AXIS system used to install gravity flow sewer Laser-guided boring technology capable of pinpoint, on-grade accuracy

Transcription

1 AXIS system used to install gravity flow sewer Laser-guided boring technology capable of pinpoint, on-grade accuracy The City of Kitchener, Ontario, Canada, was in a dilemma. After repeated breakdowns and a series of attempts to repair an aging sanitary pump station, City Operations officials finally concluded the station had reached the end of its service life. Maintenance costs were draining the city s budget and something needed to be done. MTE Consultants Inc., a civil, environmental and structural engineering consulting firm, also based in Kitchener, was hired to help develop a solution. In a collaborative effort, MTE s design team, including Caroline Amyot, designer and contract administrator and Kevin Mick, design and approval engineer, along with Bryan Bishop, construction project manager for the City of Kitchener, to develop a plan for upgrading or replacing the failing pumping station. After collecting and analyzing extensive amounts of data and preparing several alternative potential solutions, Amyot and Mick concluded that eliminating the pump station and replacing it with a gravity flow sewer was the preferred solution. Going gravity The final recommendation was to decommission and remove the pump station and install a gravity flow sanitary sewer line through a forested area to divert the sewage that was passing through the pump station and connect it to an existing sanitary sewer at the other end. The plan design proposed the new sewer be installed in two sections. The first section, approximately 755 feet (230 m), involved a residential subdivision with an environmentally sensitive area that included a creek crossing, and was to be installed using horizontal directional drilling (HDD). The second 105-foot (32 m) section included a slight deflection from a proposed manhole at the downstream end to tie in to the existing sanitary sewer in a neighboring residential subdivision. This section was to be installed using open-cut methods. According to Bishop, the proposed route would not have been possible had it not been for trenchless technology. The trenchless technology available today didn t exist back in the days when the pump station was built, Bishop explains, so that wasn t an option at that time. Fortunately we were able to chart a course for an

2 underground gravity flow sewer to retire the pump station that will ultimately save the city a lot of money, not to mention frustration. It wouldn t have been possible without HDD. Jason Kottelenberg, contract manager with AVERTEX Utility Solutions Inc., based in Orangeville, Ontario, Canada, was among the many contractors who reviewed the Tender. After analyzing the soil conditions they would face in the second section, he knew there would be challenges with excavating. The soil profile consisted of loose fill, sand and peat soils on top of hard clay till, Kottelenberg explained, and the water table was perched well above the proposed sewer line and would have been difficult using open-cut. That s not to say that it couldn t have been done, but we viewed this as an opportunity to give our new AXIS boring system a try. The AXIS guided boring system, developed by Vermeer, is a pit-launched trenchless installation method designed to achieve pinpoint, on-grade accuracy while eliminating some of the difficult steps associated with other installation techniques. The system has the capability to install a wide range of product at any grade with a range of materials and diameters. Last fall, AVERTEX became the first contractor in North America to add the AXIS system to their fleet of equipment. Kottelenberg presented his idea to Jack Kottelenberg, AVERTEX president /CEO and Andy Blokker, vice president /COO, for input. After receiving an enthusiastic thumbs-up from Jack and Andy, Kottelenberg initiated bore plan designs incorporating use of the AXIS system. When the plans were completed, Kottelenberg felt certain the AXIS system would work and the AVERTEX team got busy preparing their bid. Changing things up After AVERTEX was awarded the project, they presented proposed changes to the design at the initial pre-construction meeting which included completing the second section using the AXIS guided boring system an approach that would avoid open-cut excavation through the less-than-desirable soil conditions. Although not familiar with the AXIS technology, Bishop and Amyot were receptive. AVERTEX proposed using the AXIS system for a section we d specified as open-cut and actually streamlined the installation by eliminating some excavation that ultimately saved us money, Bishop says. Even though we weren t familiar with the technology we didn t have an objection because it was welldesigned, and frankly, the city really didn t have anything to risk. It ended up working out very well. The original design specified that the first section connect through two manholes. Installation of a drop structure was required at the second manhole. The first manhole was to be installed at the final

3 connection point to the existing sanitary sewer. The second manhole, located approximately 62 feet (19 m) downstream from the first, was proposed to accommodate a grade and alignment change so the new line would tie into the existing sewer at a right angle. The AVERTEX plan called for a more direct route. With only a slight deviation in the angle proposed to complete the first section, the AVERTEX approach called for bypassing the second manhole and aligning the shot directly to the first, in essence eliminating a connection point and a lot of additional excavation and work. This plan required maintaining a 1- percent grade for the first 656 feet (200 m) of the bore and transitioning to 6 percent over the final 100 feet (30 m) to obtain the required grade at tie-in point of the existing sewer. AVERTEX used the Vermeer D100x120 Series II Navigator for the first section through the environmentally sensitive area and beneath the creek. We like to use the 100,000-pound (45,359.2 kg) machine for grade work, Blokker says. It drills down stiffer, runs a really straight bore and maintains the line and grade really well for long bores. It also limits the amount of pre-reaming we have to do. We knew things might get a bit dicey at the creek bed, Kottelenberg said. We only had about 5 feet (1.5 m) of cover to work with under the creek which is obviously a concern when directional drilling. And the soils in the area were not favorable. But we got it to work and it allowed for a shallower depth (15 feet; 4.5 m) on the end connection that eliminated a lot of excavation. Once underneath the creek the pitch was increased and the bore continued on to the existing sanitary sewer. Bypassing the second manhole allowed for a more shallow connecting point and eliminated some excavation near the creek. Once the initial bore was complete, the 10-inch (250 mm) HDPE DR II sanitary sewer was pulled back through and connected. A 7-inch (177.8 mm) bit was used to complete the initial bore followed by a 12-inch (304.8 mm) pre-ream. With the bore complete, the 10-inch (250 mm) sewer line was pulled back through using a 16-inch (406 mm) reamer and connected to the manhole. AXIS takes lead down the home stretch With the first and longest section now completed, the AVERTEX team prepared to tackle the final phase. The course included a slight deviation necessary to effectively target the end connection. A 10- by 15-foot (3 by 4.6 m) launch pit had been excavated to position the components of the AXIS system for the home stretch.

4 With all the components securely in place, the laser was positioned at the 1 percent grade required to meet the final connection and the camera positioned to align with the target guide. Here s how the system works: At the front of the drill head, only the cutter bit and center drive shaft rotate as the drill head and accompanying casing advance through the bore the outer section remains stationary. If the laser dot is centered within the cross hairs of the target, the drill head is on course. Any necessary adjustments are made by the operator who monitors the images sent from the camera to the operator console. Spoil is extracted simultaneously with the assistance of a high-power vacuum and diverted to a vacuum tank eliminating the need for hauling spoil away from the jobsite. Upon completing the 105-foot (32 m) bore, the AXIS system components were removed from the pit and the sewer line pushed back through by hand and connected. No additional external excavation was necessary at the existing manhole. Outside of encountering a pesky rock positioned dead center in the drill path, we completed the AXIS bore without a hitch, Kottelenberg says. Fortunately the rock was located toward the end of the bore and eventually came out ahead of the drill in the manhole. It took some constant repositioning to keep the shot on-line and on-grade, but outside of getting the better of the drill bit, we hit our target dead center, made the connection and finished the job. A good day Working with the City of Kitchener and MTE was a rewarding experience, Kottelenberg says. They are a very progressive, forward-thinking municipality and always stood behind us. They got involved and took interest in how the project was coming along and were actually intrigued with the AXIS technology. I would guess 30 to 40 people stopped by the site to check in and most walked away with raised eyebrows because of how impressed they were. Now that s what I call a good day. The AXIS advantage As more cities and municipalities commit increased resources to repair and upgrade outdated and crumbling infrastructures, the number of water and sewer projects is expected to increase substantially. Many of the projects will be required to be placed precisely on-grade. While some of the current trenchless methods have the ability to achieve the accuracy these projects mandate, they lack the productivity needed to compete with open-cut methods. AVERTEX Utility Solutions Inc., based in Orangeville, Ontario, was the first contractor in North America to purchase the AXIS guided boring system developed by Vermeer. The company specializes in

5 trenchless utility construction and network installation services across a wide range of markets and a recognized leader in the adoption of trenchless technologies. Co-founder, president and CEO, Jack Kottelenberg, explains the rationale behind the purchase. The accuracy, Kottelenberg says. Accuracy is No. 1. We know trenchless pretty well and we also know open-cut fairly well and each has its own place and application. But before the AXIS system was developed there wasn t a trenchless method with the capability to accomplish the pinpoint accuracy required for jobs that were specified at 1 percent grade or less. Open-cut was the only option. We walked away from a lot of jobs that required 0.5 percent pitch or less because we didn t want to assume the risk. Not anymore. The AXIS guided boring system is designed to install 10- to 14-inch (25.4 to 35.6 cm) pipe at lengths up to 350 feet (106.7 m), and can maintain grades of less than 0.5 percent. Basic components of the system include power pack, rack, vacuum pump and storage tank. Not only is the system capable of maintaining a strict tolerance of accuracy, it s also flexible. Because of the flexibility of the four major AXIS system components, various set-up configurations can be used to adjust the machine s footprint based on jobsite and transport logistics, and it can install clay, steel, HDPE and PVC pipe. Large-scale projects are also possible for contractors operating the AXIS system with the ability to install pipe up to 350 feet (106.7 m) in length. In varying soil conditions, operators can also change cutter bits mid-installation. AXIS should not be viewed as a competitor to HDD, but rather a complement to enhancing trenchless technology and capabilities, Kottelenberg says. It doesn t have a fit for every trenchless job, but certainly fulfills a niche that will allow us to pursue jobs that we would likely have not considered in the past. We believe this system will allow us to be very competitive with open-cut installation, especially at greater depth or where there is hard-surface and imported backfill requirements. We view the addition of the AXIS system to our equipment fleet as an investment in helping grow our business. It s another tool in the cabinet that gives us a competitive edge by allowing us to compete for more jobs.