May 21, 2012  Heavy storms rolled across Minnesota over the weekend. Does it seem as if recent rain storms are harsher than you remember?

A recent study, Doubled Trouble: More Midwestern Extreme Storms, offers statistical data that heavy storms are dumping more rain on states in the the Upper Midwest.  Two environmental groups, the Natural Resources Defense Council (NRDC) and Rocky Mountain Climate Organization, reviewed data collected from 1961 to 2011 at 218 weather stations in eight Midwestern states.

According to the study, released in May 2012, the average number of storms per year with rainfall of 3 or more inches in Midwestern states rose 103 percent, storms of 2 to 3 inches rose 81 percent and storms of 1 to 2 inches rose 34 percent.  The study broke statistics down state by state. In Minnesota, the average number of 3 inch plus storms increased 104 percent during the 51 years considered from 1961 to 2011.  According to the study, the greatest increase occurred in the last decade.

Some may say:  Weather is always changing.  Is there anything behind the environmentalists claims?  Is the data reliable?

A University of Minnesota professor Mark Seely who reviewed the study indicated that it may be unfair to apply the data statewide in Minnesota because data from only 30 weather stations was considered.  Seely indicated that during the late 19th century and early 20th century there was a frequency of thunderstorm intensity  similar to that reported in the study.   Seely did, nonetheless, acknowledge that there is a higher frequency of thunderstorms at almost all locations in the western Great Lakes.

What are the implications of the apparent trend of increased rainfall?

*         Large rains stress infrastructure.  In developed areas with sewer systems, the flows pool and result in direct discharges to nearby receiving waters. Depending on rainfall totals localized flooding may occur.

*         Publicly owned treatment works may be overwhelmed.  In areas where stormwater flows have not been separated from domestic and industrial sewage and flow in the same pipes, untreated wastes including bacteria, toxic chemicals, pesticides, oil and grease, sediment and nutrients may be discharged directly to receiving waters.  In the Midwest, the cities of Chicago, Milwaukee, Detroit and Cleveland each have combined flows.

*        Waterborne illnesses pose a public health concern.  In a 1993 worst case scenario, 54 people died and over 400,000 were sickened when heavy storms washed a disease-carrying parasite into Lake Michigan which is also used as the source of Milwaukee’s drinking water supply.

*         Construction projects with federal and state stormwater permits will be affected.  During heavy rains erosion and sediment controls may be wiped out.  Temporary or permanent stormwater basins may overflow resulting in unpermitted releases from construction sites.  Sites need to be inspected promptly and necessary repairs and corrective measures need to be implemented in short order.

*         Industrial facilities subject to stormwater permitting requirements need to sample stormwater flows.  If laboratory analysis indicates exceedences, facilities may need to consider and implement best management practices.  Due to the cost of corrective measures and repeated sampling, it may be prudent to see if operations and outside storage practices can be changed so that a “no exposure” determination can be applied for in lieu of an industrial permit.

*         Any party who holds a permit many be subject to an inspection or a review of records at any time.  If violations – even what may appear to be non-material conditions – are found, it is possible that an enforcement action will follow.

There are ways to minimize the impact of storms including application of “green infrastructure” stormwater controls such as porous pavement, green roofs, rain gardens, roadside plantings and use of rain barrels.  Many states, local government units and watershed districts require stormwater controls for any new construction.  Other communities are providing financial incentives to businesses and individuals to install stormwater features on their property.

For more information about the study, please see: and  A copy of the study can be found at:

Joseph Maternowski is an experienced attorney practicing in the areas of environmental, administrative, real estate and business law. For information about Joe Maternowski please visit where you can view videos describing Joe’s background and practice.  To receive blog updates and posts, we invite you to subscribe by providing your e-mail address at the space at the top of this page.

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