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Diamond Pet Food&Ripon Energy July 23,2018
<br /> Second-Quarter 2018 Groundwater-Monitoring Report Page I of S
<br /> INTRODUCTION
<br /> This report presents the results of second-quarter 2018 groundwater monitoring performed by
<br /> Lawrence &Associates (L&A) on April 2 and 3, 2018, at Diamond Pet Food Processors of
<br /> Ripon California, LLC (DP) and A1taGas Ripon Energy, Inc. (Ripon Energy), 942 and 944
<br /> South Stockton Avenue, Ripon, California (Figure 1). The work was performed in accordance
<br /> with Waste Discharge Requirements (WDR) Order No. R5-2012-0105 for the DP/Ripon Energy
<br /> site, adopted by the California Regional Water Quality Control Board, Central Valley Region
<br /> (CVRWQCB) on October 4, 2012.
<br /> Second-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/Ripon Energy site. All offsite monitoring, domestic,
<br /> and municipal wells were sampled by Stantec for the City of Ripon or ECM Consultants for
<br /> Nestles. Field and laboratory results provided by Stantec and ECM Consultants were used in
<br /> the preparation of this report and are presented in Attachment A. L&A, however, did not
<br /> review the Stantec or ECM Consultants sampling methods or data for accuracy.
<br /> SECOND-QUARTER 2018 GROUNDWATER MONITORING
<br /> FINDINGS
<br /> On April 2, 2018, the direction of the groundwater gradient across most of the DP/Ripon Energy
<br /> site was northwest and ranged between 263°to 291° at a magnitudes between 0.00028 and
<br /> 0.00054 ft/ft. In the southwestern quadrant of the site the direction of the gradient was 221°
<br /> southwest at a magnitude of 0.00063 ft/ft. (Table 2; Figure 2).
<br /> The pH concentrations in all monitoring wells were within the 6.5 to 8.5 standard pH units
<br /> range for DP/Ripon Energy effluent(Table 2).
<br /> TDS concentrations in groundwater samples OB-1, OB-4, OB-11, OB-24, OB-25, and OB-28
<br /> exceeded the 800 mg/L limitation for DP/Ripon Energy effluent. The highest TDS
<br /> concentrations were measured in wells OB-4 and OB-25 (1,500 mg/L, respectively) located in
<br /> the eucalyptus grove in the northeast quadrant of the site and in the southwestern quarter of the
<br /> site (Figure 3). The lowest TDS concentration was measured in monitoring well OB-22 (100
<br /> mg/L), located in the south central portion of the site between ASB-2 and the Stanislaus River.
<br /> Nitrate as nitrogen concentrations in wells OB-1, OB-26, and OB-28 exceeded the 10 mg/L
<br /> limitation for DP/Ripon Energy effluent. The highest nitrate concentration was measured in
<br /> well OB-28 (56 mg/L; Table 2)just offsite of the northeastern quadrant of the site.
<br /> CONCLUSIONS
<br /> The past disposal of plant process water by the former paper-making facility was responsible for
<br /> some of the elevated TDS levels measured in the semiperched aquifer over most of the site.
<br /> Since the facility's conversion to a pet food manufacturing facility, however,plant effluent has
<br /> 10107.10 Task 2 Lawrence&Associates
<br /> W.•ICLIENTYDiamond Pet Foods 1010107.01-Groundwater Monitoring)Groundwater MonitoringQ01812Q2018QQ quarter 2018 report.docx
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