(1) Sand and gravel used in filter pack wells shall be thoroughly hosed or sluiced with water, and shall be disinfected with a solution containing at least 50 parts per million chlorine before being placed in the well. All water introduced into a well during construction shall be clean and potable. The well and its equipment, including the interior of the well casing, shall be thoroughly swabbed and cleaned to remove all oil, grease, and foreign substances upon completion of the well's construction. Following the completion of a well, and again after the pumping equipment has been installed, a well and its equipment shall be disinfected by thoroughly agitating and mixing in the well a solution containing enough chlorine to leave a residual of 25 parts per million throughout the well after a period of 24 hours.

(2) The responsibility for the chlorination of the well shall be agreed upon in writing by the parties to the drilling agreement.

(3) The contractor shall clean and disinfect the drilling equipment after drilling in an area of known or suspected contamination or areas of iron bacteria problems.