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Quik Stop No 121 Closure Report <br /> CCI Project No 12118 <br /> Page 6 <br /> a gray-brown, stiff, silty clay was encountered During the collection of samples, no unusual <br /> odors were noted at any of the three well locations Organic vapor readings taken on soil <br /> samples collected from the three wells registered no detectable vapor readings <br /> Groundwater was generally encountered at a depth of approximately 14 to 15 feet at well <br /> locations MW-1 and MW-2 Groundwater at MW-3 was encountered at approximately 18 feet <br /> under confined conditions and immediately rose to approximately 15 feet Static water levels in <br /> the three wells were measured on April 30, 1999 at approximately 14 feet below the ground <br /> surface <br /> In order to further explore subsurface conditions at on and offsite locations, CCI used a cone- <br /> penetration test rig on June 21, 2000, to gather additional subsurface data The subsurface <br /> conditions encountered at CPT-1 (located on-site, near MW-3) were found to be composed of <br /> alternating layers of silty sand and sand, with some silty clay and clay from the surface to <br /> approximately 32 feet The material was found to be dense, with localized areas of very dense <br /> material From 32 feet to 42 feet, dense sand to gravelly sand was encountered This granular <br /> unit was followed by a 12-foot interval of sand, sandy silt to silty clay From 54 feet to 66 feet, <br /> very stiff, clayey silt to clay was encountered, with some localized "hard pan" material Below <br /> 66 feet and extending to the bottom of the bore hole, very dense sand to gravelly sand was <br /> encountered Refusal occurred at 79 5 feet <br /> The off-site CPT sounding hole (CPT-2), located approximately 325 feet to the southeast <br /> of the site, also encountered alternating layers of clay, silty clay, sand and gravelly sand to a <br /> depth of approximately 43 feet Below this interval and extending to a depth of 62 feet, the soil <br /> became less granular, consisting of silty sand to silty clay and clay There were several localized <br /> areas of hard pan material encountered CPT-2 was terminated at 62 feet due to refusal Copies <br /> of the CPT sounding logs are attached in Appendix A <br /> Site Hydrogeology <br /> During site investigations conducted in 1999, groundwater was generally encountered at a depth <br /> of approximately 14 to 15 feet at well locations MW-1 and MW-2 Groundwater at MW-3 was <br /> encountered at approximately 18 feet under confined conditions and immediately rose to <br /> approximately 15 feet Static water levels in the three wells were measured on April 30, 1999 at <br /> approximately 14 feet below the ground surface The groundwater gradient within the shallow <br /> aquifer at the site was nearly flat, with a very slight gradient ranging from the northeast to the <br /> southeast Additional shallow monitoring wells installed at the site in 2000 and 2001, along with <br /> groundwater level data collected during several quarters of monitoring, showed the shallow <br /> gradient at the site to be toward the north to northeast, at a nearly flat gradient In December <br /> 2000 and August 2001, CCI installed three additional deep wells to depths of 75 feet to monitor <br />