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5 <br /> r, <br /> STANDARD PROCEDURES <br /> Evacuation <br /> Groundwater wells are thoroughly purged before sampling to insure that the sample is <br /> collected from water that has been newly drawn into the well from the surrounding geolog- <br /> ic formation The selection of equipment to evacuate each well is based on the physical <br /> characteristics of the well and what is known about the performance of the formation in <br /> which the well has been installed There are several suitable devices which can be used for <br /> evacuation The most commonly employed devices are air or gas actuated pumps, electric <br /> submersible pumps, and hand or mechanically actuated bailers Our personnel frequently <br /> employ USGS/Middleburg positive displacement pumps or similar air actuated pumps <br /> which do not agitate the water standing in the well <br /> Normal evacuation removes three case volumes of water from the well More than three <br /> case volumes of water are removed in cases where more evacuation is needed to achieve <br /> stabilization of water parameters and when requested by the local implementing agency Less <br /> water may be removed in cases where the well dewaters and does not recharge to 80% of its <br /> original volume within two hours and any additional time our personnel have reason to remain <br /> at the site In such cases, our personnel return to the site within twenty four hours and collect <br /> sample material from the water which has recharged into the well case <br /> Decontamination <br /> All apparatus is brought to the site in clean and serviceable condition The equipment is <br /> decontaminated after each use and before leaving the site Effluent water from purging and <br /> on-site equipment cleaning is collected and transported to Shell's Martinez Manufacturing <br /> Complex in Martinez, California <br /> Free Product Skimmer <br /> The column headed, VOLUME OF D&41SCIBLES REMOVED (m1) is included in the <br /> TABLE OF WELL GAUGING DATA to cover situations where a free product skimming <br /> device must be removed from the well prior to gauging Skimmers are installed in wells <br /> with a free product zone on the surface of the water The skimmer is a free product recov- <br /> ery device which often prevents normal well gauging and free product zone measurements <br /> The 2 0" and 3 0" PetroTraps fall into the category of devices that obstruct normal gaug- <br /> ing In cases where the consultant elects to have our personnel pull the skimmers out of <br /> the well and gauge the well, our personnel perform the additional task of draining the <br /> accumulated free product out of the PetroTrap before putting it back in the well This <br /> Blaine Tech Samoes,Inc.940213-,-1 Shell 3725 S Tracy Blvd,Tracy page 2 <br />