ARCHIVED REPORTS_XR0011601 - Laserfiche WebLink

Home Browse Search

,, . Soil Borings Working To Restore Nature Before drilling, RESNA Industries notified Underground Service Alert of our intent to drill so that approximate locations of underground utility lines and structures could be marked. We hand- augered each boring to a depth of approximately 5 feet below grade to attempt to locate underground structures. The borings were drilled with a truck-mounted drill rig equipped with 8- inch-diameter. The drillers steam-cleaned the augers before drilling each boring to minimize the possibility of cross-contamination. F Soil ampling in Borings Soil samples were collected at 5-foot intervals from the ground surface to the total depth of the borings. The soil samples were collected by advancing the boring to a point immediately above the sampling depth, and then driving a California-modified, split-spoon sampler containing brass sleeves through the hollow stem of the auger into the relatively undisturbed soil. The sampler and brass sleeves were steam-cleaned or washed thoroughly with a laboratory-grade, non-phosphatic r detergent and water before each use. The sampler was driven 18 inches with a standard 140- F=` pound hammer repeatedly dropped 30 inches. The number of blows required to drive the sampler each successive 6 inches was counted and recorded to evaluate the relative consistency of the soil. f� During drilling, the geologist used a field photoionization detector(PID)to characterize the relative levels of hydrocarbons. Field instruments such as the PID are useful for indicating relative levels Of hydrocarbon vapors but do not detect the concentration of hydrocarbons present with the same precision as laboratory.analyses. One of the samples in brass sleeves not selected for laboratory analysis at each sampling interval was tested in the field using a PID. This testing was performed by placing the intake probe of the PID against the soil after opening the brass container. The soil samples selected for possible laboratory analysis were removed from the sampler and quickly sealed in their brass sleeves with aluminum foil, plastic caps, and aluminized duct tape. The respective sample containers were labeled in the field with the job number,sample location and depth, and date and promptly laced in iced storage for transport to the laboratory. Chain of Custody Records were initiated in the field by the geologist and accompanied the mples to a l laboratory certified by the State of California to perform the analyses requested. Logging of Borings Soil cuttings and samples were identified using visual and manual methods, and classified according to the Unified Soil Classification System. Samples not selected for chemical analysis and the soil in the sampler shoe were extruded in the field and examined using visual and manual methods. Logs include records of texture, color, moisture, plasticity, consistency, blow counts, and any other characteristics noted along with evidence for the presence of hydrocarbons such as soil staining, obvious product odor, and PID readings. The borings were backfilled with a ' cement-bentonite slurry to ground surface. -r Monitoring-Well Construction f1 Monitoring wells were constructed in the borings with thread jointed, 4-inch-inner-diameter, Schedule 40 polyvinyl chloride casing. No chemical cements,glues, or solvents were used in well construction. The screened portion of each well consisted of facto erforated casing with 0.020- inch-wide rY-p g inch-wide slots. The well screen extends from the total depth of the well to approximately 5 or 10 feet above the ground-water surface. The annular space in the well was packed with number 3 sand to approximately 1 to 2 feet above the slotted interval. A minimum 2-foot thick bentonite plug was added above the sand pack to prevent the cement from entering the well pack. The remaining annulus was backfilled to grade with a bentonite cement slurry.