ASTM International

Standard Practice for Design and Installation of Ground Water Monitoring Wells
 N D5092

Annotation

This practice describes a methodology for designing and installing conventional (screened and filter-packed) groundwater monitoring wells suitable for formations ranging from unconsolidated aquifers (i.e., sands and gravels) to granular materials having grain-size distributions with up to 50 % passing a #200 sieve and as much as 20 % clay-sized material (i.e., silty fine sands with some clay). Formations finer than this (i.e., silts, clays, silty clays, clayey silts) should not be monitored using conventional monitoring wells, as representative groundwater samples, free of artifactual turbidity, cannot be assured using currently available technology. Alternative monitoring technologies (not described in this practice) should be used in these formations

The recommended monitoring well design and installation procedures presented in this practice are based on the assumption that the objectives of the program are to obtain representative groundwater samples and other representative groundwater data from a targeted zone of interest in the subsurface defined by site characterization.

This practice, in combination with proper well development (D5521), proper groundwater sampling procedures (D4448), and proper well maintenance and rehabilitation (D5978), will permit acquisition of groundwater samples free of artifactual turbidity, eliminate siltation of wells between sampling events, and permit acquisition of accurate groundwater levels and hydraulic conductivity test data from the zone screened by the well. For wells installed in fine-grained formation materials (up to 50 % passing a #200 sieve), it is generally necessary to use low-flow purging and sampling techniques (D6771) in combination with proper well design to collect turbidity-free samples.

This practice applies primarily to well design and installation methods used in drilled boreholes. Other Standards, including Guide D6724 and Practice D6725, cover installation of monitoring wells using direct-push methods.