Wastewater collection systems, being below ground, have been out of sight and out of mind for decades, even centuries. Rainfall enters degrading pipes and can overwhelm some systems. New inspection technology has rapidly advanced our ability to assess these facilities. With this information in hand, we are working with urgency to systematically plan, prioritize, and optimize collection system repairs and upgrades.
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City of Richmond and Veolia Water
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The City of Richmond Wastewater Collection System Master Plan identified a number of capacity improvement needs, including the upsizing of the existing trunk line that crossed under a railroad right of way and continued below a major transportation corridor. This project was required to accommodate rainfall-dependent inflow and infiltration that overwhelmed the existing pipeline during heavy rainfall events. The total estimated project cost in 2011 dollars was $16.1 million.
Nearly all of the pipes within the sewer basin directly upstream of the planned capacity improvement, named the 13th Street Basin, had been inspected. VWHA analyzed the results from this inspection database and identified numerous pipes with National Association of Sewer Service Company ("NASSCO") Pipeline Assessment and Certification Program ("PACP") Grade 5 defects, which are defined as the most severe defects. Further analysis led to a strong hypothesis that due to the severely damaged status of the 13th Street Basin pipes, it was plausible that addressing the NASSCO PACP Grade 4 and 5 defects through pipeline replacements and repairs could reduce rainfall dependent inflow and infiltration to the level where the proposed capacity project could be avoided. The City initiated the 13th Street Pipeline Capacity Improvement Project, which selectively replaced or repaired approximately 27 percent of the 21-mile pipe inventory. Pipes that were repaired ranged in diameter from 6- to 21-inches. Following completion of the project, the City installed temporary flow meters to assess whether any measurable changes had occurred in rainfall-dependent inflow and infiltration. The flow monitoring results were used to recalibrate the hydraulic model for 2019 conditions. The hydraulic model confirmed that rainfall-dependent inflow and infiltration had been reduced. Further, the model no longer predicted the need for the original capacity improvement project. In summary, the City was able to repair a significant portion of the wastewater collection system and avoid downstream interceptor improvements using the funds that were originally earmarked for capacity improvements. |
VWHA has helped the City of Richmond to reduce its wet weather sewer overflows, improving health and safety for its residents and recreational users.
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