As winter draws in and nights start to get colder the sight of the gritting vehicles out patrolling the streets will become a common sight. As they make their way up and down the roads and around the car parks and paths some will be wondering effect the gritting process has on the environment.
Both the Environment Agency and the Highways Agency have undertaken numerous studies looking into the effect of salt spreading on the environment. They looked at what happens when the salt interacts with plants and wildlife on road verges and what happens when it gets washed into rivers and waterways. Click nationwide gritting services to find our more information.
Rock salt is the major de-icing agent used on roads in the UK. It can contribute to elevated levels of sodium and chloride in nearby waters when applied to the road service quickly followed by rainfall. However, sampling from streams in spring and found no evidence of significant impact on wildlife. The concentration of salt in the water was not high enough to cause significant long-term damage.
Salt gets into the water as the ice melts; as such the salt has already been partially diluted before it even enters the waterway. Add to this the fact that during the winter months, when salt is being spread, it is unlikely that rivers and streams will be running low (typically experienced in summer months). Actually it is more likely that winter rainfall will mean the waterways are running high enabling more dilution of the salt.
Despite this, gritting contractors are still looking for ways to reduce their salt usage. There are many ways they are going about this. Some are investing in better hoppers that can control the amount of salt that gets laid down, cutting down on over gritting. Some are also looking at using water or agricultural by-products that can be mixed with the salt reducing the overall amount needed making for a more economical service.
Gritting vehicle emissions will also have an impact on the overall sustainability of the gritting process. The gritting process by its very nature relies heavily on its fleet of vehicles. Therefore contractors should be looking at any ways they can reduce their CO2 emissions. Ensure they use good scheduling tools to make sure the routs are as short as possible. Many now use vehicle tracking tools to gather data on distance travelled, using this to inform their rout planning.
We must also remember that there is an environmental impact from the salt production method itself. There are two types of salt commonly used for gritting; rock salt and marine salt. As rock salt requires extensive mining in order to be obtained there will inevitably be some impact on the environment. Large earth moving equipment is used to extract the rock salt, which inevitably produces CO2. Also, as with any form of mining, there are possible risks including erosion, formation of sinkholes and loss of biodiversity. However, when managed correctly the risks can be reduced greatly. For example, the Winsford rock salt mines (the largest salt mines in the UK) is very stable and every tunnel mined is still intact – and there are over 160 miles of tunnels!
The great thing about marine salt production is that, unlike with rock salt, there is no mining involved and therefore none of the associated environmental impacts. Marine salt is manufactured by evaporating the water from brine. Although there are no immediate effects in obtaining the brine, the evaporation process requires the use of heat energy, which again produces some CO2 emissions. The vacuum process makes sure that the process is as efficient as it can be to minimise the effect the process has on the environment. Whilst both of these processes require energy input, neither is considered to be excessive and manufacturers look to maximise their energy efficiency wherever possible.
You should always consider the overall energy impact of the gritting process when considering your winter maintenance needs. Even though the environmental impact is minimal there are things contractors can do to ensure these are reduced further. Whether that is through their gritting methods, vehicle emissions or the process by which their salt is produced.