WORK PLANS - Laserfiche WebLink

Home Browse Search

B-12 and B-13 will be located by the underground septic tanks. The locations of the 13 borings are presented on Figure 2. The geoprobe sampling process is an integrated boring advancement and sample collection method that involves the driving into the subsurface four-foot sections of pipe lined with a new poly soil collection tubing. The entire sampling assembly is driven into the subsurface by a percussion- vibratory hammer operated through either a hydraulic or a pneumatic system. Below four feet,4-foot sections of geoprobe steel rods are connected to the sampling assemblage allowing deeper soil samples to be collected. The sampling pipe is blocked at the bottom end with a locking driving tip until the desired sampling depth is reached. At the desired sampling depth, the sampling pipe is opened by running thin rods to unlock the driving tip and turning open the sampling pipe. A soil sample is collected by driving the assembly for another four feet. All of the sample liners are protected from cross contamination by the outer sampling pipe. By adding sections of the geoprobe steel rods, and repeating the driving process,continuous soil cores are generated from the desired depths. At each sampling interval, a decontaminated sampling pipe and new poly sample liners will be used to avoid cross contamination. After each sampling drive, the sampling pipe will be retrieved and the poly sample liners removed and inspected. At approximately 2-foot intervals or at changes in lithologies or other discernable changes, a portion of the soils in the poly liner will be removed and classified according to the Uniform Soil Classification System and recorded on the soil boring logs. Select soil sample will also be field screened by an organic vapor meter(OVM)equipped with a photo-ionization detector(PID). The readings of the OVM will also be recorded on the boring logs. Based on the physical inspection and OVM screening, one or more 4 to 6-inch sections of the poly tubing, which appear to be the most heavily impacted, will be selected for laboratory analyses or archiving. Each poly section selected for laboratory analyses or archiving will be sealed with teflon sheets and plastic end caps. The sealed sample liner will then be labeled, sealed in a plastic bag, and placed in an ice chest cooled to 4°C with crushed ice for temporary field storage. The chain-of- custody protocol will be maintained for all soil samples from the time of collection to arrival at the laboratory. For further details in Quality Assurance and Quality Control protocols,please see the following section of this workplan. Prior to soil sampling activities, A drilling permit will be obtained from the SJCEHD. The SJCEHD will also be notified of the drilling date to allow for agency inspection, as necessary. The geoprobe work drilling will be performed by ECA of Aptos, California or by another qualified environmental drilling contractor with a current C-57 license. During the drilling operations, a field geologist or engineer from AllWest will be present to maintain a boring log and to supervise the drilling activities. The boring log will contain all pertinent information on drilling and soil conditions. The boring log will be included in the final written report. A copy of the field boring log to be used, the boring log legend, and the Unified Soil Classification System(USCS)is included in Appendix A. 4