High stress low-flow (HSLF) sampling: A newly proposed groundwater purge and sampling approach

Representative groundwater sampling is critical for establishing contaminant distributions, evaluating the effectiveness of remediation operations, monitoring the protection of human health and the environment, and sustainably managing groundwater resources. However, traditional low flow (low stress) or three-well-volume purge well sampling techniques can render high labor costs or high wastewater volumes. Newly developed passive samplers can only deal with limited analytical needs. A new High Stress Low Flow (HSLF) method is proposed involving dual pumping rates, which may significantly reduce purge time and wastewater production, while maintaining analytical needs, thus offering a new tool to promote green and sustainable remediation. A three-dimension numerical model was used to evaluate the potential benefits of the proposed HSLF approach. Compared to low flow sampling and three-well-volume purge methods, it was calculated that HSLF can reduce sampling time by up to 81.0% and 81.3%, respectively, and reduce wastewater production by up to 12.5% and 91.2%, respectively. The improvement achieved was affected by formation characteristics (e.g. hydraulic conductivity) and operation parameters (e.g. pumping rates and drawdown control). Further optimization and field testing is required to recognize the full potential of this newly proposed method.