ARCHIVED REPORTS_XR0006336 - Laserfiche WebLink

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1" 1.0 INTRODUCTION Upgradient Environmental Consultants was retained by Mrs Marjorie Conrady in March, 1998 to provide site remediation and groundwater monitoring services at her property located at 1002 Yosemite Street in Stockton, California The property is the former location of a gasoline service station that was demolished about 1980, when the underground fuel storage tanks were removed Upgradient submitted a Corrective Action Plan in April, 1998, which was approved by Michael Infuma of the Environmental Health Division of San Joaquin County Public Health Services (PHS/EHD) in mid-April, and the corrective action was performed in late April The purpose of this report is to present the results of monitoring activities since May The investigation is currently managed for Mrs Conrady by Mr James Dyke of Neumiller& Beardslee, Attorneys at Law 2.0 BACKGROUND The property is located on the northeast corner of Acacia and Yosemite streets in a predominantly residential area of west Stockton (Figure 1) The site is now vacant, but was operated as a gasoline service station from 1961 to 1978 The fuel storage tanks and dispenser islands were removed in 1980, and observers noted evidence of an unauthorized release of gasoline Investigation of the extent of contamination began in 1990, and was completed in 1997 Site remediation was begun in April 1998, when seven borings were drilled and a slurry of Oxygen Releasing Compound (ORC) was injected into each boring to provide oxygen to enhance natural bioremediation of the hydrocarbons Since that time, groundwater has been monitored on a regular basis to track changes in dissolved oxygen and hydrocarbon concentrations 3.0 MONITORING PROCEDURES AND RESULTS 3.1 Depth to Groundwater The depth to groundwater in each well was measured on June 10 and again on July 6, and the depths were recorded on the Well Monitor Report(Appendix A) Depths were measured with a Solinst water level sounder to an accuracy of 0 01 foot Water level and casing elevation data are tabulated in Table 1 and were used in constructing groundwater gradient maps for both days (Figures 2 and 3) The maps are similar in appearance and to those for the months of April and May, and all of the maps indicate that the water table has a natural slope to the northeast and a trough along the west (street) side of the site In June, the gradient was approximately 0 003 ft/ft, down from 0 008 ft/ft in May In July, the gradient increased again, to 0 006 ft/ft and a slight mound appeared in the vicinity of VW-2 2