80 million plastic balls to prevent Los Angeles reservoirs from becoming carcinogenic

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Mark my words. Headline from next year:

“80 Million Plastic Balls Removed from LA Reservoirs Over Fears of Them Leeching Carcinogens into the Water”.


Polyethylene? As in polyethylene terephthalate? As in “PET”? As in “leaches endocrine disrupters into water” PET?

Is there more specific info about what the balls are made of?

Update: Nonentity dug up indications that the polyethylene being used is HDPE, which on the one hand is implicated in estrogenic activity, but on the other hand we already use it to package our food and drink anyway, so no foul… sort of :smile:


How did they fill that container with balls? Did they stand it on end or is there an opening in the top?


This is not new, saw it on This Old House when they were in LA (Silver Lake) in 2011.

A giant municipal ball pit!




hmm…possibly something similar to what they did back when they used to ship grain in boxcars. There was a heavy paper/cardboard cover on the inside of the door that they’d slowly roll upwards as they filled the car…tear through it when you want to empty the car.

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33 cents sounds a little high at that volume. One quick google and I found them at half that price just for 100 at a time.


Probably one of these (sans unicorns, naturally)

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Do they do anything to reduce evaporation? If it was me, I’d shape them as hexagonal pucks for 100% coverage. This idea was being looked at a while back to cover tailings ponds at the big copper mines in the Atacama to reduce the evaporation of (scarce and increasingly expensive) water.


While they were at it I’d think they’d want to make them white so they’re slightly more reflective to reduce the head sink effect. Maybe it’s negligible?


PE and PET are very different. Polyethylene is a polyolefin, pretty similar to paraffin wax. On its own pretty inert. Long chains of carbons, each with two hydrogens attached. Polyethylene terephthalate is a polyester, where terephthalic acid and ethylene glycol moieties are alternating. Both may or may not contain additives, which may or may not be problems.


They’re also supposed to reduce bird activity in the water, meaning less bird poop and the odd floating or sunken dead bird. As for reducing evaporation, I’m curious about that as well, as it should reduce the evaporation effects of wind over the surface of the water, but the color of the balls may increase evaporation effects by reflecting less light and retaining heat. I’m surprised that they don’t use a white version of these balls, supposing such a product exists.


Polyethylene as in HDPE.

From what looks like a related article (though it may be talking about a different reservoir):

The reason LADWP is using the bird balls is because they are the ONLY National Sanitation Foundation (NSF) drinking-water-approved product of its kind on the market. When we discuss NSF approval, it means that this product has been tested precisely to ensure that it does not create the kinds of problems that some are insisting they create. The balls are made of High Density Polyethylene – a long-time water industry product also used for pipelines, and a black version of the same clear product you buy your one gallon container of milk in (look on the bottom for the HDPE label).


Hmm. Apparently some people use ping pong balls to reduce evaporation when cooking sous vide, but there is significant debate about whether that actually does much. People have tried it with reservoirs, though a quick search doesn’t turn up much hard science on the subject. Seems like there are a couple of things working against that idea in this case; first, the balls are hollow, which means they float high and don’t reduce the evaporative surface much, second they are black so they are likely to increase the temperature near the surface, increasing the rate of evaporation. Still, you would be blocking a theoretical 60% or more of the surface from direct sunlight, so it might have some positive effect. Certainly with something that packed more closely, covered more surface, and reflected light instead of absorbing it, there would be a much higher reduction in evaporation - possibly even approaching 100%. Shame they didn’t think about that when contracting for these balls.

close inspection of the video however shows no sign of that, so the trailer is probably one of those with a roll back top.

Black apparently blocks UV better.

As for coverage, even if the balls float high, (covering less of the water) the more humid air next to the surface still has to exchange with the less humid air above them through the triangular area between the balls, which is going tl tend to slow down evaporation…


I wonder why they didn’t use empty, sealed aluminum cans? Certainly they’d be cheaper, they’re non-reactive, and once the inevitable “we shouldn’t have done this” happens they’d be completely recyclable.


I want so badly to build some loop-de-loops and giant windmills and turn the thing into the world’s largest ball maze.