MCES Proposed Infiltration-Inflow Program Amendment

The Metropolitan Council Environmental Services (MCES) has proposed an amendment to its requirements to reduce infiltration & inflow (I/I) to the sanitary sewer system. Key elements of the proposed amendment are: (1) Adding an ongoing I/I reduction program beginning in 2013, and (2) Revising the demand charge program, using “trigger” criteria instead of a date for implementation.

MCES proposes to work with communities to implement an initial inflow and infiltration reduction program during 2007 through 2011, and MCES will prepare an estimate of the cost of I/I reduction to eliminate the sources of excessive peak flows. MCES will allow communities to undertake work to reduce inflow and infiltration using local funds, as long as those funds equal or exceed the estimated cost of I/I reduction. If a community does not voluntarily undertake this work, MCES will add an equivalent surcharge to the community’s municipal wastewater charges.

Starting in 2013, MCES will begin the second phase of the I/I reduction program. Elements of the on-going program include:

(1) continuation of the allowable peak hour flow by metershed using current design standards for interceptors;
(2) adjustment of average baseline flow by metershed to normalize the effects of precipitation variability (drought and wet periods), to avoid penalizing communities for successful water conservation and I/I mitigation, and to account for growth;
(3) adjustment of measured peak flow by subtracting estimated peak I/I into MCES interceptors in the metershed;
(4) continuation of appeal process that recognizes unusual conditions that contributed to a peak flow event, such as construction that may have temporarily allowed storm water entry into the sanitary sewer or other extraordinary circumstances; and
(5) allowing up to four years, after the flow metering period in which a peak flow exceedance occurs, for the community to complete I/I reduction work equal to the total estimated cost to eliminate sources of excessive I/I.

Under the proposed plan, MCES may institute a wastewater rate demand charge for those communities that have not met their inflow and infiltration goals(s), if the community has not been implementing an effective I/I reduction program in the determination of the Council, or if regulations and/or regulatory permits require MCES action to ensure regulatory compliance.

MCES will hold a public hearing on July 13, 2010, to receive comments on a proposed amendment to its 2030 Water Resources Management Policy Plan, Infiltration/Inflow (I/I) Program.

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