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<br />: <br /> <br />~~ <br /> <br />MOFFATT & NICHOL <br /> <br /> <br />EXHIBIT~ <br /> <br />2001 N. Main Street <br />Suite 360 <br />Walnut Creek, California 94596 <br /> <br />" <br /> <br />(925) 944-5411 <br />Fax (925) 944-4732 <br /> <br />Grace Le, Sr. Civil Engineer <br />City of Redwood City <br />1017 Middlefield Road <br />Redwood City, CA 94063 <br /> <br />Subj: Additional Scope - Levee Assessment <br />Redwood Shores Levee System <br />M&N File No: 6786 <br /> <br />Dear Grace: <br /> <br />Per our earlier discussion, I have prepared a scope of work to conduct additional statistical <br />analyses to estimate the deficiencies of the Redwood Shores levee system, as well as assist <br />the Huffman-Broadway Group with procuring permits for levee improvements resulting from <br />the Coastal Analysis. A detailed scope of work is provided below and a fee estimate is <br />attached. <br /> <br />BACKGROUND <br /> <br />We are presently under contract with the City to prepare a Preliminary Coastal Assessment for <br />the levee system, which includes a topographic survey and coastal engineering analyses. We <br />have completed these tasks and identified areas which are deficient. However, a key finding <br />of the work was that the combined 1 % annual chance of flooding event, which FEMA bases <br />their levee certification criteria on, is significantly influenced by bottom features around Bird <br />Island and the probability of simultaneous occurrence of high water levels and wind waves in <br />the area. <br /> <br />For the preliminary assessment, we used standard engineering assumptions to develop <br />required crest elevations rather than site specific features, as they vary around the peninsula, <br />and there is a good possibility that the additional analysis proposed will narrow down the range <br />of crest elevations already calculated. <br /> <br />SCOPE OF WORK <br /> <br />Task 1: Supplemental Coastal Engineering Analysis <br /> <br />1. Refine the previously prepared wave hindcasts and include transformation of wind- <br />waves, including wave refraction and wave dissipation, over the Bird Island marsh. <br />This will be performed using the CEDAS numerical model or similar empirical programs <br /> <br />2. Since the record of water levels for the NOAA Redwood Creek gage was very short, <br />develop a synthetic time series for the Empirical Simulation Technique (EST) <br />simulation. This will include development of lookup tables to for wind-wave generation <br />and wave runup based on the wave hindcast. <br /> <br />3. Develop annual maxima for still water levels and peak values. Perform a Generalized <br />Extreme Value Distribution (GEVD) analysis to estimate the 1 %-annual-chance peak <br />