OLD BRIDGE - To the west is the Marcellus Shale, one of the richest natural gas beds in America. To the north is New York City, a metropolis of 8.5 million people with heating energy needs.

Stuck in the middle is New Jersey.

Now, a megafirm is proposing to expand energy infrastructure in the Garden State in order to move more natural gas from wells in Pennsylvania to homes in the city.

The plan calls for a new pipeline across the bed of the Raritan Bay.

That has pipeline opponents up in arms, worried that New Jersey towns will absorb all the risks, that sea life could be disturbed or worse, and that the added investment will continue to delay a transition to renewable fuels, like wind and solar.

This is one of a handful of pipeline projects moving forward in New Jersey. You can see how pipelines are proliferating in the video at the top of this story.

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Let's take a closer look:

1. What is it?

The 26-inch wide Raritan Loop pipeline, a segment of what's known officially as the Northeast Supply Enhancement project, would run 23.4 miles from Old Bridge into the Raritan Bay — parallel to an existing pipeline — before reconnecting to the grid south of the Rockaways, in the New York City borough of Queens.

It would represent another branch of the Transco pipeline network, the largest interstate system in the nation. That network is owned by Williams Cos., a $26-billion energy giant based in Tulsa, Oklahoma.

The gas — enough to supply 2.3 million homes — would be shipped to customers in Brooklyn, Queens, Staten Island and Long Island.

2. When will it be built?

The project still requires approval from the Federal Energy Regulatory Commission, the state of New Jersey and other regulators.

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Williams filed an application with the FERC in March. The company says that if it gets permission to build, construction could happen as soon as next summer.

3. The argument for it

Burning natural gas releases both carbon dioxide and methane, greenhouse gases that drive global warming. However, natural gas is far cleaner than coal and oil — two fuels that it would be displacing.

Natural gas supplies have swelled in recent years, causing the cost of gas to plunge and making it an attractive fuel for home heating and electricity generation.

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The savings are reflected on utility bills.

By 2040, the typical American household would save $655 annually thanks to the spread of natural gas, according to a study by the American Petroleum Institute.

There are also the economic benefits of the actual construction.

A Rutgers study found the project would create $239.9 million in economic activity in New Jersey — most of it in the form of wages.

4. The argument against it

With pipelines and compressor stations — facilities along pipeline routes that speed up the flow of gas — comes the risk of leaks and explosions.

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The risks borne by New Jersey come with little lasting benefits. The gas wouldn't serve customers in the state, and the annual property taxes — about $1.3 million — is relatively insignificant.

Whales, turtles, fish and other sea life in the bay could be disturbed by the construction. The noise alone would be spread over thousands of acres, according to the NY/NJ Baykeeper.

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Natural gas is cleaner than some other carbon-based fuels, but it's still a contributor to climate change.

"The No. 4 (heating) oil in New York is a legitimate problem," said Patty Cronheim, outreach director for ReThink Energy NJ. "But are we just sacrificing one fossil fuel problem for another?"

5. What's next?

Williams has multiple permits pending with the New Jersey Department of Environmental Protection, as well as the FERC application.

This fall, the company is expected to produce a draft environmental impact statement, which describes what the project would mean for the health of humans and neighboring ecosystems. The public and other interested parties will have an opportunity to comment at that point.

Sometime next year, after all that information has been taken in, Williams will create a final version of the environmental impact statement. Then FERC will either approve or deny the project.

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Russ Zimmer: 732-557-5748, razimmer@app.com