Grandwood Lake / Grandwood Lake Dam
APRIL 2017 UPDATE
Statement from Mike Warner, Director, Stormwater Management Commission regarding the dam:
Recap of previous actions:
A. Late in 2016, the decision was made to remove the failing steel plates under the dam structure, as sudden failure of those plates would have created an unsafe structural situation for the dam and a flood wave that could have potentially damaged the park and downstream properties.
B. A sheet pile dam was installed a few months ago in front of the steel plating
C. The failing steel plating was removed
D. During the recent extended rainfall events in late March through early April, the sheet piling that was installed was being overtopped, and has partially failed along one side, which will eventually dewater the lake to a lower level and expose the lake bottom.
E. From a downstream flow standpoint, there is not a concern that the flow in the partially failed ‘ruptured' condition will exceed the flow that was previously overtopping the plates.
F. Concerns now include: ensuring scour and erosion don't occur around the existing concrete; and ultimate design of a replacement for the lake outflow structure.
1. There is no concern that dewatering the lake will create a condition where the lake cannot refill itself.
Grandwood Park Lake is approximately 9 acres in surface area.
If it is assumed the lake is an average of 10 feet deep, the lake would hold 90 acre-feet of water.
The tributary area to Grandwood Park Lake is approximately 19.5 square miles as shown below.
One half of an inch (½") of rainfall runoff from the upstream 19.5 square miles will generate nearly 520 acre-feet of volume.
That small storm event creates enough volume to fill the lake 5 times, within one to three days.
2. Allowing the lake to dewater, creates a safer condition (low/no water pressure concern) near the outlet to rebuild the outlet structure into whatever design is ultimately chosen.
3. With a lower water level, the physical construction process will be easier for access and workmanship considerations and lower the cost of construction for the chosen design.
4. Right now, all ideas on reconstruction are being accepted and considered, with an eye on cost of the solution and long-term effects.
5. There is currently a short-term plan in process to place large rock around the rupture to address potential erosion around the existing concrete structure. The amount of rock placed will be determined based on achieving the desired protection and will be a call made during the rock placement operation.
6. Rock placement and an engineering design meeting is scheduled for Monday (4/10) to discuss all options on the table.
Michael D. Warner, PE, CFM
Lake County Stormwater Management Commission
500 Winchester Road, Libertyville, IL 60048
The Park District is aware of the break in the temporary dam. A repair was attempted on Tuesday evening, but due to high water and extreme pressure, that repair did not hold. We have been advised that we should not attempt another repair until the current high water in the area goes down. Our first concern is for the safety of our residents. We continue to work with engineers and Lake County to develop short-term and long-term options.
MARCH 2017 UPDATE
The temporary coffer dam is in place, the steel weirs of the dam have been removed, and the immediate risk of failure has been remedied. The enginnering firm contracted for this work, McClure Engineering, is in the process of evaluating the condition of the dam structure, and will submit a report to the Board of Commissioners once it is complete.
DECEMBER 2016 UPDATE
The walkway over the dam has been closed. The coffer dam to remove the risk of sudden failure of the dam is being installed. The next step is to remove the steel weirs that hold back the water, then have a complete evaluation of the structure. Stay tuned for updates .....
AUGUST 2016 UPDATE
COMMUNITY MEETING - Tuesday, September 13, 2016
Join representatives from the Park District, and Lake County Storm Water Management Commission to review the results of the Dam Inspection and Repair Recommendation report. Cost estimates and next steps will be discussed for the following options:
- Rehabilitation of the dam (approx. $900,000)
- Replacement of the dam (approx. $1,700,000)
- Do nothing at this time (approx. $2,000,000 - $5,000,000 when it fails)
The Grandwood Lake Dam impacts all tax payers in the Grandwood Park Park District
The Park District encourages everyone in the community to attend this IMPORTANT MEETING
WHEN: Tuesday, September 13, 2016
TIME: 6:30 p.m.
WHERE: Grandwood Park Park District
36630 N. Hutchins Rd.
Gurnee, IL 60031
Please contact the park district office at 847-356-0008 if you would like to view either of the below documents:
Dam Inspection and Repair Recommendations
Sept 13 2016 Grandwood Lake Dam presentation
JULY 2016 UPDATE
The water level flowing over the dam finally subsided enough for the structural evaluation to be safely completed. The Park District is now waiting for the written evaluation from M Squared Engineering.
APRIL 2016 UPDATE
Unfortunately, there is no change to the information below ...
JANUARY 2016 UPDATE
The structural inspection was started on Decmeber 4, 2015. However, it could not be safely completed due to the high level of water flowing over the dam weirs. At this time, we are waiting for the water level to drop to allow for a safe structural inspection. Both SMC staff and M Squared Engineering staff are monitoring the water levels in the lake/over the dam. The water levels over the dam may not drop until after the spring thaw. We will update this status as we receive additional information.
Please contact the park district office at 847-356-0008 if you would like to view the following document:
October 22 2015 Special Session (minutes from Special Public meeting on 10/22/2015)
GRANDWOOD LAKE & DAM UPDATE
October 22, 2015 at 6:30 p.m.
Grandwood Park Park District
36630 N. Hutchins Rd.
Lake County Stormwater Management (SMC)
Intergrated Lakes Management (ILM)
Can we save the lake?
Are we at risk?
Why now - what's changed?
IT'S YOUR NEIGHBORHOOD!
The Park District has been asked, "What is all this about?", and "Why now - What's changed?".
Information that will be shared at the meeting:
- Des Plaines watershed project findings
- Grandwood Lake Water Quality Study
- Evaluation of the Lake and Dam Structure
- Possible Options, associated cost estimates, and the impacts to our community
- Next steps
This PUBLIC MEETING is to inform residents, answer your questions, and provide an opportunity for a Q&A with the experts.
DON'T MISS IT !!
The Grandwood Lake dam was constructed in 1941 by the impoundment of Mill Creek. In the 1960s, the area surrounding the lake was subdivided for residential development, leading to the establishment of the Grandwood Park Park District (GPPD) in 1965. In the fall of 2014, personnel from the Lake County Stormwater Management Commission (SMC) reviewed the condition of the dam and identified significant structural concerns, including settling, cracking, and erosion around the dam structure that could lead to its failure.
***** The photos below are EXAMPLES of the natural changes to the lake that would occur IF a dam removal project were to ever happen in Grandwood Park. The Park District Board of Commissioners have not made any decisions -- the process is in the investigative stages and ALL information will be shared with the community *****
The GPPD retains liability for the dam structure and is responsible for any damages that may be caused as a result of its failure. For this reason, the GPPD has begun investigating the feasibility of removing the Grandwood Lake Dam. The Lake County SMC evaluated various flood scenarios and determined that removing the dam would not increase flood elevations, and in some cases actually lower the flood risk associated with Mill Creek.
One potential dam removal scenario involves removing the overflow weirs that currently hold the lake in place, retaining the dam structure to serve as a pedestrian crossing. In place of the lake, a wet prairie would be established, through which Mill Creek would flow as a free-flowing stream just as it did prior to installation of the dam. A series of walking trails and even a fishing pond could be established to allow for direct recreational interaction with the area.
The GPPD has secured grant funding through the Lake County Watershed Management Assistance Grant to develop a public outreach campaign that will educate residents about the benefits of dam removal and prepare the way for an eventual removal project to take place within Grandwood Park.
In the coming months, public meetings will be announced, and information will be made available to residents at local community events. The GPPD hopes to establish a dialog with the residents about this important focal point within our community.
If you wish to see any of the documentation below, please contact the Park District office at (847) 356-0008.
2014 Juy Presentation Agenda
FINAL Mill Creek Stream Inventory Summary
2014 Aug Presentation Agenda
2014 September Presentation Agenda
2015 March Presentation Agenda
SMC Dam Evaluation and Removal Scenarios
2015 May Presentation
2015 June Presentation Agenda
2015 July Presentation
2015 August - Grandwood Lake & Dam - Update