Microtunneling is becoming one of the most common forms of underground construction to help mitigate disruption of the area where the project is taking place.
And this year Press-Seal’s customer, Northern Concrete Pipe, was able to assist in achieving a new U.S. record for a single bore of pipe that stretches nearly ¾ of a mile under Lake Erie.
Why Northern Concrete Pipe Was Needed for Microtunneling Project
Microtunneling in particular is a very tight niche and knowledge about pipe jacking amongst owners and engineers is limited at best. Due to the critical nature of each pipe segment along the line, concrete pipe is well suited for these types of projects.
Open-cut or trenching-type construction using concrete pipe has been common for decades, but today’s microtunneling contractors need jacking pipe with the end use in mind. Pipes used in jacking need additional strength, joints that allow for deflection and yes, even pipe gaskets that prevent infiltration and exfiltration.
Although this sounds complicated, there are plenty of concrete pipe manufacturer’s in north America that make pipe segments meeting or exceeding the expectations of microtunneling contractors. Some of these expectations quoted by contractors are:
• Rigidity – point load obstacles during pipe jacking require a rigid characteristic that you find in RCP
• Joint design – keeping the annular space with gaskets prevents sand and soil from increasing friction
• Axial loads – microtunneling contractors might need to apply extra force along the axial line to keep the string of pipes moving in the proper direction
Northern Concrete Pipe is more than capable of delivering these expectations of high-quality jacking pipe and that’s why they were chosen for the Painesville Water Treatment plant project.
How the Record was Broken
It all took place in Painesville Ohio on a $15 million project to improve the facility’s raw water intake by building a second 36-inch intake pipe connecting Lake Erie to the treatment plant.
For over 50-years the intake system was 1,000 feet from shore and only 8-feet below the water surface. This shallow depth along with harmful algae blooms that occurred in 2015 forced the city of Painesville to take action. So they took advantage of an interest free loan that the Ohio EPA was offering for communities dealing with these sort of problems.
The plant has been a lifeline to the Painesville area for well over a century, but the conditions of the lake have always forced the Painesville Water Treatment facility to make improvements. They treat over 3-million gallons of water a day for about 25,000 customers in and around Painesville.
The new intake line required RCP to be pushed out nearly 4,000-ft under the lake using a Herrenknecht AVN1500 microtunneling machine and Northern Concrete Pipe was chosen as the pipe supplier.
After boring was complete, the line stretched 3,947-ft using pipe manufactured by Northern Concrete Pipe that included:
• 10’ long pieces of pipe
• 60” C-wall
• 395 sticks of RCP
The previous record of 3,000-ft was set in 2008 in Portland Oregon for a new CSO program.
As mentioned earlier, the joint design required in microtunneling projects is critical to the success of the push and within those joints it’s also important that the correct pipe gasket’s are utilized.
That’s where Press-Seal comes into the picture for the project. We supplied:
• 3/4” Isoprene O-Ring gaskets
• 1-1/8” Isoprene O-Ring gaskets used for the intermediate jacking stations
And although there are common standards for open-cut construction, the microtunneling market is working on writing new specifications and/or standards related to concrete pipe jacking. Some of these potentially new microtunneling specifications could easily be written based off of current standards such as:
• ASTM C76-19: “Standard Specification for Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe”
• ASTM C361-16: “Standard Specification for Reinforced Concrete Low-Head Pressure Pipe.”
ASCE has even published a book called “Standard Construction Guidelines for Microtunneling.”
As more and more contractors are practicing the microtunneling process, they will be looking to be successful using concrete pipes such as those manufactured by Northern Concrete Pipe as well as gaskets manufactured by Press-Seal Corporation.