Sinkholes are a problem that has plagued Palmyra over the years and cost the borough an estimated $4 million to $5 million in damages since the late 2000s.
Palmyra Borough Council’s latest effort to address sinkholes begins later this month with a new study to gain fresh insight. The goal is to coalesce existing information from past studies with data from a new one to gain a better understanding of what’s happening beneath the borough and drive mitigation efforts toward the more problematic areas.
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“As we’ve had these sinkholes over the years, we have had geophysical studies done on the ground, so we have pockets of these studies from all over the borough, and I thought it sure would be nice to take all that information that we already have and then fill in the gaps with new information that we don’t know yet so that we end up with an entire map of the underground conditions of the borough,” said Palmyra Borough manager Roger Powl. “That way we can see what’s going on in different parts of the borough.”
Powl added that conditions differ around the borough, and having one coordinated map to reference and serve as their field guide will assist borough officials with sinkhole mitigation.
“We would know where we have more problem areas than others, so we could then direct our efforts – for any kind of mitigation efforts – in the future,” he noted. “So that is the whole idea behind it.”
The new six-month to one-year study, which will be conducted by engineering firm ARM Group LLC of Hershey, is a continuation of a recent aggressive and proactive approach to address this issue before more problems arise.
ARM Group has performed similar studies in the past, so Powl said it made sense to utilize the same company for the new study, which will cost $220,000 and be paid through American Rescue Plan Act funding that was distributed by the federal government during the COVID-19 pandemic.
“The idea behind this study is to be proactive,” said Powl. “We sometimes have sinkholes develop in areas where we’ve had sinkholes before, so we can go back to that data and see what we did before so we can do that again. Having that data will be invaluable to addressing better information faster to make quicker repairs.”
The study will occur in two parts with the first being the creation of the map that tracks underground conditions across the nearly two square miles that comprise Palmyra Borough.
“The second part is doing stormwater models for the drainage areas in each part of the borough,” said Powl. “It will be like a GIS-based stormwater model so that we can input different levels in the amount of rain that falls so that we can see how it impacts the different areas of the town, which sounds really cool. That will help us identify areas that are still flood prone, where water lays for periods of time.”
This will permit borough officials to address spots where water pools due to improper drainage.
“In a sinkhole area you don’t want water laying around and infiltrating into the ground,” added Powl. “This will help us identify other areas in the borough where we need to capture that water and move it somewhere to get rid of it.”
The study, he noted, will have a long shelf life because geophysical conditions and other underground factors change very slowly.
“They’ve said that the study will never expire, it doesn’t have a shelf period,” he said. “Dr. Seaton at ARM is the geologist that we always work with, and he has said that subsurface conditions don’t change very quickly. He said, at minimum, the study will be good for 50 years before there would be any kind of significant changes in any part of the town.”
Powl said the borough has made a number of improvements over the past 10 years to address this issue, adding that this study is part of an effort to “always do better.” Past work has included drilling injection wells and locating where fissures in the rock reside.
“We’re flat here and we have ridges on either side of town, so we’re at the bottom of the bowl, which is a horrible condition to be in, in a karst geology situation with eroding limestone underneath you,” he explained. “So we’ve installed stormwater injection wells, which is a well we’ve drilled into the ground so that instead of taking water out we’re putting water in.”
The sinkhole problem has taken a toll both mentally on residents and staff and on the borough’s coffers. Powl called the sinkholes in the 300 block of East Cherry Street – which cost the borough $3 million to mitigate – a horrible situation that he hopes never happens again.
“We had to get people out of their homes, then condemn the homes and we eventually tore those homes down,” said Powl. “We then constructed a stormwater facility there, but it was a long, horrible and expensive process for us.”
He estimated that Palmyra has spent between $4 million and $5 million on sinkholes since he started working for the borough in 2007, which he said is a pretty significant sum of money for a municipality that size. By comparison, the cost of the study is a small investment in the borough’s ongoing fight to elevate problems before they occur, he said.
“I’m glad we’re able to do this because I think it is going to be a big benefit down the line,” said Powl. “I also think it will be very cool to have that information at our fingertips as soon as we need it. This should be a good thing for the borough.”
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