U.S. CSB illustration
Today’s release of the U.S. Chemical Safety Board report on the Freedom Industries chemical spill might seem a little anticlimactic, given how much we’ve learned about the spill and the ensuing water crisis from various other investigations. But — despite the lack of strong reform recommendations (see previous post about what I was looking for) in the draft report made public this morning — we have learned a few new interesting things, thanks to the CSB’s hardworking and expert investigators.
Here are six things the jumped out at me:
1 — How did the stuff get out of the tank — While the CSB had discussed several times before (see here and here) its theory for what happened, this draft report offers more details and makes a more compelling argument that the leak from Tank 396 was caused by what’s called “pitting corrosion” that created two holes (approximately 0.75 and 0.4 inches in diameter). The draft report explains:
Corrosion is an electrochemical reaction between a metal alloy and its environment, and can lead to degradation of structures. It can attack materials uniformly, degrading metals at an even rate across the surface, known as general corrosion. However, pitting corrosion is confined to a point or small area that takes the form of cavities, some of which can perforate through the thickness of the metal. Pitting corrosion can be difficult to detect because it is highly localized and the rate at which the depth of the pit increases is often greater than the width.
In this instance:
CSB retained a tank expert to conduct a corrosion rate analysis based on the observed pitting and the data available during the incident investigation. Although it was recognized that the corrosion rates were variable and unknown, the best reasonable assumption at the time of the study was that the corrosion rate was constant over the life of tank 396 at 12.3 mils per year (mpy, or thousandths of an inch per year, a common designation for corrosion rate) with the corrosion rate bounded between 10 and 15 mpy.
2 — How long did the spill last — While the CSB team says it’s impossible to know the exact mechanism for the leak from the tank or how long the leak was going on, their draft report does offer and estimate — 24 hours — in this section, which describes one of the ways that those two small holes in the tank might have ended up leaking:
A frost heaving effect, caused by extremely low temperatures, may have contributed to the sudden release of MCHM from the bottom of tank 396. The severe cold weather in early January 2014, referred to as a “polar vortex,” brought bitterly cold temperatures to the Midwest, South and much of the eastern and northeastern United States. The Charleston area set a new minimum temperature record of -3°F just 2 days before leak discovery.
Frost heaving occurs when the freezing of water-saturated soil causes the deformation and upward thrust of the ground surface. When water freezes, it expands. This expansion is often referred to as frost jacking or frost heaving. Freezing weather prevalent at that time of year caused the frost heaving of the soil underneath the tank, which possibly led to the flexure or movement of the tank bottom in the vicinity of the holes. The movement provided enough bending on the bottom plates to possibly dislodge the PVA material or other debris blocking flow through the bottom holes.
Once the material became dislodged, the pressure from the filled MCHM tank may have enabled the sudden gushing flow of liquid from the tank bottom, which continued at a maximum flow rate of about 11.5 gallons per minute (GPM). Approximately 10,000 gallons of MCHM had leaked from tank 396 prior to leak discovery. Based on a CSB commissioned calculation of the flow rate, a sudden tank leak would have resulted in a flow loss of 1 inch per 17 minutes. At this rate, the tank contents would have leaked through the tank holes and into the ground for approximately 24 hours (1 day) before the leak was detected.
CSB concluded that tank 396 failed due to corrosion, which ultimately resulted from poor tank maintenance and inspections not in accordance with acceptable industry standards and best practices. Despite the freezing weather condition, which may have played a role in initiating the tank leak, the lack of rigorous tank inspections by ERT and Freedom directly contributed to the MCHM leak.
U.S. CSB photo
3 — The tank may have had problems before — CSB investigators were able to determine that Tank 396 was 76 years old at the time of the spill, having been installed in 1938, when the facility was operated by its original owners, Elk Refining. The tank had a capacity of 46,200 gallons. It was 20 feet in diameter and 20 feet tall.
The draft report outlined this interesting history of this particular tank:
An evaluation of the tank bottom in comparison to the tank shell indicated that tank 396 had two tank bottoms during its service life: the original riveted tank bottom and then a 250-mil (1/4-inch-thick) (6.35-mm) welded steel bottom that was retrofitted into the tank sometime after the original riveted bottom was replaced. The original riveted bottom was likely used until it failed and then the tank was retrofitted with a new welded steel bottom in order to continue its liquid storage function. The replacement bottom of tank 396 was a welded construction using lap-welded bottom plates, which suggests the bottom was retrofitted sometime after 1945 (Figure 16).
Without original tank drawings or documentation, tank experts assumed the original tank 396 bottom lasted 25 years from its construction in 1938, and estimated its replacement took place sometime after 1963, while the site was under the ownership of the Elk Refining Company or PQS. Tank inspectors estimated, based on the post-incident condition of the tank floor, that the second bottom was at least 25 years old.
The report also explained:
During the initial examinations prior to dismantling tank 396, inspectors noticed remnants of what could have been a flexible organic liner or patch, adhered to the interior surface of the tank floor, likely applied sometime before the leak occurred (Figure 18). Analytical testing determined that the chemical composition of the material was Polyvinyl Acetate, of PVA.
CSB investigators were unable to find documentation of the PVA material applied to the bottom of tank 396, but it is possible that the material, intended to be a liner or patch, was applied during prior facility ownership when tank 396 stored hydrocarbons. While there was no evidence of welded repairs around the bottom of tank 396, investigators believe the PVA could have been applied for general corrosion prevention, or to patch a leak and return to service.
Recommendations from prior inspections of the larger tank 398 called for the application of “an epoxy sealer to the bottom 6 inches of the shell and also apply sealer onto the chime” in 1997. Another possible source of the PVA remnants was reported to be a backflow of contents from the vacuum truck post-incident that occurred in the course of emptying the tanks. However, metallographic and microscopic examinations revealed corrosion product underneath the PVA, indicating that the PVA was applied to the bottom of the tank sometime before the incident.
The PVA could have been applied to act as a soft patch or liner to prevent corrosion or leaks. Soft patches have been used for temporary roof repairs in the tank industry for years. Often, the patches are thick elastomeric polymers made from a variety of materials, including rubber, neoprene, glass cloth, asphalt, and mastic or epoxy sealing materials; the choice depends on the contents of the tank and the service conditions.
According to API Recommended Practice 575, leaks in roofs can be repaired by soft patches that do not involve cutting, welding, riveting or bolting of the steel. Best practices discourage the use of patches in lieu of permanent repairs for tank roofs, but recommend them only for temporary operations since it is known that they could be delaminated from the surfaces with a fairly high probability in an unpredictable manner. Many factors affect how well patches adhere to the steel surfaces including surface preparation, the patch material, mixing and preparation, the compatibility of the material with the product and other factors.
Also used to control corrosion, liners can be applied as coatings and have been proven to effectively prevent internal corrosion in the bottom of steel tanks. For carbon steel tanks containing hydrocarbons, water and other ions can settle out of mixtures and cause various types of corrosion, including localized metal loss or pitting corrosion. PVA is a type of polyvinyl ester that is typically used to line tanks containing water, crude oil, aromatics and solvents.
4 — Tank 397 had a hole, but didn’t leak — The CSB had previously disclosed that a second Freedom tank — Tank 397 — also had at least one hole in it. Their new report confirms that, but also explains more:
Tank 397 contained a 0.2-cm-diameter hole in the bottom in addition to deep isolated pits originating from the interior surface of the tank floor. There is no evidence that tank 397 leaked in January 2014, and the hole identified during the inspection may have been plugged with debris. Pitting as deep as 0.2 inches was identified in tank 397, penetrating through about 80% of the bottom thickness.
5 — The West Virginia Department of Environmental Protection didn’t have enough resources — Maybe this seems like not really news, given that WVDEP Secretary Randy Huffman has been pretty clear that he agrees that the Freedom Industry tanks were “under-regulated.” Still, this tidbit from a footnote in the CSB draft report is pretty interesting:
West Virginia contains more permitted Industrial Stormwater facilities than WVDEP’s inspection resources can meet. Therefore, WVDEP has committed to inspecting 10% of these facilities annually in exchange for an EPA grant. Although the list of facilities to be inspected is refreshed every year, there is some overlap of facilities year to year. Freedom Industries was never included on the list of facilities to be inspected when WVDEP began receiving this grant in 2007. Due to the limited resources available, WVDEP’s compliance strategy focuses on major facilities that discharge more than 1 million gallons per day.
In fairness, the footnote goes on:
There is an ongoing effort at WVDEP to incorporate the Zone of Critical Concern into the NPDES monitoring strategy, which may allow seemingly innocuous facilities to be included in the list of facilities to be inspected, given their proximate location to water intakes.
6 — West Virginia American Water didn’t follow its parent company’s response plan — There’s obviously a lot of argument yet to be had over exactly what the water company did, could have done and should have done to both prepare for and respond to the Freedom spill. It’s looking increasingly like those questions will be decided by a federal court jury. But this little bit of information buried deep in the CSB’s draft report was certainly of interest to folks who care about those issues. In an odd — perhaps minor way — West Virginia American didn’t follow the guidance of its parent company:
AW provides standard ICS and AW Incident Management forms to assist in documenting and managing resources and operations of the incident or event; however, WVAW did not use these forms to document after-incident and event closedown actions; rather, it relied on e-mail to capture the decision-making processes post-incident. AW policy indicates that information within these forms should be augmented at the earliest opportunity to address the risks that, because of their nature, require more detailed measures and emergency plans.
Remember that the CSB is having a public meeting tonight, where investigators will discuss their findings in much more detail. The public will get to speak and ask questions. Board members will consider the report and perhaps vote on it — or even suggest changes. The meeting starts at 6 p.m. at the Four Points by Sheraton hotel on Kanawha Boulevard. There’s a webcast available.