Laserfiche WebLink
Metadata
Document management portal powered by Laserfiche WebLink 9 © 1998-2015 Laserfiche. All rights reserved.
GeologicalTec&yksbu. Page 8 <br /> Groundwater Monitoring Report <br /> Project No.750.2 <br /> November 10,2004 <br /> Groundwater Parameters <br /> • pH measurements collected from the water table wells range between 6.97 and 7.17 and <br /> are conducive to biodegradation activity. <br /> • EC measurements in the water table wells range from 508 (Dmhos/cm to 690(Dmhos/cm. <br /> • Oxidation-reduction potential (ORP) measurements were positive in all water table <br /> monitoring wells and ranged between 48 mV and 92 mV. <br /> • All water table monitoring wells at the site has Dissolved Oxygen (DO) levels greater <br /> than 2.4 ppm. DO measurements above 2.0 ppm indicate conditions are conducive to <br /> aerobic biodegradation activity. <br /> • Field parameters recorded in the deep well MW-101 are consistent with data from the <br /> water table wells. <br /> Table 4 summarizes the groundwater parameters measured at the site. <br /> 4.0 FINDINGS & RECOMMENDATIONS <br /> r <br /> Findings <br /> The results of the groundwater sample analyses show the following: <br /> • All groundwater-monitoring wells were non-detect above laboratory reporting limits for <br /> all analyzed constituents. <br /> • Chart 1 illustrates the gradual decrease in groundwater elevation over time and the <br /> — exponential decrease in TPH-G concentrations in MW-1. <br /> • Vertical groundwater gradient was calculated for the event of August 12, 2004, and was <br /> found to be insignificant. <br /> o The magnitude of the vertical gradient has been getting progressively smaller during <br /> the last several monitoring events. <br /> o Thirteen of the past sixteen monitoring events show a downward trend to groundwater <br /> flow. <br /> o The downward vertical gradients are typically equal toc or less than the horizontal <br /> groundwater gradients. <br /> • Oxidation-Reduction Potential measurements (Table 4) are positive for all the wells. <br /> This suggests that the volume of contaminants leaching into groundwater has been <br /> stopped and that biodegradation of the contaminants is at a rate sufficient to mitigate the <br /> residual BTEX/TPH-G plume in the area around the source without depleting the oxygen. <br /> • The dissolved oxygen measured at the site is between 2.4 and 5.0 ppm and is conducive <br /> to natural attenuation of BTEX/TPH-G. <br /> • It appears that soil contamination has been reduced significantly by the vapor extraction <br /> process that oxygen has been added to the subsurface and no groundwater contamination <br /> is present in the monitoring wells. <br /> • Excellent progress has been made at this site. Clean-up goals are being met and the effort <br /> has exceeded MCL's for the known constituents at the site. <br />