Dr. Kevin Foye, P.E CTI and Associates, Inc. and UW-Platteville Alum spoke to students as a part of the Engineering Seminar Series about the I-99 Corridor Acid Rock Drainage Remediation project in Pennsylvania that began in the early 2000’s. At the time, Foye was a lead engineer and project manager. His team joined the project in 2006 and production ended in 2009.

I-99 is a north-south interstate that connects New York to the North. This area of Pennsylvania is a mountainous area with creeks and rivers in between. “The intent (of the project) was to have the I-99 travel north of State College, traverse one mountain valley to the next, and continue north,” said Foye. When construction began on the road, there were two cuts made. These cuts exposed limestone native to the area and, shortly after, construction was halted.

Foye’s team was brought in on the project because the limestone native to the mountains in question contained iron pyrite (fool’s gold). In the unoxidized state, this mineral is generally stable. However, “as soon as you expose that to water and air, the oxygen is going to convert it into other sulfate species.” As these new species dissolve, they become acidic and remove other metals which then contaminate both ground and surface water, posing a big environmental problem. The exposed rock was covered with PVC and the removed rock was transferred to an area and contained in plastic to stop the acid rock run off from getting worse and contaminating the water of surrounding areas. Eventually, the temporary excess rock was moved to a landfill.

Foye’s group was brought in to help determine how to get a permanent cover to stay in place on the slope and protect it from damage. Each site had water treatment sites to catch run-off from the cuts and was designed to catch the water and treat it before it reached the creeks surrounding the site.

Another area, east of the previously mentioned cuts, lay the Large Buttress and T-54 area. This site had previously been disturbed, causing the slope to start moving in on the cut. The rock removed from the cuts later, had been moved there to stabilize the slope. Only after this rock had been moved was it discovered that it was contaminated, creating a second acid rock run-off problem area.

Foye and his team had many areas of this highway that they needed to construct covers for the immovable rock. Some challenges they countered were subsurface conditions, geomembrane installation, protection layers, and cover support. The team implemented various techniques before reaching the final solution. Some included drag lining and laser scanning. Ultimately, they used an excavator to knock down loose parts and fill in low parts to create a smooth surface to work on. They then placed a subgrade geomembrane layer, a non-woven textile plastic to cushion certain areas and another layer of barrier geomembrane textile. In the end, all areas were covered with either grass, or Astro 57, a three-quarter inch nominal stone.

Foye left students with some advice as well as his story. He said, “Starting out as an engineer, it’s very easy to not know what you don’t know. That being said, there is a lot to gain at the beginning of your career from talking to these other professionals and getting a sense for what they do. That was a big lesson learned from this project,” said Foye.

This lecture concluded this year’s Engineering Seminar Series. They will return next academic year.