Engineers cope with rising tide of rain (UPDATE)
Published: November 16, 2009
Tags: 100-year storm, American Public Works Association's Wisconsin Chapter, engineer, G factor, Grisa, Grisa Scale, Milwaukee Metropolitan Sewerage District, public works, rainfall, storm water, University of Wisconsin-Madison Center for Sustainability and the Global Environment, Wisconsin Initiative for Climate Change Impacts
Increased intensity and frequency of rainstorms has researchers in the state considering more storm-water regulations.
The so-called 100-year storms, which dump roughly six inches of rain in 24 hours, are occurring more frequently. That is leading planners, up to their ankles in floods, to wonder if they must design larger systems to handle more storm water.
Between 1950 and 2006, the amount of rainfall in Wisconsin has been increasing by 10 percent to 15 percent annually, according to research from the University of Wisconsin-Madison Center for Sustainability and the Global Environment. Milwaukee, for example, had two storms in 2008 that landed on the area’s top 10 list for inches of rainfall in a 24-hour period.
To make sure storm-water systems are designed to handle heavier loads, a state work group is considering whether Wisconsin should set minimum design standards for storm-water control systems, including sewers and retention ponds. The state regulates storm-water runoff cleanliness but has not created statewide minimums for managing certain quantities of rain, said David S. Liebl, statewide storm-water specialist with the University of Wisconsin-Cooperative Extension. Municipalities now approve their own standards for designing storm sewers, Liebl said.
A work group in the Wisconsin Initiative for Climate Change Impacts in spring will release recommendations for controlling storm water. Liebl, co-chairman of the initiative work group investigating storm-water control, said the group likely will recommend the state investigate recent storms and decide how large of a deluge systems must be able to handle.
“The public benefit is that you don’t rely on the budgets of small municipalities to develop these standards,” he said.
Rick Eilertson, city of Fitchburg environmental engineer, said municipalities are too busy dealing with compliance with the state’s storm-water runoff cleanliness standards to pay much attention to the possibility of capacity rules.
“Right now, the only proposed changes to the regulations deal with water quality,” he said, “so I don’t know that municipalities out there understand or are being aware of what the next things coming are.”