Advisory for OLALLA Water System, British Columbia

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OLALLA Water System

Type: Boil Water  -  Active

Issued: 6/9/2025

Details:

June 9 BWN remains in effect and Temporary Chlorination will be suspended to facilitate further bacteriological testing as part of on-going efforts to pinpoint the source of the contamination.  

Total coliforms and background bacteria have been periodically reported in water system samples since August 2024. The most recent BWN (issued April 24) is the result of an increase in the frequency and quantity being reported.  

In the report dated May 23: Total Coliform bacteria are present throughout the distribution system, including the storage Reservoir and No Total Coliform bacteria were reported from the source well. Based on the level of bacteria reported, the RDOS decided to reinstate the temporary chlorination.

RDOS on-going efforts to determine the source of the contamination entering the system include:
•	Enhanced bacteriological sampling, 
•	Extensive flushing of the distribution system, 
•	Temporary chlorination (October 11, 2024 to February 18, 2025),
•	WQA (March 13 to 24), 
•	BWN issued April 24,
•	Temporary chlorination (April 30 to May 9), 
•	May 2, 2025, the RDOS hired a contractor with a Remotely Operated Vehicle (ROV) to inspect the inside of the storage Reservoir, and no apparent sources of contamination were noted from this inspection. 
•	Temporary chlorination (May 23 to June 9), 

RDOS is now planning to isolate the storage Reservoir from the distribution system to further determine if the source of contamination is associated with the Reservoir. This will require some additional programming of the pump control system in advance to allow the system to modulate the speed of the Well Pump to continually maintain a set pressure in the distribution system while the Reservoir is isolated. Once this programming is complete, chlorination will again be removed from the system (scheduled for June 9) to allow for bacteriological testing.

The Olalla System consists of a single deep source groundwater well, an elevated storage reservoir and distribution system. The water supply is typically not treated; the system is monitored for potential contamination and undergoes periodic flushes and temporary chlorination as needed. This System has approx. 200 service connections.