ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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arse TABLE B.4-4 Redox Conditions and Potential Degradation Pathways Is Is Ferrous Is Prevailing redox redox depth of well Dissolved Is Nitrate Iron Is Sulfate Methane Redox Condition redox indicates indicates vinyl screen Well Location Oxygen >0.5 >0.1 >0.5 Detected Based on indicates TCE cDCE chloride Well ID ft b s Aquifer Zone (Figure 4-1 >1 mg/L? mg/L? mg/L? mg/L? ? Indicators: degrades by: degrades by: degrades by: Comments M-31 C1 120 - 125 Intermediate south of WWTP no no no yes yes methanogenic RD++++ RD++++ RD+++ TH-10 133- 158 Intermediate south of WWTP no no no yes yes methanogenic RD++++ RD++++ RD+++ Fe data from Table B.4-2 M-1 7B 25-45 Upper south of WWTP yes yes NM yes no oxic CM++ AM+++ AM++++ M-1 7A 86- 106 Upper south of WWTP no no NM yes no sulfate reducing RD++++ RD+++ RD++ M-17C1 123- 133 Intermediate south of WWTP no no no/yes yes yes methanogenic RD++++ RD++++ RD+++ Fe = 0.6 mg/L in 2008 (Table B.4-2) M-20C1 140- 150 Intermediate south of WWTP no no no yes yes methanogenic RD++++ RD++++ RD+++ Fe data from Table B.4-2 M-20D 205-225 Lower south of WWTP no no NM yes no sulfate reducing RD++++ RD+++ RD++ M-26C2 180- 195 Intermediate south of WWTP no yes no yes yes methanogenic RD++++ RD++++ RD... nitrate = 1.1 mg/L; near threshold M-41 D 205 -225 Lower north of WWTP no no NM yes no sulfate reducing RD++++ RD+++ RD++ M-813 21 -41 Upper Stockton area yes yes no yes no oxic CM++ AM+++ AM++++ Fe data from Table B.4-2 M-8A 91 - 111 Upper Stockton area no no NM yes no sulfate reducing RD++++ RD+++ RD++ M-8C1 142- 162 Intermediate Stockton area no no no yes no sulfate reducing RD++++ RD+++ RD++ Fe data from Table B.4-2 M-8D 208-228 Lower Stockton area no yes NM yes no nitrate reducing CM+ AM+ AM+ nitrate = 1.3 mg/L M-54C 155 - 175 Intermediate Stockton area no no NM yes no sulfate reducing RD++++ RD+++ RD++ M-1 B 21 -41 Upper on site yes yes NM yes no oxic CM++ AM+++ A ++++ EU-3 50-65 Upper on site yes yes NM yes no oxic CM++ AM+++ AM++++ EU-4 50-65 Upper on site yes yes NM yes no oxic CM++ AM+++ AM++++ EW-1 99- 119 Upper on site no yes NM yes no nitrate reducing CM+ AM+ AM+ M-25C1 148- 158 Intermediate on site yes yes NM yes no oxic CM++ AM+++ AM++++ M-25C2 176- 186 Intermediate on site yes yes NM yes no oxic CM++ AM+++ AM++++ M-66 23-43 Upper near site yes yes no yes no oxic CM++ AM+++ AM++++ Fe data from 2008 M-49A 50-60 Upper near site yes yes NM yes no oxic CM++ AM+++ AM++++ M-6A 90- 110 Upper near site no yes NM yes no nitrate reducing CM+ AM+ AM+ DO data from Q2 2010 M-6C1 129- 139 Intermediate near site no yes no yes no nitrate reducing CM+ AM+ AM+ Fe data from 2008 M-6C2 177- 187 Intermediate near site no yes no yes no nitrate reducing CM+ AM+ AM+ Fe data from 2008 M-6D 208-238 Lower near site yes yes NM yes no oxic CM++ AM+++ AM++++ DO may be biased; Q3 result only M-1 OA 92 - 112 Upper north of site yes yes NM yes no oxic CM++ AM+++ AM++++ M-10C1 162- 172 Intermediate north of site yes yes NM yes no oxic CM++ AM+++ AM++++ Note Redox determination is based on threshold concentrations as described in McMahon and Chapelle, 2008 but modified to include dissolved methane and a 1 mg/L DO threshold, due to detection limits of data. Abbreviations ft bgs =feet below ground surface Biodegradation Pathways: mg/L=milligrams per liter AM Aerobic Mineralization Fe=ferrous iron CM Cometabolic Mineralization DO=dissolved oxygen RD Reductive Dechlorination (i.e., dehalorespiration) Q2=2nd quarter Q3=3rd quarter number of+' symbols indicates the relative efficiency of degradation under the specified redox condition (adapted from Bradley and Chapelle, 2010) NM=not measured More data is needed to evaluate the viability of this process based on site specific conditions. Redox conditions indicate biodegradation by the pathway specified under the prevailing redox conditions could occur Rapid biodegradation by the pathway and redox conditions specified is anticipated AMEC Geomatrix, Inc. Page 1 of 1 \\oad-fs1\doc_safe\9000s\9837.006\4000 REGULATORYTS Assessment_Apx B_012711\Attachment B.4\Table B.4-4.x1s