12.1 Precautionary Salting:
Precautionary salting will take place on the Precautionary Salting Network on a pre-planned basis to help prevent the formation of ice, frost and/or the accumulation of snow on carriageway surfaces.
12.2 Post Salting:
Post salting will normally take place on the Precautionary Salting Network to treat ice, frost and snow that has already formed on carriageways.
Post salting may, in exceptional circumstances, also be carried out on roads or sections of roads beyond the scheduled precautionary salting routes.
12.3 Spot / Ad-Hoc Salting:
Spot salting may take place on parts or sections of the scheduled salting routes either to help prevent formation of ice, frost and / or accumulations of snow or as a treatment to ice, frost and the accumulation of snow that has already formed on the carriageway.
The Highway Duty Engineer will evaluate and consider if spot treatment is suitable and reasonably practicable, using the following criteria below:
- has the request come from the emergency services?
- is there an ongoing emergency at the location?
- do we have multiple reports of hazardous conditions at the location?
- what are the prevailing and forecast weather conditions at this location based on the latest forecast from the weather forecast provider?
Spot salting will only take place beyond the scheduled salting routes in exceptional circumstances.
Depending on the situation and widespread weather conditions we may choose to deploy signs or close the road rather than salting the area.
The Duty Engineer will evaluate and consider what treatment is suitable and reasonably practicable, using the following criteria below:
- has the request come from the emergency services and is it relating to an ongoing emergency at the location?
- has there been a report of an accident at the location and does the risk exists for further serious accidents?
- any action taken must not affect the treatment of the scheduled salting routes
- what are the prevailing and forecast weather conditions at this location based on the latest forecast from the weather forecast provider?
12.4 Instructions to Salt the Precautionary Salting Network:
Instructions for precautionary salting of the network will be issued if road surface temperatures are expected to fall below 1ºC unless:
- road surfaces are expected to be dry, and frost is not expected to form on the road surface
- residual salt on the road surface is expected to provide adequate protection against ice or frost forming
Instructions for salting of the precautionary network will also be issued if snowfall is expected.
The Duty Engineer will issue the instructions for precautionary salting of the network for each of the 22 precautionary routes. These decisions will be posted on the Icelert Bureau and on the DTN system.
The Duty Engineer may issue instructions for post and spot salting and will log these decisions on the Icelert Bureau and on the DTN system.
12.5 Instructions to Salt the Community Links Network:
The Duty Engineer will issue instructions to pre-salt the Community Links Network if snow is forecast, or if temperatures are expected to fall below freezing for a prolonged period.
These decisions will also be posted on the Icelert Bureau and on the DTN system.
There is an expectation that pre-salt action on the Community Links Network would be completed within 6 hours of the action being called.
12.6 Salt:
6mm dry rock salt is used across the county for precautionary and post event salting.
Where heavy snowfall has occurred grit sand will be added to the salt and/or spread on its own to aid traffic movement.
The moisture content of salt plays a major part in the spread rate decision making process.
For optimum performance rock salt should have moisture content of between 2 – 4%.
Moisture contents more than 1% outside of this range must be reported to the Duty Engineer.
Potential actions when salt is outside optimum moisture content range include:
Wet (> 4.5%):
- Review spread rates and increase to account for poorer distribution
- Consider moving wet salt away from the stockpile to dry (in a suitably contained area to minimise environmental impact)
- When the moisture content reaches the optimum range, the salt can be mixed with drier salt in the stockpile or from new deliveries
- Samples should be checked after mixing to confirm that the moisture content is in the optimum range
Wet (< 4.5%):
- Review spread rates and increase to account for poorer distribution
- Consider mixing with drier salt in the stockpile or from new deliveries
- Samples should be checked after mixing to confirm that the moisture content is in the optimum range
Dry:
- For dry salting, assume high losses after spreading
- Consider mixing with salt of higher moisture content in the stockpile or from new deliveries
The moisture content of the salt at each of the storage points will be tested as follows:
- on delivery
- before calibration of spreaders
- once per month through the winter season at all covered depots
- ad-hoc testing following any specific issues relating to spread rates
12.7 Calibration of Spreaders:
All spreaders are to be calibrated as follows:
- before the start of each Winter Service season
- mid-season - One vehicle from each depot to be checked and calibrated at 25 run intervals
- following incidents or conditions that may require recalibration
Should appropriate calibration settings not be met, the Duty Engineer must be contacted so route specific spread rate(s) can be adjusted.
Calibration procedures are to be in accordance with Well Managed Highway Infrastructure and NWSRG guidance.
12.8 Salt Stocks:
Depot |
Capacity |
Minimum Stock |
Blandford |
1,300 |
850 |
Ferndown |
2,900 |
900 |
Wareham |
1,400 |
920 |
Charminster |
4,500 |
1,080 |
Gibbs Marsh |
2,600 |
930 |
TOTAL |
12,700 |
5,800 |
Salt stocks will be replenished before 1 November each year.
Minimum stock levels are maintained for the core winter service period.
Dorset Highways will arrange for the Stock Control Spreadsheet, held within the Winter Service and Emergency folder on the highways computer server to be updated following each treatment of the network.
Dependent on usage, salt stock levels will be replenished as required to ensure minimum stocks are held. This will be subject to the control of the Government’s ‘Salt Cell’.
12.9 Route Treatment Times:
For spread rates of 20g per m2 or less, the Precautionary Salting Network will be fully treated within 2.5 hours of instructed commencement time.
12.10 Emergency Treatment Times:
When an urgent instruction to treat the Precautionary Salting Network is issued by the Duty Engineer, the treatment of the network will commence within 1.5 hours.
12.11 Level Crossings:
Salting will not take place across level crossings as this can adversely affect track side communications.