Laserfiche WebLink
has been substantially removed from the well . <br /> Before collecting a water sample, a well should be <br /> purged until temperature, conductivity and pH <br /> stabilize. often, this will require removal of <br /> four or more well volumes by bailing or pumping. <br /> once well volumes are removed and well water is <br /> stabilized, a sample can be taken after the water <br /> level approaches 80 percent of its initial level . <br /> ' Where water level recovery is slow, the sample can <br /> be collected after stabilization is achieved <br /> Ground water samples should be collected in a <br />' manner which reduces or eliminates the possibility <br /> of loss of volatile constituents from the sample. <br /> For collecting samples, a gas-actuated positive <br />' displacement pump or a submersible pump is <br /> preferred. A Teflon or stainless steel bailer is <br /> acceptable. Peristaltic pumps or airlift pumps <br /> should not be used. <br /> Cross-contamination from transferring pumps (or <br /> bailers) from well to well can occur and should be <br />' avoided by thorough cleaning between sampling <br /> episodes. Dedicated (i.e. . permanent <br /> installation) well pumps, while expensive, are <br /> often cost effective in the long term and ensure <br /> data reliability relative to cross-contamination. <br /> 10 If transfer of equipment is necessary, sampling <br /> should proceed from the least contaminated to the <br /> most contaminated well , if the latter information <br /> is available before sample collection. <br /> Water samples should be collected in vials or <br />' containers specifically designed to prevent loss <br /> of volatile constituents from the sample. These <br /> vials should be provided by an analytical <br />' laboratory, and preferably, the laboratory <br /> conducting the analysis. No headspace should be <br /> present in the sample container once the container <br /> has been capped. This can be checked by inverting <br />' the bottle, once the sample is collected, and <br /> looking for bubbles. Sometimes it is not possible <br /> to collect a sample without air bubbles, particu- <br />' larly if water is aerated In these cases , the <br /> investigator should record the problem and account <br /> for probable error. Cooling samples may also <br /> produce headspace (bubbles) , but these will <br /> disappear once the sample is warmed for analysis. <br /> Samples should be placed in an ice chest <br /> maintained at 4 "C with blue ice (care should be <br /> taken to prevent freezing of the water and <br /> A14 <br />