(1) Either the department or a POTW with an approved POTW pretreatment program may initiate program modification at any time to reflect changing conditions at the POTW.   Program modification is necessary whenever there is a significant change in the operation of a POTW pretreatment program that differs from the information in the POTW's submission, as approved under ARM 17.30.1413.

(2) POTW pretreatment program modifications must be accomplished as follows:

(a) For substantial modifications, as defined in (3) of this rule:

(i) The POTW shall submit to the department a statement of the basis for the desired modification, a modified program description (see ARM 17.30.1412(2) ) , or such other documents the department determines to be necessary under the circumstances.

(ii) The department shall approve or disapprove the modification based on the requirements of ARM 17.30.1411(6) following the procedures in ARM 17.30.1413(2) -(6) .

(iii) The modification shall be incorporated into the POTW's NPDES permit after approval.   The permit will be modified to incorporate the approved modification in accordance with ARM 17.30.1362.

(iv) The modification shall become effective upon approval by the department.   Notice of approval shall be published in the same newspaper as the notice of the original request for approval of the modification under ARM 17.30.1413(2) (a) (i) .

(b) The POTW shall notify the department of any other (i.e., non-substantial) modifications to its pretreatment program at least 30 days prior to when they are to be implemented by the POTW, in a statement similar to that provided for in (a) (i) above.   Such non-substantial program modifications shall be deemed to be approved by the approval authority, unless the department determines that a modification submitted is in fact a substantial modification, 90 days after the submission of the POTW's statement.   Following such "approval" by the department, such modifications shall be incorporated into the POTW's permit in accordance with ARM 17.30.1362.   If the department determines that a modification reported by a POTW in its statement is in fact a substantial modification, the department shall notify the POTW and initiate the procedures in (a) above.

(3) Substantial modifications.

(a) The following are substantial modifications for purposes of this rule:

(i) changes to the POTW's legal authorities;

(ii) changes to local limits, which result in less stringent local limits;

(iii) changes to the POTW's control mechanism, as described in ARM 17.30.1411(6) (a) (iii) ;

(iv) changes to the POTW's method for implementing categorical pretreatment standards (e.g., incorporation by reference, separate promulgation, etc.) ;

(v) a decrease in the frequency of self-monitoring or reporting required of industrial users;

(vi) a decrease in the frequency of industrial user inspections or sampling by the POTW;

(vii) changes to the POTW's confidentiality procedures;

(viii) significant reductions in the POTW's pretreatment program resources (including personnel commitments, equipment, and funding levels) ; and

(ix) changes in the POTW's sludge disposal and management practices.

(b) The department may designate other specific modifications, in addition to those listed in (a) above, as substantial modifications.

(c) A modification that is not included in (a) above is nonetheless a substantial modification for purposes of this rule if the modification:

(i) would have a significant impact on the operation of the POTW's pretreatment program;

(ii) would result in an increase in pollutant loadings at the POTW; or

(iii) would result in less stringent requirements being imposed on industrial users of the POTW.