Zetica - e-news
December 2010 Volume 7, Number 2

In this issue

Useful Links & Recent Publications:

Benefits of routine ballast inspection using ZARR
White paper January 2009

Limits of detection of unexploded ordnance - are you getting what you paid for?
White paper on physical limits of detection for surface- and borehole-based geophysical methods

Solution matrix for road or motorway applications
The US Federal Highways Dept has published a very useful matrix of geophysical and NDT methods for solving engineering problems during SI, construction and maintenance of road infrastructure.

WW2 bomb risk maps
Download risk maps for your region
WW2 bomb risk maps image

Measuring the risk of detonating unexploded bombs
Web-based applet to allow users to input parameters and calculate an order of magnitude risk of detonation

Limits of detection of unexploded ordnance - are you getting what you paid for?
White paper on physical limits of detection for surface- and borehole-based geophysical methods

Statistical assessment of the risk of unexploded bombs
Paper published in Ground Engineering, May 2006

The value of an independent desk study
Recent article by Zetica's Managing Director, Mike Sainsbury, in Geodrilling, highlighting the pitfalls of saving pennies on a desk study only to run the risk of spending thousand's of pounds more than necessary on UXO risk mitigation.

2010 in a paragraph

It is a good time to be an engineering geophysics and topographic mapping service provider. Although construction projects slowed during the first half of this year, they picked up significantly during the last quarter. We have seen a surge in our bomb risk map downloads – normally a sign that planning for developments is on the increase. The last quarter of this year has delivered our strongest ever performance with international assignments underpinning UK-wide transport and energy infrastructure projects. This is fuelling new research and development projects some of which will bear fruit in 2011. We merged with BW Surveying to enhance our mapping service portfolio and recruited 5 staff members. We have also made significant investments in new hardware to meet the growing demand.

We wish all our customers and colleagues a festive holiday season and a very happy new year.

SiteSafe

Over the last year, it has been satisfying to see increasing recognition of our SiteSafe Unexploded Ordnance (UXO) services and in particular our objective approach with respect to identifying and mitigating the risk of potential UXO hazards.  A growing number of customers are moving away from using UXO specialists with a more traditional Explosive Ordnance Disposal (EOD) background and turning to Zetica for objective advice on how to address the actual potential UXO hazard that may exist on a site.

Customers are starting to question the quality of 3rd party desk studies and risk assessments they receive and the subsequent recommendations for any risk mitigation surveys.  You get what you pay for.  Why do so many desk studies recommend extensive risk mitigation measures when records show no apparent UXO hazards? The desk study may come cheap but the follow-on actions can be expensive and worse, a wasted expenditure. Zetica’s research team has set the standard for objective risk assessments underpinned by thorough research. Our advice is “don’t cut corners”.

With one customer stating that the report he received from us was ‘the best survey report I have read in a while’, we must be getting something right!

New UXB risk Maps for London

An update to our set of UXB risk maps for London is due in early 2011. Many of you are probably already familiar with the existing set of maps for London and the rest of the UK.  The updated London maps will not only identify the overall UXB hazard giving you the initial information required for a preliminary desk study (as per CIRIA Guidance C681), but also indicate the likelihood that risk mitigation (such as MagCone or MagDrill-Plus) will be required for typical site activities such as bulk excavation or piling. 

The new maps will also provide a guide as to whether MagCone or MagDrill-Plus is appropriate for sites where a UXB risk has been identified for deeper works such as piling.  It is critical to get this right in order to ensure that sufficient depth of detection is obtained and that the most cost effective technique is used. For example, using MagCone in gravels will usually mean that the MagCone probe will refuse at depths much shallower than a bomb can penetrate. If you use our web-based UXB depth calculator you will see that a 500kg bomb will penetrate to 6.0m in gravel.  If you use MagCone in this scenario, you may not be clearing your piles properly!

Making UXO surveys safer

Another key issue we will be addressing in the next year is the limits of detection for UXO surveys.  This is a very contentious issue which has potentially serious safety implications.  Too many companies are exaggerating the detection limits of their surveys to provide a more competitive price.  The greater the detection limit, the smaller the number of tests required and so the lower the price.  But the stated detection distances are often far in excess of both the theoretical and practical limits. In many cases this means at best, the number of anomalies requiring investigation increases dramatically, or worse the clearance certificate issued is not worth the paper it is written on, making any subsequent construction work potentially unsafe.

Over the next year, we plan to make the whole industry further aware of this and similar issues to help customers ensure they procure the services appropriate to their requirements. 

New SiteSafe Alliance partner

We are delighted to welcome Ramora UK Limited to the SiteSafe Alliance. Ramora join Vinci (drilling), Lankelma (Magcone) and Zetica (desk studies and detection) to offer one of the UK’s largest and most cost effective UXO risk mitigation resource ranging from risk assessments right through to disposal.

Ramora have the appropriate licences, insurances and expertise to undertake Explosive Ordnance Disposal (EOD) work in the UK.

What does the SiteSafe Alliance offer that is unique to the market?

  • Independent advice on UXO risk – none of the partners are dependent on follow-on work for their survival
  • Vinci has one of the largest drilling contractors in the UK
  • Lankelma has the largest CPT fleet in the UK
  • Zetica has a dedicated research team to undertake UXO risk assessments
  • Zetica has one of the largest engineering geophysical team available in the UK and is the only contractor who publishes articles on issues such as limits of detection
  • Zetica offers highly experienced Explosive Ordnance Contractor expertise for watching briefs and target identification
  • Ramora provide Explosive Ordnance Disposal services

If you contract any of the SiteSafe Alliance partners you are buying into our collective ethic of providing impartial advice and industry-leading technical solutions sustained by a resource pool second to none.

Utilities

Zetica has had a record-breaking year providing various levels of utilities detection and mapping services for a range of clients. Our recommendation to formally decide on a level of service required by either following the TSA or ACE guidelines has been very well received by customers. Our range of assignments include a 9 month project mapping buried services and structures as part of the major Reading Station upgrade works as well as numerous borehole clearance tasks.

Topography

Zetica’s surveying team have also been very busy undertaking a wide range of surveying projects for a variety of customers, as well as supporting other Zetica projects.  Typical surveys conducted in recent months include measured building surveys, topographic surveys and detailed structure surveys of bridges and other structures. The survey team have also undertaken settlement monitoring of rail structures as part of the CrossRail project.  These have required sub-millimetre accuracy requiring the considerable skills and experience of our team.

Borehole seismics – case study

Each of our eNewsletters contains a case study which is aimed at raising awareness of an application or technical issue. This edition highlights the use of crosshole seismics. Although clear guidelines are available in the latest version of the ASTM standard for crosshole seismic testing: D4428/D4428M – 07, this is not always strictly adhered to by contractors. We draw attention here to the need to go beyond simply picking first arrival times and deriving apparent velocities from the assumed linear distance the seismic wave has travelled. Where sudden changes in velocity occur at material boundaries, Snell’s Law of Refraction must be applied to deal with non-straight line wave paths in order to derive actual velocities (which may significantly vary from apparent velocities).

A crosshole seismic survey was recently carried out in the Midlands, UK, using Zetica’s latest orientable 3-component borehole geophones and a borehole sparker source in boreholes separated by about 5m, prepared by Vinci. Zetica also carried out a verticality survey to measure the actual 3D location of each source-receiver combination.

Figure 1 shows an example composite wiggle trace plot with source-receiver depth along the x-axis and measurement time along the y-axis. Two records with the shear wave sparker source firing in opposite directions are overlaid at each position. Clear evidence of P-waves (green) and shear waves (red) is shown.

Figure 1

Figure 1

Figure 2a shows the measured (apparent) velocities in red with the modelled actual velocities shown as a dashed black line. Figure 2b shows the resulting modelled travel times as a dashed black line compared with the measured travel times. Arrows indicate the two measurements refracted at the modelled velocity boundary which, if ignored, would give erroneous velocities.

Figure 2a

Figure 2a

Figure 2b

  Figure 2b

Zetica Rail

Zetica Rail is fast expanding with ongoing contracts as far afield as Australia, South America and the USA. Our dedicated website has the latest white paper entitled: “Practical applications of GPR surveys for trackbed characterisation in the UK, Ireland, USA and Australia” available for download. Click here to download our flyer on the RASC – Railway Asset Scanning Car. The range of deliverables available from a single survey of track is impressive.

Top Tip

Earlier this year Zetica commenced with a monthly series of short tips on making the most effective use of geophysical techniques to solve underground mapping objectives. We’ve allowed ourselves to slip on the monthly schedule due in part to workload but also a muted response from customers. Is this of any interest? Click here to register your interest or just leave a comment.

Twitter highlights

If your bosses won’t allow you access to Twitter, why not access in private? You’ll stand out a mile with knowledge of developments and events that may take weeks to emerge through the traditional media (if at all). For followers you’ll be interested to know that Mike Sainsbury is responsible for tweeting on SiteSafe topics, Brian Barrett on general geophysics related themes and Asger Eriksen on rail matters.

Some of Mike’s tweet highlights over the past few months include:

  • Details of the 500kg WWII UXB we found in Essex are included in this months GeoDrilling. See https://bit.ly/bzgYFf  May 27
  • One of our teams has been investigating a former #SOE site today. The site was used to develop weapons such as exploding rats during WWII. Jun 21
  • A competitors preliminary desk study concluded there may be a risk of UXB on a London site. What a waste of time/money! https://bit.ly/azpv9I  Aug 3 
  • Just reviewed 3 competitors desk studies, all identified sites were not bombed but each recommended extensive #UXB #detection surveys! Why? Aug 24

Selected highlights from Brian’s highly entertaining tweets include:

And if you are keen on rail here are some recent tweets:

  • Another ZARR survey completed in Australia - over 3,500 rail radar km's of data safely in the bag with follow-up sites targetted within days. Nov 27
  • Read about the deformation to a railway line where it crossed a fault responsible for the Canterbury Earthquake https://bit.ly/9VEZgJ. Nov 3
  • https://bit.ly/91D9YC warns that Britain’s railway embankments and cuttings could be susceptible to landslides as a result of climate change. Oct 26

To join check out:
www.twitter.com/zeticaltd  (for information on general uses of geophysics to map buried features and monitor structures and related news from across the world)
www.twitter.com/zeticasitesafe (for information on managing the risk of UXO)
www.twitter.com/zeticarail (for news on trackbed maintenance related topics from around the world)

Contact Us:
Zetica logo

www.zetica.com
info@zetica.com
Tel: 01993-886682

CEO:
Asger Eriksen

Managing Director:
Mike Sainsbury

Copyright 2010

Field Geophysics (4th Edition)

Watch out for the release in January 2011 of the latest edition of this handy, pocket-sized field geophysics guide which has been co-authored by one of our very own.

The Fourth Edition includes comprehensive updates on the use of GPR and GPS and new sections on surface wave seismics and towed array systems. This has become the standard text in this area for use in the field and has been fully revised and updated to incorporate new developments in the field including a focus on quality control of the acquisition of data and basic field interpretation. Additional material will be available soon on the companion website at www.wiley.com/go/milsom/geophysics4e.

Order your copy now from here.