Agenda - 01-27-2015 - 1 - Laserfiche WebLink

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January 21, 2015 Attachment C 11 G. Stormwater / Flood Control Elements of the Plan 1. Background The Ephesus - Fordham Small Area Plan (SAP) was supported by a Kimley- Horn and Associates analysis in 2011 for both traffic and stormwater improvements. Approximately 1/3 of the site is encumbered by 100 year floodplain as shown in Attachment 1. This is part of a larger Booker Creek drainage shed. A second map shows the floodplain south of the Ephesus - Fordham project area which experienced extensive flooding within the past year. 2. Specific Original Work Alternative drainage improvements have been functionally engineered to provide different flood reduction benefits; i.e. less depth of flooding depending on storm event and /or reduction in FEMA flood mapping area. Culverts were analyzed at Franklin, Eastgate, Elliott and Fordham roads with varying results and costs. 3. Original Cost Estimates The "Implementation and Maintenance Cost" program for stormwater improvements was originally estimated as $1.2 million. This included $210,000 for design, $910,000 for construction and $80,000 for contingency. Annual maintenance was estimated at $35,000 a year. This program was intended for both the Eastgate and Willow area. 4. Stormwater Master Planning Orange County has been in contact with the Chapel Hill Engineer in early January to discuss some of the parameters of their improvements. Chapel Hill reports that there has been some new direction since project inception and more recently since last spring to investigate solutions at both the micro and macro scale with most stormwater flooding amelioration occurring upstream of the project. Nutrient reductions would be onsite as redevelopment protocol /BMP's occurs to a high standard. 5. New Direction The overall greater project area could be considered to be categorized into 3 areas; upstream (with 2 sub - basins); project area and downstream. The upstream basins (and more micro -level stormwater flow attenuation BMP's at the subdivision level) may be the focus of the new flood mitigation techniques, as well as, the project area culvert sizes. A localized stormwater municipal service district (MSD) has been created but not implemented awaiting improvements at the project area redevelopment level. The MSD once implemented would create an ongoing revenue stream for maintenance which is critical.