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OctobeT2002 • LUSTLine Bidlefin42 spohn t"Hach # 907-00 or equivalent). anywhere in the United States, it is ical method for fuel oxygenates (and In the field,each vial is filled with the also important to respond promptly other contaminants of concern)when groundwater sample and sealed to any petroleum release.The sooner the analyses will be used to(1)char- without headspace (the same as is all of the contaminants in a plume are acterize the three-dimensional extent done if the sample is preserved with identified and their subsurface extent of a contaminant plume, (2) deter- acid). determined, the sooner a remedy can mine whether a site requires active The salt is added to excess. If a be selected and implemented. remediation, (3)select an active rem- portion of the salt is washed out of Because a contaminant plume is edy, (4) design an active remedy, (5) the vial as the vial is filled with sam- smaller and more easily managed determine whether a site has met ple, enough TSP will remain to pre- early on,the magnitude of the impact site-specific cleanup objectives, or(6) serve the sample. As the salt and the overall cost of the cleanup determine if it is no longer necessary dissolves, it buffers the sample to a should be less than if the plume is to continue monitoring a site. pH greater than 11. allowed to expand. After all of the oxygenates (and No special handling of the sam- other contaminants of concern)pre- ples is required prior to analysis, The protocol described in this artiC sent at a site have been identified and although they should be stored in a their concentration and extent deter- refrigerator at 4° C. Water samples enables us to determine the mined,future analyses might then be preserved with TSP are 1 percent presence and concentration of all o conducted using a less expensive salt by weight. If purge-and-trap the common oxygenates and BTEX 8 determinative method (e.g., 8015). (Method 5030)is used to prepare the Situations that might not require con- water samples, it is particularly levels of regulatory interest. Rout firmatory analysis would include important to prevent the transfer of use of this protocol will greatly routine long-term performance moni- aerosols from the purged water to the improve the quality of the data tha toring as part of a MNA remedy or trap and GC column.This should be are Sported, which in turn will exposure management strategy. no different than current good labo- To properly implement this pro- ratory practice. enable us to make better decision tocol, groundwater samples should It is prudent to check the pH of which will ultimately result in mar, be collected from locations where the sample with indicator paper to effective utilization ofawl' oxygenates are most likely to occur, ensure that the pH is greater than 11 based on their chemical and physical prior to introducing it into the purge esou behavior. Because oxygenates are vessel or the headspace sampler for more soluble than petroleum hydro- analysis.IE it is necessary to analyze Consequently, it is prudent to carbons and can be more recalcitrant, samples that have already been pre- analyze samples for the entire suite of oxygenate plumes may be longer served with acid, the acid can be than typical BTEX plumes. oxygenates as identified in this proto- destroyed with TSP prior to analysis. Oxygenate plumes may also An amount of TSP sufficient to raise TAEcol (i.e., MTBE,TAME, ETRE, mIPE, "dive" beneath conventional moni- the pH of the sample to greater than should be TAA, and TBA). Samples toring wells and migrate undetected 11 is added to the sample vial, which shoulprepared for analysis, until a drinking water source is preferably using EPA Method 5030 is quickly resealed without head- heated to 80impacted. (See Weaver and Wilson's ° C (although either space and shaken gently to dissolve article in LUSTLine #36.) To ensure used if the lab the salt. Generally,about 0.7 gram of Method 5021 aMethod 5032 maybe that such plumes aren't migrating TSP is sufficient for a 40 mL VOA laboratory can demon- undetected, samples should be col- vial,but sometimes(depending upon strate appropriate performance with lected from a series of discrete sam- these methods). the of the sample) more must be The determinative method (e.g., opoints that draw in addeded groundwater to elevate the pH to greater Method 8260, 8015, or other appro- groundwater only over short vertical than 11. priate method)should be calibrated intervals.There should a sufficient for the entire suite of oxygenates,and number of sampling points cover Recommended Protocol these analytes should be reported for the entire vertical distancece over The protocol described in this article every sample analyzed. With the which an oxygenate plume may enables us to determine the presence understanding that ethanol and migrate. Generally this means that and concentration of all of the com- methanol are potentially present at additional sampling points are mon oxygenates and BTEX at levels fuel release sites, it is also advisable required at progressively greater of regulatory interest.Routine use of to have samples analyzed for these depths below the water table as the o distance from the this protocol will greatlyurove the alcohol oxygenates usingappropriate source increases. Increasing the quality of the data that are reported, preparative and determinative meth- length of monitoring well screens is which in turn will enable us to make ods. not appropriate as this will only better decisions, which will ulti- EPA Method 8260 (or another dilute the concentration of contami- mately result in more effective uti- method that provides confirmatory nants in the sample and mask the lization of available resources. identification of all of the fuel oxy- true concentration in the plume. Because MTBE (and potentially genates and can be demonstrated to To prevent constituents in the any other oxygenate)may be present meet project data quality objectives) samples from being biodegraded at any petroleum UST site, whether is the preferred determinative analyt- the release is new or old, virtually ■continued on page 8 7