I spent most of my life in the construction world, but not much with road construction. A local project here is repaving and upgrading the underground utilities with new manholes, cabling, etc. There is presently a company working out there doing. . .something. . .with the underground stuff and I can’t figure out what it is.
Basically, they seem to be pumping steam through the lines, using large fabric bags and various hoses. I can’t figure it out, but it’s been going on for at least a week now. See the photo below.
They are doing trenchless pipe rehabilitation of sewers (either sanitary sewers or storm sewers). The technology is called cured-in-place pipe (CIPP) lining.
It consists of inserting resin-soaked felt tubes inside the existing sewer (using the manholes for access), then inflating the bag with compressed air, and curing it with steam (or hot water, or UV light). So you end up with a new plastic pipe inside the old pipe (which may be clay tile or brick). Once cured, the new pipe is structurally sound and no longer depends on the original pipe for stability.
The big advantage is you don’t have to dig up the road to replace the sewer. You do a water jet cleaning of the sewer first, followed by CCTV inspection before and after. If there are any seriously compromised sections, you may have to do some isolated point repairs first—which is still better than digging up the whole pipeline to replace it.
I work for a public water and sewer utility, and I’m currently managing about $80 million of this work. I’m also certified in CIPP lining inspection by NASSCO.
More details of the technology here:
P.S. It’s kind of funny someone would ask a question that specifically touches on what I work on every day. As soon as I read the description and saw the photo the OP helpfully provided, I knew exactly what it was.
Similar techniques are used in rehabbing drain lines in large buildings. A soft polymer sleeve is drug through the pipe, inflated against what’s left of the existing rotten pipe, cured into rigidity, and you have shiny new smooth plastic pipe with a rotting cast-iron shell around it. All without digging up the grounds, digging under the building proper, or needing to tear out walls up and down the building to access the pipe chases.
Right, our contractors can even conduct CIPP lining of sewer laterals from the sewer main up to the house (or other building) with remotely-operated equipment.
Instead of being dragged through the host pipe, the liner is inverted and then inflated to open up into the lateral. (This inversion technique is often used with mainline sewer lining as well.)
Only 40 years old? Most of the sewer mains and sewer laterals I’m working on were installed between 1870 and 1950. These are usually clay tile, which doesn’t corrode but is very brittle and also settles, causing joint separation.
The first couple of feet of sewer lateral where it comes out of the house is often cast iron, though. It’s usually in pretty poor condition, often being half corroded away.
Note that typically the municipality is only responsible for the sewer main and the sewer lateral up to the property line. The portion of the lateral on private property is typically the responsibility of the property owner.
For residential neighborhood sewers (typically 8-inches in diameter), we simply block up the upstream manhole with an inflatable plug, then throw in a portable submersible pump that discharges via an above-ground hose into the downstream manhole. This is called a sewer bypass.
We tell the residents of the affected street (by letters and multiple flyers on their doors) to minimize their water use and don’t flush toilets or run washing machines during the 2-4 hour process. Those that ignore us may get a backup into their basement. (And we then get to pay for Servpro to clean up their basement.) This doesn’t happen all that often: maybe one backup per 500 houses.
The bypass for a large interceptor sewer (30-inch, 48-inch, or even larger) is a much more involved process, requiring multiple pumps that can bypass thousands of gallons per minute.
Sounds like our house in Portland. It was built in 1905 and while the exterior piping had been replaced, I’m pretty sure the under-slab was the original. I related here the big mess we had when the transition coupling between the old metal sewer line and the ABS failed due to poor bedding and subsidence. $20K later, they also had to dig up the entire 30 feet of ABS behind the house because it was reverse sloped, and bring it all up to code.
My house was built in 1928; the sewer line was cast iron (the portion within the house) and terra cotta segmented tile. Three years ago, a good-sized portion of the terra cotta pipe failed (in part due to invasive tree roots, as well as just age); repairs involved digging a big hole beside my house, and replacing about 30 feet of that with PVC; they then used the cured-in-place liner for the rest of the line (including under my basement, as well as the rest of the remaining terra cotta line to the street).
I now joke that I bought a new car three years back; it just so happens to be buried in my yard (as that’s about what the repairs cost). But, it all has a warranty against any further issues which will outlive me.
Most of the sewer mains and sewer laterals I’m working on were installed between 1870 and 1950. These are usually clay tile, which doesn’t corrode but is very brittle and also settles, causing joint separation.
(And we then get to pay for