June 2, 2011The City of North Miami is in south Florida, nestled between Miami and Fort Lauderdale and is the fifth largest city in Miami-Dade County. This is a geographical area where there is a major problem with water infiltration in sanitary sewer systems. Not only is the groundwater table very high/shallow, but there is a lot of rain in the summer. The distinct lack of gravity in this area also results in very high H2S levels. All these factors make for an extremely harsh underground environment.
The City had a serious utility problem with Pump Station # G — its dry well was taking on a lot of groundwater. Utility operations superintendent Phil Conti surveyed the situation and determined that the leak was at the base of the inflow pipe. Public works director Aleem A. Ghany P.E., and Conti got together with engineers to discuss the problem. They determined that the pump station was 50 years old and that ground movement had actually broken the concrete seal around the pipe and created a severe breach. This was not an easy fix as the pipe was 25 ft underground.
“Troubleshooting the leak was difficult,” Ghany said. “We are just a small city with limited resources and small crews. We first considered fixing the breach from the inside, because of the easy access, but we realized that this fix would be a temporary solution at best.”
When the pressure is coming from the outside, an inside fix would have to hold back that pressure, while an outside fix would actually use the pressure to hold the repair in place.
Ghany and Conti wanted a permanent solution, so they consulted with Epoxytec, a company they had worked with before, to design a system that would stop the water and hold up for many years to come. Together, they determined that the best solution would be to dig down on the outside of the pump station, dry up the area and fix the breach from the outside. This approach would also have to incorporate extra flexibility and toughness to the system in order to tolerate future ground movements. Ghany also wanted to do the repair in-house, using his own small crew to save money for the City.
Mike Caputi from Epoxytec commented, “When I saw the project, I was intrigued and found the situation challenging. We have products that will repair the breach, but we also needed to address future ground movement. I recommended our CPP, which is a 100 percent solid epoxy with 16,000 psi for the main repair, and then our Quick Blue, a polyurethane that has 300 percent elongation and is very tough, as a topcoat to seal in case of a crack.”
A high flexibility topcoat provides a second line of defense to the original repair. “With this system, North Miami could do the work in-house and I was sure it would hold for a very long time,” Caputi added.
The crew dug outside the pump station and repaired the breach as described above. “The products worked just like Caputi said, and there was not a drop that came through,” Conti said. “With the right training and support, North Miami’s crew completed a professional and permanent repair; all done in-house, for a fraction of the cost.”
Ghany noted, “I never fully appreciated the versatility of epoxies and urethanes as repair materials. They are truly amazing to work with. From now on, I am going to consider them first.”
Ghany makes a good point: epoxies and urethanes are much tougher and more durable than the usual materials, such as concrete and mortar and can even give steel a run for its money, especially when considering corrosion. Working with epoxies can be tricky. Someone with experience should be designing the system to avoid a failure.
“Most failures are caused by putting the wrong product on the right substrate,” said Caputi. “You don’t want to prep the substrate, which is usually the most costly part of a rehab, pay for the product, shut down your structure, to then have a failure; because, not only have you wasted all that effort and money, but now the job is even harder and more costly to repair than the original.”
In addition, Caputi stated, “The ease of the material application was an incentive to tackle the project in-house. Being that the materials were easy-to-use with simple equipment, such as a simple spatula for the epoxy, it made the job a true DIY undertaking. When applying quick cure polyurethanes, North Miami used the Epoxytec EZ-Spray system, which is a self-mixing disposable cartridge gun. This is more convenient than mobilizing expensive and complicated equipment typically needed for quick cure polyurethanes.”
The City of North Miami, like most municipalities, does not have a large work crew. The City does, however, understand the value of training and using its crew for projects such as these. With some solid support and training, its crews have continually improved their skill sets to take on more challenging projects. From the humble beginnings of simple protective painting to the complexities of a project like this, it is evident that they have developed the sophistication of their capabilities.
Ghany is quick to point out that there are still certain projects that are best left to contractors. When there are major logistical issues or hazardous conditions involved, it is best left to a contractor. Certain materials also require expensive equipment for surface prep and application. These kinds of materials should be avoided by in-house crews.
The key, according to Conti, is that the products should be: 1) safe (without VOCs solvents, etc) where possible; 2) should be easy to apply (not requiring expensive tools and equipment); and 3) forgiving (be able to handle moisture in underground structures, for example).
More and more municipalities are teaming up with manufacturers that offer the right kind of products and support services to do more of their own in-house repairs and maintenance. The result is a long-term repair and a better trained and prepared crew. All this is achieved while extending the tax dollars allocated to rehabilitation and maintenance of critical infrastructure.
Demetri Rapanos is senior vice president of sales and marketing for Epoxytec, headquartered in West Park, Fla.