Gravina Mill Access Road

Gravina Access RoadLEI completed the Gravina Mill Access Road project using DOT LiDAR, design surveying, environmental analysis, permitting, PS&E development, and construction administration for 3 miles of low-volume road re-alignment and improvements west of the Ketchikan International Airport.

LEI performed a detailed route survey of the road and structure site using a Trimble S6 Robotic Total Station to the specifications and standards provided by the DOT&PF. LEI survey crews produced over 2,000 feet of full preliminary line route survey per crew day. Primary reference and control was set along the alignment, and tied to geodetic control provided by DOT&PF. Survey crews surveyed property lines, easements, and Right-of-Way referenced to the route survey, as deemed necessary and appropriate by the research conducted by the LEI Land Surveyor and DOT&PF. Topographic data was collected at not more than a 50-foot spacing, but sufficient to adequately map terrain features and model the terrain for design.

Site surveys were conducted at all fish-bearing stream crossings and stream crossings with anticipated flows requiring a 48-inch diameter or larger pipe structure. For each site survey, LEI established control for the site tied to the control network for the route survey. Topographic data was collected on not greater than a 25-foot spacing, but sufficient to properly model the site conditions and terrain. Terrain features collected included stream thalweg, active channel width, top of bank, flood plain limits within the site, and terrain breaks within the site feature. Site surveys were also conducted at all locations requiring earth structures, such as retaining walls and large engineered fills. Streams requiring a backwater analysis had the cross sections located by a hydraulic engineer to ensure that proper modeling of the stream was achieved.


LEI used the data acquired to develop Plans, Specifications & Estimate (PS&E) output for each route/structure alternative for analysis and presentation in the Preliminary Engineering Report. The PS&E format followed DOT&PF design standards and guidelines, and met the objectives and requirements needed for the environmental analysis task in the project.

One of the Alaska DOT project management team members had the following to say about LEI’s approach on a recent project: “This project is becoming one of the most successful ‘new’ road alignments this department has ever been involved with. Your ability to field engineer the alignment is invaluable.”