An integral component in the investigation of groundwater at any given site is the proper and thorough installation of Groundwater Monitoring Bores (GMBs). GMBs provide the platform for accurate determination of groundwater quality, depth, site geological characteristics and assessment of site contaminant concentrations. Refer to Part 1 of the article here.
Good practice:
Good planning through obtaining a preliminary understanding of the soil/rock conditions, anticipated standing water levels and contamination status of the site will ensure:
- The correct materials are organised with drillers,
- Costs are well understood
- Field staff have a clear understanding of construction requirements.
By also understanding the site and the placement of the bores, decisions on the type of lockable cover to use can be appropriately made.
Bore construction field sheets should be recorded and contain as much information as possible. This includes the bore ID, soil description by depth, GPS location, bore construction details, and any samples or photographs collected. This should be accompanied by a bore development log sheet, which should record the amount of water purged from the bore, visual descriptions of the water, and display the recording of physical parameters (such as pH, Dissolved Oxygen and temperature) stabilising to +/- 10%.
Collection of purged water should occur into a separate collection container, to be held and disposed appropriately offsite, once the initial sample results have been received and the contamination status of the collected purge water is known.
Collection of a reliable drilling log, so that both the driller and the client can see the formation changes. Where soil cores are not being collected, a good driller will lay samples of each metre interval of geology intersected, to provide a visual representation of the bore hole geology, allow for accurate logging by the field staff, and allow photographs to be collected for future reference and reporting.
If soil samples are being opportunistically collected, they should be done so as soon as possible and recorded on bore construction field sheets. Finally, ensure appropriate clean-up of the site and work area is conducted.
Good practice in the installation of GMBs ensures that all reportable information is collected, and can be reviewed and referred to as required through detailed field logs and photographs. It also ensures that bore construction:
- is right for the scope of work
- provides longevity in sample locations
- achieves value for money for the installation of GMBs.
Useful references:
ASTM D5092-04. 2010. Standard Practice for Design and Installation of Groundwater Monitoring Wells, ASTM International, West Conshohocken, PA, 2010, www.astm.org
Department of Water. 2006. Groundwater monitoring bores. Water Quality Protection Note 30. February 2006.
National Uniform Drillers Licensing Committee. 2012. Minimum construction requirements for water bores in Australia. Edition 3. February 2012.