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SOP #: GW 0001 <br />Region I Low Stress <br />(Low Flow) SOP <br />Revision Number: 2 <br />Date: July 30, 1996 <br />Page 3 of 13 <br />Teflon). <br />Adjustable rate, peristaltic pumps (suction) may be used with <br />caution. Note that EPA guidance states: "Suction pumps are not <br />recommended because they may cause degassing,. pH modification, and <br />loss of volatile compounds" (EPA/540/P-87/001, 1987, page 8.5-11). <br />The use of inertial pumps is discouraged. These devices frequently <br />cause greater disturbance during purging and sampling and are less <br />easily controlled than the pumps listed above. This can lead to <br />sampling results that are adversely affected by purging and sampling <br />operations, and a higher degree of data variability. <br />B. 'IUbing <br />Teflon or Teflon lined polyethylene tubing are preferred when <br />sampling is to include VOCs, SVOCs, pesticides, PCBs and inorganics. <br />PVC, polypropylene or polyethylene tubing may be used when collecting <br />samples for inorganics analyses. However, these materials should be <br />used with caution when sampling for organics. If these materials are <br />used, the equipment blank (which includes the tubing) data must show <br />that these materials do not add contaminants to the sample. <br />Stainless steel tubing may be used when sampling for VOCs, SVOCs, <br />pesticides, and PCBs. However, it should be used with caution when <br />sampling for metals. <br />The use of 1/4 inch or 3/8 inch (inner diameter) tubing is preferred. <br />This will help ensure the tubing remains liquid filled when operating <br />at very low pumping rates. <br />Pharmaceutical grade (Pharmed) tubing should be used for the section <br />around the rotor head of a peristaltic pump, to minimize gaseous <br />diffusion. <br />C. Water level measuring device(s), capable of measuring to 0.01 <br />foot accuracy (electronic "tape", pressure transducer). Recording <br />pressure transducers, mounted above the pump, are especially helpful <br />in tracking water levels during pumping operations, but their use <br />must include check measurements with a water level "tape" at the <br />start and end of each record. <br />D. Flow measurement supplies (e.g., graduated cylinder and stop <br />watch). <br />E. Interface probe, if needed. <br />F. Power source (generator, nitrogen tank, etc.). If a gasoline <br />generator is used, it must be located downwind and at least 30 feet <br />from the well so that the exhaust fumes do not contaminate the <br />samples. <br />