Rehabilitation of Lift Station, North Miami Public Works Department – concrete lining

City of North Miami Public Utilities Department– North Miami, FL, USA
Structural re-build of concrete with calcium aluminate mortar with an epoxy lined top coat.
March 2010

The City of North Miami and Epoxytec co-consulted to determine a solution for the concrete rehabilitation of one of the City’s many lift stations. Lift stations are used to raise the waste water up to a level that will allow it to gravity feed into the sewer line. Because the waste water builds up over time in the wet well before it is pumped down, the H2S gases and waste take its toll on the concrete of the lift station causing extreme deterioration. This deterioration can cause structural failure and potentially lead to leaks and exposure to the environment….

If the concrete is not protected properly, the gases in the form of hydrogen sulfide will completely corrode and destroy the concrete. This extreme environment has to be taken into consideration to determine the best coating system necessary to combat the effects of corrosion. Epoxytec offers free consultation for their clients who may not understand these factors and will always help to find the best solution for their clients needs.

In this instance, the concrete required a complete structural re-build and then needed lining with a high performance epoxy liner. For the re-build, Epoxytec suggested a calcium aluminate mortar, Epoxtec Mortartec Aluminate, which is a high density sewer grade mortar that provides an added layer of protection to the underlayment in the event the underlayment is exposed in the future. It also proivdes a solution where the existing structure requires enhancement of 10,000psi plus compressive structural integrity for resurfacing or rebuild.

Surface preparation is always important for any coating application. The substrate must be completely rid of poor concrete and contaminants that might have settled in the concrete. This surface was prepared by sand blasting to NACE No.6/SSPC-13, which removed all contaminants and gave the concrete an ideal profile to coat over.

Once completed, Epoxytec’s Mortartec Aluminate can be troweled or sprayed onto the surface, depending on the contractor’s capability. The contractor here, sprayed the Mortartec Aluminate for a build up of nearly 4″ in some spots where the rebar was exposed. In order to build up that high, the mortar needed to be sprayed in 2 passes, another one after the first coat cured in approximately 12 hours.

Although the calcium aluminate can be used for a back-up protective layer, Epoxytec encourages a higher performance liner should always be utilized. With the presence of such high amounts of hydrogen sulfide and contaminant build- up in lift stations, Epoxytec suggested the use of Epoxytec Uroflex, which is a proven urethane-modified epoxy liner used for immersion in such environments that will help with premium protection for the top lining. The Uroflex, because of its urethane finish, will also be easier to clean when dealing with grease build-up concerns. The high gloss of urethane will allow any build up of contaminants such as fats, oils and grease to be easily removed with your everyday pressure washer.

To replace a structure of this size just wasn’t an option within budget, but with the help of Epoxytec, a budgeted and improved solution of trenchless rehab would provide more than adequate protection from gases and allow for easy clean-up for future evaluations and repairs that may be needed in this lift station. This coating system will protect the concrete for years to come and provided the City of North Miami with a money saving solution that will allow them to continue their efforts in maintaining their underground infrastructure in order to prevent major complications from happening in the future.

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