Will removing a dam ultimately destroy a bridge in Allentown’s Lehigh Parkway?
The Wildlands Conservancy has city approval to remove the dam in the Robin Hood section of the Parkway.
It is one of nine dams the conservancy intends to remove this summer from the Little Lehigh and Jordan creeks, to improve the aquatic health of both streams.
But on Wednesday night, Allentown resident Michael Molovinsky suggested City Council rule that no decision will be made to remove the Robin Hood dam until it’s certain that the bridge won’t be jeopardized.
“And if the bridge is jeopardized who will pay for it?” he asked. “Is the Wildlands Conservancy going to compensate Allentown if we lose the bridge?”
Removing the Robin Hood dam, said Molovinsky, will change the velocity of the water in the stream and the depth of its channel. He said the dam is only 17 feet downstream from the bridge.
“My concern is that it’s going to undermine the bridge piers and we’re going to end up with a closed bridge,” said Molovinsky. “If we would lose the Robin Hood Bridge, which is essentially the icon of the park, we would lose one half of the parking in Lehigh Parkway.
“It’s essential that we preserve this bridge and it’s not worth jeopardizing the bridge for what is essentially a science experiment for the wildlife conservancy. The bridge belongs to the citizens of Allentown," Molovinsky said.
City planning director Richard Young will look into Molovinsky’s contention that removing the dam will threaten the bridge.
Young wants to review Wildlands Conservancy’s report on the planned removal of the dam, to see if it includes “scour calculations on those bridge substructures. I hope they did that.”
Molovinsky doubts the conservancy did any engineering work regarding the impact removing the dam will have on the bridge.
Describing himself as an expert on the federal Work Projects Administration in Allentown, Molovinsky said the WPA built the Robin Hood bridge and the dam in 1936, as well as the nearby walls and stairs. “Although they were excellent masons, they were not bridge engineers, they were not hydraulic engineers,” he said.
“The stress on that bridge has been pretty intense,” said City Council member Peter Schweyer. “We’ve had one accident there that took out part of the railing.”
Molovinsky noted the Parkway’s Iron Bridge upstream from the Robin Hood Bridge has been closed to vehicular traffic for several years, “so now we have a bisected park.”
Molovinsky said the irony of the conservancy’s plan is that an LCA sewer line runs along the stream through the Parkway and overflows in heavy rains, putting sewage into the Little Lehigh. He said environmentalists consider removing dams a way to improve stream quality, but in this case “it’s just a token” because of that sewer line.
“There’s a limit to how much you can improve stream quality when you have periodic sewage spills,” he said. “The environmentalists are dogmatic about removing dams. It’s almost a religious vigor with them.”
Council’s parks and recreation committee will look into the issue in one of its future public meetings.
“It is a concern,” said City Council vice president Ray O’Connell. “If it doesn’t need to be done, why does it have to be done?”
What the Wildlands Conservancy calls a watershed restoration project began
five years ago. It began with getting permission from property owners, as well as obtaining state approvals and funding.
Removing the nine dams and restoring the stream banks will cost $431,000.
Most of the money --$331,000 -- came from the state Department of Environmental Protection. Another $75,000 was provided by FishAmerica Foundation and $25,000 came from American Rivers.