Laserfiche WebLink
10 May 1996 - <br /> AGE-NC Project No 95-0121' J <br /> r - <br /> t <br /> Page > <br />' approximately 0 0023, or 12 feet per mile (Figure 3 - Surface Ground Water Elevation Contour <br /> Map) <br /> 1 � , <br /> 42 LABORATORY RESULTS OF GROUND WATER SAMPLES _ <br />' TPH-g was detected in water samples from MW-1 through MW-4, MW-6, and MW-7 at _"I <br /> concentrations up to 36,000 ppb (parts per billion reported as micrograms per liter), TPH-d was <br /> detected in samples from MW-1 through MW-9 at concentrations up to 13,000 ppb t <br /> 1 ' <br /> Benzene was detected in samples from MW-1 through MW-4, MW-6, and MW-7 at concentrations <br />' up to 5,700 ppb Toluene was' detected in samples from MW-1 through MW-3, and MW-6 at <br /> concentrations up to 2,200 ppb Ethylbenzene and total xylenes were detected in water samples from <br /> MW-1 through'MW-4, and MW-6 at concentrations up to 420 and 2,000 ppb, respectively The <br />' analytical results of the samples are listed in Table 2 The laboratory report and chain-of-custody are <br /> included in Appendix B <br /> 5.0. CONCLUSIONS & RECOMMENDATIONS <br />' Ground water flow direction has remained relatively constant at the site over the past two years , <br /> Monitoring well MW-9 continues to be up gradient of the former UST area, while monitoring wells <br /> MW-8 and`MW-5 continue to be down gradient <br />' <br /> During Febris 1996 TPA- concentrations from wells MW-1 and MW-7 increased substantially, s <br /> _ g �y g , <br /> TPH-d concentrations increased in all monitoring wells except MW-2 However, BTE&X <br />' concentrations increased only in MW-1 The increase in total petroleum hydrocarbons concentrations <br /> ma'y be related to the rise of ground water, causing washing of impacted soil wrthrn`the capillary <br /> fringe or lower vadose zone t <br /> Furthermore, surface ground water was approximately between'l to 10 feet above the top of screen <br /> intervals from monitoring wells MW-1-through MW-8, while approximately 1 foot below the top of <br />' the screen interval from monitoring well MW-9 Because the screened intervals from MW-1 through ' , <br /> t MW-8 are beneath surface ground water, analytical results may not be representative of petroleum r <br /> hydrocarbon concentrations' <br /> MTBE should be sampled for a minimum of two consecutive quarters If laboratory analysis indicates <br />' non-detect for both quarters, then we recommend eliminating MTBE from the sampling program <br /> Further assessment is required northeast of MW,4 to determine the extent of dissolved hydrocarbons <br /> in ground water and to'monitor possible migration of,the plume as a result of ground water <br />