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' GW&SW Monitoring Report COE-WDR Project No. 894.2 September 1,2011 rate of recharge that may have contributed to the well having historically gone dry from past monitoring events corroborates the above interpretation. • The concentrations of the constituents of concern observed this quarter are within the historical ranges observed at the site. ' • The background monitoring wells appear to show water chemistry similar to the other monitoring wells on site. be below laboratory reporting limits for all • Total Coliform Bacteria — was reported to ' monitoring wells with the exception of MW-3 (542 MPN/100mL). Total Coliform has decreased or remained the same from the previous monitoring event in all other wells and is within historical ranges. • Fecal Coliform Bacteria was reported to be below laboratory reporting limits for all monitoring wells during the 3rd quarter 2011 groundwater monitoring event. Coliform is ubiquitous in the environment and has been detected intermittently in various monitoring ' wells at the site. re reported to be non-detect in all monitoring • Volatile Organic Compounds (VOCs) we t wells during the 3rd quarter 2011 groundwater monitoring event. • No discernible trends are observed in the analytical data from the monitoring wells, i.e. none of wells show steadily increasing or decreasing concentrations. The concentrations ' of the various constituents appear to fluctuate seasonally. • Historically, the water chemistry in the Stanislaus River does not change appreciably between sampling stations R-1 and R-2. However, for the 3rd quarter groundwater ' monitoring event sampling point R-1 contained elevated levels of total coliform (2,320 MPN/100mL). It is believed that this is a localized phenomenon that occurred upstream of the facility. Sampling point R-2 was elevated but it is believed that the higher total ' coliform values are a result of upstream conditions. Laboratory analytical results from sampling points R-1 and R-2 are within historical range for fecal coliform. Recommendations • GTI recommends that the quarterly groundwater and surface water monitoring program continue according to the "Rs (order No. 5-00-1142 and the corresponding ' Monitoring and Reporting Program No. 5-00-142). ' 6.0 LIMITATIONS ' This report was prepared in accordance with the generally accepted standard of care and practice in effect at the time Services were rendered. It should be recognized that definition and evaluation of environmental conditions is an inexact science and that the state or practice of environmental geology/hydrology is changing and evolving and that standards existing at the present time may change as knowledge increases and the state of the practice continues to improve. Further, that differing subsurface soil characteristics can be experienced within a ' small distance and therefore cannot be known in an absolute sense. All conclusions and recommendations are based on the available data and information. ' Geological TecWcs 19C. 8 894 3rd QMR I l.doc