Fifty years ago this week, the remnants of Hurricane Agnes drifted north through the Susquehanna River basin as a tropical storm and saturated the entire watershed with wave after wave of torrential rains. The storm caused catastrophic flooding along the river’s main stem and along many major tributaries. The nuclear power station at Three Mile Island, then under construction, received its first major flood. Here are some photos taken during the climax of that flood on June 24, 1972. The river stage as measured just upstream of Three Mile Island at the Harrisburg gauge crested at 33.27 feet, more than 10 feet above flood stage and almost 30 feet higher than the stage at present. At Three Mile Island and Conewago Falls, the river was receiving additional flow from the raging Swatara Creek, which drains much of the anthracite coal region of eastern Schuylkill County—where rainfall from Agnes may have been the heaviest.
Pictures capture just a portion of the experience of witnessing a massive flood. Sometimes the sounds and smells of the muddy torrents tell us more than photographs can show.
Aside from the booming noise of the fuel tank banging along the rails of the south bridge, there was the persistent roar of floodwaters, at the rate of hundreds of thousands of cubic feet per second, tumbling through Conewago Falls on the downstream side of the island. The sound of the rapids during a flood can at times carry for more than two miles. It’s a sound that has accompanied the thousands of floods that have shaped the falls and its unique diabase “pothole rocks” using abrasives that are suspended in silty waters after being eroded from rock formations in the hundreds of square miles of drainage basin upstream. This natural process, the weathering of rock and the deposition of the material closer to the coast, has been the prevailing geologic cycle in what we now call the Lower Susquehanna River Watershed since the end of the Triassic Period, more than two hundred million years ago.
More than the sights and sounds, it was the smell of the Agnes flood that warned witnesses of the dangers of the non-natural, man-made contamination—the pollution—in the waters then flowing down the Susquehanna.
Because they float, gasoline and other fuels leaked from flooded vehicles, storage tanks, and containers were most apparent. The odor of their vapors was widespread along not only along the main stem of the river, but along most of the tributaries that at any point along their course passed through human habitations.
Blended with the strong smell of petroleum was the stink of untreated excrement. Flooded treatment plants, collection systems overwhelmed by stormwater, and inundated septic systems all discharged raw sewage into the river and many of its tributaries. This untreated wastewater, combined with ammoniated manure and other farm runoff, gave a damaging nutrient shock to the river and Chesapeake Bay.
Adding to the repugnant aroma of the flood was a mix of chemicals, some percolated from storage sites along watercourses, and yet others leaking from steel drums seen floating in the river. During the decades following World War II, stacks and stacks of drums, some empty, some containing material that is very dangerous, were routinely stored in floodplains at businesses and industrial sites throughout the Susquehanna basin. Many were lifted up and washed away during the record-breaking Agnes flood. Still others were “allowed” to be carried away by the malicious pigs who see a flooding stream as an opportunity to “get rid of stuff”. Few of these drums were ever recovered, and hundreds were stranded along the shoreline and in the woods and wetlands of the floodplain below Conewago Falls. There, they rusted away during the next three decades, some leaking their contents into the surrounding soils and waters. Today, there is little visible trace of any.
During the summer of ’72, the waters surrounding Three Mile Island were probably viler and more polluted than at any other time during the existence of the nuclear generating station there. And little, if any of that pollution originated at the facility itself.
The Susquehanna’s floodplain and water quality issues that had been stashed in the corner, hidden out back, and swept under the rug for years were flushed out by Agnes, and she left them stuck in the stinking mud.
Early October is prime time for hawk watching, particularly if you want to have the chance to see the maximum variety of migratory species. In coming days, a few Broad-winged Hawks and Ospreys will still be trickling through while numbers of Sharp-shinned Hawks, Cooper’s Hawks, Northern Harriers, and falcons swell to reach their seasonal peak. Numbers of migrating Red-tailed and Red-shouldered Hawks are increasing during this time and late-season specialties including Golden Eagles can certainly make a surprise early visit.
If you enjoy the outdoors and live in the southernmost portion of the lower Susquehanna valley, Rocky Ridge County Park in the Hellam Hills just northwest of York, Pennsylvania, is a must see. The park consists of oak forest and is owned and managed by the York County Parks Department. It features an official hawk watch site staffed by volunteers and park naturalists. Have a look.
If you’re a nature photographer, you might be interested to know that there are still hundreds of active butterflies in Rocky Ridge’s utility right-of-way. Here are a few.
To see the daily totals for the raptor count at Rocky Ridge Hawk Watch and other hawk watches in North America, and to learn more about each site, be certain to visit hawkcount.org
To avoid any theft of the limelight from the country’s miscreants who are currently using the year’s most worrisome virus strain , SARS-CoV-2, as a cover for wealth realignment and self-promotion, this week’s 41st anniversary observance of the 1979 nuclear accident at Three Mile Island has been cancelled. The planned community reenactment festivities will not be held this year.
We will not be recreating the run on the stores or the hoarding of toilet paper, ammunition, food, booze, smokes, prophylactics, and pet treats. Though not sanctioned by the official event, undocumented pharmaceutical distributors will still be vending product to the self-medicated at the usual locations, reminiscent of 1979 commerce.
The Friday night disco get-together featuring authentic vintage 8-track tape music is called off, which of course means that commemorative T.M.I.-2 anniversary t-shirts will not be available for sale this year. If you were thinking of attending, be assured that you can find audio of the Bee Gees’ “Stayin’ Alive” on the internet and play it three times just like it would have been repeated at the dance. You can find other event favorites online too, including the Trammps’ “Disco Inferno”.
The annual “evacuation excursion” to the mountains of Pennsylvania led by the gasoline and gunpowder gang to terrorize the countryside with four-wheel drive trucks, all-terrain vehicles, fireworks, and random weapon discharges is scrubbed. The traditional trash burning in the fire pit on Saturday afternoon and weenie roast scheduled for Saturday night are nixed. Regular participants will have to inhale and ingest their dose of dioxins somewhere else this year.
The consortium of local college drama clubs will not be presenting their popular horror play “It’s Gonna Blow Up”, featuring authentic rumors and supposition from actual news media reports about the 1979 accident. Mock briefings featuring posturing politicians trying to patronize their donors without endangering their reelection prospects will not be held and have been eliminated from the slate of activities—they seem too familiar to be of any interest. A slapstick comedy interpretation of bureaucrats trying to assume authoritarian power to implement an emergency plan that never existed has been postponed until a future event.
Speakers due to share their insights at this year’s gathering have been asked to return next time. We’re pleased that each has agreed. It’s a splendid roster of advocates both for and against nuclear energy, each of whom has shamelessly abandoned their integrity to sustain a do-nothing career that protects them from ever breaking into a sweat. As usual, these appearances will be scheduled as the final feature of the weekend to assure a prompt dispersal of the crowd.
We hope to see you all sometime soon. In the meantime, please remember to use the euphemism “essential workers” when referring to the expendable labor that is out there protecting public health and assuring that everyone can keep shopping. We as a nation would hate for them to realize their worth—they may expect to be better compensated.
Late this afternoon, despite a cold bone-chilling rain, news media and crowds of onlookers gathered along the Susquehanna shoreline upstream of Three Mile Island at the small town of Royalton to catch a glimpse of the removal of a downed aircraft from the river. Back on October 4, a single-engine Piper PA46 Malibu was on the final leg of an approach to runway 31 at Harrisburg International Airport when it lost power. The pilot and passenger were uninjured during the emergency “splashdown” in the shallow water just short of the runway.
At 12:07 P.M., E.D.T. today, forty-five years and eighteen days after being commissioned into commercial service on September 2, 1974, the Three Mile Island Nuclear Generating Station’s Unit 1 reactor was shut down for the final time. There will be no refueling. There will be no more electricity furnished to the grid by the plant. It is henceforth a user, not a producer, of energy.
It had been quite a few years, decades actually, since Uncle Tyler Dyer and I had visited the State Museum of Pennsylvania, formerly the William Penn Museum, in Harrisburg. Several days ago we decided to stop by to see what’s new.
I was fussing around with the official “Life in the Lower Susquehanna Watershed” camera while walking slowly down an entrance corridor when I heard Uncle Ty exclaim from up ahead, “Hey man, that’s my T-shirt!”
There it was, neatly screen-printed on luxurious , but functional, blended cotton and polyester, just like the one Uncle Ty wore forty years ago. This priceless gem was no iron-on job. It was the real thing, just like Coke, but a little bit more expensive.
Uncle Ty said that, other than his own artistic creations, his T.M.I. T-shirt was the only one he wore during the summer of ’79. It even had spots of hardened wax in the fabric around the belly section where his candle had dripped during one of the anti-nuclear energy protest vigils he attended.
I wasn’t so certain, I thought he had a few others in his rotation back then. All those corporate beer brand and pop music group T-shirts were really popular. And “Grease”, Uncle Ty really liked Olivia Newton-John back then. He had a “Grease” T-shirt for sure. Then I remembered, and I reminded him, “You were wearing a Buck Tractor Pulls T-shirt back then, weren’t you?” I was sure of it, nice artwork of a hopped-up farm tractor on the front and “See You at the Buck” across the back.
“No way man,” he retorted, “There’s no way I went down there to waste a Saturday night with that gasoline and gunpowder gang. I would have sooner spent a Saturday night getting a tooth worked on by an angry intoxicated dentist!”
Oh well, everybody has there own idea of a good time.
We’re beginning to worry about Uncle Tyler Dyer. It’s been almost a month since a tornado descended from an eastbound cloud that first passed by Three Mile Island, and from him we’ve heard not a word about it. And the rainfall totals during the past year, well above normal and record setting, but not a peep from him about it. The floods too, and the gusty thunderstorms that either seemed to strike only our town, or would instead let us high and dry while passing off to the north or south. For forty years, from Uncle Ty’s point of view, these phenomena were all attributable to those towers down at Three Mile Island. He would say, “Man, you know the lightning in that thunderstorm was terrible because of T.M.I. You know that, don’t you?”
If you happen to live in the lower Susquehanna valley, you’ve probably heard comments like that at the local diner, taproom, or gathering of family and friends. Many are offered by good-humored folk, in jest, to enliven the conversation. It makes a chat about the weather a bit more exciting. Then to, there are those who became extraordinarily suspicious of the nuclear facility at Three Mile Island after the accident. To them, any deviation from the status quo must be caused by those big towers down there. Even if they don’t fully believe what they’re saying, it matters that they don’t miss the chance to get in a jab, even if it’s a glancing one. That’s Uncle Ty. He sees that plant in a different light than we do, from a different perspective. To him, Three Mile Island is the ultimate symbol of corporate evil. It’s not about the fuel used to operate the reactor. The invisible threat of radioactivity is a metaphor for the secretive operations of sinister big business. Those towers are a collection of monoliths representing greed, interlocking corporate directorships, and immunity from accountability. And no one is going to change his mind.
If you remember reading, watching, or listening to news reports in the weeks and months following the accident at Three Mile Island, you recall stories from farmers and other residents living in the vicinity of the plant who described diverse irregularities in the health of domestic animals and in populations of wildlife there. For some, these reports left a lasting impression of conditions near the site of the accident.
The Pennsylvania Department of Agriculture, the Environmental Protection Agency, and the Nuclear Regulator Commission conducted an investigation into these reports. Because the levels of radiation released during the accident were barely above background levels, it was going to be difficult to detect any changes in animals or plants that could be definitively linked to operations at Three Mile Island or the accident there.
Upon evaluating cases for which sufficient data had been preserved or animals were available for examination, investigators failed to find any animal deaths, injuries, diseases, deformities, or stillborn young caused by known effects of ionizing radiation exposure. Anemic conditions would have been expected in animals exposed to significant doses of radiation, but cases of anemia were not found. For the animal fatalities reported, their numbers generally fell within the expected mortality rates for breeding, raising, and keeping the species involved. For the cases examined, no link could be made to exposure to ionizing radiation or byproducts released during the operation of T.M.I. or the accident at Unit 2. Instead of a pattern of mortality and illness consistent with ionizing radiation exposure, investigators instead found a wide-variety of problems considered common to animal keeping.
During the investigation, some of the causes for domestic animal afflictions were identified and, when possible, proper remedies were recommended. Animal husbandry errors, accidents, and disease accounted for most of the deaths, disabilities, and reproduction failures in domestic animals. The occurrence of stillborn or deformed pets was attributed to a variety of diseases and developmental problems that are frequently associated with the symptoms described by pet owners. Poultry eggs that failed to hatch were believed to be infertile or were not maintained at the proper temperature during incubation. Many of the physical ailments in adult dairy cows were traced to mineral deficiencies in the feed. Cases of rickets were found among steers at two different farms. Supplements mitigated these abnormalities in the involved herds. Some cows were found to be suffering from bacterial or viral infections. A few dairy animals had developed mastitis, an inflammation often caused by bacterial infection of the udders. Following diagnosis, herdsmen were able to initiate treatment. Among livestock, fertility and reproductive deficiencies were generally traced to nutritional shortcomings or disease. Those farmers needing further help troubleshooting breeding difficulties were referred to the Pennsylvania Department of Agriculture’s Diagnostic Lab.
The majority of people not living in the lower Susquehanna valley at the time paid little attention to the results of the investigations. Such reports are often lengthy and boring, not as exciting as the stories of mutants and catastrophe, and not as memorable. Naturally, the closer you lived to T.M.I., the more informed you probably were about it; you knew first-hand how life was both before and after the accident. Those living elsewhere were sometimes left with exaggerated recollections based upon those initial news stories from the scene.
While traveling some years ago, Uncle Ty was astounded by the perception folks from outside Pennsylvania had of the place he calls home. He told us of one incident in particular. Uncle Ty had gone to the South Bronx in New York City to participate in an “End the Violence” protest. Gunfire and murder were an occurrence of epidemic proportions on street corners there at the time. It turned out that the protest was a poorly attended flop. It happened to be Bat Day at Yankee Stadium, so everyone had gone there instead. During his extended lunch break, Uncle Ty struck up a conversation with a local, a likeable public safety worker who lived and worked in the South Bronx. Ty expressed some sympathy for the stressful conditions the fellow had to endure as a resident there. The guy appreciated his sentiments, but didn’t think he had it too tough. When Ty told him that his home was near Three Mile Island, the guy shook his head in pity and said, “yeah, I hear it’s pretty bad out there, all the two-headed cows walkin’ around and s…”. A guy from one of the most dangerous neighborhoods in the country felt really sorry for him. Even Uncle Ty was caught off guard by that one, but it wasn’t the last time he heard it either.
Today, Uncle Ty has us all pondering. Has he given up on Three Mile Island’s grand towers as the primary factor affecting all meteorological irregularities in the lower Susquehanna? Will we ever hear of a cooling tower induced drought again? What will he turn to? It’ll have to be something big. A causative force that no one can quite prove or disprove, mysterious enough to keep everyone guessing if he really knows something no one else knows. I wonder what it’ll be. No matter what it is, it just won’t be the same as hearing, “Man, don’t you know? T.M.I. did it.”
Gears, G. E., G. Laroche, et al. (1980) Investigations of Reported Plant and Animal Health Effects in the Three Mile Island Area. U.S. Environmental Protection Agency. Las Vegas, NV.
A sixteen year-old skinny kid driving a Ford Pinto on a Saturday afternoon in late March, 1979, might be perceived by some observers as a metaphor for the accident at Three Mile Island on that same day. When experiencing a rear-end collision, the fuel tank on these little compact cars had been known to explode, sometimes with fatal consequences. They quickly gained a reputation as a deadly hazard on the highway. Despite a recall and engineering fix to prevent the fuel tank from failing, the Pinto remained cursed, and it was henceforth looked upon as a dangerous creation of man that best be avoided if you wished to remain in good health.
For a sixteen year-old, a Pinto functioned just fine as a frugal form of transportation. So in a hideous limey-yellow one, a kid showed up at the Three Mile Island Observation Center to have a look around. There, hundreds of photographers, reporters, and journalists had gathered to try for their angle on the latest news from the accident scene. Cars and news vans lined the state road, Pennsylvania Route 441, in front of the facility. Anything that moved was photographed and interviewed. The story of the day, March 31, 1979, was the impending explosion of the hydrogen gas bubble in the Unit 2 reactor. It was the sensation that they had waited for.
By Saturday, the N.R.C. was growing concerned about the potential of a hydrogen explosion within the Unit 2 reactor. Hydrogen was formed early in the accident when hot steam in the high-temperature core reacted with the zirconium alloy in the fuel rod cladding and produced primarily zirconium dioxide and hydrogen gas. Some of this gas had been vented into the reactor containment building. There, it mixed with atmospheric oxygen and ignited when a block valve switch was operated during the late morning of day one. Operators recalled hearing a “whooshing” sound just after flipping the switch. It is believed they did not really hear the explosion or burn-off of the gas, but rather the activation of a water spray system in the building in response to it.
The N.R.C. learned on Friday of this event that had occurred two days earlier. Harold Denton wanted to know if radiolysis of water inside the reactor was producing additional hydrogen and, more critically, oxygen. Many in the N.R.C. were convinced by their calculations that enough oxygen could be produced in the coming days to make the existing hydrogen bubble explosive. Denton wanted to know for sure, and ordered a team to enlist outside help to determine a timeline for this radiolysis. He also assigned a team to determine the parameters and details for a possible explosion.
Meanwhile, this story had gone public. Upon hearing the words “nuclear” and “explosion” together in news reports, the memories of old Civil Defense promotions came back to haunt local residents, and the nation. For many, the horrific image of a nuclear explosion had been projected into their perception of the accident. An explosion similar to an atomic bomb was not possible in the reactors of the type used for energy production in the United States, but few sleep well with visions of mushroom clouds dancing in their heads. For those on the fence deciding whether to stay or go, this was it, the last straw. In response to these broadcasts, more residents left the lower Susquehanna region on Saturday. As they went out, press personnel moved in, many setting up camp at the Three Mile Island Observation Center.
At 2:45 P.M., reporters at N.R.C. headquarters in Bethesda were told that a 10 to 20 mile evacuation might be necessary as a precaution if the decision was made to attempt to force the hydrogen bubble out of the reactor.
An Associated Press story went public at 8:23 P.M. quoting N.R.C. officials as saying that the hydrogen bubble could explode spontaneously.
This information kept local Civil Defense personnel up through the night answering phone calls from the worried residents who remained in their homes. They wanted to know what to do, but the local offices and P.E.M.A. were getting very little advice from the Lieutenant Governor’s and Governor’s offices. The state B.R.P. was still providing them with radiation information, but beyond that, Civil Defense offices were on their own for the night.
Harold Denton, being informed that President Carter was coming to Three Mile Island the next day, wanted things clarified. He told his deputy Victor Stello, Jr. to solicit sources outside the N.R.C. on the oxygen issue. Stello had fielded a call from the White House at about 9:00 P.M.. In response to the A.P. story, he told a presidential aide that he did not share the concern of others at the N.R.C. regarding the production of oxygen in the reactor. He and some engineers at Babcock & Wilcox, designers of the reactor, were among the few who shared this opinion. (Also, engineers at Babcock & Wilcox analyzing the effects of an explosion, should one occur, were confident that water and steam, if maintained in the pressurized reactor containment vessel, would reduce the pressure of an explosion to within the capabilities of the vessel to contain it.)
On Sunday morning, April 1, 1979, Victor Stello made his case to Harold Denton explaining why he thought there would be no hydrogen explosion in the Unit 2 reactor. He told Denton that pressurized water reactors like TMI-2 routinely have free hydrogen circulating in the coolant. The majority of oxygen produced by radiolysis would bind with this hydrogen and simply make more water.
Just minutes before the President landed at the Air National Guard facility at Harrisburg International Airport at 1:00 P.M., the N.R.C.’s Joseph Hendrie and Roger Mattson, who had been researching the explosion question, arrived at a hangar there to present their case to Denton.
Quoted in the “Report of the President’s Commission on the Accident at Three Mile Island”, Mattson described the scene:
“…And Stello tells me I am crazy, that he doesn’t believe it, and he thinks we’ve made an error in the rate of calculation…Stello says we’re nuts and poor Harold is there, he’s got to meet with the President in 5 minutes and tell it like it is. And here he is. His two experts are not together. One comes armed to the teeth with all these national laboratories and Navy reactor people and high faluting PhDs around the country, saying this is what it is and this is the best summary. And his other (the operating reactors division) director saying, “I don’t believe it. I can’t prove it yet, but I don’t believe it. I think it’s wrong.”…”
President Jimmy Carter was no stranger to nuclear reactors, or reactor accidents for that matter. A 1947 graduate of the United States Naval Academy, Carter eventually worked his way into Captain (later Admiral) Hyman Rickover’s nuclear command. In 1952, Rickover (known as the father of the Nuclear Navy) ordered the 28 year-old Lieutenant Carter, then assigned to the Naval Reactors Branch at the U. S. Atomic Energy Commission, to the scene of a partial meltdown of a research reactor at Chalk River Laboratories in Ontario, Canada.
There, Carter led a team of 23 men. Their job was to shut down and dismantle the damaged reactor. They built a mock-up of the reactor on a tennis court and practiced taking turns performing the tasks to complete the job. This model would be used to track the progress of the project in the actual reactor. When a bolt, nut, or other part was removed in the real reactor core, it would be removed from the model as well.
Following these preparations, men suited up in protective gear and were lowered into the reactor, one man at a time, to do the work. Each man in the rotation was permitted to be in the reactor for only ninety seconds, then he was hoisted back out. During every one of these short journeys to the core, each worker, including Carter, received a dose equivalent to a year’s worth of allowable radiation today. Carter’s urine was radioactive for six months afterward.
President Carter’s earlier experiences in Rickover’s Navy, particularly at Chalk River, gave him exceptional familiarity with conditions arising from the accident at Three Mile Island in 1979.
Following the briefing of the President and Governor, Stello, Hendrie, and Mattson went back to the N.R.C.’s temporary office to try to rectify the oxygen and explosion problem. After consulting with some additional outside sources, including Westinghouse and General Electric, they had the answer. The hydrogen bubble would NOT explode. It was 3:00 P.M.
At just before 4:00 P.M., there was a new push from the N.R.C. in Bethesda to start an evacuation within two miles of the plant. Chairman Hendrie informed them—there is NO danger of an explosion. The teams in Bethesda would find concurrence with Stello, Hendrie, and Mattson by later that evening. On Monday, the N.R.C. trickled out the good news, but would not outright admit that their calculation errors had caused a near panic. Instead, they claimed that they had been a little too conservative in their estimates.
Shortly following the President’s visit, or during it, the hydrogen bubble began dissipating. The public wasn’t made aware of it until the following day, Monday, April 2. By then, operators for the utility reported that it was nearly gone. No direct action had been taken to get rid of the bubble, its disappearance was mysterious, yet welcome.
Nobody knows how many people evacuated the lower Susquehanna valley during the accident. It is generally believed that over 100,000 left for at least the weekend. Some communities, such as Goldsboro, a small town overlooking Three Mile Island’s reactors from the York County side of the Susquehanna, may have experienced evacuation rates approaching ninety percent. In the majority of areas more distant from the plant, the rate was well below fifty percent. Most of those who left their homes began returning as schools reopened during the mid-week.
During that first weekend, the press was angling to get officials to speculate on the probability of the occurrence of a catastrophic core meltdown. No one had realized that the meltdown had already happened, on day one. It was determined in 1987 that in excess of half of the more than 100 tons of uranium oxide fuel had melted during that first morning. In 1989, 20 tons of molten fuel was discovered to have flowed to the bottom of the reactor vessel and solidified into a slag-like mass there. Fortunately, Unit 2’s pressurized reactor vessel had kept the catastrophic core meltdown contained within its five-inch-thick steel structure.
Crews on Three Mile Island worked faithfully to manage gases and continue the cooling of the reactor core. Cold shutdown of the reactor (reduction of temperatures to below the atmospheric boiling point of water) would take another week, the full cleanup and de-fueling would take more than a decade. Unit 2 was placed in monitored storage in 1993, and will be fully decommissioned simultaneously with the Unit 1 reactor when the latter is permanently taken out of service.
On the day of his visit to Three Mile Island, President Carter signed executive orders activating the Federal Emergency Management Agency (F.E.M.A.), a new entity formed to house Civil Defense and disaster preparedness, with the latter of the two becoming the greater focus of its mission.
Forty years after his visit to Three Mile Island, Jimmy Carter, at age 94 ½ years, had become the longest-lived President in American history. We wish he and Rosalynn many more happy years.
Finally, what shall we think of the risky travels of a sixteen year-old? Was the bigger hazard the act of being inside a Ford Pinto while driving to Three Mile Island on Saturday, March 31, 1979, or was it the act of being at Three Mile Island itself on that afternoon? We’ll let you decide.
Forman, Paul, and Sherman, Roger. 2004. Three Mile Island: The Inside Story. Web presentation based upon Smithsonian National Museum of American History exhibit, as accessed March 28, 2019. https://americanhistory.si.edu/tmi/index.htm
Kemeny, John G., et al. 1979. Report of the President’s Commission on the Accident at Three Mile Island; The Need for Change: The Legacy of TMI. U. S. Government Printing Office, Washington, D.C.
Milnes, Arthur. January 28, 2009. “When Jimmy Carter Faced Radioactivity Head-on”. The Ottawa Citizen.
It was forty years ago today. The civics teacher had a hook on stick, and he was under orders to use it. He was trying his best to draw the water-stained paper blinds down over the tall old single-pane glass windows that covered the length of the outer wall of his west-facing room. You understand, this was not something he was doing of his own accord. He was a veteran educator, one of those teaching the offspring of his students from a previous generation. He was no tyrant merely wanting to deny his pupils the distractions of a beautiful spring day outdoors. He was ordered by the coffee cup brigade in the front office to close the windows and draw the shades. The safety of the students is at stake!
As his third class of the day entered the room, the instructor enlisted the help of a couple of taller students to try to get some of those stubborn window coverings pulled down. No luck. Class would commence with blinds up, down, and in between. Today’s topic: the dangers of nuclear energy. As usual, it was something of an open discussion of current events. All points of view were encouraged.
Few noticed the town fire siren howling away during the first minutes of the oratory. That happened every once in a while, so it wasn’t so remarkable. The class transformed from debate and dialog to a practical demonstration a little while later when fire trucks began circulating through the streets near the school broadcasting muffled incoherent warnings of some sort to the residents of adjacent neighborhoods.
Within moments there was clamor in the hallways as several students were banging locker doors and making off with their wares. Soon the old classroom phone that hung as a decoration on the wall near the doorway began making an obnoxious noise. What does this mean? What should we do? It never made a sound before. The dedicated educator walked over and picked up the receiver. He timidly said, “Hello?” He listened carefully, acknowledging the caller from time to time, then he said, “O.K.” After hanging up the little-used device, he walked over to a startled girl and simply told her to gather things and report to the office, one of her parents was here to pick her up.
The old sage walked back to the lectern and just stared around at the quiet faces in the room , not a word was said until the phone rang again. He looked over toward a skinny sixteen year-old kid, a late-bloomer, seated near the half-shaded windows and quietly said, “Mr. C—, you have duties to perform, don’t you?, you may leave.” Then he turned to answer the phone for the second time. The skinny kid departed the school building posthaste.
Since the beginning of the accident, operators of the Unit 2 reactor had been spending a considerable share of their time and effort coping with noncondensible gas in Unit 2’s coolant system. Not only was there growing concern that a build-up of Hydrogen around the top of the reactor core was preventing coolant from reaching the fuel assemblies, but gas was causing problems in other portions of the cooling system as well. One component in particular, a make-up tank used to store water that is used as needed to increase the volume of coolant in the primary cooling system, was of concern in the early morning hours of Friday, March 30, 1979. Its relief valve had activated at least once due to excessive pressure. Gauges read that gases had displaced all of the water from the tank.
Just before 7:00 A.M., operators decided to open a valve to purge the radioactive gases from the make-up tank into the waste gas decay tanks where it is collected and stored by design. The venting began at 7:10 A.M. Aware that a header leaks in this system, and that any leaked gas will enter the auxiliary building and be discharged to the atmosphere from its vent stack, a helicopter monitoring flight is requested to collect samples above the plant and its perimeter. Almost an hour into the venting process, at 8:01 A.M., a radiation reading of 1,200 millirems per hour (mr/hr) is measured 130 feet directly above the vent stack. A reading of only 14 mr/hr was taken along the boundary of the facility site. This was an expectable set of readings. During a short venting procedure involving the make-up tank on the previous day, a sampling flight measured 3,000 mr/hr fifteen feet above the stack .
Confident that they can now keep gas accumulation in the make-up tank under control by “puffing” it clear on a regular basis, and again having the ability to use the make-up tank to equalize coolant levels, the process is a success. The operators are on to the next step as they strive to get the reactor into a cold shutdown.
Friday’s memorable troubles resulted from a series of inaccurate reports of the 1,200 mr/hr reading taken above the auxiliary building vent stack. For the next ninety minutes, the 1,200 mr/hr figure shot like lightening through a chain of phone calls that left Three Mile Island and made its way through state-level and county-level offices and found smooth sailing through the Nuclear Regulatory Commission (N.R.C.) and landed right in the middle of meeting of the latter in Bethesda, Maryland.
But first, at 8:45 A.M., a Telex message arrives at the N.R.C.’s Incident Response Center:
“The seal return to the makeup tanks was causing excessive gas pressures in the makeup tank which was directed to the waste gas decay tanks which were full. The waste gas tanks were being released to the stack. Pennsylvania Civil Defense was being notified by Licensee.”
This errant message indicates that the highly radioactive contents of the waste gas decay tanks, which are NOT full, can be expected to vent from Three Mile Island with some regularity for the foreseeable future. At 9:00 A.M., the N.R.C.’s Lake Barrett carries the Telex into a meeting of the agency’s Executive Management Team (E.M.T.). Alarmed by the news, they ask Barrett to calculate what an off-site radiation dose might be with the anticipated releases. Ironically, Barrett arrives at a figure of 1,200 mr/hr for a person at the site boundary, a value exceeding the Environmental Protection Agency (E.P.A.) threshold for evacuation of sensitive persons. Within minutes, the E.M.T. receives a phone call from Karl Abraham, the N.R.C. press officer at Governor Richard Thornburgh’s office in Harrisburg. He’s on the speakerphone and wants to know if the reports of 1,200 mr/hr readings above the “cooling towers” are true. This is the first the E.M.T. has heard of the 1,200 mr/hr number at the site, and because it matches Barrett’s calculation for off-site releases from full waste gas decay tanks, they assume it to be an off-site number and forget that Abraham was asking a question. Following a discussion, Harold Denton, Director of Reactor Regulation, orders that a recommendation for evacuation out to ten miles in the direction of the plume be given to the Pennsylvania Emergency Management Agency (P.E.M.A.), the state-level Civil Defense agency. This recommendation is delivered at 9:15 A.M. Unfortunately, the location of the 1,200 mr/hr reading was not verified beforehand.
In Harrisburg, Margaret Reilly of Pennsylvania’s Bureau of Radiation Protection (B.R.P.) was trying to verify the N.R.C.’s reasons for the evacuation recommendation. There was some ire because P.E.M.A. received the recommendation instead of the B.R.P., or, better yet, Governor Thornburgh himself. Information available to Pennsylvania agencies showed no reason to evacuate.
Dutifully acting on the N.R.C.’s recommendation, the state notifies Dauphin County Civil Defense, telling them to expect an evacuation order from the Governor within five minutes. The mild temperatures on this Friday were due to a steady wind from the southwest, putting communities in Dauphin County within any possible plume from the Three Mile Island Unit 2 facility. It appeared that communities in Dauphin County, including the city of Harrisburg, would comprise the majority of the evacuation zone. Fire companies, municipal officials, local Civil Defense directors, and others were alerted. Announcements on Harrisburg’s WHP radio advised citizens within five miles of T.M.I. to make preparations and gather supplies for a possible evacuation. The cat was out of the bag.
Governor Thornburgh was very cautious, possessing an understanding of the risks to the public that an evacuation order could cause. He would later be quoted, “In Pennsylvania, P.E.M.A.’s role is to manage the emergency, not to recommend evacuation. P.E.M.A. mentality (during the T.M.I.-2 accident) was akin to being all dressed up with no place to go—leaning forward in the trenches. We had to be careful about that attitude.” Thornburgh knew that ordering an evacuation meant moving patients in health care facilities, possibly at great risk to them. He knew too, that evacuation meant putting helmets in the street—the National Guard.
The Bureau of Radiation Protection had checked the site and conferred with the N.R.C. in Bethesda and was convinced that an evacuation was not necessary. Because of the public broadcasts, phone lines were jammed, so nuclear engineers from B.R.P. are hurriedly en route to the Governor’s office and P.E.M.A. to deliver the facts in person. It’s 9:45 A.M.
At the same time in Bethesda, the E.M.T. had learned that the 1,200 mr/hr reading was not from off-site, but from directly above the vent stack. They were also made aware that the venting had not come from the waste gas decay tanks, but from the make-up tank. And finally, they learned that the waste gas decay tanks were not full, but were accepting gases from the make-up tank as designed. By 10:00 A.M., they rescinded their evacuation order—about the same time that Governor Thornburgh countermanded it.
Too late. By this time people were getting out of town. Schools were overwhelmed as parents showed up to pull their children out of class, one by one at first, then in droves. Sirens were sounding. Broadcasts were telling people to close blinds and windows and remain indoors. The Three Mile Island Unit 2 accident was now the biggest news event in the nation.
Governor Thornburg went on WHP radio at 10:25 A.M. to broadcast a message to residents, attempting to rectify some of the contradictions of the morning. Within the hour, President Carter would call the Governor and assure him of the White House’s full support. He told the Governor that he was sending Harold Denton to the scene forthwith. Denton was to “take charge of the site on behalf of the federal government”.
At local Civil Defense offices in the lower Susquehanna valley, there was a continuous flow of telephone calls from concerned citizens, some of them very frightened. They wanted to know what to do. The ball was rolling, and people with families were becoming more and more inclined to leave.
A skinny sixteen year-old volunteer walked into a community fire station in a small town about six miles from Three Mile Island at about 11:00 A.M. There, the town’s mayor and Civil Defense Director were conferring inside the “Civil Defense office”, a coat closet with a desk and ashtray. The phone was in the adjacent closet, which had more desks and ashtrays. The discussion centered around responsibilities for ordering an evacuation. Following the events at the federal and state level earlier in the morning, it was unclear who had the authority and responsibility to order an evacuation.
The scene was tense, the cigarette smoke was rolling out of the closet for hours as phone calls were made and the chain of command was clarified. Evacuation plans were being worked out in case they were needed. Moving patients from hospitals and nursing facilities was a particularly difficult planning challenge to be tackled. The cloud would persist as the chain smoking continued for the next couple of days. (And those plaid double-knit leisure suits with Flintstones neckties—wow!—it’s a good thing there were no photographs taken of this scene.)
Elsewhere inside the fire station, the sixteen year-old lad and some other volunteers collected the radiological monitoring supplies from the blue and white Civil Defense rescue truck. After gathering some fresh batteries, they ventured outdoors and set up a small monitoring station. Lungs clouded by all the chain smoking inside could be clarified out there. Several metering devices were employed in an attempt to detect radiation. The crew remained at their post through late afternoon, keeping a sharp lookout for the fashion police and enjoying the balmy spring air. It was easy work and no radiation was detected.
Following further consultation with the N.R.C., the Governor held a press conference at 12:30 A.M. He advised pregnant women and pre-school age children to leave the area of a five-mile radius around Three Mile Island. He closed the schools and the few students still in the classrooms were on their way home—or to the mountains for an unscheduled spring holiday.
Harold Denton would arrive at Three Mile Island during the mid-afternoon. Denton found inadequate facilities and communications (no cellular telephone in 1979!) at the T.M.I. Observation Center building where other N.R.C. personnel had set up temporarily. This facility on the east shore of the Susquehanna overlooking the plant was now overrun by scores and soon hundreds of reporters, so Denton set up his base in a home offered by a Met-Ed employee just across the street. He set up his temporary office in the living room, complete with a direct line to the White House. Denton would have his work cut out for him; the hydrogen gas bubble was becoming an increasing concern and the press was storming over the possibility of a catastrophic meltdown. The situation was serious—there would be no BINGO in the fire halls this weekend.
Thanks Mr. H—, wherever you are!
Kemeny, John G., et al. 1979. Report of the President’s Commission on the Accident at Three Mile Island; The Need for Change: The Legacy of TMI. U. S. Government Printing Office, Washington, D.C.
Rogovin, Mitchell, et al. 1980. Three Mile Island: A Report to the Commisssioners and the Public. Nuclear Regulatory Commission.
Forty years ago, at just about 4:01 A.M. on Wednesday, March 28, 1979, the Unit 2 reactor at the Three Mile Island Nuclear Generating Station on the Susquehanna River at Conewago Falls “scrammed”—the control rods automatically dropped into the reactor core to stop fission. This occurred in response to the automatic opening of the “Pilot-Operated Relief Valve” (P.O.R.V.) on the pressurizer, a tank designed to prevent the boiling of water in the primary cooling system loop that transfers heat energy from the reactor core to the steam generator. The P.O.R.V. activated when steam in the top of the pressurizer tank was compressed by water that was expanding as it increased in temperature while circulating within the primary cooling system loop.
During normal operating conditions, water in a non-nuclear “secondary loop” is pumped through tubes within the steam generator where it absorbs energy from the hot water in the primary cooling system loop. The heat converts the water in the “secondary loop” to steam for turning the steam turbine and making electricity. At about 36 seconds after 4:00 A.M., a set of pumps “tripped” and stopped feeding water through the “secondary loop” to the steam generator. Within seconds, Unit 2 ceased making electricity. Starting automatically as a failsafe were a set of three “emergency feedwater pumps”, designed to reestablish water flow to the steam generator. A reactor operator verified their start just fourteen seconds after the main pumps “tripped”. Unfortunately, the operator did not notice the panel lights indicating that valves were closed on each of the two lines supplying the steam generator from the emergency pumps. With the “secondary loop” shut down, heat from fission in the reactor core began accumulating within the steam generator and the primary cooling system loop, leading to the P.O.R.V. activation, and the reactor’s “scramming”. The “scram” triggered control rods to drop in 69 tubes among the 36,816 uranium oxide fuel rods to absorb neutrons and stop the chain reaction fission process in the core of Unit 2.
Following the reactor’s “scramming”, an equipment malfunction occurred when the P.O.R.V. failed to automatically close as designed after reducing pressure within the pressurizer vessel on the primary cooling system loop. Unbeknownst to anyone at the time, this equipment malfunction initiated a small “Loss Of Coolant Accident” (L.O.C.A.). Fortunately, the reactor’s High Pressure Injection system (H.P.I.) automatically began pumping water into the primary cooling system to compensate for the loss of coolant through the stuck valve. Even though fission was no longer generating heat, the decaying radioactive materials within the reactor still require continuous cooling until the reactor is brought to cold shutdown.
(Note that the dropping of control rods to effect an automatic scramming immediately reduced the heat output in the core to 160 megawatts, or about 6% of that generated while the fission reaction was occurring. Normally, the heat release rate after the first hour would drop to about 30 megawatts and, over next three hours, to 20 megawatts. This is still a lot of heat—enough to severely damage the fuel assemblies in the core. Twenty megawatts is equivalent to the heat release rate from a big wind-driven apartment fire. It is critical that an uninterrupted flow of cooling water circulates through the core to prevent damage. See the “Riverside Firemen’s Retreat” page on this site to learn how heat release rate applies to the work firefighters do.)
Enter human error, enhanced by insufficient training, missing protocols, and a poorly designed control panel (including, at one point, 100 alarms in simultaneous operation!), and soon the small L.O.C.A. was converted into a destructive meltdown event. An illuminated light on the reactor control panel indicated that a signal had been sent to close the stuck P.O.R.V.; it did not indicate the valve’s position—open or closed. It would be two hours before operators were aware of the stuck valve and would take corrective action to close the back-up “block valve” to stop the leak. Had the H.P.I. system continued operating autonomously throughout this two hour period, no damage to the reactor core would have resulted. However, operators began overriding the emergency H.P.I. system by throttling the flow of 1,000 gallons per minute back to less than 100, hoping to maintain a certain water level in the reactor. This action was inspired by an operator’s doctrine encouraging them not to let the primary cooling system ever “go solid” (fill completely with water). For “extended periods” during the first day of the event, the H.P.I. was throttled back or shut down. It was during these periods that much of the core of the reactor was exposed, resulting in its meltdown.
The Reportof the President’s Commission on the Accident at Three Mile Island reveals how haphazard and unorganized the notifications of key persons and agencies were from the very start of the accident. The mayor of Harrisburg at the time, Paul Doutrich, first heard about the accident when he received a phone call from a radio station in Boston inquiring what he planned to do about the nuclear emergency. They had to fill him in first.
The public gained little if any confidence from clumsy and often contradictory public statements made by the plant operator, regulators, and various other government officials during the first days of the event. The oscillations between dire warnings on one hand, and assurances that there is no need to worry on the other, frightened and angered thousands of people in 1979. Memories of these awkward and inconsistent messages continue to be the dominant recollections for many residents of the lower Susquehanna region to this very day.
Here, for your entertainment pleasure, is how the media and general public first learned of the accident on the morning of March 28, 1979 (quoted from the Report of the President’s Commission on the Accident at Three Mile Island)…
“WKBO, a Harrisburg “Top 40” music station, broke the story of TMI-2 on its 8:25 a.m. newscast. The station’s traffic reporter, known as Captain Dave, uses an automobile equipped with a C.B. radio to gather his information. At about 8:00 a.m., he heard police and fire fighters were mobilizing in Middletown and relayed this to his station. Mike Pintek, WKBO’s news director, called Three Mile Island and asked for a public relations official. He was connected instead with the control room to a man who told him: “I can’t talk now, we’ve got a problem.” The man denied that “there are any fire engines,” and told Pintek to telephone Met Ed’s headquarters in Reading, Pennsylvania.”
By late Wednesday afternoon, the reports from the plant indicated that everything was under control. Day one would end with the residents of the lower Susquehanna area presuming they would hear little more of this event. Then came Friday.
Forman, Paul, and Sherman, Roger. 2004. Three Mile Island: The Inside Story. Web presentation based upon Smithsonian National Museum of American History exhibit, as accessed March 28, 2019. https://americanhistory.si.edu/tmi/index.htm
Kemeny, John G., et al. 1979. Report of the President’s Commission on the Accident at Three Mile Island; The Need for Change: The Legacy of TMI. U. S. Government Printing Office. Washington, D.C.
“Fear is the darkroom where negatives are developed.”
I celebrate alone, entering my fortieth year of fame. Everyone knows me; they’ve all heard my name. The world won’t recognize Berwick, Salem, Peach Bottom, or the place near Springfield (not the one with the donut-eating man who drools when he sleeps on the job, the real one in Montgomery County, Pennsylvania). Oyster Creek, Beaver Valley, Hope Creek, and dozens of others won’t ring a bell, but they’ll recall me with emotion or story, and often with myth as well—I’m a Nuclear Star.
I’m the ultimate thriller, generating anxiety from day one. My worldwide debut was the stuff of legend; you saw me on the news. You remember all the dramatic tension, don’t you? Like all celebrities, I blew off a little steam, had a little gas, and then everyone waited, trying to figure out what was going to happen next. But I kept things under wraps, shrouded in a fog of mystery, not a sole eyewitness to the events in my inner sanctum. Confusion reigned. There was a sense of great danger and imminent catastrophe. There prevailed a sweaty uncertainty over the threat of disaster and invisible death.
Would I melt down?
Would I blow my top?
Those iconic and sinister towers, what kind of horrid poisons pour from them to burn the sky and land?
The world needed to know. People demanded information.
Well, I know your trust in me was eroded and you felt deceived by my agents. You saw it, how they withered in the spotlight of fame while trying to protect themselves and the new Nuclear Star. The uncertainty they caused motivated many of my neighbors to leave. Many more were pushed beyond rational skepticism about me to an enduring cynicism which persists to this day. Fortunately, a genuine, competent, straight-talking communicator arrived to allay everyone’s fears with frank and understandable explanations of the situation. Then, a visit by the President of the United States assuaged the trepidations of a frightened public and provided reassurance to those who left that it was safe to return.
I want everyone to know that I had plans for a long quiet career. Then, three months into it, a handler pressed my buttons the wrong way and I’ve been in the limelight ever since. I did melt down a bit, but thanks to a timely intervention, I didn’t drop through the floor. For the same reason, I didn’t go through the roof either. You need to know that I’m no bomb. I was built to last for the long haul, and I won’t go to pieces. Remember, I’m a Nuclear Star. Oh, and those really are just big fluffy white steam clouds coming out of those towers, nothing more. It’s true.
I’m really not so scary. There’s no scheming evil little man hiding in my shadow planning the demise of the planet. Only the flies sit around rubbing their tiny hands together as they contemplate their next move, and I’ll remind you that not even one of them was hurt here.
I’m a Nuclear Star; my legacy is secured. Come look at me and feel the awe. After all these years, I continue to make nervous those who see me in person. You’ll still see the crowds and cameras outside my gates from time to time, demanding to know what kind of devious scheme is being hatched inside. I remain a central figure, but typecast as the villain. Without fail, I’m presumed to be the deleterious factor when man or nature ails. It’s not the coal-choker down the river, or the dam wall next door. It’s not the smoldering trash cookers north and south, or the sludge on the fields. It’s not the junk mixed into the food, or the spraying willy-nilly. Nor is it the filth in the water, the lazy life, or the smog in the city. It’s not the cigarette in your mouth, the synthetics in your house, the hours in your car. It’s Three Mile Island. That’s what did it. I’m a Nuclear Star.
Oh, and by the way, the plant in Montgomery County is called Limerick, in case you were wondering.
Two days ago, widespread rain fell intermittently through the day and steadily into the night in the Susquehanna drainage basin. The temperature was sixty degrees, climbing out of a three-week-long spell of sub-freezing cold in a dramatic way. Above the ice-covered river, a very localized fog swirled in the southerly breezes.
By yesterday, the rain had ended as light snow and a stiff wind from the northwest brought sub-freezing air back to the region. Though less than an inch of rain fell during this event, much of it drained to waterways from frozen or saturated ground. Streams throughout the watershed are being pushed clear of ice as minor flooding lifts and breaks the solid sheets into floating chunks.
Today, as their high flows recede, the smaller creeks and runs are beginning to freeze once again. On larger streams, ice is still exiting with the cresting flows and entering the rising river.
The events of today provide a superb snapshot of how Conewago Falls, particularly the Diabase Pothole Rocks, became such a unique place, thousands of years in the making. Ice and flood events of varying intensity, duration, and composition have sculpted these geomorphologic features and contributed to the creation of the specialized plant and animal communities we find there. Their periodic occurrence is essential to maintaining the uncommon habitats in which these communities thrive.
Is this the same Conewago Falls I visited a week ago? Could it really be? Where are all the gulls, the herons, the tiny critters swimming in the potholes, and the leaping fish? Except for a Bald Eagle on a nearby perch, the falls seems inanimate.
Yes, a week of deep freeze has stifled the Susquehanna and much of Conewago Falls. A hike up into the area where the falls churns with great turbulence provided a view of some open water. And a flow of open water is found downstream of the York Haven Dam powerhouse discharge. All else is icing over and freezing solid. The flow of the river pinned beneath is already beginning to heave the flat sheets into piles of jagged ice which accumulate behind obstacles and shallows.
It was one of the very first of my memories. From the lawn of our home I could look across the road and down the hill through a gap in the woodlands. There I could see water, sometimes still with numerous boulders exposed, other times rushing, muddy, and roaring. Behind these waters was a great stone wall and beyond that a wooded hillside. I recall my dad asking me if I could see the dam down there. I couldn’t see a dam, just fascinating water and the gray wall behind it. I looked and searched but not a trace of a structure spanning the near to far shore was to be seen. Finally, at some point, I answered in the affirmative to his query; I could see the dam…but I couldn’t.
We lived in a small house in the village of Falmouth along the Susquehanna River in the northwest corner of Lancaster County over fifty years ago. A few years after we had left our riverside domicile and moved to a larger town, the little house was relocated to make way for an electric distribution sub-station and a second set of electric transmission wires in the gap in the woodlands. The Brunner Island coal-fired electric generating station was being upgraded downstream and, just upstream, a new nuclear-powered generating station was being constructed on Three Mile Island. To make way for the expanding energy grid, our former residence was trucked to a nearby boat landing where there were numerous other river shacks and cabins. Because it was placed in the floodplain, the building was raised onto a set of wooden stilts to escape high water. It didn’t help. The recording-breaking floods of Hurricane Agnes in June of 1972 swept the house away.
During the time we lived along the Susquehanna, the river experienced record-low flow rates, particularly in the autumn of 1963 and again in 1964. My dad was a dedicated 8mm home-movie photographer. Among his reels was film of buses parked haphazardly along the road (PA Route 441 today) near our home. Sightseers were coming to explore the widely publicized dry riverbed and a curious moon-like landscape of cratered rocks and boulders. It’s hard to fathom, but people did things like that during their weekends before football was invented. Scores of visitors climbed through the rocks and truck-size boulders inspecting this peculiar scene. My dad, his friends, and so many others with camera in hand were experiencing the amazing geological feature known as the Pothole Rocks of Conewago Falls.
The river here meets serious resistance as it pushes its way through the complex geology of south-central Pennsylvania. These hard dark-gray rocks, York Haven Diabase, are igneous in origin. Diabase sheets and sills intruded the Triassic sediments of the Gettysburg Formation here over 190 million years ago. It may be difficult to visualize, but these sediments were eroded from surrounding mountains into the opening rift valley we call the Gettysburg Basin. This rift and others in a line from Nova Scotia to Georgia formed as the supercontinent Pangaea began dividing into the continents we know today. Eventually the Atlantic Ocean rift would dominate as the active dynamic force and open to separate Africa from North America. The inactive Gettysburg Basin, filled with sediments and intruded by igneous diabase, would henceforth, like the mountainous highlands surrounding it, be subjected to millions of years of erosion. Of the regional rocks, the formations of Triassic redbeds, sandstones, and particularly diabase in the Gettysburg Basin are among the more resistant to the forces of erosion. Many less resistant older rocks, particularly those of surrounding mountains, are gone. Today, the remains of the Gettysburg Basin’s rock formations stand as rolling highlands in the Piedmont Province.
The weekend visitors in 1963 and 1964 marveled at evidence of the river’s fight to break down the hard York Haven Diabase. Scoured bedrock traced the water’s turbulent flow patterns through the topography of the falls. Meltwater from the receding glaciers of the Pleistocene Ice Ages thousands to tens of thousands of years ago raged in high volume abrasive-loaded torrents to sculpt the Pothole Rocks into the forms we see today. Our modern floodwaters with ice and fine suspended sediments continue to wear at the smooth rocks and boulders, yet few are broken or crumbled to be swept away. It’s a very slow process. The river elevation here drops approximately 19 feet in a quarter of a mile, a testament to the bedrock’s persisting resistance to erosion. Conewago Falls stands as a natural anomaly on a predominantly uniform gradient along the lower Susquehanna’s downhill path from the Appalachian Mountains to the Chesapeake Bay.
The scene of dangerous tumbling rapids during high flows, the drought and low water of 1963 and 1964 had left the falls to resemble a placid scene; a moonscape during a time when people were obsessed with mankind’s effort to visit earth’s satellite. Visitors saw the falls as few others had during the twentieth century. Much of it was due to the presence of the wall. I had to be a bit older than four years old to grasp it. You see the wall and the dam are one and the same. The wall is the York Haven Dam.
The initial segment, a crib dam constructed in 1885 by the York Haven Paper Company to supply water power to their mill, took advantage of the geomorphic features of the diabase bedrock of Conewago Falls to divert additional river flow into the abandoned Conewago Canal. The former canal, opened in 1797 to allow passage around the rapids along the west shore, was being used as a headrace to channel water into the grinding mill’s turbines. Strategic placement of this first wall directed as much water as possible toward the mill with the smallest dam practicable. The York Haven Power Company incorporated the paper mill’s crib dam into the “run-of-the-river” dam built through the falls from the electric turbine powerhouse they constructed on the west shore to the southern portion of Three Mile Island more than a mile away. The facility began electric generation in 1904. The construction of the “Red Hill Dam” from the east shore of Three Mile Island to the river’s east shore made York Haven Dam a complete impoundment on the Susquehanna. The pool, “Lake Frederic”, thus floods that portion of the Pothole Rocks of Conewago Falls located behind the dam. On the downstream side, water spilling over or through the dam often inundates the rocks or renders them inaccessible.
During the droughts of the early 1960s, diversion of nearly all river flow to the York Haven Dam powerhouse cleared the way for weekend explorers to see the Pothole Rocks in detail. Void of water, the intriguing bedrock of Conewago Falls below the dam greeted the curious with its ripples, cavities, and oddity. It was an opportunity nature alone would not provide. It was all because of the wall.
Smith, Stephen H. 2015. #6 York Haven Paper Company; on the Site of One of the Earliest Canals in America. York Past website www.yorkblog.com/yorkpast/2015/02/17/6-york-haven-paper-company-on-the-site-of-one-of-the-earliest-canals-in-america/ as accessed July 17, 2017.
Stranahan, Susan Q. 1993. Susquehanna, River of Dreams. The Johns Hopkins University Press. Baltimore, Maryland.
Van Diver, Bradford B. 1990. Roadside Geology of Pennsylvania. Mountain Press Publishing Company. Missoula, Montana.