From: PUGH Mark * DEQ

Sent: Wed Jan 15 15:47:51 2025

To: Lisa Thompson

Cc: Andie Fitzgerald; Suzy Stumpf

Subject: RE: Former Five Star Cleaners (2305 SW 6th Avenue) – Q4 2024 Quarterly Progress Report

Importance: Normal

Attachments: image001.png;

Thanks Lisa.

It would be helpful to include a statement on indoor air concentrations with respect to screening criteria.

The lack of measurable vacuum in VP-5 through 8 should be noted as a potential problem. If the fan is no longer operational it needs to be replaced as part of the site remedy installed by DEQ. Please be prepared to trouble-shoot this issue and replace the fan as needed during the next monitoring event or ASAP if that monitoring event has occurred and the issue has not yet been resolved.

It is not necessary to revise this report. Thanks again, and let me know if you have any questions or would like to discuss.

From: Lisa Thompson <lthompson@farallonconsulting.com>

Sent: Tuesday, January 14, 2025 11:46 AM

To: PUGH Mark * DEQ <mark.pugh@deq.oregon.gov>

Cc: Andie Fitzgerald <afitzgerald@terwilligerplaza.com>; Suzy Stumpf <sstumpf@farallonconsulting.com>

Subject: Former Five Star Cleaners (2305 SW 6th Avenue) – Q4 2024 Quarterly Progress Report

Mark,

This email provides a quarterly progress report for the former Five Star Cleaners property at 2305 Southwest 6th Avenue (DEQ ECSI Site ID No. 6276) (herein referred to as the Site). This progress report is being submitted for the fourth quarter of 2024, on behalf of Pacific Skyline Holdings II, LLC. Also attached is the revised Operation and Maintenance Manuel with updated project personnel.

Actions taken during the previous 3 months:

• * Farallon conducted monthly operation and maintenance (O&M) visits to document the Site’s Vapor Collection System performance on October 24, November 12, and December 23, 2024. Monthly O&M activities included monitoring the following parameters:

o Concentrations of volatile organic compounds (VOCs) were measured using a hand-held photoionization detector (PID) at select monitoring points, including at the vapor collection system, subslab vapor points, and vapor recovery wells. PID readings are summarized in Table 1 (attached).

o Differential pressures were measured at the subslab vapor points (VP-5 through VP-8) using a hand-held vacuum gauge (Figure 2). Differential pressure readings are summarized in Table 2 (attached).

• * Semiannual air samples were collected from the influent (pre-carbon) and effluent (post-carbon) lines of the vapor granular activated carbon treatment vessels using Summa canisters on October 24, 2024. The samples were submitted to Pace Analytical laboratories for analysis using U.S. Environmental Protection Agency (EPA) Method TO-15 for VOCs including but not limited to tetrachloroethene (PCE) and trichloroethene (TCE). Analytical results for the vapor collection system are shown in Table 3 (attached). The analytical report is also attached.
• * Indoor and outdoor ambient air samples were collected using Radiello badges between October 16 and 24, 2024. The samples were submitted to ALS Environmental laboratories for analysis for PCE and TCE by EPA Method TO-17. Ambient air analytical results are shown in Table 4 (attached). The analytical report is also attached.

Summary of monitoring data and sample analytical results for the previous 3 months:

Monthly O&M field reports are attached. PID readings are tabulated in Table 1, and vacuum and pressure readings are tabulated in Table 2 (attached).

• * PID readings from vapor collection system exhaust were as follows:
  • * VOCs were not detected in the Pits Exhaust from the vapor collection pits in October, November, or December 2024.
  • * VOCs were detected in the Pre-Carbon Effluent from the vapor recovery wells at concentrations of 15 parts per million (ppm) in October, 31 ppm in November, and 23 ppm in December 2024.
  • * VOCs were not detected in the Post-Carbon Effluent from the vapor recovery wells in October, November, or December 2024.
• * Positive pressure was measured at the exhaust stack for the vapor pits collection system in October, November, and December 2024, indicating the system is functional.
• * A vacuum was observed at the carbon inlet for the recovery wells in October, November, and December 2024, indicating the system is functional.
• * A vacuum ranging from 0.003 to 0.009 inches of water column was measured at vapor points VP-5 through VP-8 during October and November 2024 monitoring. Vacuum was not measurable at vapor points VP-5 through VP-8 during the December 2024 monitoring. If VP-5 through VP-8 continue not to have measurable vacuum, then Farallon will assess whether a replacement radon fan is required to improve system performance.

A description of any problems experienced during the previous 3 months and actions taken to resolve them:

• * The subslab vapor collection pit piping was checked for the accumulation of water during the October, November, and December 2024 O&M events. Accumulated water ranged from approximately 1 to 2 cups in volume that was removed from the subsurface piping system during the October, November, and December 2024 O&M events. Water removed from the subsurface piping system is collected and stored on-Site in a lidded 5-gallon bucket pending appropriate analytical testing and disposal.

Actions scheduled in the next 3 months:

• * Conduct monthly O&M visits in January, February, and March 2025.
• * Conduct semi-annual vapor sampling and indoor air sampling in February 2025 (see attached Site Plan for monitoring locations and O&M Manual for sampling details).
• * In the event rainfall occurs in the upcoming months, check the piping system for water accumulation.

If you have any questions about the information provided in this progress report, please do not hesitate to contact us.

Project Manager: Lisa Thompson, P.E., Associate Engineer

Farallon Consulting, L.L.C.

Phone: (425) 395-4636

Email: lthompson@farallonconsulting.com

Technical Contacts: Lisa Thompson, P.E., Associate Engineer

Farallon Consulting, L.L.C.

Phone: (425) 395-4636

Email: lthompson@farallonconsulting.com

Suzy Stumpf, P.E., Principal Engineer

Farallon Consulting, L.L.C.

Phone: (303) 489-1032

Email: sstumpf@farallonconsulting.com

Regards,

This correspondence contains confidential or privileged information from Farallon Consulting and may be "Attorney-Client Privileged" and protected as "Work Product." The information contained herein is intended for the use of the individual or party named above. If you are not the intended recipient, note that any copying, distribution, disclosure, or use of the text and/or attached document(s) is strictly prohibited. If you have received this correspondence in error, please notify us immediately. Thank you.