Vibration Monitors
There are five permanent monitors located on the compliance boundary around the perimeter of the open pit and another three around the Favona site. Additional roving monitors can be set up anywhere as required, providing in-fill monitoring to improve our knowledge and check on anomalies or other causes of vibration as they occur.
Not only blasting vibration is recorded by the monitors. Vibration from sources such as lawn mowing, seismic activity, passing traffic and even pedestrians can register. Monitors are triggered by vibration levels as low as 0.5mm/s. The table below gives an indication of the vibration levels generated by some common activities compared to compliance levels at Newmont Waihi Gold's operations.
Blasthub
Newmont Waihi Gold uses the most technologically advanced system available anywhere in the world to manage vibration monitoring and blast design at the Martha and Favona operations.
Developed by Australian company The Saros Group, in association with vibration consultant John Heilig, Blasthub is a state-of-the-art data management system that records and maintains accurate information from several individual vibration monitoring stations, each with its own processor and recording capabilities.
The monitoring stations are active 24 hours a day. When vibration levels exceed a set level the monitors are triggered. This is linked to a central computer at the NWG office which downloads and stores data after each blast event. This computer is in turn linked to a database computer in Brisbane where the information is stored and analysed by specialist consultants.
Blast results are sent via email to relevant staff at Hauraki District Council Environmental and Planning department and various users at Newmont Waihi Gold as well as the vibration consultants. Data are processed and made available on the Blasthub web site, accessible to the authorised users via a password. A security system determines the level of access available to a user and no data can ever be influenced by any user.
Those with access to the Blasthub website are able to gain or register specific information such as date, time, duration and location of each blast, vibration levels recorded from all monitors, complaint details, waveform information and blast design details.
Data charts and graphs and weekly/monthly reporting details can be generated on demand, calculating information to show statistics, trends and compliance levels and supplying information to assist when modifying blast design. Blasthub has the ability to provide information from previous blast events that can be used to plan and design future blast procedures. This enables the company to carry out a proactive approach to ensure that the effects of blast vibration are minimised.
A demonstration sample of Blasthub can be accessed via the web site www.blasthub.com. Here viewers can gain an insight into the capabilities of the programme.
Above is a recent screen capture from Blasthub. The aerial photograph shows the location of a selected blast event and monitoring stations. Beside that is a collection of data provided by each monitor that was triggered by the blast. Blast reports and waveforms can be downloaded to give extra detail as required.
The Newmont Waihi Gold freephone is attended 24 hours a day, seven days a week.
0800 NEWMONT
(0800 639 6668)
Minimising Blasting Effects
The Company uses various techniques to limit blast vibrations. The pit is divided into zones which reflect the sensitivity of nearby residences and different geological conditions. Within each zone blast design can be modified by:
- number of blast holes
- weight of explosive
- amount of stemming
- delay timing
Because the areas being worked in the Martha Mine site are close to the pit rim, for the first time in several years, residences and businesses are more likely to notice effects such as noise and vibration due to blasting. At the end of last year trial blasts were carried out to obtain data to refine blast design so that effects could be minimised. Now that the operational blasting programme has begun the information gained from the trials is applied and every blast is monitored at several locations.
In addition, Newmont Waihi Gold has negotiated a Memorandum of Understanding (MOU) with Hauraki District Council, under which the company will carry out the Southern Stability Cutback work.
In this agreement Newmont commits to undertake the work in accordance with management, monitoring and mitigation plans approved by the Council and to manage any effects in accordance with these plans. The MOU requires the company to continue to use the Blasthub vibration monitoring system and maintain Council’s on-line access to Blasthub.
The MOU also sets out guidelines for establishing and maintaining a working party to deal with issues related to activities in the open pit if they arise.
| Household Activity | Vibration Level (mm/s peak particle velocity) |
| Jumping | Up to 250 |
| Heel Drop | Up to 150 |
| Nail hammering | Up to 100 |
| Walking | Up to 40 |
| Shutting Door | Up to 30 |
| Sliding door | Up to 10 |
| Compliance Levels for Blast Vibration | |
| Martha Mine open pit compliance | up to 5 |
| Favona Underground compliance (day) | up to 6 |
| Favona Underground compliance (night) | up to 1 |