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MAR-24-99 16 50 From WOODWARD CLYDE T-735 P 28/34 Job-402 1l1S4tC�C t ujx4-"ILC4 VU settled flocculants and soil particles, providing the least turbid sample available 17Cio einem of DPOS Scuip ing A bullet-listing of sums of the bonefds of DPIS sampling Is presented below This list is summamed from the available literature Discrete point-interval monitoring of ground-water quality is cost-effective relative to nested or clustered wells (23). Discrete point-interval groundwater sampling provides greater precision in evaluating the vertical distribution and range of contiaminant concentrations relative to vertically-Integrated samples obtained from wells which partially- orfully-penetrate a givan aquifer (92: 13) Groundwater quality data derived from discrete point-Interval samplers (DPIS) provide a sound basis to delineate oxidatlontraduction (REDOX) boundenes and to evaluate chemiaml and microbial processes in an aquifer (22) Discrete point-interval monitoring of forced-gradient tracer tests enables development of a three-dimensional picture of hydraulic conductivity (9) Discrete point-interval monitoring provides an accurate determination of the three-dimensional distribution of piezometnc head within an aquifer (42) The first three findings are particularly Important In view of the sheer number of heaardous waste sites ander regulatory supervision in the United States, particularly underground storage tank (UST) sites 7hG M003 ftmp0ov sm (DPOS) The sampler used in the new DPIS protocol is a unique new groundwater device designed to eliminate sample turbidity, organic constituent volatilization, and costly well purging (5) It is particularly effective on volatile organic acid (VOA) compounds There are three versions of this device, one of which easily fits any 2" well. The other two versions may be used in wells 4-inch-diameter or larger, and will take either three simultaneous 40-milliliter vial samples or a 1-liter sample Construction The sampler is precision machined from solid and tubular stainless steel All crevices and corners have been radiused (hollow- ground) to leave no "square" edges The sampler is sturdy and field-ready and it is stored and carried in a sturdy carrying case which is fitted with an upright can positioner for the sampler when it is being downloaded or for maintenance Maintenance of the sampler is very simple, there aro no moving parts, so there Is nothing to broak down a3ampier components damaged in any manner, ars easily removed and replaced (there are only two, the cap and the body), Even denied (in the miclate), the sampler will still operate and be capable of obtaining a viable Semple (6) apawa n Everything about this sampling device is unique, from its shape to its operational characteristics, this sampler delivers performance unmatched by other devices General The sampler cap is loaded with any standard VOA vial and the cap is screwed to the weighted body. The sampler is then lowered down the well to the predetermined sampling depth at which point the sampler automatically begins filling (sampling) Sampling is facilitated via laminar flow directly into the sample container Low turbidity is achieved through the minimal disturbance caused by the hydrodynamic shape of the sampler 2 of ai 3/7x/99 4 22 PM