TRANSMITTAL LETTER FOR BOARD MEETING OF JANUARY 5, 2012
COMMITTEE ON STORMWATER MANAGEMENT
Mr. David St. Pierre, Executive Director
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Report on meeting held at City of Markham on November 7, 2011 regarding natural channel approach to address erosion and flooding at Calumet Union Drainage Ditch in Markham, Illinois under Contract 10-882-5F, Streambank Stabilization Projects on Tinley Creek, Midlothian Creek, and Calumet Union Drainage Ditch
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Dear Sir:
The Board of Commissioners granted approval to enter into an agreement with Michael Baker Jr., Inc. (Baker) for Contract 10-882-5F entitled Streambank Stabilization Projects on Tinley Creek, Midlothian Creek, and Calumet Union Drainage Ditch (CUDD) on October 6, 2011 at which time City of Markham (City) Alderman Donna Barron expressed concerns on behalf of her neighborhood regarding the natural channel alternative recommended at the conclusion of preliminary engineering. As a result, a meeting was held in the City on November 7, 2011 (presentation attached) to discuss the various alternatives considered during preliminary engineering and the rationale for the natural channel alternative. A lengthy question and answer session followed and it was apparent the residents were still leery of the natural channel alternative. Many residents expressed a desire for the ditch to be encapsulated or hard armored.
During the Little Calumet River Detailed Watershed Plan (DWP) development, erosion issues were identified along CUDD between Sunset and Hamlin Avenues and flooding was reported immediately downstream of this area. In response to these issues, a combination of hard armoring to address erosion and a 4 foot high floodwall alternative was developed at a conceptual level. A contract for preliminary engineering of this project was approved by the Board of Commissioners on May 6, 2010. After detailed evaluation, the DWP floodwall alternative was determined to be infeasible as its height would need to be increased to 11-feet to prevent overbank flooding during the 100-year event. It was also revealed the culvert under Central Park Avenue could not adequately convey the 100-year flow. Preliminary engineering concluded that a natural channel alternative would address both the erosion and flood control components. The natural channel alternative includes the use of bioengineering methods in addition to creation of a wider channel cross section with gentler slopes to both stabilize banks and improve conveyance. The natural channel alternative also includes increasing the size of several culverts, including the Central Park Avenue culvert. A drawback to this alternative is the need for easements over private property to allow for increasing the width of CUDD.
A workshop to present this alternative to residents was held on May 12, 2011, prior to the Little Calumet River Watershed Planning Council (WPC) meeting. Exhibits of the proposed alternative were posted and staff was on hand to explain how the alternative would work. Residents in attendance were surprised to learn the proposed project had changed from a floodwall to the natural channel alternative. At the conclusion of the workshop, the Engineering Department believed the residents were sufficiently appeased to allow for the project to proceed to final design as proposed. Subsequent to this workshop, updates on this project were presented at WPC meetings, at which Alderman Barron and City Building and Housing Director TyWayne Wilson were in attendance. No objections were raised at these meetings.
It is important to note that the U.S. Army Corps of Engineers (Corps) requires an individual permit for most of the alternatives presented. The Corps prefers use of bioengineering to improve or restore waterways to a more natural state. Hard-armoring can be used if it is proven necessary via alternatives analysis and site constraints. Encapsulation is the least likely alternative to receive permit approval.
As described below, the Engineering Department has considered three possible courses of action.
Option 1: Natural Channel Alternative
Using sustainable bioengineering methods, this alternative will stabilize eroded banks, use in-stream features to redirect erosive flow to the ditch’s center, and widen the ditch with flood benches to eliminate overbank flooding for the 100 year event. A site plan is attached for your reference. This alternative has an estimated construction cost of $2.97 million. Minimal maintenance of this alternative is anticipated after the 3 to 5 year establishment period required for vegetation to take hold. Much of the residents’ concern stems from easements necessary to implement this alternative, and they also fear bioengineering will be unable to withstand the flow of the ditch. If the City and residents adamantly refuse to grant the easements required for this option, the scope of this alternative can be modified to address only the critical erosion areas with hard armoring and remove the overbank flooding component. Minor hydraulic improvements, such as replacing the undersized culverts at road crossings, can be made, but no widening of channel cross sections or enlargement of the Central Park culvert would be performed.
Option 2: Minimal Improvements at Critical Points:
As with the second part of Option 1, the project scope could be modified now to address only critical erosion areas with hard armoring along approximately 400 LF and replacing 3 road culverts to improve channel hydraulics. Preliminary construction costs are estimated to be $200,000 for hard armored erosion control and $240,000 for road culvert replacements for a total of $440,000. Although the critical stabilization issues would be addressed, this option is not recommended as the overbank flooding the District is striving to address will still occur.
Option 3: High Flow Bypass Pipe
As a result of the November 7, 2011 City meeting with CUDD residents, the Engineering Department investigated the possibility of routing flows exceeding the 2-year event through an underground bypass pipe. Excess flows would be conveyed through a reinforced concrete pipe routed along the City’s right-of-way in the neighborhood and rejoin CUDD downstream of the existing Central Park Avenue culvert. This option would include the use of bioengineering to stabilize banks at critical erosion areas. No expansion to the Central Park Avenue culvert would be needed. A conceptual construction cost for this option is estimated to be $4 million. In very preliminary discussions with the Corps, they did not rule out this option, but indicated alternatives analysis would have to be performed and, if permitted, mitigation fees would likely to be required. This option is not recommended due to the increased design cost associated with preliminary engineering needed to determine feasibility, increased construction cost, and uncertainty regarding permitting from the Corps.
Based on the foregoing, the Engineering Department recommends proceeding with Option 1 as described above. Unless directed otherwise, the Engineering Department will resume work on the final design of this project as described under Option 1.
Requested, Kenneth A. Kits, Director of Engineering, WSS:JPM
Recommended, David St. Pierre, Executive Director
Respectfully Submitted, Debra Shore, Chairman Committee on Stormwater Management
Disposition of this agenda item will be documented in the official Regular Board Meeting Minutes of the Board of Commissioners for January 5, 2012
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