By far the most important aspect of air pollution in relation to open cast coal extraction is the generation of dust. Unfortunately dust generation is an inevitable consequence of minerals working. Dust is also the generic term used to describe particulate matter, which, although it may be found resting on the ground or other surfaces as 'solid' matter, is capable of becoming airborne to disperse in the atmosphere prior to returning to surface. In construction work, the term generally applies to rock product less than 2mm after crushing. Nuisance dust may be described as the coarse fraction of airborne particulates, typically greater than about 20 µm (microns), although there is no standard definition.

Short for micrometer, a micron unit of measure that is 1 millionth of a meter, or 1 thousandth of a millimetre. A human hair is typically just under 100 microns in diameter, and a human cell is typically several microns across. A grain of salt is about 60 microns and the eye can see particles to about 40 microns. The Environment Agency states that particles larger than 30 - 50 µm tend to be deposited quickly and as such is generally a nuisance. Such settled particles may show up as a deposit on clean surfaces such as cars and window ledges. Deposited (nuisance) dust gives rise to the greatest number of complaints from local residents, and fears are commonly expressed in relation to the alleged health effects. Without appropriate alleviation, residents can potentially be affected by dust up to 1km from the source, although concerns about dust are most likely to be experienced near to dust sources, generally within 100 metres depending on site characteristics.

The Polkemmet reclamation scheme can be divided into broadly 3 areas, where surface materials will be removed as part of site operations. The first area covering the central part of the site is overlain by colliery spoil. Peat occupies a large area at the southern and southwestern ends of the site and the majority of this material will also be handled using large excavators. Generally peat has very high moisture content and dust generation from these activities is unlikely. Furthermore, the location of the peat stripping operations is relatively remote to the sensitive dust receptors. The remaining areas of the site will be stripped of soils and is generally confined to the lower lying areas in the north and northwest of the site. However other areas in the southeast and central area between the bings will also be stripped on a phased basis. Soil stripping will be carried out using small excavators and articulated dump trucks during the driest conditions of the summer months and only a relatively small proportion will be stored in perimeter mounds. The remainder will be placed directly to restoration, wherever practicable. Most of the soils at Polkemmet have high water content and this will inhibit dust generation other than in the driest of conditions. As the excavation proceeds, the depth of working increases and this means that the active area gains some protection from the wind. The major excavation areas (Areas A, B, and C) are located upwind from the major bings, which will provide a screen to the main residential areas and the sensitive receptors in the east and northeast. The bings themselves will also be reduced behind an outer screening face.

A study carried out by the DoE concluded that complaints relating to dust deposition were most likely within 175 m of the source but in the event of unfavourable meteorological conditions e.g. a dry windy day in conjunction with a significant dust source, this distance could be up to 500m but that may be considered worse case scenarios...although with the Whitburn weather...who knows.

There are a number of receptors (locations) that can be considered to be sensitive to dust. These include, but are not limited to the following:

• Residential dwellings;

• Hospitals;

• Food processing;

• Certain hi-tech industries and/or business operations;

• Schools;

• Horticultural areas.

This map shows an imaginary 500m zone of influence from the site boundary. The boundary encompasses the overall limit of excavation, together with the principal soil storage mounds and areas of colliery spoil. Most of the potential dust generating activities will take place within the limit of excavation, although the storage of soils and some operations involving the removal of the existing Bings will take place beyond these limits. Because of this, the zone of influence from the site boundary has been shown at 500m to take into account the DoE study mentioned above. The map also shows the potentially sensitive dust receptors, which have been agreed with WLCEHD and are representative of all the types of locations as shown in the list above. It is clear that the 500 m zone of influence encompasses residential areas of Whitburn, Longridge and Fauldhouse.

Weather conditions such as wind speed and direction and rainfall will influence how and where dust is dispersed as will other factors such as the moisture in the ground (where it is being excavated) and the topography of the land i.e. the bings themselves, as mentioned before, will be natural dust catchers as will the numerous tree lines situated around the site. The Beaufort wind scale determines a moderate breeze of around 6.7 metres per second (6.7m/s) as being able to raise dust. Therefore, given the nature of the materials (including wet, peaty soils) and the proposed operations at Polkemmet, dry winds exceeding a mean of 6.7 m/s (13 knots) would be required to produce airborne dust. Weather data gathered recently shows that throughout the year, southwesterly winds tend to dominate with the exception of May when it tends to be easterly winds. Dust generation and dispersal is generally highest on dry, windy days, particularly when these coincide with specific dust generating activities. However, a sensitive location is only at risk of dust deposition if it is downwind of the source. This means that sensitive locations in Whitburn to the northeast of the site (i.e. downwind of the prevailing winds) are most at risk. The residential areas to the south and southeast are at lower risk of dust from the site as they are not in the prevailing wind direction. However to ensure that all the bases are covered, five receptor locations have been chosen as sites for Osiris dust monitors.

The map shows the receptor sites as green squares and those with Osiris monitors as red squares.

The monitors are currently sited at:

 

Cultsykefoot is at a minimum 150 m away from Coal Extraction Area (CEA)-E. This area has almost been completely worked out i.e. the coal has been extracted but the compacting process may generate dust. The monitor is not shown in this photo and the cottages for the most part are shielded by the terrain and tree lines. The photo here shows the line of sight to CEA E1 to E3.

 

 

 

Polkemmet Road (residential area) is approx. 350 m away from a small part of CEA-E and a soil mound. This photos faces south to southeast and the nearest work is that of CEA E8 to E10.While the monitor is fairly exposed, the houses in Polkemmet Road are relitively shielded by a line of trees up the side of the road.

 

 

 

Kepscaith Farm is over 250 m away from CEA-D, which includes No 3 Bing. Most of D (the southeastern part of the scheme) has already been coaled out but the delicate removal of the burning bing will mean that this monitor is absolutely crucial.

 

 

The Osiris dust monitor in Longridge is just off the A706 as you enter the village from Whitburn and like the Kepscaith Farm monitor will be crucial when No 3 Bing is removed.

 

 

 

 

The Osiris Dust monitor is Fauldhouse is situated on top of the Community Education buildings and being high up will monitor the situation when there are easterly winds

The other receptors shown on the map are either generally upwind or over 500 m away from the nearest activity.

Continuing monitoring and assessment is carried out using the Osiris dust monitors as shown which measure suspended particulates, wind speed and wind direction. Directional sticky cylinder gauges (purpose made adhesive slides mounted in a collection cylinder) are also located at other sensitive receptor locations. These are exposed for short periods, around 1 -2 weeks and the dust collected is then analyses using computer software. The data that becomes available from the Osiris monitors, including wind speed and direction information is made available to site management to enable an ongoing review of best working practices. Temperature and rainfall data will also be obtained from an on-site weather station.

The operational monitoring includes visual assessments of dust emissions and weather conditions, which is cross-referenced with the monitoring data gathered prior to work starting on the site providing baseline data.

So what mitigation has been incorporated into the works?

The soil is excavated using hydraulic excavators and minimising drop heights and matching the right type of excavator to a dump truck to prevent spillages on haul roads reduce the potential for dust emission. Wind speed and direction are taken into account when organising tipping operations.

These large wheels from a Caterpillar 777D are 8 feet in diameter and could churn up a fair dust storm if unchecked so speed limits are enforced thus cutting down on dust emissions from the various haul roads throughout the site. To further reduce dust emissions these roads are often watered down using specially designed vehicles which traverse the site spraying water as shown to ensure that dust emissions are kept to a minimum.

All the site contractor’s vehicles that operate at Polkemmet reclamation scheme have upward facing exhausts and radiator cowls. The use of vehicles with upward pointing exhausts and radiator cowls is moderately effective in reducing potential dust emissions i.e. powerful exhausts pointing downwards have the potential to easily stir up dust especially on those tracks which have not been watered down.

The coal is being processed at the on-site facilities located near Cult Farm which is screened from the prevailing wind direction by the fireclay stockpile, together with topsoil and subsoil mounds. Road going coal transporters are sheeted before leaving the site.

Off-site haulage is limited to the removal of coal from the site. This is at an average rate of approximately 60 loads per day, once the seams are exposed. A fixed wheel wash facility has been established near to the site access and a road sweeper is used on a regular basis to clean the site access and adjoining main road.

Restored areas are seeded with grass as soon as practicable to prevent wind erosion of soils.

All site staff, including contractors, has received (or will receive) appropriate training in order to ensure that employees are conversant with the site dust control strategy.

If dust trigger levels are breached specific measures are taken to immediately reduce any problems. These can range from additional watering of the site, speed limits being reduced even further to a whole scale suspension of site operations. These measures are done in consultation with West Lothian Council.

In overall terms, there is potential for a small decrease in local air quality during site operations but it is only for short periods and agreed air quality criteria will not (and should not) be exceeded. This is largely because site activities are unlikely to generate a significant quantity of air born dust; although this is routinely monitored and action is taken in accordance with agreed trigger levels and site management plan for dust.