While the benefits of cured-in-place-pipe (CIPP) liners have been well-documented throughout the world since the early 1970s, it is interesting to note that innovation continues to occur in the field, allowing boundaries to be pushed. These innovations can result in significant cost savings to clients, as well as significant benefits for the environment and the general public.
This was certainly the case on two recent sewer rehabilitation projects completed by Insituform.
Project 1
The first project required the company to undertake what appeared to be a relatively simple project – the structural lining of a
225 mm sewer main. However, upon arrival on the site, the lining crew was surprised to find that the pipe was crossing beneath a small natural creek within a reserve (Refer photo 1). They were further surprised by the fact that the top of the pipe was exposed and clearly visible in the shallow creek.
Following normal procedure, the pipe was internally inspected using a CCTV camera prior to lining. This showed a significant number of structural defects in the pipe at the exposed location beneath the creek. These defects were allowing a significant amount of infiltration into the pipe and the crew quickly determined that the pipe section was under threat of imminent collapse, which would lead to a sewage spill into the creek.
The crew immediately plugged the incoming upstream flows and commenced by-passing flows to eliminate the risk of contamination to the creek. They then sought advice from Insituform’s engineering team in regards to repairing the pipe. After careful consideration, it was determined that pipe could be lined by following some specially-developed procedures. This needed to happen quickly to avoid the risk of the pipe collapsing completely.
The liner was able to be air-inverted and steam-cured within a few hours, even though the pipe was in saturated ground with high levels of infiltration. As anticipated, the damaged pipe section in the creek collapsed during the lining process, however this no longer mattered as the new structural liner was supporting the pipe (Refer photo 2). The outcome for the environment would have been very different had these works been delayed by just a few days.
Project 2
The second project called for the lining of a severely deteriorated 150 mm sewer pipe in a sensitive urban environment.
Following initial CCTV inspection, it was discovered that a section of the pipe was under severe distress, with the entire top section missing and large stones about to fall into the pipe, which would have blocked it completely (Refer photo 3). This type of defect would typically be repaired prior to lining by carrying out a localised civil repair. The line also had a bend in it which is very uncommon in this size sewer.
However, when the defect was marked above ground, it was found to be located 2 m below the toe of a 2 m high sandstone retaining wall with an elevated property block above it (Refer photo 4). Carrying out a civil repair would have lead to significant disruption and damage to both properties, as well as significant risk to the civil crew carrying out the works. After careful consideration and site investigation, it was determined that the pipe could be lined following some initial internal robotic preparation works.
The lining was then completed using Insituform’s revolutionary iPlus Infusion CIPP system, a pull-in/inflate and steam cure structural liner. The lining was successfully installed within a few hours avoiding the significant disruption and risk to property which would have been caused by a civil repair. It is envisaged that the civil repair could have cost up to $A100,000 to complete.
Both projects demonstrate the significant contributions of trenchless pipeline rehabilitation to the protection of the environment, protection of property, reduced disruption to the public, and the saving of public funds.
In addition, the projects show new innovation in the field of CIPP lining which some Australian clients may not have been aware of previously.