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Construction projects can have a huge impact on the local environment and water supply. Altering landscapes and paving over soil systems if done without consideration for the natural environment can cause huge ecological problems.
The use of some construction materials can be highly water intensive, and, in certain areas of high water charges, this can push up the cost of a build. Using copious amounts of fresh drinking water in construction reduces the total available. The UK has just 1334 cubic meters per person per year, compared to 3065 cubic meters in France and 2785 cubic meters in Italy.
It is important that methods and practices be implemented to save water, not only throughout a building's life, but also during its initial construction.
When construction projects are undertaken they inevitably replace highly permeable surfaces such as soil with non-permeable surfaces such as concrete. This has the effect of water running off and into drainage systems instead of being allowed to enter the topsoil, causing the soil to dry out.
Land is particularly vulnerable to erosion during construction and dirt and silt that washes off of sites can end up in freshwater systems clogging the water, reducing the light available to plant and animal life which can prove fatal. To prevent this it is essential that as little landscaping as possible is done during construction. Plant life such as trees and hedgerows can be planted around natural sources of water on larger builds to act as a buffer to run-off.
A common method of controlling dust on a site is to water it down. This requires a lot of water to be sprayed around collecting silt and man-made pollutants that can soak into the ground. Whilst more labour intensive, sweeping dust from a site will cut down on fresh water used. Weighted tarpaulins and seals should be used to keep dust in containers rather than constantly dampening them.
Other ways of saving water include setting up a temporary rainwater catch tank with the water stored used in spraying although this still does not stop the problem of pollutants entering the soil. Tools should be washed in buckets of water instead of under running water taps.
Different methods of construction also require different amounts of water. Concrete requires water to give it strength and workability.
A typical concrete mix has a ratio of 40% water to 60% cement mix when you consider that 6 billion cubic meters of concrete are used in the construction industry annually the amount of water required is staggering. Plaster is also a water intensive material commonly found on building sites.
Constructing concrete structures off site will improve water usage considerably. This is because factory conditions off site will allow for precise measuring of materials required, in the case of concrete precise mixes can be used with any leftover concrete going straight into production of other units instead of going to waste on site.
The use of factory conditions will also reduce the water used by the workforce, and proper storage of dusty materials will save water used to damp down dust to prevent it from blowing around a site. The lack of concrete dust around by using off site construction will reduce the need for wheel washing of vehicles leaving the site (used to prevent chemicals such as chromium from entering the soil and groundwater).
Where high strength building is not essential, but water conservation is, concrete should be replaced completely. Concrete typically requires a large amount of water to be used during its production, around 30-40% of the pre dried total mass. Concrete will also require hydrating, wasting significant water resources, as well as concrete delivery vehicles which require regular clean-outs to ensure quality does not suffer.
Replacing concrete with lower impact materials such as timber framework will allow a build to make significant savings on the water required to be used around the site. Timber does not require water to be present on the site during construction and the lack of drying time will allow the shell of a building to be assembled far quicker then if excessive concrete is used.
Where roads are to use concrete based asphalts, consideration should be given to what type of vehicle will be using them. Small access roads and driveways can use recycled rubble as gravel instead of concrete creating a double saving of using less water to cover an area and less CO2 used transporting materials off site.
Newer technologies are being invented to replace the cement as a binder in road building including a system developed by the oil company Shell which can use vegetable based material to provide as strong a binder.
Concrete production companies have also recognised the amount of water they use is excessive. Some companies are trying to reduce their water consumption by fitting closed loop water and filtration systems. These take some of the waste water left by the production of concrete and filter it allowing it to be used in production. The material caught in filters can be used to create new concrete and the systems installed on some plants can save 38 million gallons of water per year.
Many concrete plants use heat exchangers to cool hydraulic pumps on site. If these are water powered, savings of millions of gallons of water can be made by changing to air-cooled. When buying concrete for a project research is key and companies which favour water efficiency and are taking pro active steps should be used even if the cost is slightly higher.
Using clay-based plasters will cut water use down while constructing a building. Clay based plasters will have some natural moisture and will require only small amounts of water to be added to make them workable. This compares favourably compared to the amount of water required to make traditional lime plaster and cement based plaster, which can use more the 1kg of water per 4 kg of cement.
Earth based construction methods such as cob building and rammed earth can also help reduce a sites needs for water. Whilst earth based methods do require water it does not need to be a s pure as required for cement and concrete manufacture, water collected from rain water catchment systems will be perfectly adequate. Any run off generated during the use of earth as the primary material will only contain natural substances and will not damage the local soil if it seeps in. Care should still be taken to prevent run off from falling into nearby streams and rivers to prevent clogging.
Using recycled materials will also cut back on the water used within a build. Water is used throughout the production of construction materials and recycling methods all save on the need for fresh water. An example of this is recycled steel, which uses 40% less water per tonne than new steel. Textiles, paper and glass production all require large amounts of water. Where these materials are used they should be sourced from either re-usable materials already produced, or from recycled sources.
Larger companies can introduce an education policy to encourage their workforce to help reduce a sites water usage. Leaving hose pipes and water taps running when not required can be a problem around building sites. Using buckets where possible instead of hosepipes will save water.
Making sure the correct mixtures are used in materials. These are all things which, although simple, when instilled into every member of staff can have a profound effect on a site's water consumption. This also applies to the office staff of an organisation Stringent recycling methods should be in place both at on and off site facilities, to ensure the least amount of water waste is produced. For example dual-flushing toilets fitted into all company buildings, rain and greywater catchment systems etc.
Vehicles should be maintained to the highest standard to allow them to run as efficiently as possible. Leaking oil and coolant can have a profound negative effect on the local environment if it reaches the groundwater of a site.
One litre of oil can contaminate one million litres of water so it is especially essential for sites located next to streams that vehicles do not leak and that any oil or water drained from them during maintenance is disposed of safely and through the right channels.
Landscaping should be kept to a bare minimum in order to reduce the risk of harming the local environment and watercourses. Where possible existing vegetation should be left to prevent the soil from drying out, which is a hidden form of site water usage. Using bags filled with wood chips and other natural materials around the edge of dug trenches will help shelter the exposed earth from the sun and prevent drying out as well as providing a supporting wall to the soil.
Water usage in construction will vary substantially between projects depending on the size and type of the building as well as the materials used. Where water conservation is key intensive building materials such as concrete should not be used and alternative methods sought. The result of reducing water use in the construction industry will have a result on society as a whole by being aware of water efficiency from the early stages of a building's life.
An attitude of water conservation will continue throughout the building's life-cycle. Knowing a building was constructed using the minimum amount of water possible will allow individuals and large corporations to know that they have made a difference in keeping this essential natural resource readily available for the future.