2021.04.07_CCO.p14_DEQSampleRetentionGuidance

DEQ Sample Retention Guidance
April 7, 2021

In addition to the samples that Chemours listed in its sample retention proposal, DEQ would like to
request that Chemours also retain the following samples:

1. Representative onsite annual groundwater (GW) samples with a range of detectable results
– 20%+ per sampling event, going back as far as samples are available;
2. Representative offsite annual GW samples with a range of detectable results – 20%+ per
sampling event, going back as far as samples are available;
3. Representative offsite private well water with a range of detectable results – 20%+ per
sampling event, going back as far as samples are available, and 100% of other offsite
drinking water samples (such as community wells) except as defined in 4 and 5 below;
4. All onsite GW, offsite GW, and drinking water samples from Sept 1, 2018 until Jan 1, 2019
(around Hurricane Florence);
5. All GAC and RO Pilot Program testing samples (Raw, mid and post samples);
6. 100% of pre-RTO (thermal oxidizer) environmental samples, including soil, sediment, surface
water, pore water, groundwater, and any other samples that were collected;
7. All the rainwater samples that Chemours has taken or will take that have detectable levels
of any PFAS compounds;
8. Representative environmental samples including soil, sediment, surface water, pore water,
groundwater, and any other samples that were collected post-RTO installation (Dec. 2019)
with detectable levels of PFAS, 20%+ per sampling event;
9. Any samples of Chemours or non-Chemours process wastewater, non-contact cooling
water, stormwater, or other wastewater conveyance samples such as from or near the terra
cotta pipe and wood-lined ditch or wastewater treatment system;
10. All samples that were split with DEQ;
11. All stack testing samples, including before and after the RTO;
12. Chain-of-custody records to show how Chemours will prevent premature disposal of
samples;
13. A description of sample security measures; and
14. A description of proper sample disposal/destruction methods.

Finally, DEQ requests that Chemours send a spreadsheet of proposed samples and sample materials for
destruction to DEQ for approval at least 60 days before such destruction takes place. This spreadsheet
must include sampling date or date range for each sample or sample group, a description of the sample
or sample group, and correlate each sample or sample group listed with one of the above-listed items.