Manning Crevice Bridge Replacement, Riggins, Idaho;


Manning Crevice Bridge is a 248-foot long one-lane suspension bridge with timber support towers crossing the Salmon River 13.5 miles from US 95. The bridge was constructed in 1936 and the current sufficiency/load rating for the bridge has continued to degrade. The project site is located in a steep, rocky section of the Salmon River Canyon. White Shield provided survey services to support conceptual and preliminary design, hydraulic studies, and floodplain analysis for the new bridge. Surveyors verified existing control on-site, tying to any control monuments near the project location, including one NGS monument, and one US Forest Service monument. A medium-resolution High Definition Scan (HDS) of the project site was performed to facilitate topographic data collection and maintain the ability to ͞mine͟ data, as needed, for future specific design areas. The HDS data captured elevations 200’ above grade to edge-of-water through the corridor to support future hydraulic modeling.

Laser scanning provides designers and end users with extremely precise, real world, as-built data thus minimizing downtime and fit up issues during construction.This view is looking at the bridge abutment and tower mounted on rock cliff near Riggins Idaho. We can collect point data on vertical rock cliffs collected from ±300’ across the river. For relative size comparison, remember that the tower is ±35 tall.


Laser scanning can capture details such as swaying cables and power lines and later determine their exact location and parabolic bend. This is a view of detail near the top of tower, suspension bridge, in medium density from a nearby scanner position.



Laser scanning can capture high detail such as bolts and tensioners and other critical structural elements of bridges. This is a view of one suspension bridge multi-cable tensioner when scanner is located close by (±50’) using a high detail scan.