Central San shifts sewer maintenance strategy to combat root intrusion in legacy clay pipes

Central San shifts sewer maintenance strategy to combat root intrusion in legacy clay pipesFollowing an uptick in sanitary sewer spills in 2025, the Central Contra Costa Sanitary District is transitioning vulnerable pre-1960 pipe networks to mechanical root-cutting programs, while also advancing a $1.5 million PFAS regulatory planning contract.

The district recorded 24 sanitary sewer spills in 2025, driven largely by root intrusion in pre-1960 clay pipes located in Lafayette, Orinda, and Walnut Creek.

While the frequency of spills increased, the total spilled volume dropped by 60%, averaging 513 gallons per incident.

Operations staff reviewed over 750 CCTV reports to identify vulnerable lines, shifting them from hydro-flushing to mechanical root-cutting.

The board approved a $1.5 million consulting agreement with Brown and Caldwell for PFAS adaptive management.

Central San achieved 100% NPDES permit compliance in 2025, treating 13.4 billion gallons of wastewater.

During its April 2, 2026 meeting, the Central Contra Costa Sanitary District (Central San) board reviewed its 2025 operational performance and approved key regulatory investments to manage both legacy infrastructure and emerging contaminants. According to the 2025 Sanitary Sewer Spills annual report, the district experienced 24 spills last year. While this represents a slight uptick in the frequency of incidents, the total volume spilled decreased by 60%. The average volume per spill was 513 gallons, and zero incidents were attributed to inadequate system capacity. Root intrusion was the primary culprit, accounting for 71% of the spills. Another 8% were caused by grease, and 21% by other debris such as concrete, asphalt, and non-flushable wipes. Staff noted that the structural challenges are heavily concentrated in Lafayette, Orinda, and Walnut Creek, which rely on pre-1960 clay pipes characterized by legacy materials and outdated installation methods. To address the localized uptick, Central San is pivoting its maintenance tactics. A staff member presenting the report explained that lines historically maintained with standard hydro-flushing were beginning to experience unprecedented root blockages. In response, operations staff reviewed 752 closed-circuit television (CCTV) reports to identify discrepancies where root presence was noted in descriptions but not properly flagged. Affected lines have now been transitioned to a mechanical root-cutting maintenance program to prevent future blockages. Despite the collection system challenges, the district's treatment operations maintained a flawless regulatory record. Plant Operations Division Manager Alan Weir reported that Central San treated 13.4 billion gallons of wastewater in 2025 with 100% compliance under its National Pollutant Discharge Elimination System (NPDES) permit. The milestone makes the utility eligible for the National Association of Clean Water Agencies (NACWA) Platinum Award for the 28th consecutive year. On the future regulatory planning front, the board used its consent calendar to authorize a $1,500,000 professional consulting services agreement with Brown and Caldwell. The contract will fund regulatory planning services under the district's Per- and Polyfluoroalkyl Substances (PFAS) Adaptive Management project, ensuring the utility is prepared for tightening federal and state regulations regarding forever chemicals.