Repairs Made With Under Pressure Installations Can Offer Reduced Risks And Expenses

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1 Repairs Made With Under Pressure Installations Can Offer Reduced Risks And Expenses They also give the community a built-in re-entry system for future monitoring and repair. BY BRETT HANES According to one estimate, there are more than 795,000 miles of wastewater pipeline in the United States. The nation s sanitary sewer system is increasing in size, and the existing infrastructure is aging. A good portion of the sewer pipe conduit is under attack by sewer gases (hydrogen sulfide), aging, internal and/or external forces, corrosive soil, pipe settling or shifting, higher flow demands, and issues caused by having the wrong materials installed and/or improper installation. Regardless of what is attacking and depreciating the nation s $1 trillion sewer pipe infrastructure equipment, there are methods available to maintain the sewage system without draining or spilling hazardous sewage. These methods enable municipalities to safely maintain and control the sewage system without system shutdown. Obviously, the owner of a collection system cannot control whether a sewage pipe is going to break, resulting in a sewer spill that contaminates the environment. It is in the selection of the means of construction, equipment utilized, and methods employed that the owner can have an impact on the safety and dependability of his system. The repair and maintenance strategy of any given wastewater system will largely depend on the owner and the operator/maintenance personnel s knowledge of the most up-to-date methods, technology, equipment, and practices. With the proper equipment and proper sequence of its use, in conjunction with other proven piping restoration methods, the finished product will result in a successful project. Why? The repaired infrastructure (asset) has gained additional years of service. Repairs made with under pressure installations (UPIs) result in the community having a built-in re-entry system for future monitoring and repair. In addition, there are other benefits of UPIs: Health and Safety: One of the primary constants is providing a safe work environment for those maintaining the system. Needless to say, people have always experienced the displeasure (real and imagined) of repairing sewage lines. However, it hasn t been until more recent years that the full hazards of inhalation and absorption of the toxins through the skin have become well documented. Environment: A large concern to the National Pollutant Discharge Elimination System is the environment. As it states: A key concern with sanitary sewer overflows that enter oceans, bays, estuaries, rivers, lakes, streams, or brackish water is the effect on water quality. When bodies of water cannot be used for drinking water, fishing, or recreation, society experiences an economic loss. Financial: For cost-comparison purposes, consider an alternate method employed to perform necessary maintenance. The contractor/owner begins by selecting a site and excavating a collection pit large enough to handle the sewage in the area affected by the repair. It is necessary to line this excavated collection pit with an antiabsorbent material to limit sewage spill seepage into the soils. Now, in some manner, the sewer line flow is directed to the excavated pit, then the sewage is redirected by a pump (or multiple pumps) into a convoy of tankers. The convoy of tankers takes the sewage to a collection point where again it needs to be pumped or dumped into another pit, manhole, lift station, or lagoon. This process continues 24 hours per day until the repair or replacement is completed. Some of the financial challenges to this method include selecting a time of low flow activity, such as evening; predicting the weather and precipitation; controlling traffic; reflecting on and calculating the amount of exposure and contact of sewage to humans and the environment; restoration costs for the excavation of pits; coordination of convoy tankers and drivers; and many other hidden risk factors associated with raw sewage. The risk and expense to the sanitary sewer collection 44

2 owner are drastically reduced when using UPI as compared with the tanker convoy, pumping, and excavated holding pond method described above. Additionally, with the use of UPIs, no one is out of service, and flow continues in a safe and pressurecontained bypass pipe using the sewage control equipment without exposing the hazardous lurking sewer to humans and/or the environment. UPIs have been selected as the method of maintenance by many sewer collection systems to make needed repairs without pipeline shutdown. Herein we will discuss the two UPIs being used at the WSSC (Washington Suburban Sanitary Commission) Northwest Branch of the Sligo Creek Interceptor in Maryland: a UP (under pressure) sewer tapping technique and UP line stopping. This project involves the repair of a section of collapsed main, then the relining of a portion of a 66-inch sanitary main. Additional applications for tapping include, but are not limited to, adding inlets or outlets to steel or concrete tanks and vaults, adding pumping stations, inserting probes and flow meters, and launching and retrieving stations for pipeline pigging. UP Line Stopping The technique of line stopping incorporates the UP Sewer Tapping Technique The basic principle includes three easy steps: 1) Attach a pressure-tight tapping sleeve and valve to the primary conduit. 2) Make the pressure tap and remove the tapping machine. 3) Connect the new permanent pipe or temporary bypass pipe to the tapping valve to complete the branch connection. Figures 1, 2, and 3 illustrate the preparation of the concrete pipe with pretension wires, tapping machine, and the removal of a section (coupon) of the 66-inch PCCP (prestressed concrete cylinder pipe). The applications for sewer UP tapping are wide and varied. A tap connection may simply be a 1-inch (25 mm) live connection for a proposed air and vacuum valve. On the other end of the spectrum, the UP tap connection could be a 102-inch (2,600 mm) or larger UPI to connect the existing collection system into a new treatment facility or to create a temporary or permanent bypass. 45

3 Figure 1: Preparing the 66-inch PCCP for the pressure tap chipping concrete and restraining the prestressed wire Figure 2: Attaching the inner gland seal onto the steel cylinder of the 66-inch PCCP Figure 3: A section of the 66-inch PCCP coupon retained in whole within the tapping machine holesaw technique of pressure tapping as described. This tapping technique utilizes a machine that temporarily controls the sewer fluid during maintenance and expansion without system disruption. The technique is as follows: 1) Attach a line stop fitting with a temporary valve. 2) Tap the pipe and remove the tapping machine. 3) Position the sewer flow control equipment (the line stop machine uses a solid plug, not an inflatable plug). While the sewage is controlled, the contractor or utility can perform the necessary expansion (see Figures 4 and 5). 4) Remove the sewer flow control line stop machine and attach the completion plug under pressure. An extremely popular application for UPI line stopping is in the repair and replacement of inline control valves (pinch, butterfly, plug, gate, or ball), lift stations, and air and vacuum valves. Sewer control line stopping doesn t always mean stopping the flow. When performing a double stop, there are methods of UPI line stopping that can be utilized without stopping the sewage flow. Garrison Enterprise, of Vineland, NJ, general contractors, selected both UPI tapping and line stopping techniques in tandem for the WSSC Northwest Branch of the Sligo Creek Interceptor. Using Hydra-Stop equipment, this combination of tapping and stopping techniques provides the elements necessary to maintain consistent service. The general scope of the Northwest Branch of the Sligo Creek Interceptor is to bypass sewage around approximately 1,950 feet of 66-inch PCCP, said Elbert Basolis, president of Garrison Enterprise. To construct the project, two large-diameter pipe taps were made on each end of the project for influent and effluent pumping, respectfully. Just inside each of the pipe taps, a 66-inch line stop was constructed to isolate the flow in order to allow for the repair of the collapsed pipe. Between the two line stops, eight pressure taps were made to access the pipe for dewatering, closed circuit television, and cleaning and relining the PCCP now and in the future. From a comparison cost standpoint, utilizing under pressure installation procedures benefits the owner significantly and, more importantly, drastically reduces the general contractor s risk exposure to the environment and health and safety risks for employees. Figure 6 illustrates a temporary bypass line with a portable pump transferring the sewage so necessary repairs can be made without human exposure to the sewer, system shutdown, and sewer spills. In the end, the only remaining items attached on the line are the pressure-tight chambers or sewer control equipment fittings. 46

4 Figure 4: Preparing the 66-inch folding head to be attached to the line stop fitting It is worthy of note that these fittings are pressuretight chambers and can be utilized in the future to gain controlled entry into the sewage pipeline repeatedly without sewage spill or system shutdown. Line stopping has tremendous potential and unlimited opportunities, providing engineers and utilities with full Figure 5: Attaching the 66-inch line stop onto the temporary valve control of the sewage while maintaining and repairing infrastructure assets. The applications and capabilities of line stopping include replacement of lowering or rerouting pipe (grade separations, road widening), replacement of valves and pipe, installation of smart pig launching sites, isolation of 48

5 reinforced concrete (noncylinder), reinforced concrete cylinder, plastic, AC, and nonferrous metals. Line stopping allows the utility to be creative in repairing and replacing the necessary sewer collection system parts without sewage spills or sewer plant shutdown. Acknowledgements Special recognition and acknowledgements are in order for Elbert Basolis, president, and the entire team of Garrison Enterprise. They have provided valuable information throughout the design and construction process. Figure 6: Temporary bypass line with a portable pump transfers sewage pipe for cure-in-place pipe re-lining with bypass capabilities, and other trenchless technologies. UPI sewer control line stopping is relatively unlimited with respect to the pipe. These include steel, cast iron, Brett Hanes, general manager of Hydra-Stop, A Division of ADS LLC, has nearly 25 years of sales, business development, and customer relations experience in the water and sewer equipment industry. His background includes product development and improvement, territory management, and private ownership. Mr. Hanes is a member of the American Water Works Association. As general manager of Hydra-Stop, he is responsible for the management of all activities and personnel related to the Hydra-Stop product line. He can be reached at (708) , Ext. 200, or [email protected]. 50