Construction – Page 3

12 October, 2018

Hollow Stem Augers

Up Close and Personal – The Business End of a Hollow Stem Auger

The site investigation industry has, traditionally, relied on light cable percussion (generally known as shell and auger) drilling. This is slow, messy and crude providing low quality geotechnical and environmental samples at best. Thankfully, these days it isn’t the only option available to you.
The majority of our general site investigation drilling is done using hollow stem rotary methods. These provide signficantly better quality data with minimal sample disturbance, even in the toughest of conditions. This week we were working at a site underlain by glacial and millstone grit cobbles, sand and terrace gravels in a sandy clay matrix. We drilled five boreholes to their target depth on 8m in one working day – something that might have taken a shell and auger crew a week – minimising the disruption to our client’s business which was able to remain open throughout.

12 October, 201812 October, 2018

Leaks and Spills

We’ve recently started the first phase of our latest remediation project: the redevelopment of a former petrol station site located in a highly environmentally sensitive location.
Stage one of our work comprised identifying and removing the source of the contamination. As you can see, we are pretty confident that we found the root-cause , although we have to wonder how the former site operator didn’t know something was wrong with this tank.
We’re currently working to design and integrate our groundwater treatment system with the construction work to ensure that there are no delays to the redevelopment.

2 October, 20183 October, 2018

‘Sump’thing in the Ground

Excavation with Services Exposed and Sump Installed

Remediation is always challenging, but it’s made much harder when we are asked to do it at a busy filling station which needed to remain open throughout our works. Having previously determined that the contamination was confined to a relatively thin layer of gravel but was migrating offsite, we decided to install some small diameter sumps across the site in preparation for a programme of ISCO (treatment using in situ chemical oxidation).

Fitting the sumps between buried services was always going to be tricky, so we pre-excavated each location using vacuum drilling techniques. As you can see from the photographs, it was a good job that we did, with numerous pipes and ducts exposed (and duly avoided).

The excavation has now been backfilled and the pavement reinstated, leaving us with a small manhole cover to provide access to our sump when we return to start treating the ground. The filling station remained open throughout our works.

13 August, 201825 September, 2018

You Never Know….

…what lies beneath your feet. But when it comes to carrying out any form of ground investigation or excavation work, it’s imperative to find out whether there are any buried pipes or cables before you start work.

We provide consultants and contractors with the information they require, whether it’s a complete set of public utility drawings or a remote sensing survey using radio detection and ground probing radar.

For more information, please contact Angus Gale – 01296 739333

8 August, 2018

When Your Protection Fails….

Not that kind of protection! We’re talking about cathodic protection of fuel pipes and tanks.

Decommissioning and replacing defunct cathodic protection ground beds requires an element of precision and brute force. Our first job is usually locating the existing beds. This can be no small task on a 30 hectare oil terminal site! The redundant beds were installed over 30 years ago and records are sparse.

We used radio detection methods to accurately locate the old redundant vertical ground beds to the required accuracy of +/-50mm. We need to be that accurate in order to successfully overdrill the beds.
Unusually, on our most recent project, our client asked us to drill through the connecting cables rather than removing them. The cables were isolated by a field engineer prior to us starting work and all our works were carried out under a permit to dig.
To overdrill the existing beds we brought in a shell and auger rig, drilling 350mm boreholes to 5m depth. This effectively decommissioned the existing redundant ground beds to make way for the new ones. With the first stage of the project complete, we are now back on site with our Comacchio rotary rig drilling much deeper boreholes in which we will be installing new anodes. Updates to follow.

6 July, 2018

Heathrow Third Runway

OK so we can’t say whether this will (or should) get the final go ahead from government. But what we can say with absolute confidence is that we have more experience of working airside at Heathrow than any other geo-environmental consultant.

We are the only consultant with permanent airside passes, both for our staff and our vehicles. We are also well versed in navigating our way through the airport’s complicated permiting system.

Just last week one of our investigation teams worked through the night to install several deep monitoring wells adjacent to one of the existing runways. The third runway will need thousands of similar geotechnical borehole drilling in the next few years. We believe that having an airside presence and an in depth knowledge of the geology gives us a head start when it comes to providing this service.

For more information please contact James Skinner – 01296 739411

6 July, 2018

The Good Old Days

We recently came across this advice in a 1960s ‘How To’ manual.

We think the Environment Agency might have something to say if anyone advised this now. But it is typical (albeit on a small scale) of many of the less enlightened environmental practices from earlier times.

This goes some way to explaining why so much of our brownfield land is contaminated in one way or another. With soil and groundwater clean-up costs increasing all the time, it also points up how foolish it is to buy brownfield land without first checking on its condition.

If you’d like to know more about our geo-environmental site investigation capabilities or if you have land that requires treatment, then please contact Duncan Eastland – 01296 739431.

6 July, 2018

Cathodic Protection

Drilling large diameter boreholes at a brownfield site to install anodes for a cathodic protection system requires a rather eclectic combination of skills.

Working in a tight space, to a detailed specification, we achieved an anode installation through a complex sequence of geological strata. Clean drilling techniques required us to install an environmental seal through surficial gravels and 30m into underlying clay. We then extended the boreholes through 20m of Thanet sands and 10m of flinty chalk. To complete the anode installation we then tremmied sacrificial coke contact media into the borehole’s response zone with the remainder of the boreholes being grouted back to the surface with bentonite.

Our team consisted of drillers, environmental engineers, mud technicians and cathodic protection engineers, all working together on a busy site to ensure the client got the installation required whilst working within the Environment Agency guidelines. The anodes will now ensure the pipelines are protected for the next 100 years.

If you’d like to know more or if you have an installation requiring cathodic protection be installed then please contact Angus Gale – 01296739433

28 June, 201825 September, 2018

Tight Fit?

When it comes to sites that have narrow or restricted access, we reckon that there is no better drill rig than our Terrier. It may be the baby of our drilling fleet, but don’t let its diminutive size fool you.

In the past year it has worked in basements, narrow side passages between houses, amid demolition debris and in a host of other conditions that would have precluded larger rigs being used.

If you add in the fact that it can work on inclines as steep as 30 degrees I think you’ll agree that our Terrier is a little gem.

This week we’ve been using the Terrier to carry out post-demolition verification sampling. We’ve been able to pick our way through the demolition rubble, getting access to the entire site to drill a pattern of boreholes to 5m depth.

For further information, or to discuss your drilling requirements, please contact Angus Gale – 01296 739433

25 June, 201828 June, 2018

Northern Powerhouse?

We like to feel that we’re contributing to the Northern Powerhouse and this week saw us working in Manchester on a project to construct student accomodation in the city centre. Our role was to clear locations of buried obstructions prior to piling commencing.

We successfully cleared 30 locations to 8m depth in a single day – a total of over 250m linear metres of pile probing. With the piling rig arriving the following day, the result was a happy client.

The fact Manchester was enjoying its warmest day of the year so far was a pure coincidence, though it was a welcome surprise not to get wet*!

For more information or to get a quote for pile probing at your site, please contact Steven Partridge – 01296 739413

[* The editor used to live in Manchester]