Groundwater Professional Bulletin Board

Confirmation Sampling Update

The following provides additional guidance for conducting RBCA confirmational sampling at LUST sites.

Groundwater - Confirmation sampling is required at the groundwater maximum for a Tier 2 which classifies the site NAR, unless:

(a) there are already at least two samples at the groundwater maximum which confirm the NAR site classification AND concentrations do not increase more than 20% from the previous sample;

OR

(b) contamination is less than the Tier 1 level for groundwater vapor to enclosed space,

OR

(c) the site would be classified NAR regardless of the results of further sampling (For example, soil gas was passed at the maximum, and the other groundwater pathways are not complete.) Justification must be provided to explain why higher concentrations would still result in NAR classification.

Soil - no confirmation sampling required.