fill may be placed back as an engineered fill provided it meets the recommendations in Section 5.5 below. As an alternative to removal and overexcavation, ground improvement may be performed. We provide recommendations for ground improvement in Section 6.1. 5.2 EXPANSIVE SOIL MITIGATION To reduce the risk of structural damage associated with the variably expansive soil conditions, we recommend lime treating the upper 18 inches of the finished building pad and to 5 feet laterally beyond building extents. We provide recommendations for lime treating slab subgrade in Section 7.1.1. 5.3 GENERAL SITE CLEARING Areas to be developed should be cleared of surface and subsurface deleterious materials, including existing building foundations, slabs, buried utility and irrigation lines, pavements, debris, ENGEOPage 113 December 13, 2021 Expect Excellence