Published: December 15, 2023 |

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Neiswonger Construction Inc., which operates the Maggie Lynn limestone quarry in Washington County, is hoping to start extracting the rock underneath it.

The company is proposing to build an underground mine that would stretch for 337 acres in Deemston Borough, roughly the area of Schenley Park.

It might take 30 years to extract all that rock, cranking out 250,000 tons of limestone a year, as the mine is initially slated to produce. Or, if demand is robust enough, Neiswonger said in its environmental permit application that things could move much faster, ramping up to 900,000 tons a year.

Today, demand is booming, the company’s president Vinnie Neiswonger said.

Neiswonger sells the stone it mines for use in asphalt, concrete, and gravel.

After the Infrastructure Investment and Jobs Act supercharged the construction business in the public sector, Neiswonger said demand picked up considerably.

“Every bit of concrete that’s poured (on a bridge), every bit of pipe that goes into the ground that has to have stone on top of it, every footer, every foundation — all of it requires limestone to keep things solid,” said Vinnie Neiswonger.

The cost of limestone began a sharp rise in 2022 and by this October — the latest for which data is available in the producer price index which tracks wholesale prices — it was up 30 percent.

“The Pittsburgh area alone uses millions of tons of stone a year,” said Neiswonger.

His construction company, which does site prep work — whatever involves moving dirt — uses its own limestone on local projects.

Strattanville-based Neiswonger began preparing environmental documents for the underground mine in 2019 and the project hasn’t been a secret in Deemston Borough. But the first public meeting with a comprehensive look at its permit is scheduled for this week.

There, the Department of Environmental Protection will talk about the proposal and how the agency will evaluate it.

Some area residents have been calling the township for months worried about potential impacts to their water wells from a large underground mine.

Melissa Jay has been fielding these calls since she was hired as the borough’s secretary in March. People have called to complain about dust from the quarry and to lament that they passed on the opportunity to have a public water line put in two decades ago, she said.

“I get all the complaints,” said the borough’s secretary Melissa Jay.

But there’s not much the township can do about such concerns, so Ms. Jay has been forwarding them to state environmental officials and trying to promote a meeting for everyone involved to be in the same room.

Unlike the big underground coal mines of southwestern Pennsylvania which use a longwall mining technique that takes out all the coal in an area, leaving its roof to collapse afterwards, Neiswonger will use a room and pillar method.

It will remove limestone in blocks and leave behind untouched columns to hold the weight of the earth above the mine in place. The company’s permit documents set 150 feet foot buffers for mining around several oil and gas wells inside the permit boundary. Permit documents say when underground work begins, the company will stop operations on the surface at the quarry.

Neiswonger, a family-owned company started by Vinnie Neiswonger’s father in 1978, got into the limestone extraction business in 2012 when it bought the Maggie Lynn quarry, according to a company profile published by one of its vendors, Cleveland Brothers.

It has since added four other quarries in the state, one of which, in Garrett, has an underground mine below it.

There are more than a dozen such mines in the state, according to DEP records, and they can be valuable assets even when emptied of their primary commodity. Limestone mines can be turned into dry storage, where low temperatures, protected access and lack of weather interruptions shelter valuable paper and digital records.

Iron Mountain’s Butler County mine, for example, holds government documents, Hollywood classics, and a datacenter.

The possibilities include “anything that has to be in a controlled environment,” Neiswonger said, but it’s too early to think about the what and the when of repurposing, he said.

The Maggie Lynn quarry currently employs 15 people and Neiswonger expects to have 20 working underground if the permit is granted, with an additional 70 of so contractors handling logistics like fueling and stone deliveries on the surface.

He anticipates spending about $2 million over the next 12 months to build out the mine.

Source: Pittsburgh Post-Gazette

Neiswonger Construction provides demolition, site preparation, heavy construction, and mining services.

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