Harbor Mountain Road Design Sitka, Alaska

The Harbor Mountain Road survey had an elevation differential of approximately 2,000 vertical feet along a 4.8 mile stretch of narrow and winding one-lane road. The contract Task Order was awarded late in the season, causing difficult field conditions with waning daylight hours and impending winter weather, especially at the higher elevations. Other obstacles encountered during the fieldwork included steep terrain and dense brush.

The primary horizontal control survey consisted of establishing eight permanent monuments, complete with accessories, located at approximately 1 kilometer intervals outside of the existing road prism. Static Global Positioning System (SGPS) survey methods were used to define preliminary coordinate values for these monuments. Intermediate control was established between the primary monuments and along the route, and consisted of pairs of points that were surveyed using conventional traverse equipment and techniques. A vertical control survey was conducted using differential leveling techniques that included all primary and secondary control points. Tertiary control was set, as needed, to provide 50-foot cross-section interval coverage along the full length of the project.

The roadway contained six major switchbacks that required extended cross-section data to be collected for reroute engineering design purposes. Our surveyors identified 113 culverts and documented their physical dimensions and conditions. The inlet and outlet locations were tied into the survey. Thirteen hydro-sites were detailed to include extended profile data along each stream's natural course. Boundary research, monument locations, and survey ties were conducted to define the boundary line between the U.S. Forest Service property boundary and the City of Sitka. Planimetric ties consisted of all cultural items encountered along the road.

During the course of the survey, 10,500 data points were collected. The final deliverables consisted of 14 "E" size sheets and a comprehensive survey report.

This project required the following:

• Establishment of eight primary project control monuments and secondary control (using Third Order, Class I Survey Standards) for the purpose of gathering topographic and planimetric survey data along the route;
• Ties into existing Federal Highway Project PFH 50-1(1) Benchland Road for the datum basis of final horizontal and vertical control values;
• Ties to boundary corners defining the line between the City of Sitka and the Tongass National Forest; and
• A survey of approach roads intersecting Harbor Mountain Road.

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