/ Centro Colaborador OPS/OMS en Mitigación de Desastres en Establecimientos de Salud
Universidad de Chile / /

Chapter III

General Criteria for SelectingaSafe Site

1Introduction

Theidentityofsiting optionsandthe selectionofthe definitive siteforthe facilitymust be based on an assessment ofthehealthcare needs ofthepopulationandthecharacteristics oftheexisting health network. The choice of site will also be affected by public health policies and any demographic, geographical, sociopoliticalor economiccriteria set bythe institution. Other important considerations are the performance objectives sought forthe facilityat normal timesandduring emergencies, thecomparative analysisofthenaturaland technological hazardspresentat the various potential sites, theestimatedcost andtechnical feasibilityof implementingthenecessaryprotection systems, theeconomic resourcesavailable,andthefindings of the cost/benefitanalysis oftheoptions as illustrated in Flowcharts 2 and 3.

This assessment mustcovernot onlythe specificsites butalsotheirsurroundings. The way in whichnatural phenomenaaffectthesurrounding population, thepopulationof referenceandthe infrastructure must be evaluated, particularly their impact on lifelines and access roads.

Flow chart 2

Site preselection

Flow chart 3

Site selection

2Processfor selecting siting options

2.1Variables ofsite selection

It is not the purpose of this handbookto show in detail how to rank thevarious siting options. Instead,relevantcriteria will be mentioned, such as the key factors that must betaken into account when selecting anadequateandsafe location. It isadvisable that the Institution define qualitativeandquantitativespecifications for assessing and comparing each ofthesiting options. Thesespecificationsmay be of varying degrees of complexity. What matters is that they facilitate the decision-making process by testing each site’s capacityto meetthe desiredperformance objective.If none of thesiting optionscan meet it, it will benecessaryto select a less ambitious performance objective—orcontinue searching for acceptable siting options.

All the informationon local risks that may be needed forchoosing thesiting optionsmight be limitedtoexistingdata found in land-use managementplans, localorregional development plans, technical reports, local zoning lawsandregulations, or the opinionsofexperts. Even so, on-site inspection of each of the options and their surroundings should be carried out by the Assessment and Selection Team.If thehealth facilitywill be designedto meet ahigh performance objective, however, detailed studiesmust be carried out to characterizetheprevailing hazards. No siteshould be selected if any of the detailed informationrequired is lacking.

Inselecting the site,moreover,one must consider theproximity tocertain industrial facilities (chemical plants, refineries, mining processingplants, etc.), military facilities, landfills, airports, routes used forthetransportofhazardous materials, and so on, facilities that—because of theiroperations, the emissionoftoxic agents, or the possibility of eventualaccidentsat normal timesorduring an emergency—might affectthesafetyof the contemplated health facility.

An aspect worthconsideringisthefeasibility of having thelocal regulatory planmodified in such a way that no activitiescan be carried out in the future that endangerthe hospital andits operations.

2.2Site selection procedures

The selectionof the siteinvolves threestages, each with its own activitiesor substages.

Stage 1:Compilationofbackground data

Stage 2:Assessmentofsiting options

Stage 3: Site selection

2.2.1Stage 1:Compilationofbackground data

2.2.1.1Preliminary studies

When the different siting options have been selected by the Client Institution,it will be necessary to evaluate any background data available concerning each of the options. The team in charge of site selection mustdetermine whether theavailable data aresufficientormore informationis required in order to compare the various options and select the definitive site. Table 10 lists some of theactivitiesthat should be carried outat thisstage.

Table 10
Preliminary activities
Selection ofprofessional team (see Chapter V)
Definitionofprotection objectivesandexpected level of damage
Definitionofsiting options
Delimitationoftheboundaries within which the potential sites would be located
Area to be occupied bythe facility
Area of influence
Roads
Lifelines
Review oflocal regulatory plans
Preliminary studies
Human settlements and infrastructureintheregion
Inhabited area
Services
Roads and available forms oftransportation
Review ofexisting lawsandregulations
Review ofregional development plans
Review ofexisting cartography
Reviewof general information regarding thesites ofinterest and their surroundings
Review ofbackground data regarding adverse natural phenomenathat have taken place intheregion,such as landslides or mudslides, strong winds, floods, seismic events or volcanic eruptions
Compilationofpreliminary geotechnical data regarding the potential sites
Compilationof informationgathered for otherprojects that have been developedinthearea
Opinionofgovernmentbodies andNGOs
Opinionofexperts

At thisstage, theteam of specialistsparticipating in the project must estimatethe probability of occurrence ofthe various natural phenomenaconsideredinthis handbook. Thisisnecessaryin order to definethelevelofdetailofthestudiesrequiredto characterizethehazards inthe siteschosen. In case not enough informationis available, orthere are doubts regardingthat information, theteam of specialistsmustinform theProject Director andCoordination Team and recommend which studiesare needed to characterize theprevailing hazards oneach site. Thelevelofdetailof thestudieswill also be determined, naturally, by theperformance objective chosen forthe facility (see Table 8).

2.2.1.2Studiesrequiredforassessingthe risks prevalent in each of thesiting options

At the beginning ofthisstage, theteam of specialistsmustevaluate if the informationcompiledduringthepreliminarystageissufficientto preselect the best potential sitesforthe facility. If it is, the next step is to carry out a closer evaluation ofthesiting options, as discussed further on inthischapter. If the informationrequired is not available, theteam of specialistsmust carry outall studiesnecessary for producing the informationthat will characterizethehazards prevalent in each site. An example ofthetypes of studiesrequiredcan be found inAnnexA.

2.2.2Stage 2: Assessmentofthesiting options

2.2.2.1Processingthe data

The informationcompiledduringthepreliminary studies, or that obtainedlater as needed, must beprocessedin order to characterizethehazards and level of risk at each of thesiting options. Flow chart 4 summarizesthemain variables that must bequantifiedin order to determine thenatural hazardsprevalent at eachsite.

Flow chart 4

Quantificationof theRisk

To obtaintheresultssummarizedinthechartabove thetasksspecifiedintables 11a through 11f must be carried out.

Table 11a
Assessmentof landslide risk
Assessment of conditions for the occurrence of alandslide
Historical background
Vegetation
Geological conditions
Natural strata
Topographical conditions
Steepness of slopes
Geomechanical conditions
Stratigraphic sections
Strataoflowcohesion and lowshear-strength soil
Soil and rock degradation
Watercourse-related hazards (destabilization)
Seismic hazard
Human intervention
Assessmentofslope stability
Preliminary assessment
Detailed assessment
Dimensionsof therisk of landslides
Surfaceaffectedandvolume displaced
Velocity of thelandslide
Safety factors
Likelihood
Productionoflandslide risk maps (microzoning)
Table 11b
Assessmentof mudslide risk
Assessment of conditions for the occurrence of mudslides
Historical background
Meteorological conditions
Vegetation
Geological conditions
Naturally unstable strata
Topographical conditions
Steepness of slopes
Geomechanical conditions
Stratigraphic sections
Low-cohesion soil with low shear strength
Soil and rock degradation
Drainageand permeability
Human intervention
Dimensionsof therisk ofmudslides
Surfaceaffectedandvolumeof material displaced
Mudslide speed
Likelihood
Productionofmudslide risk maps (microzoning)
Table 11c
Assessmentof therisk of strong winds
Assessment of conditions for the occurrence of strong winds
Historical background
Meteorological conditions
Topographical conditions
Dimensionsof therisk ofstrong winds
Wind speed
Likelihood
Productionofwind speed maps (microzoning)
Table 11d
Assessmentof flood risk
Assessment of conditions for the occurrence of floods
Historical background
Meteorological conditions
Existenceofwatercoursesinthearea
Topographical conditions (low-lying areas)
Permeability anduseof thesoil
Riskoffloodby tsunami
Human intervention
Identityofcritical points – Calculationofhydraulic axes
Identityofcritical overflow pointsduringfloods
Dimensionsof therisk offlooding
Surfaceaffected
Heightofflood water level
Flow speed
Likelihood
Productionofflood risk maps (microzoning)
Table 11e
Assessmentof seismic risk
Characterizationofseismogenic conditions
Establishment offrequency-magnitude ratios
Estimationof themaximum probable seismic event
Estimationof seismic risk
Probabilistic seismic hazard analysis
Definitionofattenuation factors
Estimationofthe duration of strong ground motion
Estimationof thepredominant periodof ground motion
Deterministic seismic hazard analysis
Dimensionsof theseismic risk
Linear response spectrum
Foundation-soil liquefaction potential
Likelihood of massive landslide (See section on landslides)
Likelihoodoftsunamis (See section on floods)
Productionofseismic risk mapsfor each of thesiting options
Table 11f
Assessmentof volcanic risk
Assessmentoflikelihood ofvolcanic activity
Likelihood oflateral explosions
Likelihood ofbeing in the path of pyroclastic flows
Likelihood ofbeing in the path of lava flows
Likelihood of massive landslides
Likelihoodofmudslides
Likelihoodof contaminationby gases andashes
Likelihoodofsolid and particulate matter emissions
Likelihoodoftsunamis
Dimensionsof therisk ofvolcanic activity
Surfaceaffected (areaof influenceofvolcanic action)
Velocity oftheflows
Degree of toxicity of gases emitted
Magnitudeofrelated ground motion
Characterizationof probablemudslides (See sectionon mudslides)
Characterizationof probablefloodsdue to tsunamis(See sectionon floods)
Likelihood
Productionofvolcanic risk maps (microzoning)

2.2.2.2Technical and economic feasibilityof protectionsystems

In the case of eachlikely natural hazard, thetechnical and economic feasibilityof implementingoverall protection systemsfor thestructurethroughtheexecutionofperipheral worksand other actions must be evaluated. Thefollowingtable lists some of these actions.

Table 12

Actions that can assist in the overall protection of the facility

Strategies for protectionagainstlandslidesandmudslides
Slope stabilization
Soil stabilization throughthe use of geotextiles
Knocking down unstable masses
Reforestation
Cleaningnaturalwatercourses,canals
Constructionofdrainage facilities
Constructionofalluvial terraces
Constant monitoring (instrumentation); early warning systems
Strategies for protectionagainststrong winds
Production of technical detailing specifications
Reforestation
Permanent monitoring ofmeteorological conditions;early warning systems
Strategies for flood protection
Construction of protection barriers at critical points of the watercourse
Construction of gavions [retaining walls made of rocks and chicken wire] along the full length of the watercourse
Cleaning natural watercourses and canals
Construction of drainagefacilities
Reassessment and improvement of rainwater collection and drainage
Reinforcement of the structural system
Others
Strategies for seismic protection
Production of technical specifications for seismic-resistant design
Strategies for protection against volcanic activity

Permanent monitoring and early warning system

2.2.2.3Impactofhazards on thesites under consideration

In the case of each prevailing hazard, an assessment must be made of its likely impact on thepopulationto be served, as well as on local lifelines, related agencies,andoverall accesstohealth services. The likely impactof thephenomenononthehealth networkoftheregion—and, where appropriate, of the country—must also be assessed. This assessmentshould not onlyconsider thenetwork’s infrastructurebutalsothe functional, economic,andpolitical aspects. All too often, whiledamagetohealth infrastructuremay bemanageable fromatechnical viewpoint, thepolitical impactcan bedevastating.

2.2.3Stage 3: Site selection

2.2.3.1Selectionofthebestoption

The informationcompiledmust beprocessedin order to selectthe safest and most convenient siteforthe facility. Table 13 summarizestheminimum activitiesrequired forthe selectionof the best site.

Table 13

Site selection

Productionandsuperimpositionofhazard data
Assessmentof thelevelof riskat each of thesiting options
Characterizationofthehazards presentat each site
Cost assessmentfor the overall protectionofthestructure
Cost assessmentfor the protectionofkey services, systemsandcomponents
Vulnerability assessment(likely impactofeach hazard)
Comparative cost/benefit analysis of the various options
Selectionofdefinitive site for thestructure

Insomecircumstancesit is not possible tomeetthedesiredperformance objective due totheextreme conditionsin which thetarget population is forced to live. Given the lack of safe locations, the project’s performance standards should guide siting choices in ways such as the following:

i.Dividingthefunctionsof the facilityin such a way that they are carried outindifferentlocations that are remotefrom each other.

ii.Procuring mobileortemporaryfacilities.

iii.Producing effective reference systemsso that thepopulationcan easily be transferred to health facilitiesinotherareas.

Theseoptionsmake it possible to distributeorreducetherisk. They alsoincreasecostsandmake operationsmore complex than might be desired, butmay betheonlyreasonable alternative if the level of risk is too great.

2.2.3.2Productionofdocumentsummaries

The informationobtainedduring thepreliminary stage through the risk assessments and theprocessofsite selectionmust besummarizedinadocument that should include, at the very least, thefollowingcontent:

  • Explanationofthereasons for the choice of site.
  • Descriptionoftherisks identified inthe site.
  • Causes ofthose risks.
  • Characterizationoftherisks.
  • Design recommendations for the facility, including the length of timeit can remain cut off from basic services (water, electricity, etc.).
  • Design and protection recommendations for theareaof influence.
  • Protection objectivesforthehealth facility.

3Assessmentofsite safety

Form 3belowshould assist the Project Director andtheCoordination Team in selecting asafesite forthe hospital.

Form 3

4References

ASCE 7-98, Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers, 1998.

FEMA 55: Coastal Construction Manual, Federal Emergency Management Agency, Washington, 1996.

Hallent, B., Photogrammetry: Basic Principles and General Survey, McGraw-Hill, 1960.

Key, D., Structures to Withstand Disasters, Thomas Telford, London, 1995.

Kuroiwa, J., Reducción de Desastres: Viviendo en Armonía con la Naturaleza, Lima, 2002.

Ministry of Housing and Urban Development, Planificación de Asentamientos Humanos en Zonas Propensas a Desastres, Chile, 1982.

PAHO/WHO Collaborating Center for Disaster Mitigation in Health Facilities, Bases Metodológicas: Evaluación de Vulnerabilidad Sísmica de Edificaciones Estructuradas con Pórticos de Preformed concrete, Evaluación de Elementos Arquitectónicos y Evaluación de Equipamiento, University of Chile, 2000.

Pan American Health Organization, Manual para la Mitigación de Desastres Naturales en Sistemas Rurales de Agua Potable, 2001.

Pan American Health Organization, Natural Disaster Mitigation in Drinking Water and Sewerage Systems: Guidelines for Vulnerability Analysis, 2000.

Pan-American Health Organization, Disaster Mitigation for Health Facilities: Guidelines for Vulnerability Appraisal and Reduction in the Caribbean, 2000.

Simiu, E., Wind Effects on Structures: an Introduction to Wind Engineering, John Wiley & Sons, 1978.

Taype, V., “Aplicación de Mapas Geodinámicos en la Prevención de Desastres Naturales”, Fourth National Simposium on the Prevention and Mitigation of Natural Disasters, Lima, CISMID, 1990.


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