Spatial positioning of sidewall stations in a narrow tunnel environment: a safe alternative to traditional mine survey practice

Mining house corporate standards of accuracy

Several representatives from the mining industry were contacted in order to determine whether there are “in-house” limits of allowable error used by large mining houses. From the responses it became clear that the minimum standards of accuracy as prescribed by the MHSA are the only limits used [31]. An accepted “rule of thumb” in the South African mine surveying industry has always been that no survey should exceed 20mm in horizontal distance, elevation or co-ordinate positioning. The origin of this “rule of thumb” could have been a derivation from the prescribed limits of error for a standard development survey distance of 60 metres that was normally dictated by the length of a standard 60m steel tape used for underground surveying. The limit of error for a distance of 60 metres according to the MHSA is 17mm, which for a quick reference for the underground surveyor could be rounded off to 20mm. [31]. With the introduction of more accurate surveying instruments, specifically with the introduction of the EDM¹², the acceptable limits of error have become easier to meet with greater consistency.

2.6. Other Corporate Safety Standards and Procedures

In addition to the accuracy requirements the Mine Surveyor must ensure that all surveying work undertaken by his surveyors will satisfy not only the Mine Health and Safety Act but also the health and safety requirements determined by his employer. In order to fully appreciate the environment in which the Mine Surveyor must perform his duties, it is necessary to examine some of the external factors that influence the environment in which the surveyor must operate where “most of the mine surveying must be carried out in cramped quarters, in three dimensions, and must follow the turns, twists and rises of the works of the miners…Dust, deafening noise of drilling and excavating machinery, transportation traffic in narrow tunnels, poor illumination, and very often knee deep water add to the misery of the working conditions.” [30].

In the current international social- and legal environment, most mining companies have adopted a “zero-harm” principle in all the activities they engage in. Traditionally surveying stations have been installed in the roof or hangingwall of mining excavations. In recent years though, the adoption of new mechanized mining techniques has led to an increase in mining tunnel dimensions. This increased height of tunnels can make the safe, fast installation of hangingwall survey stations hazardous when the height of the roof of an excavation increases to a point where the roof cannot be reached without the assistance of a ladder or mobile lifting equipment. Common Corporate Standards and Procedures of mining companies operating in South Africa includes ensuring that all the employees working-at-heights , such as surveyors that have to install survey stations in the roof of an excavation to take all the necessary precautions to safeguard against an accidental fall that could possibly have fatal consequences. Such safeguards include using specific types of ladders, safety harnesses and the performance of on-the-job risk analysis prior to executing the work.
In most development tunnels in the South African mining industry the excavations are in excess of 3metres high to accommodate the mode of transport used in the mining process. This height makes the use of step ladders a minimum requirement in order for the surveyor to place his survey control in the hangingwall of the excavation. In the normal performance of his duties the surveyor will need to gain access to the hangingwall of the excavation when installing a target at the reference point or “backsight”, at the survey station for the installation of a plumb bob to ensure that the instrument is correctly centred under the survey station and at the new survey station or “foresight”. After the new “foresight” has been surveyed, the target at the “backsight” must be removed again. That means that the surveyor is required to access the hangingwall a minimum of three times and sometimes as many as six times, during the installation of a single survey station. The surveyor will be exposed to the risks associated with working-at-heights every time a survey network is extended.
In addition to the risks involved with working-at-heights, the equipment used by the surveyor in order to install his survey control could carry its own unique risk in the form of the “light metals” used in the construction of most modern tripods, ladders and scaffolding equipment. The use of equipment that contains “light metals” in the alloys used is prohibited in mines where hazardous conditions may result due to the presence of flammable gas in the area.
According to statistics from the DMR¹³, Quarterly Newsletter of the Mine Health and Safety Inspectorate, April to June 2010, the largest category of fatalities in the mining industry remains falls of ground, representing 40% of the fatalities in the period January to May 2010. The report states that 18 fatalities were related to gravity induced fall of ground incidents. (Directorate of Mineral Resources 2010) [48]. The exposure to the risk of fall of ground is addressed in terms of Chapter 14 of the Mine Health and Safety Act (Act No. 74 of 2008) which, “requires that at every underground mine and at every other mine where a significant risk of … roof falls exists, an employer must take reasonable measures to ensure that no person is endangered by being struck by rock …” [17].
In the following section the Health and safety requirements used locally and internationally is evaluated and summarized to provide a background to the environment in which the surveyor is required to operate. These requirements are considered the most important factor towards motivating for an alternative method of surveying that would ensure the safety of the survey crew, while at the same time still conforming to the defined accuracy requirements

1. The Occupational Health and Safety Act of New South Wales

The Act from New South Wales states that “Controls must be put in place to ensure workers working at a height of 2 metres or more are prevented from falling… All Supervisors and Managers must: Identify, assess and control the risks to workers or object to fall from a height greater than 2 metres.” [49] This standard is an excellent summary of similar standards issued by most of the mining companies operating in Australia. The Anglo American Fatal Risk Standards: Working-at-heights [50], defines the aim of the AFRS to be “to eliminate or minimize the risk of fatalities arising from working-at-heights .” The standard is applied where there is a potential for a person to fall 2 metres or more, but allowing for a risk assessment to identify high potential fall hazards when working-at-heights less than 2 metres. The risk standard bases the reason for inclusion into the official AFRS as follows: “Falls from heights have contributed to a significant proportion of our fatal and high-potential incidents.” Some of the causes contributing to falls from height include the lack of planning and job assessment, failing to wear a harness and an unstable setup of elevated work platforms. “The application of the AFRS is mandatory at all Anglo American managed businesses and operations.” [50]

It is standard practice on most mines in South Africa that working at a height greater than 1.5m from the floor, constitutes “working-at-heights ”. No documented evidence of incidents involving Mine Surveyors working at heights could be obtained from the South African DMR or corporate reports. A case study from the Royal Institution of Chartered Surveyors makes reference to the following incident:

“A heating engineer was working on a development in Fitzroy Square, London. He climbed an unguarded ladder to a half platform from which he fell some 2.5metres and suffered fatal injuries. The principal contractor on site had not carried out a risk assessment in the area in which the engineer was working, the half platform had no edge protection, nor had the area been declared an exclusion zone. The principal contractor was found guilty of failing to make sure people not in their employ were not exposed to health and safety risks under S3(1) of the Health and Safety at Work etc Act 1974.” [51]

2.6.2. The BHP Divisional Standard Procedure

The standard critical procedures: “Working with ladders and working-at-heights” are used to illustrate the extent of the extent of then risk aversion in the form of formalized procedures to be followed by a person working-at-heights found on most South African mines. The standard describes in great detail the requirements that any person working at heights (in this case the surveyor) must contend with on a daily basis. The standards describe in detail that ladders must be checked before use and must be on “firm and stable ground” [52] such conditions are rarely found anywhere in underground situations. It is important to note that non-compliance to these regulations may lead to dismissal of the supervisor.

The standard procedure states that at some sites it is required that the person working from a ladder “wears and attaches an approved safety harness that must be attached to a point in the hangingwall of an excavation.”. It is importantly to note that these regulations, similar to other industry standards states that, “If a person cannot comply with these requirements, the job must be immediately stopped and a supervisor must be sought” [52]
The BHP Divisional Standard Procedure for Operating and Working with Elevating Work Platforms (EWP’s) DIV-OHS 01-04.2 defines similar extensive procedures to be followed by a person working on an EWP and for the use of the safety harness and personal lanyard DIV-OHS 01-04.6 [53] . All of these standards clearly state that “If you can’t comply, don’t do the job!” [52] This sentiment is voiced in all corporate standards investigated. In the zero-harm, zero-tolerance environment on South African mines. Should a person injured by falling from height be found not to have complied with all the above requirements, such a person will in all likelihood be dismissed as a result of a disciplinary enquiry. Additional disciplinary action will in most cases also be taken against the person’s supervisor.

2.6.3. The Anglo American Fatal Risk Standards: Working-at-heights

The standard compiled by Anglo American defines the requirements for working-at-heights as follows: “… the use of a full body harness, including shock absorbing lanyard or inertia reel is mandatory.” The procedure defines that “…where the work method requires a person to detach and re-attach at height, a dual lanyard system shall be utilized to ensure that at least one connection point is maintained at all times.” Because of the risks involved in case of a person who has fallen and is suspended from his harness “emergency response plans should be available for the rapid retrieval of personnel in the event of a fall from height as response time is critical if a person is to avoid suspension trauma.” [50]. From these standards it can be reasonably deduced that all surveyors installing survey control in the roof of a tunnel is performing work at heights and must therefore comply to the standards. It can be concluded that these standards, although designed to protect the life of employees are not conducive to productivity and speed of operation, such as that normally required from a surveyor in order to delay the activities of the production crew as little as possible in the drilling and blasting cycle of mining the tunnel.