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KLE/NFELOER �Bright People.Right Solutions. there will be a delay between placing the aggregate base and asphalt concrete, the aggregate base should also be periodically sprinkled or wetted to prevent drying of the underlying subgrade soil. A representative from our firm should perform a field check of the soil moisture content and relative compaction prior to placement of aggregate base. 5.8.1.2 Lime Treated Subgrade In lieu of supporting pavement directly on expansive clay, the subgrade soil can be stabilized by mixing it with lime (lime treatment). For areas where pavement subgrades will be lime treated, we recommend the upper 12 to 18 inches of the subgrade below pavements be treated with 4 percent high calcium quick lime by dry weight (assumed as 115 pcf). Lime treatment is commonly used to stabilize near surface expansive soils under pavements for many of the large commercial developments in the project area. The treatment area should extend beyond the proposed improvements a horizontal distance of at least 2 feet. Final lime percentage should be determined during construction in consultation with Kleinfelder. The lime quality and spreading, mixing, and compacting operations should conform to Section 24 of the Caltrans Standard Specifications, latest edition. Following lime treatment, the treated soil should be properly cured by continual sprinkling with water to keep the surface damp, combined with light rolling to keep the surface knitted together. The subgrade soils should be covered with Class 2 aggregate base within three days of lime treatment in an effort to reduce drying. Periodic sprinkling is still required to keep the surface damp and the treated soil should not be allowed to dry out. As an alternative, the treated soil could be cured as discussed in Section 24 of the Caltrans Standard Specifications. The upper 12 inches of lime-treated subgrade soil should be compacted to at least 95 percent relative compaction. Lime treated subgrade soil below a minimum depth of 12 inches should be compacted to at least 90 percent relative compaction. The lime treatment should be designed to meet a minimum unconfined compressive strength of 200 pounds per square inch at 28-day cure based on the California Test 373. The zone of lime-treated soil should extend laterally at least 2 feet beyond the perimeter of the pavements. Prior to earthwork operations, our firm should review the lime contractor's proposed treatment procedures. Laboratory tests should be performed at least two weeks prior to earthwork operation in order to assess or revise the required lime application rate. 20210067.001A/ST020R111447 Page 26 of 37 May 11, 2020 ©2020 Kleinfelder www.kleinfelder.com