The PERFECT PIPE for Infrastructure Challenges

As published in the Ontario Concrete Pipe Association’s Concrete Pipe Journal Winter 2017 Issue.

Municipal inflow and infiltration reduction programs across the country have changed long-term expectations regarding the sustainability and resilience of sanitary sewers.

For example, York Region and its area municipalities have committed to implementing specifications and standards for inflow and infiltration in their existing and future sanitary sewer systems. Reducing inflow and infiltration is a high priority initiative with a budget of $100 million over a 20-year period.

Inflow and infiltration reduce the capacity of the sewage systems leaving less for existing residents and future growth. When sewage is diluted by water, treatment becomes less efficient. The cost of water to residents increases because plants are required to treat a higher volume of low.

Another challenge within municipal sewage systems is microbial induced corrosion (MIC). A sanitary sewer that has a shallow gradient, with low flow velocity is an ideal environment for a slime layer to develop on the surface of the pipe below the water level. Anaerobic bacteria reduce sulphate to sulphide. Above the sewage level, the hydrogen sulphide gas is consumed by Thiobacillus, a sulfur oxidizing bacteria (SOB), which produces sulphuric acid that reacts with the exposed concrete surface causing corrosion.

To mitigate MIC and improve concrete durability, engineers reference CAN/CSA A23.1 and specify a C-XL exposure class in combination with other commercially-available admixtures and additives which may be unsubstantiated in their performance while adding cost to the production process.

A third challenge designers often face in Ontario, due to our increasingly built infrastructure resulting from continued population growth, is the need to it sanitary sewer extensions into an already crowded underground space. Subsequently, sanitary sewers often need to be installed deeper with increased joint capacity. Open cut construction is disruptive to municipalities, businesses and the public, thereby opening opportunity for microtunnelling, which has seen continuous growth as a preferred construction option.

Con Cast Pipe worked with Schlusselbauer Technology GmbH & CoKG Austria to introduce PERFECT Pipe into the Ontario market to address the inflow and infiltration, microbial induced corrosion and microtunnelling challenges.

PERFECT Pipe combines the strength and structure of reinforced concrete pipe with the chemical resistance of high density polyethylene (HDPE), and a water-tight jointing system. PERFECT Pipe is manufactured in diameters up to 1200mm. The pipe is fully-protected with an HDPE liner that demonstrates superior abrasion resistance when compared to competitive products.

The HDPE liner protects the interior concrete surface from the damaging effects associated with corrosive gases and liquids that form in the sanitary sewer system by mitigating MIC and improving the durability and life cycle resilience of the pipeline.

PERFECT Pipe has a dual jointing system that seals the liner using a thermoplastic internal connector with dual elastomeric rubber gaskets joining pipe sections. No field welding is required. PERFECT Pipe is designed as a gravity pipe for use in open cut and microtunneling applications. The 1.65mm thick liner has 900 homogenously extruded anchors per square metre. The pattern increases in density toward the thermoplastic coupler to ensure that the liner is firmly anchored at the joint. Each anchor has a pull-out strength of 250 N (56 lbs) while providing an overall pull-out strength of 0.255 N/mm^2. Self-consolidating concrete is used in the production of PERFECT Pipe because of its wetcast properties that make it highly flowable, yet stable enough to spread easily into the formwork, thereby covering the anchors and reinforcement without any mechanical consolidation.

Con Cast Pipe is manufacturing PERFECT Pipe in 600mm, 900mm and 1200mm diameters with pipe classes of 65-D, 100-D and 140-D and a standard lay length of 3.0m. This lay length is 23% longer than typical reinforced concrete pipe which in turn reduces the number of joints and opportunities for infiltration. This difference is also important for microtunneling, since the jointing process is the only time when pipe jacking is stopped. Aside from the chemical and abrasion resistance, the PERFECT Pipe also has an improved joint performance compared to traditional concrete pipe systems. PERFECT Pipe is especially suitable for specification where designers need to mitigate infiltration, exfiltration, corrosion or require deep bury sanitary sewers or micro tunneling.

Con Cast Pipe has commissioned the PERFECT Pipe manufacturing equipment at its Oakville, Ontario production facility and has added the PERFECT Pipe to its Plant Prequalification Certificate. Municipal wastewater infrastructure faces many challenges. PERFECT Pipe can be the first step in mitigating these sanitary sewer challenges by protecting pipeline assets, public health and the natural environment.