Geologic logs are prepared from examination of drill cuttings (samples). Well drillers are usually required to submit drill cuttings to WGNHS for wells which are: (1) high capacity (>70 gallons per minute), such as irrigation or industrial wells, OR (2) public water supply wells, such as those for municipalities, schools, parks, or waysides.
Unfortunately, there are many wells for which WGNHS should have samples, but doesn’t. Reasons include: (1) samples not collected by well drillers, (2) samples collected but not submitted to the Survey, (3) samples sufficiently damaged after collection so as to render them useless (4) samples collected but not labeled, therefore also useless, (5) very difficult or unusual drilling conditions, which make sample collection difficult and/or samples collected meaningless.
When drill cuttings are received from the well driller, WGNHS geologists prepare geologic logs. These logs contain a detailed description of each sample. Because a sample is usually taken every 5 feet, these logs usually give much more detailed geologic information than the WCRs. Much of the geologic log information is included in the wiscLITH database.
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