CC - Agendas - City Council - REGULAR - 10/23/2012

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1.2 Survey and Mapping 1.2.1 Field Survey The Project Team shall perform the following survey services: • Survey of channel section at waterline crossing to get current condition of the scour hole. • Survey of miscellaneous features identified through field reconnaissance and data collection. • Survey the main channel, and 200 feet beyond the channel banks, for HEC-RAS River Stations 1.8826 through 2.1416(9 total). • Supplemental survey for Clearwater Drive at Willow Creek. • Survey of culvert crossing at Clearwater Drive and Willow Creek Tributary • Sealed Survey report. KWE,as a subcontractor to JEF,will conduct the Field Survey. A detailed scope of services is included as Exhibit 1. 1.2.2 Topographic Mapping The hydraulic and floodplain studies will utilize the existing 1 foot topographic mapping and aerials prepared in(2010) under the Willow Creek Floodplain Delineation Study(FDS)project. 1.3 Public Involvement The Consultant shall meet,up to three(3)times with the City and local stake holders regarding the flood inundation limits determined as part of Tasks 1.4 and 1.5. The Consultant shall prepare up to three(3) 24"x36"exhibits for each of the meetings. 1.4 Willow Creek Levee Floodplain Evaluation based on FEMA's Levee Analysis and Mapping Project(LAMP) Guidelines JEF shall perform up to three(3)hydraulic modeling scenarios, using as a basis for model development, the HEC-RAS hydraulic analyses for Willow Creek- Willow Creek Road to Williamson Valley Road, prepared by JEF as part of Floodplain Delineation Study for a Portion of Willow Creek dated June 2011. In addition,hydraulic modeling scenarios will be conducted in accordance with the Draft Federal Emergency Management Agency(FEMA) LAMP Guidelines. Hydraulic modeling will be based on the 100-and 500-year peak discharge(s), determined by Arroyo Engineering(Effective FEMA discharges). HEC-RAS hydraulic analyses and floodplain modeling results will be reviewed and approved by the City. JEF will coordinate with FEMA throughout the mapping process. 1.5 Willow Creek Levee Floodplain Revisions,and FEMA Submittal Based on the three(3)hydraulic modeling scenarios developed under Task 1.4, a Preferred Alternative will be selected.The Preferred Alternative will be refined based on more detailed HEC-RAS modeling. Modeling results will be used for final Willow Creek Levee flood hazard delineation. The detailed modeling and delineated flood hazard will be documented in an update to the Floodplain Delineation Study for a Portion of Willow Creek Technical Support Data Notebook(TSDN). Tasks for completing the Willow Creek Levee floodplain revision and submittal to FEMA are discussed below. 1.5.1 Hydraulic Modeling The Project Team shall conduct detailed HEC-RAS hydraulic analysis for the interior areas of Willow Creek Levee, upstream of Willow Creek Road. HEC-RAS modeling and results will be documented in the updated TSDN. Detailed hydraulic modeling will be based on the 10-,25-, 50-, 100- and 500-year peak discharges. All hydraulic modeling will be based on revised hydrology prepared by Arroyo Engineering and obtained from City. HEC-RAS hydraulic analyses shall be in accordance with FEMA standards. HEC-RAS hydraulic model results shall be used for revision of the effective FEMA Flood Insurance Study(FIS). October 8,2012 Willow Creek and Willow Creek Tributary Restudy Page 2 of 6