City of Houston 24-Inch Cast-Iron Water Transmission Main SIPP Epoxy Rehabilitation

In 2022, Houston Water (Texas) began the rehabilitation of its potable water infrastructure. This included the rehabilitation of a critical 24-inch cast iron potable water main. The pipe was highly corroded with several “kicked” joints, or areas where the pipe had shifted from its alignment. At the risk of failure, the owner issued a pipe repair project and awarded it to a local experienced contractor.

Project Background

The contractor already working on the project was hired to install seal patches. The deteriorated pipe’s interior had heavy tuberculation, otherwise known as mounds of corrosion forming rust. Concerns grew over the tuberculation and kicked joints. Houston Water was hoping to install seals in the subject section of the pipe but looked for another rehabilitation method due to its interior condition.

As a result, the owner turned to Spray in Place Solutions (SIPS), a member of Warren Environmental’s (Warren) Approved Applicator Network. The owner was interested in contracting SIPS due to their strong history of dealing with problematic situations and providing rehabilitation expertise. SIPS recommended a spray-in-place pipe (SIPP) epoxy rehabilitation method and used this section of pipe as a demo opportunity. Fortunately, the owner was already interested in exploring advanced rehabilitation technology and agreed. The agreement resulted in rehabilitating a section of the pipeline that the previous contractor passed on and the demonstration was a huge success.

In the process of awarding the project, the owner was convinced that the SIPP application of a high build epoxy reduced the amount of time pipes would be out of service, with the bonus of extending its estimated service life by 75 years. In addition, SIPS’ crew had been providing SIPP services for over 14 years, completing over 100 projects and lining over 500,000 linear feet. Houston Water understood that SIPS didn’t just bring a temporary fix, but a long-term, structurally enhancing solution that would restore and protect the pipe for years to come.

Scope of Work

The project’s scope included the surface preparation and spray-in-place lining of a 24-inch cast-iron water main with Warren’s 100% solids, 301-01 NSF certified epoxy. The 301-01 epoxy applied also meets the requirements of reference standard NSF/ANSI/CAN 600. This single coat, non-hazardous epoxy is tested and certified by the NSF and WQA against NSF/ANSI/CAN 61 for potable water contact.

SIPS performed closed circuit television video (CCTV) video inspections of the pipe’s condition and consulted with the owner before addressing the pipe. To fix and prepare the substrate to receive the epoxy coating, the pipe required extensive cleaning with specifically designed equipment including multiple pull-throughs of drag scraping and water jetting. After cleaning, SIPS performed another CCTV inspection to review the condition of the cleaned pipe. It confirmed the pipe was in a highly deteriorated condition. Before coating, the kicks had to be grouted via a robotic system. Once the pipe’s surface was prepped, SIPS applied approximately 3 mm (120 mils) of Warren’s high build epoxy in a single coat using SIPP technology. This high build factor is important as previously, epoxies were applied in a thin coat acting as more of a barrier than a structural enhancement. In this type of application, thin coat epoxies had a reputation for wearing off over time.

Coating the water main with Warren’s 301-01 NSF certified epoxy enhanced the structural integrity of the existing infrastructure as a Class III liner per AWWA’s Structural Classifications of Pressure Pipe Linings, with strength modules exceeding ASTM 1743 Class IV classification numbers. The epoxy sealed cracks, prevented leaks, and eliminated future growth of restrictive tuberculation to extend its engineered service life by an estimated 75 years. In addition, the epoxy’s zero volatile organic compound (VOC) and aquatic safe formula per ASTM E729 made for a safe and environmentally-friendly rehabilitation method.

Located in a congested downtown metropolitan area, a small construction footprint was critical to minimizing disruptions. To the project’s advantage, SIPS didn’t require a large working space to perform their scope. The SIPS crew operated out of two six-by-six-foot pits, minimizing congestion in the thoroughfare, and limiting community disruption. These access points were spaced up to 650 linear feet (LF) apart. The SIPP epoxy rehabilitation provided flexibility because the applicator’s pit could be small and off to the side of the road to mitigate the amount of lane space required. This meant that SIPS could operate within the shoulder of the busy road instead of the middle, decreasing traffic concerns and eliminating the need for traffic control services.

This type of rehabilitation only requires 5% of the space and 15% of the time of an excavation and replacement project—an added benefit for the owner and the surrounding communities. The SIPP epoxy rehabilitation method provided greater flexibility than the alternative cured-in-place pipe (CIPP) method because CIPP applicators have a larger footprint and need to internally cut open lateral connections using robotically controlled cutters. The SIPP method has even greater advantages over CIPP and pipe bursting because it does not close off lateral connections, all the way down to ¾ of an inch. This is one of the reasons municipalities and water utilities prefer the SIPP process. As the robotic spray system passes a lateral connection, the sprayed-in-place epoxy adds strength at the junction.

The crew completed the project in just four days in comparison to what normally would have taken four to six weeks for open cut replacement of the pipe. The SIPP rehabilitation method with Warren’s epoxy translated into major cost and schedule savings to benefit the owner. Once the application was complete and the epoxy cured, the owner performed tests to bring the pipe back online into their system.

The adhesion tests boasted excellent results. On the 24-inch cast-iron pipe, the result was 1360 psi with dolly #1. The cement mortar adhesion tests also displayed great results. All three pulls resulted in a 100% cohesive failure of the cement mortar, not the epoxy bond:

1. 50 mm pull – 360 psi
2. 50 mm pull – 383 psi
3. 30 mm pull – 460 psi

Project Challenges

The SIPS crew overcame any challenges encountered to deliver the client a successful project, regardless of the circumstances. This project was completed in July during one of the hottest spells in the Greater Houston area in years. It was so hot that the pipe reached an internal temperature of 97° F even buried six feet down.

Despite the heat, the SIPS crew applied Warren’s epoxy using their spin cast technology equipment while keeping the project on schedule. Warren’s epoxy brought several advantages to the project, including the ability to be applied in challenging environmental conditions including humidity and extreme temperatures. SIPS’s long history of applying Warren’s epoxy by SIPP technologies in a broad range of conditions gave them the experience to deal with such issues.

Project Successes

Thanks to their expertise and the proven success of the Warren high build epoxy product, SIPS provided an effective, sustainable solution to address unexpected problems and extend the pipe’s service life. Using the SIPP epoxy rehabilitation method, SIPS delivered a project that normally would have taken four to six weeks in just four days, significantly reducing the environmental impact to the community. The owner was pleased with the results and hopes to complete more rehabilitation projects using this trenchless technology method in the future.

For project-specific questions, please contact Peter Vita, Executive Vice President – Business Development at Spray in Place Solutions (SIPS).

Special thanks to the City of Houston (Houston Water), SIPS, mc2 Civil, and Lockwood, Andrews & Newnam for their collaboration in this case study!