Why did the Navy’s lab change the sample matrix on the laboratory reports from “drinking water” to “groundwater” in September and October of 2021?

The original notation of drinking water matrix appears to have been incorrect and the correction of the matrix to groundwater appears appropriate. Some lab report narratives stated that the Navy’s contractor requested a matrix change from drinking water to groundwater. The samples were collected from a sampling point in Red Hill Shaft but located below the drinking water pumps. The results do not represent finished drinking water. The samples were collected as part of the groundwater monitoring program, from groundwater monitoring sample points, using groundwater monitoring methods. In this case, EPA considers the matrix classification of groundwater appropriate.