Bronx Zoo Heating Loop Rehabilitation- Trenchless SIPP and HydraWrap Solution

HydraWrap® (Fiber Reinforced Polymer)

Market
Power & Utilities

Challenge
The Bronx Zoo in New York City operates a gas-fired plant that generates electricity and circulates excess heat and hot water through a 6-inch fiberglass reinforced plastic (FRP) pipeline to provide heating across its buildings and exhibits. This closed-loop system, spanning thousands of feet, had begun losing water and pressure due to leaks at the joints. Constructed years ago in approximately 20-foot sections, the FRP pipes were connected with couplings secured only by glue, which had degraded over time. The widespread nature of the leaks made spot repairs impractical, and trenching the entire loop was not an option due to the zoo’s busy operations and sensitive environment. A comprehensive rehabilitation was required to restore system integrity with minimal disruption.

Engineered Solution
The zoo selected Spray-In-Place Solutions to apply spray lining, using an epoxy liner to rehabilitate the interior of the FRP pipeline. After lining, the reassembled sections were fortified externally with HydraTech’s HydraWrap system, a carbon fiber and epoxy composite applied to couplings and fittings.

Scope
The project covered thousands of feet of 6-inch FRP pipeline circulating hot water throughout the Bronx Zoo. Work was conducted in segments, with excavation pits dug approximately every 500 feet to access the pipe. The interior cleaning process involved sanding the entire pipe, focusing on reducing the size of glue joints, followed by the application of the SIPP epoxy liner. Each lined section was reassembled using pre-cut FRP pipe sections, joined to the existing pipe with fiberglass repair couplings and high-pressure glue. After lining, the reassembled sections were fortified externally with HydraTech’s HydraWrap system, a carbon fiber and epoxy composite applied to couplings and fittings. The HydraWrap process involved applying epoxy to the pipe exterior, saturating carbon fiber fabric with wet-out epoxy, and wrapping it around the repair sites for added strength. Both solutions were chosen for their durability under high temperatures and pressures, ensuring long-term performance for the zoo’s heating loop. During the zoo’s busy summer months, the project was paused. This long-term project was completed in about 2 years with a small crew that averaged five people. After each 500-foot section was lined, it underwent a 150psi hydrostatic test, with the fully reassembled system tested at 150psi for 2 hours upon completion.

Solution
The Bronx Zoo needed a robust solution to eliminate water loss and pressure drops in its hot water heating loop, caused by deteriorating glue joints in the FRP pipeline. The SIPP epoxy spray lining effectively sealed the interior of the pipe, addressing leaks and restoring system integrity, while the exterior application of HydraTech’s HydraWrap carbon fiber and epoxy system reinforced the couplings and fittings for added durability. Rigorous 150psi hydrostatic testing confirmed the rehabilitated loop could handle operational demands without issue, passing a 2-hour test across the entire system. This dual interior-exterior approach, executed with minimal excavation and disruption, provided a long-lasting, efficient fix tailored to the zoo’s unique operational constraints, ensuring reliable heating for its facilities and exhibits.