ARCHIVED REPORTS XR0008679 - Laserfiche WebLink

Home Browse Search

i S !EC0R ATTACHMENT D FIELD AND LABORATORY PROCEDURES Exploratory Drilling The soil borings will be drilled using air rotary with casing hammer drilling equipment to depths of approximately 120 feet bgs Borings will be logged by a SECOR International Incorporated scientist under the direction of a registered geologist using the Unified Soil Classification System and standard geologic techniques Soil samples will be collected every 10 feet at depth from 80 to 120 feet using a split-spoon sampler Soil samples for chemical analysis will be retained in brass liners, capped with Teflon squares and plastic end caps, and sealed in clean zip-lock bags The samples will be placed on ice for transport to the laboratory accompanied by chain-of-custody documentation Down-hole drilling and sampling equipment will be steam-cleaned following the completion of the soil boring Down-hole sampling equipment will be washed in a tri-sodium phosphate or alconox solution between samples Well Installation and Development N The soil borings will be converted to groundwater monitoring wells by installing 4-inch diameter, flush- threaded, Schedule 40 PVC casing with 0 020-inch factory-slotted screen Heavy wall casing will be utilized as conductor casing and will be advanced following the drill bit to the total depth explored in each boring in order to seal the upper groundwater bearing zones from the lower groundwater bearing zones Approximately 10 feet of screen will be placed in the bottoms of the boring A grade , of sand appropriate to the screen size will be placed in the annular space across the entire screened interval, and will extend approximately 2 feet above the top of the screen for the wells A bentonite seal will extend two to four feet above the sand pack The monitoring wells will be completed with neat cement from the bentonite seal to the ground surface The well casing will be topped with a locking cap The wellhead will be contained in a watertight traffic-rated well box The boring logs will show well construction details The well will be developed after completion The development procedure for each well will consist of surging the well, then pumping or bailing water from the well until the water is visibly clear, the well goes dry, or until a maximum of ten casing volumes have been removed �r The newly installed wells will be surveyed by a California State Licensed Surveyor The well casings will be surveyed to the nearest 0 01 feet in elevation to a known benchmark Organic Vapor Procedures �F Soil samples collected at 5-foot depth intervals during drilling will be analyzed in the field for ionizable organic compounds using a photo-ionization detector (PID) with a 10 2 eV lamp or a flame ionization detector (FID) The test procedure will involve measuring approximately 30 grams from an undisturbed soil sample, placing this subsample in a sealed container (either a zip-lock bag or a N mason lar) The container will be warmed for approximately 20 minutes (in the sun), then the head- space within will be tested for total organic vapor, measured in parts per million as benzene (ppm, volume/volume) The instrument will be calibrated prior to drilling using a 100-ppm isobutylene standard (in air) and a sensitivity factor of 55, which relates the photo-ionization potential of benzene fi to that of isobutylene at 100 ppm The results of the field testing will be noted on the boring logs PID and FID readings are useful for indicating relative levels of contamination, but cannot be used to evaluate hydrocarbon levels with the confidence of laboratory analyses