Trenchless Technologies
“Out of sight, out of mind” is true for most people, but for SHN engineers and geologists, what is out of sight is very much in mind. Underground pipes convey water, wastewater, natural gas, and many other fluids. Underground pipes are also conduits that protect vital electrical and communications cables. Underground piping systems are ubiquitous; roads and buildings are frequently constructed on top of them, so when these pipes need maintenance or repair, how can they be accessed without damaging overlying structures?
Using various trenchless technologies, SHN engineers make old pipes new or install new pipes next to old. “Going trenchless” allows us to rehabilitate old piping and conduits with minimal ground surface disturbance, through methods such as horizontal directional drilling, cured in place pipe, slip lining (pushing or pulling a smaller pipe inside a larger one), pipe bursting, hammering, and auger boring. Sensitive environments (such as rivers, estuaries, wetlands, and other sensitive environments), and roads and structures can be left undisturbed while piping is replaced and/or installed below. SHN is one of the leaders in applying trenchless technology with smaller municipalities, keeping their limited maintenance budgets in mind. SHN engineers hold committee positions in the North American Society for Trenchless Technology (NASTT) and have been both presenters and reviewers at NASTT’s “No Dig” Show and publications.
Disaster prevention at Tillamook Bay
Drinking water lines that are suspended from bridges are vulnerable to earthquakes, floods, and other natural disasters, so under the FEMA disaster prevention program, FEMA funded the City of Bay City’s relocation of waterlines from bridge supported installations to under river installations. This project also completed a regional water system inter-tie between the City of Tillamook and Bay City. SHN’s experience with horizontal directional drilling (HDD), and our on-going relationship with the City of Bay City as the City’s Engineer of Record, contributed to this project’s success, which included a “fast-track” schedule for the inter-tie phase of the project.
SHN provided engineering design, surveying, geotechnical services, “frac-out” analyses, bidding support, permitting, and construction inspection services to the City. We submitted a Joint Permit Application on the City’s behalf to the U.S. Army Corps of Engineers, under a Section 10 nationwide permit, and to the Oregon Division of State Lands for a fill/removal permit. All of the crossings were permitted for work within jurisdictional wetlands; HDD construction was key to obtaining these permits by avoiding more significant impacts to these local waterways.
Installation of a new power cable under Gig Harbor, Washington
In parts of the Pacific Northwest, aging infrastructure includes underwater power cables as well as roads and bridges. After a major cable failure, Peninsula Light Company (“PenLight”) decided that its primary power supply cable serving Fox Island, which was last installed in the 1970s, needed to be replaced. In August 2010, PenLight contracted with SHN to “fast-track design” a new cable crossing, assist with planning and environmental resource applications, provide bid support services, and provide construction support services for the new installation. SHN initiated a design that incorporated horizontal directional drilling (HDD) of almost 4,000 feet of casing and a bundle of cable-carrying conduit. In less than three months, SHN prepared contract documents that allowed PenLight to procure the construction services of the HDD Company Inc. of Cameron Park, California.
SHN assisted in obtaining the final permit approvals from the State of Washington, Pierce County, and the US Army Corps of Engineers. The HDD Company mobilized on site and began installing a new power supply to the residents of Fox Island. Drilling of the Hale Passage Crossing began in March 2011, and was completed in 8 weeks. By the end of May 2011, SHN and HDD installed the power supply cables under Puget Sound, and in early June 2011, the cables were terminated in electrical utility vaults; the system was energized within a week of the peak electrical demand anticipated for the July 4th celebration on Fox Island.
Installation of a water main under the North Umpqua River
SHN designed the installation of a 22-inch water main under the North Umpqua River for the Umpqua Basin Water Association (UBWA), using horizontal directional drilling techniques. The existing water line was suspended from an existing bridge, but reconstruction of the bridge required that the pipeline be relocated. The directional drilling provided an environmentally safe and long lasting pipeline installation that SHN and the Water Association considered superior to conventional bridge crossings.
SHN worked closely with UBWA and the Contractor to ensure the success of this design build project. SHN applied for the US Army Corps of Engineers permit, provided the design and design drawings for the launch site and river crossing, wrote a “good practices” specification for the contractor, and prepared the design of a retaining wall that was needed at the launch site near the water treatment plant.
