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Table F-10. Groundwater pH Data for Excavation Sequencing Area H <br />Project No. 110207, Everett, Washington <br />Date LP-MW-1 SHB-MW-102* SHB-MW101 LP-MW-2 SHB-MW-2 <br />8/31/2020 7.04 7.28 6.84 6.52 6.69 <br />9/2/2020 7.07 7.30 6.83 6.50 6.63 <br />9/3/2020 7.24 7.31 6.82 6.54 6.61 <br />Average Baseline 7.12 7.30 6.83 6.52 6.64 <br />"Trigger pH"7.62 7.80 7.33 7.02 7.14 <br />9/14/2020 7.52 7.35 7.52 <br />9/22/2020 7.20 7.30 <br />9/28/2020 9.72 7.20 <br />9/29/2020 10.52 inaccessible* 6.85 <br />10/1/2020 10.84 6.85 6.71 6.60 <br />10/2/2020 10.85 <br />10/5/2020 11.34 6.87 6.95 7.13 <br />10/7/2020 11.30 6.98 6.97 7.06 <br />10/9/2020 11.38 6.99 7.02 7.13 <br />10/12/2020 11.60 7.07 6.57 6.66 <br />Notes <br />Red highlighted values exceed Trigger pH value. <br />*: The driller decommissioning wells in an adjacent area inadvertently decommissioned this well on 9/29. <br />Well SHB-MW-101, located 25 feet from this well, is substituted as a proximal well for the rest of the <br />monitoring. <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 />pH Reading in Standard Units <br />Proximal Wells <br />Downgradient Wells <br />to Monitor if pH Increase <br />>0.5 unit is Observed in <br />Proximal Well(s) <br />Baseline Readings for this Sequencing Area (3x in 1 week) <br />Weekly (at least) Compliance Readings During CM Removal in this Sequencing Area <br />Weekly (at least) Compliance Readings for 3 Weeks After CM Removal is Done in this <br />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-10 <br />Report for Second Interim Action <br />Page 1 of 1