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The MMSD has been investigating control of private infiltration and inflow (I/I) sources since the 1980s. These efforts were reinvigorated in 2002 when the MMSD entered into an agreement with the Wisconsin Department of Natural Resources to develop a private property I/I control program. This program is part of MMSD's larger 2020 Facility Planning process.

This paper discusses the development of Milwaukee MSD's private property I/I control program including the following:

The setting for the program.

Justification for a private property I/I reduction program

The relationship of the program with the 2020 Facilities Plan

Key elements of a private property I/I reduction program

Alternative program approaches that will be considered for the 2020 FP

Expected benefits and costs

Issues that must be addressed prior to implementing the program

The MMSD has over five decades experience in attempting to control private property infiltration and inflow. The first step occurred in 1954 when the plumbing code changed to not allow new connections of foundation drains or sump pumps to the sanitary sewer system. MMSD once again studied the situation in the early 1980s when it executed a private property I/I pilot project. This study and parallel Separate Sewer Evaluation Surveys determined that private sector sources contributed 59% of the total I/I flow. The MMSD recommended that member communities develop programs to disconnect downspouts and sump pumps in the separate sewer areas and, where cost-effective, repair the publicly-owned portion of sanitary laterals. The MMSD allowed communities to compel home-owners to disconnect pre-1954 foundation drains, but did not require it. None did until recently. The MMSD is now examining the issue of private property I/I once again having realized that continued I/I reduction will not occur without addressing private sources. This examination will provide key data for the development of the ongoing 2020 Facility Plan efforts which will balance reducing flows against building more conveyance, storage, and treatment.

Key elements of a private property I/I reduction program include inspection and testing, repair, funding, flexibility, and program administration. A key issue involves the removal of foundation drains connected to the sanitary sewer system. Over one-third of the buildings in the MMSD sanitary sewer service area were built before 1954 with currently legal foundation drain connections to the sanitary sewer.

The private property I/I reduction study assembled five potential approaches to reducing private I/I. One end of the spectrum targets proper maintenance by relying on private inspection and certification of houses on sale of property. The other end of the spectrum targets removing I/I only from priority sewersheds by developing a program of systematic inspection and repair. MMSD is considering letting each customer municipality decide for themselves their own preferred approach rather than specifying exactly how communities must meet wet weather control goals.

The estimated cost to reduce peak daily private property I/I flow ranges from 1.90 to 2.25 million per 1 million gallon per day (MGD) reduction. The unit costs could be cost-effective, in certain circumstances, compared to reducing I/I from public property sources or building new conveyance, storage, and treatment facilities.

There are a host of issues that must be addressed prior to implementing a private property I/I reduction program. Issues that cause community resistance to the program include equitable treatment of newer and older communities, demands on municipal staff and budgets, and the tradition of not spending public funds on private property, among others. Issues that cause owner resistance to the program include cost, disruption, drainage issues, and property rights. The MMSD is working through these issues at the community level through its Technical Advisory Team and other groups. The Technical Advisory Team includes municipal representatives from all its member communities and meets regularly to discuss and guide MMSD initiatives. At the individual level, the MMSD is incorporating its private property I/I reduction initiatives into the 2020 Facilities Plan public involvement program.
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Document Type: Research Article

Publication date: 2004-01-01

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