Lateral Lining: Comprehensive Approach to Sewers
November 2, 2015The Town of Norwood, Mass., is similar to many communities across the United States in that it is under an EPA consent decree to reduce water pollution and inflow and infiltration (I&I). Norwood is a suburban community located south of Boston, with a population of 28,000. The Town sewerage network is comprised of 100 miles of pipe ranging in size from 4 to 24 in.
The Town embarked on a program of work to meet EPA compliance by 2023. To assist with the design and implementation of this program Norwood retained CDM Smith Inc. as the consulting engineer.
CDM Smith Inc. is an international engineering firm based in Cambridge, Mass., with regional offices across the United States. CDM has worked with many communities under an EPA consent decree bringing a more progressive approach at eliminating infiltration of an aging sewer system. The integration of lateral lining into a comprehensive rehabilitation approach is a new and effective solution to the problem. Lateral lining is the final rehabilitation step, which yields the most cost-effective use of public expenditures in permanently sealing your sanitary sewer collection system by reducing and eliminating infiltration and eliminating exfiltration, as well.
Norwood faces issues with both exfiltration and I&I. The Town has an under drain system located below the existing sewer network. The sewer network is aging and starting to fail, as a result sewerage is leaking from the sewer pipes and entering the under drain system. This effluent is contaminating the local groundwater and waterways. The EPA has been monitoring the Norwood’s drainage outfalls and has recorded very high E.coli bacteria counts in the range of 5,000 to 50,000 MPN/100ML
Additionally, during wet weather events the groundwater has been entering the sewer network. The result is the treatment plants are being overloaded because of having to unnecessarily treat this “clear water.” Norwood has also recorded sanitary sewer overflows (SSOs) during certain rain events event caused by excessive infiltration.
Based on CDM’s experience and its understanding of the technology available within the marketplace, CDM’s project designers became advocates of the comprehensive approach to sewer system rehabilitation. The comprehensive approach has evolved into the philosophy at permanently sealing the existing sanitary sewer network by preventing sewerage exfiltration along with decreasing and eliminating groundwater infiltration, as well. The comprehensive approach has the underlying philosophy to fix the sanitary system correctly thereby preventing sewerage exfiltration while decreasing/eliminating groundwater infiltration. The comprehensive approach requires that the sanitary system be fixed correctly and permanently so that there is no need to reevaluate it again. “Fix it Right the First Time” is the common sense phrase. The comprehensive approach rehabilitates manholes through grouting/cement lining/epoxy coating, mainline sewers through cured-in-place (CIP) lining installation and laterals through CIP main to house lateral lining from the host pipe.
Until recently, the focus of sanitary sewer rehabilitation has primarily been on relining the main sewer pipe manhole to manhole and sealing the manhole structures. Laterals are reinstated and groundwater is allowed back into the system. In some instances, lateral connections were grouted but a permanent solution was never applied until now. Lateral pipes have been neglected because of its complexities. First, there is the issue of ownership. Who is responsible for the connection and lateral pipe and to what extent? Second has been the limited technology available in the market place to permanently rehabilitate the lateral with minimal disturbance to the residents, sewer service and surrounding environment.
Growing studies have shown that by incorporating a comprehensive approach with a permanent solution significantly reduces infiltration and also provides a barrier against exfiltration. This is the approach that stands the test of time.
Technology has caught up to the demand in the marketplace and now allows the lateral to be lined and a watertight mainline connection to be made during the same installation. Consulting engineers are becoming more aware of the lateral lining industry advancements and the results it can provide. The ability to permanently seal the lateral and its connection interface to the mainline CIP liner is the final piece of the comprehensive puzzle.
When designing the scope of work in Norwood, the issues of lateral pipe ownership were discussed. The Town owns the connection and the lateral pipe up to the property line (approximately a lateral length of 20 ft from the mainline to property line). However, infiltration and exfiltration problems were not only occurring in the first 20 ft, but also beyond the 20-ft limit and needed to be resolved.
Norwood’s engineering personnel took the leadership role by making the decision to line up to 10 ft of the house foundation. This design decision would push the trenchless limits of lining the lateral from the host pipe without the need of a secondary means of access (i.e. no cleanout needed to be installed). The EPA was on board with the approach and was pleased to see the Norwood’s leaders taking a leadership role to permanently address the environmental issues facing the aging collection system. Norwood’s leaders took a leap of faith that the trenchless market would rise to the occasion and execute their vision. The hope was to be able to execute this work with minimal disruption to the homeowner.
In 2011, Phase 1 of the project was released. Although the project was complete, the installation contractor was still required to install a secondary means of access (i.e. cleanouts) in order to rehabilitate the lateral to the lengths that the Town desired. Subsequent Phases 2, 3 and 4 were released each year thereafter. Each project focused on specific subareas and required the entire network to be sealed — mainline, manholes and laterals.
National Water Main Cleaning Co. was the low bidder and deployed the newly evolved and developed Trelleborg epros Main to House (MtH) system with its capability of lining lateral of lengths up to 100 ft without a cleanout. In the end, each project was a success with very few cleanout installations unless under extraordinary circumstances.
“This ‘seamless’ sewer system has virtually eliminated the contamination, substantially reduced infiltration into the sanitary sewer and has provided a ‘new’ sewer system right to the front door of the taxpayer.,” says Mark Ryan, P.E., P.L.S., Norwood engineer. “It’s a win-win for everyone. Norwood has been very pleased with the work performed by National Water Main Cleaning Co. and its ability to minimize disruptions to property owners,.”
The quantities for each subarea varied, but total quantities for the three subareas were approximately 27,600 ft of mainline, 185 manholes and 490 of laterals to be rehabilitated per subarea.
The projects were unique and presented several challenges in that a high proportion of the lateral connections were break in connections that entered the main pipe at a various angles. Also, the majority of the laterals did not have access via a cleanout. Many of the property lots were large and a house could sit far back in its lot, resulting in a long lateral length. The average lateral length was in the mid 40-ft range, with several laterals reaching lengths of 100 ft long. Norwood required that the lateral pipe be cleaned, inspected and relined from the main sewer pipe. From the beginning, Norwood wanted to avoid any disruption to private property.
Phases 2, 3 and 4 were completed over a three-year time frame. Out of the 490 laterals that were lined, the average length was approximately 45 ft from the mainline. Only four laterals required cleanouts. The other 486 laterals were lined from the mainline without a cleanout. The longest lateral lined without a cleanout was 104 ft.
National Water Main Cleaning Co. is a subsidiary of the Carylon Corp. The Carylon Corp. was established in 1949 and is the largest privately held contractor in the United States; providing a full-range of municipal and industrial related services that includes pipe cleaning, inspection and rehabilitation. The Carylon Corp. is comprised of 18 wholly-owned companies that operate out of more than 32 locations nationwide.
Carylon companies have used the Trelleborg Pipe Seals epros lateral repair technology for several years. With the demand to line further and further up the lateral from the main pipe, Trelleborg in partnership with Carylon Corp. has developed its epros MtH Technology to satisfy the marketplace.
Trelleborg is a global industrial group which specializes in advanced polymer technology and applications. It develops high-performance solutions that seal and protect in demanding industrial environments. Trelleborg Pipe Seals are a market leader in the manufacture and supply of specialized equipment and materials for pipeline construction, maintenance and rehabilitation.
The results of the project so far have been excellent. To such an extent that at the completion of Phase 4, the EPA requested a meeting in which National Water Main and Trelleborg provided a presentation on the technology being employed along with an onsite live demonstration.
The EPA became interested in lateral lining because of the actual results it witnessed during its continuous monitoring of the groundwater as National Water Main Cleaning progressed through its rehabilitation work. Bacteria levels dropped from 50,000 MPN/100ML to nearly zero. The EPA, CDM Smith and Norwood each attributed the drop in bacteria counts to the success of the lateral lining installation work.
National Water Main and Trelleborg were invited to the EPA Region 1 head office in Boston and, subsequently, to the EPA headquarters in Washington, D.C. There, the companies provided a detailed technical presentation on the comprehensive approach to sewer rehabilitation with a focus on the lateral pipe rehabilitation technology. The EPA enforcement staff and Federal CSO manager were very pleased with the development of the new lateral lining technology and private consultant’s use in applying it to the public infrastructure.
“The EPA is encouraged to see that lateral lining technology has progressed to a point where it can further eliminate infiltration issues and exfiltration issues,” says EPA senior enforcement coordinator.
Lateral lining is becoming the driving rehabilitation process in the sanitary sewer comprehensive rehabilitation approach. The process of lateral lining is the final overlapping step that ultimately yields such high infiltration reduction percentages. National Water Main Cleaning Co.’s/The Carylon Corp.’s ability to provide project management, the latest technology and a skilled workforce of the various rehabilitation techniques is a key element to ensure success to a project outcome.
The corporate partnership with Trelleborg in the development of the MtH technology has produced an industry leader in the sanitary sewer lateral rehabilitation marketplace. It offers the ability to line lateral from the host pipe unlike any other system in the marketplace. The ultimate result is a watertight sanitary collection system that protects the environment against exfiltration and infiltration which causes sanitary and combined sewer overflows.
Dennis P. Sullivan, P.E., is vice president at National Water Main Cleaning Co. Simon Burke is commercial manager at Trelleborg Pipe Seals.