De-icing Agents
Environmental Risks Posed by De-icing Agents
Steve Wenham
Technical Advisor
Pollution Prevention, E&B
Please Note That This Presentation
Was Prepared Before Submission
Of The Final Project Report
Steve Wenham
Technical Advisor
Pollution Prevention, E&B
The problem – the scale
Chloride: Use of rock salt and marine salt on roads, residential areas and business
premises
1.5 - 3.3 million tonnes salt used on the strategic road network
49-109 tonnes of salt per mile of road
75% of this will enter the water environment - the remainder will impact on land
quality
.
2000 parts per million peaks of chloride which is 10 times the environmental water
quality standard
Ammonia: Use of urea around airports
BOD: Use of Agricultural bi-products added to rock salt (and use of formates and
acetates)
Problem - Diffuse Pollution
Growing recognition that de-icing agents (chlorides)
contribute to diffuse pollution
Link well established in America and Scandinavia
Situation in UK less well understood, but concern
growing as:
Increasing pressure on transport owners and
operators to use de-icing agents (economic
impacts and media attention)
Increasing pressure on e.g. business / retail units
to use de-icing agents (economic impacts and
increasing risk of litigation)
Diffuse pollution = 49% of the pollution responsible for
Water Framework Directive failing water bodies
Greater focus on mitigating diffuse sources of pollution
Project Objectives
To achieve better understand of
the impacts of de-icing agents
and their contribution to diffuse
pollution
To provide detailed analysis of
water quality data
Develop a framework
methodology / tool for assessing
the risks posed by de-icing
agents.
Project Approach / Outputs
Phase 1:
Literature Review
Existing Data Analysis
Development of Risk Assessment
Tool
Phase 2:
Field Sampling - analysis of existing
continuous monitoring sites
Testing / refinement / validation of
Risk Assessment Tool
Development of working relationship
with operators – National Winter
Service Research Group
Literature Review
Summarises current understanding of:
Use of de-icing agents
Environmental impacts of de-icing agents
Legislation regarding the use / control of de-icing agents
Mitigation measures
De-icing Agent ‘Fact Sheets’
Risk assessment methodologies
Benefits:
Enhances current knowledge / awareness within the Agency
Provides consistency in understanding / approach to queries
Provides basis for the development of internal guidance –
Operational Instructions
Data Analysis
Fig. 1: Continuous monitoring of stream temperature (red) and conductivity (blue)
over time (5 years) in the River Lee (London)
Fig. 2: Continuous monitoring of stream conductivity and rainfall over time
(4 days) in Brighton Stream (Cornwall) following salt applications
Risk Assessment Tool
What it does:
Estimates total input of de-icing agent to a catchment
(tonnes / year)
Identifies / assesses potential risk factors associated
with a catchment area
Estimates potential ‘worst case’ concentrations at
particular outfalls
Benefits:
Enables comparisons to be made with other sources of diffuse pollution
Identifies those catchments more vulnerable to de-icing agents / diffuse pollution
Calculates potential concentrations of de-icing agents (chloride) at specific
outfalls
Enables EA to focus limited resources on most vulnerable catchments
Project benefits
Risk assessment tool for
estimating de-icer
impacts
Ability to identify road
salt impact at specific
sites related events
Benefits
Development of
partnership with the
National Winter Service
Research Group
Development and
support of technical
knowledge for
operational staff
Summary
Increasing pressure to apply de-icing agents to keep businesses and transport networks
open
Water bodies prone to repeatedly high (but short-lived) pulses of chloride following deicing agent (salt) use and rainfall
Monthly sampling does not reflect / capture true impacts but continuous sampling does
Chemical water quality of flowing water bodies recovers quickly but ecological impact of
repeated pulses of chloride is not well understood
Literature review provides Agency staff with latest knowledge
Risk assessment tool provides Agency staff with method to:
Estimate total inputs of de-icing agents in relation to other sources of diffuse pollution
Identify more vulnerable catchment areas
Identify / prioritise areas where further investigation / mitigation may be required
Links with NWSRG provides direct contact between Agency staff and users of de-icing
agents (transport owners / operators) to facilitate discussion and uptake of best practice
What next
Provide operational instruction for use of risk assessment
tool and for responding to de-icing agent queries
Facilitate on-going discussions with NWSRG and other
user groups to promote best practice
Build up database of continuous monitoring sites to
support further understanding / impacts in specific
locations
Investigate ecological impact of repeated pulses of
chloride
Investigate the need to introduce a max EQS for chloride