We are accustomed to working for the big hitters of modern industry. However, today we were handed the opportunity of working around one of the big hitters from history. This WWII machine gun bunker holds listed status, and rightly so. It’s one of 18,000 built, around the coastal areas of the UK during Churchill’s defence against Operation Sea Lion.
Our plucky little rig was able to negotiate perimeter fencing, dense undergrowth, steep inclines, tank traps and machine gun bunkers just to get on site. It all sounds more “Band of Brothers” than “geotechnical site investigation”. In all 28m of dynamic windowless sampling with SPTs (and 2″installs) plus 80m of dynamic probing were effortless completed.
A prominent pipeline client came to us with a problem. A ‘positive’ problem that is. A section of their pipeline runs underground next to a railway line. The railway’s overhead high voltage power lines were causing an amplified positive electrode potential in the ground, which in turn was leading to increased corrosion of their pipeline. In these cases, cathodic protection is the usual solution.
A typical cathodic protection system would comprise a series of shallow earthing rods installed at regular intervals along the pipeline. However, this requires access for maintenance in the future to the entire pipeline. But these pipelines run for hundreds of miles through agricultural land, some of which is only accessible during certain periods of the year. The solution was to design a single anode string capable of achieving the required negative electrode potential in a vertical design. Thus saving on space, maintenance and cost
The client’s senior cathodic protection engineer approached us to see if we could drill a 75m deep borehole and undertake the (negative) anode installation. We took the challenge and set about devising a safe method for installing a multi core anode string weighing more than 300kg! The borehole was installed through 18m of gravel into underlying mudstone. Just to complicate matters further, our environmental appraisal identified a potential risk of penetrating into a sandstone aquifer beneath the mudstone. To mitigate these risks and achieve the required potential we had to install a vent pipe to the base of the borehole, a tonne of coke, gravel and a bentonite seal at the top of the mudstone to ensure the underlying aquifer was protected.
Exactly how we did all this is our secret but needless to say it involved a large rig, and unusually for us, a lot of “negativity” ………….But happy pipeline equals happy client – now that’s positive.
As the rest of the world turns it attention to Hollywood and the Oscars, we’ve been focused on the only marginally less high-profile What House Awards. One of our clients, Q Developments, picked up two awards, one of which was for their development of a former filling station site in Teddington. We’re very proud to be able to say that we played our part in this project for Q Developments, having undertaken the decommissioning and removing the former petroleum installation and the treatment of hydrocarbon and asbestos-related soil contamination prior to the site’s residential redevelopment. Our congratulations to Q Developments on their award.
……is our mini dynamic sampling rig! In fact, its photographed here having its oil checked during a day’s work at a site on the south coast.
The geotechnical survey, which comprised standard penetrations tests (SPTs), dynamic probing, CBR tests and plate bearing tests, was designed to allow the design of foundations for a leading supermarket chain’s new store.
The site had a history of industrial development so, not surprisingly, it was littered with large, buried concrete obstructions from previous structures (foundations, beams and piles). We will soon be returning to complete pile probing at each of the new pile locations to enable the augers of the piling machines to keep turning thus avoiding expensive standing time.
Hopefully it will have stopped raining by then…..and no, sadly, we didn’t find the pot of gold at the end of the rainbow.
We are used to dealing with potential contaminants from a wide range of industrial sources. Our specialist risk assessment department employs a number of modelling techniques to determine what potential long-term risks could be posed to human health or environmental receptors. But in a slight change to the norm, we’ve recently completed a risk assessment to determine the potential risks posed by a lack of human health!
We were commissioned to assess the suitability of a plot of land for a potential future cemetery. A combination of desk-based research, borehole investigations using our Terrier drill rig and fascinating (!) mass flux/fate transport calculations were used to complete the assessment following Environment Agency guidance.
If you’d like to commission a quantitative risk assessment – either for the living or the dead – then we’d be delighted to assist you. Please contact our risk assessment team for more information.
No-one can say that our workload isn’t varied. Last week one of our drilling crews completed the following schedule:
Monday – Geotechnical investigation including U100 sampling and SPT testing with our Terrier drill rig;
Tuesday – Water well installation using rotary rock roller with our Commachio 205;
Wednesday – Environmental investigation at a filling station using hollow stem augering, again with our Comacchio 205, while a new canopy was being installed;
Thursday and Friday – Deep water well installation using down the hole hammer to penetrate into a limestone aquifer.
We love a bit of variety in life and this week has proved it so. Time for a rest…….next week looks busy………
Ok, that claim may be stretching things a little, but our forensic analysis team have recently notched up a few notable successes. We were awarded a contract to treat petrol and diesel contamination in the soil and groundwater under a filling station. The site had a history of leaks, the most recent of which was six years ago. Since then one of our competitors had been trying (and failing) to clean the site up.
We were brought in to deal with the contamination once and for all. The first thing we did was to carry out some forensic analysis of the contamination using proprietary methods we have developed over the last 20 years. Our analysis indicated that there was an ongoing leak at the site, and was even able to pinpoint where on the site it was likely to be.
Our client commissioned precision tank and line testing which confirmed a slow leak under pump island 7 – just where we had predicted. The rate of leak – 0.29litres/hour – was actually below the precision testing threshold, meaning that the fuel lines passed the test and were certified as ‘not leaking’. However, this rate of leak would result in around 2,500litres of fuel entering the ground under the site each year – more than enough to cause serious contamination.
So the lessons learnt? Firstly, tank and line testing is very far from foolproof and fails to identify leaks that can cause serious environmental issues. Secondly, the timely use of forensic analysis can prevent significant time and money being wasted on ineffective remediation work.
For further information on our forensic analysis capabilities please contact Duncan Eastland or Kate Clark.
Actually, there is nothing mythical about Subadra being commissioned to install shallow monitoring wells at the Daedalus Airfield Development! We constructed several shallow wells over the course of two days using our Hollow Stem Auger drilling system.
Lee-on-Solent is known for its sand and a dense gravels which are more or less guaranteed to make drilling difficult. So to avoid this we used our powerful Comacchio drilling rig which ensure we reached the target depth at all the drilling locations with minimal disruption to the site. We then installed 50mm diameter wells to allow future groundwater sampling. All our materials were sourced locally to enable us to take the minimum of equipment and vehicles thus reducing our carbon footprint for the works.
We even had time to the collect soil samples for the Principal Contractor and get them
analysed for WAC by our in house lab facility. As a result of our prompt and efficient service the client retained us to carry out a more detailed geotechnical investigation at the site. No myth there then!
The combination of restricted head room and a ‘confined space’ presents major obstacles to any site investigation. However, our Terrier rig was able to gain access and complete a geo-environmental investigation in such a space. Its quite amazing where this little rig can get.
Access was through a standard doorway working with an overhead ceiling clearance of
less than 30mm with the machine set up. Precision operation was required to ensure we completed five boreholes, each to 6 metres in depth, with SPTs every metre, all in a safe and efficient manner.
The nature of the confined space meant that exhaust gases from the Terrier’s engine had to be vented to an outside area. We used an extendable sectional exhaust pipe to ensure a safe working environment. But just in case we also carried out carbon monoxide monitoring to ensure our crew’s safety.
Even better, our work was completed without the need to close the car repair workshop we were working in. allowing our client to continue panel bashing, filling and spraying to his hearts content.
Have you ever wondered what is below your feet when you’re filling up at a petrol station? Big old tanks, that’s what! We’ve investigated the ground at more filling stations in the UK than anyone else and so, not surprisingly, we have a have a pretty detailed understanding of how they are put together. This sort of experience is invaluable when
it comes to assessing potential environmental risk – we know how and where problems
can occur…
Obviously owning our own specialist drilling systems, UKAS and MCerts accedited
laboratory and remediation equipment also has benefits, both in terms of cost and speed of turnaround.
For pragmatic advice and cost effective assessment strategies for the assessment
of filling station sites please contact James Skinner on 07770 611554.
We are accustomed to working for the big hitters of modern industry. However, today we were handed the opportunity of working around one of the big hitters from history. This WWII machine gun bunker holds listed status, and rightly so. It’s one of 18,000 built, around the coastal areas of the UK during Churchill’s defence against Operation Sea Lion.
