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- - - � Technicai Approach Page 3 search area(s) of highest potential. Siesmic data will be collected only if warranted based Oil I/W fifidings of the jet ,probe or vibracore studies. If required, survey €racklines to establish a coverage 'grid' of high ,potential candidate areas will be established which will utilize maximurn slant range on the seismicyside scan unit in order to maximize daily coverage areas (at an additional cost not to exceed $ 10, 000). Task 1.3 Perform ,let Probes at Candidate Borrow Areas A jet probe investigation of target areas identified in Task 1.2 will be performed to determine the depths to rock and the characteristics of the overlying strata. Sand samples will be collected at each probe site to examine the sand characteristics and to confirm/validate the previously collected core "GSD" data and the positionsllocations of the cones. This investigation will optimize the time expended in the field investigations to collect bathymetric, side scan and core hnrings. It is belleved that the U.S. Corps of 'Bngincaers may have destroyed the original cores, that were collected in tho 1970's and the 1980's. Upon completing the four day field jet probe investigation and analyzing the sand material, ATM will finalize the boundaries for the bathymeinc survey to perform Task t.4 and Task 1.7 as described below. Task 1.4 Bathymetq Surveys of f' lential S pi rr�e Situ Bathymetric data will be acquired for the identrfied borrow areas. wrath all instrumentation integrated to an onboard vessel navigation and tracking system (HYPACK'") Vessel position will be interfaced with a Trimble"' Differential Global Positioning System (DGPS). Thermal paper scroll output as well as digital records of the suds scan signal vwll be acquired .and trackers with the DGP'S At instrument tow speeds suitable for accurate signal feedback, it is estimated that 18 to 20 line"mies of data can be acquired in a 'typical' field day. Such a day assumes goad weather and sea state condrllons for ten to twelve hours, and a trackline spacing of approximately 500 feet in the onshore -offshore direction combined with "lie lines run north -+loath at approximately 1.000 feet on enter Task 1.5 PQ rm 54tscanSow rar This task will to performed after the tet probe study its com*led This time of the year should minimize the potential for weather days and offshore condaions should allow the work to be completed in a 3 to 4 day period It m assumed that a single mobilization of crew and equipment will be rewired The vessel platform and navigationallposition interface for the side scan instrumentation wilt be provided during one held effort with ATM directing the field work and Oceaneering Technologies (CTI) working with ATM in the field program. This field investigation will be undertaken when the borrow areae are determined from the results of the core baring investigation described in Task 1.7. if the hardbottom snapping requires site -scan sonar for specific featufes identified in the Task 2 investigations, the side -scan sonar mapping may be expanded to include these additional target area(s). Field efforts in June 1999 should help to ensure that weather patterns are favorable to sustained moderate to calm sea state conditions critical to precision data acquisition. Additionally, if evidence of sub-bottorn strata indicates rock fragments (i.e., in core borings) or underlying rock (i.e.. during jet probes),. a seismic study of the candidate borrow area will be investigated using an integrated Klein", seismic/side scan towfosh to optimize field time and data acquisition at the time of the side -scan survey (costs are included as a optional, additional cast item below in Task 1.9). Task 1.6 Process Side Scan Data Side scan data will isolate hardbottom features mapped on the seafloor and will also present a relative distinction between surface sediment types. Seismic record review and interpretatioi i will focus on acquiring areas of hardbottom that may effect dredging limits and maximization of dredging activity pursuant to project construction (e.g., locations of pipeline corridors). Areas displaying emergent hardbottom (reef) and near-bottorn submerged structure will typically require that such offshore segments be bounded or eliminated from consideration in their entirety to avoid disturbance of sensitive marine biological communities and damage to dredging equipment. Alternate plan and cross- sectlon views of the borrow areas will be developed in Task 3.1 using the vibracore data. 99tumr1A(0 ane tlaalpnVIAed WE ACOPE OF MRK 0420590,