Mark Readman, highway services manager at Durham County Council recounts how a local supplier devised a cool way to clear up a potentially hazardous chemical spill.
The A691 Framwellgate Peth is a strategic route through Durham and is critical in keeping the city moving.
As it leads away from the city centre and bends under the railway station, the very busy and at times congested road becomes a dual carriageway and climbs towards County Hall.
At around 10am on 5 April this year, a Durham local highways inspector was undertaking an inspection nearby when he received a phone call from the operational hub.
As he approached the site he found both the fire service and the police on site. On speaking to the emergency services he learned that an unknown vehicle had deposited an unknown material onto the inside northbound lane of the dual carriageway, over a section of approximately 800 metres.
The surface of the road appeared waxy and was slippery underfoot but treacherous to vehicles due to the bend and incline.
While investigations continued to establish the spillage material type, measures were put in place for traffic management to close the affected lane.
That afternoon, utilising CCTV footage from roadside cameras, the offending vehicle was identified and the material type confirmed.
A tanker carrying a heated liquified raw material for use in the cosmetic industry – “Parafol 18 - 97” – had spilled its contents on the bank and left the site. When spilled, the liquid ran and spread, and as it cooled it solidified into a wax state.
Once the vehicle was identified the chemical data sheet was soon obtained. This revealed the following human and environmental hazards:
- May be fatal if swallowed and enters airways
- Dispose of contents/ container at an approved waste disposal plant
- Do not flush into surface water or sanitary sewer system
- Melting point/range ca. 28 °C
- Flash point ca. 152 - 160 °C
- Heating can release hazardous gases
- Vapours may form explosive mixture with air
This offered little help with regards to the clean-up operation.
In its solid state on the road, the chemical was not hazardous, but if heated the material was flammable and toxic to breathe.
The initial call for the clean-up operation was to Durham’s framework supplier Nordic Products and Services Ltd as the council had worked closely with the firm on a number of clean-up operations across the county.
Managing director Peter Robinson travelled to the site immediately to inspect the spillage. It was initially thought the material would be removed with a hot water pressure system, but this option was not suitable due to the hazards outlined above.
Another suggestion from the council was that the spill could be removed by cold planing the affected area and replacing the existing hot rolled micro asphalt surface. This solution was less cost-effective but the pressure was mounting to remove the spillage and re-open the busy strategic route.
On liaising with our surfacing contractor, Rainton, the council encountered similar risks with regard to temperatures generated through the planing operation and the volatility of the chemical.
With no solution at hand we further engaged with Nordic to consider any alternatives to safely remove the chemical. Peter Robinson advised that he had undertaken dry ice cleaning on subway trains and that this application may provide a suitable solution.
The dry ice cleaning process was compliant with the risks identified in the data sheet and was given the go-ahead.
Nordic quickly arranged for the appropriate plant, equipment and dry ice product and began the clean-up operation.
The specialised process involved the use of dry ice as a blast media. Propelled using air pressure, the dry ice pellets create a thermo-dynamic explosion on contact with the surface. This then displaces the contaminant, allowing it to be collected in solid form using vacuum units and brushes.
In this case, the process averted the known risks as there was no water or heat involved and did not create run-off into the drainage system or environment.
Working 24 hours a day in 12-hour shifts, the teams Nordic from completed the work over 10 days, due to the nature of the product and the size of contaminated area.
While daytime work took place with one northbound lane open to minimise traffic disruption, night work was completed under full carriageway closures.
Nordic’s dry ice cleaning caused no damage to the road surface, with skid testing confirming that the cleaned area was performing as well as a newly laid road.
Through close working with the police the haulier responsible for the spillage was quickly identified and the associated costs of the clean-up operation will be dealt with by its insurers.
The chemical spill had posed a real risk for Durham, firstly because of the skid risk on the major strategic route but also because of the environmental and health and safety implications of the product.
But, working collaboratively with Nordic, we were able to implement a cost-effective solution to a unique problem utilising innovative cleaning methods.
This is a great example of how collaborative working with local suppliers can provide innovative solutions to meet emergency and challenging situations.
The project was such a success that the staff from Durham CC were recognised through the internal 'Great Staff Great Stuff' awards. This was also awarded to Nordic to acknowledge and celebrate its great work and a job well done.
