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Technical Appronch Page 2 federal waters, and "I"nomas Shoal, also located beyond the three-mile jurisdictional limit, was dcamed to contain 'fair" quality sand. Eased on a single vibracore and seismic data, estimates from CERC were that the "volume of usable sand in middle Indian River Shoat is 10.3 x 1Cgcubic yards,' Scientific Environmental Applications, Inc., has acquired and analyzed the vibracore samples and seismic records collected for the iCONS investigation of the Fort Pierce Grid, and has developed a preliminary contour map of mud layers offshore of the southern half of the County which will be reviewed and analyzed prior to developing the final offshore areas for jet probes and vibracore exploration. Additional review of the records and tracts line date will be conducted to refine the field investigations in the vicinity of Indian River Shoal in an attempt to isolate the highest quality sands contained it i this otherwise limited sand resource segment of offshore waters. In August 1980, the U.S. Army Corps of Engineers WSACE) Jacksonville District cofopleted a "Feasibility Report for Beach Erosion Control — Indian River County Baachrs," Project recommendations included beach restoration Project initiatives for the Sebastian Inlet State Recreation Area and Vero Beach. The District obtained a total of 55 vibracores between approximately 3,000 and 4,000 feet offshore of Indian River County in May 1973 and May 1974. These togs and grain size distribution (GSD) Information were requested and have beer) Sent to ATM. The USACE concluded that there were two potential borrow areas and one 'passible' site. ATM will review this data and assess the validity of this information. If available, ATM will perform a site inspection of these cores M the USACE depot to assess sand quality and review the precise location of each of the cores, This data will be compiled and analyzed in developing the field investigation work pram. The document 'Beach Eroslon Control indian River County, Florid8 {USACE, (ktober 1987) contains reference to addliliional sixteen vibracores obtained in late IgUlearly 1985 to better delineate the offshore barrow souse considered in the 1980 study. The core logs and grain We distribution Ctrrtln prwr ded in this effort wril be carefully revie%red, as will all other prior geoterchnnkkeb and eirvVirinawnlal study efforts conducted in Indian River County. in addition, ATM wig nw*w data and information srxrrces dest:nbed in the 1988 Cubit Engineering, Ltd, report 'Beach Preservation Plan far Indian River County, Florida' which summarizes sand source tnvmtigalrana undertaken at the time of the report preparation ATM will review previously acqurred USACE vibnxxwes And widependertif trampling to determine optilTial borfnw area geometries and a selective dredging plan desoVied in Ilia CPE (1989) 'City of Verna Beach Restoration PrtT}ect Assessment Report While the cores revealed excessive fine-grained r'naf nal percentagtrs, ATM will review the data to determine if the site warrants furlhef Wivestlpation for the vibracore study to be undertaken by the Project Team. Task 1.2 Identify OHshvre larget PnQylies and!Can0i4te Areas flit in Eigalion This task will develop a fiend 'investigation plan for the preliminary phase of the geotechnical investigation to identify and rank high probability sand sources. These areas will be determined by synthesizing prior report data (surtirrnanzed above), bathymetric data indicative of potential shoat feature(s), proximity to the Project segments to be nourished, and location relative to federal jurisdiction inside the Three Nautical Mile trine. While there appear to be considerable sand reserves in federal waters, efforts for this study will principally be concentrated in State waters. As the ICONS study collected only 'reconnaissance -level' data and information in the north half of the County, the proximity of even moderate amounts of surficial beach -quality sands to the identified Project initiatives in Sectors 1, 2 and 3 warrants consideration of additional investigation of the north half of the County offshore areas. Following a complete synthesis of all existing bathymetric and geophysical data, a plan view graphic(s) of the Indian River County offshore area will be prepared to guide decision-making for jet probes, vibracores and side scan sonar mapping areas (Task 1.3, described below). ATM will work with Dr. Gary Zarillo, P.G. and Maryann Civil, P.G. of SEA, Inc. in defining the locations to conduct core borings and bathymetric data collection targeting of the search area(s) of highest potential. ATM will work with SEA, Inc. in defining the locations to conduct core borings and bathymetric data collection targeting of the 99 Nm&Wc Nv doegnWoiad wsii+ MOPE OF WORK 042099c.9r