CORRESPONDENCE_1990-1993 - Laserfiche WebLink

Home Browse Search

D Before performing work in the field, environmental staff review the scope of work, prepare a health and safety plan, coordinate the work to be done with their supervisor, assemble the necessary sample containers, and check, calibrate and clean equipment to be used in the field. When underground utilities may exist at a site where subsurface soil samples are being collected, USA Underground is contacted with the boring locations and the scheduled date of drilling, or a utility locating firm is employed to check the boring locations. A-2 SUBSURFACE SOIL SAMPLING A-2.1 Drilling Subsurface soil samples are collected from soil borings. Soil borings are advanced using a truck -mounted drill rig, equipped with 10 -inch hollow stem augers. The borings can be advanced vertically, or at an angle up to 45 degrees from vertical. During drilling, an experienced environmental geologist classifies the soil, logs the lithology and collects soil samples for laboratory analysis.. A-2.2 Decontamination of Equipment To reduce the potential for cross -contamination, augers and associated equipment are steam cleaned prior to drilling each boring. In addition, sampling equipment is cleaned with a trisodium phosphate wash and rinsed with distilled water prior to collecting each soil sample. A-2.3 Collection of Soil Samples Soil samples are collected approximately every 5 feet for field screening, lithologic logging, and potential chemical analysis. Samples are collected by advancing the boring to a point immediately above the desired sampling depth and then driving (vertical borings) or pushing (slant borings) a Modified California Sampler, lined with three brass tubes, into the undisturbed soil. The sampler is then removed from the bottom of the boring. The ends of the bottom (third) tube are covered with Teflon and sealed with tight -fitting plastic caps. After the samples are collected they are individually labelled. The label includes Kleinfelder's name, job number, the date and time the sample was collected, the employee number of the individual who performed the sampling, and a unique five -digit sample identification number. A custody seal is also placed on the sample in such a way that any attempt to tamper with the sample is easily visible. A-2.4 Qualitative Field Screening An organic vapor detector, such as a Photovac TIP, using a photoionization detector (PID) or a Foxboro flame ionization detector (FID), is used to provide a qualitative screening of each soil sample collected from the borings. The organic vapor detector measures ionizable compounds in the air in parts per million by volume (ppmv). Field calibration is performed using a calibrated span gas. Ambient air is used to set the instrument zero. A FWR-92-04 Page A-1 Copyright 1992 Kleinfelder, Inc.