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Mr. Brattain October 19, 2020 Page 5 the Environment's(AFCEE's)Monitoring and Remediation Optimization System(MAROS). The ESTAT was used to perform a Mann-Kendall trend analysis on the data to assess the nature of COC, Cr(VI) and permanganate concentration trends with time. It must be noted that as part of this evaluation, Suite B parameters specified in the WDR-MRP (dissolved iron and manganese, total chromium and potassium and total dissolved solids) serve as surrogates to the primary byproducts of ISCO and the determinations made regarding Cr(VI) and permanganate monitoring requirements are also intended to apply to Suite B parameters. In addition, trend plots were developed to visually observe concentration trends in support of the decision-making process. A summary of the data evaluation including Mann-Kendall trend analysis is presented in Table 1. Attachments 1 and 2 present the historical data trends for the COCs and ISCO byproducts (permanganate and Cr[VI])respectively at each monitoring location. As part of the decision-making process,the following two-tiered approach is being used to justify exclusion of wells from the monitoring program or reduction in the monitoring frequency. Tier 1 criteria include the following: I. Is the well needed to evaluate remedy performance? : This criterion evaluates whether the well is located within the current plume footprint and allows for assessment of remedial performance for COCs and Cr(VI). 2. Is the well needed to define the plume boundary? : This criterion evaluates whether the well allows for evaluating plume dynamics and is useful for defining the plume boundary during active remediation. 3. Is the well needed to evaluate groundwater flow characteristics? : This criterion evaluates whether the data from the well allows evaluation of groundwater flow direction and gradients within the treatment zone, and overall site background as part of the remedial performance assessment process. If the well does not satisfy the Tier 1 criteria, it becomes a candidate for exclusion from current monitoring. If the well satisfies the Tier 1 criteria, it will be compared against the Tier 2 criteria listed below to evaluate whether it qualifies for a reduction in monitoring frequency: 1. Historical COC data trends: This criterion evaluates historical trends in COC concentrations to determine whether additional data collection at the current frequency provides continued benefit for performance assessment. For instance, if historical data engineers I scientists I innovators