Project Overview
In autumn 2017, construction work began to remediate approximately 1,000 linear feet of a 30-inch return activated sludge (RAS) line at the East Central Regional Water Reclamation Facility (ECRWRF). RAS lines play a critical role in wastewater treatment, returning activated sludge to aeration basins to maintain biological processes.
The facility treats up to 70 million gallons per day, supporting wastewater flows from West Palm Beach, Lake Worth, Riviera Beach, Palm Beach, and Palm Beach County. As part of an extensive three-year Biosolids Improvement Project, new 42-inch aeration lines were being installed directly above existing RAS lines, prompting concerns about their long-term condition and access for future maintenance.
Project Challenges
As installation of the new 42-inch aeration lines progressed, project engineers at Hazen identified several urgent risks:
- Existing 30-inch ductile iron RAS lines showed signs of deterioration.
- Construction directly above the RAS lines increased structural loading.
- Once the new aeration lines were installed, the ability to repair or replace the RAS lines in the future would be extremely limited.
Given these challenges, Hazen was tasked with fast-tracked feasibility, design, and management of a full rehabilitation programme for the twin RAS pipelines.
Accelerated Procurement and Delivery
To prevent delays to the wider Biosolids Improvement Project, an expedited procurement timeline was implemented.
- May 2017: Solicitation for proposals issued
- Insituform selected to deliver rehabilitation using InsituMain® CIPP
- Work subcontracted through Poole & Kent, general contractor
- July 2017: Lining activities commenced
- Early August 2017: CIPP installation and closeout completed
This accelerated turnaround ensured that broader construction activities remained on schedule.
Materials: InsituMain® CIPP for Pressure Pipelines
The project used Insituform’s second-generation InsituMain® fibre-reinforced CIPP system, engineered for:
- Force mains and pressure pipelines up to 96 inches
- Pressures up to 250 psi
- Complex geometries and bends
- Host pipes including ductile iron, steel, asbestos cement, reinforced concrete, cast iron, and thermoplastic materials
Structural and Performance Benefits
The InsituMain® system is designed to:
- Restore structural integrity
- Withstand internal and external loads
- Prevent leakage and corrosion
The liner is composed of:
- Epoxy composite layer
- Reinforcement using glass materials and/or polyester fibre
- Polypropylene inner layer for increased smoothness, reduced friction, and additional corrosion resistance
Latest InsituMain® Enhancements (NSF/ANSI Standard 61 Certified)
- Better expansion and improved fit
- Repairable liner coating
- Longer shot lengths
- Wider diameter capabilities
- Increased flexibility
- Simplified installation
- Reduced resin usage by approximately 15 percent
- Higher burst strength (up to 1,400 psi)
- Enhanced composite strength
- E-CR fibreglass for improved long-term corrosion resistance
CIPP Installation Method
To maintain plant operations, the twin RAS lines had to remain active throughout construction. Shutdown was not an option.
Bypass Requirements
- Above-ground HDPE bypass pipelines were installed to reroute the flow of sludge
- Work areas were confined, with aeration basins, clarifiers, and bypass lines limiting space for equipment and staging
Installation Process
- Liners were transported from a refrigerated lorry and placed onto a conveyor system.
- The conveyor moved the liner to the top of the installation tower.
- Installation was performed using water inversion and hydrostatic head pressure, allowing the tube to invert and conform tightly to the interior of the host pipe.
Innovative Termination Method
The project incorporated an emerging technique for pressure pipe CIPP:
- Fibreglass reinforced plastic (FRP) spool pieces were used to terminate the liner
- When the epoxy resin bonded with the FRP material during cure, it formed a high-strength CIPP/FRP connection
Testing
Before installing mechanical fittings and closure pieces, a hydraulic pressure test confirmed the liner could withstand the internal 25 psi operating pressure.
Both installations passed pressure testing according to ASTM F1216, confirming structural performance.
Project Outcome
The rehabilitation was completed within a few weeks in August 2017, delivering:
- 1,000 linear feet of 30-inch fibre-reinforced CIPP
- Installed in two shots
- Minimal excavation at a complex, heavily constrained site
- Mitigation of potential long-term risks associated with the new 42-inch aeration lines above
The InsituMain® solution provided the client with a durable, structurally sound RAS pipeline system, ensuring continued reliability within the broader wastewater treatment process.
