Milton Bryan to Heath & Reach

BBUSL contracted Chiltern Thrust bore Ltd to install a 506mm Ø SDR17.6 water main, at six locations located along its 15 kilometre route using Horizontal Directional Drilling (HDD) technology

With the wet winter we’ve all just experienced being a big factor for site access, each of the crossings had its own quirky issues. Also the nearest dedicated  fill up point for clean water supply, which is required throughout the HDD process, was over 11km away; a 22 km + round trip. We mobilized our crew, D80x100 drill rig with 300 GPM mud pump and our RE10000 mud cleaning unit with associated plant and equipment to undertake the crossings.  

Milton Reservoir woodland    
Milton Lodge A4012 London road
A5 Trunk Road
River Ivel
Mile Tree Road Quarry
Overend Green Lane

The first shot was installed at a depth of five metres under a wooded area at Milton reservoir. The set-up area was next to the entrance to the local Scout troop, which was a shade on the tight side as there was little or no access for anything much larger than a van; everything had to be unloaded on the road and tracked to the set-up position. Once in and set up, the piloting process was undertaken using a 150mm standard jet-head assembly.  Pre-reaming went smoothly using a combination of fly-cutters and barrel reamers, from start to finish the installation took three and a half days to complete.

We then mobilised to Milton Lodge crossing. The set-up area was located next to the Lodge House on the Duke of Bedford’s Estate. The crossing itself was under the A4012 Road at 5 metres deep and also a wooded area which was located on the exit side. Drilling in a similar ground formations as the first crossing; piloting, pre-reaming and the pipe installation  was undertaken in just three days. 


The third shot undertaken was the River Ivel. The installation had to be a minimum of 4 metres below the river bed.  Although the pilot took a little longer because of the change in ground formation, we were expecting this as we were now only about half a kilometre from a gravel extraction works. Having changed tooling and drilling fluids to suit, we drilled out with a rail head drill head; as anticipated it did take some time but after the pilot was completed the rest of the process went like clockwork with the crossing taking just over three days.

Shot four was sit-up was in the quarry and the containment of drilling fluids was a key issue in this area. The quarry management had expressed their concern regarding cross contamination, so all of the drilling spoils were re- moved from the drill areas immediately as  they were produced. They were then re-cycled using our RE10000 cleaning unit.  Again, we were geared up for some tough going being in a quarry but we were pleasantly surprised, the predicted formation didn't  throw up as much resistance as we were expecting. Even with the extra movement of drill fluids/spoils, we were out of the quarry in three and a half days.    

Shot five at Overend Green Lane needed to be minimum of 4 metres deep. Again expecting a harder formation, this also drilled and pre-reamed with a certain amount of ease again taking 3 days from start to finish   

Shot six was under the A5 Trunk Road. To date our client is still waiting for the go-ahead from the Highways Agency to complete this installation.    

All the crossings were just over 100 metres in length, the exception being Milton Reservoir at just over 120 metres.


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