Nothing brings folks together Part II - Sewer drainage

Nothing brings folks together like sewage running 30' under the roads.

Seriously - it's great stuff. Your remains of the day sail away - traversing mystical terrains - off to a better, less in your face kinda places. Places where it's ok to be a stinker. Well it isn't entirely magic. A lot of it happens because people work hard to make it happen. As discussed previously - underground sewer systems have existed for thousands of years - and it beats many alternatives such as caca en la calle - spanish for "The bathroom is any and everywhere" or "Welcome to Tijuana." Is it a great solution? No. From far below it blows on high. It costs millions of dollars to install these systems, and at the end of the analysis you're losing all of that potentially valuable organic fertilizer. The Aztecs recognized this and were keen to collect all of the stuff and sell it back to the population as fertilizer....

Oh well. Maybe one day. In the mean time we're making certain that the stuff goes underground and arrives safely to a central destination.

Sewer lines are the most difficult lines to set - the tests are rigorous to ensure a proper seal on every section, pressure and vacuum tests are basic along with a host of other tests. Our recent work led us almost 30' below the earth to lower an existing sewer line 2/10s of a foot - roughly 2.5 inches.

Technical Specs
All lines are required to pass a ~5-10 minute pressure test. 10 psi is applied inside the line using a flowthrough plug on one end and a solid plug on the other.

The manhole must pass a vacuum test of -10 bars Hg for one minute without dropping a pound

Mandrel test - all the PVC must have a mandrel sent through to ensure that no warpage has occurred during the backfilling of the ditch

How to set a sewer manhole

Setting manholes is an old tradition beginning in the Indus Valley almost 2000 BCE. Many Roman manhole covers still exist with the SPQR notation on them. When the European expansionists arrived in the Americas they were amazed to see an Aztec sewer system vastly superior to their own (ie throwing it in the streets and bringing about the great plagues).

Today we set manhole covers over the structures set in the ground to allow access should something go wrong. Whereas storm sewers are unlikely to carry filth and foulness, it is assumed that all sorts of nastiness may pass through a sewer line, and thus the porosity of the system must be maintained to a minimum. In most cases we are expected to achieve ~4psi during a smoke test of the system. This ensures that there are no major leaks where said nastiness may pass through the pipes and into the ground water.

Setting the covers is an essential part of the test. Not that the stuff in the pipes is likely to rise up that high, rather that it's a common point of failure and simple enough to fix in a few simple steps.

1) Clean the surface up nice 'n purty.

2) Slap some tar on there - we like Clipper Ship tar - it's swell.

3) Flipper over and check the level - you may need to slope it to work with the existing asphalt - when all else fails use your brain.

4) Mix up some mud. We like to blend 50% non-shrink grout (red bag) + 50% sand and mortar mix (yellow bag). Mix it very wet to get underneath the manhole. FYI - the non-shrink stuff smells like coke, however I'm told it tastes lousy and won't numb up a thing unless you swallow a few pounds of it. It's great stuff though - really helps to prevent cracks later.

5) Slop the stuff on there.

6) and once the mortar gets a bit drier use what's left to seal the inside.

Added Jan 15 - Had a tough time getting the manholes to hold -10Hg during the vacuum test a few days ago. We lined all the seams with carboline epoxy yesterday, let it harden overnight (plus almost an hour per manhole with a 70,000 BTU jet furnace to complete the setting) and tested today - none of the manholes leaked so much as a pound.

yippee - a new manhole. humorously enough these are made in the Capital Foundry in India - known to be one of the worst places on earth to work - conditions are so rotten the discovery channel did a series on them. Pictures of a bunch of small brown people running around shoeless pouring 3000+ degree steel so that we can drive over manhole covers. Aren't we the lucky ones!