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samples are removed. Upon removal from the sampler, the ends of the lowermost tube are typically sealed with Teflon® sheeting and plastic caps. The sample may be extruded from the tube and sealed within another appropriately cleaned sample container(e.g., glass jar). The sealed simple is labeled and handled according to the Quality Assurance Plan. Material from one of the other tubes is screened in the field, when rec uired, according to the Soil Sample Screening section below. The data is recorded on the boring logs at the depth corresponding to the sampling point. All drilling and sampling equipment are either steam-cleaned,or wast ed with a solution of Alconox(or equivalent) soap and water and triple rinsed between bore holes and samples to minimize the potential for cross-contamination. Soil Classification As the samples are obtained in the field,the field geologist classifies them in accordance with the Unified Soil Classification System, Visual/Manual Method. Representative portions of the samples are then retained for further examination and verification of the field classification. Logs of the borings are prepared indicating the depth and identification of the various strata,the N value and pertinent information regarding the method of maintaining and advancing the borehole. Soil Sample Screening After the soil samples in re-sealable (Ziploc® type) plastic bags have been brought to ambient temperature, the headspace vapors in the bag are screened with a photo-ionization detector equ Aped with a 10.2 eV lamp. The corner of the bag is opened and the detector probe immediately placed within the headspa e. The highest observed reading is recorded. Monitoring Well Construction The borehole diameter for a monitoring well is a minimum of four ir ches larger than the outside diameter of the casing. A monitoring well is typically cased with threaded, factory-perforated and blank Schedule 40 PVC. The perforated interval consists of slotted casing,generally with 0.01 or 0.02 inch-wide by L -inch-long slots, with 42 slots per foot. A threaded or slip PVC cap is secured to the bottom'of the casing. The slip cap cap be secured with stainless steel screws or friction. No solvents or cements are used. Centering devices may be fastened to the casing to ensure even distribution of filter material and grout within the borehole annulus. The well casing is thoroughly washed and/or steam cleaned. It may be purchased as pre-cleaned prior to completion. 1� �5