Groundwater Professional Bulletin Board

Plastic Water Line Sampling

PLASTIC WATER LINES IN THE ACTUAL PLUME
We have received a number of RBCA reports where the certified groundwater professional has not conducted the sampling of plastic water lines located in actual contamination plumes. We consider this to be a serious report deficiency relating to risk determination and may cause the report to be rejected. Site evaluation guidance concerning the sampling of drinking water in plastic water lines is found on pages 39 (section 3.5.2) and 40 (section 3.6.3) of the Tier 2 Guidance document.

PLASTIC WATER LINES IN THE SIMULATED PLUME
We are modifying the sampling requirement as follows:

Instead of sampling all the plastic water lines located in the Plastic Water Line Receptor ID (RID) Plume, groundwater professionals only need to sample those lines that are within 100 feet of the largest actual plume exceeding the plastic water line target levels. Actual plumes refer to both soil and groundwater plumes, for all chemicals of concern.

For nongranular bedrock sites, where the groundwater plume does not have to be defined, sample all lines within 200 feet of any point which exceeds a plastic water line target level. At a minimum, for nongranular bedrock sites, sample all lines within 200 feet of the suspected source.

PLASTIC WATER LINE SAMPLING RESULTS. When plastic water lines are sampled, we are requiring the following information be provided with the Tier 2 submittal (as part of Appendix 24):

1. a description of the water line sample location,
2. a description of the water line sampling methods (including a copy of the calculations used to determine the volume of water between the impacted line area and sampling location),
3. >time and date of sampling,
4. analytical sample results and summary of data, and
5. a justification from the groundwater professional indicating why the sampling procedures produce representative results.

NOTE: if elevated contaminant levels are detected in the water samples, this department and the local health department must be notified immediately.

Contact Elaine Douskey at (515)281-8011 or elaine.douskey@dnr.iowa.gov if you have questions concerning this posting.