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The Las Vegas Valley Water District (LVVWD) is responsible for providing water to over one million people in southern Nevada, including the City of Las Vegas. In 2011, LVVWD's state-of-the-art asset management program discovered that one of several important feed lines to the Las Vegas Strip was leaking.
The utility detected leakage in a 36-inch cement and mortar lined and coated steel pipeline (MLCP), installed in 1993, that provides water to the famous Las Vegas Strip. The line runs under busy Interstate 215, which is part of a 50-mile "beltway" that circles about three quarters of the City. Complicating matters, access to the line was problematic due to the below grade location of I-215, which actually runs under Las Vegas Boulevard.
LVVWD Engineering and Asset Management evaluated various accepted pipe materials and techniques as they grappled with site constraints, cost, and reliability. Replacement with new MLCP pipe would have required an expensive casing and was ultimately evaluated at 50 percent higher cost than sliplining with Fusible PVC® pipe or HDPE. LVVWD also examined CIPP (Cured-In-Place-Pipe), but there were no previous potable water installations with Class IV pressure lining at the desired diameter and pressure. Additionally, repeated alignment changes as the line dropped from Las Vegas Boulevard to go beneath I-215 were viewed as challenging. Ultimately, Fusible PVC® pipe and sliplining were selected as the combination that provided the best tradeoff among cost, risk, and performance.
The contractor decided that five separate sections of pipe would be fused aboveground, with the 300-foot, below grade, I-215 crossing being fused in-pit. The Fusible PVC® pipe was inserted into each section of host pipe through an "insertion pit." At either end of the alignment, the water line makes several bends as it reconnects to the steel cylinder concrete pipe feed line. Restrained standard ductile iron fittings were used in each case to connect the horizontally offset fused PVC segments, as well as to connect to each end of the remaining steel line. Due to the highly constrained work area adjacent to I-215, in-pit fusion of 10-foot pipe sticks was utilized to restore the section of pipe directly below the highway itself. Normally, fused PVC is supplied in 40-foot lengths, but in this case the factory pre-cut 10-foot sections of pipe to accommodate the tight site. Additionally, standard ductile iron fittings were used for the vertical offsets, making for easy connection to appurtenances and the other pipe segments.
The sliplining was completed and pressure tested on January 25, 2013, and the new pipeline was put into service in February. While the overall fieldwork took approximately 180 days, the pipe replacement itself was completed in just 37 days.
|Pipeline Details and Project Summary|
|Project:||I-215/Las Vegas Boulevard, Las Vegas, NV|
|Length/Pipe Size:||800 LF of 30-inch DR25 Fusible C-905®|
|Pressure Test:||150 psi for 2 hours|
|Owner:||Las Vegas Valley Water District|