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of which would harken back to medieval times.
But keeping today’s sewer systems flowing
is a near-constant struggle.
Filled with cutting-edge infrastructure,
obstacles at every turn.
>Kill the truck.
> That hardworking men and women who toil
out of sight to keep our sewage out of mind.
> Oh.
There we have it.
[WATER BURBLING]
[MUSIC]
> Ever wonder why a certain seat in your house
is sometimes called a throne?
Well maybe it’s because that particular piece of
furniture sits atop an underground kingdom.
A kingdom that we call our sewer system.
Across the country these sprawling networks of pipes
perform the often overlooked but undoubtedly
essential task of dealing with a torrent of waste water.
To the tune of 34 billion gallons a day.
That’s more volume than you’ll find
in the Mississippi River.
By a lot.
And in larger cities like Milwaukee, Wisconsin,
it takes 2,000 people and 6,000 miles of pipe
to keep their share of that sewage under control.
But right now they’re racing to clean up
the aftermath of a sewer system’s most taxing of events.
A rainstorm.
Just one inch of rain will send seven billion
gallons of water through Milwaukee’s sewer pipes.
Pushing the whole system to its limits.
And last night a storm dropped that and more
into gutters and drains across the city.
What’s worse?
There’s an even bigger one forecast
to blow in this evening.
> Tornado or hail potential.
And there is ample instability or strength
in the atmosphere for these storms to continue
to strengthen before Milwaukee gets hit
by about seven or 7:30 tonight.
> That gives the sewer workers of Milwaukee
just ten short hours to address the damage
from the previous storm.
So the entire system is ready
for the next one this evening.
And on the front line of that endeavor
are guys like Tracey McCaskill.
> We kind of operate on the philosophy
that if you don’t know that we exist then we’re doing our job.
People always celebrate firefighters
but nobody think about us.
[LAUGHS]
> All kidding aside, Tracey and his colleagues
are responsible for a system that the good
people of Milwaukee need more than they know.
And it works something like this.
Your typical household drain is designed
to run out of the home and into city sewer pipes
underneath the street.
From there gravity leads the wastewater
through countless intersections of larger
and larger pipe until it finally reaches
the city’s water treatment plant.
Which will sanitize about 300 million
gallons of it per day.
But if that system isn’t ready tonight’s
storm could easily result in a long list of
unsavory scenarios.
From sewer overflows to basement backups.
So to clean up their share of last night’s storm damage,
Tracey and his fellow maintenance technicians
are reporting to one of Milwaukee’s seven pump houses.
The facilities responsible
for keeping wastewater moving where gravity can’t.
And after last night’s downpour
their holding tanks are full of, well,
full of a lot more than wastewater.
So it’s on Tracey and his team to clear out
all the debris washed down by the rain.
Lest it clog up the pump houses’ works.
> We will open up the hatches here to the wet
well where we can begin the cleaning of the wet well.
Okay come down on the cable.
[MUSIC]
> It’s tight quarters in your typical wet well.
So while two of Tracey’s men get to cleaning,
he’ll direct and assist from above.
Must be nice.
> Here we go.
The first thing they’re doing is getting
all the solid stuff off the floor.
The next step is to remove these blogs
and rags of debris.
> A little hard to recognize at this point.
These blobs are mainly comprised of flushable wipes.
Which despite the name aren’t very sewer friendly.
> They could go in and it’ll wreck the impellers.
There’s a domino effect with wrecking the pump.
And that is the potential problem
that we’re trying to avoid.
[MUSIC]
> With the heavier debris clear,
Tracey and his team will now use a vacuum truck
to suck out the rest.
> You ready for the truck?
> Trucks like these can inhale up to 2,000 gallons
of waste at a time.
And with the business end of the hose now in place,
it’s time to start sucking.
> Tell Cal to start up the vac truck.
[VACUUM]
> But when working in the sewer business,
one never knows what one might find down below.
[VACUUM]
> Kill the truck.
> While Tracey and his team deal with the vacuum issue,
12 miles away a team of city workers
are suiting up for another mission.
Beneath their feet lies what’s known
as an approach channel.
A massive cavern that manages excess amounts of wastewater.
And when filled,
feeds that into an even larger underground reservoir.
That’s how cities like Milwaukee prevent
widespread flooding every time it rains.
But after last night’s storm,
this channel and the sensors
inside were tested to their limit.
So the crew’s heading down to ensure that everything
is still in working order before the next storm hits.
And leading that effort will be Monitoring
and Sampling Specialist Ryan Bates.
> This being an approach channel,
this is a category five.
This is the most dangerous of all the confined space
categories we have given the depth and the other
safety hazards that we have down there.
[MUSIC]
> What’s so unsafe about this part of the sewer?
Well aside from the long drop down to
a biohazardous lake, there are also a number
of harmful gases that can accumulate below.
Something Ryan will need to rule out
before they head down.
> It is reading 20.8,
which is normal oxygen level.
And then zeros on combustibles,
carbon monoxide and hydrogen sulfide.
Air appears to be good.
The site is safe to enter.
All right, I’m coming down.
>Approach channels like this one are equipped
with sensors that let guys like Ryan know
when they’re nearly full and need to be opened
into the larger reservoir known as the Deep Tunnel.
And if those sensors aren’t working
it could cause widespread flooding.
So it’s imperative that Ryan locate and test them
before the next storm hits.
> So here we are.
We are in a approach channel.
This is the structure that leads to our Deep Tunnel,
which is approximately about 400 feet
underneath the ground.
That runs underneath the city of Milwaukee.
And then it flows through a series of interconnected
channels that eventually is pumped up
and treated at Jones Island Treatment Plant.
So now we are moving downstream in the approach channel.
As you can see the walls temporarily narrow
to restrict flow.
And as you can see up above we have our conduit line
that leads to our ultrasonic sensor mounted
along the rise of the channel.
This is what we’re going to be testing out.
> But first Ryan will need to gather
some tools from topside.
In the meantime 20 miles away at the end of the sewage line,
the many tanks and agitators
at the Jones Island Treatment Plant
are hard at work cleaning the torrents of wastewater
from last night’s storm.
All under the watchful eye of engineer Ricardo Santiago.
> Jones Island Treatment Facility
sits on about 75 acres of land.
And we are capable of treating about 330 MGDs,
or Million Gallons a Day.
> Here’s a quick rundown on how all that happens.
First, the wastewater is left to sit for about two hours.
Allowing solids to settle at the bottom.
After that, bacteria-eating microbes
are added to the water, along with plenty of bubbles
in a stage known as aeration.
Finally the water is pumped into basins
where one chemical, sodium hypochlorite,
destroys any remaining bacteria before another chemical,
sodium bisulfate, is added to neutralize
the first chemical.
And just like that there you have it.
Unsanitary to pristine in just seven hours.
[MUSIC]
But none of that can happen without these.
The screw pumps.
Responsible for shuttling wastewater above ground
and into the treatment plant.
And rather inconveniently one of them
is in bad need of replacing.
So much so last night’s storm put it
out of commission for good.
So today Ricardo’s team is conducting the Herculean task
of swapping in a new screw pump
before tonight’s storm sends another flood of
wastewater into the plant.
> So the screw that we’re gonna be picking up
today is about 40 feet long and weighs 32,000 pounds.
And it has to fit in the existent trough
that is down there.
So that could be challenging.
If it doesn’t fit, it won’t spin.
If it doesn’t spin it doesn’t push
the wastewater up to the next level.
> But an even bigger concern of
Ricardo’s right now is the wind.
As the storm front moves closer wind speeds
have picked up to about 20 miles an hour.
Which does not make for the best screw pump
hoisting conditions.
> So the wind’s gonna be a huge factor.
We want to make sure that when we lift that screw up
the wind is not blowing all over the place.
It could be very dangerous for our system
and also for the workers that we got working here.
> But after a few test runs with lighter objects it
sounds like the men on the ground are willing
to roll the dice on the real thing.
> So we got word from the crane operator right now
that we’ve got sustained winds about 18 miles an hour.
The max is 22 miles an hour.
So we’re gonna give it a go
and hopefully get it installed.
[MUSIC]