The American Society of Civil Engineers’ (ASCE) Seattle Section honored Aspect’s Lake Crescent Roadway Improvement Project at their recent Local Outstanding Civil Engineering Achievement (LOCEA) Awards ceremony. The project won this year’s award for Geotechnical Engineering, recognizing Aspect’s innovative moment slab design that widened and stabilized a key stretch of Highway 101 along Lake Crescent in Olympic National Park.
The two-lane stretch of Highway 101 and its varying geologic conditions prior to moment slab construction.
Principal Geotechnical Engineer Erik Andersen walked the group of 60 people watching online through the project and how Aspect got involved. A 400-foot-long section of two-lane road on the shore of Lake Crescent was in need of a permanent solution to address ongoing instability and widen the road. The Federal Highway Administration’s Western Federal Lands Highway Division (FHWA), who have jurisdiction over this part of Highway 101, recommended the unstable shoulder fill be removed, and a mechanically stabilized earth (MSE) wall be constructed at or above the lake level.
Complex Geology + Unstable Shoreline = Great Engineering Challenge
This recommendation presented a host of challenges to an already complex site with varying geology and an unstable shoreline. Constructing the MSE wall would require blasting bedrock in some areas and constructing concrete beams in other areas where bedrock was below the lake elevation, which would be difficult to execute within the 4-hour windows they were permitted to have both lanes of the highway closed. Blasting the rock and construction near the lake would greatly disturb wildlife, fish, and the lake itself. Strider Construction, tasked with building the MSE wall, determined this concept was too difficult and risky. They turned to Aspect to develop a safer and more constructible alternative. Erik and Staff Engineer Henry N. Haselton brainstormed with Strider and FHWA to develop a moment slab design.
Rebar reinforces the moment slab that extends over the shoreline but doesn’t impact the water.
Henry and Ken Wilson from Integrity Structural Engineering joined the presentation to discuss the analysis and design for the slab. The heavily reinforced concrete slab was designed to be supported on the shore at one end and suspend (or cantilever) over the embankment. It required significantly less excavation and blasting from the site, eliminated the need for temporary shoring, and could be completed without disturbing the pristine waters of Lake Crescent. With the easier design in place, construction moved at a more predictable pace. Ultimately, work was completed three weeks earlier and saved the project over $100,000, as compared with the original MSE wall concept.
Bellingham Waterfront Project Also Honored
Aspect contributed to the success of another of the night’s honorees. Project Geologist Matthew von der Ahe provided hazardous material mitigation during construction of KPFF’s Granary Avenue and Laurel Street Project. This roadway/bike lane/sidewalk project for the City of Bellingham improved access into Waypoint Park (itself a winning project) on the former industrial site that housed the Georgia-Pacific Tissue Mill.
Photo from City of Bellingham website.
This year’s other LOCEA winners are:
Small Projects and Non-Construction Study: CSO 171 Outfall Project (HDR and team)
Transportation and Development Engineering: NE 45th Street East Approach Seismic Retrofit Project (HDR and team)
Water Resources and Environmental Engineering: Meydenbauer Bay Park Project (Anchor QEA and team)
Ports and Waterways Engineering: WWPS043 Emergency Force Main Replacement Project (Staheli Trenchless Consultants and teams)