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Buro Happold
Appendix F: Preliminary Risk Assessment
Northumberland Development Project
Geotechnical Desk Study and Preliminary Geoenvironmental Risk Assessment
Copyright © Buro Happold Limited
Revision 00
November 2008
Appendix F Preliminary Risk Assessment
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
Consequence
Probability
Risk
concern
affected
Made
Heavy metals,
Site Wide
Ground
other inorganic
(Demolition
contaminants,
debris,
asbestos, total
former &
petroleum
current
hydrocarbons
land uses across site including steelworks, steelworks, car
industrial
(TPH), polycyclic
workshops & engineering works etc.
land uses)
aromatic
Up to 3.5m of Made Ground (average 2m) expected. Made Ground
likely to comprise clayey SAND and GRAVEL. Gravels typically
comprise of brick, flint, clinker, ash, chalk, glass, slag and glass with
rare organic material i.e. wood. Numerous historical industrial and
SOILTECHNICS ground investigation report 2005 (ref 3) recorded
hydrocarbons
(PAHs), carbon
elevated concentrations of lead (<1100mg/kg), Benzo(a)pyrene
dioxide,
(<9.8mg/kg) and PAH (up to 120mg/kg) in Made Ground.
methane, semi-
Nature/extent of contamination is not fully known/ proven but likely to
volatile and
volatile organic
be widespread and with gross contamination present in localised
compounds
areas.
(SVOC & VOC),
PCB oils.
Soil and dust
Health impact to
ingestion, dermal
construction workers
Medium
Lowlikelihood
Moderate/
Low
Potential for exposure during excavations/earthworks. Standard Health &
Safety precautions likely to be used by workers.
contact, vapour
inhalation (outdoor
air)
Soil and dust
Health impact to site users
ingestion, dermal
and visitors
Medium
Low
Moderate/
Accidental exposure prevented due to site being currently covered in hard
likelihood
Low
standing. Potential for uncontrolled exposure in areas of soft landscape in
contact, vapour
the future. Potential for uncontrolled exposure to dust etc during
(outdoor & indoor
earthworks. Appropriate investigation and risk assessment/mitigation in
air)
the final development is likely.
Soil and dust
Health impact to residents
ingestion, dermal
of the adjacent properties
Medium
Lowlikelihood
Moderate/
Low
contact.
Potential for contamination to migrate onto adjacent sites during any
earthworks with resulting uncontrolled exposure. Residential, Primary and
Secondary Schools, Sports Centre and Community Centre located
adjacent to the site boundary. Standard good construction practice likely
to inhibit dust generation.
Migration via
Degradation of water
permeable strata
quality [Kempton Park
Gravels Minor Aquifer]
Medium
Low
likelihood
Moderate/
Leachate results from SOILTECHNICS report (2005) suggest
Low
contaminants are not highly mobile. Localised deposits of silt overlie
gravels but unlikely to provide effective barrier to downward migration of
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Consequence
Probability
Risk
any mobile contamination. Infiltration significantly inhibited by present
hardstanding. Final development also likely to be mostly hardstanding.
Potential for infiltration during earthworks. Groundwater likely to be
degraded by history of commercial/ industrial use. Expected at shallow
depth (~2-3.5m). Flow direction unknown No local surface water limiting
potential for baseflow.
Migration via
Degradation of water
permeable strata
quality [Woolwich and
aquifers, limiting vertical migration. Infiltration will be significantly reduced
Reading Beds – Minor
in final development. Potential for infiltration during earthworks. Majority of
Aquifer. Chalk Major
site lies within SPZ II. Nearest abstraction over 285m NE (rubber: general
Aquifer]
cooling).
Direct contact/,
Permeation of water
aggressive attack/
supply pipework
Medium
Medium
Unlikely
Lowlikelihood
Low
Moderate/
Low risk
below ground
Significant thickness of low permeability London Clay overlying the deeper
Potential for direct contact. Appropriate investigation/ design likely in any
new buildings. Previous investigation results show there is potential for an
aggressive ground environment.
structures
Root uptake
Detrimental effects
Minor
(stunted growth, die-back)
Low-
Very Low
likelihood
uptake in any areas of public open space (<5% of future development) or
on plant life.
Methane, carbon
Gas/vapour
Explosion, fire,
dioxide, VOC
migration via
asphyxiation hazard to
vapours
permeable strata
construction workers, site
and accumulation
end users, users of
in enclosed
adjacent buildings
spaces
Limited vegetation onsite did not show any adverse effects. Potential for
neighbouring gardens.
Severe
Lowlikelihood
Moderate
SOILTECHNICS have undertaken ground gas monitoring at the site in
2005. Recorded maximum concentrations of methane (24.5%) and
carbon dioxide (12%). Source of methane unknown. Further
monitoring proposed but results have not been obtained.
Potential for significant generation / migration of gases associated with
decomposition of any organic matter in Made Ground and presence of
hydrocarbons. Unprotected below ground/ enclose spaces would enable
accumulation of gas to hazardous concentrations.
Former Fuel
PAHs, MTBE,
On site (to
Station
heavy metals,
the east
VOCs, SVOC,
fronting
hydrocarbons
High Road)
(TPH, BTEX),
methane and
carbon dioxide
Former fuel station located onsite. No visual evidence of leakage.
SOILTECHNICS report noted slight hydrocarbon odour in Kempton
Park Gravels.. SOILTECHNICS indicated former station’s tanks and
fuel lines have been foam filled.. Location of tanks indicated on
drawings but invert levels unknown. Nature/extent of contamination
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Consequence
Probability
Risk
gases.
is not fully known/ proven.
Soil and dust
Health impact to
ingestion, dermal
construction workers
Medium
Lowlikelihood
Moderate/
Low
Potential for exposure during excavations/earthworks. Standard Health &
Safety precautions likely to be used by workers.
contact, vapour
inhalation (outdoor
air)
Soil and dust
Health impact to site users
ingestion, dermal
and visitors
Medium
Low
likelihood
Moderate/
Low
Accidental exposure prevented due to site being currently covered in hard
standing. Potential for uncontrolled exposure in areas of soft landscape in
contact, vapour
the future. Potential for uncontrolled exposure to dusrt etc during
(outdoor & indoor
earthworks. Appropriate investigation and risk assessment/mitigation in
air)
the final development is likely.
Soil and dust
Health impact to residents
ingestion, dermal
of the adjacent properties
Medium
Lowlikelihood
Moderate/
Low
contact.
Potential for contamination to migrate onto adjacent sites during
earthworks with resulting uncontrolled exposure. Residential and retail
properties located on western boundary of site. Standard good
construction practice likely to inhibit dust generation.
Migration via
Degradation of water
permeable strata
quality [Kempton Park
Medium
Low
likelihood
Moderate/
Leachate results from SOILTECHNICS report (ref 3) suggest
Low
contaminants are not highly mobile. Localised deposits of silt overlie
Gravels Minor Aquifer]
gravels but unlikely to provide effective barrier to downward migration of
any mobile contamination. Infiltration significantly inhibited by present
hardstanding. Final development also likely to be mostly hardstanding.
Potential for infiltration during earthworks. Groundwater likely to be
degraded by history of commercial/ industrial use. Expected at shallow
depth (~2-3.5m). Flow direction unknown No local surface water limiting
potential for baseflow.
Migration via
Degradation of water
permeable strata
quality [Woolwich and
overlying the deeper aquifers, inhibiting vertical migration. Infiltration will
Reading Beds – Minor
be significantly reduced in final development. Potential for infiltration
Aquifer. Chalk – Major
during earthworks. Former fuel station does not lie within SPZ II. Nearest
Aquifer]
abstraction over 285m NE (rubber: general cooling).
Medium
Unlikely
Low
Likely to be a significant thickness of low permeability London clay
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Direct contact/,
Permeation of water
aggressive attack/
supply pipework
Consequence
Probability
Risk
Medium
Low-
Moderate/
likelihood
Low risk
below ground
Potential for direct contact. Appropriate investigation/ design likely in any
new buildings. Previous investigation results show there is potential for an
aggressive ground environment.
structures
Root uptake
Detrimental effects
Minor
(stunted growth, die-back)
Low-
Very Low
likelihood
uptake in any areas of public open space (<5% of future development) or
on plant life.
Methane, carbon
Gas/vapour
Explosion, fire,
dioxide, VOC
migration via
asphyxiation hazard to
vapours
permeable strata
construction workers, site
and accumulation
end users, users of
in enclosed
adjacent buildings
Limited vegetation onsite did not show any adverse effects. Potential for
neighbouring gardens.
Severe
Low-
Moderate
likelihood
No gas monitoring carried out in vicinity of former fuel station. Potential
for localised generation/ migration of gases associated with
decomposition/ breakdown of hydrocarbons.
spaces
Tanks
Heavy metals,
(including
other inorganic
Diesel,
contaminants,
Unknown
total petroleum
Storage)
hydrocarbons
Site Wide
Diesel tank and another tank of unknown content identified onsite.
No visual/ olfactory evidence of leakage. Contents of two further
tanks and two potential tanks identified by Envirocheck report
unknown. Tanks not observed during site walkover. Nature/extent of
(TPH), polycyclic
contamination is not fully known/ proven but likely to be relatively
aromatic
localised..
hydrocarbons
(PAHs), carbon
Soil and dust
Health impact to
dioxide,
ingestion, dermal
construction workers
methane, semi-
contact, vapour
volatile and
inhalation (outdoor
volatile organic
air)
Medium
Lowlikelihood
Moderate/
Low
Potential for exposure during excavations/earthworks. Standard Health &
Safety precautions likely to be used by workers.
compounds
(SVOC & VOC),
Soil and dust
Health impact to site users
PCB oils and
ingestion, dermal
and visitors
solvents.
contact, vapour
the future. Potential for uncontrolled exposure to dusrt etc during
(outdoor & indoor
earthworks. Appropriate investigation and risk assessment/mitigation in
air)
the final development is likely.
Medium
Unlikely
Low
Accidental exposure prevented due to site being currently covered in hard
standing. Potential for uncontrolled exposure in areas of soft landscape in
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Soil and dust
Health impact to residents
ingestion, dermal
of the adjacent properties
Consequence
Probability
Risk
Medium
Unlikely
Low
Potential for contamination to migrate onto adjacent sites during
earthworks with resulting uncontrolled exposure. Residential, Primary and
contact.
Secondary Schools, Sports Centre and Community Centre located
adjacent to the site boundary. Standard good construction practice likely
to inhibit dust generation.
Migration via
Degradation of water
permeable strata
quality [Kempton Park
Medium
Low
likelihood
Moderate/
Low
Gravels Minor Aquifer]
Localised deposits of silt overlie gravels but unlikely to provide effective
barrier to downward migration of any mobile contamination. Infiltration
significantly inhibited by present hardstanding. Final development also
likely to be mostly hardstanding. Potential for infiltration during
earthworks. Groundwater likely to be degraded by history of commercial/
industrial use. Expected at shallow depth (~2-3.5m). Flow direction
unknown No local surface water limiting potential for baseflow.
Migration via
Degradation of water
permeable strata
quality [Woolwich and
overlying the deeper aquifers, inhibiting vertical migration. Infiltration will
Reading Beds – Minor
be significantly reduced in final development. Potential for infiltration
Aquifer. Chalk – Major
during earthworks. Majority of site lies within SPZ II. Nearest abstraction
Aquifer]
over 285m NE (rubber: general cooling).
Direct contact/,
Permeation of water
aggressive attack/
supply pipework
Medium
Medium
Unlikely
Unlikely
Low
Low risk
Likely to be a significant thickness of low permeability London clay
Potential for direct contact. Appropriate investigation/ design likely in any
new buildings.
below ground
structures
Root uptake
Detrimental effects
Minor
(stunted growth, die-back)
Low-
Very Low
likelihood
uptake in any areas of public open space (<5% of future development) or
on plant life.
Gas/vapour
Explosion, fire,
migration via
asphyxiation hazard to
permeable strata
construction workers, site
and accumulation
end users, users of
in enclosed
adjacent buildings
Limited vegetation onsite did not show any adverse effects. Potential for
neighbouring gardens.
Severe
Lowlikelihood
Moderate
Potential for localised generation/ migration of gases associated with
decomposition/ breakdown of organic matter/ hydrocarbons.
spaces
Electrical
PCBs and
Substation
Mineral Oils
Site Wide
Three electrical substations indicated by Groundsure maps to be
present within site boundary. Two observed during site visit. No
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Consequence
Probability
Risk
visual/ olfactory evidence of leakage. Any historic losses likely to be
aged, minor and localised.
Soil and dust
Health impact to
ingestion, dermal
construction workers
Minor
Low-
Very Low
likelihood
Potential for exposure during excavations/earthworks. Standard Health &
Safety precautions likely to be used by workers.
contact, vapour
inhalation (outdoor
air)
Soil and dust
Health impact to site users
ingestion, dermal
and visitors
Minor
Unlikely
Very low
Accidental exposure prevented due to site being currently covered in hard
standing. Potential for uncontrolled exposure in areas of soft landscape in
contact, vapour
the future. Potential for uncontrolled exposure to dusrt etc during
(outdoor & indoor
earthworks. Appropriate investigation and risk assessment/mitigation in
air)
the final development is likely.
Soil and dust
Health impact to residents
ingestion, dermal
of the adjacent properties
Mild
Unlikely
Very Low
Potential for contamination to migrate onto adjacent sites during any
earthworks and resulting uncontrolled exposure.. Residential, Primary and
contact.
Secondary Schools, Sports Centre and Community Centre located
adjacent to the site boundary. Standard good construction practice likely
to inhibit dust generation.
Migration via
Degradation of water
permeable strata
quality [Kempton Park
barrier to downward migration of any mobile contamination. Infiltration
Gravels Minor Aquifer]
significantly inhibited by present hardstanding. Final development also
Medium
Unlikely
Low
Localised deposits of silt overlie gravels but unlikely to provide effective
likely to be mostly hardstanding. Potential for infiltration during
earthworks. Groundwater likely to be degraded by history of commercial/
industrial use. Expected at shallow depth (~2-3.5m). Flow direction
unknown No local surface water limiting potential for baseflow.
Migration via
Degradation of water
permeable strata
quality [Woolwich and
overlying the deeper aquifers, inhibiting vertical migration. Infiltration will
Reading Beds – Minor
be significantly reduced in final development. Potential for infiltration
Aquifer. Chalk – Major
during earthworks. Majority of site lies within SPZ II. Nearest abstraction
Aquifer]
over 285m NE (rubber: general cooling).
Direct contact/,
Permeation of water
aggressive attack/
supply pipework
below ground
Medium
Mild
Unlikely
Lowlikelihood
Low
Low
Likely to be a significant thickness of low permeability London clay
Potential for direct contact. Appropriate investigation/ design likely in any
new buildings. Previous investigation results show there is potential for an
aggressive ground environment.
Source
Pathway
Hazard to Receptor
Risk assessment (following CIRIA C552)
Description of source [bold text]. Comment on hazard realisation
[normal text]
Origin
Contaminants of
Zone
concern
affected
Consequence
Probability
Risk
Minor
Low-
Very Low
structures
Root uptake
Detrimental effects
(stunted growth, die-back)
on plant life.
likelihood
Limited vegetation onsite did not show any adverse effects. Potential for
uptake in any areas of public open space (<5% of future development) or
neighbouring gardens.
Charlotte Woodhall-Jones
Buro Happold Limited
Camden Mill
Lower Bristol Road
Bath
BA2 3DQ
UK
Telephone: +44 (0)1225 320600
Facsimile: +44 (0)870 787 4148
Email: [email protected]