From: Soren Hill

Sent: Fri Jul 12 11:48:48 2024

To: PUGH Mark * DEQ

Cc: Andie Fitzgerald; Chuck Esler; Lisa Thompson

Subject: Former 5 Star Cleaners – Q2 2024 Quarterly Report

Importance: Normal

Attachments: image001.png; Q2 2024 Tables.pdf; 04_April 2024 O& M Inspection Form & Field Notes.pdf; 05_May 2024 O& M Inspection Form & Field Notes.pdf; 06_June 2024 O& M Inspection Form & Field Notes.pdf;

Mark,

This email provides a quarterly progress report for the former Five Star Cleaners property at 2305 Southwest 6^th Avenue (DEQ ECSI Site ID No. 6276) (herein referred to as the Site). This progress report is being submitted for the second quarter of 2024, on behalf of Pacific Skyline Holdings II, LLC.

Actions taken during the previous 3 months:

• * Farallon conducted monthly operation and maintenance (O&M) visits for the Site’s Vapor Collection System on April 17, May 16, and June 18, 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. Differential pressure readings are summarized in Table 2 (attached).

• * Semiannual soil vapor samples and indoor air samples were not collected during the previous 3 months. Consistent with the Operation and Maintenance Manual (O&M Manual), the second round of semiannual samples will be collected in October 2024. The results of historical air sampling are summarized in Tables 3 and 4 (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 detected in the Pits Exhaust from the vapor collection pits at a concentration of 0.3 part per million (ppm) in April 2024 and were not detected in May or June 2024.
  • * VOCs were detected in the Pre-Carbon Effluent from the vapor recovery wells at concentrations of 19 ppm in April 2024, 14 ppm in May 2024, and 9.0 ppm in June 2024.
  • * VOCs were not detected in the Post-Carbon Effluent from the vapor recovery wells in April, May, or June 2024.
• * Positive pressure was measured at the exhaust stack for the vapor pits collection system in April, May, and June 2024, indicating the system is functional.
• * A vacuum was observed at the carbon inlet for the recovery wells in April, May, and June 2024, indicating the system is functional.
• * A vacuum differential ranging from 0.003 to 0.011 inch of water column was measured at vapor points VP-5 through VP-8 during April, May, and June 2024 monitoring, except April 2024, when no vacuum differential was measured at vapor points VP-5 and VP-8, and May 2024, when no vacuum differential was measured at vapor point VP-8. Readings from the second quarter O&M indicate that the system is functional.

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 April, May, and June O&M events. Approximately 0.2 liters of accumulated water was removed from the subsurface piping system during the April 2024 O&M event and trace amounts were removed during the May and June 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 July, August, and September 2024.
• * Schedule and planning for the second semi-annual vapor sampling and indoor air sampling to be conducted in October 2024 (see 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: Soren Hill, Project Scientist

Farallon Consulting, L.L.C.

Phone: (503) 880-6230

Email: shill@farallonconsulting.com

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

Farallon Consulting, L.L.C.

Phone: (425) 395-4636

Email: lthompson@farallonconsulting.com

Charles Esler, CHMM, Principal Scientist

Farallon Consulting, L.L.C.

Phone: (503) 816-9874

Email: cesler@farallonconsulting.com

Regards,