ARCHIVED REPORTS XR0001664 - Laserfiche WebLink

Home Browse Search

t t l f ' 15 April 1996 AGE-NC Project No 95-0109- Page 5-0109-Page 6 of 7 - concentrations verses time for momtonng wells MW-6, MW-8, MW-9, MW-10, MW-14 and EW-1 EDB was detected in-the sample from MW_714 at,a concentration of 0 52 ppb_1,2-Dichloroethane 1� was detected in samples from MW-8, MW-9, MW-13 and MW-14 at"concentrations of'I 1 ppb, 14 v ppb, 3 7 ppb and 4 5 ppb, respectively Thus is a concentration increase in four of six wells compared to the previous monrtonng results Chloroethane, tetrachloroethene and other volatile halocarbons were not detected in any of the water samples analyzed Analytical results of ground water samples are summarized on Tables 6 and 7 The laboratory report (MAI Laboratory I D Nos 61986-and 61987, 62526 through 62535) and chain-of custody forms are included in Appendix D 550. ' CONCLUSIONS AND RECOMMENDATIONS y 4 5 1 HYDROCARBON-IMPACTED GROUND WATER Ground water elevation has risen throughout the site since December 1995 (see Table 5) The change of ground water elevation is assumed to be the result of precipitation during the most recent wet season The ground water flow direction continues to be toward the south-southwest i Results of the March 1996 sampling continue to indicate that the dissolved hydrocarbons in ground water are not migrating down-gradient Analytical results from ground water samples from MW-10, MW-11, MW-12 and MW-13 continue to indicate that the hydrocarbon plume has not migrated ' beyond the known plume boundaries TPH-g,was detected in MW-7 at a concentration slightly above ; the detection limit, indicating that this well is near the current edge of the hydrocarbon plume , Hydrocarbon concentrations appear to have crested,in ,late 1993 oto early 1995 m most of the monitoring wells on the site The hydrocarbon concentrations in these wells have generally decreased since that time, with'minor fluctuations, indicating that the plume of dissolved hydrocarbons is becoming4ess concentrated " r -Results of microbiological and physicochemical analys►s,performed by an independent consultant are indicative of continued biodegradatronal activity in the ground water Concentrations of oxidized a nitrogen have improved since December 1995 However, concentrations are still below optimum for favorable microbial activity Nutrient supplementation consisting of a water-soluble solution, containing ammonium nutrate, phosphorous, and potassium was'irecommended to enhance continued microbial growth - r IWe recommend the addition of approximately 1,000 gallons of a commercially available nitrate- phosphorous- itrate- ' phosphorous-potassium (20-20-20 NPK) fertilizer to all wells (ground water and vapor) within the impacted ground water plume The nutrient addition should be performed` in stages to allow dispersion and prevent high concentrations at the inlectiori points Physicochemical and microbial data r V A 1