July 24, 2018

RE:  Review of three groundwater data and modeling documents

 Former Koppers Facility, Wauna, Oregon

ECSI No. 649

Dear Messrs. Paschl and Hassett,

The Oregon Department of Environmental Quality (DEQ) has reviewed three documents presenting groundwater monitoring and analytical data collected in 2017 and 2018 (citations below). These three documents were prepared on your behalf by Amec Foster Wheeler (now Wood Environment and Infrastructure Solutions).

DEQ reviewed analytical data sets representing groundwater samples collected on April 18, 2017, October 13, 2017 and April 2, 2018. The data indicate an improving groundwater quality trend, which supports 2016 natural attenuation modelling predictions. The improving groundwater quality trend appears to be protective of the Columbia River and meets Level II Ecological Risk Screening Level Values at the two points of compliance established for the site.

The three consecutive groundwater data sets collected in 2017 and 2018 were reviewed in light of the evaluation criteria provided below. The reviewed data were all well below any triggering concentrations established for the site.

From 2016 Monitored Natural Attenuation document, Page 21:

Groundwater Quality Evaluation

The groundwater quality at monitoring wells ATT-03, ATT-04, and ATT-11 will be evaluated after each monitoring event to assess the effectiveness of natural attenuation and the need to implement the contingent remedy. The contingent remedy would be triggered by either of the following two events:

1. The detected concentration(s) of one or more COCs at western POC wells ATT-12 or PMW-7R exceeds one-half of the respective Level II SLV(s) for two consecutive semi-annual monitoring events.

2. The detected concentration(s) of one or more COCs at Western Discharge Area wells ATT-11, ATT-04, or ATT-03 (located up gradient of the POC) exceeds the respective Level II SLV(s) for two consecutive semi-annual monitoring events.

If either of the above events occurs, DEQ will be notified via email within one week after receiving final analytical results from the analytical laboratory. The contingent remedy (described in Section 5.2.2, sic) will be implemented following DEQ notification.

Please review site groundwater data to determine if a case can be made to support regulatory closure of the groundwater to surface water pathway as present no unacceptable risk.

Please feel free to call me with questions.

Sincerely,

Kenneth Thiessen, CEG

Northwest Region Cleanup Section

cc:    Christy Duitman, RG, Wood

   Joel Eledge, CHMM, Wood

   L. Littlejohn, Georgia Pacific

ECSI #649

References Cited:

2016. Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler), Final Report: Monitored Natural Attenuation Demonstration, Former Koppers Facility, Wauna, Oregon, March 31.

2017. Amec Foster Wheeler, 2017 Annual Operations, Maintenance, and Monitoring Report, Former Koppers Facility, Wauna, Oregon, April 20.

2018. Wood Environment & Infrastructure Solutions, Inc., 2018 Semi-annual Progress, Operations, Monitoring and Maintenance Report, Former Koppers Facility, Wauna, Oregon, July 2.