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<regulation prefix="Regulation" num=".24" citation="COMAR 26.04.04.24" title_num="26" subtitle_num="04" chapter_num="04" heading="Disinfection of Wells and Water Supply Systems.">
  <paragraph num="A.">
    <text>Upon completion of well construction activities, the permittee shall disinfect a water supply well in accordance with this regulation.</text>
  </paragraph>
  <paragraph num="B.">
    <text>Whenever any work is done on the well after disinfection of the well by the well driller, the person doing the work shall be responsible for disinfection of the well and water supply system in accordance with this regulation.</text>
  </paragraph>
  <paragraph num="C.">
    <text>Material. Tablets or dry granular material may not be used as the only chlorination material. The materials, which may be used for disinfection, are:</text>
    <paragraph num="(1)">
      <text>Calcium hypochlorite,</text>
    </paragraph>
    <paragraph num="(2)">
      <text>Sodium dichloro-triazine dehydrate; or</text>
    </paragraph>
    <paragraph num="(3)">
      <text>Sodium hypochlorite.</text>
    </paragraph>
  </paragraph>
  <paragraph num="D.">
    <text>Standard Disinfection Procedure.</text>
    <paragraph num="(1)">
      <text>The chlorine shall be placed in the well in quantities that will produce a concentration of at least 100 mg/l chlorine. The amount required to obtain this concentration will depend on the casing diameter and the amount of water in the well.</text>
    </paragraph>
    <paragraph num="(2)">
      <text>The well shall be chlorinated using all of the following sequential steps:</text>
      <paragraph num="(a)">
        <text>Chlorine tablets or granular chlorine shall be dropped in the top of the well and allowed to settle to the bottom, or a prepared 10 gallon chlorine solution, with a chlorine concentration of at least 100 mg/l, but not more than 500 mg/l, shall be placed in the bottom of the well by pumping or gravity through a tremie pipe, drill rod, hose, or other approved method.</text>
      </paragraph>
      <paragraph num="(b)">
        <text>A chlorine solution of at least 10 gallons and producing a concentration of at least 100 mg/l, but not more than 500 mg/l, in the well shall be introduced (poured) into the top of the well. All surfaces above the static level shall be washed with this solution.</text>
      </paragraph>
      <paragraph num="(c)">
        <text>After the solution has been placed in the well, the water shall be agitated to thoroughly disperse the solution. Agitation may be accomplished by turning the pump on and off, or if no pump is available, by using a bailer, a swab, a plunger, air, or other approved method.</text>
      </paragraph>
      <paragraph num="(d)">
        <text>If the well has been connected to the pressure tank and distribution system, a small amount of the chlorinated water shall then be pumped through the system to thoroughly disinfect the system.</text>
      </paragraph>
      <paragraph num="(e)">
        <text>The well shall be allowed to stand without further agitation for at least 12 hours.</text>
      </paragraph>
      <paragraph num="(f)">
        <text>If a residual of at least 5 mg/l chlorine remains in the water after 12 hours, the well shall then be pumped to waste until the odor and taste of chlorine is no longer detectable. If less than 5 mg/l free residual chlorine is found in the water after 12 hours, the disinfection procedure shall be repeated.</text>
      </paragraph>
    </paragraph>
    <paragraph num="(3)">
      <text>Chlorinated water and water pumped during the flushing of the well during the disinfection procedure may not be discharged:</text>
      <paragraph num="(a)">
        <text>To an on-site sewage disposal system; or</text>
      </paragraph>
      <paragraph num="(b)">
        <text>Directly to surface waters of the State.</text>
      </paragraph>
    </paragraph>
  </paragraph>
  <paragraph num="E.">
    <text>Disinfection Procedure for Wells That Do Not Respond to the Standard Procedure.</text>
    <paragraph num="(1)">
      <text>If, after testing, the well cannot meet the bacteriological standard of this chapter, it shall be chlorinated as in §D of this regulation.</text>
    </paragraph>
    <paragraph num="(2)">
      <text>If the well remains unresponsive after repeating the standard disinfection procedure per this section, a volume of water chlorinated to a concentration of 100 mg/l and at least two times the volume of chlorinated, standing water in the well, but not less than 50 gallons, shall be introduced into the well in order to completely displace the volume of chlorinated, standing water and force it out into the water bearing formation.</text>
    </paragraph>
  </paragraph>
  <paragraph num="F.">
    <text>If bacteriological contamination persists after repeated disinfection, the Approving Authority may require the well to be abandoned and sealed in accordance with this chapter.</text>
  </paragraph>
</regulation>