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Professional Services Agreement <br /> C08L0198A <br /> Attachment A - Scope of Services <br /> A�reement Date:Januarv 18,2010 <br /> ProjeCt: Lake Decatur Dam Hydraulic Study <br /> Project Description: <br /> The Sangamon River channel located downstream of the dam has experienced scour due to oultlet flows from the <br /> spillway and gated outlet works. As part of their Joint Application for Permit review associated with the current <br /> (2009)dam repair project,the Illinois Department of Natural Resources(IDNR)has suggested that the City of <br /> Decatur continue to observe and maintain the channel bottom to prevent additional scour. IDNR also has some <br /> concerns about the erosion countermeasures proposed in the permit. Hanson will perform a hydraulic analysis of the <br /> existing dam to model the existing condition;evaluate the predicted scour below the dam; and recommend <br /> countermeasures. <br /> Services: <br /> The Scope of Services to be provided is limited to the following: <br /> The project scope is to investigate the scour hole downstream of Lake Decatur's dam and spillway structures. <br /> The project will include field surveys of the existing channel downstream of the dam, developing a hydraulic <br /> model of the downstream channel, developing and assessing methods for scour countermeasures and generating a <br /> report which summarizes the results of the study. The following outline summarizes the scope of the project in <br /> more detail: <br /> 1. DATA COLLECTION <br /> Collect available data for the project which will include available discharge data from the <br /> �DNR/OWR, USGS topographic data and USGS stream flow for the watershed,record plans, <br /> operation/maintenance manuals far the existing dam and sluice gate <br /> 2. FIELD SURVEY <br /> This phase of the project will include a site visit to compile a survey request Once complete, a <br /> survey request will be finalized. It is anticipated that the field survey will include both traditional <br /> and hydrographic survey of the area downstream of the dam including the tailwater structure. <br /> Channel bed material samples will also be taken downstream of the spillway. Enclosed is a map <br /> depicting the survey requirements for the study. <br /> 3. SCOUR ANALS[S OF SYILLWAY <br /> Develop a hydraulic model using data collected from the survey. "The model will be used to <br /> deterir�ine the existing and potential scour do�vnsh-eam of the spillway. Hanson �vill also <br /> i�sn Kc�� z Z <br /> I:A I I ti j�)�l AfiAt�dlM�l,�p�¢I�31ppp`eH(isulg f�gn�pgt�91TIKV Pti�A_r ev Z[I U� <br /> � <br />