Abstract
Hydrogeological characterization is required when investigating contaminated sites, and hydraulic conductivity is an important parameter that needs to be estimated. Before groundwater sampling, well water level values are measured during low-flow purging to check the correct driving of the activity. However, these data are generally considered only as an indicator of an adequate well purging. In this paper, water levels and purging flow rates were considered to estimate hydraulic conductivity values in an alluvial aquifer, and the obtained results were compared with traditional hydraulic conductivity test results carried on in the same area. To test the applicability of this method, data coming from 59 wells located in the alluvial aquifer of Malagrotta waste disposal site, a large area of 160 ha near Rome, were analyzed and processed. Hydraulic conductivity values were estimated by applying the Dupuit’s hypothesis for steady-state radial flow in an unconfined aquifer, as these are the hydraulic conditions in pumping wells for remediation purposes. This study aims to show that low-flow purging procedures in monitoring wells—carried out before sampling for groundwater characterization—represent an easy and inexpensive method for soil hydraulic conductivity estimation with good feasibility, if correctly carried on.
Highlights
Pumping tests are widely used to obtain the estimation of groundwater flow parameters, which are necessary in planning or engineering applications to predict flow and design aquifer extraction or recharge systems [1].In the context of site contamination, both academically and in work practice, it is widely accepted that well purging procedures are necessary to collect representative samples for groundwater characterization [2,3,4,5].The groundwater sampling procedure aims to collect water samples that represent the total mobile organic and inorganic contaminants transported through the subsurface under ambient flow conditions, with minimal physical and chemical alterations from sampling operations [4]
Considering the different case of low-flow purging and according to drawdowns observed during the monitoring campaigns, R values lower than 30 m have been considered
This study aimed to propose an effective and reliable method for aquifer hydraulic conductivity (K) estimation using data coming from low-flow purging activities inside environmental monitoring procedures
Summary
The groundwater sampling procedure aims to collect water samples that represent the total mobile organic and inorganic contaminants transported through the subsurface under ambient flow conditions, with minimal physical and chemical alterations from sampling operations [4]. In this framework, bailers often can’t achieve a correct well purging, whereas high-flow purging produces large volumes of potentially contaminated water, resulting in depletion of quality groundwater samples with higher associated costs in terms of transport and treatment. The reduction of water volumes purged overcomes problems related to its disposal, a theme that often generates many difficulties during working activities [5]
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