News Release: Scientific Study Shows Significant Increase in Rainfall Standards for Lake County

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April 24, 2019

News Release: Scientific Study Shows Significant Increase in Rainfall Standards for Lake County

Climate change and the direct and indirect impacts it has to Illinois, and more specifically to Lake County, has become an important topic in recent years. The Illinois State Water Survey has been studying the climate conditions being seen across the State of Illinois. Their findings show that Lake County is receiving significant amounts of rainfall. 

Recently, the Illinois State Water Survey released updated statistical rainfall data for Bulletin 70--Frequency Distributions of Heavy Precipitation in Illinois. Initial evaluation of rainfall data from Bulletin 70 indicates that Lake County is receiving between 20% and 45% higher rainfall amounts. This new data has a significant impact on not only the residents of Lake County, but also the Lake County Stormwater Management Commission (SMC). 

"We have always used Bulletin 70 as best available data for our Watershed Development Ordinance (WDO)," said Kurt Woolford, SMC Chief Engineer. "The WDO is a countywide ordinance that sets forth minimum requirements for the stormwater management aspects of development within Lake County. Based on the increased rainfall amounts from Bulletin 70, SMC will need to evaluate and make revisions to the WDO because a significant amount of regulatory criteria are affected by the new data."

There will be an impact to storm sewer and detention design, floodplains, building protection, wetland requirements, and much more. With Lake County rainfall design standards increasing between 20% and 45%, flood prevention measures, such as detention basins and storm sewers, will need to be larger and will take up more space on development sites. In addition, there will be an increased cost of construction.

Although many stormwater requirements will be impacted, SMC is looking at all of the facts before making any official recommendations.

"We know the WDO will need changes, but right now it's unclear to what extent," said Woolford. "The SMC Commission requested an initial technical discussion at our Technical Advisory Committee to evaluate all requirements and determine the potential impacts. We reviewed and discussed the impacts last Thursday. The two main issues that will be studied further are the affects to detention basins and floodplain and flood prone areas. Until we can evaluate all the facts, SMC will be drafting a temporary document that will provide guidance on how to handle new developments and permits."

The current version of the WDO, and any changes that are made based on the rainfall study, directly impacts Lake County residents, residents downstream of the County, and potential developers. Any time the County sets forth regulations for County development, it's in the best interest of residents and surrounding communities. The WDO's regulations do their best to make sure new development doesn't create negative environmental impacts to County residents and those downstream. The WDO also contains building protection requirements so new homes and businesses being built have all the necessary requirements for flood prevention.  

SMC is presenting their findings and recommendations at the Commission meeting on May 2. 

"We know Lake County is experiencing more rainfall; we've experienced it firsthand," said Craig Taylor, SMC Chairman and District 19 Lake County Board Member. "The record flood event in July 2017 is just one example of the increased precipitation our County is seeing on a regular basis. I'm looking forward to hearing SMC's recommendations on how we can improve our flood prevention methods with new development and keep our residents protected from flooding due to the uptick in increased precipitation events."

The WDO approval process includes a public comment period, followed by a review from the Commission and the Lake County Board prior to adoption. For more information about SMC, visit the website



Brooke Hooker
Interim Communications Manager