A Guide To The Visual Screening Of Quarries

01 February, 2007

By Rob Pile, David Jarvis Planning Associates

‘Will I or won’t I see the quarry?’ This question is nearly always at the top of the public’s list of concerns about a quarry proposal, and consequently also that of the planners. A recently published guide has examined the problem and come up with 20 techniques and solutions, including the most important one of avoiding the need for mitigation in the first place.

‘A Guide to the Visual Screening of Quarries’ is the output from a research project, carried out by David Jarvis Associates Ltd (with technical input from Prof. Geoffrey Walton), which has been part-funded by the Minerals Industry Research Organisation (MIRO) through the Minerals Industry Sustainable Technology (MIST) programme. Additional funding contributions were provided by Brett Aggregates Ltd.

The guide is intended to assist the aggregates industry in its efforts to minimize the visual impact of quarrying activities on receptors in the vicinity of quarries. It examines the need for screening, how this need can be minimized or avoided, and the different methods by which effective screening can be achieved in different contexts. It then considers the practicalities and implications of the various techniques. It is not, however, a geotechnical or engineering textbook, and site-specific advice should always be sought from an appropriate competent person when planning or designing screening measures.

It is hoped that the guide will prove useful not just to the minerals industry but to mineral planning authorities as well, by illustrating the wide range of options and techniques available to remove or reduce visual intrusion.

Quarrying can only take place where minerals naturally occur and more often than not this is in attractive upland or river valley contexts. The industrial nature of extraction means that, unless carefully planned and managed, such activities are often in conflict with their surroundings.

The key objective should always be to remove the need for screening through the design of the quarry itself and the positioning of plant, access roads etc, so that activities are not visible outside the site. Though it should always be the aim, this approach will not always be successful and it will, therefore, be necessary to employ some form of constructed visual screening.

The planning system in the UK, in particular the Town and Country Planning (EIA) (England & Wales) Regulations (1999), will normally require an Environmental Impact Assessment to be carried out for new quarries or substantial extensions to existing sites. An assessment of the visibility of the site will form part of this EIA, together with an assessment of the effectiveness of any proposed mitigation measures relating to visual screening.

The Quarries Regulations (1999) apply to any tip within a quarry, where tips are defined as ‘…any accumulation of material within a quarry’. This means that all screening bunds, landforms and soil/overburden/waste storage mounds are classed as tips under the regulations.

As a consequence of the two regulations described above, the assessment of visual impact and the design of the mitigation measures are enshrined in UK law.

Once the visual impact assessment has been undertaken and the need for mitigation measures established, decisions need to be taken on the type and location of different screening techniques.

In addition to the overall avoidance of the need for screening, the guide examines and details the following solutions:

recreation of previously existing landforms
replication of local landforms/landscape
the use of land use and land cover
the creation of (semi)permanent external slopes
phasing of landform construction
bare earth bunds
naturally vegetated bunds
grassed and planted bunds
retained bunds
interlocking bunds
shrub/tree planting
fencing
walls
ha-has
retaining walls
buildings as screening elements
minimizing the impact of buildings through height, colour, silhouette etc
using stretched fabric/hoardings
using false perspective and trompe l’oeil.

Where space, geology and surrounding landform permit, the use of landform screening has been shown to be the most effective solution, especially when combined with appropriate planting. Landform screening is particularly effective where it later becomes part of the final restoration of the site.

Landform replication

Landform replication refers to attempts by excavation or the placement of materials to simulate natural geomorphological features within the landscape. This is a technique developed to deal with visually intrusive limestone and chalk excavations. One method used in limestone quarries has been restoration blasting, where the technique seeks to form a scree and headwall-type landform found in limestone dales in central England. A similar principle can be applied to other screening landforms.

The relevant area is assessed to establish those natural local landforms that could be repeated as a visual screen. Obvious constraints relate to slope angles and morphology, since screening banks can generally be no steeper than 35º. However, it is sometimes possible to simulate the extension of spurs of land to ‘hide’ a quarry face or quarry operations as a prolongation of a natural feature.

Such an approach is difficult in relation to flat valley landscapes but often viable in more hilly areas or places where glacial features, such as drumlins and eskers, are found. The technique is particularly important for long-term/permanent screening and can be greatly enhanced by planting. It could be used not just to screen quarry operations and final quarry faces, but also post quarrying land use within the quarry, such as housing, commercial or industrial buildings.

The other methods mentioned above have also been shown to be effective in particular circumstances, and again are often most effective when used in combination. Some of these may prove to be more effective than landform screening in situations where the screening is only required for short periods of time.

Buildings as screening mechanisms

Buildings may be used as screens to visually intrusive aspects of quarries. In particular, domestic-scale buildings (eg houses, barns etc) may themselves be of minor or no visual intrusion but may block more distant unattractive elements. Such buildings may be existing or can be part of the proposed quarry development. Frequently, new quarries or quarry extensions are based on farming units where the farmyard complex, farmhouse or cottages offer dual usage as administrative/storage buildings as well as screens to the quarrying activity. New buildings, in particular plant, offices, weighbridges, stores, staff accommodation, canteens and vehicle repair facilities, can be designed to resemble rural complexes such as farm buildings.

Domestic-scale buildings (often in the range 5–10m high) can be located to divert the human eye such that much larger industrial buildings can be screened or part-screened. Free-standing walls (eg 2m high brick walls) can be ‘attached’ to houses and farmyards such that they appear to ‘belong’ in the landscape in a way that they would not if located purely in isolation.

In summary, UK law makes the assessment of visual impact and the design of mitigation measures a priority matter. While the need for visual screening should always be negated if possible, where this cannot be achieved a raft of techniques (singly or in combination) exist to minimize the visual impact of the quarry operations (and the mitigation measure itself). Where possible such mitigation measures should be permanent and a part of the overall final restoration.

For further information contact David Jarvis Associates on tel: (01793) 612173; email: [email protected]