VIHA Policy Drinking Water Treatment for Surface Water Supplies

I have been looking for this document for a very long time. I have seen VIHA’s 4-3-2-1 (4321) 4 Log Policy referenced many times but have not been able to find it. Until now. Click here to learn more or read an excerpt below. One thing that does bother me is why the document was so difficult to find. It is our health they are risking and taking chances with.

VIHA 4 Log Drinking Water Policy 2007


Since November, 2007

The Drinking Water Protection Act requires that all water supply systems provide potable water. The Drinking Water Protection Regulation further states that drinking water originating from surface water must be disinfected.

This policy characterizes the level of treatment for surface water expected by VIHA and should provide for adequate removal or inactivation of pathogenic organisms that may be present in raw water. Turbidity and situations when filtration may not be required are also addressed.

1. All water supply systems in VIHA that use surface water sources will be required to
maintain the following treatment specifications:

4-log removal/inactivation of viruses
3-log removal/inactivation of Giardia cysts and Cryptosporidium oocysts
2 treatment processes, usually filtration and disinfection
1 NTU turbidity (maximum) in finished water

2. Under the following conditions, a water supply system may be permitted to operate
without filtration:

a. Average daily source water turbidity levels measured at equal intervals (at least
every 4 hours) – 1 NTU or less (95% of days) and not above 5 NTU on more
than 2 days in a 12 month period.
b. Escherichia coli 20/100ml or less in 90% of source water samples.
c. Two primary disinfectants are provided, which together achieve a 4-log
removal/inactivation of viruses and 3-log reduction in Giardia and

3. The Drinking Water Officer may require additional/alternative treatment to address any
of the following:

a. High bacterial counts or risk of fecal contamination of source water.
b. High organic matter that may result in unacceptable levels of disinfection by-
c. Chemical or other contaminants than may affect potability.


New Water Supply Systems

Applications from new water supply systems, which include a surface water source and are
received after the effective date of this policy, will need to be in compliance with the policy
before a construction permit or operating permit is issued.

Existing Water Supply Systems

Staff responsible for drinking water systems will implement this policy for existing systems as follows:

1. Identify all water supply systems that use surface water and serve more than 500 persons per day.
2. Send a standard letter to each water supplier stating that the Vancouver Island Health Authority is consulting with them under Section 8(4) of the Act with regard to the proposed attachment of the following condition to their operating permit, “By (date to be determined), this system will provide 2 treatment processes acceptable to VIHA, achieve a 4-log removal/inactivation of viruses and 3-log removal/inactivation of parasites, and produce a finished water with less than 1 NTU turbidity.”
Enclose other information as appropriate and request written comments within 30 days.
3. Consider the comments received, and complete any other consultations necessary to determine the final wording of the condition to be placed on the operating permit,
including the date by which the condition is to be met.
4. Amend the operating permit.
5. Obtain an implementation strategy from the water supplier, and monitor progress leading to compliance with the conditions on the operating permit.


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