South Holland Celebrates Success of Deep Tunnel Project

After many years of hard work and patience, South Holland residents can rest assured that their homes are safe from flooding. Thanks to the effectiveness of the Thorn Creek Diversion Tunnel, part of the Little Calumet leg of the Deep Tunnel project, recent heavy rainfall did not result in serious flooding problems for South Holland residents.

For many years, Thornton Township experienced significant flooding.  Hundreds of homes in South Holland along the riverside would flood during periods of heavy rain.  Records show major flooding occurred in the 1940s when the height of flood water at Cottage Grove reached 593.5 feet above sea level.  A greater flood height occurred in 1990, as a new record was set at 595.5 feet.  Through the cooperative efforts of the Metropolitan Water Reclamation District (MWRD), the Village of South Holland and the Mayors and Managers Association, the Diversion Tunnel project was launched.  This project, which utilizes the west lobe of the Thornton Quarry, has provided much needed relief to the Village.  The reservoir provides 3.1 billion gallons of overbank flood protection for the Little Calumet River.  The floodwater from the Little Calumet River and Thorn Creek is diverted into the west lobe of Thornton Quarry through two and one half miles of underground tunnel, which is 30 feet in diameter.

These days, residents can celebrate as the constant monitoring of the Thorn Creek basin means homes are safe from flooding.  As water rises, it will overflow into the tunnel and travel into the west lobe. When heavy rains from Monday, January 10 through Wednesday, January 12 caused the Thorn Creek river to reached flood stage, diversion gates were opened to allow 1.3 billion gallons of excess water to flow into the Thornton Transitional Reservoir.  Trustee Frank Knittle pointed out that the Little Calumet river was expected to crest well over 18 feet from the heavy rainfall. While water did rise relatively high in some yards, the South Holland Public Works department reported that the river crested at 15.3 feet, and homes stayed dry.  Essentially, homes and businesses that would have flooded before the reservoir was constructed remained dry.  The project will save Village residents and businesses millions of dollars and a lot of frustration.

“The Thorn Creek Diversion Tunnel is working great,” said Mayor Don De Graff.  “Residents should not be affected by flooding over the riverbank.”

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The Village of South Holland
16226 Wausau Avenue   South Holland, IL 60473
Telephone 708-210-2913     Fax 708-210-1019
Email:  jwynsma@southholland.org