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CSB Cites Lack of Inspection, Repair in Spill

Monday, October 3, 2016

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The federal agency tasked with investigating chemical accidents has said that a failure to inspect or repair corroding tanks contributed to the 2014 contamination of drinking water in Charleston, WV.

The U.S. Chemical Safety and Hazard Investigation Board (CSB) announced its findings Wednesday (Sept. 28) with the publication of its final report on the massive chemical release into the area’s primary source of drinking water.

According to the investigation report, “Documentation provided to CSB after the incident bears little evidence of rigorous, formal tank inspections that would have identified potential leaks.”

Spill Event

On the morning of Jan. 9, 2014, a 46,000-gallon storage tank located at the Freedom Industries site in Charleston failed, spilling an estimated 10,000 gallons of Crude Methylcyclohexanemethanol (MCHM), a chemical foaming agent used to “wash” coal, mixed with propylene glycol phenyl ethers (PPH Stripped) into the Elk River.

Freedom site, Charleston
Photos: CSB

On the morning of Jan. 9, 2014, a 46,000-gallon storage tank located at the Freedom Industries site in Charleston, WV, failed, spilling a hazardous chemical into the Elk River, leaving residents without clean, consumable water.

In the river, the chemical flowed toward West Virginia American Water’s intake, located about 1.5 miles downstream from the Freedom site, leaving residents without clean water for drinking, cooking and bathing for up to 10 days.

On Jan. 10, Freedom was ordered to remove the contents of its 11 remaining aboveground storage tanks at the site. The contents of three other tanks, including the one that leaked, all of which contained MCHM, had already been removed and relocated to another facility.

Several months later, the CSB provided an update on its investigation, launched at the time of the incident, in which it reported finding severe corrosion damage and no evidence of formal, industry-approved inspections occurring on any of the site’s chemical storage tanks prior to the leak.

Lack of Inspections, Inspection Requirements

During its extensive technical analysis, the CSB discovered that Freedom’s MCHM tanks had not been internally inspected for at least 10 years before the January 2014 incident, the agency said in its announcement.

Moreover, the investigation found that no comprehensive aboveground storage tank law existed in West Virginia at the time of the release. However, since the incident there have been a number of reforms, including passage of the state’s Aboveground Storage Tank Act, the CSB report noted.

The bill, which requires all aboveground storage tanks in areas of critical concern to be registered with the state Department of Environmental Protection and subject to annual inspections by DEP and independent engineers, was reportedly fast-tracked after the Charleston incident.

MCMH tanks, post-incident

Three tanks containing Methylcyclohexanemethanol (MCHM) mixed with propylene glycol phenyl ethers (PPH Stripped) were the source of the CSB investigation; Tank 396 is the one that failed.

Among other requirements, the new regulations would have required the tanks at Freedom to be surrounded by an adequate secondary containment structure, as well as proper maintenance and corrosion prevention, including internal inspections and a certification process, according to the CSB.

Informal Report

CSB investigators were able to obtain a two-page report from an October 2013 informal review, which included a visual inspection summary of the three MCHM tanks, noting that they were riveted but which gave no information about their internal condition.

The report also indicated that “the tanks have been maintained to some structural adequacy,” but not in compliance with American Petroleum Institute (API) or Environmental Protection Agency standards, and that they were not suitable for petroleum or regulated products without costly upgrades.

Dated a little more than two months before the incident, that document noted that the “condition of the other tank floors is questionable.” In the report, the inspector recommended developing a schedule to have each tank completely inspected by a certified tank inspector over the next five years, according to the CSB.

Corrosion Analysis

In the CSB’s investigation, API-certified tank inspectors conducted internal and external inspections of 20-foot-diameter tanks, thought to have been constructed in the late 1930s and showing material properties consistent with tanks of that era typically used to store petroleum products.

A visual inspection of the bottom interior of Tank 396, in which the leak occurred, showed deep, isolated corrosion pitting near the shell (side) of the tank in addition to two holes on the tank floor, inspectors said. The CSB determined that the two holes, approximately 0.75 inches and 0.4 inches in diameter, were the source of the MCHM leak.

Holes, pits in tank bottom

CSB inspectors identifed corrosion pitting and holes in the floor of Tank 396; two holes in the tank bottom were determined to be the source of the chemical leak.

Similar pitting conditions were found in the other two inspected tanks.

In addition to the pitting and holes in the bottom, inspectors reported that Tank 396 showed other visual abnormalities, such as structural integrity issues and additional corrosion sites. Tank 396 had several damaged roof deck support rafters on the inside, for instance.

“The tank had isolated areas of active corrosion on the roof with some internal seeps during rain,” they noted.

Additionally, the inspectors identified that the external coating on the shell and roof of the tank was nearing the end of its useful life “as indicated by peeling and evidence of corrosion.”

Although no obvious corrosion holes were found on the roof, loose rivets or lap joints likely allowed rain to enter the tank, they said.

Metallurgical testing of cut carbon steel coupons from the affected tank was conducted to determine whether the failure resulted from damage over time, such as from corrosion, or from a sudden event, like a puncture. However, laboratory analysis by energy dispersive x-ray spectroscopy reportedly detected silicon, chlorides, iron and oxygen—consistent with aqueous corrosion.

Although Tank 396 was a closed tank, the report said, the holes identified in the roof likely allowed rainwater to enter. Moreover, analysis of the pit morphology showed that the corrosion of the holes in the bottom was initiated from the top surface of the bottom plates (i.e., internal product-side corrosion) rather than the underside/outside.

Repairs and Patches

An evaluation of the tank bottom in comparison to the tank shell indicated that the original riveted tank bottom was retrofitted with a new welded steel bottom in order to continue its liquid storage function.

Inspectors reportedly found remnants of a flexible organic liner or patch in the vessel. At some point after the installation of the second bottom, a liner of polyvinyl acetate (PVA) appeared to have been added to the bottom of the tank to patch existing holes or prevent future corrosion, the report said.

coating remnants, tank floor

During their initial examinations, inspectors noticed remnants of a flexible organic liner, later determined to be PVA, adhered to the interior surface of Tank 396’s floor, likely in an effort to patch holes or prevent corrosion, they said.

Recommendations from prior inspections of the larger of the three inspected tanks had reportedly 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, the report noted.

“Best practices discourage the use of soft 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,” the report stated.

“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,” the report noted.

Lessons Learned

The CSB is an independent federal agency charged with investigating serious chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.

The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA.

Among its final recommendations, the CSB advises that aboveground storage tank owners should establish regular inspection and monitoring.

“The unacceptable chemical contamination of the Charleston, WV, drinking water system could have been prevented had the lessons and recommendations in our CSB report been adopted years ago,” CSB Chairperson Vanessa Allen Sutherland said. “Public officials and water companies must work diligently to identify potential risks and assure that the public’s access to safe drinking water is protected.”

   

Tagged categories: Chemical resistance; Corrosion; Tank interiors; Tank roof; Tanks and vessels; U.S. Chemical Safety Board

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