July 2012, Vol. 67, No. 7
Features
Ensuring A Successful ‘Burst Day’
Pipe bursting is a well-established and proven method for replacement of an existing underground utility throughout the world. The growth of pipe bursting as a method of choice is directly related to the success of installations and the comfort level utility system owners have with the technology.
Not unlike any other form of construction, the result of a project and its overall success is highly dependent on the field crews actually conducting the work. This article will share some tips and experiences that will help give those new to trenchless construction and specifically, pipe bursting, a perspective on how success can be driven in the field.
In pipe bursting construction, the success of the project is often realized, or not, on “burst day” — the day that new pipe is installed. But there are many aspects of a project before, during and after that will impact the effectiveness of the resources on a pipe bursting project.
Any successful project will include a detailed plan that has been communicated to all of the project stakeholders and decision makers. The project plan for pipe bursting should clearly define such items as traffic control plans, laydown of equipment, laydown of pipe materials, location and size of pits, flow by-pass or temporary service lines, sequence of events and a time-driven schedule for those events. This should be a living document that is used on a daily basis by not only the project manager and contract coordinator, but by the crews in the field actually performing the work.
Traffic control
A traffic control plan must, in most cases, be submitted to the owner for approval and for pipe bursting will need to include some very specific items that will make the day in the field go much smoother and limit disruption or confusion. In most cases of continuous pipe installation with a product like thermally fused HDPE or PVC pipe, jobsite impact will be approximately two times the length of the pipe to be replaced as the new pipe is pre-fused and strung in place as it is pulled into the ground via an insertion pit. For a typical sanitary sewer installation, that length will often be manhole-to-manhole and the pipe will extend above ground while it is being installed. Some items often overlooked are how residents will access their driveways or business entrances, all of which can be properly planned to limit disruption, with the field crews understanding of the plan and being able to communicate that plan in real time.
Equipment laydown is typically predetermined in the contract documents. However, field crews often need areas along a jobsite or public street to store items like pipe and equipment. Clear communication between the owner, contractor and general public will help promote goodwill and prevent delays caused by equipment needing to be moved or unnecessary disruptions to the public. Keeping access to emergency equipment like fire hydrants is essential and prior notification to the local fire or police should be standard even if not clearly identified in the contract.
Pipe laydown with a pipe bursting project is an area where confusion can exist if the entire project team does not clearly understand the process and the sequence of events during a pipe burst. Most pipe bursting utilizes continuously fused pipes made of either HDPE or PVC which are fused in the field to form one long pipe that is installed without joints. These pipes can often be fused prior to “burst day” and staged alongside a road or in a nearby vacant lot and pulled into place the day of the pipe burst. It is essential that everyone understand the potential impacts of traffic, residents and business. In most cases, an experienced crew can fuse, store and move into place a pipe with little or no impact to the general public and limit the impact during installation. Segmental pipes are used in areas where the pipe cannot be strung into place in a continuous length and are stored at the side of the insertion pit and launched through a “cartridge” style installation.
Pits
Although pipe bursting is a trenchless method, it does require excavated pits to insert and (some cases) receive the pipe, as well as to reinstate service connections like sewer laterals or water services. The location of these pits should be configured in a way that minimizes disruption and maximizes the benefits of a trenchless technology. In many cases the location of all pits will be predetermined prior to construction between the owner and the contractor, these locations should be clearly identified in the construction plan including location, size and laydown area needed near the pit for support equipment. It is common to move or shift a pit during construction. This is a decision that must be made in real time in the field by the construction manager, along with communication measures in place to allow that to happen without unnecessary delay or impact. Typical reasons for moving a pit during construction would be adjacent utilities being improperly marked or conflicts not originally in the project plan.
Above ground by-pass of sewer flows or temporary water service lines should be established prior to the installation of the new pipe. The configuration of the temporary piping should not interfere with pipe bursting activities and be able to handle any anticipated peaks in flow that the system may experience. The operation of the temporary system is essential to providing reliable service during construction and in turn keeping the residents and businesses affected by the construction happy (or as happy as they can be during a construction project). Pipe bursting has the ability to install new pipe at a rate much faster than traditional open-cut construction so the duration of temporary lines is often dramatically reduced.
A clear schedule with a defined sequence of events is one of the best ways to manage the expectations of a pipe bursting project and to communicate the steps required to execute a successful installation to all stakeholders. Utility system owners that are well versed in pipe bursting and other trenchless methods often understand clearly what a project will look like whereas utility owners or engineers with little hands-on experience with pipe bursting do not understand all the steps that occur and are critical to the project. Although a daily project schedule should be a part of all construction activities, it is especially essential to burst day.
It is important to make sure everyone involved in a project understands the process and what it looks and feels like. A field crew with experience will protect the area they are working in and actively drive the end product — which is a new pipe in the ground to serve the public for many years.
Coming in August: Dealing with the unexpected – what to do when things don’t go as planned.
FOR MORE INFORMATION:
IPBA (NASSCO), (410) 486-3500, www.nassco.org
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