Salt supplies for gritting island roads got so wet in outside storage areas this winter that double levels were spread to make it effective.
With the council spending over the odds on grit for the mileage needed, they are now looking at constructing salt storage buildings at Marybank in Stornoway, Urgha in Tarbert and Market Stance in Benbecula to protect supplies from the rain.
Councillors at today’s (Thursday) Policy and Resources Committee will consider setting aside a budget of £700,000 for provision of new facilities at the three locations which could make savings of over £100,000 a year.
A report to members stated that wet or even damp salt was ‘considerably more difficult to apply’ and that recommended moisture content for optimum flow from gritting vehicles was between two and 3.5 per cent.
“When the moisture content reaches as much as four per cent this can often lead to ‘tunnelling’ within the gritter hopper resulting in an uneven distribution of salt on the road, and in a worst case scenario of no salt being discharged. Recent tests on salt at Marybank have found the moisture content to be well in excess of the maximum figure of four per cent.
“To mitigate the effects of salt with high moisture content operatives often open the spreading mechanism which increases the amount of salt leaving the gritter. This usually leads to gritting well above the recommended levels, which for ice conditions would be 20gms per sqm.”
As well as the damaging impact of moisture on the ability to spread the salt, it can also cause damage to the environment through run-off from storage and overspreading on roads.
Officers checked the actual output for 2012/13 and the results have shown that levels have been ‘in excess of twice that desired’.
A new storage facility close to the existing site at Marybank is expected to cost in the region of £300-400k and covered containment for Urgha and Market Stance are also proposed.