Remediation

1
Remediation

• Acid tar lagoons risks and sustainable
  remediation in an urban context
• Simon Talbot

2
Legislative compliance

• Part II A of the Environmental Protection Act
  1990
• LAs duty to inspect and identify contaminated
  land
• Special sites
• EAs regulatory duties

3
Acid Tar Lagoons - introduction

• Acid tars are waste residue of petrochemical
  processes - a complex mixture of hydrocarbon,
  sulphuric acid and water, mixed with co-disposed
  materials.
• Acid tars are acidic (pHlt2), viscous, and of
  greater density than water (1050-1440 kg/m3).
• Major contaminants PAHs, phenols, benzene,
  toluene, xylene (BTEX), acid heavy metals and
  sulphate.

4
Acid Tar Lagoons - introduction
Historically, tars were dumped in worked out
quarries, clay or gravel pits
5
Acid Tar Lagoons - introduction

• Problems fluidity lead to bulk tar migration
  through fissures and weathering at exposed
  surface.

6
Is a site Statutory Contaminated Land?

• Development of conceptual model
• Hazard identification
• Risk estimation
• Risk evaluation
• Yes, then site remediation

7
Acid Tar Lagoons Conceptual Model
8
Hazard Identification - Acid Tar Lagoons
9
Volatiles from liquid tar
10
Hazard Identification - Acid Tar Lagoons
11
Dust wind-blow from exposed, weathered tar
surfaces
12
Hazard Identification - Acid Tar Lagoons
13
Leaching from tar into surface water
14
Hazard Identification - Acid Tar Lagoons
15
Direct contact with tar migrating out of
contained site
16
Stakeholders- internal

• In the know but divorced from full effects
• Site owner/s
• Local Authority.
• Environment Agency
• Health protection agency/Primary care trust
• Health and safety officers
• Restoration consultants
• Restoration contractors
• Researchers

17
Stakeholder- external

• Subjected to effects but invariably not fully
  informed and with reduced influence
• Local community
• Local politicians
• Wider community
• Media

18
Risk assessed versus risk perceived

• Public (External) perception of risk at odds with
  professional (Internal)
• Over-estimation of risk- fright factors
• Underestimation of risk- familiarity

19
Acid Tar Lagoons remediation options

• Options include
• Engineered cap
• Stabilization/solidification
• Removal and treatment for use as fuel
• Do nothing
• Full containment
• Restrict access to site

20

• Issues affecting local residents
• 1) Removal based techniques release of
  volatiles, odour, transportation issues.
• 2) On-site treatment treatment plant,
  emissions, transportation issues.
• 3) Stabilization/solidification transportation
  issues, import of material and significant
  volume increase in the final lagoon site.
• 4) Simple fencing off loss of amenity for
  residents, does not lower the risk of dust blow
  off and vapours.

21
Risk communication- why

• Public have a legal right to know
• Familiarity lowers perception of danger and
  unfamiliarity increases perception of danger
• Public participation in remediation process
  (Århus Convention)

22
Risk communication- how

• Overcome low trust in agencies
• Informed
• Inclusive
• Transparent
• Avoid rhetoric
• Avoid alarm

23
Integrating technical and socio-economic issues-
risk assessment

• Site specific
• Precautionary principle
• Protect public from acute risk
• Warn public of chronic risk

24
Integrating technical and socio-economic issues -
remediation strategies

• Remediation process impacts on the public
• Plan for current and future end uses

25
Conclusions

• Appreciation and understanding of risk is
  increasing
• Sustainable remediation acceptable to all
  stakeholders requires a multi-disciplinary
  approach

26
Acknowledgements

• Funders
• EPSRC
• Environment Agency
• Various Acid Tar Lagoon Site Owners