ALTOONA, PA (AP) Construction of a section of Interstate 99 could be delayed for a year or more as state transportation officials try to resolve acidic runoff created by crews unearthing pyritic rock, according to state officials.

The state Department of Environmental Protection (DEP) has asked the state Department of Transportation (PennDOT) for further testing on the acid rock taken from a sandstone layer at Skytop Mountain, just west of State College, and a permanent plan to curtail the acid runoff, which has threatened two trout streams and delayed construction.

Getting the needed permits is expected to take at least a year, according to a letter written by Gary Byron, an assistant regional director for the state DEP. The letter was sent July 23 to George Khoury, a PennDOT engineer overseeing the project.

The discovery of the acid runoff earlier this year has been the biggest construction setback for the transportation department since it began building the $700-million link between the Pennsylvania Turnpike and Interstate 80 five years ago. PennDOT has halted construction near Skytop, potentially delaying this year’s scheduled opening of Interstate-99 from Grays Woods to Port Matilda.

PennDOT’s contractors last year dug up between 500,000 and 1 million cu. yds. (382,277 and 76,4555 cu m) of sandstone containing pyrite, a mineral that produces sulfuric drainage when exposed to air and water.

The rock had been safely sealed in geologic formations, but is now exposed to rainwater and possibly groundwater that drains into Buffalo Run and Bald Eagle Creek, state officials said.

According to Byron’s letter, state environmental officials want constant monitoring of areas where the acid rock is being stored and any new areas. The new fill sites should have liners and leak detection systems, state environmental officials said.

State environmental and transportation officials said some of the permit reviews may overlap. But the process will still take time because some steps, such as public comment periods, can’t be streamlined, said Daniel Spodoni, a spokesman for the state DEP.

“Given the urgency of the situation, we hope we can mutually find a way to streamline and shorten the suggested permitting process,” Khoury said.

State environmental officials have also suggested PennDOT drill into the piles of rock to determine how much of the acid-forming pyrite is present and its sulfur content, an indication of how acidic runoff could be.

If PennDOT doesn’t do the drilling, state environmental officials said they will assume the piles are mostly made of the acid rock and require them to be chemically neutralized.

The discharge has been temporarily neutralized with 10,000 lbs. (4,536 kg) of soda-ash briquettes as it washes into the stream and has built a ditch to collect acidic run-off from an area where the rock is being stored.

But state environmental officials issued a violation notice to the PennDOT after finding elevated acid levels in waterways.

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