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Coating Fiasco Plagues Sewage Plant

Friday, March 2, 2012

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Officials in the Newfoundland capital of St. John’s are working to repair and sue their way out of a major coating failure that has shut down a 2-million-gallon tank at a fairly new $150 million wastewater treatment plant.

 St. John's tank
Digester Tank No. 1 was shut down in December due to a lining failure. City officials say the concrete substrate was not properly prepared.

Repairs have been underway since January, but they will continue for many months and cost “multi millions of dollars” in the end, a city official says. Lawsuits will follow, the city vows, once the many contractors in the process can be sorted out and the blame affixed.

Lining Disbondment

At issue is the massive disbondment of a coating system that lined Digester Tank No. 1 at the Riverhead Wastewater Treatment Facility, a primary treatment plant that opened in mid-2009.

The long-awaited facility was the centerpiece of an initiative that began in 2004 to clean up St. John’s Harbour. Previously, sewage from the area’s three cities—with a combined population of 130,000—was discharged, untreated, into the harbor.

 Deputy Mayor Shannie Duff
Deputy Mayor Shannie Duff says repairs will cost “multi millions of dollars.”

City officials were forced to shut down Digester No. 1 in December after large strips of the multi-layer coating system were found to be peeling from the concrete structure’s interior walls.

The tank is one of two 7.5-million liter (1.98-million-gallon) structures that process solids removed during wastewater treatment.

Concrete Prep Cited

Although the repairs and investigations are still underway, the city already seems sure of the cause of the debacle.

“The problem is that the concrete was not properly prepared, so that this special liner which protects the concrete from acid … failed,” Deputy-Mayor Shannie Duff, Chair of the Regional Wastewater Committee, told CBC News.

The committee says it will certainly sue to recover the cost of the repairs, but sorting out the responsible parties will take some time.

“It’s not one contractor involved,” Duff told CBC. “There are many contractors and specialized inspectors and specialized consultants in every part of this process.”

Relying on One Tank

While the work continues, operators are relying solely on Digester No. 2 to process 65 tons of solid waste that previously flowed into the harbor each week. The facility can “operate normally” with one digester tank, officials say.

Residents have complained of smells, but officials say they are not related to the shutdown. To minimize the problem, however, operators are scheduling the processes that generate the worst odors for 4 to 8 a.m. daily.

“This has been a lengthy process for a number of reasons, including the fact that we had to retain experts to come in and inspect the tanks to determine what was causing the problem," says Duff.

“We hope that by changing our staffing hours to perform some of the process work early in the morning, we can minimize any inconvenience.”

So far, the No. 2 tank seems to be doing the job, officials say. But they are clearly waiting for the other shoe to drop.

Said Duff: “We’re assuming since it’s the same contractor, the same lining and the same process, that we probably also have a problem in Tank No. 2.”

 Newfoundland Design Associates Limited

 Newfoundland Design Associates Limited

The Riverhead Wastewater Treatment Plant was designed to keep raw sewage out of St. John’s Harbour. Tank No. 1 is marked as a circle at the facility’s western edge. 


Tagged categories: Coating failure; Disbondment; Linings; Paint application; Protective coatings; Wastewater Plants

Comment from Shane Hirvi, (3/5/2012, 5:26 AM)

Concrete can be such a tricky substrate to work with, especially if you choose not to follow the written instructions of the manufacturer and the specification. The genesis of the most extreme problems, when dealing with a concrete substrate, occur when a proper moisture barrier has not been installed prior to the placement of the concrete. Mitigating moisture vapor transmission should be the single most important thing an engineer or specifier should be concerned with on projects like these. One of the several things that confuses me, in reading this story, is this quote: “There are many contractors and specialized inspectors and specialized consultants in every part of this process.” So if there were so many consultants and inspectors how is it possible to skip one of the most common causes for failure in coating/lining concrete substrates--adequate surface preparation. Any inspector/consultant worth his/her salt should have a fundamental understanding of an acceptable degree of surface prep on these common substrates. I have worked on several of these removal and reapplication projects where substantial failures have occured and when you find a failure on this grand a scale you will find several other steps that have been skipped as well. When the most fundamental steps are skipped you have to wonder what else has been skipped.

Comment from Shane Hirvi, (3/5/2012, 5:27 AM)

If the required surface prep wasn't done according to the spec or techncial data sheet; was the concrete allowed to cure sufficiently prior to overcoating, was there a bond breaker used on the concrete that was left over prior to coating, what was the ph of the concrete, was any moisture teting completed e.g. anhydrous calcium chloride tests, relative humidity tubes, moisture meters, plastic sheet tests? To what ICRI/CSP degree was the surface prep required? Was exposed aggregate required or just a sweep blast? How spotty is the adhesion? Was there any evidence of laitence or efflorescence? Were the bug holes and irregularities filled with a compatible sack coat/surfacer as the liner system? Was the adhesion of the sack coat/surfacer adequate to coat over? Where does the failure('s) exist? Is this a miltiple coat system? Was this your standard blast, fill bug hole, cant strips on the 90 degree corners, cracks routed and filled, epoxy primer, high build elastomeric, epoxy, polyurea liner? Did the prime coat blush prior to being overcoated? What were the overnight temps? Was some sort of data logger employed to gather ambient conditions around the clock? What was the ph of the prime coat? Were these products applied in declining temperatures? Was the pot life of the product exceeded? Was the material properly mixed? Was this liner spray applied with bad equipment? Was there evidence of the concrete outgassing in the liner system applied? I am always curious to see the inspection packages provided in situations like these. When I worked on the contractor side I probably didn't document as much as I should. But, since I started an inspection company a couple of years ago I firmly believe that inspection packages need to include photographic and video documentation that detail every step along the way. If you know now that it is a surface prep problem you should have known that the surface prep was a problem when the first coat of paint went on and somebody should have stopped the project or at suggested a conference call with the manufacturer or owner to figure a way through the problem. So the multiple contractors didn't see a problem with the surface prep, the consultants and inspectors didn't see a problem with the surface prep. Seems to me that there are systemic problems associated with this project and not just with the surface prep. In situations like these I always question officials who want to engage in litigation prior to knowing all the facts. I have seen too many people who boldly express an interest in litigation get bitten in the butt before all the facts are known. Hopefully their specification is in order--covering at least the few items I have mentioned. Hopefully there is an intact moisture barrier...

Comment from ivor williams, (3/5/2012, 6:45 AM)

I agree there was an obvious lamentable lack of pre inspection which is typicalthrough peer pressure from the contractors

Comment from Thomas Hill, (3/5/2012, 7:53 AM)

What was the coating system? What was name brand of the coating? did the Manufacture have a tech rep. on site?

Comment from Mary Chollet, (3/5/2012, 10:08 AM)

We will certainly follow this issue and make additional information available as we get it.

Comment from Jerry Trevino, (3/5/2012, 12:49 PM)

Liner / coating failure was very obvious, and as per the previous comments, very little info is provided. On many occasions, plant owners or large general contractors push coating contractors to perform the work regardless of environmental conditions. In addition many contractors do not understand the dynamics of concrete structures. Concrete is not rocket science, however, in some cases it can be very complex. Some coatings / liners have a very narrow window of application conditions of which can lead to successful applications, especially with isocyanates curing agents. The writer does not specify what type of products where specified or the conditions of their applications so it is very interesting to find this major failures, however, one can only guess at what the cause of failures was. We coat / line thousands of underground concrete and masonry structures where hydrostatic pressure, 100% humidity, and very corroded concrete is involved. This is a challenge.

Comment from David Mattingly, (3/5/2012, 4:55 PM)

Not all substrates have a moisture barrier installed. Anytime you are you are dealing with concrete structures especially underground you will have moist and damp concrete which means the product selected should be moisture tollerant such as the poly-amines for example. Also the application should be performed only after a NACE accredited inspector or equal with actual field experience with concrete coatings and surface prep has signed off that it is ready. Actual cure time must be insured on the host substrate material such as a minimum 28 day standard on Portland Cement. My experience is that a lot of time and money is invested into writing a specification , only to award the contract to the lowest bidder and no qualified inspection is performed as each step is followed as per the specification and verified prior to taking the next step in the application procedure. So many specs are written by cut and paste froma steel substrate spec and many contractors have attempted concrete applications when they have primarily worked mainly on steel. The coating only adheres as a result of the surface preparation performed and the overall success of the application is a result of a contractor that has experience with concrete coatings, plural component equipment, and history with the selected manufacturer's product all in combination with an onsite inspector that signs off on every aspect of the specification and makes sure that it is followed.

Comment from Stephen Pinney, (3/5/2012, 6:21 PM)

Almost always, the most probable cause for these failures can be theprized and in most cases proven. In this case, there in far from enough information presented in this write up to even speculate as to the cause.

Comment from Glenn Summers, (3/5/2012, 10:00 PM)

Comments from all are legitimate, but I find Stephen's and Jerry's to be on point. We deal with this condition on a daily basis and I've got money on moisture vapor emissions as the cause. Unless concrete on a tank such as this is Stabilized prior to a coating being applied, you are inviting a failure. A tank wall must be sealed to prevent moisture vapor from traveling through the matrix! Internal chemistry allowed to travel out to the backside of a coating or anything being absorbed into this concrete is a recipe for failure!! Someone dropped the ball on this, Big Time!! A review of the Specification would be a starting point and an inquiry about an RPR on site would be all telling. Yes, Jerry, you are correct "it's not rocket science", but it is concrete and they are all different.. I hope we see more information on this tank? Would be interesting to see the fix?

Comment from Jerry Trevino, (3/8/2012, 3:47 PM)

We have lined sewer manholes that were made up of brick and mortar, and also precast that are located in lakes, some are in creeks and swamps. The inside of these manholes look like modern shower heads, water infiltration of hundreds of gallons per day. We have successfully lined these structures and provide a 5 year labor and material warranty. It takes special technicians to do this. In addition, concrete is always used to resurface the interior of structures especially brick structures.. We line with epoxy the next day. If a NACE inspector was involved he/she would not allow the epoxy lining the next day. We do this all the time and we do not have failures. So sometimes the conventional schools of thought of waiting 28 days for concrete to cure before lining is not feasible. We have thousands of structures to proof that. Underground concrete structures never have a vapor barrier. There is moisture on both the outside of the structure and the inside. Like said previously they are a tricky.

Comment from Don Day, (3/13/2012, 10:44 AM)

The structure should have been tented from the start and slowly cured per temporary HVAC systems from within and without before any attempts at lining were pursued.-especially given the climate of the area not withstanding the efficacy of the sealing products and systems. I am sure the citizens would sleep better knowing their investment would result in a structure projected to last 80 to a 100 years. It is a flipping mess as it stands.

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