From: Soren Hill

Sent: Fri Apr 12 11:09:46 2024

To: PUGH Mark * DEQ

Cc: Andie Fitzgerald; Lisa Thompson; Chuck Esler

Subject: Former 5 Star Cleaners – 1Q 2024 Quarterly Report

Importance: Normal

Attachments: image001.jpg; 2024-Q1 Tables.pdf; 01_January O& M Inspection Report & Field Notes.pdf; 02_February O& M Inspection Report & Field Notes.pdf; 03_March O& M Inspection Report & Field Notes.pdf; Pace Labs_L1711184-Report.pdf; ALS Labs_2406436-Report.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 first 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 January 11, February 28, and March 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 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 February 28, 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 February 21 and 28, 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 detected in the Pits Exhaust from the vapor collection pits at a concentration of 0.4 part per million (ppm) in January 2024 and were not detected in February or March 2024.
  • * VOCs were detected in the Pre-Carbon Effluent from the vapor recovery wells at concentrations of 47 ppm in January 2024, 28 ppm in February 2024, and 23 ppm in March 2024.
  • * VOCs were not detected in the Post-Carbon Effluent from the vapor recovery wells in January, February, or March 2024.
• * Positive pressure was measured at the exhaust stack for the vapor pits collection system in January, February, and March 2024, indicating the system is functional.
• * A vacuum was observed at the carbon inlet for the recovery wells in January, February, and March 2024, indicating the system is functional.
• * A vacuum differential ranging from 0.003 to 0.009 inch of water column was measured at vapor points VP-5 through VP-8 during January, February, and March 2024 monitoring, except February 2024, when no vacuum differential was measured at vapor point VP-8.
  • * Readings from the first quarter O&M indicate that the system is functional.
• * Radon fan evaluation: Farallon’s review of historical subslab pressure differential data determined that the system is functioning as designed and that replacing the existing radon fan is not warranted at this time. Radon fan operation will be reevaluated in the event that the former dry cleaner space becomes occupied or PID readings at vapor point VP-8 increase.

Pre- and post-carbon and indoor and outdoor ambient air sampling analytical results from the February 2024 sampling event are presented in Tables 3 and 4, respectively. The results are summarized as follows:

• * The carbon treatment of extracted vapors is operating as intended. The laboratory report is provided as an attachment. Relevant results are noted below:
  • * Emissions from the system were less than the limits listed in the Consent Judgment, served on June 10, 2021, of 2,300 micrograms per cubic meter (µg/m³) for PCE and 88 µg/m³ for TCE.
  • * Removal of 99.85 percent of PCE was achieved (54,800 µg/m³ pre-carbon to 84.9 µg/m³ post-carbon).
  • * Removal of TCE, cis-1,2-dichloroethene, and trans-1,2-dichloroethene post-carbon was achieved to concentrations less than laboratory reporting limits.
• * Analytical results for ambient air samples collected between February 21 and 28, 2024 indicated PCE concentrations at all sample locations were less than applicable Risk-Based Concentrations (RBCs) for Air Inhalation (Occupational at 47 µg/m³, Urban Residential at 26 µg/m³, and/or Residential at 11 µg/m³) and ranged from 0.33 to 3.9 µg/m³. TCE concentrations at all sample locations were less than the RBCs (Occupational at 2.9 µg/m³, Urban Residential at 1.0 µg/m³, and/or Residential at 0.47 µg/m³) and less than the laboratory reporting limit. The laboratory report is provided as an attachment.

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 January, February, and March O&M events. Approximate volumes of accumulated water removed from the subsurface piping system during the O&M events were 0.8 liter in January, 0.4 liter in February, and 0.1 liter in March 2024. 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.
• * The ethanol concentration in the post-carbon air sample was detected at 2,810 µg/m³, but the concentration remains less than the odor threshold of 100 ppm (188,417 µg/m³) or the Occupational Safety and Health Administration Permissible Exposure Level of 1,000 ppm.

Actions scheduled in the next 3 months:

• * Conduct monthly O&M visits in April, May, and June 2024.
• * In the event rainfall occurs in the upcoming months, check the piping system for water accumulation.
• * Update O&M Manual project personnel contact information to reflect current project team members (see below).

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

Thank you,