Four Topographic Levee Surveys for FEMA Certification

Client—Multnomah County Drainage Districts, Oregon

Gibbs & Olson was hired by four drainage districts in Multnomah County to perform topographic surveying and ownership/easement research for a total of 28 miles of Columbia River levee from Hayden Island to the mouth of the Sandy River. Services performed included:

Collecting and researching all existing surveys and deeds of properties abutting the levees to determine existing property monumentation;

Collecting and researching ownership and easement information to determine the limits of each District’s ownership and easements in relation to the physical levee location;

Gathering existing levee cross-sections to a distance of 30 feet from the levee toe on the landward side to either the edge of water or to 30 feet from the levee toe on the river side at a typical interval of 150 feet;

Preparing final AutoCAD drawing files to include surface model with 1 foot contour lines, field located corners of record, levee monuments and easement or right-of-way limits. The maps produced included property and easement lines of the levee and all structure locations.