The Science Behind The Fish Kill

As a result of the Norfolk Southern train crash and sodium hydroxide chemical spill in the Driftwood Branch watershed there was an enormous fish kill. How many fish were killed is really hard to comprehend when dealing with so many miles of highly productive streams.

On August 5, 2005, there was a similar incident on the Cheakamus River in British Columbia, Canada. A Canadian National train derailed and spilled approximately 40,000 liters (10,500 gallons) of concentrated sodium hydroxide solution into the Cheakamus River, a highly productive river harboring resident trout and char and hosting runs of all five species of pacific salmon, as well as steelhead.

The results were devastating with the fish kill extending downstream to the ocean. An entire run of salmon coming up into the river was wiped out, along with many of the previous year's fry. The Cheakamus has a flow volume about the same as that of the Sinnemahoning Creek below where First Fork joins.

Our sodium hydroxide spill involved about four times the volume of sodium hydroxide on a much smaller stream. However, if 10,000 gallons of sodium hydroxide was so devastating on such a large stream as the Cheakamus, it's no wonder that four times that volume devastated the Portage and had harmful effects for at least 35 miles downstream, likely even farther.

To put things in perspective, the sodium hydroxide had a pH of 14, which is ten million times more basic than neutral. I estimate the flow of the Portage Creek were the chemical entered to be about 3,000-5,000 gallons per minute the day of the spill. The one tanker that was ruptured spilled its contents (16,000 gallons) immediately. It would have taken ten times this volume of good water to bring the pH down to 13.

I bring this up to show that even with the chemical entering the stream at this point and being diluted somewhat and neutralized by slight acidic conditions in the stream, the pH of the stream still would have been just below 14. The pH of the stream during the initial slug of pollution probably wouldn't have been lowered to 13 until downstream where Cowley Run joins the Portage.

Unfortunately, I have seen no DEP data taken on the initial slug of pollution. Field staff simply weren't able to reach the spill site that quickly. The field data they do have was taken during the afternoon of June 30 when the other two tank cars were still leaking sodium hydroxide at a slower rate than when the first tanker burst. That afternoon the pH of the Portage was above 12 below the spill site while the chemical was leaking at this slower rate.

I would have to imagine that Friday night when the pollution slug was first traveling through the Driftwood Branch, the stream's pH was 11 to 12 (10,000 to 100,000 times more basic than neutral).

All of this is just my best educated guess, but I wouldn't doubt that it is too far from the truth. Although how high the pH actually was in the streams when the highest concentrations of pollution were first moving through may not be known, its effects on our fish population are no secret.

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Hundreds of thousands, if not millions of fish were killed by the sodium hydroxide spill throughout the lengths of Portage Creek, the Driftwood Branch, and Sinnemahoning Creek. Near the crash site conditions were so basic and the pH was so high that fish would have died instantly with severe chemical burns to their skin and gills. The chemicals also would have burned any waterfowl in the stream. I have heard of one first hand account of dead waterfowl, but there were likely others killed that were not seen due to the remote location of the spill.

As the pollution traveled farther downstream and its pH lowered to 12 (100,000 times stronger than neutral), death to fish would no longer be instantaneous. These were likely the conditions Friday night at the bottom of the Portage and at the Driftwood Branch below Emporium when the pollution was first traveling through. The chemical would have taken longer to kill the fish. It would have begun damaging their gills, causing hemorrhaging and eventual suffocation after about fifteen or twenty minutes exposure.

These were likely the conditions Friday night when many eyewitnesses viewed fish literally jumping out of the water to try to escape the caustic conditions. Eventually gill damage was so bad that the fish suffocated and died, putting an end to their painful suffering.

Farther downstream as the sodium hydroxide was diluted somewhat more and more neutralization occurred the pH likely lowered to around 11 or 10 (10,000-1,000 times stronger than neutral), the same damage occurred to gills, except it was a much slower process. Many fish were able to survive the pollution for several hours, only to finally succumb to the gill damage caused by the high pH.

Under these conditions the few fish that were able to survive faced equally deadly trials later. They had their immune defense system compromised in that their protective slime layer was damaged by the basic conditions. This led to various bacterial and fungal skin infections. In the days following the pollution several individuals witnessed seeing surviving fish with fuzzy white fungus growing on their bodies. Many of these fish died as a result of their first line of immune defense, their protective slime layer, being compromised.

Eventually, likely somewhere on the lower Sinnemahoning Creek, the pH dropped down to 9 and was no longer as deadly to fish. Although they were still being somewhat stressed, these conditions were no longer lethal.

Besides the high pH, another factor contributing to the toxic nature of this spill was all of the metals that were dissolved by the extreme basic conditions. The caustic spill leached many toxic metals out of surrounding soils. These metals are naturally found in our soils in very low concentrations. Among the metals detected in contaminated seeps leading from the spill site were cadmium, arsenic, molybdenum, aluminum, selenium, manganese, and numerous other metals. Iron was leached in the highest concentrations of any metal.

In addition to these effects, there are many substances in our streams that are found in low concentrations. At normal pH's these substances are not toxic. However, under highly acidic or basic conditions many of these very low concentrations of substances are actually lethal. One example of this is ammonia.

All of these factors had a hand in contributing to the terrible environmental disaster that occurred on our County's streams on June 30 and July 1.