The Vermeer AXIS system is a pit-launched, laser-guided trenchless installation system that uses elements of pilot tube microtunneling and horizontal directional drilling. The system offers the option of pullback pipe installation or jack boring.

During the last two years, the scenic city of Carpinteria, Calif., has undertaken a multi-phase project to relocate a 50-year-old, 6,000-foot sewer main that ran through the city's beloved Carpinteria Bluffs Nature Preserve, a destination revered for breathtaking views of the Pacific Ocean and surrounding mountains. Coastal erosion has taken a toll over the years, and the sewer main pipe has been exposed and damaged on occasion during winter storms. Additionally, increased environmental sensitivity of the preserve has made maintenance access considerably more difficult. In 2011, the Carpinteria Sanitary District opted to install a new sewer main under a roadway 700 feet north of the original main.

The final phase of the project was connecting five large commercial buildings along the bluffs to the new sewer main. The limited workspace available and environmental concerns significantly limited pipe installation options for these new lateral connections.

"Open-cut installation was not an option due to site constraints, and the required slope for the new pipe was too flat to allow for a horizontal directional drilling installation approach," said Craig Murray, P.E., general manager of the Carpinteria Sanitary District. "We were really scratching our heads. At first, the only apparent option was the use of a sewage pump station and a force main to convey the flow to the new gravity sewer within the roadway, which would have been costly and resulted in long-term O&M requirements."

Fortunately, the sanitary district was able to find a newer, more cost-effective and less-disruptive option – the Vermeer AXIS Guided Boring System coupled with CertainTeed restrained-joint PVC pipe. The Vermeer AXIS system is a pit-launched, laser-guided trenchless installation system designed for more accurate, on-grade pipe installation. Utilizing elements of pilot tube microtunneling and horizontal directional drilling, this system offers the option of pullback pipe installation, in addition to jack boring.

The sanitary district specified CertainTeed CertaFlo GreenLine restrained-joint pipe, a product often paired with the AXIS system, because of the advantages it offers in directional sewer applications. The high-impact PVC pipe features CertainTeed's Certa-Lok Integral Bell restrained-joint system and is available in 10-foot lengths, in addition to the standard 20-foot lengths. The option of a 50-percent shorter pipe length allows smaller and more economical construction pit sizes, which made the product ideal for the confined work space on the Carpinteria Bluffs. The pipe's light green color also makes it easier to see during camera inspection of sewers.

Carpinteria Sanitary District hired Tierra Contracting Inc., of Santa Barbara, Calif., as general contractor for the Carpinteria Bluffs sewer relocation project, which subcontracted the 511-foot sewer lateral installation to Pacific Boring Inc., of Caruthers, Calif.

Pacific Boring began work in spring 2012. Since this was the first time the contractor's crew had used the Vermeer AXIS system, Vermeer representatives were onsite to provide training and technical support throughout the installation. The crew excavated a center pit and made a 268-foot bore in one direction and a 243-foot bore in the opposite direction under a building's parking lot. The soil consisted mostly of sandy loam, which offered little resistance, but unanticipated intermixed rock slowed the process down at points.

A worker in a receiving pit helps positon the pipe segment to begin pullback operations.

"From a constructability standpoint, the pipe was ideal," Murray said. "The Pacific Boring crew had to work in a narrow corridor behind the building, and there was really no good access point. The shorter lengths of pipe helped keep the pits small, and the crew was able to assemble the pipe at the receiving pit as pullback continued. It was really easy to manage."

The Vermeer AXIS system also performed well throughout the project, its laser guide helping the crew meet the 0.4-percent grade requirement. The equipment also helped the project team minimize disturbance to surrounding businesses and vehicle traffic in what could easily have been a more invasive installation.

"We kept the main entrance into the building's parking lot open and were able to minimize the construction footprint so the building tenants still had space to park," Murray said.

Shorter pipe lengths (10 feet) allowed smaller pit sizes for trenchless sewer lateral pipe installation in confined spaces.

The project was completed in a week. Carpinteria Sanitary District was pleased with the outcome, as it ultimately cost less than the pump station alternative and made for a much smoother installation. Various trenchless pipe installation methods played a significant role throughout the Carpinteria Bluffs Sewer Relocation project, and the utility is now well aware of the many benefits of going trenchless.

"On this sewer relocation project, we used horizontal directional drilling to bore under a creek, jack-bored one section under a roadway, and used the Vermeer AXIS system for the final sewer lateral phase, all with positive results," Murray said. "I think we're finding that trenchless construction is more and more the right solution for us."

John Coogan is channel marketing and communications manager for CertainTeed Pipe & Foundation Group (www.certainteed.com/products/pipe).