Nicola
Using the full building foot print may not be appropriate. It will depend on the building foundation and floor slab construction and the assumptions
you are making about the area of the ingress pathway (ie area of cracks). For example if you are assuming a perimeter crack (which may or may not be appropriate) the larger the floor area you assume the lower the estimated vapour ingress will be compared
to the fresh air changes inside the building (assuming crack width stays constant).
In a basement the worst case may be a room on a corner where cracks could be present at the interface between slab and wall and also at corner between
walls. Depends on type of construction.
You really need to consider the CSM for the building and make sure it fits the equations and parameters you are using in the risk assessment.
Steve Wilson, Technical Director
The Environmental Protection Group Ltd
Tel 07971 277869
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]]
On Behalf Of Dumitrescu , Luiza L
Sent: 03 March 2017 15:13
To: [log in to unmask]
Subject: Re: Vapour intrusion in CLEA for flatted development
Hi Nicola,
We had a similar site for a block of flats development where we had to do a vapour DQRA. The building had a basement, + four storeys.
We started with the basement as the first floor and the volume of the basement as the indoor air space. We have assumed the full block footprint as being the building area.
We adopted an approach of ‘forward modelling’ in the sense that the first floor (in our case a basement) was firstly modelled considering
the volatiles concentrations in the respective sources (soil and groundwater); then ratio mode was used to calculate a hazard quotient based on the percentage contribution to the indoor vapour inhalation pathway for each contaminant, and to provide an estimate
of the indoor air concentration in the basement (using J&E) for each contaminant. For our DQRA, the calculated indoor concentration was significantly below the indoor air reference concentrations which we have used for screening (from my experience this is
usually the case once you model a predicted indoor air concentration, even if you have exceedances in soil and groundwater source).
Hope this helps.
Luiza
Luiza Dumitrescu
Senior Environmental Consultant BSc (Hons) MSc CEnv
Infrastructure
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]]
On Behalf Of Nicola Matthews
Sent: 03 March 2017 14:36
To: [log in to unmask]
Subject: Vapour intrusion in CLEA for flatted development
Hi All
Does anyone have and useful references/suggestions on how to determine the indoor air space for flatted developments in CLEA?
Would you assume the living space accounts for the number of storeys in the building (e,g, 6 floors), or just one floor given that a persons living space would only be on one storey? Similarly, would you assume the full block footprint
is the building area, or the individual flat/property within that block?
None of the guidance docs in CLEA seem to advise regarding flats for considering flatted developments.
Thanks in advance,
Nicola Brookfield (Scott Bennett Associates)
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