WorldWide Drilling Resource

21 WorldWide Drilling Resource ® AUGUST 2014 The Importance of Groundwater Sampling by Thomas D. Dalzell, CWD Director of Environmental Research AMS, Inc. The basic steps of groundwater sam- pling are emphasized in this article. Groundwater samples are collected for three main purposes: (1) a preliminary or initial ground- water investigation; (2) part of an ongoing groundwater monitoring program; and (3) for the development of remedi- al action plans (RAP). It is not adequate enough just to know there is contamination in the sub- surface (soil and/or groundwater). The contamination type and concentration must be specifically identified; the exact vertical and lateral extent of the soil and/ or groundwater which has been affected, the type of soil, and the characteristics of the groundwater lithologic zone must be determined. Contamination existing in the soil has the potential to migrate to ground- water. Contaminated groundwater has the potential to migrate off-site. Contam- inated groundwater (on-site or off-site) has the potential to negatively affect human health and the environment. Initial Groundwater Sampling and Monitoring Wells Prior to installation of groundwater monitoring wells, groundwater samples can be properly collected through a variety of drilling equipment and ground- water samplers. There are several types available for sampling groundwater where there are contaminants dissolved in the upper/highest level of the ground- water table. There are also groundwater samplers for determining the conditions of the groundwater when a contaminant is possibly sinking within the ground- water (vertical delineation of contami- nants in the groundwater). If it is not practical to wait until sampling is completed through drilling equipment, a temporary groundwater monitoring well can be installed, so the drill rig can move on to the next task and the groundwater can be properly sampled. If it is known or anticipated that groundwater has been impacted by con- taminants or, if the groundwater has the potential to be impacted in the future by contaminants in the soil, it is impor- tant to implement a long-term ground- water monitoring program. For groundwater monitoring well(s), the type of equipment selected and used to purge and sample is somewhat de- pendent upon the: (1) diameter of the well; (2) total depth of the well; (3) total depth of the groundwater; (4) total number of wells; and (5) location or accessibility of the wells. Summary and Conclusions In sampling groundwater, it is very important the sampling and monitoring procedures be conducted in a way that meets all applicable requirements and accurately represents, as close as pos- sible, the actual level of contaminants which have impacted the groundwater. The fieldwork which involves ground- water sampling and monitoring well installation must be conducted with pre- cise sampling procedures, with a range of acceptable variances that can be applied in actual sampling conditions and safety procedures. The data from a groundwater monitoring program can be used to develop a successful, effec- tive, and efficient RAP. As indicated, groundwater sampling is ultimately used toward groundwater protection and/or restoration activities. Tom Thomas D. Dalzell may be contacted via e-mail at admin@ worldwidedrillingresource.com