The first man to notice New York City ’s $ 1.6 billion job was a public-service corporation worker . place upright near the Hudson River in 1988 , he see it was at downcast tide , which revealed a separate body of piss bubbling up near the shore and spilling into the main current .
That did n’t seem properly at all . The worker notified the city ’s Department of Environmental Protection ( DEP ) . Back then , New York was using Cu sulfate to see algae in the Delaware Aqueduct supply , one of the city ’s three independent arteria for water . At 85 miles long , it ’s also thelongest continuous tunnelin the world .
Scientists try the gurgling , gurgle pond . It was positive for copper sulfate .
Somewhere 700 feet below the surface was a pressurized tunnel approaching 50 years of old age that was depart to necessitate to be repaired to discontinue the 15 to 35 million gal hemorrhage occurring daily . “ The dilemma was not just the fact there are crack in a tunnel hundreds of invertebrate foot below ground , ” Adam Bosch , DEP ’s Director of Public Affairs , tellsmental_floss . “ It was , where is New York City going to get its water if we shut the Aqueduct down for a year or more ? ”
The solution is a sequence of engineering feats that competition any in the metropolis ’s history : enlisting skilled divers to steer a 23,000 pound overwhelm bulkhead in spot , assembling a massive drill underground to tunnel two miles horizontally , and run citizens to begin conserve H2O for the twenty-four hours the Aqueduct — which pitch over half of the city ’s crapulence water — is drain down to its last drop .
Shaft 6 , the access item where the Aqueduct will finally be run out . Image courtesy of Global Diving .
The blame fall chiefly with limestone . The coffee bean bar of rock , it crumble well and supply short reinforcement when refinement decides to tunnel underground . The men who labored to deploy the Aqueduct in the 1940s draw the weaker sphere with blade , trusting the basics in other arena would n’t call for any additional support .
They were right — up to a point . “ We ’re seeing the cracks right where the steel liner ends , ” Bosch says . “ The belief is , if the workers had just gone a few hundred yards further with the liner , we would n’t have any escape right now . ”
After the symptom — the leaks — were confirmed in the late eighties , the city spend most of the nineties working on a diagnosis . It ’s been a dumb dig of entropy that queer nearby house physician who were suffering from the import of urine ooze : The town of Wawarsing saw flooded basements and mold issues that were so stern they promptedcity buyouts .
“ You have to consider everything , ” Bosch says . “ There are no small problem . ”
After establish the tunnel was n’t in danger of crash — under press , it ca n’t crumble inwardly — the DEP was able-bodied to reassert the location of the two outflow sites by using a remote - contain submersible vehicle that take flick of the scissure in the early 2000s . picture pick out five years afterward , Bosch says , have prove the escape have n’t gotten any worse .
More recently , a vehicle able to put in dye into suspected areas confirmed the site affecting Wawarsing had coin - sized mess that could be recompense by simple grouting once the Aqueduct is drained . The other site , near the Hudson , is long past the spot of dressing : It will need a2.5 - mile longbypass install to circumvent the damage entirely .
In society to connect the bypass and repair the leaks , engineers will have to drain the tunnel . To do that , they ’ll have to promote the pump system in Shaft 6 , one of the key approach points to the Aqueduct locate in Wappinger . That , too , would have to be run out in Holy Order to set up the pumps .
The need to inspect , reinforce , and get up Shaft 6 for that forthcoming duty fell to a squad of six underwater diver who spent weeks at a stretch living and working in a pressurized environs . Their chore would be to insert a monumental bulkhead that will help handle the millions of pounds of pee pressure looming near workers — a set so exact it allows less than a quarter of an inch of way on any one side .
To dive nearly 700 feet below the aerofoil to do the work need in Shaft 6 , however , was n’t fail to be gentle . It would require 12 - 60 minutes shifts , one after another . Having men solve just one day and then decompress was not only impractical , it would translate an already gelid operation almost interminable .
The solution : live under pressure .
Global Diving
Global Diving , the salvage surgical procedure out of Seattlecontracted by DEP to handle duty for Shaft 6 in 2007 , had six plunger spending weeks at a stretch trim down off from the international domain . This is known as chroma diving , which allows for divers to avoid decompression until the end of their term of office — typically a month . The “ saturation ” is the maximal amount if nitrogen that ’s been built up in the dead body : it ’s not going to be any more whether the diver expend a day or a week under compression .
In ordering to remain at pressure , the divers live in a customize bedroom built over the backtalk of the shaft . The 24 - foot inclosure resembled a kind of mobile home by way of NASA , with bedding , a shower , and a “ med lock ” that allowed support faculty to deliver fresh laundry , food , and other supplies without compromising the crushing , oppressive air the diver had to endure .
“ Say you go down 600 feet , ” says Donald Hosford , one of the divers on the undertaking . “ It ’s about .445 pounds per square in for every human foot . That ’s about 300 PSI . That ’s like me sitting on your dresser and you trying to breathe . ” diver had to avoid major exertion—“no bound labourer , ” Hosford says — and some suffer a level of sinew wasting away . “ You ’re sit on a single-foot and not using your peg muscles . ” Hosford , at 6 - foot-6 , did n’t spend a lot of clip standing up .
Because there ’s too much nitrogen in atomic number 8 at that depth , the underwater diver would breathe a 97 percent root of helium . Their voices were always balloon - high , which meant some of the crew had to apply a descrambler to understand them . ( While initially bizarre , loon finally develop “ helium ear , ” and the richly - sky tone begin to vocalise normal to everyone but the living staff . )
Before any restoration work could begin , Global first get a sample of the bronze room access that separates Shaft 6 from the Aqueduct to valuate its condition . It was in immaculate shape , but DEP wanted to take precautions . Global fabricated a 23,000 Syrian pound bulkhead,5 feet wide and 7 feet tall , made from concrete that would fit so snugly — with just a quarter - inch of give on any one side — that the company rehearsed its trying on before seek it submerged . When DEP was quenched it could be done , the bulkhead was turn down down the shaft on a Hart Crane and glided across a wagon train path meeting place to connect to the existing doorway .
Because everything postulate for the job had to fit in Shaft 6 ’s 13 - foot diam hatchway , tools to facilitate the job werebuiltfrom scratch . And since most were bigger than the 8 - foot diameter diving gong could incorporate , they had to be lowered and retrieve each time .
conform to the bulkhead took just about two workweek . By the prison term divers performed a 12 - hour shift and return to the bedchamber , they had just enough time to sleep and get an hour or two of take in before the next shift begin . ( Because of fire headache , electronic devices are mostly proscribe . )
After five year of scouting work , preparation , assembly , and fitting , Global finished the project inJune 2012 . To decompress , the divers spend roughly a sidereal day in the chamber for every 100 feet they had been under . After a hebdomad of that , Hosford says , “ it was just about baffle re - acclimated to society . ”
The drift separate off from Shaft 6 where divers were lowered to work on reward the bronze door bulkhead . Once drained , it will have to hold out millions of pounds of force from the Aqueduct . picture courtesy of Global Diving .
Though New York City ’s population has grown by over a millionsince the 1980s , H2O consumption has gone down . “ The peak body of water utilization was 1.6 billion gallons in 1979 , ” Bosch order . “ Today it ’s roughly a billion . That ’s down by a third . ”
Part of the reason is an effort by official and citizens to become eco - witting , installing low-down - flow toilets , shower heads and front - loading washers in residential and commercial-grade edifice . The preservation could n’t have come at a good time , since reduce usage has allowed the city torelyon the live Catskill and Croton source as the replacement piddle supply while the Delaware tunnel is dry for the six to 15 months it will take to allow for the beltway connection . “ It ’s enough to sustain the new normal of one billion , ” Bosch says .
presently , workers are boring into ground in the towns of Newburgh and Wappinger to create new access tunnels between 700 and 900 base below the Hudson . Once they ’ve run into bottom — or their rendering of it — a formidable slow machine will be lowered in piece and assembled under Newburgh . From there , it will begin the 2.5 mi journey to Wappinger . Bosch carry the drill will move 50 feet a day , upchucking world to make room for the bypass tunnel .
The tunnel will be gravitational attraction - fed , meaning Wappinger ’s side of the ring road will pillow below Newburgh’s — but only by about 5 feet . “ It ’s incredibly accurate , ” Bosch aver . ( And one of the reason two drills ca n’t just plow toward one another in half the time . )
The Delaware Aqueduct is expect to be back online in 2024 , finish 10 of painstaking assessment and problem - solving . “ This is the largest fixing of the metropolis ’s water supplying in its 180 - year history , ” Bosch says . “ We want to discontinue the losses as soon as possible , but we had to make trusted the haunt is the veracious repair . ”
