Shadowing Practice: Why Are 96,000,000 Black Balls on This Reservoir? - Learn English Speaking with Video

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These are shade balls.

They're being dumped into this water reservoir in Los Angeles.

And contrary to what you may have heard, their main purpose is not to reduce evaporation.

So what are they really for?

To find out, I'm visiting the largest collection of these balls anywhere on Earth at LA Reservoir.

96 million shade balls.

That's correct.

96 million.

It's very rare for you to see 96 million of anything.

This is your life vest which you are required to wear.

All right.

Throw a leg over and climb on in any way you can.

There you go.

Looking at this, I had so many questions.

Like, why are they black?

Are they safe to have in drinking water?

How much do they cost?

Do they actually reduce evaporation?

And what is their real purpose?

Is it hard to drive in Shade Bowls?

It is very hard.

Why is that?

These are actually partially filled with water.

And the reason they're filled with water is that at LA Reservoir we have some really high winds.

And so, you know, if we didn't put water in these things, there'd be balls bouncing down the five freeways people would drive down.

They'd be all over the place.

So these keep the balls in the reservoir, and if they do start to roll, they kind of wobble because the water makes them uneven.

But that makes them significantly more difficult to push out of the way, especially when they form close -packed crystal -like structures.

come together in our wake.

And some, close to the motor, are pulled along with the boat.

Wow.

- Did you - what did you think the first time they suggested doing this or when it first came in?

Yeah, it was a little out there.

Did you think they were nuts?

No, not nuts.

Well, it just - it like - it looks absurd.

It's like we're in the world's biggest ball pit.

Right.

Yeah, that's what it looks like.

Yeah, you wouldn't you can't tell by standing here that we're actually floating over.

I think it's probably 40 40 feet right here 40 50 feet deep below us.

Oh Thank you and you can't even see any water.

Uh...

You'd think it was a joke.

Right?

Like if you didn't know, you'd be like, no, you're not.

That's...

like green screen or something, right?

Yeah, it's fake.

So like when I switch on my tap at home, is the water coming from here?

Yes.

Sometimes. Or always.

Most of the time.

Most of the time the water's coming from here.

Absolutely nuts.

So why is LA Reservoir covered in shade balls?

Well, the problem all started with bromide.

Bromide is a naturally occurring substance.

associated with salt water.

And so normally places like the California aqueduct that comes down from the delta, you get some salt water intrusions, you have some bromide in the water.

Bromide's harmless and it's almost impossible to remove.

But when you disinfect the water with ozone, that bromide becomes bromate.

And bromate's carcinogenic.

And so around the year 2000, they wrote regulations regulating bromate.

And the regulations basically said, if you have a treatment plant that uses ozone, then you have to watch your bromate formation and be careful not to form too much.

So the only place we ever measured bromate was at our filter plant.

And the results were always within the 10 micrograms per liter limit set by regulators.

So they were confused when they got a call from one of their customers, a beverage company in LA.

They said, "We have some really high levels of bromate showing up.

Are you aware of this?" And we said, "Well, we don't show anything." But between the filtration plant and the customer was the reservoir.

So they did some tests.

Almost immediately upon coming into this open reservoir, the bromate levels jumped.

It turned out that bromide with chlorine, which was supposed to be safe in bright sunlight, formed bromate even more than ozone.

And so we made this unfortunate scientific discovery that actually was not part of any regulatory scheme.

And so here we are at the reservoir.

We have water source that's got bromide in it, harmless.

We have chlorine, we have to have the disinfected water.

sunlight because it's open the only choice we have is to remove sunlight

so we looked at all sorts of things we looked at floating tarps across the water

and normally you put a floating cover on the water

but that's a multi -year project and

so we said well can we manufacture these kind of trampolines with poly like PVC pipe

and we said well they're just gonna become bird perches it'll have a big water quality problem

and so then we knew we had high -density polyethylene pipe

which is used in the water industry and we know that it the surface.

Well that's hard to do and very expensive because it's a lot of material.

So maybe we could take some pipe and run into a chipper

and we can make a debris field across the surface like the back corner of a lake somewhere.

But then they have all this mushy warm water with plastic floating on the top.

That looks like a petri dish.

And so lo and behold Dr. Brian White did some research and he found the shade ball.

Except they weren't called Shade Balls at the time.

This product existed and they were called bird balls.

And they used it on ponds that had mine tailings where they didn't want waterfowl to go and get poisoned.

And also around airports where there were ponds

and they wanted to keep the waterfowl off so that they didn't take off and get into jet engines.

Bye.

I'm sorry.

You know they've actually done wind tunnel testing

100

and we had you know blue you know 50 60 mile hour winds across to see how they behave.

101

But they were really made to deter birds and wildlife from sitting on the water.

102

Did there used to be birds landing here more?

103

Absolutely.

104

Yeah?

105

Once we deployed these balls all the birds were gone.

106

They used to just hang out right loiter at the curbs.

107

Yeah they'd be all over the top of the dam.

108

They'd be down at the outlet tower they'd be everywhere but we don't get them anymore like we used to.

109

But before being added to the reservoir, the shade balls had to be tested.

110

would they actually reduce the formation of bromate?

111

And we bought three kiddie pools, three little inflatable kiddie pools, and we filled them all with reservoir water.

112

One was in the sunlight, one we put a tarp on, one we put shade balls on.

113

And amazingly, the shade balls knocked out the problem immediately.

114

So the reason shade balls are black is to block all light from reaching the water and triggering the bromate reaction.

115

The black pigment is also safe for contact with drinking water, and it's stable, even exposed to the elements for years.

116

They're black for a reason.

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So, you know, they're made out of high -density polyethylene.

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It's the same material that like a gallon milk jug is made out of.

119

It's a food -grade plastic, and they would be clear like a milk carton, except that they wouldn't last in the sun.

120

And so they have a material called carbon black in there, and that's what makes the plastic last for at least 10 years out in the sun.

121

And so it's that carbon black, the magic powder in this, that really makes this product last in the sunlight.

122

One of the concerns that people raised to me when we first put these on was that, are they going to get hot and then leach material out?

123

And they don't.

124

They're totally inert.

125

I mean, theoretically, you can cut off a piece of this ball and you can chew it.

126

No harm comes to you.

127

This is totally food grade.

128

Nothing wrong with it whatsoever.

129

What's it like driving through these things?

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It's difficult.

131

As you can see, we've been sitting here for, I don't know how long, quite a while.

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there's a breeze and we haven't moved.

133

I mean anybody that knows that's been on a boat in a lake

134

if there's a slight breeze and you're on a boat you're drifting right?

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Not here this thing they're just stable.

136

It's interesting when you try to pilot the boat through these things it's difficult.

137

It's like driving through peanut butter or something.

138

Something I guess yeah.

139

Not that I've ever done that but.

140

Blocking sunlight from the reservoir also provided additional benefits.

141

You know one of the reasons we put so much chlorine in was to control the algae growth

142

There were times years ago in the summer where if we had an algae outbreak you might actually, if you filled a bathtub up, it might have a slight change of green.

143

I mean it may be healthy to drink but it might have a slight change of green from the algae.

144

You see a bit of algae.

145

Yeah, and it's just coloring the water.

146

That no longer occurs.

147

So with the sunlight gone, the algae problem is gone.

148

We put in basically no chlorine.

149

We've only had a few times since the shade balls went on L .A reservoir that we've added any chlorine at all.

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And we used to do half the chlorine in the whole water system went into that reservoir just to control algae growth.

151

But the big concern I had was evaporation.

152

When I first heard about these black plastic balls reducing evaporation, it didn't seem to make any sense.

153

I mean, wouldn't they absorb more energy and so heat up the water, leading to faster evaporation?

154

It turns out the answer is no for a number of reasons.

155

In an open reservoir, there is more exposed surface area where water molecules can escape into the air.

156

Plus, there is greater airflow over the water surface, continually removing the layer of moist air and replacing it with drier air, increasing evaporation.

157

Now the shade balls do absorb more energy and get hotter on top, but the bottom of the balls stays cool.

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It's almost like a double pane window.

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You get that air gap in there and the air acts as an insulator.

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And so the sun never hits the water.

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Matter of fact, we've actually done some measurements

162

and it's actually cooler under the shade balls even though they're

163

black than it is without the balls just with the sun itself.

164

So the balls actually have a slight cooling effect.

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So for all of these reasons, shade balls reduce evaporation by 80 to 90 percent.

166

That's pretty significant for a dry climate like Los Angeles.

167

How much do they cost?

168

These run about around three for a dollar.

169

I think we paid 33, 34 cents a piece, something in that range.

170

And they actually have a salvage value, not that much, but if we go to remove them, they're recyclable material.

171

But we figured that over the life of the balls, between the savings in chlorination, the chemical savings, and the savings in evaporation,

172

probably at least half the cost of the balls will be paid for.

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And so, I mean, of course, the water quality benefit is immeasurable.

174

but even the balls themselves will save money doing what they do.

175

Do you ever bring people out here for tours?

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You're the first one.

177

Why am I the first one to get to go on a tour here?

178

To get this level of detail tour, yes.

179

This is so cool.

180

I've heard something about hexagonal balls.

181

Have you heard anything about hexagonal balls?

182

Oh my gosh.

183

So we had the shade balls and of course, everyone in the world came up with another product.

184

I have ones I call the ravioli, it's a small hex.

185

We had large hexes.

186

We had all sorts of pieces and people say, well, they lock together.

187

is they need to not stack up and they need to not sit on the bank of the reservoir.

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The reservoir is going to go up and down and

189

so it's really the shape of the ball that

190

that makes them not not perch on the side

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because we need to make sure that these when the water goes up

192

and down that they spread up or they you know spread out completely to cover the water as best possible.

193

I mean, I just can't get over what I'm seeing.

194

It's just so nuts.

195

I'm waiting for you to say it looks like a pool of boba.

196

I feel like that's the line that'll go in, but you got it.

197

Like, that is...

198

That's awesome. Do you like boba?

199

I love boba.

200

I might get some after this.

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Vocabulary and speaking notes for this lesson

This B2 speaking lesson is built on the video “Why Are 96,000,000 Black Balls on This Reservoir?”. The speaker keeps coming back to these words: ball, reservoir, shade, bromate. This video has 200 sentences and 2146 words to shadow. The speech runs for 12:03. The speaker talks at a natural 178 words per minute, close to everyday conversation. 84% of the words are among the 3,000 most common in English; the rest is worth studying before you start.

Key vocabulary in this video

The 15 most advanced words in the video, with pronunciation and meaning:

Word	Pronunciation	Meaning
reservoir noun	/ˈɹɛz.ə(ɹ).vwɑɹ/	A place where anything is kept in store.
shade noun	/ʃeɪd/	Darkness where light, particularly sunlight, is blocked.
bromate noun	/ˈbɹoʊ.meɪt/	the anion BrO₃⁻¹, derived from bromic acid; any salt containing this anion
evaporation noun	/ɪˌvæpəˈɹeɪʃən/	The process of a liquid converting to the gaseous state.
sunlight noun	/ˈsʌnˌlaɪt/	All the electromagnetic radiation given off by the Sun; especially, that in the visible spectrum and that bathes the Earth.
alga noun	/ˈæl.ɡə/	Any of many aquatic photosynthetic organisms, including the seaweeds, whose size ranges from a single cell to giant kelps and whose biochemistry and forms are…
bromide noun	/ˈbɹoʊ.maɪd/	A binary compound of bromine and some other element or radical.
chlorine noun	/ˈklɔɹin/	A toxic, green, gaseous chemical element (symbol Cl) with an atomic number of 17.
float verb	/fləʊt/	To be supported by a fluid of greater density (than the object).
boba noun	/ˈboʊ.bə/	Synonym of tapioca pearl.
ozone noun	/ˈoʊzoʊn/	An allotrope of oxygen (symbol O₃) having three atoms in the molecule instead of the usual two; it is a toxic gas, generated from oxygen by electrical…
disinfect verb	/dɪs.ɪnˈfɛkt/	To sterilize by the use of cleaning agent.
hexagonal adjective	/hɛkˈsæɡ.ə.nəl/	Having six edges, or having a cross-section in the form of a hexagon.
perch noun	/pɝt͡ʃ/	Any of the three species of spiny-finned freshwater fish in the genus Perca.
polyethylene noun		A polymer consisting of many ethylene monomers bonded together; used for kitchenware, containers etc.

Phrasal verbs you will hear

Word	Pronunciation	Meaning
go up verb		To move upwards.
make out of verb		To construct from; to create (something) using (a material or substance).
turn out verb		To end up; to result.
come up with verb		To manage to produce, deliver, or present (something) by inventing, creating, thinking of, or obtaining it.
cut off verb	/ˌkʌt ˈɔf/ [ˌkɐɾ ˈɔf]	To remove by cutting.
drive down verb		To cause or force a price, quantity, rate, etc. to decrease.
find out verb		To discover, as by asking or investigating.
get over verb		To overcome.

Sentences worth repeating

Short, complete lines from the video that you can reuse in everyday conversation:

Did you think they were nuts?
It's like we're in the world's biggest ball pit.
You'd think it was a joke.
Do you ever bring people out here for tours?
Have you heard anything about hexagonal balls?

Grammar in this video

The structures the speaker uses most, with the exact words from the video:

Structure	In the video
“Used to” used to + verb — a past habit or state that is no longer true	used to be · used to just hang · used to do
Conditional sentences if + clause, will/would + verb — a condition and its result	if you didn't know, you'd be
Passive voice be + past participle — the focus is on what happens, not who does it	being dumped · are required · are pulled
Present perfect have/has + past participle — a past action that still matters now	they've actually done · haven't moved · that's been

Pronunciation to watch

The speaker uses 53 contractions and reduced forms, such as they're, didn't, don't. Say them the short way, as you hear them.

The “sh” and “zh” sounds: shade /ʃeɪd/, evaporation /ɪˌvæpəˈɹeɪʃən/, chlorination /ˌklɒ.ɹɪˈneɪ.ʃən/, filtration /fɪlˈtɹeɪʃən/, immeasurable /ɪˈmɛʒəɹəbəl/
Long words — get the stress right: evaporation /ɪˌvæpəˈɹeɪʃən/, hexagonal /hɛkˈsæɡ.ə.nəl/, carcinogenic /ˌkɑː(ɹ)sɪnəˈd͡ʒɛnɪk/, chlorination /ˌklɒ.ɹɪˈneɪ.ʃən/, immeasurable /ɪˈmɛʒəɹəbəl/

How to practise with this video

Listen to the whole video once without speaking and note the words you do not know.
Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
Record yourself and compare with the original, paying attention to words like reservoir, shade, bromate.

What is the Shadowing Technique?

Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.

Shadowing technique: read the full step-by-step guide →

Shadowing Practice: Why Are 96,000,000 Black Balls on This Reservoir? - Learn English Speaking with Video

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Vocabulary and speaking notes for this lesson

Key vocabulary in this video

Phrasal verbs you will hear

Sentences worth repeating

Grammar in this video

Pronunciation to watch

How to practise with this video

What is the Shadowing Technique?