R2019-89 Resolution Authorizing a Professional Services Agreement with Hanson Professional Services Inc. for Lake Decatur Dam Gates Evaluation

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6/7/2019 Item Coversheet '� . Public Works DATE: 6/7/2019 MEMO: 2019-48 TO: Honorable Mayor Moore Wolfe and City Council Members FROM: Scot Wrighton,City Manager Matthew Newell,P.E.,Public Works Director Keith Alexander,Water Producrion Manager SUBJECT: Resolution Authorizing a Professional Services Agreement with Hanson Professional Services Inc. for Lake Decatur Dam Gates Evaluation SUMMARY RECOMMENDATION: Council adopt the attached Resolution Authorizing a Professional Services Agreement , with Hanson Professional Services Inc. for Lake Decatur Dam Gates Evaluation for a fee not to exceed$153,900. BACKGROUND: On Monday,December 10,2018,while operating the Lake Decatur dam bascule gates,the north bascule gate failed to raise from its full down position. The bascule gates are the long gates that span the top of the dam. Large hydraulic pistons lower or raise the gates as needed to allow water to flow over the dam to maintain the necessary lake depth. This failure created a 24-hour period during which a considerable amount of water flowed uncontrolled out of the lake. The lake lost nearly 2'of water overnight. On Tuesday,December 11,the gate finally responded to repeated activation attempts and was raised to its full up position. Since then, we have not lowered the north gate below its 60%up position. � It is believed that one of the four hydraulic pistons that power the north bascule gate seized for some reason. However,there could also be other explanations,including debris blocking the front of the gate which sits underwater out of sight of normal inspection. With the summer weather approaching and hopefully reduced Sangamon River water flow,the Public Works Department proposes to retain the services of Hanson Professional Services to review the bascule gates including the hydraulic cylinders to determine the cause of the December failure and recommend necessary repairs. Hanson Professional Services has provided Lake Decatur dam engineering and repair services to the City for the past 15 years. Since they are the firm that is most familiar with the dam,and located nearby in Springfield,they were contacted to provide the proposed bascule gates evaluation. Hanson has assembled a turnkey operation to perform the inspections. Their team inc�udes � Christy Foltz,a respected local contractor who will provide the necessary equipment to access the gates and hydraulic cylinders. Underwater inspection of the front face of the bascule gates will be performed by Global Infrastructure who completed the last major rehab of the bascule gates and has provided underwater inspections of the upstream face of the dam in the past. Hydraulic. review and testing of the system will be conducted by John Henry Foster,a firm that currently services the dam hydraulic systems. , The evaluation is complex and encompassing in order to determine the problem and its likely cause. The scope of work is ' composed of four major task: 1.Hydraulic Cylinder Testing-A118 hydraulic cylinders,encompassing both the north and south bascule gates will be tested to assure that there are no other lurking problems with the large pistons. ' 2.Gate Inspection-Both bascule gates will be examined for possible damage. This will include the use of divers to inspect the upstream face of the gates. 3.Upstream Face of the Dam Inspection-With divers mobilized at the site,we will have them inspect the upstream(lalce side) face of the entire dam. This portion of the dam has not had an underwater inspection in approximately 15 years. � 4.Preparation of a Summary Report and Recommendations-This will include the likely cause of the December gate failure and specify the follow-up work necessary to design the necessary repairs. Task details are on page A-1 through A-3 of the agreement. https://decatur.novusagenda.coMAgendaWeb/CoverSheet.aspx?ItemID=2070 1�2 ,