digger242j
Administrator
...Since there's recently been another one going on. This one's sorta the same, but different.
We had a little job a couple of weeks ago, at one of our local municipality's sewage treatment plant. It involved repairing a small sinkhole in a paved area.
There's a 3 inch "plant water" line, that leads from the one building to the tanks that process the raw sewage. As I understand it, water is occasionally used to wash down some of the equipment, and it doesn't need to be drinking water, so water that's already been through the treatment process is used. A pipe runs underground, and then at several points tees branch off and go up the side of the tanks. Since we have cold winters here, those lines needs to be drained in freezing weather. The drain can't just run to daylight, because the water is technically not ready to be discharged from the plant yet, so was a 3" x1" tee, with a curb stop attached, and the water was allowed to drain into the gravel bed around a larger (18" ductile iron), raw sewage pipe below.
The sinkhole apparently happened because either somebody left the line pressurized when they opened the drain, or the pipe broke off at the tee, which allowed an excessive amount of water to run. When we dug it up, it was broken. The 3" valve that controls this setup is right in front of the tee.
The first part of the job involved installing a new valve, inside the building, so that we could isolate the problem area from the rest of the system, which needed to remain active. That was pretty simple. The access was easy, and we cut out a section of pipe, installed two flanged ends, and slipped the new valve in between them, and bolted it all up. We opened the valve to test for leaks, and then shut it again so that we could proceed to the next part, which was digging up the problem area and figuring out a solution.
First pic shows the site:
On edit: ignore the time stamp on any of the pics. I took them with a digital camera, which had been sitting with the batteries removed for quite some time, and didn't realize the date needed to be reset.
We had a little job a couple of weeks ago, at one of our local municipality's sewage treatment plant. It involved repairing a small sinkhole in a paved area.
There's a 3 inch "plant water" line, that leads from the one building to the tanks that process the raw sewage. As I understand it, water is occasionally used to wash down some of the equipment, and it doesn't need to be drinking water, so water that's already been through the treatment process is used. A pipe runs underground, and then at several points tees branch off and go up the side of the tanks. Since we have cold winters here, those lines needs to be drained in freezing weather. The drain can't just run to daylight, because the water is technically not ready to be discharged from the plant yet, so was a 3" x1" tee, with a curb stop attached, and the water was allowed to drain into the gravel bed around a larger (18" ductile iron), raw sewage pipe below.
The sinkhole apparently happened because either somebody left the line pressurized when they opened the drain, or the pipe broke off at the tee, which allowed an excessive amount of water to run. When we dug it up, it was broken. The 3" valve that controls this setup is right in front of the tee.
The first part of the job involved installing a new valve, inside the building, so that we could isolate the problem area from the rest of the system, which needed to remain active. That was pretty simple. The access was easy, and we cut out a section of pipe, installed two flanged ends, and slipped the new valve in between them, and bolted it all up. We opened the valve to test for leaks, and then shut it again so that we could proceed to the next part, which was digging up the problem area and figuring out a solution.
First pic shows the site:
On edit: ignore the time stamp on any of the pics. I took them with a digital camera, which had been sitting with the batteries removed for quite some time, and didn't realize the date needed to be reset.
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