voc investigation and gocls vapour generic assessment criteria

4 De Frene Road, London SE26 4AB

020 8291 1676

[email protected]

www.gosolve.co.uk

VOC investigation and GOCLS vapour Generic

Assessment CriteriaCristiano Ascolani, Contaminated Land Consultant

mailto:[email protected]

http://gosolve.co.uk/

VOC

“Organic compounds that are volatile under normal environmental/atmospheric conditions, although they may be found in the ground in the soil, liquid and dissolved phase as well as in the gaseous phase”Baker, K., et al. Investigating, assessing and managing risks of inhalation of VOC on land affected by contamination. CIRIA C682. London : CIRIA, 2009

Typical VOCs:

• Petroleum hydrocarbons (e.g. benzene, toluene, butylbenzene)

• Halogenated hydrocarbons (e.g. dry cleaning fluids, freons)

• Organic compounds containing nitrogen sulphur and oxygen (e.g. THF)

10/05/2017VOC investigation and GOCLS vapour Generic

Assessment Criteria1

Sources and pathways

1. Solid• Contaminants within soil

2. Liquid• NAPL


Assessment Criteria

3. Dissolved phase• Contaminants within water

4. Gaseous phase• Pressure-driven gas flow

2

On-site

VOCCO2 CH4

CH4

CO2

Off-siteSite

boundary

Environmental media

Source

• Soil

• Groundwater

• NAPL

• Soil gas (away from building influence

Pathway

• Sub-foundation slab soil gas

• Near-foundation slab soil gas

Receptor

• Surface emissions

• Point of exposure (air)



Investigation in soil

Hand auger Trial pits Boreholes In situ probing



Sampling: collection of soil samples into a container

Monitoring wells (typically within

boreholes)In situ probing

Investigation in groundwater



Sampling: bailers, low-flow

tubing, passive diffusion bags

PASSIVEACTIVE

Investigation in soil gas

Shallow / driven probe (hollow rod)

Driven buried soil gas monitoring tube / pipe

Buried soil gas monitoring tube / pipe

(sub-slab)In situ probing Driven rod / probe



Sampling: vacuum stainless steel canister or pump used to retrieve sample

collected within soil gas container or on sorbent material

Sampling: burial of

sorbent material

into ground and

removal

AIR

Investigation in other media



LNAPL & DNAPLSURFACE EMISSIONS

Static and dynamic flux chamber

Indoor air sampling Monitoring well

• Soil / rock / made ground

• Groundwater including perched

• Soil gas in unsaturated zone

• NAPL

• Further investigation of the previous source media if needed, in

addition to: near-slab soil gas

• Sub-slab soil gas

• Air at point of exposure

Investigation hierarchy



Generic Assessment Criteria

Medium On-site exposure

Soil SGVs

LQM/CIEH S4ULs

EIC/AGS/CL:AIRE GAC

ATRISKsoil SSVs

C4SLs

…

Groundwater SOBRA sub-surface water GAC

ATRISKsoil WSVs

…

Soil gas None



Generic Assessment Criteria

Medium On-site exposure

Soil SGVs

LQM/CIEH S4ULs

EIC/AGS/CL:AIRE GAC

ATRISKsoil SSVs

C4SLs

…

Groundwater SOBRA sub-surface water GAC

ATRISKsoil WSVs

…

Soil gas None



DEVELOPMENT OF GAC FOR VAPOUR INTRUSION

IN ACCORDANCE WITH UK GUIDANCE

GO CLS vapour Generic Assessment Criteria (vGAC)



GOCLS vGAC: methodology

• Amended Health Criteria Values (HCVs) concerning vapour inhalation produced using CLEA v 1.07

• vGAC produced using the calculated HCVs and Johnson and Ettinger Model assuming vapour intrusion only via advection

• Physical-chemical and toxicological parameters from LQM/CIEH S4ULs (2015) and EIC/AGS/CL:AIRE GAC (2010)

• Volatile contaminants (Kaw < 4 x 10-4)



GOCLS vGAC: summary

• vGAC for 61 compounds:o9 Monocyclic Aromatic Hydrocarbonso5 Polycyclic Aromatic Hydrocarbonso10 Total Petroleum Hydrocarbon carbon rangeso2 Gasoline Additives o35 Halogenated Hydrocarbons

• Residential use, commercial land use and petrol filling station

• vGAC relevant for: 1) open space 2) near slab 3) sub slab

• Indoor air sampling data to be compared with amended HCVs (inhalation only)



Johnson & Ettinger Model

• CLEA model includes the J&E model for the estimation of vapour intrusion

• J&E model output: attenuation factor (𝛼)

𝛼 =𝐶𝑎𝑖𝑟𝐶𝑣𝑎𝑝

× 106𝑐𝑚3𝑚−3

𝐶𝑎𝑖𝑟: indoor air concentration, mg m-3

𝐶𝑣𝑎𝑝: soil vapour concentration, mg cm-3



𝑪𝒗𝒂𝒑

𝑪𝒂𝒊𝒓

𝜶enclosed space

vaporintrusion

VaporSource

• 𝐶𝑎𝑖𝑟 = 𝑎𝑚𝑒𝑛𝑑𝑒𝑑 𝐻𝐶𝑉

• 𝐶𝑣𝑎𝑝 = 𝑣𝐺𝐴𝐶

𝛼 =𝐶𝑎𝑖𝑟

𝐶𝑣𝑎𝑝֜ 𝛼 =

𝑎𝑚𝑒𝑛𝑑𝑒𝑑 𝐻𝐶𝑉

𝑣𝐺𝐴𝐶

𝒗𝑮𝑨𝑪 =𝒂𝒎𝒆𝒏𝒅𝒆𝒅 𝑯𝑪𝑽

𝜶

Critical receptors

Land end use

(exposure time)

Building type

Soil type

Source distance

Johnson & Ettinger Model



𝑪𝒗𝒂𝒑

𝑪𝒂𝒊𝒓

𝜶enclosed space

vaporintrusion

VaporSource

J&E Model: critical parameters

Movement of soil gas controlled by:

1. Diffusion: transport of a substance by concentration gradient

2. Advection: transport of a substance by bulk motion

Depending on transport mechanism, in 2002 Johnson identified solutions based on three multi-component parameter 𝐴, 𝐵and 𝐶

enclosed space

vaporintrusion

Diffusion[pseudo-

steady state

Well-MixedAdvection and

Diffusion

Source

[steady or transient]

VaporSource



J&E sensitivity to transport mechanism

Diffusion is the dominant

mechanism across foundation

Diffusion through soil is the over-all

rate-limiting process

𝛼 ≈𝐴

1 + 𝐴

Diffusion through foundation is the

over-all rate-limiting process

𝛼 ≈𝐶

𝐵

Advection is the dominant




𝛼 ≈ 𝐴

Advection through foundation is the


𝛼 ≈ 𝐶



J&E sensitivity to to transport mechanism

Diffusion is the dominant




𝛼 ≈𝐴

1 + 𝐴

Diffusion through foundation is the


𝛼 ≈𝐶

𝐵

Advection is the dominant




𝛼 ≈ 𝐴

Advection through foundation is the


𝛼 ≈ 𝐶



MOST

CONSERVATIVE

Attenuation factor (advection only)

𝜶 ≈ 𝑪 =𝑸𝒔

𝑸𝑩𝑄𝑠: volumetric flow rate of soil gas into the enclosed space, cm3 s-1

(SR7: 25 cm3 s-1 for residential land use, 150 cm3 s-1 for commercial land use)

𝑄𝐵: building ventilation rate, cm3 s-1

𝑄𝐵 = 𝐻 × 𝐴𝑓𝑜𝑜𝑡 × 𝐸𝑥𝐻: height of living space, m

𝐴𝑓𝑜𝑜𝑡: building footprint, m2

𝐸𝑥: building air exchange rate, hr-1



Amended Health Criteria Values (HCVs)

• HCV and background inhalation from LQM/CIEH S4ULs (2015) and EIC/AGS/CL:AIRE GAC (2010)

• CLEA Model, only exposure due to indoor vapour intrusion

Two different scenarios:

1. SR3 residential land use

2. SR3 commercial land use



Amended HCV on CLEA Model

1. Set up model with appropriate parameters/calculations

2. Derive results (AC)

3. Unhide/unprotect “Media Calculations” sheet

4. Adopt “Indoor Air Concentration of Vapours” as amended HCV



Calculation of GOCLS vGAC

𝑣𝐺𝐴𝐶 =𝑎𝑚𝑒𝑛𝑑𝑒𝑑 𝐻𝐶𝑉

𝛼Three scenarios:

1. SR3 residential land use

2. SR3 commercial land use

3. Service station: critical receptors and land use as SR3 commercial land use, building type as SR3 bungalow (similar to convenience store)



GOCLS vGAC: conservative approach

• Main assumption: source lies directly beneath the building and no additional depletion via diffusion occurs

• Most conservative soil type and worst-case building scenario

• Biodegradation of VOCs not taken into account



Conclusions

• VOCs may be found in sorbed, liquid, dissolved and/or gaseous phase.

• Investigation can be focused on several environmental media.

• GAC concerning inhalation exposure are available for soil or water. GAC for soil gas may be produced.

• GOCLS produced vGAC using the CLEA Model and the revised J&E model considering only advection as transport mechanism.

• Amended HCV (indoor vapour concentration) are available for residential and commercial land.

• GOCLS vGAC (open space and near- and sub-slab) are available for residential land use, commercial land use and petrol filling station.



References

Baker, K., et al. Investigating, assessing and managing risks of inhalation of VOC on land affected by contamination. CIRIA C682. London : CIRIA, 2009.

Heuristic model for the intrusion rate of contaminant vapors into buildings. Johnson, P.C. and Ettinger, R.A. 8, s.l. : ACS Publications, 1991, Environmental Science & Technology, Vol. 25, pp. 1445-1452.

Identification of critical parameters for the Johnson and Ettinger (1991) vapor intrusion model. Johnson, P. C. 2002, American Petroleum Institute, Vol. 17, pp. 1-N2

Department of the Environment, Food and Rural Affairs and Environment Agency. CLR 11: Model procedures for the management of land contamination. 2004.

Environment Agency. Human health toxicological assessment of contaminants in soil. Bristol : Environment Agency, 2009. Science Report - Final. SC050021/SR2.

Jeffries, J. and Martin, I. Updated Technical background to the CLEA model. Bristol : Environment Agency, 2009. p. 166, Science Report.

