WORK PLANS - Laserfiche WebLink

Home Browse Search

19 November 2009 AGE-NC Project No. 02-0950 Page 12 of 13 I 520 µg/1 and 300 jig/I, respectively. • Based on plots of TPH-g, TPH-d and benzene versus time (Appendix F), a definitive trend of decreasing dissolved concentrations has been evident at the site from monitoring wells MW-2 and MW-7.Based on trend line analysis of the MW-2 and MW-7 data, AGE projects that TPH-g concentrations should be non detect at well MW-2 by October 2010 and should be non detect at well MW-7 by August 2010.Trend analysis of dissolved TPH-g,TPH-d and benzene are included in Appendix F. • The approximate maximum mass of dissolved TPH in ground water prior to corrective action was estimated at 11.41 pounds of TPH, equivalent to 1.83 gallons(Figure 12;Appendix J). However, the approximate mass of dissolved TPH remaining in ground water following corrective action is estimated to be 0.09 pounds, equivalent to 0.014 gallons. The mass and volume calculations are presented in Appendix J; the lateral extent of pre- and post- corrective action dissolved TPH is depicted in Figures 12 and 13, respectively. • A sensitive receptor survey identified fourteen (14) ground water monitoring wells within 2,000 feet of this site. No other sensitive receptors were identified. Copies of the well driller's reports are included in Appendix G; a summary of water wells located from the review of well driller's reports is included in Table 7 and a location of wells are depicted on Figure 9. • A soil-vapor intrusion investigation has not been performed at the site. However, shallow impacted soil has been removed by excavation activities. • AGE concludes that petroleum hydrocarbons remaining beneath the site appear to pose minimal risk to human health and beneficial use of ground water down-gradient from the site. 8.0. RECOMMENDATIONS Based upon data collected from the site, AGE recommends the following: • No further subsurface investigation at this time. The Masonite site has adequately assessed petroleum-impacted soil and ground water associated with the UAR. • Consideration of the facility for closure as a low risk ground water site. From previous data, AGE has documented that petroleum hydrocarbon concentrations in ground water at the site have been at non-detectable or near non-detectable levels. • Destruction of monitoring wells in accordance with applicable regulations as part of the site closure preparations. I Advanced GeoEnvironmental,Inc.