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Guidance on
Ground gases, VOC’s & Radon.
Validation &Verification.
By: Peter Atchison
Permanent Gas and VOC definitions
Permanent Gas
“Element or compound that is a gas at all ambient temperatures likely
to be encountered on the surface of the earth” – except Radon!
Volatile Organic Compound
a) organic compound that is volatile under normal
environmental/atmospheric conditions, although it can be found in the
ground in the solid, liquid and dissolved phase form as well as in
gaseous phase. (from CIRIA Report 682)
b) organic compound which is liquid at 20 °C and which generally
has a boiling point below 180 °C (after ISO CD 11074:2011)”
The Ground Gas Hierarchy
Bulk gases: Methane, Carbon Dioxide •NHBC - Guidance on evaluation of development proposals on sites where methane and carbon Dioxide are present Report No 10627-RO1 (04) January 2007
•CIRIA - C665 Assessing Risks posed by hazardous ground gases to buildings 2007
•BS8485 – Code of Practice for the characterisation and remediation from ground gas in affected developments Dec 2007
•BS 8576 Guidance on investigations for ground gas – Permanent gases and Volatile Organic Compounds (VOCs)
•VOC/s CIRIA C716
RADON
•BRE 211……………. 1990’s and overdue updating
•Missed out of the Building regulations revision last year -
Is Radon treated as a second rate risk ?
BS 8576: 2013
• Guidance on investigations for
ground gas – Permanent gases
and Volatile Organic Compounds
(VOCs)
• In final draft now
• Links together key recent
documents into a full British
Standard
• Monitoring and sampling of
ground gases
• Does not cover Radon
Preliminary Investigation
• Desk study and site reconnaissance (site walkover) in line
with BS 10175 and establishes the site investigations to
follow based on the objectives set
• For sites in which migration of permanent ground gases is to
be investigated, a conceptual model cross section ‘should’ be
included.
CIRIA C716 – Remediating VOC Risks
• Lead authors Arcadis
• Funders included:
– PAG & GGS
• Covers:
– Petroleum hydrocarbons
– Halogenated hydrocarbons
– N, S & O containing organic compounds
CIRIA C716 - 2012
CIRIA C716
The guidance leads the reader through the three stages of remediation risk mitigation as outlined by DEFRA and the Environment Agency of England and Wales (2004) namely :
1 Development of the remediation strategy
2 Design and implementation of the remediation strategy
3 verification of the remediation strategy (including long term monitoring and maintenance)
Mechanism of Harm
• Ground gas seeps into enclosed spaces (e.g. Buildings), and collects.
• Basements are particularly susceptible to large accumulations (as greater area in contact with soil)
• High concentrations can build up, depending on local geology, atmospheric conditions & ventilation
• Methane – explosive risk if concentrations between 5% and 16% (Acute risk!)
• Carbon Dioxide – asphyxiates in excess concentrations; health affecting at lower concentrations (chronic – acute)
• VOC’s Mainly a odour nuisance but deleterious to health at high concentrations or long term exposure.(generally chronic risk)
• Radon - when inhaled, these irradiate the lungs and increase risk of developing lung cancer.
• Radon – (Chronic Risk) and difficult to consider in isolation from other causes
Concentration of gases in the atmosphere (excluding water vapour)
Gas Percentage by volume
Nitrogen 78.08
Oxygen 20.95
Argon 0.93
Carbon dioxide 0.033
Neon 0.0018
Helium 0.00052
Krypton 0.00011
Hydrogen 0.00005
Xenon 0.0000087
Radon <0.000000000000000001
What is RADON?
• A naturally occurring element
• A radioactive gas
• Colourless & odourless
• Comes from radioactive decay of Radium
• Radium comes from radioactive decay of uranium
RADON Levels
• Average UK background radon concentration outside is 4 Bq m-3
• Outside, radon gas dissipates harmlessly
• Average level inside UK homes is c20 Bq m-
3
• For levels below 100 Bq m-3, individual risk remains relatively low
• However, risk increases as the radon level increases
Radon deaths
– compared to other causes
of UK premature deaths per year
Radon Exposure Risks
Things to Remember!
• Type of Protection
• Membrane choice
• Detailing / Design
• Installation / Installation / Installation
• Validation
• Protection is only as good as its weakest part.
• “Right First time” saves cost!
Validation & Verification
New document not yet published
Approaching “final draft” stage
Likely to be published in 6 months time!!!!!
Aimed at clients and engineers / specifiers in order
to assist them in setting appropriate levels of
validation according to what system has been
used and by whom installed.
Uses all state of the art validation techniques from
visual inspection to integrity testing
Validation and Verification
Presumptions:
ALL installations should be subject to some form of
validation
Validation should be proportionate to the risks from the
site AND the experience of the installation operatives
Validation should be conducted by suitably qualified
INDEPENDENT practitioners.
In the event of appropriate self validation this should be
AUDITED by a suitably qualified independent auditor
Validation & Verification
Table A (Low Rise Housing Only)
Gas regime/ Risk Type of Slab Installer Experience Suggested Levels of Verification & Integrity Testing Basic & Full Radon Protection Area, CS2* (with venting**)
All Slabs General builder/groundworker/ landfill operative [No relevant qualification1]
Independent Consultant4 to conduct a thorough visual inspection of the first plot, including vented void, subgrade, & membrane and after placement of floor reinforcement if no protection layer provided. On successful completion of the first plot independent validation inspections to be carried out at a frequency of around 1 in 10 plots. Contractor to supply plot sign off sheets including photographs to validation consultant for all other plots Consideration given to the need for and scope of integrity testing in the event of continuing concerns identified by visual inspections3
Qualified1 and experienced installer (Minimum 1 operative to hold qualification)
Independent Consultant4 to conduct a thorough visual inspection of the first plot, including vented void, subgrade, & membrane and after placement of floor reinforcement if no protection layer provided. On successful completion of the first plot independent validation inspections to be carried out at a frequency of around 1 in 20 plots. Contractor to supply plot sign off sheets including photographs to validation consultant for all other plots Consideration given to the need for and scope of integrity testing in the event of continuing concerns identified by visual inspections3
CS2* (no venting) or CS3* (with venting**)
General builder/groundworker/ landfill operative [No relevant qualification1]
Independent Consultant4 to Inspect first 10 plots including vented void, subgrade, & membrane and after placement of floor reinforcement if no protection layer provided, furthermore all joints, pipe penetrations, corners etc. should be air lanced to ASTM D 4437. On successful completion of the first 10 plots independent validation inspections including air lancing to be carried out at a frequency of around 1 in 20 plots Contractor to supply plot sign off sheets including photographs to validation consultant for all other plots Consideration given to the need for and scope of integrity testing (e.g. initially on 30-50% of plots then falling to 0-10% of plots if first tranche gives acceptable results and no concerns raised by visual inspections).
Qualified1 and experienced installer (Minimum 1 operative to hold qualification)
Independent Consultant4 to Inspect first 5 plots including vented void, subgrade, & membrane and after placement of floor reinforcement if no protection layer provided, furthermore all joints, pipe penetrations, corners etc. should be air lanced to ASTM D 4437. On successful completion of the first 10 plots independent validation inspections including air lancing to be carried out at a frequency of around 1 in 20 plots. Contractor to supply plot sign off sheets including photographs to validation consultant for all other plots Consideration given to the need for and scope of integrity testing (e.g. initially on 10-25% of plots then falling to 0-5% of plots if first tranche gives acceptable results and no concerns raised by visual inspections) 3.
VOC & Hydrocarbons CS3* (no venting) or CS4* (with venting**)
Qualified1 and experienced installer (ALL operatives to hold qualification)
Independent Consultant4 to Inspect all plots, including vented void, subgrade, membrane and after placement of floor reinforcement if no protection layer provided, furthermore all joints, pipe penetrations, corners etc. should be air lanced to ASTM D 4437. 100% Leak Detection should also be considered. Consideration given to the need for and scope of integrity testing (e.g. initially on 30-50% of plots then falling to 0-10% of plots if first tranche gives acceptable results and no concerns raised by visual inspections) 3.
Notes 1) Relevant qualification is NVG Level 2 Qualification in Gas Protection Installation [see report text] 2) Prior to Commencement of works the contractor should produce a detailed installation plan including: method statement, CQA procedures and qualifications, on receipt of these the validation
protocol could be increased or reduced. 3) Consideration should be given to carrying out integrity testing/ leak detection (i.e. smoke, tracer gas or dielectric testing) on the above basis and/ or if an unacceptable amount of damage/ loss of
integrity is found during visual inspections. In this instance the consultant should discuss with the relevant personnel, strategies to prevent this recurring. This could include changing material, improving subgrade preparation, putting up warning signs to reduce the amount of trafficking etc.
4) Independent Consultants should be appropriately trained and experienced. An example of relevant training could be a certificate of attendance for the C. Skills Installation of Gas Membrane Sector Apprenticeship and Up-Skilling Course (or equivalent), which includes inspection and integrity testing as part of its syllabus. Appropriately experienced could be say 3 years of building surveying, engineering or site supervision/ inspection experience. Less experienced staff should be accompanied by appropriately experienced staff at least for the initial visits. Inspections. A statement detailing the required qualifications and experience should be included in the Verification Plan.
5) Air Lancing is the only integrity test that has an independently recognized international standard that is suitable for testing taped and welded seams and should be used at the frequency suggested in the table.
6) This table should be used for guidance and is not intended to be used in lieu of sound professional judgment. * Gas regime defined by Characteristic Situation as set out in CIRIA C665 (and all other recent good practice guidance and British Standards) ** Assumes Venting designed to keep steady state concentration of CH4 below 1% in void, sites designed with higher levels of gas in the void should adjust the frequency of inspection and testing as deemed necessary.
“Quality is never an accident; it is always the
result of high intention, sincere effort,
intelligent direction and skilful execution; it
represents the wise choice of many
alternatives.”
William A. Foster
• The three most important elements of membrane
efficiency
• INSTALLATION
• INSTALLATION
• INSTALLATION
How to do it well!
And How not to!
The good!
The bad!
And The Ugly!
Attention to detail
Ventilation & ancilliary products
• Void former – Made from cuspated High Density
Polyethylene (HDPE).
– High strength and crush resistance.
– Available as fully wrapped or single-sided geotextile.
• Cross linked butyl sealant – Suitable for joining polyethylene
membranes.
– Very low gas transmission.
Improving standards
Construction Skills
National Occupational Standards (NOS)
Gap identified in the National Qualification
Framework (NQF)
Gas membrane installation for domestic and
industrial/commercial buildings
Existing standards for installing geomembranes
NOSs should reflect current occupational practice
Mandatory Core Standards
NVQ/SVQ Structure
MANDATORY UNITS
Unit No. VR 01 Conform to General Workplace Safety
Unit No. VR 02 Conform to Efficient Work Practices
Unit No. VR 03 Move and handle resources
Unit No. GM 01 Prepare to install venting media and gas membranes
Unit No. GM 02 Install venting media and gas membranes
www.ukstandards.co.uk
Sealing Techniques
Validation / Verification
–Increasingly being specified as part of a well designed solution
–May consist of a variety of or combination of practices and should be specified appropriately according to risk
–There is no “One off” Validation!
–May consist of:
–Check for compliance with specification (Including materials, qualifications of installation operatives and position of components.)
–Visual inspection of work
–Close physical inspection of work including “pick testing”
–Seam and seal testing using test equipment
–Full installation integrity testing using gas, smoke or dielectric testing techniques.
–CIRIA Project currently under way to offer guidance – due published 2013
Always confirm expectations
pre-construction
Combination of protection elements
DPM or proprietary gas resistant membrane
Detailing in line with current good practice
Self installation or specialist sub contractor
Third party validation or
Detailed report with photographs
Integrity testing
Certificate of integrity
NHBC guidance:
Amber 1 & Amber 2
Checklist
Is there sufficient provision for ventilation?
Is there a clear path to atmosphere?
Is the membrane appropriate?
Is the contractor competent to self install for Amber 1?
Have repairs been carried out (correctly)?
Is visual inspection adequate?
Has the contractor employed a specialist for Amber 2
Is a certificated Integrity Test required?
Gas membrane installation:
Concrete prep on Full Line Out
Gas membrane installation:
3-D detailing
External corner with level change
Internal corner
Wind posts & penetrations
Changes in level
Validation Report types
– Often based on LCC pro forma
– Must contain confirmed details of Project particulars & materials used.
– Should contain photographic records
– Should be completed by a “competent person”
– May involve validation via integrity testing
– Typically in “report format” 4-10 pages typical.
– Should be plot and visit specific (You can only validate what you have seen!)
Examples of Report format
Report extract 1
Report extract 2
Validation & Verification
Validation and verification is the single most important aspect of barrier installation and has been implied for many years. Only with the development of this document will designers, clients, practitioners and the like be able to substantiate the presumptions of the past 20 years.
NOS’s VR 612 and 613 describe the process
NVQ level 2 qualification in gas membrane installation has been developed and offered by NSAC
Up-skilling course for installation operatives available via the British Geomembrane Association
How it shouldn’t be done:
Pipe entry missed
How it shouldn’t be done:
End lap not sealed
How it shouldn’t be done:
Both together
How it shouldn’t be done:
Lack of detailing awareness
How it shouldn’t be done:
Run out of gas membrane?
Integrity testing
– Is a TOOL of validation
– Whilst “IT” may be considered the “ultimate” verification…………….
– It should be used appropriately.
– There are a number of different methods currently available.
– Each are appropriate for certain sites
– Further information will be included in CIRIA guidance on validation and
verification Due 2013
Integrity testing
Set up
Introduce tracer gas
Scan and repair
In conclusion
•Much has been accomplished over the last 10 years
•Much is still to be done
•Quality design relies on quality data.
•Good quality materials need good quality workmanship to perform
•Standards exist and can be applied
•Validation and verification form part of a quality design
•So could you be a “validator”………………..?
Spot The difference!
“Be a yardstick of quality. Some people aren't
used to an environment where excellence is
expected.”
Steve Jobs (1955 -2011)
Thank You
And remember ………………..
Thank you
Peter Atchison
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