Md. Code Regs. 26.04.04.24

Current through Register Vol. 51, No. 22, November 1, 2024

Section 26.04.04.24 - Disinfection of Wells and Water Supply Systems

A. Upon completion of well construction activities, the permittee shall disinfect a water supply well in accordance with this regulation.

B. 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.

C. Material. Tablets or dry granular material may not be used as the only chlorination material. The materials, which may be used for disinfection, are:

(1) Calcium hypochlorite,

(2) Sodium dichloro-triazine dehydrate; or

(3) Sodium hypochlorite.

D. Standard Disinfection Procedure.

(1) 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.

(2) The well shall be chlorinated using all of the following sequential steps:

(a) 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.

(b) 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.

(c) 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.

(d) 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.

(e) The well shall be allowed to stand without further agitation for at least 12 hours.

(f) 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.

(3) Chlorinated water and water pumped during the flushing of the well during the disinfection procedure may not be discharged:

(a) To an on-site sewage disposal system; or

(b) Directly to surface waters of the State.

E. Disinfection Procedure for Wells That Do Not Respond to the Standard Procedure.

(1) If, after testing, the well cannot meet the bacteriological standard of this chapter, it shall be chlorinated as in §D of this regulation.

(2) 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.

F. If bacteriological contamination persists after repeated disinfection, the Approving Authority may require the well to be abandoned and sealed in accordance with this chapter.

Md. Code Regs. 26.04.04.24

Regulations .24 adopted effective 42:1 Md. R. 19, eff.1/15/2015