Officials not sure how lake at Ryerson damaged
WIND RIDGE – A little more than one year from when movement of the dam forced a complete drawdown of the 52-acre Duke Lake at Ryerson Station State Park, state officials are no closer to an answer for what caused the damage. A contractor hired by the state Department of Conservation and Natural Resources (DCNR) finished “intensive monitoring” on June 30, according to Eugene Comoss, director of the DCNR’s Bureau of Facility Design and Construction.
Now begins the long process of analyzing roughly six months of data from 30 to 40 monitoring stations around the park, according to Comoss.
“It’s going to be months (before a conclusion is reached),” Comoss said. “I can’t say if it’s going to be two or six. We have tons and tons of data we have to look at.”
The cost to DCNR for the project so far is a “couple a dollars on either side” of $1 million, Comoss said.
In January, Gannett Fleming Inc., under contract from the DCNR, drilled holes about 8 inches in diameter on the hilltop near the dam, next to the pool by the lake and also through the dam.
During the drilling, crews examined each foot of ground removed in hope of determining if the ground is susceptible to movement or shifting. Once drilling was complete, inclinometers were placed deep beneath the surface to detect and monitor movement.
The data from the core samples and the inclinometers will be combined and is currently being analyzed, Comoss said. The DCNR is hoping the data will point out a culprit for the movement that damaged the dam.
“Ideally, yes, that would be the goal, but unfortunately in a situation like this you can gather a lot of data and not come to any conclusion,” he said. “That could be part of the issue.”
Data was being collected weekly during April, May and June. Since the last reading on July 13, monitoring now is being completed at the 30 to 40 monitoring stations bimonthly, Comoss said.
The inclinometers being used are common for sites where there is interest in the movement of the earth, like along fault lines or where mudslides are prevalent. Several possibilities for the shifting are being investigated, including flood damage, mine subsidence and landslides.
During late spring, Comoss said, CONSOL Energy was mining under the west side of park and “some movement was detected during that period.” However, Comoss and DCNR officials have repeatedly said that no conclusions can be made until sufficient data has been determined to conclude a cause for the movement.
“At this point, we just don’t have enough understanding of the data to come up with a cause,” Comoss said. “We’ve ruled nothing in or out yet. We’re still neutral on cause and effect.”
At an open house in December, officials from the state Department of Environmental Protection (DEP) said that though they haven’t ruled it out, they did not believe mining was the cause, and if it were, it was an “anomaly.”
Another result of analyzing the collected data will be to quantify the total amount of movement since it was first detected.
“We’re talking inches,” Comoss said. “I think that’s where the numbers are going to be.”
The 62-acre lake formed by the dam was drawn down immediately July 28 after joint inspections by the DCNR and DEP uncovered serious structural concerns. The 1,164-acre Ryerson Station State Park opened in 1967. The concrete dam was built in 1960.
State crews removed a 100-foot-by-15-foot section of the 200-foot dam spillway in August 2005 to prevent the reservoir from refilling after heavy rains, which could further damage the structure.