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DRAFT WILLAMETTE RIVER GREENWAY DESIGN PLAN APPENDIX A. FIELD INVESTIGATION OVERVIEW This section discusses the methodology used to conduct the field investigation, the findings from the investigation, and the process used to establish mapped Willamette River top of bank JOB) and Willamette Greenway setback (WGS) lines as components of the updated regulations. METHODOLOGY City staff estimated the Willamette River TOB in GIS using 2-foot contours, slope, and hillshade layer sets derived from the 2009 LiDAR data. The City provided the GIS dataset to Cameron McCarthy for use on the project and consultants conducted a field investigation on October 12, 2021, to test the accuracy of the mapped Willamette River TOB line. City and consultants agreed upon six test sites for the field investigation. Test sites were labeled with a directional identifier (W, E) based which side of the river the site was located, and nearest street name or geographical feature: • W1 Hatten • W2 Briarcliff • W3 Millrace • E1 Riverplace • E2 Valley River Center (VRC) • E3 Frohnmeyer Exhibit A to the Top of Bank Determination contains a map of the full extent of the Willamette Greenway boundary within Eugene and the location six test sites, as well as field map enlargements of each test site. Consultants collected GPS survey points in the field using a Trimble Geo7x centimeter kit comprised of a handheld rangefinder module connected to a Zephyr mobile antenna mounted to the top of a 6-foot tall surveyor's range pole. At least 12 Global Navigation Satellite System (GNSS) satellites were acquired for use by the handheld GPS unit prior to point collection. This method of collection provides a sub-centimeter radius of accuracy. The high level of accuracy of both LiDAR data and field collected GPS data is designed to rule out data collection and digital processing as contributing factors of error. Consultants collected field GPS points within the six sample sites along the Willamette River. Point Feature Data collected and filed on the GPS handheld was converted to ESRI shapefile format using the handheld internal Windows OS and Trimble's TerraSync application standard process. GIS compatible shapefiles (points) were then transferred to a memory card for processing in Autodesk Civil 3D 2021. GPS field point data was overlayed in Civil 3D with the mapped TOB line, previously generated using LiDAR data. The TOB line and field-collected points were then assessed at each test site for consistency. Where less than 1 meter of difference occurred on average, the mapped TOB line from LIDAR data is considered to be accurate to field conditions. For test sites where field-collected data points varied from the mapped TOB line greater than 1 meter of difference, the mapped TOB line was considered not accurate to field conditions and modified based on field conditions and GPS field point data. Primary methods used for M WILLAMETTE RIVER GREENWAY CODE AMENDMENTS I CITY OF EUGENE 38