Call to Rob Ede, Hahn and Associates, Inc., 4 October 2010

I called Mr. Ede to discuss changes to NW Natural’s 2010 groundwater monitoring program for their and Siltronic’s properties. My understanding of the discussions is summarized below by the main topics discussed.

Adding monitoring wells on the Siltronic property – NW Natural proposes adding WS-16-161, WS-17-52, and WS17-94 to the monitoring program, which I approved. I let Mr. Ede know it seemed as if the approach to groundwater monitoring on the Siltronic property was to place wells around the margins of the worst MGP dissolved phase contamination, horizontally and vertically. Mr. Ede acknowledged this was the case. I indicated it would be useful to have monitoring wells in the MGP plume interior and suggested looking at the data for WS-13-69 and WS-13-105. Mr. Ede and I agreed to add these two wells as it appears 1) WS-13-69 is within the MGP plume; 2) WS-13-105 is near the bottom of the MGP plume, and 3) there is data back to the fall of 2003 for VOCs, including benzene and naphthalene; and 4) PAH data for a period of time covering 2-3 years.

Removing wells on the NW Natural property with historic DNAPL occurrence – Four monitoring wells on the NW Natural property with historic occurrence of DNAPL are proposed for removal from the monitoring program, including MW-10-25, MW-11-32, MW-16-45, and MW-18-30.

I approved removing the four wells from the program after discussing previous efforts made by Hahn to collect samples representative of groundwater. I understood from the conversations that Hahn: 1) bails DNAPL from each of the wells before sampling; 2) sampling has occurred after DNAPL removal and waiting later in the monitoring event to collect samples; 3) DNAPL recharge occurs soon after removal and recovers between sampling events; 4) DNAPL removal using a bailer mixes product in water which is then entrained in samples; 5) generally DNAPL properties and water levels do not facilitate use of a peristaltic pump for DNAPL removal; and 5) sample collection at each well takes ~1-day to complete.

Mr. Ede also made it clear that in his opinion the concentration ranges for each well have been established and the ongoing presence of DNAPL confirmed. As such, the data collection objectives for these installations have been met.

During the discussion I mentioned that construction of MW-16-45 could warrant its abandonment. The well is constructed in the upper alluvium and the sand pack extends up to within a foot of the top of the silt unit. Observations made during drilling indicate DNAPL occurs in the silt unit and underlying upper alluvial sand. As such, DNAPL could migrate vertically downward via the sand pack and screen. Also, if the well was being dropped from the monitoring program its only use was for water levels. As such, there could be other wells nearby (e.g., MW-16-65) which could provide similar water level information and groundwater data not influenced by DNAPL. Mr. Ede acknowledged data collected at MW-16-65 could provide similar data, but was hesitant to agree with abandoning MW-16-45. Mr. Ede indicated DNAPL occurred over the length of the sand pack and screen intervals. Based on this information, he felt the well did not represent a conduit for downward vertical movement of DNAPL.

We agreed to further review boring logs for MW-16-45and vicinity and revisit the questions regarding abandonment. We wound the discussion down at this point with me informing Mr. Ede that given the number of annular seal breaches at the site, DEQ would likely be asking NW Natural to compile information regarding wells in areas with DNAPL occurrence so the information was available in a single location. Mr. Ede acknowledged and let me know he would discuss abandonment with NW Natural and Anchor to determine whether MW-16-45 was needed for purposes other than monitoring.