Hollow-stem auger drilling (HSA) is the international standard for characterizing hydrogeologic conditions and installing monitoring wells at contaminated sites. Soil sampling and well construction are performed without removing the augers from the boring, preventing cross-contamination and borehole collapse. Undisturbed soil samples are collected ahead of the augers using a split-spoon sampler. Specific intervals or the entire boring can be sampled continuously to identify exact depths of potential migration pathways, confining layers, critical stratigraphic changes, or contaminated intervals. 

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Using HSA, wells are constructed inside the augers, allowing precise placement of the well screen, sand filter pack, and transition seal. Bore walls are stabilized by the augers, insuring sand pack and well seal integrity. In addition, HSA does not require use of drilling fluids that could alter groundwater chemistry and dilute contaminant concentrations.

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None of the drilling methods currently being used in India (air rotary, mud rotary, hand auger) are capable of collecting undisturbed, depth-specific soil samples.

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HSA works best in depths when drilling in contaminated areas. A hydropunch sampler can be used to collect grab groundwater samples from targeted intervals to identify migration pathways and evaluate vertical and lateral extent of dissolved contamination. Unconsolidated sediments and highly weathered bedrock. HSA cannot drill in consolidated bedrock conditions, or where large cobbles or boulders are present.