2011-08-29_REVISION - M1986015 (11)

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Parameter Method Reference Sieve Analysis ASTM C 136/AASHTO T27 -#200 wash ASTM D1140, C117, T11 Atterberg Limits ASTM D4318, T89/T90 Unconfined Compressive Strength ASTM D2166 • • Transit Mix May 18, 2011 Page 2 of 2 SUBSURFACE CONDITIONS AND LABORATORY TESTING Lyman Henn conducted a subsurface evaluation on April 28, 2011, which included the drilling, sampling, and logging of two exploratory borings. Borings LH -1 and LH -2 were extended to depths of 46 and 41 feet below the ground surface (bgs), respectively. Earth materials encountered during the subsurface exploration consisted of fine alluvium, coarse alluvium residuum and bedrock (Pierre Shale). The locations of the borings are presented on Figure 2. Generalized descriptions of the materials encountered are presented below. Detailed descriptions are presented on the boring logs in Appendix A. A Test Boring Key is also supplied in Appendix A for an explanation of soil and rock descriptions. To aid in classifying the soils and to determine general soil and bedrock characteristics, selected laboratory tests were performed on representative samples; test method references are shown in the following table. Table 1: Laboratory Test Methods The test boring reports were amended as necessary to reflect laboratory test data. The results of the laboratory testing are summarized in Table 1 and laboratory test reports are provided in Appendix B. Laboratory testing was performed by Lyman Henn. Fine Alluvium (CL, CL-ML) Fine alluvium consisting of sandy lean clay and silty clay was encountered in borings LH -1 and LH -2. The stratum was encountered from the ground surface to as deep as 10 feet bgs. This material was dry to moist and, based on Modified California test values, stiff, with blow counts ranging from 11 to 14 blows per foot (bpf). Silty clay soil was tested for unconfined compressive strength in boring LH -1. The unconfined compressive strength result was 2,290 pounds per square foot (psf). The laboratory results are provided in Table I and Appendix B. Coarse Alluvium (SP, SW) Coarse alluvium consisting of poorly- graded sand, well - graded sand, and well - graded sand with gravel was encountered in both borings below the fine alluvium. The coarse alluvium was encountered at 10 feet and extended to depths of approximately 35.4 feet and 38.1 feet bgs. This stratum ranged from approximately 25.5 feet to 28 feet in thickness. The material was slightly moist to wet and very loose to very dense, with standard penetration test values ranging from 4 to 68 bpf. Bedrock and Residuum Residuum (bedrock that is completely weathered to soil but still retaining the structure of the rock), encountered in boring LH -2, was composed of dark gray to black, highly plastic, blocky, clayey shale. The top of this stratum