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Mine Health and Safety Act, 1996 (Act No. 29 of 1996)

Guideline for a Mandatory Code of Practice

Minimum Standards on Ground Vibrations, Noise, Air-Blast and Flyrock near surface structures and Communities to be Protected

Part C : Format and Content of the Mandatory COP

8. Aspects to be addressed in the mandatory COP

 

8.1. The COP must address the management of risks and hazards on ground vibration, noise, air-blast and flyrock incidents emanating from blasting practices at mines.

 

8.2. The COP may be used in conjunction with the standard operating procedures employed at a mine.

 

8.3. Identification of all relevant structures to be protected (pre-survey to be conducted)
8.3.1. The purpose of the pre-survey
8.3.1.1. Identify the specific type of structure(s), for example a public building, public thoroughfare, a railway line, a power line, any place where people congregate or any other structure that may be necessary to protect.
8.3.1.2. Determine the condition and structural integrity of the structure(s).
8.3.1.3. Measure the distance from where blasting is to be conducted to the specific structure and consult with the Principal Inspector of Mines.
8.3.2. A pre-survey must be done, before any blasting commences, for structures that is within the affected area. Where no pre-survey was done before blasting operations commenced, for example at existing mines, a survey must be done as a matter of urgency and relevant requisite information collected.
8.3.3. This information must be used to determine the site-specific baseline limits, restrictions, and conditions to be complied with for ground vibrations, noise, air-blast and flyrock to ensure that there is no significant risk to the specific structures and the health or safety of persons in the determined area.
8.3.4. The principle of “who came first” must be applied. This, therefore, means that:
8.3.4.1. Measures must be put in place to ensure that structures which existed prior to the commencement of blasting operations are protected against the risks emanating from blasting operations.
8.3.4.2. When new structures are built close to the mine boundary and after mining operations have commenced, these structures should be of a design that enables the structures to withstand the prescribed safety limits without sustaining undue damage. It is the duty of the employer to communicate with the community of the prescribed safety limits.
8.3.4.3. During this process, the need for and frequency of the follow-up surveys of the identified structures exposed to risk must be determined by the relevant appointed committee.

 

8.4. Drill and blast design
8.4.1. When significant risk to structures due to ground vibration, noise, air-blast and flyrock is determined, site specific drill and blast designs must be developed by a dedicated multi-disciplinary team consisting of, but not necessarily limited to:
8.4.1.1. A qualified blasting expert.
8.4.1.2. The relevant explosive manufacturer or supplier.
8.4.1.3. The geologist.
8.4.1.4. The rock engineer or geotechnical expert with appropriate Chamber of Mines (now Minerals Council of South Africa) Certificate in Rock Mechanics.
8.4.1.5. Employee representative.
8.4.1.6. Affected community representative.
8.4.2. This team must determine the drill and blast design to limit ground vibration, noise, air-blast and flyrock to below the recommended South African standard as stated in table 1 and 2 below, and as determined by Milestone 5: Scoping of guidelines to ameliorate the effects of blasting on people, domestic and wild animals, dwellings, buildings, and other civil structures (Brovko et al 2016).

 

Table 1: Recommended safe ground vibration levels at the structure that needs to be protected

 

STRUCTURE DESCRIPTION

PEAK PARTICLE VELOCITY

(mm/s)

National roads/tar roads

150

Electrical lines (pylons)

75

Railway

150

Transformers

25

Waters wells

50

Telecoms tower

50

General houses of proper construction

USBM criteria or 25 mm/s

Houses of lesser proper construction

12.5

Rural building - mud houses

6

 

Table 2: Recommended air-blast levels at the structure that needs to be protected

 

DECIBELS (dB)

EFFECT

100

Barely noticeable

110

Readily noticeable

120

Currently accepted by the South African authorities as being a reasonable level for public concern (not more than 10% of the measurement should exceed this value)

134

Currently accepted by the South African authorities that damage will not occur below this level (no measurement should exceed this value outside of the mine boundaries)

164

Window break

176

Plaster crack

180

Structural damage

 

8.4.3. No acceptable levels of flyrock have been suggested, other than to avoid it altogether outside the mine site and/or exclusion radius set by the operation as part of the risk assessment.
8.4.4. If the assessment of the danger zone suggests it may extend beyond the site boundary, then a controlled space or exclusion radius must be created where the public are either excluded or evacuated, and therefore not endangered by the blast.
8.4.5. The predicted values for ground vibration, air-blast and flyrock must be calculated as part of the drill and blast design implemented.

 

8.5. Quality assurance and quality control
8.5.1. The employer must develop and implement measures and procedures to attain practical and reasonable quality assurance and quality control systems, to ensure that every blast is executed as designed.

 

8.6. Monitoring and recording of actual blast results
8.6.1. The employer must implement an effective system, such as Vibrometers, to monitor the intensity of every blast, and record the actual ground vibration, noise, air-blast and flyrock measured.
8.6.2. The specific location of monitoring equipment will be determined during the risk assessment and captured on a plan with reference to the specific blast.
8.6.3. Design predicted values and the actual blast results must be compared. Site exceedances or deviations must be investigated and the impact thereof must be evaluated to prevent reoccurrences.

 

8.7. Management of complaints
8.7.1. The employer must develop and implement effective measures to register and handle complaints emanating from the surrounding communities and any other affected parties.
8.7.2. These measures may include, but are not limited to:
8.7.2.1. Increasing awareness amongst community members through posters, consultations with the community committees, etc.
8.7.2.2. Implementing an effective warning system at the mine to notify and alert the surrounding communities of every planned blasting activity. Such warning system may include measures such as audible alarms or sirens, posters, blast notification boards and WhatsApp-messages for notifying the members of the community and other affected parties of such planned blasting operations.