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Underground Marvels
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00:03below this historic Cincinnati neighborhood lies a forgotten underworld we found tunnels that have
00:09been sealed up for over 100 years what does this vast subterranean maze reveal about this city's
00:16past thousands of miles away overlooking the Baltic Sea is a secret underground Danish
00:23fortress carved into a cliffside what pivotal role did this concealed stronghold play during
00:30the Cold War this really is on the front line and located 170 feet below this major waterway in
00:39Liverpool lies a breathtaking feat of underwater engineering nobody had seen anything of this
00:58scale before throughout history life underground has captured our imagination it creates very
01:06frightening but also very beautiful experience now we're taking you further and deeper there's all
01:14kinds of wild theories about what could be below to unearth the mysteries the secrets and the wonders
01:22of these underground marvels lurking beneath the heart of downtown Cincinnati are remnants of Ohio's best
01:36kept secrets located 30 feet below the city streets is a network of abandoned tunnels and caverns
01:45with a rich history that shines light on its origins the magic of Cincinnati is right down these steps
01:52who built this underground labyrinth and why was it abandoned all of this industry and all of this
01:59culture starts to collapse all at once how are they now being revived being able to get a piece of
02:08living history it just fills me with joy for decades Cincinnati has had a lot going on above ground but
02:25what
02:25makes this historic city unique is what's hidden below it in the 1830s and 40s hundreds of thousands of German
02:34refugees fled to the United States in hope of a life free from repression and inequality in Cincinnati
02:42they settled in the historic over the Rhine district and they brought with them their most treasured product
02:49beer the United States is often referred to as a nation of immigrants Julie Carpenter is an architectural
02:56historian specializing in the region's rich history by the time over the Rhine was fully developed the neighborhood was
03:06between 60 and 75 percent German you see a lot of buildings that have German language on them what we
03:15know as
03:15Republic Street today was originally called Bremen Cincinnati already had an established brewing industry but the newest residents
03:23added something distinctly German for as long as there have been people in Cincinnati people have been
03:29brewing beer the earliest breweries were run by English Irish Scottish and they were making
03:35traditional English style beers ales and porters while the English breweries remained above ground the German
03:44ones relied on subterranean chambers to craft their delicious concoctions so we're walking into the
03:52fermentation level of the Jackson brewery Mike Morgan is Cincinnati's resident beer expert this room looks huge and
04:03cavernous now but it would have been packed with fermenting beer in the 1800s huge wooden vats going up and
04:11down both sides of it the only real difference between a lager and an ale is that lager yeast requires
04:19cool
04:19temperatures to ferment and ale yeast ferments at room temperature at their peak nearly 35 breweries were
04:27producing more than 30 million gallons of beer per year as demand grew local business owners had to dig
04:35additional tunnels and cellars to accommodate production all these lager and cellars have two levels
04:43and on the upper level they would ferment the beer and on the lower level they would age it
04:52most of the beer was consumed locally but soon the German logger's popularity spread far beyond the city
05:00limits it was sending a lot of what was made here down to New Orleans so if you went to
05:06the French
05:06quarter good chance was it came from right here in these lagering cellars
05:15demand increased exponentially over the Rhine and the city of Cincinnati experienced an economic boom
05:22due to beer production so much so the city earned its nickname as the beer capital of the world
05:30but building cellars large enough to house not just fermentation tanks
05:34but also thousands of barrels of the finished product was no easy task in the 1850s
05:41the enterprising brewers got creative the magic of beer in Cincinnati is right down these steps
05:49steve hampton works for an organization revitalizing the brewing district
05:53so we're 30 feet underground in the crown brewery cellars
05:57they use arch stone construction they use stone floors they were typically built by very specialized
06:03contractors cellar diggers it was very hard to do 30 40 feet underground you were in the middle of a
06:11dense urban neighborhood where there were people working and living and playing literally right next to
06:17what brewers soon realized was that their underground recipe for success had a lethal side effect
06:28fermentation produces significant amounts of carbon dioxide
06:32built up co2 would not only make these tunnels off limits for people
06:36it would also starve the fermenting process of oxygen and slow or even stop the production of beer
06:43they built these series of ventilation shafts they look like fireplaces but they're actually
06:47ventilation shafts they could actually use the natural stack effect and let the warm
06:52air out of this space and keep fresh air in here
06:57ventilation solved the carbon dioxide problem but keeping the cellars cold enough for the lager
07:03fermentation process needed further innovation early on they would use ice that they would harvest from
07:08the lakes and the rivers and the canals and literally cut that in blocks pack it away with the
07:13barrels of beer down here there's a lot of cons to ice it's expensive it's unpredictable it also
07:21melts and that creates all sorts of problems so they started using artificial refrigeration as soon as
07:27that was possible and when they did there would have been lines crisscrossing through here and it was
07:33ammonia that was run through those lines
07:38while the early brewers had addressed the temperature issue they unknowingly introduced another complication
07:46ammonia remains a very effective coolant we don't use it today because it will kill you
07:55they would oftentimes have ammonia leaks from the cooling systems that would kill draft horses
08:01it could even overcome the uh the workers down here coolant leaks were just one of the many dangers
08:08facing workers in cincinnati's underground breweries they were often at risk of being injured by rolling kegs
08:16or kegs falling down like a massive kegs of a couple hundred pounds each breaking legs and ankles
08:23beer was part of your pay and so often you were drinking while you were on the job and so
08:28drinking
08:29and old sellers weren't always the most conducive to safety so we had a lot of accidents that way
08:36as the breweries continued to boom they managed to adapt and prosper however by the turn of the
08:42century a nationwide shift was about to cast a dark shadow over cincinnati's beer making industry
08:49all of this industry and all of this culture it really all starts to collapse all at once
09:07in the 19th century innovations in beer making required breweries to undergo major upgrades
09:13cincinnati was at the forefront of these changes pasteurization in 1864 that's a big deal you don't
09:21have to consume it immediately without it spoiling we then get into technology around steel so we go from
09:29wooden vats to big metal tanks that are easier to clean and get the bacteria out of and we also
09:36start
09:37to see revolutions in glass and then in 1892 and we have the crown bottle cap
09:47despite these investments society was changing and the industry was in for a rude awakening
09:55the united states enters world war one in 1917 when that happens all of that germanness that made over
10:03the rhine such a unique european feeling place that all becomes bad so that's really the first blow
10:12prohibition goes into effect nationally in 1920 and so all of this industry and all this culture
10:18it really all starts to collapse all at once by 1918 laws were passed forcing breweries to shut down
10:28and for many years things looked very bleak for the over the rhine district some breweries tried to
10:36survive by brewing illegally but police raids squashed most efforts and soon the cincinnati breweries were
10:43seemingly forgotten now decades later there's been a recent drive to revive the area combined with a new
10:51popularity for high quality craft beer the over the rhine district is being brought back to life
10:59breweries are reopening and the community is once again embracing its vibrant past
11:05as these tunnels and cellars are renovated some unexpected discoveries have been made
11:11we found a new access to tunnels that have been sealed up for over 100 years here in cincinnati
11:17brett coleman baker is a chemical engineer turned craft brewer now operating in over the rhine he's
11:25found an unusual use for the unearthed cellars these tunnels were discovered three four years ago when
11:32the new tenants bought the building they punched this hole out and what did they discover besides a massive
11:39pile of rubble and a big freaking hole in the ground get your lights on it's a little dark down
11:46here so this is the f and j a link brewery lager tunnels
11:55look at this what we have here is the top of a barrel you let it ferment then you let
12:01it lager which
12:02is aging brett realized that the original wood fermenting tanks could still be harboring life in their timbers
12:11yeast lives up to an inch deep in wood there's a really good chance that this yeast has sporulated
12:18which means that it is in a hard shell and it can basically just hibernate for as long as it
12:26wants
12:26in that until it gets dropped into liquid conducive to its growth so we're talking sugar we're talking
12:33nutrients brett took swabs from the link brewery and sent them to a lab to be tested one swab now
12:41it
12:41doesn't look like we got anything to the naked eye but that doesn't matter because we just need a tiny
12:46little spore that you're not even going to see we're going to dip it into our jar seal it back
12:53up and
12:54hopefully get something good out of it out of 100 swabs taken one successfully picked up spores of
13:01brewer's yeast tiny microorganisms that survived in the barrels for over a century being able to get
13:10a piece of living history that survived from before prohibition here in cincinnati is just uh
13:17i mean it's just it just fills me with joy the yeast spores were grown under controlled lab
13:24conditions and returned to brett to create a brand new 100 year old beer today craft breweries are on
13:32the rise across the country but in cincinnati it's more than a trend it's a tradition that dates back more
13:39than 150 years
13:56on the south coast of denmark overlooking the baltic sea is a cliff face hiding both military and
14:04prehistoric mysteries we're ready if you decide to attack us carved directly into the rock is an
14:12impenetrable fortress with more than a mile of underground passageways tough enough to withstand
14:18a nuclear bomb shock waves from a nuclear blast would be deflected as the cold war escalated this base was
14:27equipped with the latest technology and built to be on the front line science with special forces
14:34to climb up the cliff outside
14:48in the late 1940s denmark was reeling from the impact of the second world war
14:55it had only recently been liberated from nazi control and the country desperately wanted to rebuild
15:02but just as one war was ending another was beginning as political and military tensions grew between
15:09the east and the west nato called upon denmark to play a major role in the cold war as the
15:16first line
15:16of defense from russia's red banner fleet denmark was sometimes called the guardian of the baltic
15:24usually people just say the cork in the baltic because baltic is kind of like the bubble and there's
15:28these really narrow straits you have to get out of to get out of the baltic
15:33ibn bjornsson is a historian and curator at the stensford museum she works to preserve the memory of
15:39the crucial role this cork in the baltic played in 1949 denmark joined nato and with that it was solidified
15:48in a future war the enemy would be the soviet union the soviet baltic fleet was their main fleet
15:56in a war they would have to move that fleet through the danish straits and out into the open sea
16:03so the purpose of stensford was to close off the sound
16:08denmark's task was to hold the cork in
16:11and prevent the entire baltic fleet from coming out into the atlantic that was a pretty important task
16:20war could potentially break out at any moment and there was nothing protecting denmark from the enemy
16:26the stensford would be the first to know about an imminent attack and it would be their job to alert
16:32the world
16:33sometimes for british but especially americans for them the actual battlefield in a war was something
16:40far away you have the enemy right there this really is on the front line of the cold war but
16:46also
16:46would be on the front line of an actual war
16:52stensford was intentionally constructed so the danish could not only see an attack starting
16:57but potentially had a chance to intervene you would have sea mines sort of covering
17:04the stretch of water and then you would have the big guns now these two guns were to support the
17:11mine
17:11fields and shoot down the mine sweepers which would be sent in advance
17:18denmark alone would not stand the chance against the soviet fleet the task for denmark within nato was
17:25to hold the line for long enough for reinforcement to come from the west building a subterranean
17:31fortress that could survive the first strikes of enemy aggression was crucial
17:36but unlike some military complexes built during this time stensford had one huge advantage
17:52fire
17:53strategically located on denmark's south coast stensford was in prime position to monitor the
17:59baltic sea during the cold war any maritime vessel friend or foe would not go unnoticed
18:07no expense was spared in building the fort
18:10so with all the tunnels and nooks and crannies it's 1.7 kilometers
18:15it's built into nearly identical sections to support the two big guns on the surface each section
18:22supporting one gun an attack was considered so likely that when building the fort the tunnel
18:29layout was designed with a breach in mind where we're standing now you can see the hallway it makes
18:35sort of a little bend or a little break and that's because if the enemy takes one section he's not
18:41able to stand down there and shoot into the other section
18:48what was unique to stensford in comparison to many other military bases around the world
18:55is that its existence wasn't classified
18:59nato wanted the communists to know it was there
19:02the russians were also supposed to know that we had a military installation waiting for them here
19:09pointing out towards the baltic and we're ready if you decide to attack us
19:16when determining where to locate their cork in the baltic
19:20denmark deliberately chose this site for several reasons
19:24possibly the most important is that it could withstand a nuclear blast fire
19:35answers to how and why can be found 65 million years ago you can see it has different layers of
19:43limestone flint limestone flint dr jesper milan has spent his career studying the geology of stensford
19:53the rock formations along this coast are unique in their specific makeup
19:58and it was no mistake that this location was selected for the construction of stensford
20:03the limestone is quite porous and flexible and the flint is very solid like glass so that makes a sandwich
20:10construction that actually makes it a very very strong cliff side and the idea was that the shock waves
20:17from a nuclear blast would be deflected by these sandwich layers here and that should bump proof
20:23the stones fortress the impact absorption of the rock is the result of several fortuitous stages in its
20:31evolution if you see it from a distance we can see the layers are curving they're curving in big mount
20:38like structures that's actually the old shape of the sea floor 66 million years ago
20:44all the white chalk here the skeletal remains of tiny tiny animals that lived on the sea floor at that
20:50time and then they died the skeletons collapsed a new grew on top of them more skeletons collapsed
20:56forming big big layers of limestone through time the flint layers are actually very very interesting
21:01they are composed of tiny needles from sponges the most unlikely animal to form a solid rock these sponges
21:10had a skeleton of glass needles and when they died the glass needles dissolved and crystallized in the sea
21:15floor forming these big layers of flint if the fortress was under nuclear attack the alternating layers
21:24would behave like a mattress gradually bending absorbing and dissipating the shock waves
21:34and then they would be able to move to the sea floor to the sea floor to the sea floor
21:36to the sea floor
21:37should war strike stentsford the base had to remain operational this required it to be equipped with
21:43the very latest in surveillance technology this is the heart of the underground if war broke out
21:50you would have your operation center down here this was really top of the line electronic surveillance gear in the
21:5780s
21:58red ships are water-packed ships of course the blue ships are our own nato ships the green ships are
22:05civilian
22:05and the white ships are unidentified this is where you would have your overview of all traffic going
22:13through the south throughout the cold war there were times when tensions nearly boiled over to full-on conflict
22:25during some of the major crises this place went into high alert which means lockdown
22:32cuban missile crisis was one you had people down here for a week a week and a half
22:39hongary 1956 was another and czechoslovakia 1968 was another you would have the order clear thought which
22:47means everyone is underground you don't get radio signals down here you you didn't get newspapers so
22:55they would just basically receive no news
23:00i imagine that would have been quite scary despite the depth of the fortress there were risks inside and
23:09out none more so than the russian navy who remained unnervingly close we were very close out there
23:17sometimes it was spit on a dick actually
23:30visible to all the world stensfort was constantly under threat during the cold war
23:36troops stationed here knew that should war break out they would likely be the very first russian target
23:42i was here in the beginning of the 80s my job down here was as electronic technician maintain all the
23:50electronic equipment radars brian hekto sorensen is a retired naval officer who served at stensfort
23:58in the beginning i was some years at the danish torpedo boats we were very close out there on the
24:05russians sometimes you could spit on the deck actually so it was a very tense situation sometimes
24:11the polish crisis started when i was here the polish crisis began in 1981 with a worker uprising and
24:22threatened the communist stronghold in the country as the soviet union planned a military intervention
24:28naval activity greatly increased right on denmark's doorstep rumors that the russians had put a bottle
24:36of vodka in the foxhole outside those who said there are signs with us special forces have climbed up
24:43the cliff outside stensfort went into lockdown in anticipation of an attack this escalated russian ships
24:50coming in the waters around total standing here by the bunks for the people in the operational room
24:58in case of a hot situation the fort could be closed down for 30 days people in the fort could
25:05not come out
25:06and were forced to sleep here during the lockdown food and water had to be readily available
25:13and a secure power supply maintained if war were to break out you knew that relatively fast the main
25:20power lines would be cut the fort is built to be self-sufficient for three months that's why you had
25:27your
25:27emergency generator and that runs on diesel oil the troops below ground were on constant alert
25:34numbers this room was where i was normally stationed when i was on duty when i mean shooting exercises and
25:41in the hot situation
25:45this room is the radio room it was a restricted area where only cleared people were allowed for security
25:53reasons you could say this room is the heart of the stem fort this is where everything is controlled
26:01so 30 people was of duty all time down here
26:07one of the most important jobs was operating the formidable cannons aimed at the narrow passes of the orison strait
26:16this is the ammunition magazine here we have playing the grenades with the fuse
26:20six at a time six each minute different types of grenades about 500 of them
26:32the guns had a colossal range but they needed to be fired accurately if they were to be effective
26:38it was a multi-step process this room is the heart of the artillery system
26:44it's mechanical it's it's an an analog mechanical computer there's no electronics in it
26:51and all the basic data is put in by these handles then i use to calculate the trace of the
26:56grenades
27:06inside the gun you could have a crew of 18 people in here here we have the main gunner
27:11and then you would have people manning sort of each side this is actually the main the main barrel
27:19down here you can climb all the way down to the underground
27:27with the threat of the cold war and nuclear warfare looming over stentsford
27:32it was fitting that during construction scientists discovered this site was no stranger to devastation
27:39this tiny clay layer here contains an environment called iridium which is extremely rare on the earth
27:45but this layer here contains more than 60 times the amount of iridium that could normally occur on earth
27:52that caused the scientists to study it to suggest that earth was hit by a big big asteroid
27:59they calculated must have been around 10 kilometers in diameter that's bigger than mount everest
28:05and that hit the earth 66 million years ago
28:08in denmark we call this layer the fish clay because they found the fish skeletons in it
28:12the fish clay contains the dust that engulfed the earth when the asteroid hit and blocked out the
28:17sunlight causing a global nuclear winter and caused the big mass extinction dinosaurs and more than
28:23half of the life on earth became extinct thankfully the cold war never escalated to the point that
28:30stentsford's powerful defenses had to be put into action by the early 90s the soviet union collapsed
28:38and without an enemy to defend against the fort was eventually closed in 2000
28:45its role now is to serve as a memory of the cold war on a front line that few knew
28:51about
28:53the cliffs surrounding the fortress are evidence of one extinction event
28:58the fortress itself evidence of an extinction event avoided
29:16in the northwest of england lies the city of liverpool beneath the mersey river is one of the greatest
29:23man-based man-made engineering achievements of the 20th century at over two miles long it was
29:30unprecedented for its time nobody had seen anything of this scale before prior to being known as the
29:37home of the beatles the global port of liverpool was experiencing growing pains traveling from one
29:44side of the mersey to the other required ferries and lots of time with the increasing popularity of
29:51the automobile people needed a quicker way to do business and engineers had the answer it's all
29:58done by hand picks small explosive so how did the tunnel designers figure out how to beat the river at
30:05its
30:05own game it was very very difficult to control the ground water
30:20for centuries ships transporting goods across the world have navigated the river mersey into the port of
30:27liverpool the river was also a vital means of moving goods and people locally
30:32in the early 1900s everything had to come across by ferry people livestock horses and carts yet the use of
30:42motor vehicles was increasing exponentially around the globe and engineers were searching for solutions
30:47to handle a new phenomenon called traffic jams in 1922 alone 640 000 cars trying to get from liverpool
30:57across the mersey to birkenhead caused chaos the traffic was building up either side of the river
31:04so something had to be done local engineers got to work attempting to solve a problem that no one in
31:11the
31:11world had successfully done yet sir archibald salvage one of the city engineers at the time appointed a committee
31:18to tackle the infrastructure problem the committee proposed two options build a bridge or a tunnel
31:25the bridge was a really expensive option compared to a tunnel they also knew having come out of the
31:31first world war that a bridge across the river would be a target for enemy bombers
31:37after several years of debate the committee voted for a tunnel
31:42the next challenge was to find an engineering genius who could build it
31:52determined to keep the traffic flowing freely in the city of liverpool
31:56sir archibald salvage asked the government for financial support to build the tunnel
32:00chancellor of the exchequer was winston churchill when they agreed to fund it to the tune of two and a
32:06half million pounds sir archibald salvage appointed sir basil mott who was one of the real titans of
32:14british engineering at the time to lead on the project
32:18mott had overseen some of the country's largest engineering feats including bridges over the thames
32:24and installing the first escalators to london's underground but nothing would surpass the enormous
32:31engineering challenges he was about to face if there is some joint or fault of the lock the water can
32:40come through that joint so it can make some severe damage or severe failure of the tunnel
32:56in the early 20th century the world was trying to cope with a new phenomenon traffic jams
33:04in liverpool engineers were attempting to combat this problem by building an underwater tunnel
33:10on a scale that had never been attempted before dr hyunjun so of the university of liverpool has worked on
33:18some of the uk's biggest tunneling projects underground water excavation is very difficult
33:25100 years ago it was very difficult to control the ground water under the liver the soil or lock
33:33condition is much softer so during the tunneling the water pressure control is one of the important
33:46pot the plan was to build a two-mile-long tunnel 170 feet below the river mersey but with no
33:54modern
33:54equipment at their disposal the excavation alone was a dangerous undertaking this tunnel was all dug by
34:01hand 1700 men working on it at its peak and it's all done by hand picks small explosives engineers
34:09decided to start with two exploratory pilot tunnels on each side of the river to make sure conditions
34:15were safe to continue digging the goal was for the two tunnels to eventually meet in the middle
34:21to accurately meet in the middle they had a depth measuring stick which they would shine the light
34:27across to the next step measuring stick and make sure that they were coming out at the same level each
34:33time
34:36after three years of back breaking work on april 3rd 1928 the two teams met under the river
34:44when they met in the middle they were less than an inch out so it was very accurate work back
34:49then
34:51even though the pilot tunnels were a success the main tunnels were much larger meaning engineers had to
34:57dig in every direction and soon only four feet of rock stood between the workers and the raging river
35:04above one wrong move could have been catastrophic modern underground construction uses boring machines
35:13to seal the tunnels as they go but the workers tunneling in the early 20th century had rudimentary
35:20technology to keep the mighty river mercy at bay since over 1.2 million tons of rock needed to be
35:27excavated
35:28experimentation was necessary to find the best solution to waterproof the walls we make a ball
35:35hole and we take a sample and we know the all the ground condition before the tunnel construction
35:40like underground mapping however 100 years ago they don't know the ground condition very well
35:47the workers installed 100 000 cast iron linings weighing more than 70 000 tons all by hand to support
35:57the tunnel if there is some joint or fault of the lock the water can come through that joint so
36:05it can
36:05make some severe damage or severe failure of the tunnel yet water wasn't the only issue engineers had to contend
36:14with
36:27in the early 20th century groundbreaking designs for the mersey tunnel had managed to protect the tunnel and
36:34its crew from the river the next challenge was to rid the tunnel of lethal exhaust fumes
36:41with combustion engines passing under the mercy at a rate of 4 150 per hour the risk of a catastrophic
36:49disaster was high the project's lead designer sir basil mott needed to devise an ingenious plan or this
36:57airflow issue would threaten the entire project
37:02using a mixture of longitudinal and transverse ventilation they designed a unique system to vent
37:08toxic fumes from the tunnel the air is now coming down from the fresh air fan and it comes down
37:15the
37:16shaft and it meets these walls these walls we call our banana walls because they're curved the longitudinal
37:23system funneled air along channels running parallel to the road it was then diverted away and the air
37:30filtered the airs come around the corner along this air invert to get it on the road deck you've got
37:36this
37:36series of holes on the underside so the air travels up through those hits a u-shaped structure which sends
37:42it off across the road deck at about exhaust level the transverse ventilation used a system of ducts in
37:49the walls and ceilings to inject air and remove exhaust gases the fresh air comes through under the
37:57pavement that air pushes the quality air through that exhaust duct
38:05to sustain this system over a two mile underwater tunnel required serious power
38:12capable of delivering 2.5 million cubic feet of fresh air every minute
38:19and withdrawing the same amount this huge fan it's 28 feet wide weighs 25 tons it can actually create a
38:29wind speed of about 36 miles an hour
38:34building had to be built around them because of the sheer size of them
38:38that's what's going to be built on this scale before
38:45having overcome this mammoth undertaking on july 18 1934 the tunnel was officially opened by king george v
38:55this tunnel was actually described as the eighth wonder of the world when it opened because nothing had
39:01been built on this scale before people came on holiday to liverpool just to drive through the tunnel
39:07because they'd never experienced driving underwater before
39:14not only was it deemed the longest and largest tunnel ever attempted beneath a major body of water
39:21it was by far the most modern and technologically advanced
39:27two underwater junctions would service four lanes of traffic under the mersey
39:32between two entry and exit points on either side of the river
39:37the mersey tunnels is a 24-hour operation it never sleeps
39:43today liverpool has a dedicated team to maintain this massive underwater transit system
39:51paul heaton is one of the engineers taking on this crucial role
39:54the workmanship back in the 1920s and 1930s of the original builders of the tunnel was fantastic
40:01it's left us with a really good structure to maintain yet the power of the river surrounding the tunnel
40:08is relentless and every day water leaks through underneath us now the huge sump it spans the width of the
40:16queensway tunnel
40:18this pump manages to pump out 145 meters cube of water every minute
40:25pushed out by the pump into the main sewers in birkenhead
40:30if these pumps fail disaster will likely follow the water would fill up the sumps
40:36and it would actually fill up these rooms we wouldn't have a tunnel because it would be underwater
40:43but a lot has changed since the tunnel first opened during its first year nearly two million vehicles
40:50passed through today 12.8 million vehicles travel safely through the mersey tunnel every year
41:00this infrastructure is key to the economic success of the area
41:09the ambition and engineering prowess of the early 20th century builders who dared to tame the mersey
41:15is nothing short of inspiring and remains truly impressive even by 21st century standards
41:28the key to the new 19th century builders and the new
41:29new
41:29new
41:29new
41:29new
41:29new