State College

‘50-year storm’ caused Oak Hall washout: Regional officials, developer detail steps toward prevention

A crew works on the entrance area of Oak Hall Regional Park, along Linden Hall Road, July 8, 2014.
A crew works on the entrance area of Oak Hall Regional Park, along Linden Hall Road, July 8, 2014. CDT photo

The June 25 storm that caused a downhill slide of water and rocks in Oak Hall is being described by environmental officials as a “50-year storm.”

In response, officials from College Township, Centre Region Parks and Recreation, Centre County Conservation District, the state Department of Environmental Protection, Leonard S. Fiore Inc. and others met Thursday at the Oak Hall Regional Park construction site to discuss measures to prevent future slides.

Nearly 2 inches of rain fell in an hour during an intense storm that quickly doused the area, including the construction site. Rocks and muddy water flowed down the park driveway, piling up on Linden Hall Road.

“Measures on construction sites are designed for 10-year storms,” said Sam Seltzer, project manager for Fiore, the site general contractor. “Those really heavy deluges are a problem.”

A 50-year storm is described by the U.S. Department of Agriculture as a rainfall event that has a 1-in-50, or 2 percent, chance of occurring in a year.

“We had some terrible washouts last June,” said Ron Woodhead, director of Centre Region Parks and Recreation. “We thought the plans and measures that were taken had fixed that. (The rain) proved it had not. It never should have happened.”

As of June 30, according to Woodhead, contractors had performed emergency repairs and restoration to return the area to normal. Residents also were being helped with property cleanup. All the stone that washed across Linden Hall Road has been replaced along the side of the road in order to slow potential water flow.

Officials discussed a number of solutions to prevent future slides, according to Woodhead, including topography grading and additional ways to support water restraint. Immediate measures to be taken, Centre County Conservation District resource conservation Supervisor Jim Coslo said, include installing ditches to aid in runoff to the stormwater management pond and installing pipes along the outer perimeter path.

A super silt fence — filter fabric reinforced by a wire fence — also has been added, Seltzer said.

DEP and PennDOT plan to discuss possible improvements to runoff on the road as an added protection for residents, according to an email by DEP community relations coordinator Daniel Spadoni.

Contractors will focus on stabilizing the park area with vegetation as well, Coslo said.

Seltzer said the area has been seeded four times. Some seeding done in the fall died off over the winter, he said, and storms in early May and June 25 washed seeds away. The areas have since been seeded again.

“Once the grass is fully established, it will cut the runoff,” said Don Franson, College Township assistant engineer. “We’re hoping for some light rain so the grass will have time to grow.”

Revisions to the permitted design drawings from Stahl Sheaffer Engineering are expected soon, Spadoni said. The Ferguson Township-based firm is a consultant for Centre Region Parks and Recreation.

The DEP and conservation district will review and approve the revisions for future construction, Spadoni said.

“We believe this will prevent a recurrence of the flooding that occurred in June,” he said.

Stahl Sheaffer representatives could not be reached.

The park’s completion date has not changed, Woodhead said. It is still expected to open in the spring.

“I wish it had not happened,” Woodhead said. “We apologize that it did happen. Everyone at (Thursday’s) meeting did what it takes for it to not happen again.”