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KLE/NFELOER \\ J/Bright People.RIghY So7etFons. V If construction is to proceed during the winter and spring months, one way to reduce the exposure of the pad and potential repairs is to leave the subgrade at least 1 foot above the proposed subgrade elevation, cutting it down immediately before placing the capillary break and floor slabs. The cut areas should be proof-rolled at the discretion of the Geotechnical Engineer to identify whether undercutting of any remaining wet/unstable soils is required. Cut soils can be placed in landscape areas or disced and aerated (dried) during dry weather for placement in pavement, future pad, or other areas. 5.2.9 Trench Backfill All trench backfill should be placed and compacted in accordance with recommendations provided for engineered fill (see Section 5.2.5). Mechanical compaction is recommended. It should be noted that the native clayey material may require significant effort to achieve compaction within narrow trenches. If granular import is used for backfill, a native clay soil or lean concrete slurry dike should be provided in the upper 4 feet and extending 4 feet laterally where the trenches cross beneath the perimeters of the structures. This dike is intended to minimize the lateral migration of subsurface water into clay soil under the building. In addition, the native sandy clay soil or clay fill soils should be placed within the upper 2 feet of trenches exposed to the ground surface. 5.2.10 Pipe Bedding and Pipe Zone Backfill Placement Pipe bedding and pipe zone backfill materials for pipelines should meet manufacturer's recommendations for material type, gradation and thickness. If used, clean crushed rock bedding and initial backfill materials should be overlain by a non-woven filter fabric (see Section 5.2.11, Filter Fabric Envelope) to prevent migration of fines into the voids in the material. Bedding materials should be compacted to a firm and unyielding condition prior to placement of pipes. Initial backfill materials placed around the pipe zone should be placed in a manner to eliminate voids beneath the pipe. Clean crushed rock should be suitable for this use. If used, clean crushed rock materials should be placed in lifts less than 1 foot in loose thickness and be compacted using vibratory plate equipment until it is firm and unyielding. It is recommended that placement of the bedding and pipe zone backfill material be observed by a representative of the geotechnical engineer during construction to verify proper placement and compaction. 20210067.001A/ST020R111447 Page 15 of 37 May 11, 2020 ©2020 Kleinfelder www.kleinfelder.com