Laserfiche WebLink
Metadata
Document management portal powered by Laserfiche WebLink 9 © 1998-2015 Laserfiche. All rights reserved.
Ms Lori Duncan <br /> April 4, 2000 <br /> . Page 5 of 5 <br /> samples collected at 15 feet and 20 feet from boring SB6 <br /> • TPHg, TPHd, BTEX and VOCs detected in the groundwater ranged from at or near non-detectable <br /> to moderate levels in borings SB4 through SB8 TRPH and oxygenate additives were at not <br /> detected <br /> • Lead detected in the soil appears to be representative of background levels at the site Groundwater <br /> results appear to be suspect. Groundwater from borings with higher levels of organic contamination <br /> (primarily TRPH and TPHg) have lower concentrations of lead, and borings with lower levels of <br /> organic contarnmation have higher levels of lead The opposite should be true <br /> Conclusions <br /> • Soil in the immediate vicinity of the former UST has been significantly impacted by petroleum <br /> hydrocarbons,solvent related VOCs, and lead <br /> • The vertical extent of soil contamination has been defined No contaminants were detected below <br /> 31 feet bgs <br /> • The lateral extent of soil contamination has been defined to the north, south and east, and appears to <br /> be limited to the west. Impacted soil at the site appears to extend no more than 20 feet north, 20 feet <br /> west,or 10 feet southwest of the former UST location <br /> • Significant impact to shallow groundwater has occurred, however, contaminant concentrations <br /> appear to diminish appreciably within relatively close proximity to the former UST <br /> • The extent of groundwater contamination has not been completely defined However, analytical <br /> results infer that the contaminant plume is localized, and is essentially bounded to the north by <br /> borings SB7 and SB8 approximately 35 feet north of the former UST <br /> • Based upon San Joaquin County groundwater flow maps and recent analytical data it appears that <br /> groundwater flow at the site is generally in a northeasterly direction However, capillary zone soil <br /> contamination present in only borings SBI and SB6 suggests a northerly flow <br /> RECOMMENDATIONS <br /> Based upon field and analytical data collected during this investigation, Ground Zero recommends the <br /> following <br /> I Install four groundwater monitoring wells in the vicinity of the former UST excavation for <br /> the purpose of collecting confirmation groundwater samples and determine the local <br /> groundwater gradient and flow direction Due to limited access inside the buildings, the <br /> wells would necessarily be installed with a limited access rig or using small diameter <br /> monitoring wells installed with a direct push drilling rig Figure 5 presents suggested <br /> locations of proposed groundwater monitoring wells <br /> groundzelgabbardladd_bonng_rpt doc <br />