Agenda - Council - 08/28/1984 - Laserfiche WebLink

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I I I I I I I- I I I i I I I I I I I AUG 0 9 19 4 ~ -,r Reviewer Ms. Jean Beaubien 15855 Traprock Stneet R~msey, Minnesota 55303 Dear Ms. Beaubien: Enclosed are the results from the June 13, 1984 s.~mpling of your well by repre- sentatives 'of the Minnesota Pollution Control Agency (MPCA). The-samples were analyzed at the laboratory of the Minnesota Depar~nent of Health (MDH). Results from MDH indicate that no organic compounds are present at detectable concentrations in your water supply. HDH did report trace concentrations of methylene'chl, oride in the sample from your well. This de~ection of methylene chloride, however, is not attributaDle to the presence of'methylene chloride in your well water. Rather, the evidence indicates that this co~.pound was inadver- tently introduced in the la~oratory during sample bottle preparation. Methylene 'chl$~fde is an organic solvent which is used in nearly every, laboratory which carries out the kind of analyses done on your water s~ple. The most comon usage is in extracting compounds from v~rious types of s~mples. As a result, low levels of methylene chloride are often present as background contm~ination in laboratories. This is such a universally c~mmon proble~ that it is standard procedure to prepare and carry a "field blan~" during sampling work, which was done as part of this sampling effort. This field blank is a sample bottle which is cleaned and prepared in exactly the same way as the other sm~ple bottles. It is then filled with organic-free water in the laboratory, and carried during the sampling. If there is a problem with background contamination by methylene chloride, or any other compound, it will be indicated by the presence of that compound in the field blanK. The enclosed data sheet for the field blank shows that methylene chloride was present in trace concentrations, which indicates that the methylene chloride noted in the private well samples was introduced into the sample as a result of background laboratory contamination, and is not present in the well water. This type of problem was not unique to the s~mple taken from your well; the s~ne thing happened with all of the other seven resi- dential well samples which were collected during our s~mpling work that day. No contmnination by any other organic compounds was noted in any of the other resi- dential wells samples, which further reinforces the conclusion of laboratory introduction of the methylene chloride.