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Accuracy v Precision

We live in an age dominated by IT and its ability to crunch data. Without doubt this can yield significant benefits, but do we sometimes lose sight of reality as a result?

We were recently asked by a regulator to supply CBR results to two decimal places. Now, we can calculate data to any number of decimal places using the IT tools available to us, but just because we can doesn’t mean we should. Anyone familaiar with CBR testing will know that the test just isn’t that accurate. Quoting a CBR result to the nearest 0.1% might (just) be realistic for soft/loose materials. But quoting a result to the nearest 0.01% implies an accuracy that just isn’t warranted. The precision of the answer isn’t justified by the accuracy of the test.

So this is a plea for regulators (and anyone else for that matter) to apply a little common sense, and to remember the difference between accuracy and precision.

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It’s What You Can’t See….

Spot The Buried Tank!

We were asked to carry out an environmental ground investigation at a disused transport depot. Not surprisingly this identified diesel contamination at ~2m below ground level.

There was no sign of any obvious contamination source and given the site’s previuous use as a transport depot, we thought it likely that an abandoned below ground fuel tank might be present.

We therefore went back to the site and carried out a shallow trial pitting exercise which revealed……well, you can see for yourself.

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A Draining Holiday?

It’s the holiday season and, if you’re about to head off for a week or two of bliss in the sunshine with the family, spare a thought for our field services teams. When we asked them if they fancied a midweek stay in a caravan park, they jumped at the chance. We might have omitted to tell them that they’d be busy all day completing soakaway testing for an extension to the caravan park.

Being the good sports that they are they completed four tests, all in accordance with BRE365, and our detailed report was issued to the client the following day.

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Making a Splash

With warmer weather arriving, we received a timely request from Micasa to assist them with the design and construction of a swimming pool for a residential client. All in a day’s work for our Terrier drill rig, which is particularly suited to this work, having a small footprint and being able to pass through a standard doorway. The only problem: our site team were left imagining taking a refreshing dip in the pool, which won’t be completed for a few months yet.

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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.

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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

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Fame and Fortune

The APEA recently featured an interview with our very own James Edley. If you’d like to read James’ view on recent developments in the world of geo-environmental consultancy then please click on this link.

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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.

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Pot of Gold

They say there is a pot of gold at the end of every rainbow.

We aren’t sure our Geoprobe drillrig qualifies as that, but we liked the photo and thought we’d share it.

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We Never Sleep

The nights are drawing in and daylight is at a premium. This can limit the hours available for sitework. Or rather it could until recently. We’ve just completed a four week long refit and refurbishment of our drill rigs. This has included fitting task lighting ensuring that we can work long into the night – or even all night of the job requires it.

For more information please contact Angus Gale – 07748358304