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

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vegetation, black or dark brown staining and, of course, any sign of oozing tars. A rangingrod or similar implement may allow the ground to be probed for evidence of soft ground andtars. As this is withdrawn, any free liquids/tarry deposits remaining on the end may be testedfor pH using appropriate pH papers or detectors.4.3.2 Site investigationApproach to Site InvestigationsIn relation to acid tar lagoons, the following issues are of particular relevance when planning aninvestigation strategy:• likelihood of contaminant migration away from the lagoons (e.g. into groundwater andsurrounding soil);• many sites will have few records of the composition or extent of lagoons, due to theirage, which can be in excess of 100 years. In such cases, aerial photographs can be ofparticular benefit in determining their extent and location, as can local residents andformer employees of the producing works. In some cases, satellite images may beavailable that reveal impacts on vegetation (usually requiring specialist interpretation);• geophysical techniques may be useful in delineating both the extent of lagoons andalso the nature and thickness of the capping layer;• an investigation will need to take into account the presence of features that couldallow migration of tars away from the lagoon e.g. old mine workings, conduits,drainage channels, solution features etc; and• key pieces of information relevant to planning the study include the type of refiningoperation likely to have given rise to the waste, the period of filling, the origin andidentity of fill materials (including any wastes) and any treatment that has been carriedout.A phased approach to site investigation in which exploratory sampling is followed by a moredetailed study is appropriate for acid tar lagoons. However, exploratory sampling may not beneeded in all cases (e.g. where the existence of a lagoon is obvious). In designing thesampling density and locations, it may be possible to restrict the number of samples on thegrounds that it is known that the material is homogenous.Some acid tar lagoons are quite heterogeneous. For example, investigation of an acid tar pitin Derbyshire found that “fill products ranged from materials involved in the process ofreprocessing used oils (tar product, fullers earth and free flowing lubricating oils) to foundrysand, mining spoil and household refuse.”, (Nesbit et al 1995). In this case, during remedialstages, it may be practical to segregate and deal with the different wastes separately and thusgreater quantification via a more intensive sampling regime may be warranted. Where thereare only discrete pockets of non-acid tar wastes all of the wastes are likely, in practice, to betreated as special waste and the variability within the lagoon need not be quantified to thesame degree.R&D <strong>Technical</strong> Report P5-042/TR/04 22
Geophysical methods, such as resistivity surveys, ground penetrating radar (GPR) andshallow seismic surveys can be used to define the boundaries of lagoons, subject to certainlimitations of each approach. The simplest technique is GPR, but this should be combinedwith a resistivity or seismic survey in order to improve confidence in the interpretation of theresults.When planning an investigation, careful consideration should be given to the possibility ofoff-site migration of contaminants in groundwater from the base of the lagoon, especially atolder sites. Estimated contaminant travel times and contaminant flow direction should beused to assist in the planning of any groundwater survey.The migration of liquid tar from acid tar lagoons is a possibility, although it is unlikely tohave occurred in most cases. Old mine workings or conduits could, however, allow migrationof tars as could fissured strata. Investigations of groundwater quality should be conductedwith the possibility of migration in mind, with a selection of monitoring wells being screenedacross the water table (liquid tar or free phase hydrocarbons will tend to float on thegroundwater).Intrusive WorksWith regard to the use of intrusive investigation techniques at acid tar lagoons, the followingpoints are relevant:• careful consideration should be given to the methods adopted for the site investigation,as the ground may not be strong enough to support conventional drilling/excavationequipment and it may be difficult to keep trial pits and, in some cases, boreholes open;• if the lagoons are of high fluidity, then a pontoon or similar supportive equipment willbe required in order to provide a safe working surface (note that the fluidity of acidtars can vary within one lagoon). Surface probing can often be conducted from ahydraulic platform;• the depth of contamination may vary considerably and establishing the base of thelagoon, if this is required, may involve drilling through several non-tarry layers(consisting of, for example, on-site soils, Fuller's Earth and imported soil/wastes).Care must be taken to ensure that the true base of the tar has been reached and thatthere are not further deposits of tar beneath any soil layer (note also that the acid tarmay have migrated up through the soil layer, leading to an intermediate soil layerwithin the lagoon);• attention should be paid to ensuring that any investigation does not lead tocontamination of the underlying groundwater by the acid tar or its components bybreaching low permeability media;• excavated wastes, both solid and liquid, must be disposed of appropriately; and• ideally, site investigations should be carried out during winter months when thematerial is less fluid and the production of hazardous vapours is reduced.R&D <strong>Technical</strong> Report P5-042/TR/04 23
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: 4.2.3 Common mistakesIt is possible
Page 35 and 36: Investigation locations will need t
Page 37 and 38: • gas chromatography by simulatin
Page 39 and 40: 5.2.2 Water environmentThere is lit
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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