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Beinalorf and Associates Grand Harbor Request for Waiver Page Two BOOK 66 October 10, 1986 There are several conditions that can create high water- in the River during a storm event. These would vary from a rainfall condition with little or no wind to a storm condition with tidal surge build up at the inlets due to wind. This latter case will cause the water to flow from the ocean into the river creating the flood condition. The worst condition, as verified by the FEMA maps, will be from this latter case with wind and surge conditions at the inlets. Under this condition, filling along the river within the flood zone would have no adverse effect on the flood elevations. The flood elevation is controlled by many factors including the ocean elevation, the inlets and river physical characteristics and the river elevation (not volume). Part of the river flooding will be created by the action of the wind on the river water surface creating waves. The height of the wave and surge is a function of the amount of area the wind has to act on. Filling the lands in question would decrease the area on which the wind could act and therefor decrease the flood wave and surge elevation. The net effect could be a very small reduction in flood elevation. It should be noted that the Grand Harbor project as currently planned cannot comply with the above noted requirement of the stormwater ordinance without the waiver and still complete the project. Any attempt to complete the project would require dredging in the lower m areas of the project which could endanger environmental areas and would require additional permits. Conformance with the present ordinance will not improve flood protection to the development. Public Works Director Jim Davis explained that with the actual amendment to the Stormwater Ordinance that was approved last week, the applicant needs to prove that the project is situated in an established tidal environment; that the project meets all other requirements of the stormwater ordinance; and does not create a material adverse impact on flood protection of other lands in the environment. In staff's opinion, Grand Harbor meets those requirements with the exception of the cut and fill balance. He advised that the applicant is planning to use 646,000 cubic yards of material to fill in the existing storage volume and another 320,000 cubic yards to fill in the excavation. Director Davis reported that he had done a very simple analysis as to the effect this fill would have in the flood plain area. Using a 25 -mile length of the Indian River, approximately 11 miles wide, he figured that this amount of fill would raise the tlood stages approximately 3/10's of an inch. Staff's recommendation is that we go ahead and grant the waiver. He felt it is going to be difficult to determine the cumulative effect of 23