WORK PLANS - Laserfiche WebLink

Home Browse Search

. Gea(agical?a6rcics circ �+� �''/ Page 4 Additional Site Characterization Work Plan Project No.724.2 July 7,2000 L Detection Limits: BTEX MTBE TPH-G Soil(µg/Kg) 13.0 150 11,000 2.3 Groundwater Sampling Procedure The groundwater in the new well will be sampled no sooner than 48 hours after well L development and from there after on a quarterly basis. The following is a procedure for the sampling of groundwater from the well: LBefore sampling is attempted the well will be sounded for depth to water and then a clear disposable bailer will be used to determine if floating product is present. The well will be purged of at least 3 well volumes of stagnant water using either a submersible pump or a stainless steel bailer. 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. In addition to the above water quality parameters, dissolved oxygen (DO) and oxidation- reduction potential (ORP) will be measured. Oxidation-reduction potential is measured by directing the pump stream through a YSI 3560 flow-through cell during the well purging. A constant pumping rate is maintained. Dissolved oxygen is measured in one of two ways, depending on depth of water in the well. For deep water tables (depth to water greater then 20 feet) the water from the flow-through cell flows into a beaker in which a YSI dissolved oxygen meter probe has been placed. For wells in which the depth to water is less then 20 feet the pump used for well purging aerates the water so the above technique is invalid. In this case a down-hole YSI dissolved oxygen meter is used. It is placed at the screened interval of the casing so formation water flows past the probe. In both cases purging continues until the parameters stabilize. 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 L sample to the VOA vial and glass amber liter bottles. Once the sample container is filled and capped, the bottle will be inverted, tapped, and checked for headspace bubbles. The sample container is identified and labeled with a unique designation, inserted into foam holders and Lplaced 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 gloves will be used by the technician to collect all samples and will be changed with each sampling event. • 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 L