June 03, 2014

Photo Essay: Keeping LA's Water Supply Drinkable (And Accessible)

Now known as the Los Angeles Reservoir Complex, a huge basin area in the Sylmar / Granada Hills region, not far from The Casades, used to house the San Fernando Reservoirs (later renamed Upper and Lower Van Norman Reservoirs).

The rebuilt, current reservoir – an outstanding civil engineering achievement – is rarely open to the public for visits, and is usually held under tight security.

This is the part of the Los Angeles Aqueduct system where filtered water – now potable – can either be gravity-fed out to drinking consumers...

...or stored in a concrete-walled, 176 acre, 3.3 billion gallon reservoir.

The water stored here is owned and managed by the LA Department of Water and Power...

...which must keep the site secure... from vandals, copper thieves, and terrorists... well as from any little critters (including birds) that might want to take a drink or a swim.

Water regulations dictate that any open water reservoir must be either decommissioned or covered... the DWP is in the process of covering it with these BPA-free plastic balls, weighed down with 1/3 water so they don't blow all over the Valley when the Santa Ana Winds kick up.

There are already millions of balls covering more than half the surface of the water...

...and trucks deliver tens of thousands at a time.

This was the site of the former Lower Van Norman Dam (now shaved down)...

...which failed in the wake of the 1971 Sylmar earthquake, causing massive evacuations of those households downstream from the dam.

At the time, the DWP wasn't surprised at the dam's failure: they knew it had to be fixed, and had built a backup reservoir to handle overflow, just in case. Turns out they needed it, and although meant to be temporary, it's still there (with a new metal cover).

Compared to other major dam breaks of the LA area (including St. Francis and Baldwin Hills), the Van Norman failure could've been a lot worse.

You can walk along the entire perimeter of the LA Reservoir...

...along dikes that lead to a bridge... the southern (or lower) part of the reservoir that's not covered quite yet..

...and favored by seagulls.

Each side of the reservoir also features a spillway, leading to a canal-like drainage trench below...

...just in case there's too much water. But these days, in this drought, that's probably not going to happen.

The entire complex features several different structures and facilities...

...including some leased out to other municipal entities...

...but the focus here is on water (including some seepage, some drainage, and mostly drinking).

At one time, the main tactic for rendering the incoming water potable was by use of chlorine (which was used heavily to fight the "green slime" algae growth).

The DWP has been able to back off the use of chlorine with the opening of the new UV filtration plant...

...the largest of its kind West of the Mississippi.

It treats enough water for all four million LA residents on a daily basis through 14 giant pipes...

...each quipped with its own reactor with UV lamps.

At any given time, 12 are active, with two offline as backups.

The UV disinfection actually provides further purification of the incoming water, which has already been purified at another filtration facility up the road, which receives water from The Cascades.

Using UV instead of chemicals reduces the production of by-products by reducing the use of chlorine (instead favoring chloramine, an ammonia derivative that includes chlorine atoms). This is especially important since stored water is treated both before it goes into the reservoir and once it's drawn from the reservoir to go out to thirsty customers.

The new UV facility (named after a former Director of Water Quality), which just opened up in May, is currently fully operational, and is meant to be completely unmanned (save for the security personnel stationed at the front entrance and patrolling the area).

It's one of those places you might catch a glimpse of from the 5 freeway, get distracted, and forget all about.

Google Maps Satellite View

Related Posts:
Celebrating the LA Aqueduct Centennial at The Cascades
Photo Essay: The Power Plants of the St. Francis Dam Disaster
Photo Essay: Lake Hollywood Reservoir
Photo Essay: West Basin Water Recycling Facility

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