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Standard Interpretation



Standard: 2009 TNI
Section: V1M5, Section 1.7.5.b


REQUEST:

Regarding microbiological samples and especially the potentially reduced frequency of checks for absence of chlorine residual for potable water sources (including source water):

1. What are the definitions of "source" and "source water" in this context?

2. What constitutes a unique "source"? Some considerations are:

a. A water body (stream or lake) as a source vs. discrete segments (i.e., random or recurring sampling locations) of the water body as unique sources of source water.

b. Individual wells producing source water.

c. A common aquifer with multiple wells producing source water from that aquifer.

d. A water distribution system as a source vs. individual sampling locations specified in the sampling plan for the distribution system as unique sources.

It seems like the intent of this section was to perform checks to verify removal of chlorine residual from samples from all new potable water sources and random checks for routine samples submitted by long-term customers whose samples satisfy all four conditions in 1.7.5.b.i to iv.

3. What constitutes sufficient documentation or objective evidence that "the laboratory can 'show' that the received sample container are from their laboratory?" For example, IDEXX containers provided by various laboratories to customers are indistinguishable, unless a laboratory marks the containers to show they came from a specific laboratory in a large nationwide chain of laboratories.

TNI FINAL RESPONSE:

(Quality Systems Expert Committee and NELAP AC, 3-31-13)

<em>1. What are the definitions of "source" and "source water" in this context?</em>

"Source water" is defined by EPA as "Untreated water from streams, rivers, lakes, or underground aquifers, which is used to supply private and public drinking water supplies"

<em>2. What constitutes a unique "source"? Some considerations are:

a. A water body (stream or lake) as a source vs. discrete segments (i.e., random or recurring sampling locations) of the water body as unique sources of source water. Check influent point if for drinking water

b. Individual wells producing source water.

c. A common aquifer with multiple wells producing source water from that aquifer.

d. A water distribution system as a source vs. individual sampling locations specified in the sampling plan for the distribution system as unique sources.</em>

It seems like the intent of this section was to perform checks to verify removal of chlorine residual from samples from all new potable water sources and random checks for routine samples submitted by long-term customers whose samples satisfy all four conditions in 1.7.5.b.i to iv.

It is the intent of the standard to verify removal of chlorine residual from all samples that may have been chlorinated. This check is made on <B><U>sample containers</U></B> received by the laboratory, regardless of how they were collected.

<em>3. What constitutes sufficient documentation or objective evidence that "the laboratory can 'show' that the received sample container are from their laboratory?" For example, IDEXX containers provided by various laboratories to customers are indistinguishable, unless a laboratory marks the containers to show they came from a specific laboratory in a large nationwide chain of laboratories.</em>

The intent of this requirement is to ensure that the laboratory is supplying containers with sufficient dechlorination reagent. For the example described above, each laboratory is responsible for verifying their individual supply of containers. Therefore, it is logical to presume that the laboratory has a procedure to ensure that they can identify containers that were provided by their laboratory.

The Committee has proposed a clarification to the multiple uses of "supply" which is currently in the Voting Draft Standard:

1.7.5 Sample Handling

b) Microbiological samples from known chlorinated sources (such as wastewater effluent), unknown sources where chlorine usage is suspected (such a new client or a new source) and all potable water <s>sources</s> <u>supplies</u> (including source water) shall be checked for absence of chlorine residual. Laboratories that receive samples from potable water <s>sources</s> <u>supplies</u> (including source water) that have a demonstrated history of acceptable preservation may check a sample from each <s>source</s> <u>client</u> at a frequency of once per month if: