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Table F-13. Groundwater pH Data for Excavation Sequencing Area C <br />Project No. 110207, Everett, Washington <br />Date PM-MW-7* REC7-MW-3* UST68-MW-5* MW-1 <br />9/21/2020 7.17 7.57 8.12 7.40 <br />9/22/2020 7.16 7.60 8.13 7.43 <br />9/23/2020 7.17 7.57 8.15 7.49 <br />Average Baseline 7.17 7.58 8.13 7.44 <br />"Trigger pH"7.67 8.08 8.63 7.94 <br />10/2/2020 inaccessible* inaccessible* inaccessible*6.84 <br />10/5/2020 6.88 <br />10/12/2020 inaccessible* inaccessible* inaccessible*7.50 <br />10/19/2020 6.79 <br />10/28/2020 7.26 <br />Notes <br />"Trigger pH" for proximal wells is the pH that, if exceeded for 3 weeks, triggers daily monitoring of proximal <br />well and start monitoring of downgradient wells. <br />"Trigger pH" for downgradient wells is the pH that, if exceeded for 1 week, triggers consultation with Ecology <br />regarding response action. <br />*: The driller decommissioning wells in an adjacent area inadvertently decommissioned these wells on 9/29. <br />Therefore, well MW-1 has been substituted as a proximal well for the rest of the monitoring. Other adjacent <br />wells were decommissioned for the OMS excavation. <br />pH Reading in Standard Units <br />Proximal Wells <br />Baseline Readings for this Sequencing Area (3x in 1 week) <br />Weekly (at least) Compliance Readings During CM Removal in this <br />Sequencing Area <br />Weekly (at least) Compliance Readings for 3 Weeks After CM Removal is <br />Done in this Sequencing Area <br />Aspect Consulting <br />12/17/2020 <br />V:\110207 KC Everett Mill\Deliverables\Interim Action Report 2020\Client Review Draft\App F pH monitoring\Appendix F pH Data Tables <br />Table F-13 <br />Report for Second Interim Action <br />Page 1 of 1