Land Contamination: Technical Guidance on Special Sites: Acid Tar ...

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5. SITE EVALUATIONKEY QUESTIONS ANSWERED IN THIS SECTION1. What are the primary pollutant linkages that should be assessed?2. Which pollutant linkages are likely to be the most significant?3. When is it appropriate/inappropriate to apply conventional risk assessment methods to thiscategory of Special Sites?5.1 ScopeThis section is intended to supplement the relevant Model Procedures and associated guidanceon risk estimation and risk evaluation. It highlights the particular issues relating to acid tarlagoons rather than describing the conventional aspects of site evaluation.5.2 Pollutant Linkages5.2.1 Human healthThe principal documented concerns for acid tar lagoons relate to nuisance and to risks tohuman health and safety. These include:• physical hazards associated with soft and unstable ground, which could lead to aperson or piece of plant sinking into a tar lagoon if access or trespass is possible. Itmay seem fairly safe to walk on the surface of a lagoon but in places, remainingstationary for more than a few seconds may lead to a slow but gradual sinking into thesurface. A surface crust can also give a false sense of stability but may suddenly giveway;• chemical hazards associated with contact with acid tar breakout. The acidity (pH
5.2.2 Water environmentThere is little evidence in the literature of investigation or assessment of groundwatercontamination associated with acid tar lagoons and it appears that, in the past, the principalconcerns leading to remedial action have been those documented above.Acid tar lagoons clearly represent a risk to groundwater or surface water (depending on thesite-specific context) and the previous imbalance probably reflects the high cost of addressingacid tar lagoons. This has meant that, by and large, action in the past has been taken when ithas been forced as a result of a situation that is clearly unacceptable in public health terms andhas justified expenditure which, in today’s terms could be in the several million pounds range.However, the assessment of acid tar lagoons in the future can be expected to place a highimportance on assessment of risks to controlled waters. In most respects, the assessment ofsuch risks would follow a conventional approach as documented in the Model Procedures.Thus, there is the possibility of past or future off-site migration both of dissolvedcontaminants (e.g. benzene) or free phase liquid tars and oils. However, there are a number ofconsiderations specific to acid tar lagoons as follows:• whether other wastes are known to have been co-disposed with the acid tars. Thiscould include general demolition type waste for stability reasons, but can also includedomestic refuse (absorptive capacity) and other industrial and chemical wastes.Clearly, account needs to be taken of all that is known from previous investigationsand where these wastes are present in quantities and patterns likely to impact onremedial works, they will need to be characterised;• reduced percolation of precipitation where there is a crusted, low permeability surface;• effect of acidity on naturally occurring mineral deposits, leading to mobilisation ofmetals in strata or other wastes;• effect of acidity on certain natural strata such as limestone and chalk (increasingsolution features and enlarging fissures);• interaction between acid tars and other substances present are especially importantwhen estimating risks to the water environment from acid tar lagoons. These can actto reduce mobility, by preferentially binding the deposits, or enhancing it, due to cosolvencyeffects.R&D <strong>Technical</strong> Report P5-042/TR/04 29
Page 1 and 2: Land Conta
Page 3 and 4: CONTENTSFOREWORDiGLOSSARYii1. Intro
Page 5 and 6: FOREWORDPart IIA of the Environment
Page 7 and 8: CresolsCreosoteDCRDesorptionDesulph
Page 9 and 10: PVCRCRASelosafeSodium saltsSodium h
Page 11 and 12: 1. INTRODUCTION1.1 BackgroundThis r
Page 13 and 14: SECTION 2: INDUSTRIAL PROCESS/FACIL
Page 15 and 16: 1.5 Linkages Between the Gu
Page 17 and 18: 2.1.2 Overview of acid tar lagoon s
Page 19 and 20: Overall CommentsAcid tars can be of
Page 21 and 22: White Oil• Acid tar lagoons from
Page 23 and 24: Box 2.5 Scenario: Acid tar disposal
Page 25 and 26: 3. CHEMICAL AND PHYSICAL CHARACTERI
Page 27 and 28: Table 3.1 - General Physical Charac
Page 29 and 30: The chemicals listed in Table B.1,
Page 31 and 32: 4.2.3 Common mistakesIt is possible
Page 33 and 34: Geophysical methods, such as resist
Page 35 and 36: Investigation locations will need t
Page 37: • gas chromatography by simulatin
Page 41 and 42: 5.3 Assessment of Investigation Dat
Page 43 and 44: 6. REMEDIATION ASPECTSKEY QUESTIONS
Page 45 and 46: 6.2.5 Solidification and stabilisat
Page 47 and 48: Box 6.1 Example of Remediation of A
Page 49 and 50: 6.3 Natural AttenuationNatural atte
Page 51 and 52: Table 6.1 - Remedial Options/Techni
Page 53 and 54: Table 6.2 - Remedial Options/Techni
Page 55 and 56: 6.4 ValidationThe principles of val
Page 57 and 58: • all personnel should follow a d
Page 59 and 60: Verschueren (1983) Handbook of Envi
Page 61 and 62: USEPA. Innovative Site Remediation

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