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f <br /> PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> JOGI KHANNA M.D.,M.P.H. <br /> Health Officer <br /> CrgCrFOR�� <br /> P.O. Box 2009 0 (1601 East Hazelton Avenue) • Stockton,California 95201 <br /> (209) 468-3400 <br /> � 1 r~- <br /> JOHN JOHNSON / ,� <br /> THE CUSTOMER COMPANY <br /> P O BOX 886 `' FEB 2 419913 <br /> BENECIA CA 94510 <br /> RE: FOOD AND LIQUOR SITE CODE 1984 <br /> 890 NORTH MAIN <br /> MANTECA CA <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has recently <br /> completed a comprehensive review of the past activities at the above noted site and has the following <br /> comments. <br /> The levels of contaminants documented in the soil samples obtained after the 1987 over-excavation are <br /> considered to be too high to be left in place without the risk of impacting the groundwater at the site. <br /> The three initial monitoring wells drilled at the site in 1987 showed contamination in the groundwater, <br /> which was approximately 13 feet below ground surface at that time. <br /> As the water table level has receded during these recent drought years, the hydrocarbons originally <br /> detected in the groundwater at this site have most likely become adsorbed to the soil. Should the water <br /> table rise, it may again become impacted by the hydrocarbons previously left behind in the soil. <br /> Therefore, the two main areas in the soil that are a concern with respect to future risk to groundwater are <br /> those areas of soil contamination that were not investigated after the 1987 over-excavation activities and <br /> the secondary soil contaminant plume left behind by the recent drop in the water table. <br /> Soil borings drilled in the areas of concern may give an indication as to the areal extent of the residual soil <br /> contamination. Should these areas still show residual contamination, some form of remediation (either <br /> passive or active) must take place before this site can be considered for closure. <br /> Should the soil borings not detect any residual soil contamination, some degree of groundwater monitoring <br /> may still be warranted, depending on the extent of the confirmation work completed and the degree of <br /> confidence that is obtained from the work (i.e. the locations and number of soil borings, the number of <br /> soil samples submitted to the laboratory for analysis, the methods used to obtain, store and transport the <br /> samples, the laboratory detection limits and quality control data, etc.). <br /> As current data indicates, the groundwater does not appear to be impacted at this time. However,because <br /> the full extent and concentration of residual soil contamination is unknown, the risk to groundwater at this <br /> site is still an issue, as noted above. Groundwater sampling of the wells on the site has been requested by <br /> PHS/EHD in the past in order to monitor and verify that the groundwater does not become impacted <br /> again should site conditions change. In addition, the previously requested quarterly status reports are a <br /> minimum compliance requirement pursuant to the California Code of Regulations, Chapter 16, Section <br /> 2562(d). <br /> A Division of Sun Joaquin County Health(are Services 10 <br />