Contract Amount: $10.6 Million Owner: Ogden City Completed in 2013
The Ogden Canyon Waterline Project was initiated to rehabilitate or replace an existing 24” steel waterline put in over one hundred years ago between the water treatment facility at the base of Pineview Reservoir to the city water storage lagoons on the hillside above the city of Ogden. Over 23,000 feet of new 24” waterline was installed. The CM/GC contracting method was chosen by the city as the method of choice to allow the city to work with a contractor to help solve some of the difficult constructability issues facing this project.
There are two main waterlines that feed the city of Ogden, both of which come down Ogden Canyon from Pineview Reservoir. These two waterlines are the lifeblood of the city and a failure on either water line would have resulted in severe water shortages for the residents. For this reason it was determined to only complete the construction work in the winter and spring months when water demand was greatly reduced and the city could shut down the 24” waterline.
A major challenge was to maintain traffic through the canyon throughout construction and minimize impact to the traveling public to the extent possible. Much of the work was completed at nighttime when traffic flows were the lowest, traffic signals and pilot cars were used to help clear traffic around the construction area and the pipeline was completed in phases to minimize areas of the canyon impacted.
Other challenges on the project included working in the extreme winter conditions of the canyon. Record low temperatures in February combined with night time work and canyon winds made for difficult work for the crews. A temporary water system was installed to provide water throughout construction to over 200 homes for the six months required for the pipeline replacement. Rock was encountered throughout the project which required trackhoe mounted jackhammers to break and remove the rock from the pipe zone. The limited work areas on this narrow canyon road required additional work to remove snow, place temporary asphalt through the winter and careful scheduling the road crossing affecting traffic.
The final construction challenge came at the mouth of Ogden Canyon to take the waterline from the highway in the bottom of the canyon up the steep mountainside to the upper bench where the city storage reservoirs were located. The original pipeline was installed on a small mountain trail inaccessible by modern construction equipment and the old waterline was in fact was tunneled through several rock outcroppings. To make matters worse, the original pipeline trail was directly above and parallel to the existing highway creating a hazardous situation to do the earthwork required for the pipe replacement. The team was determined to find a new route for the waterline that would allow the highway to remain open during the new installation. Unfortunately there was no good location, between the highway, river and steep hillside.
After careful considering several locations, a new alignment was finally agreed upon although this location still had considerable construction challenges. The slope of the hillside was 77% grade in some locations with rock removal required, no staging area at the bottom and a small 10’ wide trail at the top from which to bring in the equipment.
Through use of a variety of creative construction techniques crews were able to complete this segment. The existing trail on top was widened to be able to bring in equipment from the top; a trackhoe was lowered down the upper hillside using a winch Cat dozer to a shelf on mid mountain where crew cut a new trail across the hillside and there again the pipeline turned downhill for the lower vertical section. To install pipe on the lower section crews built a temporary retaining wall along the highway and built a large earth ramp to get the equipment high enough to reach between the highway and the hillside shelf.
After the new pipe alignment had been pioneered, the pipe was hoisted from the highway, assembled and winched into place. Polyurethane foam was sprayed around the pipe to both bed the pipe and as a trench cutoff to prevent water from washing out the soil around the pipeline causing a future failure.