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APPENDIX B <br />PROCEDURE FOR WATER LEVEL MEASUREMENT <br />1.0 OBJECTIVE <br />The objective of this procedure is to guide the collection of groundwater level data from observation <br />wells. <br />2.0 BACKGROUND <br />Water-level measurements are fundamental to groundwater studies. Some of the major uses of water- <br />level data are to indicate the directions of groundwater flow and areas of recharge and discharge, to <br />evaluate the effects of manmade and natural stresses on the groundwater system, to define the hydraulic <br />characteristics of aquifers, and to evaluate stream-aquifer relations. <br />3.0 EQUIPMENT <br />All equipment should be assembled, calibrated, and tested before arriving at the site. All items that <br />potentially come in contact with the groundwater should be pre-cleaned. <br />Well Measurement Equipment <br />^ Electronic water level measuring tape accurate to within 0.01 foot. <br />^ Any additional project-specific sampling equipment as required. <br />^ Field logbook. <br />^ Photographic record, if appropriate. <br />^ Pressure transducer and data collection equipment <br />4.0 MEASURING POINT <br />For comparability, water-level measurements must be referenced to the same datum (elevation). The <br />measuring point is established in reference to land surface datum and is the most convenient place to <br />measure the water level in a well. Measurement points change from time to time, especially on private <br />wells. The measuring-point correction of a water-level measurement converts the measurement to a <br />distance above or below land surface at the well. <br />The measuring point must be as permanent as possible, clearly defined, marked, and easily located. If at <br />all possible, position the point so that a leveling rod can be set on it directly over the well and also so that <br />the measuring tape can hang freely when it is in contact with the measuring point. Frequently, the top of <br />the casing is designated as the measuring point; because the top of the casing is seldom smooth and <br />horizontal, a particular point should be designated and marked clearly. <br />5.0 METHOD <br />Many types of electrical instruments have been devised for measuring water levels; most operate on the <br />principle that a circuit is completed when two electrodes are immersed in water. Commonly, atwo- <br />conductor cable and special probe are used. Current is commonly supplied by batteries. <br />Ordinarily, two-conductor electric tapes are 100- to 200-feet long and are mounted on ahand-cranked reel <br />that contains space for the batteries and some device for signaling when the circuit is closed. Electrodes <br />O / 11-4V 152/00-05 B-1 Final APPend_B_WL_Meas.doc <br />