Estimation of vertical concentration profiles from existing wells

A method of computing the vertical distributions of solute concentrations i n aquifer strata penetrated by an existing well or borehole can be develope d from a simple solute mass/water balance approach. This approach allows re finement of site characterization without the cost of drilling additional w ells or using other site characterization methods. This method also allows prediction of the water quality impacts of different well construction and screening options when the vertical distribution of flows from an aquifer a nd the aquifer water concentrations are known or can be estimated. Data req uirements and methods of data collection for use of the technique are revie wed. Flowmeter or spinner logging surveys indicate the flow contribution of each portion of the well. When depth-specific samples are collected under the same Dumping conditions as the spinner logging, a solute mass/water bal ance approach allows vertical concentration distributions in the aquifer to be estimated. Application to a well containing arsenic concentrations that approach the maximum contaminant level (MCL) of 50 mug/L indicates that wa ter with arsenic concentrations of nearly 100 mug/L enters the well from a particular stratum.