Quarries And Built After-Uses

David Jarvis asks why more built developments are not incorporated into mineral planning schemes

The Eden Project, Bluewater retail park and Hampton (the southern extension to Peterborough) are well known developments in quarries; they were, however, all conceived largely after mineral extraction. Why are there not more of them and why were they not integrated with the mineral extraction scheme? A recently published MIRO research project found that in seven counties only 6% of all quarries had a built after-use element. Is this a missed opportunity?

Demand for housing and other built development continues to grow annually. Various techniques such as increasing the density of existing housing, urban regeneration and the use of brownfield land cater for some of this demand, but the remainder has to come from greenfield sites.

Could some existing and proposed quarries not only provide mineral but built development as well?

What is the range of potential after-use?

Current mineral planning guidance (MPG7) states that after-use may include ‘…agriculture, forestry, amenity (including nature conservation), industrial or other development’. Other development is, therefore, not precluded and can cover a range of potential after-uses (see table 1). Why has there been no built development on many of those sites that have no overriding social, economic and environmental factors?

First, mineral planning is dealt with at county level, while built development is handled at district level; this makes an integrated approach difficult. The emergence of regional spatial strategies and local development frameworks, however, may offer an opportunity for joined-up thinking.

Secondly, and historically, mineral operators typically owned the freehold to their sites on which they had one main focus. More recently there has been a trend for operators to lease their sites. The landowner generally has a long-term interest and is now often looking to a range of uses over time, including built development.

Thirdly, quarries with restoration conditions ultimately have the same planning status as greenfield land. It is a common public misconception that old quarries are automatically brownfield sites.

In order to successfully integrate built development into suitable quarries it is essential that interested parties, as with the old local development plans, seek to have sites allocated for an appropriate after-use in the local development framework documents.

In addition, the relatively long timescales relating to quarrying activities may mean that it is not possible to envisage at the quarry design stage what the local development pressures will be when the land is released from operational use. It is therefore important to plan for flexibility of use in the future.

Historically, a desire to minimize social and environmental impacts has led to quarries (particularly hard rock sites) being constrained to the smallest footprint; this typically results in deep, steep-sided holes with restricted after-use possibilities. Public access becomes a problem because of rock falls and other safety issues. The constrained footprint also reduces flexibility in the operation of the quarry, for example in direction of working, materials handling, plant location, and, perversely, this can lead to unnecessary impacts (particularly visual). This often leads to mitigation measures (eg linear bunds), which are, in themselves, intrusive.

An alternative approach considers the resultant landform (the void and associated mounds) as being of prime importance. By generally increasing the land take at the outset, impacts and intrusive mitigation may be avoided. The resultant wider, gentler landform is, in itself, less intrusive but also offers a fuller range of possible uses including built development.

Ironically, quarries contribute greatly to geo- and bio-conservation. There are around 700 SSSIs in former quarries. The alternative approach need not diminish the conservation potential and, importantly, allows a mechanism for long-term sustainable funding of the conservation management by allowing some built development.

Technical issues

Technical issues require careful assessment but methods and techniques can be used to overcome most difficulties. Consideration at an early stage in the quarry planning process can allow the incorporation of solutions and techniques that may facilitate future flexibility of after-use and create a safe, tailored landform for specific uses in the most cost-effective way.

Even at a late stage in mineral extraction many of these techniques can be applied to enhance the after-use potential, particularly by dealing with face stability and access issues. Notable in this regard are the benefits of linking adjacent quarries.

Descriptions of over 20 techniques and mechanisms for maximizing the potential for built development are given in the full MIRO research report (see table 2).

Each of the techniques listed in table 2 can be applied to enhance development potential, for example:

• The provision of wide benches — it is easy to allow for future road widths or building plots.
• Merging adjacent quarries — this can give a wide, developable quarry floor.
• Removing tips to reveal usable land — while tipping material back into a quarry may provide developable land, it will also reveal land under the old tip at original ground level.
• Positive use of microclimate — quarries generally have extremes of microclimate that many of the potential uses require or can benefit from (eg building houses on south-facing slopes).

The full MIRO report draws together the planning, design, financial, technical and environmental aspects.

Figure 1 describes the process of assessing a quarry for future built development.

Conclusion

The main research project came to the following conclusion and made a number of recommendations.

The promotion of built development in some quarries is desirable and would be helped by:

• The integration of mineral and built development in future planning guidance.
• An integrated approach at the regional planning level using possibilities already available under the current planning system.
• Adopting long- rather than short-term thinking in quarry planning and design.
• Appreciating the environmental and development benefits of a larger land take.
• Evaluating financially, technically, environmentally and in planning terms the options, solutions and schemes.
• Undertaking individual site assessments of preferred options by competent persons.
• The employment of a raft of technical solutions and approaches.

The full 120-page research report and findings, which was undertaken by David Jarvis Associates with Prof. Geoffrey Walton and Andrew Crawford, can be found at: www.dclgaggregatefund.co.uk/themeb.htm