The North Cascades National Park in Washington State is among the most scenic spots in the US. Also known as “America’s Alps,” the park boasts the largest concentration of glaciers and glaciated peaks in the Lower 48. The North Cascades Highway winds its way through the mountains, with a scenic climax at the spectacular hairpin turns beneath Liberty Bell peak and the Early Winter Spires.
As a major portion of the classic Cascade Loop, SR-20 is a very popular and busy highway when open in the summer and early fall. However, the loop is long, with some distance between fuel stops.
Seattle City Light operates three hydroelectric dams in the Park and adjacent recreation areas, and is working in cooperation with the Washington Department of Transportation to install recharging stations for electric cars at an existing roadside rest area near the Park entrance. The rest area, in historic Newhalem, WA, provides an opportunity for visitors to explore the fascinating company town (established in the 1920’s) while their Prius or Leaf recharges.
DTD was contracted to use HDD to install conduits for the power and fiber optics cables to service the fueling stations. An otherwise routine job, this road crossing was complicated by the geology of the area. As the last Ice Age ended, 10,000 years ago, the Skagit River filled its narrow gorge with untold tons of granite and metamorphic rock boulders, cobbles, and gravels – making for picturesque landscapes and truly difficult drilling.
DTD mobilized our Washington-based Vermeer 24×40 drill rig for the project. The initial hope was to pull a single bundle containing two, 4-inch and two, 3-inch conduits under the highway. As the drill bit squeaked and ground its way around and through the rocks underlying the highway, it was apparent that an appropriately large diameter bore could not be reamed in this material to accept the product bundle. Therefore multiple bores were completed to pull back smaller diameter product pipe.
Two, 4-inch conduits were installed within a few hours. The following day, the pilot bore for the third pullback went smoothly, inspiring confidence in the stability of the bore and relative lack of Smart Car-sized boulders at this location. The remaining two, 3-inch conduits were connected together and successfully pulled back into a single bore. The entire project required 2 1/2 days in the field, with no obstruction to traffic and an opportunity for DTD to assist Seattle City Light and WDOT in making a completely green circumnavigation of the Cascade Loop possible!
For more information on this and other DTD projects and capabilities, contact Senior Geologist, Mike Lubrecht, at [email protected].