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Fngineering, Surveying (10YQ .$ 930,675.47 <br />ESTI TFC GRA ND TO TA L $ 10,237,430.16 <br />In order to independently interpret the Cobb Fendley Report, City leadership hired Hayter <br />Engineering, Inc. to evaluate and summarize the report in 2018. Hayter prepared a memorandum. <br />to the city dated November 7, 201& <br />"During rainfall events in 20.15, 20.16, and 2017 residents living along Big Sandy Creek <br />Tributaries 4 and 6 experienced flood damages to their homes (see attached reap)... load damages <br />were most prevalent south of Lamar Avenue along 26th Street between Hubbard Street and <br />Collegiate Drive. the City of .Maris (City) retained Cobb-Fendley (CF) to perjbrm an analysis of <br />BigSandy Creek Tributaries 4 and 6 to determine improvements that could be made to minimize <br />flooding during rain events, CFYs report recommends as three -phased improvement plan,.,/roin <br />.Lamar Avenue south to the South Collegiate Drive 7"Mil.flead, totaling $10.2 million. <br />Hayter E, ngineering (HEI) reviewed CF, 's report and modeling and concluded that the biggest <br />factor in the observed flooding is the channel section between Simpson Street to ClarkLane. As <br />such, HEI hags focused their attention on this area in developing a preliminary solution that would <br />mitigate flooding along this section of channel, The table belowprovides some insight into why <br />HE7 believes the channel section from Simpson Street to Clark Lane plays a large role in the <br />observedflooding in this area. In particular, please note the floww coming to and the floww area of <br />each crossing. " <br />Crossing <br />Tributary <br />Crossing Size i <br />Flow <br />Flow Area <br />(span x rise) <br />(CFS) <br />Culbertson <br />Trib. 4 <br />2 - 5..5x 4.5' <br />400 <br />49.5 <br />20h SE <br />"rib. 6 <br />2 - s -..O' x.3,5'' <br />399 <br />56.0 <br />sinipsoll <br />`nb.4 - D/S Confluence <br />2 - 9ff x 2.5" <br />876 <br />45,O <br />Clei k <br />�i'SCq�ntluet�ice,4 <br />Lj�jb-A - D <br />�-6- <br />76 <br />J: <br />-84.0, <br />With theflows passing through the undersized existing culverts, HEIsurtnised that necessary <br />flows would not fit within existing channels, nor the existing channels easements if they were :an <br />place. "Upstream and downstream channel modifications would be required to accommodate <br />the increased span and rise of any proposed culverts. SinceTIE1 does not believe that lowering <br />the existing channel 'sflowline is afeasible alternative, EI focused on an alternative that <br />includes homelproperty buyouts along the west side qf'the channel. However, rather than buying <br />out these homes1properties to increase the capacity of the concrete channel, HEI is suggesting a <br />more cost-efficient,?ption that involves increasing the capacity of thefloodplain along the west <br />side of the existing channel. The existing concrete channel would be utilizedfor lowflows and <br />larger raiqfi711 events would spill out into an expandedfloodplain (a result of homelproperty <br />bqyouts along the west side of the reach) and be stored there until able to pass downstream. <br />They also recommended increasing the sizes of the culverts at Simpson Street and Clark.Lane, <br />M <br />