A Rig (or Two) and a Prayer

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It’s not often we have two of our rigs working on the same site together, but this week we needed to do just that.
Our client had originally requested a plate bearing test to determine the bearing capacity of the underlying geology for a new extension to their mosque.
We advised that a plate bearing tests was not the right test. Instead , using our Geoprobe DirectPush and Terrier percussive drill rigs, we were able to complete soil sampling, dynamic probing and SPTs in the chalk underlying the site. These data then allowed us calculate the ultimate bearing capacity for future foundation design.

If This Doesn’t take the Daffodil….

A recent project in Wales saw us drilling through Coal Measures. We encountered mudstone, ironstone, siltstone, sandstone, claystone and, of course, coal….all in a single day. This didn’t stop us achieving 100% core recovery and 20m+ coring a day, all with full gas monitoring.

For more information or to get a quote for us to drill your site (it doesn’t have to be in Wales!) please contact Angus Gale – 0774 8358304

Practical (Geotechnical) Magic

We were called to the rescue of a local home owner recently. They had been told, by both Building Control and their builder, that they needed to make substantial improvements to their existing foundations in order to be able to add a first floor extension to their property. The existing foundations had been signed off by Building Control, a number of years previously, but were considered insufficiently deep and wide to support the additional loads of the proposed extension.

To add to the problem, the existing foundations were off-set from the line of the existing walls, but there was no indication to suggest they would be inadequate. When we asked what information Building Control had used to reach their conclusion all we got in response was ‘it’s just not what we usually see’. We thought we could (and should) do a little better than that…

Given our knowledge of the local geology, we knew the property was likely to sit directly onto the bedrock chalk, which being ‘rock’ is usually pretty strong (maybe the clue is in the name?). We carried out some low-cost field tests adjacent to the existing foundations and used these data to complete an evidence-based geotechnical design. We then worked with the project’s structural engineer to confirm that the existing foundations were more than adequate to support the new loads.

The cost of carrying out the testing and subsequent report was less than 10% of the cost of the previously proposed ‘necessary improvement works’. Not only that, they yielded a significant time saving. A win the for the client and a win for us – sometimes it’s just nice to be on the right side of common sense.

Hedging Your Bets?

Can You Spot Our Drill Rig?

When a client rang and said they needed boreholes in a densely overgrown area, located up a high-sided kerb behind some hedges, we knew we had just the drill rig for the job. After checking for below-ground utilities, we completed seven boreholes locations to 4m depth in a single day. Naturally, we left the site clean and tidy, with a happy client.

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.

Leaks and Spills

Tank with Corrosion Hole

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.

‘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.

You Never Know….

Buried Services

…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

When Your Protection Fails….

Overdrilling CP

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.

Heathrow Third Runway

Night Working at Heathrow

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