Section R. 325.10308a - Variances from MCL for total trihalomethanesRule 308a.
(1) The department identifies all of the following as the best technology, treatment technique, or other means generally available for achieving compliance with the maximum contaminant level for total trihalomethanes as established in R 325.10604a:(a) Use of chloramines as an alternate or supplemental disinfectant or oxidant.(b) Use of chlorine dioxide as an alternate or supplemental disinfectant or oxidant.(c) Improved existing clarification for THM precursor reduction.(d) Moving the point of chlorination to reduce TTHM formation and, where necessary, substituting chloramines, chlorine dioxide, or potassium permanganate for the use of chlorine as a pre-oxidant.(e) Use of powdered, activated carbon for THM precursor or TTHM reduction seasonally or intermittently at dosages not to exceed 10 milligrams per liter on an annual average basis.(2) The department shall require a community supply to install or use, or both, any treatment method identified in subrule (1) of this rule as a condition for granting a variance, unless the department determines that the treatment method identified in subrule (1) of this rule is not available and effective for TTHM control for the system. A treatment method shall not be considered to be available and effective for a community supply if the treatment method would not be technically appropriate and technically feasible for that supply or would only result in a marginal reduction in TTHM for the community supply. Upon application by a supplier of water for a variance, if the department determines that none of the treatment methods identified in subrule (1) of this rule is available and effective for the community supply, the supplier of water shall be entitled to a variance pursuant to section 20 of the act. The department's determination as to the availability and effectiveness of the treatment methods shall be based upon studies by the supplier of water and other relevant information. If a supplier of water submits information to demonstrate that a treatment method is not available and effective for TTHM control for that community supply, the department shall determine whether the information supports a finding that the treatment method is not available and effective for that supply before requiring installation or use, or both, of the treatment method.(3) Pursuant to R 325.10305, the department shall require a schedule of compliance to be established that may require the community supply being granted the variance to examine any or all of the following treatment methods to determine the probability that any of the methods will significantly reduce the level of TTHM for that community supply: (a) Introduction of off-line water storage for THM precursor reduction.(b) Aeration for TTHM reduction, where geographically and environmentally appropriate.(c) Introduction of clarification where not currently practiced.(d) Consideration of alternative sources of raw water.(e) Use of ozone as an alternate or supplemental disinfectant or oxidant. If the probability exists, the supplier of water shall determine whether any of the treatment methods is technically feasible and economically reasonable, and that the TTHM reductions obtained will be commensurate with the costs incurred with the installation and use of the treatment methods for that community supply.(4) If the department determines that a treatment method identified in subrule (3) of this rule is technically feasible, economically reasonable, and will achieve TTHM reductions commensurate with the costs incurred with the installation or use, or both, of such treatment method for the community supply, the supplier of water shall be requested to install or use, or both, that treatment method in connection with a compliance schedule pursuant to R 325.10310. The department's determination shall be based upon studies by the supplier of water and other relevant information. The supplier of water shall not install or use a treatment method not described in subrule (1) or (3) of this rule to obtain or maintain a variance from the requirements of R 325.10604a or in connection with any variance compliance schedule.Mich. Admin. Code R. 325.10308a