R2014-08 ACCEPTING THE BID AND AUTHORIZING CONTRACT FOR OAKLEY SEDIMENT BASIN REHABILITATION & LAKE DECATUR DREDGING

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DEPARTMENT OF WATER MANAGEMENT Memorandum No.2014-02 January 28, 2014 TO: Mayor Michael T.McElroy and City Council FROM: Ryan P. McCrady,City Manager Keith D.Alexander,Director of Water Management SUBJECT: Contract Award Oakley Sediment Basin Rehabilitation and Lake Decatur Dredging Basins 1 through 4 City Project W 1314 SUMMARY RECOMMENDATION: City Council adopt the attached Resolution awarding a contract to Great Lakes Dredge&Dock Company, LLC to rehabilitate the Oakley Sediment Basin and dredge Lake Decatur Basins 1 through 4 at a cost not to exceed$89,254,535.96. BACKGROUND: The City Council reviewed the project and bid results on January 21, 2014. City staff recommends that the City Council award the base bid to the low bidder, Great Lakes Dredge & Dock. This firm successfully completed the Basin 6 dredging project in 2011 almost 3 months ahead of schedule and on budget. While other bid alternatives that would dredge less of the lake can be done at a lower cost, City staff's opinion is that Great Lakes Dredge&Dock's base bid is the best option for the following reasons: ➢ It would increase the lake's water storage capacity by 30%, which is equal to 52 days of additional water supply for our community. When full,the lake currently has a 174-day supply. ➢ It provides the largest increase in the lake's water storage capacity at the lowest unit cost per cubic yard of dredged material. ➢ The base bid of$89.3M is reasonable for the significant amount of work to be done and is only 0.98%above the Engineer's Estimate of$88AM. ➢ Great Lakes Dredge & Dock has proposed that almost all of their dredging and pumping equipment be powered by electricity which is significantly quieter than diesel powered equipment, eliminates diesel exhaust air pollution concerns and the possibility of diesel fuel contamination in Lake Decatur. ➢ The work will eliminate the mud flats in the Big Creek and Sand Creek areas of Basin 1 that occur when the lake is low and dramatically improve recreational opportunities including boating, swimming and fishing. Exhibit 1 details the locations of the Oakley Sediment Basin and the areas of Lake Decatur proposed to be dredged. Exhibit 2 is the profile of 1) the material to be dredged (shaded in gray), 2) the current bottom elevation of Lake Decatur and 3) what the bottom elevation will be if this project is authorized. Upon completion, virtually all of the water in Basins 1 through 4 will flow to the South Water Treatment Plant intake. I