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GeofogkafTechnics Inc. Page 3 Valentine(.Eldorado St.) Work Plan Addendum Project No.723.2 January 13, 1999 Well No. Dia./TD Screen Slot Sand Pack Trans.' Seal Grout Seal MW-101 111190' 85-90' 0.010" #12 sand 83-91' 78-83' 78-surface MW-201 1"/105' 105-110' 1 0.010" 412 sand 103-111' 91-103' After.the well sealing materials have set (>24 hours) the wells will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The wells will be purged and groundwater samples collected no sooner than 48 hours after well ' development. All development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged. The top of casing measuring point for the well will be surveyed into the common arbitrary plane of the existing monitoring wells by a competent surveyor. Groundwater Sampling Procedure_ The groundwater in the new wells will be sampled no'sooner than 48 hours after well development and from there after on a quarterly basis.. The following is a procedure for the sampling of groundwater from the well: Before sampling is attempted the wells will be sounded for depth to water and then a clear disposable bailer will be used to determine if floating product is present. The wells will be ` purged of at least 3 well volumes of stagnant water using a Wattera purging system. ,The Wattera system uses a length of poly tubing.with a check-ball on the bottom. The tubing is agitated in an up and down movement which causes the water to rise in the tubing. This system has'been found to be very time and cost effective at sites that have problems with silting of the wells. Purging will continue until the temperature, conductivity, and pH of the groundwater has stabilized (<10% variation between three readings) indicating that formation water representative of aquifer conditions is entering the well. These water quality parameters are measured at intervals of each well volume purged. A stainless steel or disposable plastic bailer will be used to collect each sample. Care will be taken to minimize sample agitation from the initial filling of the bailer to the transfer of the sample to the VOA vial and glass amber liter bottles. Once the sample containeris filled and capped, the bottle will be inverted, tapped, and checked for head space bubbles. The sample container is identified and labeled with a unique designation, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory. All non disposable sampling equipment is decontaminated using'a steam cleaner before.and between uses. The effectiveness of the decontamination procedure is ensured by using the following quality control measures: } • Disposable gloveswill be used by the technician to collect .all samples and Will be � changed with each sampling'everit. • A .bailer blank for each well will be collected prior to sampling by filling the decontaminated stainless steel bailer with water (provided by the laboratory) and then filling a VOA vial (provided by the laboratory) using the same procedures for actual sample collection.