austrian guidelines

8/12/2019 Austrian Guidelines

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Recommendations of the AustrianPermanent Seveso Working Group

as a basis to determine appropriate distancesfor the purpose of land-use planning

according to Council Directive 96/82/EC of 9 December 1996on the control of major accident hazards involving dangeroussubstances (Seveso II Directive) as amended by the Directive

2003/105/EC of the European Parliamanet and of the Council of16 December 2003

June 2005


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Editor:

Magistrat LinzUmwelt- und Technik-CenterHauptstrae 1 54041 Linz


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Table of Contents:

Chapter Contents Page

List of Abbreviations 40 Introduction 5

The Austrian Permanent Seveso Working Group 51 The Seveso II - Directive and its Effects on Land-use Planning 61.0 Preamble 61.1 The Provisions of the Directive 71.2 Observations on the Determination of "Appropriate Distances" 102 The Recommendation of the Austrian Permanent Seveso

Working Group12

2.1 Threshold-Quantity-Related Distance Model for Industrialestablishments

12

2.2 StandardisedCase-by-Case Assessment 15Types of Effects for Case-by-Case Assessment 18

2.2.1 Shock wave 18

2.2.2 Thermal radiation 192.2.3 Toxic effects 203 Computational Parameters for Standardised Case-by-Case-

Assessment23

3.1 Source Term Calculation 233.2 Pressure Propagation 233.3 Thermal Radiation 243.3.1 Pool fires 243.3.2 Thermal radiation in case of BLEVE and UVCE 243.4 Dispersion of Toxic Gasses and Vapours 244 References 26

Formatiert

Gelscht: Seitenumbruch


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List of abbreviations:

AEGL Acute Exposure Guideline LevelBLEVE Boiling Liquid Expanding Vapour ExplosionBMLFUW Bundesministerium fr Land- und Forstwirtschaft, Umwelt und

Wasserwirtschaft (= Ministry for Agriculture, Forestry, theEnvironment and Water Management)

BMWA Bundesministerium fr Wirtschaft und Arbeit (=Ministry forEconomy and Labour)

DN Diameter InsideEC European CommunityERPG Emergency Response Planning GuidelinesEU European UnionIDLH Immediately Dangerous to Life or HealthMAC Maximum Allowable ConcentrationMS Member StateFAS sterreichisches Forum Anlagensicherheit (= Austrian

Association for Industrial Safety)RHAD Risk/Hazard Assessment DatabaseTDU Thermal Dose UnitTEEL Temporary Emergency Exposure LimitsUVCE Unconfined Vapour Cloud ExplosionVCI Verband der Chemischen Industrie (Germany; Association of

Chemical Industry)


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0 Introduction

The Austrian Permanent Seveso Working Group

The Austrian Permanent Seveso Working Group (hereinafter referred to as the"Working Group) is a permanent panel of experts, which was constituted in 1992when the Major Accident Ordinance came into force. Since its foundation, the

Working Group has met on a regular basis at least twice a year. Apart from theexchange of experiences among experts on technical-practical as well as legalmatters regarding its implementation in the area of industrial accident law and(industrial) safety technology, its activities also include provision for adequatetraining of the colleagues concerned. To this end, reports and documents arerequested regularly from international and EU bodies which are discussed andconclusions drawn for the Austrian situation. This includes also the invitation ofinternational experts to special seminars. Another important task is the deliberation ofharmonised guidelines for the implementation of the Directive, in particular for theofficially appointed technical experts and, upon request, to offer advice to therespective authorities and ministries.

Since the coming into force of Directive 96/82/EC, the Working Group hasestablished a guideline for inspections according to Art. 18 of the Directive and hasbeen instrumental in elaborating the guideline of the Federal Ministry of Economic

Affairs for the "assessment of safety reports according to Directive 96/82/EC('Seveso II')".The Working Group is composed of representatives of the respective ministries, i.e.the Federal Ministry of Economic Affairs and Labour and the Federal Ministry of

Agriculture and Forestry, Environment and Water Management, delegates from allnine Laender, the cities Linz and Salzburg as well as the official Austrianrepresentative for Directive 96/82/E. Currently, the Working Group is the onlynational body to deal extensively with matters arising from the Seveso II Directive.

Chairman of the Working Group:

Dipl.-Ing. Ernst SimonAmt der Steiermrkischen Landesregierung, Fachabt. 17BAlberstrae 1, 8010 Graz

Head of the Working Group "Reference Scenarios":Dipl.-Ing. Martin SonnleitnerMagistrat Linz, Umwelt- und Technik-CenterHauptstrae 1-5, 4041 Linz

While this document has no legally binding effect on land-use planning, theConference of the Austrian Regional Ministers of the Environment deems the "dualsystem to determine adequate distances" as proposed by the Working Groupsuitable for the consultation procedure to ensure a uniform and practicable approachin Austria until the EU database is available (decision of the Conference of AustrianRegional Ministers of the Environment of 15 and 16 June 2005).


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1 The Seveso II Directive and its Effects on Land-usePlanning

1.0 Preamble

The modelling of the effects of industrial accidents is influenced by a large number ofparameters and assumptions. As a consequence, unacceptable differences in thecalculation of distances for one and the same establishment have been noted.Comparisons made by the Technical Working Group 5, Land-use Planning (TWG 5),throughout the EU have shown differences of between 20 and 1500 m for LPGinstallations and between 200 and 1000 m for ammonia installations. Thesecalculations also reflect the Austrian experience made so far.

Furthermore it is important to point out that several Member States use both thedeterministic and probabilistic approach for determining distances.

For this reason, the Commission was asked to incorporate guidelines concerning thedefinition of a technical database including risk data and risk scenarios in the latest

amendment of SEVESO II.Thus, on a medium-term basis, it to be expected that the probabilistic approach willgain in importance throughout the EU. This trend has prompted the German-speaking Member States in particular to reconsider their deterministic approachchiefly adopted so far. In Germany, the Major Accident Commission is working on apaper which is to provide for adequate distances for new establishments and which isalready based on probabilistic considerations. The German Major AccidentCommission believes that this should also help to avoid the high incidence ofconservative assumptions.

In Austria, recommendations taking into consideration not only deterministic but alsoprobabilistic approaches were elaborated as early as 2002. With the updatecontained in this document, the request put forth to the Working Group by theConference of Austrian Regional Ministers of the Environment has been heeded,which is to discuss anew the matter of "eligible protective measures" and thedetermination and demarcation of risk zones as well as to elaborate proposals. Thisdocument is also intended to avoid a stalemate in the development of land-useplanning, which might occur if the publication of the EU database is waited for.

What is new is the incorporation of a distance model (as discussed in Germany)developed by the Working Group. This model for the determination of adequatedistances largely tallies in the majority of its results with the distances ascertained inthe MIACC Guide (Canada). The MIACC Guide has been used as a benchmarkbecause it has been found to be the only model currently available which has beentested in practice and which has been published (a strong focus on riskconsiderations based on the assumption of a individual fatality risk of 10-6 / yearunderlies this screening tool).

Moreover, as in the past, individual cases may also be considered in exceptionalcases if required, which, according to the present body of scientific knowledge are inline in their methodology with expected EU approaches. Since the assumptions to bemade for the consideration of individual cases are all within the scope of forecasts,this Recommendation also proposes laying down calculation models and parameters


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to achieve standardisation and to prevent undue scattering of results (see Chapter2.2).

What is also new is that this Recommendation is to be employed exclusively as abasis to determine adequate distances for the purpose of land-use planning and nolonger for domino effects and disaster prevention purposes. This is due to the factthat the calculation models as outlined in Chapter 2 neither provide a safe limit nor

are they able to cover all possible accident scenarios. Instead, thisRecommendation, in the long term, is to heed the request to maintain an adequatedistance between industrial establishments and residential areas, public buildings,etc. This approach is also in line with current EU practice.

Since this Recommendation is intended only for the purpose of land-use planning,disaster prevention authorities will now have to base the design of their off-siteemergency plans on considerations of their own, which ideally should includespecifications on appropriate distances as well.

In summary and considering the above, the Working Group decided to revise theRecommendation, issue Nov. 2002 with a focus on the following priorities:

1. Proposal concerning the application of threshold quantity-related distance model

(Chapter 2.1)2. Standardised case-by-case appraisal (Chapter 2.2)

- also taking into consideration active technical protective measures asmitigation measures

- avoiding a high incidence of conservative assumptions

- determining calculation models and parameters.

It is pointed out once again that this first update of the Recommendation by theWorking Group is intended to serve as a practical basis for the determination ofappropriate distances in the current phase. Once the guidelines of the EUCommission have been published, the necessity for a further update, if any, will be

examined.

1.1 The Provisions of the Directive

Directive 96/82/EC (Seveso II- Directive)1 as amended by Directive 2003/105/EC,which replaces Directive 82/501/EEC (Seveso Directive), is intended to preventmajor accidents involving dangerous substances and to limit their consequences forman and the environment2, with a view to ensuring high levels of protectionthroughout the Community. Contrary and complementary to the preceding Directive,it is not only geared to ensure the "technical safety of establishments" and to preventdisasters, but - above all having seen the results of extremely severe industrial

1Directive 96/82/EC of the Council of 9 December 1996 on the control of major-accident hazards involvingdangerous substances (OJ L 10, 13.1.1997, p.1) as amended by Directive 2003/105/EC of the EuropeanParliament and of the Council of 16 December 2003 (OJ L345, 31.12.2003, p. 97.2Cp. Art. 1 of the Directive.


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accidents especially in the 80s, such as in Mxico City in 19843 and in Bhopal in19844- introduces further instruments to attain this goal as far as possible.

One of these instruments is Land-use Planning(Art. 12 of the Directive RL).

The major industrial accident on 21 September 2001 in Toulouse, where theexplosion of huge amounts of ammonium nitrate caused enormous and widespread

damage to industrial establishments, residential areas and urban infrastructure aswell as to schools, hospital and heavily used transport infrastructure5, alerted theinternational and European public yet again to the issue of land-use planning and theincompatibilities arising from industrial areas too close to other areas as well as fromother sensitive uses.

Art. 12 of the Directive contains provisions concerning control on land-use planning6in the vicinity of "Seveso establishments". In the recitals No 4 and 22 of the Directive96/82/EC, explicit mention is made of the importance of maintaining appropriatedistances between "Seveso establishments" and settlements in the vicinity of suchestablishments7. Art. 12 requests that the aim to prevent major accidents and to limittheir consequences be taken into account by the Member States in their land-useplanning policies and other relevant policies8.

It stipulates that in siting new establishments or modifying existing ones, which mayincrease the risk or consequences of major accidents, as well as in case of newdevelopments in the vicinity of existing establishments, such as new transport links,locations frequented by the public and residential areas, appropriatedistances shallmaintained to ensure that the risk of a major accident will not be increased or itsconsequences aggravated9.

The following 4 cases must be distinguished:

3The explosion of an LPG storage tank with a storage capacity of 15 m l with a series of BLEVEs claimedhundreds of lives and left thousands of people injured. Official data on the number of fatalities vary between 600to far beyond one thousand.4This industrial disaster at the Union Carbide plant in the Indian town of Bhopal , during which major quantitiesof methyl isocyanate were released, killed thousands of people and left several thousands more injured orsuffering from the sequelae.530 fatalities, 2500 persons injured, damage at least 1.5 2 bn .The report by the General Inspectorate for theEnvironment of 24 October 2001 is available on the internet at:http://www.ladocfrancaise.gouv.fr/brp/notices/014000809.shtml6 The official German heading of Art. 12 of the Directive berwachung der Ansiedlung is somewhatunfortunate wording. The English text reads Land-use Planning, which - literally translated - meansRaumordnung or. Flchenwidmung in German.7This again refers to the two industrial disasters in Mxico City and Bhopal, where the lack of suitable distancesbetween residential areas and the industrial establishments was to be blamed for the huge number of fatalitiesand people injured or having sustained lasting damage.8Art 12, para.1.9Art 12 para.1 (a and c).


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1 Existing establishment Existing land use No case102 Existing establishment New development in the

vicinitydistances

3 New establishment ofmodification

Existing land use distances

4 New establishment ormodification

New development in thevicinity

distances (rather rare)

Table 1

As far as existing establishments are concerned, additional technical measureshave to be taken so as not to increase the risk to people11, whereby such measurescan be taken on site as well as off site. Art. 12, Para.2 furthermore stipulates thatappropriate consultation procedures be set up to facilitate (concrete) implementation.

Art. 12 reads as follows:

Article 12

Land-use Planning

1. Member States shall ensure that the objectives of preventing major accidents andlimiting the consequences of such accidents are taken into account in their land-usepolicies and/or other relevant policies. They shall pursue those objectives throughcontrols on:

(a) the siting of new establishments,

(b) modifications to existing establishments covered by Article 10,

(c) new developments such as transport links, locations frequented by the public and

residential areas in the vicinity of existing establishments, where the siting ordevelopments are such as to increase the risk or consequences of a major accident.

Member States shall ensure that their land-use and/or other relevant policies and theprocedures for implementing those policies take account of the need, in the longterm, to maintain appropriate distances between establishments covered by thisDirective and residential areas, areas of public use; major transport routes as far aspossible, recreational areas and areas of particular natural sensitivity or interest, and,in the case of existing establishments, of the need for additional technical measuresin accordance with Article 5 so as not to increase the risks to people.

10Protection of vested rights! In this case, other instruments of the Directive have to be employed, such astechnical/management specific measures or provisions of prevention by appropriate (off-site) emergencyplanning.11 Art. 12 Para.1 (b). The case applies if a modification to an existing establishment is planned and if suchmodification increases the risk of an accident while the existing land-use scheme remains unchanged. Moreover,it seems to be increasingly common practice in the EU to reduce appropriate distances by technical measures ofappropriate quality and in sufficient availability (either on site or off site) intended to limit any such accidents intheir consequences and impact.


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1a. The Commission is invited by 31 December 2006, in close co-operation with theMember States, to draw up guidelines defining a technical database including riskdata and risk scenarios, to be used for assessing the compatibility between theestablishments covered by this Directive and the areas described in paragraph 1.The definition of this database shall, as far as possible, take account of theevaluations made by the competent authorities, the information obtained fromoperators and all other relevant information such as the socio-economic benefits of

development and the mitigating effects of emergency plans.

2. Member States shall ensure that all competent authorities and planning authoritiesresponsible for decisions in this area set up appropriate consultation procedures tofacilitate implementation of the policies established under paragraph 1. Theprocedures shall be designed to ensure that technical advice on the risks arising fromthe establishment is available, either on a case-by-case or on a generic basis, whendecisions are taken.

1.2 Observations on the Determination of "Appropriate Distances"

The only basis available so far in Austria to determine appropriate distances to/from"Seveso establishments" were reference scenarios coupled with dispersion models(mainly for pressure, thermal radiation and toxic gases) and acceptance criteria (endpoints). The preparation and calculation of such scenarios, in particular for severeaccidents involving dangerous substances, had no tradition in Austria prior to theenforcement of the Seveso II Directive. Thus it was and is still necessary to resort toEU and international experience.

Within the Community but also in other countries12 longer traditions existed withregard to the determination of distances to/from "Seveso establishments", with twotrends being chiefly pursued. The "determinists" select certain scenarios andevaluate their consequences13. The "probabilists" determine the (arithmetic)probability of a specific accident or of the extent of damage14,15. Apart from these,

there are hybrid approaches composed of both trends. However, it is most likelythat the probabilistic approach will prevail in the end.16

At any rate, in order to comply with the requirements of Art. 12 of the Directive, areasonable approach towards planning and decision-making had to be sought. TheWorking Group took this issue on board in the wake of an expert seminar held by the

Austrian Forum for the Safety of Installations (FAS)17 in April 1996. Apart frominternal discussions among experts and calculations based on international technical

12E.g.. Canada, Major Industrial Accidents Council of Canada (MIACC): Risk Assessment Guidelines forMunicipalities and Industries. An Initial Screening Tool. Major Industrial Accidents Council of Canada 1997(MIACC-Guide)13For instance in France. First attempts also in Germany.14For instance in the United Kingdom, the Netherlands and Canada15A good survey on the approaches adopted by the (then 12) Member States is given by C. Hamilton, R. de Cort,K. O. Donnel (HSE): Report on Land Use Planning Controls for Major Hazard Installations in the EuropeanUnion. Ed.. CDICR-Ispra, 1990. EUR 15700 EN. For definitions on deterministic and probabilistic approachescp. Hamilton et al. aaO, 10.16 See amendment of Directive 96/82/EC by Directive 2003/105/EC; Article 12 Para. 1a.17AFS is the Austrian association of officially appointed experts dealing with safety technology matters andindustrial accident law.


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literature, two studies were commissioned, based on which the decision for theoriginal Recommendation was taken. These studies are:

- H. Koinig, Reference Scenarios according to Directive 96/82/EC, Final Report,Vienna 1999, commissioned by the Federal Ministry of Agriculture, Forestry,Environment and Water Management, and

- R. Pischinger, P. Sturm et al., Reference Scenarios "Dispersion of Toxic

Gases" for the Purpose of Land-use Planning according to Art. 12 of theSeveso II Directive", Graz, 2000; commissioned by the Laender Carinthia,Salzburg, Styria, Tyrol, Vorarlberg and Vienna and the City of Linz.

A fundamental decision was then taken to chose the deterministic approach and thusto base calculations largely on worst case scenarios. The use of a probabilisticapproach, namely databases concerning the probable failure rate of componentsetc., did not appear to be meaningful at that time since the Working Group did notbelieve that the data material then available were sufficiently reliable.Finally, in November 2002, the Recommendation of the Austrian Seveso WorkingGroup for the Calculation of Appropriate Distances for the Purpose of Land-usePlanning, Emergency Planning and Domino Effects was published.Meanwhile the general view has gained acceptance throughout the EU that referencescenarios in the context of appropriate distances are not to be equated with worst-case scenarios for the purpose of emergency planning. As a consequence and quitecorrectly, the trend when designing such scenarios is to use risk data (riskscenarios). To date, there are still too few reliable data available so that the EUCommission will draw up at least guidelines on the definition of a technical database(RHAD) by 31 December 200618.In view of the greatly differing nature of industrial installations and the required effort,it remains to be seen whether - in analogy to the risk assessment of nuclear powerplants - a purely probabilistic approach will be widely accepted. Currently, a kind of"mixed from" appears to be a likely solution, meaning that quasi-deterministicapproaches are backed by risk considerations (e.g. the as yet unpublishedrecommendations of SFK/TAA Working Group "Monitoring of Land-use Planning in

Germany" or the MIACC-Guide12

). Considering all these facts and circumstances, theWorking Group has agreed to adapt the Recommendation in a first update so as totake account of this development and, in particular, of the discussion throughout theEU as it stands today. Once the RHAD has been published, the need for a furtherupdate will be examined.The following proposals and suggested modes of calculation are also to be seenagainst this background.

The recommendations given below are intended to assist the competent authoritiesin the consultation procedure to be set up19in determining appropriate distances bybalancing the interests between the need to protect the population and to safeguardeconomic and settlement development.

18Article 12 Para.1a.19Article 12 Para.2.


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2 The Recommendation of the Austrian PermanentSeveso Working Group

In view of the lack of a binding definition of "appropriate distance", the Working Grouphas based its Recommendation on the following assumptions:The appropriate distance-

is one of several instruments to reduce the risk to the neighbourhood;- is unable to prevent all possible consequences of industrial accidents inneighbouring zones lying outside the distance;

- is not a safe limit;- is laid down to achieve, on a long-term basis, a separation between industrial

zones and sensitive areas;- should, ultimately, be a political consensus and the result of balancing a great

number of interests, inter alia, the interest between industry and labour on the onehand and between the need of protecting the neighbour on the other.

2.1 Threshold-Quantity-Related Distance Model for IndustrialEstablishments

The best-suited model to provide a uniform basis for the consultation procedure todetermine appropriate distances, especially for newly planned establishments butalso for existing Seveso establishments, is the threshold-quantity-related distancemodel. This model presupposes that the establishment is a state-of-the-artinstallation.

The model is based on the following framework conditions:- a distance of 100m if the lower threshold quantity is reached;- a distance of 300 m if the upper threshold quantity is reached; and- a distance of approx. 1000m if the 100-fold upper threshold quantity is reached;- linear interpolation is applied up to the upper threshold quantity; a logarithmic

approach is adopted for values above.

The distance model is described by the following formula:

For 11


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))1(9

21(

10 +=

=

n

i Li

ia

Q

qrD and

=

=n

i Ui

ia

Q

qrD

103 resp.

applies, with the larger distance being the applicable one.

For 11

=

n

i Ui

i

Q

qthe following applies:

aD distance proposed for the consultation procedure to determine the appropriate

distance [m]

0r specified to be 100 m

iq quantity of dangerous substance [ t ]

n number of dangerous substances or categories of substances present in theestablishment or installation in question. The Directives summation rules areto be observed.

LiQ threshold quantity column 2 [ t ]

UiQ threshold quantity column 3 [ t ]If no LiQ is specified in the Directive, UiLi QQ = .

as

qi/Qi13 10

100

300

Figure: Example for possible curve patterns in the thresholdquantity-related distance model


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Account is to be taken of all dangerous substances which may be present in anestablishment or installation within the meaning of Article 3, Para. 2 of the Directivewhereby these substances are classified in groups or categories according to thesummation rule pursuant to Annex I, Part 2 of the Directive. For each of these groupsor categories of substances, the distance for this establishment or installation is to becalculated, whereby the largest distance shall apply.

These formulae are mathematical models, which like the Risk AssessmentGuidelines for Municipalities and Industries, Edition 1997 (MIACC-Guide) use alogarithmic approach for the risk to be calculated. However, contrary to the MIACC-Guide, these formulae are applicable to all substances and categories of substanceslisted in the Directive.

The formulae are based solely on the threshold quantities as specified in theDirective and the quantities present in the establishment or installation. They thusrepresent the potential hazard of a substance in analogy to the Directive.

In many cases, the distances as determined by the formula correspond, by and large,to the distances proposed in the guidelines and commonly adhered to in the EUMember States.By using the distance formulae, uncertainties concerning the assumptions andparameters to be chosen for the calculation are avoided. Another advantage is that,by adopting this approach, uniform distances are laid down throughout Austria forestablishments having the same quantities of substances present.The calculated distance is to be maintained for each establishment pursuant to

Article 3 (2) of the Directive starting from the area within an establishment in whichthe major technical units together with the respective substances are located.

Examples of calculations:

Part/no. Substance Qualifying

(threshold)quantities [t]

Quantity [t] Distance [m]

1/6 chlorine 10 / 25 100 4401/14 LPG/natural gas 50 / 200 100

1,000150460

1/18 methanol 500 / 5,000 1,000 1201/30 petroleum products 2,500 / 25,000 100,000 4402/1 Very toxic

substances5 / 20 5

50100390

2/2 ammonia 50 / 200 10010,000

150690

2/2 toxic substances 50 / 200 1001,000

150460

2/8 Extremely flammableliquids R11

5,000 / 50,000 10,000100,000

120370


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2.2 Standardised Case-by-Case assessment

Distances must normally not fall short of the distances as determined according to2.1. Exceptions may be granted in the case of existing establishments if it can beproved that additional (technical) measures or measures beyond the state of the artwhich warrant a reduction of the distance have been taken, whereby other specificlocal conditions may also be taken into consideration.

These case-by-case assessments are to be based on the conditions and modes ofcalculation specified below (see also Chapter 3).

Immission guidance values for standardised case-by-case assessments:

Table 2:Substance Scenario Impact Assessment value

liquefied flammablegases

BLEVE, UVCE a) shock waveb) thermal

radiation

a) 0.050 barb) 500 TDU for thedynamic-thermalassessment ashort-term impact

of


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To obtain, as far as possible, uniform results, the following boundaryconditions were laid down by the Working Group:

1. The scenarios listed above shall apply to technical installations in whichdangerous substances may be present and if these are applicable for thedetermination of distances. Account shall also be taken of installations using,handling or storing dangerous substances which have not led to the

classification as Seveso establishments

2. Missiles will generally only have spot character in their effect (contrary toexplosions, toxic gas clouds and the like) and shall not be taken into account.However, there may be cases where their inclusion may be justified (e.g.storage of gas bottles, acetylene).

3. Containment measures shall, as a matter of principle, be passive safetymeasures. Passive safety measures include, inter alia, retention pools andsimilar retention systems, shock-proof design of the enclosure, encasements,fire-protective coatings, earth dams and ramparts, precautions against pipefractures, check valves, bursting disks.Containment measures in the form of active safety measures24may be eligible ifproof can be furnished of their sufficient availability. This is the case, forinstance, if a redundant design of the containment device exists and a fail-safe design thereof exists25.

4. The scenarios listed in Table 2 shall be applicable to transport vehicles onlyinasmuch as their operation is connected directly with the activity of theestablishment. This is the case, for instance, during loading or unloadingoperations or if these vessels or vehicles are used as a means of storage (84bTrade Regulation Act). On-site transportation by vessels / vehicles is excludeduntil the loading / unloading facility.

5. The failure of a pressurised vessel under thermal impact need not be taken intoaccount if eligible safety measure are in place (Point 3) or if safety distancescalculated according to "Druckbehlteraufstellungsverordnung" (AustrianOrdinance concerning the installation of pressurised vessels) are maintained,provided these safety measures are able to prevent an exposure of thesevessels to unduly high thermal radiation or an unduly high rise of pressure inthese vessels. For rail tankers and road tankers, the special case appliesinasmuch as these containers do not possess safety valves and that thereforethe permissible heat radiation to which they may be exposed is accordingly lowFor temporary fire loads (e.g. motor vehicles), the appropriate distance shall bedetermined by calculation, whereby the minimum distance as laid down in the"Druckbehlteraufstellungsverordnung"is 5 m.Spontaneous failure and auto-ignition of transport vehicles are events which donot fall under the requirements of "appropriate distances".

242 (9) Industrial Accident Ordinance, Austrian Federal Law Gazette 354/2002 of 27 November 200225Note: The Working Group had initially intended to take over the definitions of the IEC 61511 "FunctionalSafety - Safety Systems for the Process Industry " for their own definition of active safety measures. However, inview of the lack of experience in dealing with this standard and due to the lack of data, it refrained from doingso.


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6. In cases where a BLEVE has not to be taken into account due to the presenceof passive safety devices (Point 3), a UVCE is to be calculated, as in cases ofexplosive gas/vapour clouds.

7. For diameters larger than DN 250, a leakage corresponding to DN 250 isassumed.26.

8. In case of an UVCE, an intervention time of 10 min is assumed. For determiningthe effect of the UVCE, the amount of gas released within 60 sec shall be takeninto account, whereby ignition is assumed to have taken place at the point ofrelease27. The damming factor shall be determined on a case-by-case basis.

9. For liquid and solid oxidising substances an examination shall take place ifscenarios or effects as listed in Table 2 are possible. These shall then beconsidered in analogy.

10. For substances dangerous to the environment no scenario is usually relevant forthe purpose of land-use planning unless these substances possess otherdangerous properties.

11. Conflagration gases are not specific to Seveso establishments and are thereforenot considered when determining appropriate distances (see Chapter 3.3). Ifrequired, their effect may be considered in emergency planning.

12. There may also be other scenarios (e.g. continuous exothermal reactions).

13. The distance shall be determined from the source.

14. For installations with toxic or carcinogenic substances for which no assessmentvalue is specified, a standardised case-by-case approach is not possible.

26This "limit diameter" is based on the result of the ENCONET Study according to which 96% of all pipefractures occur in pipes of a diameter of up to DN 250.27Cp.: Scnario B: UVCE in: Secrtariat dEtat auprs du Premier ministre charg de lEnvironnement et de laPrvention des risques technologiques et naturels majeurs DEPPR Service de lEnvironnement industriel(Ed), Maitrise de lUrbanisation autour des Sites Industriels Haut Risque, Paris, October 1990, p 30f.


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Types of Effects for Case-by-Case Assessment

2.2.1 Shock wave

For land-use planning purposes a threshold value of 50 - 70 mbar (irreversibledamage to humans) has been laid down internationally for the surroundings.Considering the instantaneous effect of such shock waves which make escape

impossible, the Working Group proposes a value of 50 mbar.

Examples28:

Overpressure(mbar)

Effects on humans

6 hurricane with wind force 1210 a blast of wind knocks down persons standing30 slight injuries caused by glass fragments70 no injuries in open terrain

80 90 a blast of wind sweeps away persons lying (360 km/h)170 1% rupture of the ear drum300 fatalities and injuries within collapsing buildings480 70% fatalities and injuries in the open2000 99% lung rupture

Effects on buildings and installations (parts thereof)

2 breakage of large window panes possible10 standard value for window breakages30 confined structural damage50 minor structural damage to buildings60 99% of all window panes break70 partial destruction of buildings, danger of collapse

170 50% walls of buildings damaged210-280 destruction of light constructions, rupture of empty crude oil tanks340-410 total destruction of buildings

28Cp. Damage Assessment, Department of the Interior of the Canton of Zurich, Emergency Response Co-ordination Centre, Zurich, June 1992.


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2.2.2 Thermal radiation

For land-use planning purposes a threshold of 3 - 5 kW/m (irreversible damage tohumans) has been laid down internationally. Considering that an escape will not bepossible equally for all persons, the Working Group proposes a value of 3.0 kW/mand of 500 TDU for short-term impacts.

Examples29

:

Thermal radiation(kW/m)

Effect on humans

1 maximum solar irradiation1.5 no adverse effects even with longer exposure4.5 formation of blisters after 20 sec.

12.5 first-degree burns after 10 sec.36 third-degree burns after 10 sec.

Effects on emergency-response teams

4.5 fire-fighting action without cooled fire-fighting suits8 short-term fire fighting action with cooled fire-fighting suits

12.5 If cooled, tanks are not damaged36 tanks are damaged in spite of cooling

Effects on constructions and installations (parts thereof)

2 destruction of varnish surfaces on timber after 30 min.3 destruction of synthetic surfaces after approx. 30 min.

4.5 ignition of felt roofing upon flame contact12.5 bursting of glass panes after 10 min.25 ignition of timber without flame contact30 deformation of steel profiles after 30 min.

100 ignition of roof insulation covered with aluminium plates,failure of load-bearing steel profiles after 20 min.

29Cp. Damage Assessment, Department of the Interior of the Canton of Zurich, Emergency Response Co-ordination Centre, Zurich, June 1992


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2.2.3 Toxic effects

The assessment of the immission load caused by an accidental release of toxicsubstances shall be based on the consideration when determining the threshold thatthis is an extremely rare event and, if occurring, of short-term impact only. This is whythresholds are applied assuming an impact of 30 60 minutes in duration. Theapplication of MAK values, which are geared to frequent and long-term exposure, are

not suitable at all.

IDLH values (Immediately Dangerous to Life or Health)is a concentration at which escape is possible within 30 minutes without causingirreversible damage to health even without breathing equipment.

ERPG values (Emergency Response Planning Guidelines)

ERPG 1is assumed to be the maximum airborne concentration to which almost all individualsmay be exposed for up to one hour without sustaining more than mild, transientdamage to health or perceiving a clearly defined objectionable odour.

ERPG 2is assumed to be the maximum airborne concentration to which almost all personsmay be exposed for up to one hour without sustaining or developing irreversible orother serious damage to health or symptoms which might impair a persons ability totake protective measures.

ERPG 3is assumed to be the maximum airborne concentration to which, if not exceeded,almost all individuals may be exposed for up to one hour without sustaining ordeveloping life-threatening damage to health.

AEGL values (Acute Exposure Guideline Levels)

AEGL 1is the airborne concentration of substances (expressed in ppm or mg/l) at which, ifexceeded, the population at large including sensitive but excluding hypersensitiveindividuals may experience perceptible indisposition. Airborne concentrations ofsubstances below the AEGL 1 represent exposure levels which may be slightlyirritant to the sense of odour, taste or other senses.

AEGL 2is the airborne concentration of substances (expressed in ppm or mg/l) at which, ifexceeded, the general population including sensitive but excluding hypersensitiveindividuals may sustain irreversible or other serious long-term damage includingdamage which might impair a persons ability to escape. Airborne concentrations of

substances below the AEGL 2 value but above the AEGL 1 represent exposurelevels which may cause perceptible indisposition.

AEGL 3is the airborne concentration of substances (expressed in ppm or mg/1) at which, ifexceeded, the population at large including sensitive but excluding hypersensitivepersons may sustain life-threatening damage or perish. Airborne concentrations of


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substances below the AEGL 3 value but above the AEGL 2 value represent exposurelevels which may cause irreversible or other serious long-term damage includingdamage which may impair a persons ability to escape.

TEEL values (Temporary Emergency Exposure Limits)

TEEL 0

is the threshold concentration below which most people will experience no adversehealth effects.

TEEL 1is assumed to be the maximum airborne concentration to which almost all individualsmay be exposed up for one hour without sustaining more than mild, transientdamage to health or perceiving a clearly defined objectionable odour.

TEEL 2is assumed to be the maximum airborne concentration to which, if not exceeded,almost all individuals may be exposed for up to one hour without experiencing ordeveloping irreversible or other serious health effects or symptoms that could impairan individuals ability to take protective action.

TEEL 3is assumed to be the maximum airborne concentration to which, if not exceeded,almost all individuals may be exposed for up to 1 hour without sustaining ordeveloping lifethreatening damage.

In Austria, the IDLH value is favoured by the Working Group. However, changes areforeseeable. The US Environmental Protection Agency together with several MemberStates are elaborating and jointly publishing threshold values (AEGL AcuteExposure Guideline Level) which, once accorded internationally, might becomeapplicable. In the Risk/Hazard Assessment Database (RHAD), which is in themaking, the European Commission is expected to propose AEGL2 and AEGL3 for

the two-zone model, if not available, ERPG2 and ERPG3. Similarly to the US AEGLvalues, so-called AETL values (Acute Exposure Threshold Levels) are currentlybeing prepared at European level for 21 different substances. These values mightalso be incorporated into the RHAD.


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Comparison Toxicity DataSub-

stance IDLH ERPG (60 min) AEGL (30 and 60 minresp.) MAC2003(30

min) ERPG2 ERPG3 publ. AEGL2 (30) AEGL2 (60) AEGL3 (30) AEGL3 (60) Status** Mv*** Sv***NH3 300 150 750 2000 160 110 1600 1200 int. 20 50

SO2 100 3 15 1989 1 1 32 27 prop. 2 4

Cl 10 3 20 1988 2.8 2 28 20 int. 0.5 0.5

HF 302050

(10min)

50170 (10

min)

19971999

34 24 62 44 int. 1.8 3

H2S 100 30 100 1991 32 27 59 50 int. 10 10

Acrolein 2 0.5 3 1989 0.18 0.1 2.5 1.4 prop. 0.1 0.1

Br 3 0.5 5 2001 0.33 0.24 12 8.5 prop. 0.1 0.1POCl3 - 0.5* 3* ? - - 1.1 0.85 int. 0.2 0.8

PCl3 25 3* 15* ? 2.5 2 7 5.6 int. 0.25 0.5

BF3 25 10 33 1999 6.2 3.1 27 14 int. 1 1

CS2 500 50 500 2002 200 160 600 480 prop. 10 40

TDI 2.5 0.15 0.6 2002 0.17 0.083 0.65 0.51 int.0.00

50.02

Styrol 700 250 1000 1995 160 130 1900 1100 prop. 20 80

Remarks:

all values in ppmMAC maximum allowable concentration* TEEL values** int. = interim, prop. = proposed*** Mv = daily mean value, Sv short-term value/instantaneous valueIDLH unchanged at least since 1996

Calculation modelFor the scenario "dispersion of toxic gases", the choice of the calculation model isessential when determining the appropriate distance. To investigate this further, astudy was commissioned by the Austrian Laender of Carinthia, Styria and Salzburgto Graz University of Technology, which screened the large number of programmesavailable on the market and evaluated them on the basis of certain criteria. As a

result of this study, the following computational programmes were recommended:TSCREEN, SLAB, RMP, ALOHA (CAMEO), HGSYSTEM .Other models, such as Effects/TNO, MET-Model, VDI, etc. may be employed as well.However, it has to be borne in mind, that the result may vary quite considerably fromprogramme to programme for the same task. The Working Group believes thatconsiderable efforts still have to be invested in this respect to achieve internationalharmonisation.


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3.3 Thermal Radiation

3.3.1 Pool fires

Almost all hydrocarbons generate considerable smoke if burnt in extensive pools.The use of the model according to Schnbucher/Gck30is recommended. No smokeor little smoke develops if methanol, ethanol, acetaldehyde and other comparable

liquids (C-H-O compounds) are burnt. The heat radiated by fires of this kind can bederived from the Stefan-Boltzmann Law. However, it has to be borne in mind that theflame temperature has to be considered to the power of 4 in the calculation and thatthe emission factor has a major influence as well.

Other parameters:- transmission coefficient = 1 (conservative; attenuation due to air humidity and

carbon dioxide as well as the influence of wind are not considered)- convection should be considered only in case of direct flame contact in

buildings; convection increases the result of thermal radiation by some 20%.

As regards conflagration gases, see Point 3.4.

3.3.2 Thermal radiation in case of BLEVE and UVCE

When assessing the thermal radiation from unconfined vapour cloud explosions(UVCE) or boiling liquid expanding vapour explosion (BLEVE), the method accordingto Hymes31may be applied. A value of 30 - 40% without atmospheric attenuation isrecommended.

3.4 Dispersion of Toxic Gasses and Vapours

Physical dispersion of the various substances always differs widely and is verycomplex. It depends on a number of factors such as density, temperature,

turbulence, etc. Moreover, local meteorological conditions (wind direction, windspeed, temperature gradient, heat of ground, roughness, air humidity, vertical mixing,solar irradiation, ....) are difficult to capture. In addition, dispersion in close proximityto the source of emission is heavily influenced by the type of source (point/areasource), the source altitude as well as by the topography and building structure.Users and commissioning authorities, therefore, have to bear in mind thatcomputational models are merely able to predict roughly the potential effects and thatthe results may vary considerably depending on the meteorological conditions.

The Working Group, therefore, recommends the use of "standardised averagedispersion conditions". These are applied in several other European countries as well(e.g. "Guide to hazardous industrial activities", Netherlands).These dispersion conditions are based on Class D according to Pasquill/Gifford orClass 5 according to Turner/Reuter without considering inversion.

Ambient temperature is assumed to be 20C and wind velocity 2 m/s at 3 m heightwithout considering the distribution of wind direction. As regards surface roughness,

30is included in various commercially available programme packages.31is included in various commercially available programme packages


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values reflecting the actual situation are to be used. Further default parameters are50% cloudiness and 50% relative air humidity.

In case of fire, apart from the spread of thermal radiation, the spread of hazardoussubstances present in the conflagration gasses is frequently of interest. Thepropagation of hazardous substances in the conflagration gasses can be neglectedin many cases where the fire has developed fully and sufficient oxygen is supplied

due to the strong uplift caused by the high heat release, which dilutes hazardoussubstances in the conflagration gasses close to the ground to non-dangerouslevels32.

32quoted from the UFO scheme, see Chapter 4.


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4 References

The references quoted below do not claim to represent the complete internationaland EU literature available on this subject. Only references used, inter alia, by theWorking Group are cited.

EU:

ISIS (Ed) Guidance on Land Use Planning As Required By Council Directive96/82/EC (Seveso II), Report No EUR 18695 EN, Ispra 1999 (may also bedownloaded from the JRCs website in Ispra: http://mahb.jrc.it).

Other MS and European States:

Secrtariat dEtat auprs du Premier ministre charg de lEnvironnement et dela Prvention des risques technologiques et naturels majeurs DEPPR Service de lEnvironnement industriel (Ed), Maitrise de lUrbanisation autour desSites Industriels Haut Risque, Paris, October 1990.

Direktion des Inneren des Kantons Zrich, Koordinationsstelle fr Strfall-vorsorge, Schadenausma-Einschtzung, Zurich, June 1992.

Austria:

H. Koinig, Referenzszenarien zur RL 96/82/EG, Endbericht, Wien 1999,commissioned by the Austrian Federal Ministry of Agriculture, Forestry,Environment and Water Management.

R. Pischinger, P. Sturm et al., Referenzszenario "Ausbreitung toxischer Gasefr Zwecke der Raumordnung/Flchenwidmung nach Art. 12 der "Seveso II-RL, Graz, 2000; commissioned by the Laender of Carinthia, Salzburg, Styria,

Tyrol, Vorarlberg and Vienna, and the City of Linz.

USA:

Primary and secondary information sources for the SLAB-Database (ENCONETStudy).

Canada:

Risk Assessment Guidelines for Municipalities and Industries. An InitialScreening Tool. Major Industrial Accidents Council of Canada 1997 (MIACC-Guide).


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austrian guidelines

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