Is low-flow sampling applicable for fractured rock aquifer?
Is low-flow sampling applicable for fractured rock aquifer?
Sometimes low-flow sampling is applicable. The problem with fractured flow is that everything changes compared to flow in wells that are set essentially in granular media. If, through your measurements, you know that you have either upward, downward or mixed vertical flow in the well, you get some redistributed contaminant mass within the borehole. You need to be sure where you are sampling in those situations. If you look at the 1996 U.S. EPA Groundwater Issue paper, they have a specific section on sampling from wells that are set in fractured bedrock or similar settings. The recommendations are to try to use things such as packers to isolate them or a multilevel sampling system. So, as long as you know something about the flow within the well, use the low flow approach in order to maintain low turbidity. However, if you don’t know about the flow in the well, and you have specific fracture flow areas that would cause some upward or downward mixing or movement, you would have to determine whether some other method such as multilevel sampling might be more appropriate.
Sometimes low-flow sampling is applicable. The problem with fractured flow is that everything changes compared to flow in wells that are set essentially in granular media. If, through your measurements, you know that you have either upward, downward or mixed vertical flow in the well, you get some redistributed contaminant mass within the borehole. You need to be sure where you are sampling in those situations. If you look at the 1996 U.S. EPA Groundwater Issue paper, they have a specific section on sampling from wells that are set in fractured bedrock or similar settings. The recommendations are to try to use things such as packers to isolate them or a multilevel sampling system. So, as long as you know something about the flow within the well, use the low flow approach in order to maintain low turbidity. However, if you don’t know about the flow in the well, and you have specific fracture flow areas that would cause some upward or downward mixing or movement, you would have to determine whether some other method such as multilevel sampling might be more appropriate.