|
2011 Semiannual Groundwater Monitoring and Evaluation Report
<br /> Full-Scale In Situ Hexavalent Chromium Reduction Treatment Implementation
<br /> Former Marley Cooling Tower Site, Stockton,California January 2012
<br /> 3.1.3 Northern Injection Area Wells
<br /> Baseline well sampling results represent conditions within and around the current established Cr
<br /> plume boundary and areas of treatment. Quarterly well sampling results track the performance
<br /> of the treatment by quarter.
<br /> Consistent with the WDR, the last two 2011 quarterly monitoring and sampling events included
<br /> MW-1, MW-2, MW-8, MW-101, MW-102, MW-104 (S-2), MW-105, MW-106, MW-207,
<br /> MW-208, MW-213 (I-7), MW-300, MW-323, MW-361, TW-12, and TW-13 in the northern area
<br /> of the Site to obtain information on groundwater quality. Wells MW-6, MW206, MW214 (I-8)
<br /> and MW-320 continued with quarterly sampling and wells EW-3, EW-4, EW-5, MW-4, and
<br /> MW-212 were sampled during the last two 2011 quarterly events, though they are not required
<br /> by the MRP. During an August 2011 supplemental sampling event wells MW-4, MW-102,
<br /> MW-104 (S-2), MW-212, and MW-213 (I-7) were sampled to support preparation of the
<br /> Proposed Work Plan for Focused Supplemental Hexa valent Chromium Reduction as Part of the
<br /> In Situ Remedial Action Plan Amendment Activities(MWH, 201 lb) which was submitted to the
<br /> CVRWQCB and DTSC on 20 October 2011. It should be noted that wells MW-102 and MW-
<br /> 104 were sampled during the 3rd quarter as part of the August supplemental sampling, as they
<br /> could not be sampled during the regular July event due to broken pumps.
<br /> 3.1.4 Southern Injection Area Wells
<br /> Consistent with the WDR, the last two 2011 quarterly monitoring and sampling events included
<br /> MW-9, MW-204 (S-8), MW-205 (S-7), MW-301, MW-303, MW-321 (I-9), MW-322, MW-324
<br /> (I-10), TW-14, TW-15, TW-16, TW-17, MW-447S, MW-447D, MW-448S, and MW-448D to
<br /> obtain information on groundwater quality. Wells EW-1 and I-11 continued with quarterly
<br /> sampling, though they are not required by the MRP.
<br /> 3.2 GROUNDWATER ELEVATION, ESTIMATED GRADIENT, AND
<br /> LINEAR VELOCITY
<br /> Potentiometric surface maps were prepared by Dudek for the Shallow, 100-Foot Sand, and
<br /> Intermediate zones using groundwater data collected in July and October 2011. Depth-to-
<br /> groundwater and groundwater-elevation measurements are presented in Table 4. Potentiometric
<br /> (a MWH,
<br /> 3-3
<br />
|