R2012-130 AUTHORIZING AN AGREEMENT WITH HANSON PROFESSIONAL SERVICES, INC.

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Infrastructure, currently under contract with the City to complete repairs to the Lake Decatur Dam, were asked to review the Tail Water Dam and recommend repairs. On March 1, 2012, divers with Global Infrastructure determined that approximately 7 feet of stream bed had been scoured from beneath the Tail Water Dam. This compromised the integrity of the Tail Water Dam and allowed the pool of water immediately below the dam to empty. The scour under the Tail Water Dam was likely the product of years of erosion immediately downstream of the dam as water spilled over the top of the structure and eventually carried away the stream bed. Repair options to install sheet piling around the dam were presented to City staff in March and April. These options were discussed with the Illinois Department of Natural Resources (IDNR), which oversees dam construction and repairs in the State. The IDNR indicated that the dam was never permitted for construction, since it predated State regulations, and that a permit would be required to allow the dam to remain and for repairs to be made. Professional Engineering Services Agreement Hanson is currently serving as the design engineer for the $3.4 million dam repair project which was recently completed by Global Infrastructure on the Lake Decatur Dam. Hanson assisted the City in performing the initial review of the Tail Water Dam and staff recommends that Hanson perform the required studies to obtain a permit to repair the Tail Water Dam and design repairs to the dam. Hanson's permit preparation and design work on the Tail Water Dam will include: 1. Preparation of a dam Evaluation Report for the IDNR. 2. Perform a hydraulic analysis for the Tail Water Dam. 3. Document the City's operation and maintenance of the Tail Water Dam. 4. Perform a stability and structural analysis of the Tail Water Dam, the surrounding river bank and stream bed. 5. Prepare an environmental assessment of the Tail Water Dam including the preparation of pollution control and Corps of Engineers permits. 6. Prepare plans and specifications for proposed repairs to the Tail Water Dam. 7. Prepare and submit permits to the IDNR. 8. Assist with construction oversight of the dam repairs. The design agreement is for a total not to exceed fee of$82,300. POTENTIAL OBJECTION: There are no known objections to this resolution. INPUT FROM OTHER SOURCES: Hanson Professional Services, Illinois Department of Natural Resources STAFF REFERENCE: Keith Alexander, Director of Water Management, Richard Marley, Public Works Director, Matt Newell, City Engineer. Richard Marley will be in attendance at the City Council meeting to answer any questions of the Council on this item. Page 2