Article Contaminated Land Data Management Laboratories

NHBC’s Role in Developing Hazardous Sites

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Tags: brownfield data Investigations NHBC

NHBC (National House-Building Council) is the standard setting body and the leading warranty and insurance provider for new and newly converted homes in the UK. Our role is to work with the house-building and wider construction industry to provide warranty, risk management and compliance services that raise the standards of new homes, and to provide consumer protection to new homebuyers.

Approximately 80% of new homes built in the UK each year are registered with NHBC and benefit from our 10-year warranty and insurance policy called Buildmark. Around 1.6 million homes are currently covered by Buildmark policies and over the past 40 years, NHBC has protected more than 30% of all existing homes in the UK.

In 1999 Buildmark was extended to provide the homeowner with protection cover against the issue of a statutory notice. This was done in the anticipation of Part 2A, which came into force a year later.

The NHBC Foundation

The NHBC Foundation was launched in 2006 in partnership with the BRE Trust. Its remit is to provide the necessary data and intelligence to develop long-term solutions to industry challenges which lie ahead and lead debate and thinking among industry experts. The NHBC Foundation facilitates research and development, and shares pragmatic and relevant guidance and good practice to the homebuilding industry.

Though much of the NHBC Foundation’s research is focused on the challenges of the Government’s 2016 zero carbon homes target, published works do include ground related issues such as ground source heat pumps, the risks associated with basement construction and the efficient design of piling for housing.

NHBC Standards

The 2011 NHBC Standards, effective from 1 January 2011, introduced for the first time a new chapter for low or zero carbon technologies (Chapter 3.1). It also included an update to Chapter 4.1 – Land quality on managing ground conditions, and a major update to Chapter 4.6 – Vibratory and ground improvement techniques, as well as reference to the introduction of Eurocodes in place of British Standards.

The latest update to the NHBC Standards continues our corporate mission to work with the house-building and wider construction industry to provide guidance, inspection and technical services to raise the standard of new build UK homes to protection homeowners. The identification of geotechnical risk assessment and the implementation of robust site investigations and geotechnical and remediation designs are therefore essential to NHBC, our developer customers and ultimately the homeowner.

Chapter 4.1 Land quality – managing ground conditions

Chapter 4.1 was first published in 1998 and, since that time, few changes have been made. The Chapter has now been updated to reflect recent technical changes and developments, made to reflect the changes to British Standards and the development of European Standards. It now includes technical guidance produced since the Chapter was last revised and better aligns the process for assessing contaminated land with the Government’s guidance document CLR 11 (Contaminated Land Report 11): Model Procedures for the Management of Land Contamination (2004).

Chapter – CH4.6 Vibratory ground improvement techniques

The update to Chapter 4.6 reflects changes and innovations in ground improvement techniques. It outlines current industry practice, provides additional guidance on the suitability of ground to be treated, clarifies the objective of vibro treatment, and updates the range of suitable stone fill for vibro column materials by permitting the use of suitable recycled aggregates. It now also references Eurocode EC7 (BS EN 1997 – Geotechnical Design).

The new Standards reflect the EU wide transition to Eurocodes for the design of structural elements following the withdrawal of the existing British Standards in March 2010. It is proposed that the Building Regulations in England and Wales will be revised in 2013, with the structural Eurocodes becoming the standard reference document for demonstrating compliance. In the interim, the Public Contract Regulations 2006 require Eurocodes to be used for the design and construction of publically funded building projects.

For geotechnically challenging sites, such as those where vibro improvement, piling or engineered fill is required, the management of geotechnical risk is likely to be enhanced by adherence to EC7. Additionally, in the UK, the British Standard for Earthworks (BS6031:2009) has also been extensively revised and is now compatible with the Eurocodes. These documents set out the requirements for assessing the geotechnical suitability of the ground for development and the execution of stabilisation works and foundations.

Some of the changes include:

  • References to the 15 kPa absolute limit on soft clay strength has been dropped
  • The 30 kPa limit on soft clays is maintained as not being generally acceptable unless the suitability of the treatment can be demonstrated, taking due account of the impact of group effects, ground heave and settlement
  • Requirement to consider inundation settlement risk issues of poorly compacted fill
  • Requirement to consider surcharging settlement effects
  • References to chalk or clay fills have been omitted and replaced with the generic ‘loose or un-engineered fills’
  • Requirement to consider effects on ground gas and contamination
  • Recycled aggregates can be used subject to compliance with BRE Digest 433 or other suitable guidance, such as WRAP
  • Validation testing is required of treated ground to confirm that the proposed load-settlement performance has been achieved
  • Requirement to produce validation reports confirming that the proposed load settlement performance of treated ground has been achieved
  • Clarification that plate load tests on stone columns alone are not acceptable to NHBC for treatment validation

 

Land Quality Endorsement (LQE)

For housing developments on major Brownfield sites requiring significant geotechnical and contamination remediation, NHBC has increasingly noted that many of the sites developed for housing in the UK are remediated by specialist remediation companies, landowners, private developers, regeneration specialists, development agencies and similar companies.

These organisations are responsible for or own contaminated land and are remediating them for residential development. However, they are not themselves NHBC registered builders or developers, and are therefore outside NHBC risk management processes and may not be aware of NHBC’s requirements.

NHBC introduced Land Quality Endorsement (LQE) in 2005 as a consultancy service providing technical risk management for sites being remediated befoere residential development. LQE allows the assessment of contaminated and brownfield sites against the requirements of the NHBC Standards.

This determines the suitability of these sites for Buildmark cover in advance of the formal registration of residential properties. Sites are assessed against the requirements of NHBC Standards Chapter 4.1, including a review of geotechnical and foundation proposals alongside contamination assessments.

The pre-registration assessment of sites affected by contamination and the remediation adopted will potentially enhance the marketability of a site by reducing the potential risks to the builder or developer, whilst saving time and effort.

Article Contaminated Land Laboratories

UKWIR – GUIDANCE FOR THE SELECTION OF WATER SUPPLY PIPES TO BE USED IN BROWNFIELD SITES

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Tags: analysis brownfield contaminated investigation laboratories

Peter Boyd, AECOM Limited and Neil Parry, Geotechnical Engineering Limited

The UK Water Industry Research (UKWIR) has produced this document to replace the heavily criticised 2002 WRAS guidance on water supply pipe materials for contaminated land. Unfortunately there remain several similar problems with the new document. It has been produced by UKWIR with the footnote “Promoting Collaborative Research” but there does not appear to have been any collaboration or consultation with practitioners in the industry. As a result the document fails to reflect commonly accepted industry practice and terminology.

The basis of the document is highly conservative, for example making reference to identifying whether “any chemical may have ever been on a site” and that “samples should be collected at a frequency and depth that will identify any contamination”.  Although it rightly advocates a risk based approach to sampling and assessment many of the recommendations ignore this premise and current guidance, with the end result likely to be overdesign and significantly increased costs for end users.

The document was recently revised, where some of the initial errors were corrected, unfortunately several errors remain and the opportunity to gain widespread acceptance was missed.

The responsibility for the selection of supply pipes is confused between the Developer, Self Lay Organisation (SLO) and Designer.  The responsibility for the production of the crucial Site Assessment Report (SAR) is not clear between the “Developer” or the “Designer” without considering whether they have the necessary contaminated land expertise.  Guidance such as the new Eurocodes define competence roles and from an industry perspective it’s yet another missed opportunity to give some further recognition to the SiLC qualification. It seems to be aimed at the layman but also advocates a very wide ranging and unusual range of laboratory implying the user has a detailed knowledge of soil sampling, preservation and laboratory testing. It is also unfortunate that 30 years after the first edition of BS5930 the document blurs the distinction between site investigation and ground investigation.

Desk Study
The document provides some good general guidance on establishing previous site use and the potential for contamination but insufficient information or reference is provided for a general user to adequately complete this.  It suggests that the findings should be summarised on a map to show current and historic land use but show a level of detail at a scale which would not be possible in most practical instances. implying that the authors have not actually performed this exercise with real data or thought about the preparation of a robust conceptual model, which is the basis for most contaminated land assessment.

The document suggests that the Local Authority may request an SAR as part of the planning process.  There is no recognition of the fact that such an assessment could and perhaps should be incorporated into the routine pre-development desk study, intrusive ground investigation and interpretative reporting process.

Investigation
When looking at investigation the application of photoionization detector (PID) screening is meaningless without further guidance. The “suitable survey pattern” is not defined and ignores the shortcomings of PID readings. The extent of suggested PID testing could also be onerous in most circumstance.

The soil sampling section refers to an unspecified “suitable survey pattern” which is easily confused with the PID screening.  Although it recommends the use of BS10175 for more detailed information on the design of a sampling plan no specific information on sampling for proposed services is included. It makes reference to taking “a spadeful” and the use of a “plastic bag” for samples which may be inappropriate and ignore the complexities of sampling.  Investigation and sampling are assumed to be undertaken via trial pits (likely to be machine dug to achieve the recommended depths) which would be difficult in an urban situation where numerous existing services are present and may not present the best method for obtaining the best samples, particularly for groundwater.  It suggests that if groundwater is present within 1m (or 2m in summer) of the base of the intended trench then a water sample should be taken from “a suitably completed narrow borehole” but establishing groundwater depth may be difficult.

Chemical Analysis
One of the most onerous parts of the recommendations is the imposition of a mandatory analytical suite to be undertaken on all samples.  Despite the fact that a desk study and ground investigation has been undertaken, including PID screening for VOCs, it appears that there is a limited choice for the user of the document in respect of what testing is required. The suite is far from routine with several determinands not generally carried out by any of the commercial laboratories in the UK on soils. To cover the lists as provided would probably cost in excess of £300 per sample.  Notably only organic contaminants are considered with the absence of inorganics such as arsenic.

Confusion extends to the proposed testing suites. The extended VOC suite (by GCMS) contains many non VOCs such as Benzo(a)pyrene and propylene glycol, explosives such as nitroglycerine and nitrotoluene (which are analysed by HPLC), Nitrohydrochloric acid (Aqua Regia a mixture of HCL and nitric acid which again cannot be analysed as a VOC) and Naphtha which is petroleum terminology for an ill defined distillate. There are misspelled chemicals such as “Mesityl” oxide and duplicated compounds such as methyl chloroform (which is 1,1,1 TCE) and Monochlorobenzene which is Chlorobenzene.

Other suites contain similar errors. Petroleum ether is incorrectly listed under ethers. Under mineral oil the document contains a turpenoid, a plasticiser, a flavour, a fatty acid and fuming sulphuric acid with no mention of mineral oil C5-C10, C11-C20 and C21-C40 listed in the “mandatory analytical suite”. A random list of chemicals is listed under Conductivity, Redox and pH including a vitamin, food preservatives and a range of compounds that would either not be found or could not be determined by routine analyses.

The simplistic approach to the determination of redox and resistivity in disturbed samples also causes some concern. This should at least reference BS 1377 Part 3:1990 and mention the benefits of in-situ measurements. Other soil conditions, not necessarily associated with a brownfield site, may also need to be examined for classification, for example “Wetness Class” which, although are not directly related to contamination, are used in the examination of sites for existing or proposed ductile iron pipes.

In relation to chemical testing reference is made to detection limits – but no discussion on how these limits were arrived at is included. These are set at “at least 10 times lower that the screening values identified” which appears to be arbitrary.

Specification of Water Supply Pipes
The final part of the document, as expected, relates to the process of specification of pipes.  It provides a comprehensive list of standards and guidance for each of the options including ductile iron, steel, polyethylene (PE), PE Barrier, PVC and copper.  Further undefined terms which will have a major effect on the specification are included such as “light chemical contamination”

Unfortunately some of the chemistry in this part is also misleading. It gives a conversion from EC to resistivity, which is not applicable to soils as it does not take into account natural moisture content, compaction, voids or the benefit of in-situ measurements.  Redox is used as a criteria without proper reference to BS1377 or acknowledging the problems likely to be encountered with disturbed samples.

Once all of the results of the extended testing have been received, individual chemicals are summed in groups, which appears to be highly questionable considering the differences between each of them.  Further mistakes are noted on the Pipe Selection Table 3.1, below which is provided to make a final selection, notably with disagreements between these figures and those in F.4 (Derivation of ‘data-supported threshold values’ for PE and PVC).  In this table there would be no requirement for any analysis if Barrier Pipe (PE-Al-PE) is used as it passes on all counts.  It is felt that the selection of barrier pipe for all sites will be a frequently exercised option as this is suitable for all conditions, it would also negate the need for any of the desk study, analysis, site assessment and pipe selection process covered in the rest of the document.  A statement that “barrier pipes should be used for all brownfield sites” would make the whole of this document redundant.

Pipe material

All threshold concentrations are in mg/kg

Parameter group

PE

PVC

Barrier pipe
(PE-Al-PE)

Wrapped Steel

Wrapped Ductile Iron

Copper
 

1

 Extended VOC suite by purge
and trap or head space
and GC-MS with TIC

0.5

0.125

Pass

Pass

Pass

Pass
1a + BTEX + MTBE

0.1

0.03

Pass

Pass

Pass

Pass
 

2

 SVOCs TIC by purge and trap or
head space
and GC-MS with TIC (aliphatic
and aromatic C5 – C10)

2

1.4

Pass

Pass

Pass

Pass
2e + Phenols

2

0.4

Pass

Pass

Pass

Pass
2f + Cresols and chlorinated
   phenols

2

0.04

Pass

Pass

Pass

Pass
3 Mineral oil C11-C20

10

Pass

Pass

Pass

Pass

Pass
4 Mineral oil C21-C40

500

Pass

Pass

Pass

Pass

Pass
 

5

 Corrosive (Conductivity, Redox
and pH)

Pass

Pass

Pass

Corrosive if pH < 7
and conductivity
> 400μS/cm

Corrosive if pH < 5 , Eh
not neutral and
conductivity > 400μS/cm

Corrosive if
pH < 5 or > 8
and Eh
positive
Specific suite identified as relevant following Site Investigation
2a Ethers

0.5

1

Pass

Pass

Pass

Pass
2b Nitrobenzene

0.5

0.4

Pass

Pass

Pass

Pass
2c Ketones

0.5

0.02

Pass

Pass

Pass

Pass
2d Aldehydes

0.5

0.02

Pass

Pass

Pass

Pass
6 Amines

Fail

Pass

Pass

Pass

Pass

Pass

Table 3.1: Pipe selection table

Conclusions

Although the document recommends a staged process of desk study, investigation, assessment and specification there are several areas where it is far from satisfactory.  Lack of suitable detail, ignorance of current guidance and an unwieldy and expensive approach to chemical analysis has made the process of selecting suitable pipe materials almost impossible.

Given the potential complexity and cost of the investigation and analysis to fulfil the requirements of the document it is likely that developers and specifiers will often take the simpler approach of always using barrier pipes in brownfield sites when there is any possibility of contamination.  This will be the case in most existing domestic plots and extensions (where the presence of a garage or garden shed would lead to the onerous investigation procedure) and may in turn lead to barrier pipes being unnecessarily specified.  It is also possible that the replacement of lead water pipes will be prevented by the higher costs caused by following this guidance.

We would recommend that the document goes through a further period of consultation including commercial laboratories, consultants and industry groups (such as EIC, NHBC and AGS).  The limitation of desk studies and PID screening should be added and more guidance and reference on the investigation, preparation of a conceptual model and provision of competent personnel given.  A more flexible approach to analysis should be taken, relating the testing to the previous site usage.  The selection process should also be made simpler, making the choice of other pipe materials more likely.

Article Contaminated Land Data Management

Water Pipes: a guide

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Tags: brownfield water

UKWIR (UK Water Industry Research) have recognised that with an increasing number of brownfield sites being used for development, it is important that appropriate water supply pipes are selected to provide long term protection to both water quality and the structural integrity of pipes. The focus of their project was the development of clear and concise procedures which provide consistency in the pipe selection decision process. Published data and water industry experience on the impacts of different contaminants on pipe materials have been used to provide guidance that can be used by relevant parties to ensure compliance with current regulations; and to prevent water supply pipelines failing prematurely due to the presence of contamination.

This guidance can be purchased from UKWIR for £50 by visiting: https://www.ukwir.org/report/90140/Water-Mains–Services–Leakage/90145/Pipeline-Technology/90146/Pipeline-Materials/93452/Guidance-for-the-Selection-of-Water-Supply-Pipes-to-be-used-in-Brownfield-Sites

The AGS Contaminated Land Working Group will be reviewing this document and invite any comments and observations to be sent to ags@ags.org.uk

Article Contaminated Land

Managing residual risks of land contamination

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Tags: brownfield environmental insurance

The successful trading, development and regeneration of brownfield sites requires stakeholders to acknowledge and manage environmental risks effectively to realise
the potential returns. Whilst many risks associated with the project require careful consideration, the management of environmental risks can have a profound effect on the success, or failure, of a development project. Get it “right” and the developer and investment partners can reap immense rewards. Get it “wrong” and environmental issues have the potential not only to jeopardise any financial gain on the project, but present long-term liabilities to those involved.

Of course, developers cannot simply adopt a “zero risk” attitude to environmental issues when it comes to brownfield sites, particularly given the current climate of increasing costs of landfilling. Avoiding sites with actual or perceived environmental
risks could result in missed opportunities as a result of deciding not to proceed with a purchase, however budgeting for overly stringent remedial standards during development can risk losing a site to a less conservative competitor. It is not only major regeneration schemes that require careful assessment. Arguably, the adoption of adequate risk management procedures is even more important for small brownfield sites, where margins will tend to be tighter.

Residual Risk and Uncertainty
The drive towards the use of “innovative” remediation techniques, particularly those involving the in-situ treatment of soil or groundwater pollution, brings with
it the need to address residual contamination risks.

The application of risk-based remediation criteria, whilst an entirely credible and practical solution for modern day brownfield site regeneration, is designed to reduce risks to acceptable levels based on the current status of scientific knowledge, legislation, and (perhaps even more importantly) enforcement practice. Predicting future trends in any one of these factors is prone to significant uncertainties. One only has to look at the progress made (or lack of it) on Soil Guideline Values in recent years, and the Water Framework Directive to realise that this is an area ripe for changes in enforcement practice, raising the spectre of cases being re-opened some years after remedial works have been “signed off” by regulators.

Developers will, understandably, want to realise a profit on their investment as quickly as possible, and will therefore tend to have a relatively short-term interest in a site. Long-tail liabilities associated with residual contamination will therefore typically not be of primary concern. However, other stakeholders such as investors,
lenders and sellers (particularly if the latter are the original polluter) may seek additional safeguards to protect themselves in the event that environmental risks are not entirely addressed through remediation. In many cases, it may be merely the perception of environmental risk, rather than specific risk factors that cause concern.

Solutions
The increasing availability of fixed price remediation contracts may seem to be the perfect panacea for developers looking to avoid the risk of cost-overrun. But what happens if additional contamination is found that falls outside the scope of the contract, either during or after completion of the remedial works?

The first reaction may be to try to take action against the environmental consultant or contractor responsible for designing and implementing the remediation scheme. This is unlikely to be successful, unless either party has been clearly negligent, or the
engineered solution has failed within the warranty period. General liability and property insurance policies will almost certainly offer no protection from ongoing ground contamination liabilities. By contrast, environmental insurance can offer a
cost effective solution to residual contamination risks.

Environmental insurance policies cover statutory clean-up requirements, third party claims for bodily injury and property damage, and associated legal expenses, resulting from contamination. The environmental market has softened in recent years, largely through increased competition, resulting in premium levels being approximately half what they were three years ago for comparable risks. Price is not everything of course, but there is also greater potential to secure coverage enhancements now than in previous years.

Whilst policies can be placed quickly and efficiently, it is important to use a specialist broker who is familiar with insurance market, policy wording and to ensure that any policy placed is tailored to meet the specific needs of the Client and project.

Do Claims Succeed?
In short, yes. Environmental insurance is a relatively
young insurance market, nonetheless we are seeing a maturing claims experience in the UK and elsewhere. During a recent survey by Willis, environmental insurers
indicated that up to 1 in 10 policies see claims activity, a trend that most insurers agree is increasing, both in terms of the frequency and magnitude of loss.

Case Study 1
A car dealership relocated one of its showrooms, with the intention of selling the site for residential development. Following the discovery of a widespread plume of petrol contamination caused by a petrol filling station formerly located at the site, remedial plans were prepared in agreement with the regulators. The petrol plume affected an
underlying aquifer, and also extended beneath surrounding residential properties.

The risk assessment reduced the uncertainty to a level that the developer was willing to take on the risk of funding the remediation works, in return for a purchase price reduction. Although there was general confidence that the remedial works would be successful in reducing both the risk and uncertainty the developer was concerned that the residual risk exposure could be significant, particularly as they were required to indemnify the seller. The developer therefore purchased environmental insurance to safeguard against the possibility of future additional clean-up costs or third party
claims following completion of the remediation, for example as a result of “rebound” of the plume or future health impacts caused by inhalation of petrol vapours by residents.

Case Study 2
This illustrates a recent example where liabilities of residual contamination, the costs of which ran into six figures, were successfully claimed on an environmental insurance policy.

A landowner implemented remedial works following the discovery of hydrocarbon contamination beneath their site. The original polluter had ceased trading some years earlier, leaving the current owner liable for the remediation, which was planned and undertaken with the agreement of the regulators.  Upon commencement of the works, the landowner also took out an environmental insurance policy to cover
the possibility of additional future clean-up works being required as a result of unidentified contamination being present beneath the site. Due to site access constraints, it had not initially been possible to investigate in all areas.

The remediation achieved the required target, and was duly “signed off” by the regulators, upon which the environmental insurer was obliged to provide for any further “on-site” clean-up costs under the policy terms. Following this, additional
contamination was identified which required further remediation, the costs of which were met by the environmental insurance policy.

For more information or to discuss other environmental risk transfer solutions, please contact

Fiona Gray
Willis Environmental Practice
Tel: +44 (0)207 488 8111
grayf@willis.com

Ten Trinity Square
London EC3P 3AX
www.willis.com

Willis Limited, Registered number: 181116 England and Wales. Registered address: Ten Trinity Square, London EC3P 3AX. A Lloyd’s Broker. Authorised and regulated by the Financial Services Authority.

Article Uncategorized Contaminated Land Loss Prevention

SITE INVESTIGATION SHOULD BE FOR CONCRETE DURABILITY IN ADDITION TO SOIL STRENGTH PARAMETERS

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Tags: brownfield concrete foundations Site Investigation

All too often Site Investigation work is seen solely to provide soil strength parameters to enable economical foundation design. There is a need for the site investigation industry to make clients more aware that the aggressive nature of the ground should also be accurately determined if adequate precautions are to be taken in the design of a durable concrete for use in the foundations.

The problems associated with the thaumasite form of sulfate attack (TSA) have been well documented and in August 2001 BRE Special Digest 1 was published. Part 1 of the digest is particularly relevant to the site investigation industry. Without the necessary soil and ground water testing to determine the extent of those aggressive chemicals present at a particular site the concrete cannot be designed in accordance with best practice. It is where possible beneficial to have results from both groundwater and soil samples.

Many Site Investigation reports are issued without fundamental site-related parameters to enable the adequate design of the concrete.

The site assessment procedures should vary depending on whether the site can be defined as natural ground, brownfield containing industrial wastes or pyritic ground, reference to BRE Special Digest 1 should be made for full details.

In general it will be necessary to determine the water soluble sulfate in 2:1 water/soil extracts and the pH in 2.5:1 water/soil extracts. Many Site Investigations where they report any chemical testing only show an occasional soluble sulfate result which is often inadequate to determine the Design Classification for the concrete mix. Where the sulfate in the soil extract exceeds 3.7 g/l SO4 or in the groundwater sample exceeds 3.0 g/l SO4 it is necessary to also determine the Magnesium content. The mobility or otherwise of the groundwater on site also has an affect and should be established.

Where a site is brownfield it will generally be necessary to obtain the Chloride and Nitrate content in both the soil and groundwater samples if the aggressive chemical environment for the concrete is to be accurately determined. Where Pyritic ground conditions are anticipated more substantive testing is required to enable the total potential Sulfate and hence the concrete design requirements to be determined, for full details reference should be made to BRE Special Digest 1.

It should be apparent from the above that greater consideration needs to be given to determining the aggressive chemical environment at the site investigation stage than is currently the case, to determine site-related parameters for strength in one site investigation and then undertake further work at a later date to enable the Aggressive Chemical Environment for Concrete to be determined is no way for the industry to improve its standards or its advice to clients.

It should also be noted that BRE Special Digest 1 has superseded BRE 363.

D.Brightman Technical Manager, Rock & Alluvium