The following document outlines a typical fall-out dust monitor application.
OBJECTIVES OF THE PROPOSED PROGRAMME
As the programme for the monitoring must be a credible and a representative assessment of the prevailing fall-out conditions an operation, we propose the following format for the exercise:
The programme must initially establish as much good data on the conditions as possible and thus it is important that the initial sampling period covers the full spectrum of seasonal conditions throughout the year.
Once the seasonal conditions for a full year have been established it will be possible to make predictions and to interpret the continuing monitoring and relate this to climatic conditions, which play an increasing part in the behaviour of fall-out dust.
After discussions with occupational hygienists at the operation, we can consider the full requirement for 4 bucket DustWatch units or 2 bucket units as fixed units with a possible contingent of mobile units that can be used as a mobile monitoring station to enable the operation to carry out investigations on an ad hoc basis wherever an indication of fall-out may be required to be assessed. This may constitute a “nice to have” but will complement the full programme.
In the interest of cost saving we suggest that the client usually set up an assessment facility with local persons trained to undertake the sample collection, carry out vacuum filtering of the samples, desiccation and weighing. In this offer and quotation we have allowed for all supply items, all training and the coaching required, after which we issue documentation as proof of attendance in respect of all persons who have undergone training, coaching and instruction in the use of DustWatch units and the assessment of dust fall-out results.
During the delivery and training trip to the operation we can assist in locating the units at optimum positions. While the fixed units are usually concreted in position, and this could take the client some time, we use the mobile unit to effect training and to coach the monitoring official.
MONITORING FOR HEALTH & ENVIRONMENTAL PURPOSES
From a legal viewpoint, a mine falls under the jurisdiction of the Department of Minerals and Energy with the Mine Health and Safety Act forming the authoritative legislation.
Although the act does not indicate actual limits with regard to dust, it makes provision for the issuing of guidelines by the Chief Inspector.
The guidelines specify the following:
Gravimetric personnel dust sampling has to be carried out on a regular basis with the frequency of monitoring related to the actual risk involved.
The principal pollutant is silica or alpha quartz and the means of ingestion is through the respiratory system and thus the monitoring is only of the respirable or particulate of less than about 7µm.
If the silica content of the respirable portion of dust is less than 5% the allowable occupational exposure limit is 5mg/m3 but should the quartz content exceed 5%, this OEL falls to 0,10mg/m3.
Should any other pollutant/s be present, these will have to be considered as well in a combined air quality index (AQI).
These guidelines do not specify what happens outside the property boundary, although the act makes it clear that the mine's responsibility does not stop at the boundary.
Once outside the boundary, the provisions of the Chief pollution control officer as enacted and vested in the Prevention of Pollution Act and the relevant regulations and guidelines.
These guidelines outline a classification related to that of the American Standard Test Methods, as these are universally accepted as an indication. The procedures, the sampling method and equipment constitute full compliance with ISO 14001.
To indicate the relative classifications we have produced the following table.
Factories and plants are subject to the provision of the Occupational Health and Safety Act, which has similar provisions.
TABLE 1 – VARIOUS CLASSIFICATION AND LIMITS – mg/m2/day
S.A. Classification – Chief pollution control officer
American ASTM – Monthly limit levels
German Din air quality – monthly limit levels
MODERATE 251 – 500
HEAVY 501 – 1200
VERY HEAVY > 1200
HEAVY INDUSTRIAL >1200
Once particulate has been collected on a filter various options are available to the mine and while the ASTM method stipulates only the mass of fall-out dust and limits for this mass indicated as a mass per metre2 per day (m2/day), the samples can be subjected to:
Microscopic examination for possible fibres.
Microscopic examination for pollens and organics.
Physical analysis using XRD, XRF or Infra red spectrometry.
Physical quantitative or qualitative examination using S.E.M. microscopy
4 bucket DustWatch units
With one of the units positioned on each of the 4 sides of the operation it will be possible to establish the nett export and import dust in all directions together with cross flow ambient levels cross checked at each position.
It will also be possible to establish the extent of dust actually produced by the mine, dumps, slimes dams etc on an ongoing basis by comparing an import on one side of the mine with the export of the other side. The difference will establish the degree of mine contribution to the total fall-out dust.
Fall-out dust samples are frequently scanned for ionising radiation in cases where this is potentially problematic. Similarly biological windborne contaminations can be assessed by varying the capture techniques and catch media.
MOBILE DustWatch UNIT
As with many operations using the DustWatch units, an additional 2 bucket unit used as a mobile unit is valuable for use to determine immediate fall-out emanating from a source, which may be sampled on an ad-hoc basis; i.e. fall-out from a blast under various wind velocity conditions to establish the precipitation pattern (open cast mining) or to establish precipitation models. Assessment of particulate and metal fume from a smelter or organic particulate from refineries are also possible with the system.
As part of our offer we have allowed to help your team to establish locations for each unit to optimise the efficacy of dust collected.
We have allowed for training of your personnel with regard to the undertaking of the sampling and assessment of the samples.
A procedural manual is made available, meeting the requirements of ISO 14001.
On completion of the training, documentation providing proof of attendance is provided to trained personnel.
We have also allowed for time to assist the operation with setting up the laboratory equipment and demonstrating the use of this equipment.
We are offering use of the computer programme.
EXCEPTIONS & NOTES
The validity of the above quotation has been fixed at ___ days in the absence of instructions.
The above quotation does not include VAT, which will be charged at ___%.
Laboratory equipment will be quoted separately.
We can offer a sub-micronic oxidation/reduction water filter, which you will need if you do not have a still that can produce enough distilled water for your bucket preparation. For 4 buckets you will need approximately 10 litres of water for each cycle. The water filter by contrast has replaceable cartridges that filter suitable quality water before having to replace the cartridges.
We will invoice the operation on completion of the delivery and training.
Follow up supervision or audit trips will be as requested by the undertaking and will be charged for should you need these.
The DustWatch unit supply is approximately 5 weeks, depending on our stock situation.
Where possible we may be able to combine delivery trips to save on travelling costs. Any saving incurred by sharing trips will be passed on to clients directly.
Gerry F. Kuhn and Chris Loans