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coverage of existing hardbottom . The intent of this effort is to eliminate the expense of towing a side-scan sonar array . ATM will make a reasonable effort to digitize and overlay the reef edges onto a coordinate system ; the County acknowledges that the accuracy of this effort may be no better than +/- 60 ft. Adequate horizontal buffers between apparent edges of exposed nearshore hardbottom and edge of proposed mitigative reef will be employed . Aerial photography, bathymetric survey data , jet probe findings , and sub-bottom profiling data will be reviewed and assembled in digital form according to depth , thickness , or isopach , of unconsolidated sandy sediment, and location of hard bottom structure . Based on the field information gathered , a planform representation of the thickness of sediment found within the mitigation site shall be produced and used to guide Task 1 . 2 for location layout , unit placement, and possible need for the use of a geotextile grid . Sub-bottom profiling data will be presented as a contour map of thickness , or isopach , of unconsolidated sediments , with elevations referenced to NGVD . A bathymetric contour plot will be generated from the acquired hydrographic survey data , with two-foot intervals represented as an overlay in AutoCAD at 1 n = 200 ' . Cruise track plots of the bathymetric tracklines will be furnished to the County in AutoCAD at 1 " = 500 ' or 1 " = 600' as appropriate to depict vessel/instrument tracklines . A brief (letter) report of field methods utilized , and dates of survey, will be transmitted along with the herein referenced digital files . TASK 1 . 2 : MITIGATION DESIGN Task 1 . 2 . 1 Preliminary Location Layout The preliminary location layout will utilize the data and information collected in Task 1 . 1 to specifically identify the placement location of the mitigation reef. This effort will include the production of a location map with the bathymetry of the selected site and adjacent areas identified , and shall include coordinate locations for the reef placement. Task 1 . 2.2 Analysis of the Possible Use of Geogrid Materials In the event that the sand thickness in the otherwise suitable area for the placement of the mitigation reef is such that excessive reef unit settling into the substrate is likely to occur and compromise the desired relief of the reef, geogrid materials will be evaluated in their use as foundation material . Task 1 . 2.3 Design and Analysis The design and analysis task will include typing and sizing of the individual units based on design water depth , design material , and spatial density of the units . A stability analysis will be performed on the mitigation reef to ensure stability of the structures as both individual units and as a whole . Construction operations including schedule , deployment procedures , lighting and flagging , delineation of transport pathways, placement timing and methods , and additional information necessary to the construction and deployment of the mitigation reef will be detailed as part of the design and analysis phase . CAWINDOWS\TEMMAmbersand Post-Construction Services Contract Amendment p6 - Reduced Scope 03-12-03.doc 4