Appendix 1: Nationally Standardised Protocol for State of the Environment Groundwater Sampling in New Zealand - Flow Chart
Text description of the flow chart
Some instructions in the Flow chart are in bold text. Such instructions must be done and are noted below.
Further explanation to some instructions of the flowchart are provided at the bottom of the webpage. These are noted by *.
Step 1: Pre sampling |
1.1 Check site details | ||
|---|---|---|---|
| 1.2 Gather equipment * | |||
| 1.3 Calibrate the field meters (must be done) |
|
For calibrating the pH and conductivity field meters the temperature compensation for pH and conductivity calibrations should be checked using chilled standard solutions. If the temperature compensation function is not working, recalibration is required at each site. Use standard solutions at ambient groundwater temperatures. (must be done) | |
Step 2: On-site preparation |
2.1 Confirm correct site | ||
| 2.2 Confirm appropriate sampling point (must be done) * | |||
| 2.3 Check meter calibration (must be done) | Check calibration at each site using at least one standard solution for pH and one standard solution for conductivity. The meter reading must be within plus or minus six percent of expected value. | If the specified criteria cannot be met on-site calibration is required. If recalibration cannot be achieved the meter must not be used. (must be done) | |
| 2.4 Clean sampling equipment | |||
Step 3: Purging |
3.1 Measure depth to water | ||
| 3.2 Calculate volume to be purged (must be done) | Purge volume equals 3.14 multiplied the square of the well radius and then multiplied by the result of the depth to water subtracted from the well depth. The resulting figure is then multiplied by 1000. (must be done) (further explanation) | ||
| 3.3 Install pump if necessary* | |||
| 3.4 Initiate pumping if necessary * | |||
| 3.5 Monitor field parameters (must be done) | |||
| 3.6 Assess adequacy of purging (must be done) | Continue purging until:
|
||
| Step 4: Sample collection | 4.2 Preparation: (must be done)
|
||
4.3–4.7 Collect samples in any order as required:*
|
|||
4.8 Collect sterile unfiltered unpreserved sample if required:
|
|||
| Step 5: Site Clean-up | Clean and rinse all sampling equipment between sites | ||
| Step 6: Sample storage, transport and delivery | The sample storage, transport and delivery step is: Some types of samples require appropriate measures to ensure that adequate chilling during storage and transport. During the day: Samples should be kept in a chilli bin, with at least five frozen pads, or three kilograms of ice. Overnight Courier: Replace frozen pads/ice used during the day with at least three kilograms of ice for overnight transport. Minimise airspace in the chilli bin. |
Nationally Standardised Protocol for State of the Environment Groundwater Sampling in New Zealand (further explanations)
1.2 A preservative is required for some types of sample, (e.g. an acid preservative for samples to be analysed for cations.) Be prepared to chill samples (e.g. for nutrients) to one to four degrees centigrade immediately after collection and for the duration of transport to the laboratory.
2.2 An appropriate sampling point is one that minimises the purging time (see Step 3) and minimises the potential for contamination of alteration of the sample. It is acceptable to collect samples from a short length of clean hose attached to the tap or wellhead.
3.2 For calculation of purge volume:
- Well depth, depth to water and well radius must be expressed in meters in order to derive the purge volume in litres.
- If the depth to water under ambient (non-pumping) conditions cannot be determined for any reason, assume ‘depth to water’ equals zero.
- Well depth can be obtained from drilling log or through the use of the dip tape.
- Well radius refers to the casing dimensions and not to the dimension of the bore.
- If it is not possible to determine depth to water and if the well depth is unknown, then purge volume cannot be calculated. In this case, any samples collected from the well will not comply with this protocol.
3.3 The pump should be installed so that its intake is positioned at least one metre below the static water level and a minimum distance above the top of the screened/open interval of ten times the well diameter (for example, 1500 millimetres for a 150 millimetre well diameter). This will ensure that the sample is representative of the entire screened or open interval of the well.
3.4 A suitable pumping rate produces a continuous stream of water from the pump outlet or sample point without turbulence, entertainment of air or pump cavitation. Compliance with this protocol requires determination of the pumping rate during purging.
3.6 For assessment of adequacy of purging, note that:
- The purging operation requires extraction of at least three times the calculated purge volume and may require extraction of many more that three times the calculated purge volume.
- The field values of temperature, conductivity and pH must be measured on at least four separate occasions, each measurement at least one purge volume apart.
- The differences between the last two sets of field measurements must be the same within the following limits:
- Temperature: plus or minus 0.2 degrees centigrade AND
- Conductivity: plus or minus 3 percent (plus or minus 5 percent if less than 100 microseamen per centimetre at 25 degrees centigrade), AND
- pH: plus or minus 0.1 pH unit
4.3-4.7 All samples must be collected sequentially from the sample point or from a short length of clean tubing attached to the sample point. The filtered acid-preserved, filtered unpreserved, unfiltered unpreserved samples and the samples collected in isolation from the atmosphere can be collected in any order.
4.8 Sterile samples must be collected after all other samples. This is because the requirements for sterilisation could potentially influence the chemistry of samples collected afterwards. Note that sterilisation of the sample point requires the pump to be turned off briefly.
Refer to Groundwater Sampling Protocol for further detailed explanations when required.
