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10 well volumes or until the conductivity,pH,and temperature of the <br /> groundwater being extracted have stabilized. These parameters will be <br /> judged to have stabilized when three consecutive readings show: <br /> • Less than 10 percent change in conductivity; <br /> • Less than 10 percent unit change in pH; and <br /> • Less than 10 percent change in temperature. <br /> Each well will be considered developed when the parameters have <br /> stabilized and the water flows clear, or when 10 well volumes have been <br /> removed (whichever occurs first). Development water from all <br /> monitoring wells will be containerized until properly disposed. <br /> The static water levels in the wells will be measured a minimum of <br /> 24 hours after installation and initial development to help determine the <br /> hydraulic gradient at the Site. <br /> 4.5 GROUNDWATER SAMPLING PROCEDURES <br /> Groundwater samples will be collected a minimum of 24 hours following <br /> monitoring well development,and quarterly thereafter,for a period of <br /> 1 year. A low-flow method will be used-to collect groundwater samples. <br /> The primary pu se of low flow (micropu 'ng) sampling is to minimize <br /> disturbance in the o minimize the collection of <br /> normally immobile particles in the sample,which will affect the level of <br /> potential contaminant concentrations. The method also reduces the <br /> volume of water that will need to be disposed of. <br /> The depth to groundwater and the total depth of the well will be <br /> measured in each monitoring well. Water levels will be measured with <br /> minimal disturbance in the casing. Water will be pumped from the <br /> middle of the screened interval at a low rate to minimize drawdown and <br /> disturbance of the water-bearing zone. Groundwater parameters (pH, <br /> temperature,and conductivity)will be monitored every 3 to 5 minutes <br /> until parameter stabilization is reached. The water level will be checked <br /> periodically to minimize drawdown. Samples will be collected through <br /> the flow tubing after parameter stabilization and the water level will be <br /> recorded after sample collection. <br /> The groundwater samples will be collected in clean, appropriately <br /> preserved,laboratory-supplied containers. The samples will be labeled <br /> and stored in a cooled ice chest until delivery to a California-certified <br /> analytical laboratory. A chain-of-custody document will be completed for <br /> the collected samples and will accompany the samples to the laboratory. <br /> ERM 10 LMOO,WC./0067MO1-N.. 2107 <br />