New Low-flow bore sampling capability
Many resource consents are now including the requirement for environmental monitoring bores to be sampled using the more modern low-flow sampling methodology, as opposed to the traditional technique of purging multiple times the well volume before collecting a sample. Low-flow (or low-stress) sampling is carried out using highly specialist equipment that is capable of pumping ground water from depth at very low flow rates
Conventional well sampling involves purging at least 3 times the well volume before collecting a water sample. Due to concerns that this process affects the water chemistry in a way that results in the sample not being representative of the actual groundwater conditions, there has been a move towards alternative sampling methodologies to collect samples that better reflect the groundwater chemistry.
Low-flow sampling involves using a submerged pump to draw ground water without causing any drawdown to occur within the well. This is achieved by pumping at rates lower than that with which water enters the well from the surrounding formation, usually less than 1L/min. In order to make sure that the sample being collected is representative of the water chemistry at that particular point various parameters such as pH, conductivity, dissolved oxygen or temperature may be measured at the same time to ensure that the water chemistry is stable before actually collecting the sample. Static water level may also be measured to make sure that the water level in the bore is not dropping as water is pumped out of the well, which would indicate that the flow rate is higher than the rate that the well is able to re-charge.
As well as offering conventional bore sampling through our Auckland, Wellington, Christchurch and Dunedin laboratories, we are now able to a low-flow sampling service throughout the Canterbury region.
