Dear Cambrians,

Stuart Street Tank Incident – Summary

Update: Laboratory test results have confirmed that Cambria’s water supply was not contaminated during the recent pressure loss event. Based on these results and in coordination with the County of San Luis Obispo Environmental Health Department, the Cambria Community Services District (CCSD) has lifted the boil water notice for all affected customers. The water is safe to drink and use as usual.

How We Got Here

Summary – Stuart Street Tank Failure and Boil Water Notice

On the morning of September 12, the Stuart Street Tank experienced an equipment failure caused by a malfunctioning level transducer. The transducer stopped sending accurate readings to the site’s Programmable Logic Controller (PLC). When the signal was lost, the system held the last known tank level instead of dropping as tank levels dropped. This made the Supervisory Control and Data Acquisition (SCADA) system believe the tank level was stable, and communications were regular when, in fact, the tank was emptying. As the tank continued to drain, it eventually became empty overnight, leading to a loss of pressure in the water distribution system for the affected pressure zone (Zone 2 in Lodge Hill).

When water system pressure drops below safe operating levels, there is an increased risk that contaminants could be drawn into the water system through backflow or leaks. Because of this public health risk, state regulations require the District to issue a boil water notice anytime there is a pressure loss until water quality samples confirm the water is safe to drink.

In response, the CCSD:

• Refilled and repressurized the Stuart Street Tank
• Flushed the water system through fire hydrants
• Issued a boil water notice to all customers in the affected zone
• Conducted door-to-door notifications and provided bottled water at the Cambria Veterans Hall
• Replaced the tank’s level transducer, PLC power supply, and network switch
• Implemented new flatline and watchdog alarms as part of the Phase 3 SCADA upgrade to an Allen-Bradley PLC platform
• Added advanced level-monitoring algorithms to prevent similar failures in the future

The District understands the inconvenience this incident has caused and appreciates the community’s patience and cooperation during the response. Protecting public health and maintaining reliable water service remain our highest priorities, and the corrective measures implemented will help prevent a recurrence.

We extend our sincere thanks to CCSD staff who stepped up—many on their days off—to assist with this emergency response, and to the Cambria Community Emergency Response Team (CERT) for providing vital support when it was needed most.

Sincerely,

Matthew McElhenie