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Diamond Pet Food&Ripon Cogeneration September 27,2013
<br /> Third-Quarter 2013 Groundwater Monitoring Report Page 1 of S
<br /> INTRODUCTION
<br /> This report presents the results of third-quarter 2013 groundwater monitoring performed by
<br /> Lawrence &Associates (L&A) on July 8 and 9, 2013, at Diamond Pet Food Processors of
<br /> Ripon California LLC (DP) and Ripon Cogeneration, LLC (Cogen), 942 South Stockton
<br /> Avenue, Ripon, California(Figure 1). The work was performed in accordance with Waste
<br /> Discharge Requirements (WDR) Order No. R5-2012-0105 for the DP/Cogen site, adopted by
<br /> the California Regional Water Quality Control Board, Central Valley Region(CVRWQCB) on
<br /> October 4, 2012.
<br /> Third-quarter monitoring consisted of measuring the depth to groundwater in monitoring wells
<br /> OB-1, OB-2, OB-4, OB-5, OB-7, OB-8, OB-11, OB-17, OB-19, OB-21, OB-22, OB-24, OB-25,
<br /> OB-26, and OB-28, collecting groundwater samples from the wells and analyzing the samples
<br /> for temperature,pH, electrical conductivity(EC), turbidity, total dissolved solids (TDS), and
<br /> nitrate as nitrogen.
<br /> Table 1 (following text)presents well descriptions including well names, casing diameter,
<br /> reference point elevation, total depth, screened intervals, and aquifer unit(s).
<br /> L&A sampled the wells located on the DP/Cogen site. All offsite monitoring, domestic, and
<br /> municipal wells were sampled by Stantec for the City of Ripon or Environmental Cost
<br /> Management(ECM) for Nestl6s. Field and laboratory results provided by Stantec and ECM
<br /> were used in the preparation of this report and are presented in Attachment A. L&A, however,
<br /> did not review the Stantec or ECM sampling methods or data for accuracy.
<br /> THIRD-QUARTER 2013 GROUNDWATER MONITORING
<br /> FINDINGS
<br /> On July 8, 2013, an east-west trending ridge, originating in the vicinity of the City of Ripon's
<br /> waste-water treatment facility(WWTF)ponds and their fresh-water infiltration pond, was
<br /> present in the semiperched aquifer in the western portion of the DP/Cogen site. The direction of
<br /> the groundwater gradient in this area was away from the ridge and ranged between north-
<br /> northeast(15°) and southwest(210°) at magnitudes between 0.00064 and 0.0017 ft/ft. The
<br /> direction of the gradient in the eastern portion of the DP/Cogen site was generally towards the
<br /> north-northwest(300') at a magnitude of 0.00024 ft/ft(Table 2; Figure 2).
<br /> pH concentrations in all monitoring well samples were within the 6.5 to 8.5 standard pH units
<br /> range for DP/Cogen effluent (Table 2).
<br /> TDS concentrations in groundwater samples OB-1, OB-4, OB-5, OB-7, OB-8, OB-11, OB-21,
<br /> OB-24, OB-25, and OB-28 exceeded the 800 mg/L limitation for DP/Cogen effluent. The
<br /> highest TDS concentration was measured in well OB-4 (2,000 mg/L) located in the eucalyptus
<br /> grove in the northeast quadrant of the site (Figure 3). The lowest TDS concentration was
<br /> measured in monitoring well OB-17 (89 mg/L), located in the southeastern corner of the site
<br /> along the Stanislaus River.
<br /> Nitrate as nitrogen concentrations in wells OB-1, OB-5, OB-7, OB-8, OB-19, OB-26, and OB-
<br /> 28 exceeded the 10 mg/L limitation for DP/Cogen effluent. The highest nitrate concentrations
<br /> were measured in wells OB-5 (28 mg/L) and OB-28 (30 mg/L; Table 2).
<br /> 10107.04 Task 2 Lawrence&Associates
<br /> W.•I CLIENTSIDiamond Pet Foods 1010107.01-Groundwater Monitoring)Groundwater Monitoring12013 13Q2013 Ord quarter 2013.docx
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