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MAR-24-98 16 45 from MODWARD CLYDE 4 T-735 P 18/34 1qb-462 612911 There was no appreciable difference in the TPH ccentrations between ft pro-purge samples collected by the K►®IS SamplerTm and pont-purge samples collected by the checkvaive bailer 0 The test showed overall lower TPH concentrations in the post-purge K+SIS SamplerTm samples when compared to the post-purge check-valve bailer samples, due to an improperly designad field method (i.o , the KAKIS Sarnpior was delivered to a depth of 4 feet BGW, while the bailer sampled the upper 9'h feet of the water column ) Compainson of relative recovery values indicated as much as a 540% Increase in recoverable dissolved chemicals of concern (COGS) in the pre-purge KAKIS Sampler,", Samples as compared to the post-purge check-valve bailer samples Comparison of overall costs showed a considerable difference between the two methods employed at the site. Savings of more than 80% were shown when using the KAKIS SamplerTm in a no-purge methodology sc©nario The %VSPA GMy -- to 1996, under pressure to reduce the ever-increasing costs of onvironmontal cleanup at Petroleum contaminated sites, the Wastom States Petroleum Association sponsored the "Galifomia Well Purging study° to evaluato tho no©d for purging of groundwator monitonng walls pnor to sampling it should be noted that several methods of purging (high-flow, low-flow, and passive) were compared in this study, as were several types of passnre and rsotrvo campling dovicos. Analysis of tho collected data set supports the following three conclusions The results of analyzing the entire data sat indicate that there is a systematic tendency toward slightly higher petroleum hydrocarbon concentrations in the no-purge sample than in the post-purge sample with the modlan value of the relative percent difference between no-purge and post- purge samples being approximately 9 5 percent The degree of variability introduced into the sampling process by the absence of purging is no larger than, and in many cases much smaller than. the variability introduced by the choice of a purging method In simpler terms, the decision to select a no-purge sampling methodology will not effect the overall variability in chemical data, and will provide a comparable, and in many cases more conservative, estimate of petroleum hydrocarbon concentrations in groundwater In a small population of wells/sites, an especially large discrepancy between no-purge and post- purge concentrations was found This effect appears to be due to site-specific conditions/mechanisms, is reproducible, and such wells/sites can be identified using the sampling methodologies presented in their Study. Tho Man4ord Steady -- Under directive from the Department of Energy Operable unit Manager to investigate methodologies which could obtain supenor data 2nd cut costs,the ilio-purge KAKIS SamplerTm technique was tested against the Low flow Purge technique at the Hanford Operable Unit in Richland Washington In an unprecedented cooperative effort, a multi-agency, mufti-contractor study was conducted in 9996 on a limited number of wells to evaluate the benefits and inherent drawbacks associated with each sampling method and device In this unpublished study, M Darrach, et al , noted that, " .the KAKIS Sampierr1' provides superior sampling results where large sample volumes are not required.," and that, using the KAKIS sample(m. purging appears unnecessary in wells which exhibit a measurable flow through the screened interval Aquifer flow evaluation was conducted on each well selected for this study using colloidal tracer methodology Hall at al, has shown that flow through the screened portion, and at any interval along the screened portion, of any groundwater monitoring well can ba aff®ctively identified and characterized using colloidal tracer methodology The results of now tracer testing at the Hanford Operable Unit on the wells selected for this study indicated that Rows as low as 1-2 gpd were sufficient to affect refreshing of the water inside the screened portion of the well ®tat:r W LAulthfi YOF Sampling MudW -- Some success has been achieved using a new discrete mufti-layer sampling (DMLS) system in the no-purge scenario. The DMLS system resembles an elongate "bird house" with numerous chambers, each filled with de-ionized water, extending radially outward from a central stem, each chamber is covered with a serni-permeable membrane which is exposed to the water within the well The DMLS system is lowered down a well and allowed to reside within the well for up to several months before it is retrieved and 4 of 10 3/24199 4 22 PM