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Andrew Richle - 2 - May 18, 2020 (pg/L). After switching extraction to EW-6, the influent concentration started at 2,100 pg/L, decreased to 100 pg/L by January 2013, and had further decreased to between 37 and 46 pg/L as of fourth quarter 2013. In total, 1.3 pounds of PCE was removed from EW-4 and EW-5 and 21.4 pounds of PCE was removed from EW-6. PCE concentrations in the seven wells monitored during the GWET rebound study evaluation showed a declining trend and have remained significantly below pre-remediation PCE concentration levels. For example, PCE in MW-09 decreased from 140,000 pg/L in June 2001 to 20 pg/L in April 2020. PCE in G-05 decreased from 59,000 pg/L in November 2001 to 8.9 pg/L in April 2020. After shutting down the GWET system, the equipment was retained in case it could be connected to new extraction wells installed downgradient of the Central Plume Source Area. However, a separate GWET system was later installed in the mid-plume area of the Central Plume, which continues to operate. In June and August 2019, the City conducted confirmation soil gas sampling in the area of the SVE system using passive soil gas samplers. In total, 16 soil gas samples were collected using quantitative passive soil gas samplers supplied by Beacon Environmental. Soil gas samples were collected over 14-day exposure times. The samples were analyzed by Beacon Environmental for volatile organic compounds including PCE, trichloroethene (TCE), cis-1,2-dichloroethene, and vinyl chloride using EPA Method TO-17. PCE and TCE were detected in all of the passive soil gas samples. PCE concentrations ranged from 4 to 153,000 pg/m3. TCE concentrations ranged from 2 to 4250 pg/m3. The highest concentrations of PCE and TCE were located in samples closest to the sewer line in the alleyway near Pleasant Avenue and decreased significantly away from the sewer. In August and September 2019, the City collected indoor air samples from buildings in the Central Plume Area that were either found to have detectable concentrations during previous indoor air sampling events in 2004 and 2008 or were considered sensitive receptors such as schools. No residences were sampled. In total, 16 indoor air samples and 9 outdoor ambient air samples were collected using passive sorbent samplers supplied by Beacon Environmental. Air samples were collected over 72-hour or 96-hour exposure times. The samples were analyzed by Beacon Environmental for PCE, trichloroethene, cis-1,2-dichloroethene, and vinyl chloride using EPA Method TO-17. PCE was detected in 9 indoor air samples and one outdoor air sample. No other constituents were detected. Two sample locations contained PCE greater than 1.0 but less than 2.0 micrograms per cubic meter (pg/m3). A sample location at St. Anne's Parish office contained PCE at a concentration of 12.3 pg/m3. This location was subsequently retested and found to contain 2.91 pg/m3 of PCE. The St. Anne's Parish office was previously sampled in 2008 and had been non-detect (less than 0.24 pg/m3)