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As part of Superfund and similar state programs, pump and treat systems have been installed at many sites to control and remediate groundwater contamination. In many cases, these systems have been functioning for five years or more with little change in how they are operated. Although these systems continue to comply with applicable discharge requirements, influent groundwater characteristics might have changed since the systems were designed and put into operation. Accordingly, significant cost savings might be achieved on a project by evaluating the current groundwater pumping requirements and treatment system operation.
Groundwater characteristics
The designs of groundwater treatment systems often are based solely on groundwater contaminant concentrations from monitoring wells. The historical monitoring well data typically are analyzed to estimate the extracted groundwater characteristics. This is done by considering the capture zone predicted by groundwater modeling software. Depending on the availability of data and sophistication of the model, the designer will develop a best estimate of predicted groundwater concentrations. The estimate will incorporate statistical analysis of monitoring well results and the spatial characteristics of the groundwater capture zone and extraction system. If treatability studies or pilot testing are conducted during the design phase, the predicted influent groundwater concentrations are modeled using groundwater from different monitoring wells proportioned to simulate the future extracted groundwater. The samples may also be spiked with particular compounds of concern to simulate worst-case conditions.
Although this approach provides a best-estimate of future groundwater characteristics, it is limited by several factors:
Samples typically are collected as grab...