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40 40 40 Technical Approach Page 9 TASK 9 WAVE REFRACTION/DIFFRACTION ANALYSIS OF INDIAN RIVER SHOAL DREDGING IMPACTS ON ADJACENT SHORELINE Assuming the regulatory agencies require an analysis of pre- vs. post -dredging shoreline impacts associated with sand excavation of a portion of the Indian River Shoal complex, ATM will establish and conduct a numerical simulation of such impacts. A wave refraction/diffraction study of the borrow area and adjacent shorelines will be conducted to satisfy these requirements. The model REF/DIF will be utilized. Wave data will be assembled from a combination of the Wave Information Study (WIS) hindcast data and real-time wave gauging apparatus in the area. A grid will be established sufficient to fully simulate the bathymetry and shoreline adjacent to and contiguous with the South borrow area anticipated to be dredged to support beach restoration activities by the County. Model simulations will be conducted on sufficient wave 'cases' to adequately demonstrate the wave propagation over and shoreward of the Indian River Shoal (borrow area) and to the adjacent shoreline. The grid will encompass the entire borrow area and depths seaward a sufficient distance to generate the incoming wave fronts, and a distance of up to 8 miles north -south (alongshore). Grid coverage with these dimensions should be sufficient to depict pre- and post -dredging impacts to the near -field and shoreline areas in the lee of the borrow site. A report will be prepared detailing the methodology, set-up and results of the simulation. TASK 10 NATIVE BEACH SAND SAMPLING ANALYSIS AND REPORTING Surface sand samples will be collected concurrently with the beach profile surveys, and assumes that the design -level beach profile surveys will be conducted in February 2000. Sand samples will be collected along nine (9) longshore transects, corresponding to DNR monuments R-4, R-7, R-10, R-13, R-17 (Sectors 1&2); R-37, R-40, R-43, R-46 (Sector 3). This spacing meets standard DEP requirements of one transect per 3,000 feet of shoreline and corresponds to previous sand sampling performed by Martin County in June 1990. Sand samples will be collected at elevations top of dune (-12), Toe of Dune (—+9), +6, +3, 0, -3, -6, -9, and -12 feet NGVD. It is possible that certain of the above -stipulated beach profile transects may not support sample acquisition at the - 12 ft contours, respectively, due to the presence of nearshore hardbottom. Samples will be analyzed using standard ASTM procedures to determine the grain size distribution. Siirfara camnt� t;r• i��:.. r..s.._ ._ .,..��-£ +f,i.l e,@ t . _. �iiii! =1 !!_'t!:{7 -L;;, ,rig .. - i��. vnanvia $dril Flir3 be collected with a petit ponar grab sampler (from a boat). Each sample will be analyzed to determine grain sizes using the same nested sieve set as detailed above in Task 8.2 (assumes a total of 81 samples will be collected and analyzed). The results will be used to analyze native beach grain characteristics (sand, shell, and percent mud) throughout the Project beaches planned for nourishment.