But this region is the birthplace  of the American oil industry. 

The country's first commercial  oil well wasn't sunk in Texas,  

but here in Pennsylvania, way back in 1859. 

It was the first of a vast number of wells,  drilled and worked dry across the state. 

Hey good morning Myles. When their wells are no longer viable,  

responsible companies employ experts like Luke  Plants to seal them up, preventing any leaks  

or contamination in the future. I'm gonna give you one of these,  

then we'll go take look around the site. That'd be great, thank you very much. 

But in the pioneering, unregulated oil rush  days, many drill sites went unrecorded,  

unplugged and abandoned and now honeycomb  the ground, including under cities and towns. 

Many wells exist in places that have grown up  around them so suburbs and urban areas that  

were developed long after the well was drilled,  and now they present a threat to human life. 

These images from Pennsylvania's Department  of Environmental Protection show toxic gas  

and liquids belching from old wells, contaminating  the air and threatening to poison drinking water. 

One study has estimated that the methane  emissions from the US's tally of abandoned wells,  

is equivalent to the annual  CO2 output of 2.1 million cars. 

Some forgotten well heads have even  been uncovered under people's homes. 

Plugging and sealing off a disused well  is hazardous, highly specialised work  

that can take a lot of time and money. Watch your step. 

The idea sounds simple enough: insert pipes  into the well using this towering rig,  

then link them up to inject concrete  into all the nooks and crannies below. 

So we're going from the bottom, all the  way up to the top until finally you've  

completely sealed off your well bore. But not every job is the same. 

Old bores that have crumbled or collapsed  can take a month to excavate and plug,  

and the sheer number of abandoned wells  in this state alone is staggering. 

Since the country's first oil well was drilled  in Titusville, Pennsylvania 70 miles to my west,  

there have been hundreds of thousands of  oil and gas wells drilled across the state. 

A DEP map shows the extent of the problem  in Pennsylvania. The locations of plugged  

wells in blue, swamped by the uncapped,  abandoned wells found so far in red and green. 

Many more disused and undiscovered  wells lie scattered across the country. 

To tune into the wider scale of the problem,  I've crossed state lines to Washington DC  

to meet Daniel Raimi, an academic  and expert on the subject at  

environmental think-tank Resources for the Future. 

Daniel how are you? I'm doing well, nice to see you. 

Nice to see you too. Thanks for having us in. What kind of scale of problem are we talking here? 

The scale is actually pretty staggering. The US  EPA estimates that there are about 2.1 million  

abandoned, unplugged oil and gas scattered  across the country. These are wells that  

aren't being used for production or injection  or other productive purposes, and they also  

haven't been plugged, they haven't been sealed  off. In addition to those 2.1 million wells,  

there are estimates that there are up to one  million orphaned oil and gas wells. These are  

also abandoned, but they don't have a legal owner. The dilemma surrounding so-called “orphaned” wells  

is that their original owners have  either disappeared or gone bankrupt. 

Orphans effectively become wards of the state,  

meaning taxpayers are left to cover  the costs of making them safe. 

One estimate puts the average cost of plugging  and cleaning up an open well at $76,000,  

but contractors say that figure can vary  from $10,000 to $1.5m depending on the well. 

Before breaking ground on any new well-plot,  oil companies generally pay a bond up front  

to the relevant state or federal authority. In theory, it's there to cover the cost of any  

future clean-up should the company go bust, but in  practice, any securities paid are rarely enough. 

The problem is, almost all of the regulations  at the state level don't give regulators enough  

money to actually plug the wells that would  become orphaned when a company goes bankrupt. 

Help for cash-strapped states may be on the way. 

Around $5bn has been specifically set  aside for cleaning up old wells in  

a bipartisan infrastructure bill  making its way through Congress.

That figure falls short of proposals put  forward by President Biden. But I wonder  

whether a share of the funds would make a  real difference for states like Pennsylvania. 

Its pioneering history of unfettered,  unrecorded drilling means that the  

Keystone State is thought to have by  far the most abandoned wells in America. 

On the way home I drop by the state  capital of Harrisburg to meet Scott Perry. 

It's his team at the Department  of Environmental Protection  

who arrange the plugging of problem  wells when no one else can or will pay. 

The budget is tight and clean-up  jobs have to be prioritised. 

Every well we find we rank it, according to its  threat to public safety, to the environment. 

So would a slice of the infrastructure  bill money make a significant dent  

in the long list of leaky wells to be fixed? 

If we're only able to plug say 10 wells a year,  and we've got 8,500 to go, we're in for a long  

haul. But the federal stimulus money could  potentially enable us to clear that ledger. 

Much has been made of the potential for new  jobs as politicians weigh the benefits of the  

multi-billion dollar clean-up bill. But many experts say policymakers  

need to think longer term. To tackle the root of the problem, they argue,  

any federal handouts should be tied to commitments  from states to reform their bonding systems,  

so that they can better afford  to deal with the issue in future. 

That will become all the more critical  as a transition away from oil and gas in  

the coming decades risks a dramatic rise  in the number of wells being abandoned. 

And unless states force the industry  to shell out the cleanup costs upfront,  

taxpayers could be left once  again footing a hefty bill.