Trenchless Technology

JAN 2019

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46 T R E N C H L E S S T EC H N O LO GY JA N UA RY 2019 C A R T R I D G E M E T H O D S O L V E S H D D C H A L L E N G E A C R O S S H U N T I N G B AY O U By Christine Kirby, P.E. O N E O F H O U S TO N'S major water transmission mains is a 42-in. line that begins at the East Wa- ter Purification Plant and continues north and west to provide water to a large distribution area in the north- east part of the City. Spanning nearly eight miles, the pre- stressed concrete cylinder pipe along Federal Rd., IH-10 East Freeway, and Loop 610 was con- structed in the late 1960s and early 1970s. This 42-in. main has a history of leakage and needs repairs. For a 3,600-ft section along IH-10 East Freeway, between Baca Street and Centerwood Drive, there wasn't a small -diameter water distribution line for local water customers. This 42-in. transmission main provided service for the businesses and ten- ants in this area. Eight active custom- ers were connected to the 42-in. PCCP within this section, meters ranging in size from 1 to 6 in. Customers along this busy frontage road included a motel , a shopping center, a high-rise office building and a restaurant . The City of Houston recently detect- ed an active leak on this aging 42-in. line within the project limits. Part of this line, which crosses Hunting Bay- ou above-grade, had been submerged in recent flooding and needed to be replaced. Two isolation valves on the 42-in. line also needed to be replaced. To perform this repair work, a long- term shutdown was desperately need- ed. Shutdown was not a possibility, because isolating the 42-in. would put these eight customers out of service. Lockwood, Andrews & Newnam, Inc. (LAN), a national planning , en- gineering and program management firm, has served as the City of Hous- ton's technical advisor for its Surface Water Transmission Program (SWTP) for more than three decades. The City asked LAN to develop a solution to repair the 42-in. line without disrupt- ing service to the eight customers. Af- ter evaluating various options, LAN engineers identified constructing a small diameter distribution main as the solution. A 12-in. water line could be connected to existing distribu- tion lines and extended from Baca to Centerwood within a separate ease- ment parallel to the existing 42-in. After placing the new 3,600-ft line in service and transferring the custom- ers, a long- term shutdown of the 42- in. PCCP could be planned. However, constructing this 12-in. water line posed some daunting challenges. Cartridge Method O ne of the major challenges was a 600-ft crossing at Hunt ing Bayou , one of Houston's major water ways that meanders through northeast Houston unt il it reaches Buffalo Bayou at the Houston Ship Chan - nel . With act ive nearby businesses and driveways on either side of the bayou , the entr y and exit sites for horizontal direct ional drilling had to be carefully placed. O n the west side of the crossing , there was room for the drill rig and entr y point set up. O n the east side, there was much less space, and the full pipe string could not be laid out without block- ing a busy intersect ion . With fused pipe, each joint must be fused and allowed to cool , and the complete pipe string laid out prior to being pulled into the reamed hole. To avoid blocking the busy Centerwood intersection, the cartridge method of engaging each joint as the pipe was being pulled back provided the best solution. LAN recommended Certa- Lok C-900 RJIB (restrained joint inte-

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