SITE INFORMATION AND CORRESPONDENCE

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2 Discussion of 2M8 Treatment System Activities Treatment system operation and monitoring was conducted on a monthly basis during Q2 and Q4 2018, when the treatment system was operating. Monitoring included recording extraction well parameters, sampling the treatment system effluent for VOCs and 1,4-dioxane, and performing as-needed maintenance of the treatment system and appurtenances. Over 36 million gallons of groundwater were treated and discharged to the retention/infiltration basin during the periods of operation in 2018 (April 4, 2018-July 6, 2018 and October 4, 2018-December 14, 2018). The total volume of groundwater pumped and treated between April 4 and July 6 was 17,316,260 gallons and the average flow rate was 154 gallons per minute. The uptime in Q2 was approximately 100%. There were two brief periods of downtime,on April 19 and May 22; however,they were short enough thatthey had a negligible effect on the percent uptime in 2018 The total volume of groundwater pumped and treated between October 4 and December 14 was 19,006,260 gallons and the average flow rate was 153 gallons per minute.The uptime in Q4 was 100%. 2.1 Treatment System Monitoring Treatment system monitoring was conducted in 2018 in accordance with MRP R5-2017-0125. Sampling dates are listed in Table 1, Extraction Well and Treatment System Effluent and Injection Monitoring, and Table 2, Treatment System Effluent and Injection Monitoring, which also contain results from the monitoring and sampling events. Samples were collected from the treatment system effluent and analyzed for VOCs and 1,4-dioxane(Table 2).Water- quality parameters, including pH,electrical conductivity,and temperature,were measured in the field (Table 1). VOCs and 1,4-dioxane were not detected above their respective reporting limits in any of the treatment system samples collected from the treatment system effluent(Table 2). Because treated groundwater is currently discharged to the retention/infiltration basin, applicable monitoring parameters according to MRP R5-2017-0125 include injection rate,total volume of water injected,and water level. These parameters are reported in Table 1.Other systems monitored on a monthly basis include the extraction wells. Extraction rate,volume of water extracted, pressure,and water-level measurements for each of the extraction wells are recorded monthly and are reported in Table 1. 2.2 Treatment System Operation and Maintenance This section presents operation and maintenance activities performed during 2018. This information is also included in the monthly operation and maintenance reports submitted to the DTSC and CVRWQCB on the 15th of each month. As discussed in the post-closure permit application(Dudek 2017b),the treatment system was pulsed in approximately 3-month cycles in an effort to increase removal efficiency and further decrease concentrations of CDCs at the site. The treatment system was shut down on January 3, 2018, which began the first three-month planned shutdown D U D E K 10886-1 5 March 2019