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Neiswonger Construction, which is part of the Century III mall demolition project (shown here in March 2024), got the go-ahead earlier this month for an underground limestone mine in Washington County.
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Underground limestone mine in Washington County is a go

Lucy Schaly/Post-Gazette

Underground limestone mine in Washington County is a go

Production will start at 250,000 tons a year and “gradually” ramp up to 900,0000 tons

In the five years between Neiswonger Construction first pursuing a permit to build an underground limestone mine in Washington County and earlier this month — when Pennsylvania regulators granted that permit — the wholesale price of limestone rose 50%.

The material is used in all sorts of construction, from poured concrete to loose gravel and asphalt paving. It had been bolstered, in part, by federal funding coming from two Biden-era laws, the Infrastructure Investment and Jobs Act of 2021 and the Inflation Reduction Act of 2022 that included hundreds of billions of dollars for building clean energy projects and upgrading the country’s infrastructure.

And while President Donald Trump had ordered a halt to the disbursement of all federal dollars from these two laws for at least the next three months, much of the money has already been allocated or spent.

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Strattanville-based Neiswonger has been supplying the limestone market from several quarries across Pennsylvania, including the Maggie Lynn quarry in Deemston, which the company bought in 2012. Now, it will convert that site to a 257-acre underground mine with somewhere between three and seven portals.

A map of the perimeter of the proposed Maggie Lynn Underground limestone mine included in Neiswonger Construction Inc.'s application to the Department of Environmental Protection.
Anya Litvak
Surge in limestone use fuels Washington County mine plan

Neiswonger will be extracting Benwood limestone using a room and pillar method, where stone is taken out in large blocks, leaving behind untouched columns to hold the roof in place.

It plans to start production at 250,000 tons a year and “gradually” ramp up to 900,0000 tons “due to the anticipated increase in demand.”

“At this rate, the anticipated life of this operation will be 30 to 35 years,” Neiswonger wrote in permit documents.

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Neighbors of the quarry, which hugs Washington County’s border with Greene County, have complained to their township and to the Department of Environmental Protection that dust from the quarry travels off the site, cakes the outside of their homes and cars, and contributes to particulate pollution in the area, which includes nearby high school.

The DEP, during a series of inspections over the past few years, found that Neiswonger was not doing enough to control the dust. In October, regulators and the company signed a consent order and agreement that requires Neiswonger to install water spray bars at emission points, run road sweepers and water trucks to prevent limestone dust from leaving the site, conduct daily emission and odor inspections, and apply for an air quality permit that would be specific to the site’s operations.

As is typical in southwestern Pennsylvania, the underground limestone mine will share the land with other extractive industries, including 20 gas wells, and several coal seams. Neiswonger will establish a 150-foot boundary around the gas wells to prevent mining within that radius.

Neiswonger operates another underground limestone mine in Garrett, Somerset County. The company is also involved in demolition work, including the dismantling of Century III Mall in West Mifflin.

First Published: January 29, 2025, 9:47 p.m.
Updated: January 30, 2025, 6:26 p.m.

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Neiswonger Construction, which is part of the Century III mall demolition project (shown here in March 2024), got the go-ahead earlier this month for an underground limestone mine in Washington County.  (Lucy Schaly/Post-Gazette)
Lucy Schaly/Post-Gazette
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