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4.2.6 DETECTION LIMITS The detection limits for the various method analyses will be established as the mini- mum concentrations that must be accurately and precisely measured by the laboratory. Consideration will be given for practical limitations such as sample size,matrix interfer- ences, and dilutions. ' 4.3 FIELD PROCEDURES 431 SOIL BORINGS AND MONITORING WELL INSTALLATION Soil borings will be drilled and sampled using 8-inch-outside diameter (OD), 3-inch- inside diameter (ID) hollow-stem augers. Soil borings will be sampled at five-foot in- =t r- tervals during boring advancement to produce lithologic logs. Drill.cuttings will be i j.., disposed as described in Section 3. Samples will be collected using a 2-inch ID split- spoon sampler lined with brass sleeves. Each sleeve will be capped with Teflon tape p? and a polyethylene cap, taped to the sleeve. Sample identification numbers will be E:e marked on the outside of the sleeve using indelible markers. i The well will be installed through 12-inch OD; 8-inch ID hollow-stens augers. If un- favorable conditions(sand locking,heaving sand,etc.)prevent or impede completion of the well using hollow-stem augers, air- or mud-rotary drilling may be used to prepare a borehole for well installation. The well casing and screen will be a 4-inch ID flush-threaded, Schedule 40, PVC. The . screen section will be factory slotted with 0.02-inch slots. The annulus around the j -I screen will be filled with No. 3 sand (Lonestar or equivalent). The.monitoring well will { be screened across the water table with a maximum screened intelval of 20 feet. The � exact interval to be screened will be determined in the field, 'based on the first appear- ance of water in the boring anal the firi water-bearing permeable zone encountered. The well installation procedures are as follows: • The proposed boring locations will be marked with stakes and cleared for s utilities. i • The drill rig,drilling equipment, and brass sleeves will be decontaminated i by steam cleaning or by detergent/water/isopropanol/de-ionized water washings before and after drilling. • The drill cuttings and split spoon samples will be logged by a CH2M HILL hydrogeologist or geologist. 3 sF031604\WP\004.51 4-4 t 1� i. .z-