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Management of Natural Resources
What is Management of Natural Resources about?
The Government's strategy for Sustainable Development for the UK 'A Better Quality of Life' (1999) discusses the term Prudent use of natural resources and explains that:
'This does not mean denying ourselves the use of non-renewable resources like oil and gas, but we do need to make sure that we use them efficiently and that alternatives are developed to replace them in due course. Renewable resources, such as water, should be used in ways that do not endanger the resource or cause serious damage or pollution.'
Why is this an issue for the Highways Agency?
The construction, maintenance and operation of the trunk road network consumes large quantities of resources. In 1998 roads represented 3% of the UK's construction work (Source: DETR (2000) Construction Statistics Annual). Between about 20,000 and 60,000 tonnes of aggregate is used to construct a mile of motorway. Over 90% of non-energy minerals extracted in Great Britain are used to supply the construction industry with materials. Yet every year some 70 million tonnes of construction products and demolition arisings are wasted. Some 13 million tonnes of that is material delivered to sites and subsequently thrown away unused. Poor design and planning can also result in wasted time and money and reduced profits.
What is the Highways Agency's goal?
One of the objectives from 'Towards a balance with nature: Highways Agency Environmental Plan' is:
'To develop techniques to ensure that the Trunk Road Network is managed in the most sustainable manner, conserving the existing resource, generating less waste and removing barriers that prevent or inhibit the use of secondary or waste materials.'
How is the Highways Agency achieving its goal?
The Agency considers this theme in three parts. These have been developed from the Office of Government Commerce Sustainability Action Plan and are:
- Re-use or new build - this is the process of decision making to ensure that new build options are not automatically promoted without consideration of other approaches, for instance, to maintain and re-use the existing road, or use waste or recycled material. We are co-operating more closely with industry to identify barriers to the reuse or recycling of highway materials and to encourage the use of secondary and waste materials where practical.
Examples of newly developed recycling techniques are the 'linear quarry' method and the 'crack and seat' technique for concrete pavements. Both involve the in situ reuse of existing pavement materials during reconstruction. This not only reduces the requirement for new materials but also does away with the need for the associated transport movements. - Design for Minimum Waste - for highway construction or maintenance this relates to the fate of any residual material as well as the sources of potentially recyclable material that can be used at the site or elsewhere. See the Reducing Energy the site or elsewhere. See the Reducing Energy Consumption Case Study - M6 Toll Road.
- Aim for Lean Construction - this cuts across many issues for instance, minimising waste, energy and water usage. It also encompasses broader concepts such as value for money, good management (up and down the supply chain) and innovation. For more information see - Partnerships to Better Business.
The Agency also undertakes specific initiatives relating to natural resources, such as the sourcing of timber for fencing and barriers and furniture in HA buildings. There is now a requirement for the timber used in our roadside environment to have certification proving that it has been sustainably sourced.
Some key tools for managing the Agency's operations in relation to the management of natural resource are:
- Better Business Practice
- Environmental Management Systems
- Environmental Impact Assessment
- Guidance and Specifications
Monitoring Progress
The Agency is developing performance indicators for resource use in maintenance contracts.
Future Development
Research is underway to prolong the life of roads and other structures. This includes assessment of durability of selected recycled aggregates in structural concrete. It is anticipated that the output from this project will produce guidance and specifications on the use of such material.
Research is underway to identify the potential for recycled aggregates in pavements and structural concrete and to develop a quality standard for recycled materials. Identifying material sources close to sites will reduce the environmental impact of transportation.
A specification for the use of Incinerator Bottom Ash is currently under development and will be included in the next specification update, further increasing the use of alternative materials in road construction. The table below demonstrates the secondary aggregate material currently permitted for use in road works.
The Agency is currently developing a Quality Management sector scheme for highway lighting which will include recycling of lamps from highway lanterns.
Extending the Durability of Highway Structures
The Agency is increasing the durability of highways structures by:
- Minimising the amount of maintenance required by adopting integral bridges for new construction, eliminating bearings and expansion joints;
- Using new techniques to extend the life of in-service structures such as cathodic protection to minimise corrosion in some reinforced concrete structures;
- Using new techniques to strengthen bridge supports and decks using fibre reinforced plastics (developed for aerospace and marine applications).
All these techniques reduce the need for maintenance / repair / strengthening work; help to reuse rather than demolish structures and are cost effective in whole life terms.
Crack and Seat for concrete roads
Jointed concrete roads can provide poor ride quality if the joints are not maintained properly and the concrete surface is often noisy. For these reasons, even though such roads remain structurally intact, it is often desirable to cover them with a new asphalt surface, but this usually leads to a future maintenance requirement because thermal expansion and contraction at the buried joints in the concrete causes deterioration of the new surface.
Traditional solutions are a thick layer of asphalt or the removal of the concrete, which are both expensive in financial and resource terms. Alternatively, the concrete can be treated using the Crack and Seat method. This involves 'cracking' the concrete slabs with a large guillotine, 'seating' the slabs with a heavy roller, then applying a thin asphalt surface. The new cracks will accommodate some of the thermal movement and the new surface will not deteriorate at an accelerated rate.
When designed carefully and monitored closely, this can be done while preserving most of the strength of the concrete and thus extending its lifetime as a structural layer. Energy consumption, the use of aggregates and the amount of material taken to landfill are all significantly reduced compared to traditional reconstruction and the thin asphalt surfacing reduces noise pollution.
It is estimated that up to July 2002, around £50 million have been saved in terms of materials and user delay costs by the use of crack and seat.
Using Quarry Waste
China clay is an important material for the paper, ceramics, paint and construction industries. Deposits occur mainly in Cornwall and Devon where extraction has been carried out over the last few centuries and continues today. Large amounts of waste are produced in the china clay recovery process and large stockpiles of waste exist adjacent to the quarries. The ratio of quarried china clay product to waste is high, with 1 tonne of china clay giving rise to 9 tonnes of waste. Part of this waste is sand, which due to its consistency has the greatest potential for reuse. China clay sand is a good-quality aggregate, and only needs to undergo the same basic grading and washing processes as other natural aggregates to be fit for use. China clay waste has been used on a number of Agency projects in the Cornwall area and it can be used in most road applications such as in concrete, base layers and foundations.
Case Study Resurfacing the A21
During resurfacing and reconstruction work on roads, part or the entire asphalt surface is planed off. Due to the high quality of material involved there is an opportunity for reuse. Road planings from Highway Agency schemes are not sent to landfill. They are normally taken to distribution storage centres for use on other schemes. However, reusing the road planings on site can significantly reduce the number of lorry journeys associated with the work.
Recycled road planings were recently used in a 4.3km section of the A21 Sevenoaks Bypass. Incorporating the recycled material into the new road surface led to a saving of £216,000 in off site transport costs, a reduction in contract period and reduced delays and costs to the travelling public.
