Los Angeles' Underground Sewer Technology

Sewer- Lines,Drain Drones, Hydro-Saws of LA's Waste Sub-surface Tour

When you think of a city's sewer operations, you probably think of one of these trucks pulling up outside your house. Some issues certainly require large-scale interventions, like thegiant balloonthat LADWP is using to choke the massive water main break at UCLA. But in many cases, as Carlson and his team were happy to show me at their headquarters in the San Fernando Valley, what's blocking a sewer drain is something relatively tiny-a crooked PVC pipe, a tree root, a pair of dentures.

One-by-one, Carlson laid out his secret weapons for me to see, an arsenal of claws, saws, and egg beater-like machines which can be affixed to the trucks' hydropowered nozzles. These are all devices that Carlson and his team have invented to solve very specific problems in the LA. sewer system, each engineered to fit the diameters of LA's standard drains (the average sewer drain is eight inches wide).

Carlson is clearly a professional-he's been with the city for 26 years and before that was a machinist in the Navy. But at this moment it felt as if I was peeking inside a macabre torture chamber.

The crew set up a demonstration to show me a scenario that happens often in the underground world: a PVC pipe feeding sewage from a home slips too far into the larger ceramic drain under the street, causing a backup. This is called a "protruding lateral." Usually, this would require crews to dig up the connection, clear the blockage, and replace the pipe-a costly and messy undertaking. But not anymore.

Carlson's team started with one demonstration in a clear plastic pipe: a torpedo-like drill which easily bored into a 2x4. No problems there. Then it was time to fix the protruding lateral. The guys flipped on the high-powered hoses that propelled a spinning diamond-tipped saw down the clay drain. It chewed right through the PVC in minutes.

That was impressive enough, but the big sewer star-and my favorite among them-was an adorable (yes, I can call it adorable) drain bot that reminded me of a squat, Tonka-wheeled Johnny 5. These remote-controlled cameras byArieshave become the saving grace for Carlson and his crew, as they can now get a clear picture of obstructions before they determine how best to clear them using their array of tools. And now these methods have become standard at sewer yards across the county, which has led to a reduction in spills overall.

As in most cities, LA's sewers were built segment by segment over many decades by hundreds of different contractors. The city alone maintains 6,700 miles of these underground mazes. "The conveyance system is such an arena," says Carlson. "Once you flush the toilet, you have to think about how far it travels, then is treated to the point that it's almost drinkable, and then exits into the Santa Monica or San Pedro Bay." (That doesn't even include the storm drains, which are a completely different system than the sewage system in LA. Many other cities combine them.)

So perhaps it's not very surprising to hear that the city is still piecing together its sewer maintenance map. Archival data is being gradually imported into a publicly accessible online directory calledNavigate LA, which is managed by the Bureau of Engineering, but there are still plenty of gaps. One major part of the sewer system that has not been accurately mapped is the only way to access them: manholes (or the more proper term, maintenance holes).

Source: Gizmodo

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Taxonomy

• Sludge Separation
• Infrastructure