ARCHIVED REPORTS_XR0011953 - Laserfiche WebLink

Home Browse Search

i Additional Groundwater Investigation Report CSUS Multi-Campus Regional Center August 19,2003 Page 4 3.1 SITE PREPARATION �I A drilling permit application was prepared by Condor and submitted to the SJCEHD for five proposed CPT borings and five proposed direct push borings. Condor received the drilling permit prior to initiating { any fieldwork. The proposed soil boring locations were marked with white paint and Underground Service Alert(USA) was notified 72 hours in advance of the fieldwork to locate and identify underground utilities in and near the work area. However, because the proposed boring locations were on private property, some utilities contacted by USA did not mark their lines past property boundaries and on to the site. Therefore, it was the responsibility of the property owner to locate and identify underground utilities in and near the work area. The SJCEHD was notified of the fieldwork schedule 72 hours in advance. I. 3.2 CPT PROCEDURES A Condor geologist was on site to supervise the work. Prior to commencement of fieldwork, a tailgate safety meeting was held and a site-specific Health and Safety Plan was discussed with, and presented to, all field personnel for their signatures. The investigation.included the advancement of five CPT borings pairs (CPT-4 through CPT-8) between April 14 and 17, 2003 using an integrated electronic system in accordance; with ASTM standards (D 5778-95). The borings were advanced to evaluate the vertical extent of groundwater contamination in the vicinity of the former USTs and at the anticipated cross and down-gradient extents of the plume. Borings CPT-4, CPT-5, and CPT-6 were advanced to depths of approximately 100 feet below ground surface (bgs); borings CPT-7 and CPT-8 were advanced to depths of approximately 130 feet and 135 feet bgs, respectively. The boring locations are shown in Figure 2,Attachment A. At each boring pair location, the first boring of each group was used to investigate the lithology of the site at that location. The first borings of each boring pair were completed on April 14, 2003. Pilot holes were hand-augured to five feet bgs. The borings were hydraulically advanced downward into the subsurface using an electric piezocone tip. Measurements of cone resistance, sleeve friction, and dynamic pore water pressure were measured at approximately five-centimeter (cm) depth intervals to provide a nearly continuous hydrogeologic log of the subsurface. Pore pressure dissipations were recorded at five-second intervals when appropriate during pauses in the penetration. The five geologic logs were compared and ` correlated to identify potential horizons that are laterally extensive and relatively conductive of groundwater(clean sand) and/or potential horizons that may act as relative groundwater barriers (clay and silt). Copies of the CPT boring logs are included in Attachment B. One directp ush boring was advanced within a few feet of each CPT borehole to collect discrete € groundwater grab samples from horizons identified in the CPT boring logs. The second boring at each pair location and a single direct push boring were completed from April 15 through 175 2003. Pilot holes were hand-augured to five feet bgs.-The direct push borings, corresponding to CPT-.4, CPT-5, CPT-6, CPT-7, and CPT-8, were hydraulically advanced using a 2-inch diameter conicalbit to depths of approximately 85 feet, 82 feet, 100 feet, 127 feet, and 128 feet bgs, respectively. Based on field observations of the shallow groundwater sample collected from CPT-5, an additional direct push boring, GP-10, was advanced to a depth of approximately 44 feet bgs to investigate the potential lateral extent of petroleum hydrocarbon contamination in shallow groundwater downgradient of CPT-5. Groundwater samples were collected using a push-type groundwater sampler. The piezoeorie, groundwater sampler, stainless steel bailer, and associated push rods were thoroughly steam-cleaned prior to each depth advancement and sample collection. Upon completion of the boring and sampling, each boring was grouted to the surface with neat cement. The cement was tremied into the boreholes to avoid bridging. A grout-collar was utilized to backfill all the CPT boreholes with the GON©OR r