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