Taking Sewer Rehab In-House
Pennsylvania Municipal Authority Uses CIPP Technology to Address Its I/I Challenges
By Simon Burke Dec 03, 2013
The Dallas Area Municipal Authority (DAMA) is a relatively small municipal authority based Pennsylvania but it deals with the same inflow-and-infiltration (I/I) issues that challenge other utilities and municipalities across the United States. In recent years, DAMA brought the work of rehabbing its aging and deteriorating sewer lines in-house, using cured-in-place (CIPP) technology that has resulted in a more cost-effective approach to its sewer maintenance program.
The DAMA sewer collection and conveyance system consists of approximately 100-plus miles of gravity sewer lines, ranging in size from 6 to 30 in., with 8-in. clay being the predominant type and size dating back to the 1970s. There are 16 remote pumping stations located within the system, which use pumps from 2 hp to 75 hp. There is also a 2.8 million-gal flow equalization tank located at the headworks of DAMA. The average daily flow over the past several years has risen to approximately 3.8 MGD, with measured wet weather flow events ranging from 5 MGD to 8 MGD. The main pumping station at DAMA uses three 75 hp submersible pumps with variable frequency drive control units, and a diesel-powered emergency generator.
The DAMA sewer division staff consists of seven full-time employees, five of which are PA Certified Operators, whose daily duties include inspection, operation and maintenance, and repair of the DAMA sewage collection system and pumping stations.
Decision to Rehab “in-house”
In the early 2000s, DAMA began a comprehensive and proactive maintenance program to address I/I issues. Working in conjunction with the DAMA board and its engineer, the decision was made to address the I/I issues by purchasing the necessary equipment and performing the repairs in-house. This allowed DAMA to clean, televise and repair defects noted within the collection system at the full control of the sewer division staff, using DAMA personnel and equipment in a more cost-effective manner.
DAMA have been installing the Trelleborg epros Drainpacker cured-in-place pipe (CIPP) sectional repair for several years as a cost-effective, fully structural repair method to tackle emergency repairs of major defects and seal heavy infiltration without the need for costly grouting.
DAMA had previously contracted out manhole-to-manhole sewer rehabilitation, however, it was looking to have a more cost-effective approach and to have full control as to when and how much pipe can be repaired year-round, in a manner that meets the workload requirements of their staff. DAMA also wanted to work cooperatively with adjoining municipal authorities in a regionalized approach to the operation and maintenance of their sewage collection systems and Act 537 Plans.
After careful review, the DAMA board decided that purchasing and operating the mainline CIPP equipment outright as opposed to putting out tenders for sub-contracted repairs gave DAMA the necessary cost-savings, control and desired approach.
DAMA staff and board engaged on an extensive review of the various CIP systems on the market. DAMA staff members attended product demonstrations, trade shows and various seminars. When final consideration was given to quality, design, product support and ease of operation, Trelleborg, along with local distributor Exeter Supply, came out on top.
Trelleborg is a world leader in engineered polymer solutions that seal, damp and protect critical applications in demanding environments. Its innovative engineered solutions accelerate performance for customers in a sustainable way. Within the Trelleborg Group - Trellborg Pipe Seals design, manufacture and supply specialist equipment and materials for pipeline construction, maintenance, repair and rehabilitation. Their research and development ensures they are at the forefront of developments in the industry, specifically providing structural repairs and sealing solutions to reduce inflow and infiltration in existing sewer systems.
Within the United States, Trelleborg has office, sales and technical support, manufacturing and warehousing facilities in Milford, N.H., and Bonne Terre, Mo. This is supported both in terms of materials and equipment development and supply from its head office in Duisburg, Germany. All their systems are independently tested and exceed all international design standards for sewer rehabilitation including ASTM, EN, DIN, BS, AS etc.
DAMA’s remit was that the equipment should be suitable to rehabilitate mainline sewers 8 to 12 in., up to 400 ft in length, with the majority of pipes being 8 in. in diameter. Based on this requirement and following meetings and a visit to Trelleborg Pipe Seals head office in Duisburg, DAMA selected an epros Type 3 inversion system along with impregnation, vacuum system and M300 steam unit.
The epros Type 3 inversion drum is designed to hold up to 15-in. liners and has a capacity for more than 400 ft of 8-in. liner. The corresponding steam unit is specifically designed for sewer rehabilitation. Steam generation is fully automated to reduce fuel and water consumption. Steam is “dry” with a moisture content maximum of 2 percent, this ensures minimal water condensate during the curing process.
The material selection was based on several factors including environmental and health impact, quality of finished product, structural repair, I/I reduction and pricing. Final product selection was for epropox HC120 epoxy resin system in conjunction with epros Drainflex Polypropylene coated liner.
Eproxpox HC120 resin is a 100 percent solids epoxy resin. It does not contain any VOCs or styrene. There are no unpleasant odors. It has a potlife of 120 minutes at 75 F. This potlife can then be greatly extended when the impregnated liner is chilled. This allows the DAMA staff to factory-impregnate the liner in controlled conditions to ensure high quality. The impregnated liner is then placed in a cool box and transported to the site, where it is wound into the inversion unit onsite directly from the cool box positioned in a truck. The liner is then installed under air pressure. The inversion drum ensures that the liner is under constant pressure at all times during the inversion and curing process.
Once the liner is installed it is heated with steam and has a curing time of 45 minutes at 176 F. The final product has zero shrinkage ensuring there is no annular gap between the host pipe and liner preventing groundwater reentering the system at manholes and re-opened lateral connections.
Full training and certification was provided by Trelleborg technical staff at DAMA’s facility and through onsite installations.
DAMA executive director Larry J. Spaciano stated that results to date appear to indicate that DAMA made the right decision, and that it would not hesitate to recommend the Trelleborg product line to other interested municipal authorities and contractors.
Simon Burke is product group manager of pipeline rehabilitation products-North America for Trelleborg Pipe Seals Milford Inc, which is based in Milford, N.H.