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Advanced Condition Assessments: The benefits of using Pipe Penetrating Radar

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Abstract: Pipe Penetrating Radar (PPR) is the underground in-pipe application of GPR, a non-destructive testing method that can detect defects and cavities within and outside mainline diameter (>18 in/450 mm) nonmetallic (reinforced concrete, vitrified clay, PVC, HDPE, etc.) underground pipes. The key advantage of PPR is the unique ability to map pipe wall thickness and deterioration including voids outside the pipe, enabling accurate predictability of needed rehabilitation, and/or the timing of replacement. By having this information available, engineers and owners can better estimate the remaining life left in a pipeline, refine timing of rehabilitation, and ultimately better allocate funding for asset management. This paper presents recent advancement of PPR inspection technology together with two selected case studies from the U.S. The Weber Basin Water Conservancy District (WBWCD) Layton, UT and the Denver, CO case studies are discussed in detail. Carollo Engineers and WBWCD conducted a large condition assessment project on the Weber and Davis Aqueducts. The 26-mile aqueduct system (21 to 84-inches in diameter) was constructed in the early 1950s to convey raw water to several water treatment plants and irrigation providers. The aqueducts supply 250 MGD and serve as the primary water source for over 600,000 people. As part of the investigation, the team identified three leaky 60-inch reinforced concrete joints previously fixed with mechanical joint seals along with a “non-leaky” control joint to be assessed with PPR. PPR identified pipe wall thickness and confirmed the rebar configuration in the surveyed joints. Radar data mapped voids outside several of the joints. Small cracks in the bell of the joints were identified on all three of the joints. The “non-leaky” control joint did not exhibit any radar anomalies. With limited available funding and budget constraints becoming more prevalent, timing of rehabilitation and overall intelligent asset management is more critical than ever. Advanced pipe condition assessment technologies, such as PPR show promise as a cost-effective, nondestructive method of condition assessment to help refine the estimated remaining pipe life, accurately determine pipe degradation, as well as provide a basis for improved cost allocation and timing of rehabilitation efforts.

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