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Evaluation of the Sonic Water Level Meter <br />In the fall of 2004, a sonic «-ater level meter ~~~as used to meastue «-ater levels in a subset of wells <br />to evaluate its potential to improve the efficiency- of measuring ~~-ater levels in bedrock wells. The <br />sonic meter «as used iii combination with another water level measuring device to evaluate the <br />accuracy of the sonic meter. The sonic meter is a small portable handheld meter that requires only <br />a small opening at the top of the ~~~ell and a fe« seconds to obtain a ~~ ater level measurement. <br />The sonic meter ~~ as used to collect «-ater levels at 26 sites. The results and a comparison to a <br />steel tape or m-scope measurement are presented in Figure Al and Table Al. As can be seen <br />from Figure A1, the eater level measurements obtained from the sonc meter have a 99 percent <br />correlation to the steel tape or M-scope measurements. Table Al sho«-s that most of the <br />measurements collected from the sonic meter are within 2 feet and 2 percent of values obtained <br />from other measurement devices over a large range in depth to water. These results indicate that <br />although the percent difference bet~~een the sonic meter and other devices measurements is small, <br />the absolute difference can be significant. It is recommended that other direct measurement <br />devices such as the steel tape or water level meter be used primarily and a sonic meter be used <br />only when necessai-~-. <br />700 <br />soo <br />r.. soo <br />v <br />a <br />0 <br />U <br />U! <br />~ 400 <br />H <br />U! <br />U! <br />U! <br />A 300 <br />0 <br />a <br />v <br />~ 200 <br />100 <br />Depth to Water (Sonic) <br />Figure Al -Comparison of Sonic Measurements and Other Device Measurements <br />SPDSS Phase 4 Task 39 TM -Final <br />0/20/2008 A-3 <br />0 100 200 300 400 500 600 700 <br />