Donohue & Associates and the Heart of the Valley Metropolitan Sewerage District (HOVMSD) in the Fox Valley, Wisconsin, received a Best of State Award in the 2013 ACEC Wisconsin Engineering Excellence competition. The award recognizes the use of innovative antecedent moisture modeling (AMM) to precisely analyze inflow and infiltration (I/I) reduction efforts. HOVMSD was implementing an aggressive 30% I/I reduction program with its member communities as mandated by its 2004 Facility Plan. By 2009, the communities had spent $15 million on various I/I reduction projects, but an additional $40 to $80 million was needed to meet the 30% mandate as calculated by traditional modeling techniques.

Instead of continuing with this approach, Donohue combined AMM with dynamic hydraulic modeling to predict future system performance and extended the model to communities to predict risk of future basement backups/overflows. As a result, the model showed that spending tens of millions of dollars for additional I/I reduction would only minimally decrease the overflow risk. For example, the City of Kaukauna’s model showed that municipal projects alone would not achieve the mandated I/I flow reductions, and that private property foundation drains and illegal sump pump connections have an enormous impact on their peak flow. Thus, Kaukauna shifted some of their resources to private property I/I inspections and changed their municipal ordinance so that the City can require replacement of non-compliant laterals at the homeowner’s expense. 

Together with the results of previous I/I removal projects, the HOVMSD submitted a new Sustainability Program to WDNR to replace the 30% I/I mandate. The new plan, approved by WDNR, will accomplish the same goal: protecting the environment by minimizing the risk of wastewater entering the Fox River. However, the new approach will result in $40-$80M in cost savings for member communities, its residents, and the District.