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II. SUBSURFACE INVESTIGATIONS 2.01 Previous Investigation A preliminary slurry wall feasibility study was performed in the project vicinity in 1999 (Rocky Mountain Consultants, 1999). The feasibility study included the subject site as well as a larger area that was being evaluated at the time. The following explorations were located on the subject property, and were considered when evaluating subsurface conditions across the property: TH-3, TH-6, and TH-7. These borings are shown on Figure 2, and are included in Appendix B. A summary of these borings is included in Table I. The borings were advanced to bedrock, but no specific details regarding the method of drilling or sampling were provided. 2.02 $aley & Aldrich Exploration Program Haley & Aldrich conducted a field exploration program in June, July, October and December 2001. The program consisted of hand augered holes along the reclaimed fill slopes, and test boring drilling through soil, rock coring, and in situ water pressure testing (packer test) along the proposed slurry wall alignment. Observations of subsurface conditions at the 35~' Avenue gravel mine directly west of the site and a gravel pit. A. Supplemental Test Borings Thirty-two test borings (HA-1 to HA-32) were drilled at approximately 200-300 fr spacing along the proposed slurry wall alignment in June, July and October 2001 as part of the feasibility study. The purposes of the borings were to investigate general subsurface conditions and to obtain samples to aid in the determination of engineering properties of the in situ materials. Borings were drilled by Dakota Drilling, Inc. from Denver, Colorado and logged by a Haley & Aldrich representative. A summary of test boring results is included in Table I. Boring locations are shown on Figure 2. The individual test boring reports are provided in Appendix A. Borings were extended to depths ranging from 40.5 ft to 84 ft below ground surface (bgs). Hollow stem auger (HSA) drilling was performed to bedrock depth in all holes. Once bedrock was encountered, HSA penetration was continued for up to 15 ft in order to obtain samples of the bedrock. To assess the quality of the bedrock and provide a zone for water pressure testing, 14 of the borings were continued for an additional 10 to 20 ft using core drilling (NX diameter}. A 10-ft double-tubed core barrel assembly was typically advanced in 10-ft intervals. Standard split-spoon barrel (1-3/8 inch (in.) ID, 2 in. OD) samples were obtained from all borings in general accordance with the standard penetration test procedures specified in ASTM D 1586, generally at 5-ft intervals. The penetration values reported in the boring logs are the number of blows of a 140-Ib ltarnmer falling 30 in., generally counted over 18 in. of sampler penetration.