Piercing tools provide less disruptive alternative to trenching
Problem: United Cable Construction, based in Ladson, South Carolina, was contracted to complete a 2-mile fiber installation project to bring additional cable and Internet service options to Mooresville, North Carolina. The project plan called for CIC feeder cable, approximately 1/2 inch in diameter, encased by a 1 1/4-inch outer conduit. Installation was specified on the street side so disruption, footprint and maintaining the integrity of the existing landscape were primary concerns.
Solution: Since the site was an established residential area and infrastructure was crowded because several utilities had already been installed, the project manager used Vermeer by McLaughlin Hole Hammer piercing tools and a stitch boring installation approach. Stitch boring calls for a series of shorter shots — less than 50 feet in length — and allows crews to locate existing utilities while self-excavating the launch pits. This process is both accurate and cost-efficient, which helps enhance overall installation productivity.
Result: The Hole Hammer was used to complete each bore. Then mule tape was installed and conduit pulled from bore pit to bore pit and “stitched” into place. In each conduit run, the fiber was installed and connected. The crew used tarps for temporary storage of spoil, cut sod for surface reinstatement and restored each pit the same day to minimize disruptions to residents. The contractor used a four-person crew to help keep labor costs in line, while achieving 400-plus feet of production, including excavation, installation and restoration, per day. 800/435-9340; www.mclaughlinunderground.com.
Island beachfront blemish-free after trenchless storm sewer upgrade
Problem: A Biscayne Bay, Florida, storm sewer upgrade required three 100-foot, 12-on-12 storm sewer runs of HDPE. Buildings stood in close proximity to the outfall pipes. The Miami Office of Capital Improvements and Transportation Program limited bidding to pipe bursting replacement. One sewer to be replaced was vitrified clay pipe; two were concrete. The varying tidal cycles and a pulling machine pit immersed in salt water rated the IPBA Class A project as an experimental technique performed under Class D conditions.
Solution: Contractor Maggolc Inc. used a HammerHead Trenchless Equipment Hydroburst HB100 100-ton pulling machine with 15-inch OD expanding head. Maggolc left one lane open around its coned-off curbside pulling pit. Residential traffic flow was not otherwise interrupted. The end of the storm sewers lay 3 feet below the sea’s surface, requiring no entrance pit. The low tide schedule limited the crew to six hours or less for a pull, one pull to a shift. HDPE in lengths of 100 feet had been fused onshore. Ends plugged, they were floated from shore to a preparation barge. An excavator aboard the barge lifted the HDPE in place for crews to connect the pipe to the expander head.
Result: Actual pipe bursting time per run was less than 30 minutes to pay out pipe and 20 minutes for pull back. Bursting runs required only 15 tons of the HB100 pulling machine’s full 100-ton capability. Restoration consisted of repair to the seawall where it had been chipped away to accommodate expansion and backfilling the working pit. 800/331-6653; www.hammerheadtrenchless.com.
Challenging conditions no match for sewer pipe system
Problem: The growing seaside community of White Rock, British Columbia, Canada, is clustered on a steep hill around a 5-mile sandy beach in Semiahmoo Bay. Over time, the sanitary and storm sewer systems grew with a mix of materials, including PVC, asbestos cement and concrete. The entire system needed replacing.
Solution: Consulting engineers decided that the PVC SDR 35 gasketed sewer pipe and fittings system from Royal Building Products was the best choice. It is lightweight, durable and easy to install. “It gave us a lot of flexibility because two PVC pipes could be laid side-by-side. Twin trenching allowed installation to be done very quickly and efficiently,” says David Chan, branch manager with Alpin & Martin Consultants. “This could not have been achieved as effectively with a thicker-walled pipe such as concrete. Thinner walls meant narrower trenches, less disruption to the community and fewer road cuts.”
Result: Given the underground surprises, PVC made design changes easier. “We were able to install several more lineal feet in a day compared to other types of products,” Chan says. “Flexibility is critical when dealing with less-than-ideal ground conditions and an older infrastructure with different materials. You need to come up with answers quickly. The ability to move things around when needed made it easier to work in and around utilities in a safe manner.” Crews installed more than 1,100 miles of storm and sanitary sewer pipe, 34 manholes and 130 service connections without any significant problems. 800/232-5690; www.royalbuildingproducts.com.
Multiple progressive reams ensure smooth installation
Problem: To meet the demands of a growing residential area, the City of Ottawa, Ontario, Canada, set out to install a 5-mile water feeder system, consisting of a 42-inch-diameter HDPE pipe. A 2,000-foot section of the bore presented a particular challenge. City planners were concerned with one of the two water crossings, which traversed a creek feeding the Ottawa River, the city’s primary water supply. The sticky clay conditions and the size of the installed utility presented a serious frac-out threat. The bore plan had to focus on methods and tooling to eliminate the possibility of drilling fluid intrusion into the waterway.
Solution: Stopping the reactive clay from swelling by maximizing cuttings flow, the bore plan called for an initial pilot hole and 16-inch pre-ream, followed by a series of progressive reams. The design team at StraightLine HDD was tapped to supply the reamer solutions. The aggressive open-bodied Reverse Radial Flow reamer was specified, in 24-, 36-, 48- and 54-inch diameters. The bidirectional design is suited for push/pull reaming, and provides ample open space and fluid delivery to deal with significant cuttings volume. For stabilization of the hole, the cutting reamers were followed by 22- and 34-inch Maxi Barrel reamers. Finally, a 54-inch Reverse Radial Flow, followed by a 46-inch Maxi Barrel was selected to handle pipe installation.
Result: Over a five-week period, the progressive reaming process — executed by pulling/pushing the StraightLine reamers — resulted in an ideal final utility installation. 800/654-3484; www.straightlinehdd.com.