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"'t,. "' Mr. Tom Browning Page 2 the field survey and map check for the project. We are also assuming that there are adequate control points close to the bridge crossings so they can easily be tied together with GPS. Based on your Scope of Services, ICON will complete the following tasks: 1. Research and Data Collection: Obtain information for the project from the CWCB including FEMA maps and reports, digital mapping, benchmarks and field control, names and addresses of potential contacts and any other hydrologic or hydraulic data available. 2. Map Check: ICON will complete GPS field surveys to obtain elevation data at several points in the vicinity of the bridges that are accessible to our survey crew, Field control used for the aerial mapping will be obtained from the CWCB and used as the horizontal and vertical control for the map check. The elevation data will be analyzed and the points compared to the digital mapping developed for the project. A determination of the mapping accuracy will be made based on the: two sets of data. 3. Field Bridge Measurements: There are four bridges that cross the Crystal River within the project study reach. Field measurements will be taken that includl~ the following parameters: a. Bridge length b. Bridge height (water to low chord) c. Deck thickness (low chord to top of road) d. Pier location, width, and shape (if applicable) e. Bridge width f. Digital photos of both the upstream and downstream face of the structure g. Estimation of water depth (measured if possible) If field control is near the bridge locations, a top of road elevation will be obtained at each end of the structure. If field elevations cannot be obtained, the top of road elevations will be estimated from the digital mapping. This will serve as the basis for determining elevations for the HEC-RAS modeling. As mentioned previously, the upstream bridge is on gated, private property and cannot presently be accessed. We are assuming the CWCB or County will obtain access for us at the time of our site visit. If not, we will model that area without a bridge in place. 4. Hydrologic Evaluation: We will complete a Flood Flow Frequency Analysis for the Crystal River utilizing existing stream gage records at Marble, Redstone, and above Avalanche Creek. Flood flows will be developed using a Log-Pearson Type III frequency distribution. Flows will be developed for the 10-, 50-, 100-, and 500-year events.