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sealed off to prevent commingling with water in a deeper aquifer of good <br /> quality. <br /> 4.7. WELL GROUTING AND CONSTRUCTIONS <br /> The primary purpose is to prevent contamination, pollution and degradation of <br /> water wells and of the ground water by intrusion of poor quality water and cross <br /> contamination of aquifers. <br /> 4.7.1. The annular space between the well casing and the wall of the drilled <br /> hole, or between the conductor pipe and the wall of the drilled hole or the <br /> well casing shall be filled with approved cement grout or Bentonite clay, <br /> or other sealant material approved by the Director, from the ground <br /> surface into an impervious formation under-laying the uppermost aquifer. <br /> If an impervious formation does not exist, the annular space shall be filled <br /> to a sufficient depth to prevent polluted or contaminated water from <br /> entering the well. The minimum depth of the annular seal shall be as <br /> follows: <br /> Public Water Supplies ....................... 100 Feet <br /> Individual Domestic Well ................... 100 Feet <br /> Industrial Wells.................................. 100 Feet <br /> Agricultural Wells.................................50 Feet <br /> 4.7.1.1. Local conditions will determine depth of seal. Any deviation <br /> from Ordinance requirements will require a Special Water Well <br /> Permit. <br /> 4.7.2. Gravity installation of sealing material, without the aid of tremie or grout <br /> pipe is prohibited unless the interval to be sealed is dry and in no case <br /> where the interval is over 30 feet in depth. <br /> 4.7.2.1. In placing the annular seal, a tremie pipe shall be installed <br /> within 5 feet of the desired seal depth and removed as the <br /> grout is installed. <br /> 4.7.3. Sealing Material: <br /> 4.7.3.1. Neat Cement - 1 bag (94 lbs.) Portland Cement to 5 to 10 <br /> gallons of potable water. <br /> 4.7.3.2. Cement Grout - Not more than two (2) parts by weight of sand <br /> and one (1) part by weight of cement (per bag of cement) to 5 <br /> to 7 gallons of potable water. <br /> 4.7.3.3. Bentonite-sealing materials and their uses shall be in <br /> accordance with the manufacturers specifications or as <br /> approved by the Director. <br /> EHD 43-03 Page 12 of 27 WELL STANDARDS <br /> 10/9/07 <br />