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EM 1110-14444 3Jun 02 are commonly encountered m m°nitonn cdei e sanw th ve ting time,and b Several data trends 2-3c(6)) heavier soil gas,and vent gas Residual soil contamination(paragrapha large n effects are apparent from preferential evaporation of more volatile compounds leaving distillation tracking residual contamination accurately requires analyzing compounds behind However, unmixed medium,is heterogeneous Analysis of residual number of samples because soil,being (Analyses of residual contamination is usually limited to before venting, enth atm determine tte'�via to been mete concentrations, and after the that venting operation is complete,to confirm aqueous plus vapor phase contamination in soil samples are actually analyses of the residual plus aq contaminants) armnated aurid at sites th erlying shutdown should not be considered in isolationuld also beimomtdosed to terrnme the c SVE s � water Concentrations of contaminants in ground to the soil gas A site contaminateedte with no the contribution of contaminants from the aqueous p Dal of 1 mg/kg � 55 mg/kg of PCE m soil was subjected to SVE to achieve a cleanup g as concentrations met as was less that 1 percent of Its initial value Soil g It was found PCE concentration in vent g shutdown criteria,but soil sample analyses showed PCE concentrations of uptable to 15 rn g recontaminating the soil by capillary action and aeteelerated the Mass fluctuations transfer fluid that groundwater was u into the movement during a period when the water table rose and fell evidently�'apparently transportedP process from the saturated zone to the unsaturated zone Solutgas In the e was lOwIn during a water table rise,and then exposed to soiUnder stagnantwatertablelconditiions,by op in vadose zoned g the water table and draining of sol}near the capillary fringe rough calculation showed that mass transfer' would tend to be diffusion limit oaand therefore four orders a VE contrast,the a period of bulk fluid movement magnitude slower than during p 12VOC, could have coat we ntributed 270 kg of the more his 325 s ng tg1i��ul�Pha�flow model,re removed y t ons groundwaterextensive simulations Ammunitions system(Urban 1992) By performing phenomenon at the Twin Cities Army Williams et al (2()00)have demonstrated a similar p Plant(TCAAP) progress of SVE/BV a gauge of mass removal from the whole soilv°lhase d Air,being a mixed medium,is more economic al than soil far monitoring the progrp operations Vent gas concentrations can provide as monitanng can resolve spatial variationvapor affected by the SVEfSV system,while soil g or hale compounds,including both VOCs and Oz,COz contaminant concentrations Monitoring of gr p and methane m monitoring points will assist greatly m calibrytibnegme s models tracer gas concentration at confidence as into e specified point This permits estimation of flow velocities in the results of�afte de je modeling Another f he parameter whic may e rates across the site(USEPA, monitoring p ore volume exchang to assist in calibration of models and estimation of p 1996) d with BV is at times ered fuels cOntainIng mployed for treatment of soilshcations,nso�t c n enirat Dens have been observed to e drocarbons In such app relatively heavy petroleum by degradation rates decline slowly over time Concurrent shutdown decline moderately fast at first,then the dept en uptake rates declined over time,signaling that most of testing performed periodically indicated that oxygen approach to viewing such data the more biodegradable constituents tidtuents are been nso tow in solubied A lity and volatility that they re no Io longer might argue that if the remainingwn to appropriate bioavailable under operating conditions ct exp sure routes can beiprevented through present a nsk,provided that direct con P administrative or containment measures(Smith et al 1995) 9-4