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Report: Groundwater-quality Monitoring—October 20-21, 2005, 7500 West Eleventh Street, Tracy, CA. Page i <br /> .� Table of Contents <br /> i`.:A PROFESSIONAL CERTIFICATION AND LIMITATIONS..................................iii <br /> 1.0 INTRODUCTION.................................................................................................................... 1 <br /> F. 1.1 Site Location......................................................................................................................... 1 <br /> 1.2 Site Codes............................................................................................................................. l <br /> 1.3 Background <br /> 1.3.1 Site Characterization Studies <br /> 2 <br /> 1..3.2 Groundwater-quality Monitoring..................................................................................2 <br /> r. <br /> 1.3.3 Monitoring of LNAPL..................................................................................................3 <br /> :r <br /> ` 1.3.4 Testing of Water in Potable Water-supply Wells............... <br /> 1.3.5 Evaluation of Natural Attenuation................................................................................4 <br /> 1.4 Geology and Hydrogeology .................................................................................................4 <br /> 1.5 Distribution of Hydrocarbons in the Subsurface...................... <br /> 1.5.1 Primary Plume.................... <br /> 1.5.2 SecondaryPlume...........................................................................................................7 <br /> 1.5.3 Dispersed Petroleum Hydrocarbons in Shallow Soils...................................................8 <br /> 2.0 OCTOBER 2005 GROUNDWATER-QUALITY MONITORING ROUND..........................9 <br /> 2.1 Groundwater Elevations and Flow Direction...................... ....... <br /> f2.1.1 Groundwater Mound................................................................................................... 11 <br /> 2.2 Purging of Groundwater-quality Monitoring Wells........................................................... 11 <br /> 2.2.1 Disposal of Purge Water ................. 12 <br /> . ............................................................................ <br /> =' 2.3 Recovery of Groundwater Samples from Monitoring Wells.............................................. 12 <br /> 2.4 Analyses of Groundwater Samples .................. 12 <br /> .................................................................. <br /> 2.5 Groundwater Quality in the Near-Surface Unconfined Aquifer......................................... 13 <br /> 2.5.1 Analytes of Concern in Groundwater Along Principal Plume Axis ........................... 13 <br /> 2.5.2 Analytes of Concern in Groundwater around Fringes of Principal Plume.................. 14 <br /> 2.53 Analytes of Concern in Secondary Groundwater Plume ............................................ 14 <br /> 3.0 MONITORING OF FLOATING PRODUCT........................................................................ 15 <br /> 4.0 MONITORING OF POTABLE WATER SUPPLIES ........................................................... 16 <br /> i' 4.1 Recovery and Analysis of Samples from Potable Water Supply Wells............................. 16 <br /> 4.2 Results of Potable Water Sampling....................................................... ...... 17 <br /> ....................... <br /> 4.3 Notification to Well Owners .. 17 <br /> 5.0 CONCLUSIONS ------•-----•------•--•............................................................................................. 18 <br /> `} 6.0 RECOMMENDATIONS................... ....19 <br /> 8.0 REFERENCES...................................................................................................... .....20 <br /> TABLES <br /> Table 1: Depths to Groundwater <br /> Table 2: Results of Analyses of Samples of Groundwater <br /> Table 3: Thickness of Floating Product in Monitoring Well MW-7 <br /> Table 4: Results of Analyses of Samples from Potable Water Wells <br /> sic <br />