Trenchless for Gas Infrastructure - Spring 2025
The transfer hose with inverted liner being inserted into the pipe.
In the heart of urban Baltimore, a critical 42-inch cast iron gas main was successfully rehabilitated in under three weeks using the STARLINE® Cured-in-Place-Lining (CIPL). Baltimore Gas and Electric (BGE) chose the trenchless lining solution to avoid the high costs, extensive disruption, and complex permitting associated with full pipe replacement.
— Thomas Nestoras, Chief Operations Officer, Progressive Pipeline Management
—Edward Gravely, Senior Project Manager, BGE Gas Program Management
PROJECT: STARLINE® CURED-IN-PLACE-LINING OF 42” CAST IRON MAIN
LOCATION: BALTIMORE, MD
CLIENT: BALTIMORE GAS AND ELECTRIC
CONTRACTORS: PROGRESSIVE PIPELINE MANAGEMENT (PPM), MILLER CONSTRUCTION
DATE: FALL, 2024
PROJECT BACKGROUND
A 42” cast iron main in urban Baltimore had been repaired over 75 times with internal clamps/mechanical seals. The large diameter original main, a critical gas source, dated back to the 1900s. Buried more than 10 feet deep, the natural gas pipeline segment ran beneath industrial businesses, an elementary school and residential areas. It also crossed underneath a railroad bridge overpass. In the fall of 2024, Baltimore Gas and Electric (BGE) selected Progressive Pipeline Management (PPM) to rehabilitate the 840 feet segment with Starline® Cured-in-Place-Lining (CIPL).
BGE ruled out replacing the gas main for multiple reasons. Replacement estimates were very high, there would have been significant disruption and a complex permitting process. Full ‘trench and replace’ strategy would have required road closures, excavation over every one of the 75 connecting joints, and the use of expensive steel pipe. Excavation at that depth would be very costly, taking months to complete. Multiple permits would have been needed to dig under the railroad bridge. Traffic rerouting would have caused disruption to businesses, residents and the K-12 school for months.
After the planning and preparation phases, PPM and Miller Construction completed Starline® Cured-in-Place-Lining of the cast iron main in approximately three weeks. Two separate inversions were conducted with the use of three excavation pits and specialized equipment. CIPL proved to be a cost-effective and critical strategy for BGE’s leak reduction initiatives. It allowed the utility to take advantage of adding 100+ years of service life to the aging pipeline.
SCOPE
Once projec t plans were set, the utility and the excavation contractor excavated three access pits, and organized shutdowns and diversion to the gas service lines. Miller Pipeline removed the 75 internal clamps and mechanical seals that had been installed to prevent leaks.
The project was divided into two segments. The first, 208 feet long, was not straight and included four 90- degree vertical bends and two 45-degree vertical bends. After the first 90-degree bend, a 42-inch drip pot located about 18.5 feet deep required special consideration. A bridge of stainless steel was built and installed by Miller Pipeline to support the path of inversion and protect against any future unintended over-pressurization within the annular space of the drip pot fitting.
The 42” cast iron internal pipe surface was cleaned and prepared using grit and a spin blaster.
The second segment, 532 feet long, included three 45-degree bends and a 16-inch service tee that was being abandoned, leaving a void in the pipe. Before lining, PPM installed a high strength carbon fiber Structural Reinforcement Patch (SRP) inside the pipe to cover over the void at the tee fitting.
As part of the standard procedure, PPM inspected both segments for anomalies or unaccounted for structural defects. Both traditional CCTV crawlers and advanced multi-camera models were used to allow the operator to navigate and traverse the multiple pipe offsets. The internal pipe surface was cleaned and prepared using grit and a special tool called a spin blaster. Two high-CFM rated dust collecting vacuum units, creating over 50mph airflow, were deployed to reclaim the grit. Once the cleaning was completed, a second CCTV inspection confirmed the segment was clean and ready for lining.
The installation process began by loading the large diameter material into a large remotely steerable pressure drum. The liner was pneumatically inverted and maneuvered through the pipeline while maintaining 8-psi during the ambient temperature curing. A bluetooth/cellular remote pressure device provided real-time pressure readings of the internal curing along with any possible fluctuations.
With the use of a newly designed anchoring device, PPM increased the work-flow efficiency and preserved workspace within the center excavation. While segment one was curing, the crew simultaneously cleaned and lined the second segment. Each segment’s cleaning, inspection, lining and curing took approximately three days.
““Full ‘trench and replace’ would have required road closures, excavation over 75 connecting joints, costly permits and expensive steel pipe. “
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After curing, the liner was depressurized, and the ends were cut out. Post-lining CCTV inspection confirmed full adhesion of the liner to the host pipe. BGE then performed a standard 25-lb, 24-hour pressure test before restoring the main to service and beginning road and curb restorations.
CHALLENGES
Inside the pit, the 42” pipe is being prepared to receive the liner.
A major challenge was working within the confined space of the lining pit, located in an alley behind an industrial business. The excavated pit was 15 feet deep and 25 feet long, bordered by a brick foundation wall and a loading dock. There was extremely tight spacing for the heavy vehicles and crews required for cleaning, sand blasting and lining. Fast-moving crews had to have access to move, set up and operate the equipment. To lift equipment in and out of the constrained space, BGE brought in a crane.
Ensuring environmental and safety compliance was also critical. The geometry of the pipe and the depth of the pits meant that crews were working up to 8 hours a day inside a trench. Safety protocols and confined space entry procedures for BGE and PPM were put in place to protect the crews performing the clamp removals inside the pit.
Inside the transfer hose, the liner was pneumatically inverted and moved through the pipeline
Another major concern was water infiltration. The pipeline and excavations were below the water table for Baltimore. Water from a nearby culvert was deemed a significant contamination risk. As a safety precaution, BGE employed an environmental subcontractor to keep pumps running 24/7, preventing flooding and protecting the nearby stormwater system.
OUTCOMES & RESULTS
Because of careful planning and coordination among BGE, Miller Pipeline, and PPM, the lining was successfully completed ahead of schedule. Community disruption was minimal. Excavation and trenching did not extend into the roadway and traffic flowed with minimal interruptions.
Rehabilitating the 42-inch pipeline with 3 pits in total over three weeks proved far more viable than full replacement. The decision to line resulted in significant cost and time savings. Had BGE opted for replacement of the main, deep pits would have been excavated every twelve feet. Excavating under the railroad bridge may have been nearly impossible because of the embedded steel pillars. The road would have been shut down for months, disrupting nearby businesses, residences and the school. The associated costs of the materials, excavations and environmental compliance would have been extraordinary.
The full project team.
About PPM: Progressive Pipeline Management is a full service contractor and team of highly skilled infrastructure renewal specialists. For over twenty two years, PPM has been improving the safety and longevity of pipeline infrastructure. They hold the exclusive licensee in North America for the Starline® Cured-in-place-lining. PPM’s specialized expertise includes gas pipeline rehabilitation, restoration of damaged or leaking infrastructure, PIPES ACT 2020 compliance, facilities pipe renewal and site services.
