ARCHIVED REPORTS_2007_18 - Laserfiche WebLink

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1.0 Surface Water Monitoring Surface water samples at the Austin Road Landfill were collected by ATC Associates, Inc. during the second quarter 2007 monitoring event from Littlejohns Creek at the upstream monitoring point (ASW-1) and downstream monitoring point (ASW-2). Surface water samples are scheduled to be analyzed quarterly for field parameters (pH, specific conductance, temperature, and turbidity) and monitoring parameters (bicarbonate, calcium, carbonate, chemical oxygen demand [COD], chloride, magnesium, nitrate, oil and grease, potassium, sodium, sulfate, total dissolved solids [TDS], total organic carbon [TOC], and volatile organic carbons [VOCs]) when surface water is present. The field and laboratory results provided by BC Laboratories, Inc. for the second quarter 2007 surface water monitoring event are summarized on Table 2.1. The historical surface water data are presented in Appendix A. The data are graphed on time series concentration plots, included in Appendix B. The concentration limits were calculated by Herst& Associates, Inc. using data collected through the second quarter 2007 monitoring event. Information on the development of the concentration limits can be found in the Fourth Quarter/Annual 1999 Monitoring Report, Austin Road Landfill, prepared by CH2M Hill in January 2000. The description of the statistical methods is reproduced in Appendix C. The statistical analysis calculations for surface water monitoring points are included in Appendix B. During the second quarter 2007 monitoring event, there were no constituents that exceeded their concentration limits at downstream surface water monitoring point ASW-2. Table 2.1 presents the VOC detections at surface water monitoring points during the second quarter 2007 monitoring event. Carbon disulfide was detected at upstream surface water monitoring point ASW-1 (1.5 ug/L). There were no VOCs detected at downstream surface water monitoring point ASW-2. The carbon disulfide detection at ASW-1 during the second quarter 2007 is the first detection of this constituent at surface water monitoring points. Historical data from the surface water monitoring points were evaluated for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses for surface water monitoring points are included in Appendix B. Only field pH at ASW-2 exhibited a statistically significant upward trend. The second quarter 2007 field pH value observed at ASW-2 (7.90 s.u.) is comparable to values observed at that monitoring point since January 2002, and is within the National Secondary Drinking Water Standard range of 6.5 — 8.5 s.u. Sen's Slope analysis identified decreasing trends in nitrate at ASW-2, field specific conductance at ASW-1, total dissolved solids at ASW-1 and ASW-2, and total organic carbon at ASW-1 and ASW-2. Site personnel report that soil cover has been placed over the waste material to prevent ponding of stormwater and to protect surface water. In addition, down drains and a perimeter ditch direct stormwater to a basin in the southwest corner of the site. Inspection and maintenance procedures for these stormwater control structures are provided in the site's Stormwater Pollution Prevention Plan,prepared by CH2M Hill and revised June 1997. 2.0 Groundwater Monitoring Groundwater samples were collected by ATC Associates, Inc. during the second quarter 2007 monitoring event from the detection monitoring and corrective action wells at the site. Monitoring well AMW-2, which is upgradient from the landfill, is the designated background well. Monitoring wells AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14 are currently 1