Lake Blu� Ravine Restoration for Erosion Control

Ravine Park RavineVillage of Lake Blu�, IL 2010-2013

Funded by 2010 Great Lakes Restoration Initiative (USEPA) - $788,900

Project Management Village of Lake Blu�

Project PartnersHey and Associates (Project Design, Construction Management and Final Report)Lake Blu� Park District (Provided Easements for Work Access) V3 Companies, Woodridge, Illinois (Construction)

Project SummaryThe project primarily involved the placement of approximately 6,100 tons of Class RR-4 and RR-5 (IDOT Gradation Classi�cation) rock rip rap along a 2,200 foot segment of a ravine streambed and adjacent lowest portions of the ravine side slopes.

The subject ravine in which the project was performed, known as the Ravine Park Ravine in the Village of Lake Blu�, has a watershed of 375 acres.

Land use within the watershed is a fully developed suburban area. Due to high stormwater �ows through the ravine during signi�cant rain events, (modeled at 122 cubic feet per second for the two year event), severe erosion problems existed. Over the project reach it was estimated that there was an average downcutting of 3 to 4 feet over a 30 year period. The downcutting of the ravine streambed was triggering side slope failures.

100% of the ravine streambed was raw and unvegetated. As a result of the erosion, extensive quantities of sediment were being transported to Lake Michigan during each major rainfall event. Prior to the project, soil erosion in the ravine was estimated to be contributing several hundred tons of sediment annually into Lake Michigan. This was primarily due to scouring of the clay ravine streambed and adjacent lower ravine side slopes by streamwater �ows piped to the ravine from an urbanized watershed of 375 acres.

Key Project Themesravine bed downcutting, rip rap, stormwater volumes

The primary goal of the project was to signi�cantly reduce the rate of erosion or downcutting of the ravine streambed and as a result to reduce sediment loading to Lake Michigan.

OverviewHistorical Context

Goal: Reduce Ravine Bed Erosion

Project Concerns

June 2, 2016

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A project by the Alliance for the Great Lakes, Chicago Botanic Garden, The Field Museum, and Openlands.

Lake Blu� Ravine Restoration for Erosion Control

1) Obtain easement access from Lake Blu� Park District for construction2) Model potential impcts. Hydrologic and Hydraulic modeling was utilized to develop a riprap �ll section which would be stable and could convey 100-year discharge through the ravine. 3) Stabilize ravine bottom and toe of side-slope areas. Aeas were graded and �lled with RR-4 and RR-5 Rock Riprap to re-establish streambed elevations two to four feet above existing conditions. 4) Protect roadway from slope failure. A steel sheetpile wall was utilized to stabilize a portion of the ravine side-slope that was failing and in danger of impacting an adjacent roadway.5) Improve drainage from tableland stormwater inputs near ravine (roadway)6) Implement stormwater erosion controls at outfalls

Obtaining funding for the project was critical. Of the estimated 19,000 linear feet of ravine streambed in the Village the segment of ravine that was selected for this project was one of the areas of most signi�cant erosion, and was the most easily accessible due to a large part of the ravine area within the project owned by the Lake Blu� Park District and the Village of Lake Blu�. Public Village Roadways were located immediately adjacent to nearly the entire length of the project, making access relatively easy, and without the need for any private easements.

Criteria for Success

Action Strategies

June 2, 2016

When 375 acres of watershed carves out a ravine

Slope FailureToe Scouring

Fallen Trees Bed Scouring

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While the short term impacts of this type of construction project are signi�cant, these impacts are outweighed by the long term bene�ts.

Signi�cant erosion in many ravines is occurring and over time, if the erosion rates are not reduced, this erosion will lead to very signi�cant side slope failures within the ravines, leaving the side slopes raw and unvegetated. Eventually tableland will be lost if the streambed erosion remains.

To date the project has con�rmed our belief that sometimes hard armoring is the best and most cost e�ective solution when stormwater �ows are too high for vegetative solutions.

Many thanks to George Russell and Je� Hansen for sharing this project with the ravine region.

For More Information: Je� Hansen, Village Engineer at Village of Lake Blu� at jhansen@lakeblu�.org

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The project completed 3 years ago. The installed rock rip rap has remained in position along the entire project length. No new ravine slope slides have been observed within the project limits.

The general conclusion is that the project has been very e�ective in reducing the rates of erosion and that very little follow-up maintenance will be necessary in future decades.

Lessons Learned

Lasting Impact

Community Engagement

Advice to Ravine Communities

June 2, 2016

End-of-pipe erosion control 2 Years after Completion

Stream bed and toe stabilization

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