Report of testing and sampling of municipal supply well PM-4

Abstract

During drilling of regional aquifer characterization borehole R-25, located in the western part of Los Alamos National Laboratory (LANL) at Technical Area (TA) 16, groundwater samples were collected from perched zones of saturation and the regional aquifer that contained elevated levels of high explosive (HE) compounds. One of the nearest Los Alamos County municipal supply wells potentially located down gradient from borehole R-25 is PM-4, located on Mesita del Buey at the west end of TA-54. During the winter of 1998 and 1999 the pump in PM-4 had been removed from the well for scheduled maintenance by the Los Alamos County Public Utilities Department (PUD). Because the pump was removed from PM-4, the opportunity existed to enter the well to (1) perform tests to determine where within the regional aquifer groundwater entered the well and (2) collect groundwater samples from the producing zones for analyses to determine if HE contaminants were present in discrete zones within the regional aquifer. The report of the activities that were performed during March 1999 for the testing and sampling of municipal supply well PM-4 is provided. The report provides a description of the field activities associated with the two phases of the project, including (1) the results of the static and dynamic spinner log surveys, and (2) a description of the sampling activities and the field-measured groundwater quality parameters that were obtained during sampling activities. This report also provides the analytical results of the groundwater samples and a brief discussion of the results of the project.