Source Zone Delineation Demonstration Report - Triad Resource ...

For the conventional investigation, it is assumed that soil samples are analyzed by an off-site analyticallaboratory for the full suite of VOC analytes according to USEPA SW846 Method 8260. This is incontrast to the adaptive investigations that employ an on-site laboratory using DSITMS to analyze the soilsamples for an abbreviated analyte list (TCE, PCE, DCE, and vinyl chloride) according to USEPASW846 Method 8265. The costs associated with project planning, data evaluation and reporting, and thepreparation of a RI report are assumed identical for both the HAS and DPT investigations.6.1.1 Hollow Stem Auger (HSA)The total estimated cost of a hypothetical HSA investigation is $215,250 (see Table 6-1) representing thehighest cost of the four hypothetical investigations considered as part of this analysis. By comparison, theestimated costs associated with the other investigative methods are $193,460 ($21,790,or 10% less) forDPT, $149,620 ($65,630, or 30% less) for WS/DSITMS; and $125,100 ($90,150, or 42% less) forSVE/DSITMS.Two primary reasons account for the elevated cost associated with the HSA investigation: (1) directdrilling costs and (3) the investigative-derived waste (IDW) disposal charges. Direct drilling costsinclude the expense of mobilization and demobilization, actual drilling costs, the cost to decontaminateequipment during and after drilling operations, and borehole abandonment. The total direct drilling costsfor both phases of the HSA investigation are $37,160. This is compared to $28,120 in direct drilling forthe DPT investigation, a difference of $9,040 or 24% less (decontamination is not shown as a separateline item but is included in the hourly equipment and field crew rate for the DPT investigation). The costof IDW disposal for the HSA investigation is $11,880 and is estimated assuming an 8.25-inch auger and40 feet of contaminated soil (upper 20 feet of vadose zone is assumed uncontaminated) in each of 23borings. If a 6-inch auger is used, the IDW disposal cost is reduced by approximately $5,500. In eithercase, IDW disposal cost is considerably more than the estimate $1,100 incurred during the DPTinvestigation. The difference in the IDW disposal cost is due to the larger diameter boring andsubsequent increase in the volume of contaminated waste generated with the HSA investigation.Although the HSA investigation is estimated to be the most expensive, it does have some advantages overother investigative techniques. One advantage associated with HSA is the ability to construct a well in aboring following soil sampling. The decision to construct a well may be based on field observations, ormay part included in the original investigation plan. With any of the other investigative techniquesconsidered as part of this cost analysis, the decision to construct a well would incur additional drillingcosts. In addition, HSA is more robust than DPT in terms of penetration into the vadose zone. AlthoughHSA may encounter difficulty penetrating gravels and cobbles, it is likely to be more successful in thesesoils than DPT. Finally, HSA allows for the continuous logging of soil cores during a soil samplinginvestigation whereas continuous logging cannot adequately be performed using WS/DSITMS.March 2003 6-5 OU 12 Demonstration ReportFinal