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BOOK 9 pw 700 The Indian River County Board of County Commissioners accepted the Beach Committee's recommendation and hired American Coastal Engineering to Design, Permit and Construct the P.E.P. reef. Staff was instructed to assist with the design and permitting of the reef. Since the hiring of American Coastal Engineering in September of 1993, the County has commissioned several field investigations, background studies and ground breaking analysis of the P.E.P. Reef. Most of these investigations were required by the Department of Environmental Regulation as part of the permitting process. The DEP has required the County to be able to predict how the beach will change after the P. E. P. Reef is installed (e.g., what is the expected performance of the P.E.P. Reef). The most significant problem with predicting the performance of the P.E.P. Reef (with absolute confidence) is that it is an experimental technology. To date, staff is aware of only five other installations of a submerged breakwater in the United States and four of these installations are less than two years old. At the time the County began the permitting process, the only project with any history was the Dupont project in Palm Beach. The other projects, including the Palm Beach Midtown project,_were less than a year old. At the time of this writing, staff has now reviewed several monitoring reports from the P.E.P. Reef midtown project, corresponded with out of state engineers regarding the three New Jersey breakwaters and directed two model investigations of the proposed Vero Beach project. Each of these reports, however limited, provide some insight into the expected performance of the Vero Beach P.E.P. Reef. Both the New Jersey Avalon submerged breakwater and the Palm Beach Midtown P. E. P. Reef units settled 1 to 4 feet into the sand. The New Jersey project had the worst settlement with an average of 4 feet while the Midtown project has experienced an average of 3 feet for the first 54 units and 1.9 feet for the remaining 279 units. It is important to distinguish the Midtown first 54 units because these were the only units aligned during Hurricane Andrew. Under higher wave conditions there is a greater chance that sediments will be eroded from around the units thereby allowing further -settlement. P.E.P. settlement was not thought to be a significant problem in Vero Beach because a jet probe survey found a layer of rock beneath the sand. The underlying rock must be considered an asset because without it some type of foundation would be necessary. Staff reanalyzed the survey data and computed the maximum depth of settlement for each of the proposed P.E.P. Reef units (see Exhibit B). The P.E.P. Reef units will likely come to rest on the rock at elevation -9.4 to -10.6 N. G. V. D. This means the P.E.P. Reef on average will have between 3.4 and 4.6 feet of water over them at mid tide water levels. Water depth over the reef is important because this is the most important criteria for reducing wave heights. Both the University of Florida Vero Beach Physical Model Study (U of F 1994) and the Midtown project have found the P.E.P. Reef reduces wave heights. P.E.P. Reef wave height reduction can now be accurately determined for different water depths, breakwater sizes and wave heights. 18 MARCH 28, 1995 s �