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AMS No-Dig Case Studies

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Cross Section of the Drill profile
Cross Section of the Drill profile

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Project Name: Lock Ryan WwTW

Project Summary: Scottish Water is currently constructing an 800mm discharge pipeline from the Lock Ryan WwTW in Port Rodie, Stranraer discharging through a diffuser into the Irish Sea.

AMS No Dig Ltd, commissioned by contractor Leslie MWH Joint Venture recently completed the installation of the Sea outfall section by HDD techniques.

Project Details: The sea outfall section involved passing under an existing railway line and sea revetment terminating 3m below the sea bed in a pre-constructed cofferdam.

The design, planning and approval process took two years to complete before construction commenced in February 2015. AMS were involved throughout the process and prepared detailed construction proposals including commissioning of calculations necessary to gain construction approval from Network Rail and the port authority, the organisation responsible for the Revetment.
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Drill site overview
Drill site overview

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Project Name: High Pressure Gas Pipeline Replacement – River Eden, Carlisle

Background: High flows on the River Eden during heavy rains and flooding in Carlisle in 2005 caused substantial river bank erosion in the vicinity of the high pressure Gas feeder 11 pipeline crossing. This erosion exposed the crown of the feeder main. Any future riverbank erosion could have undermined the pipeline, leading to the possibility of localised supply security issues if the pipeline were to fail. For safety reasons and to ensure continued fitness for purpose and compliance with National Grids’ Safety Case and the Pipeline Safety Regulations 1996, National Grid decided to divert the pipeline and re- install the crossing at greater depth.

A design study was undertaken in 2014 to determine the best engineering solution. Horizontal Directional Drilling was considered the most viable trenchless installation technique from both an environmental and cost consideration.

Following a competitive tender process PPS Pipeline Systems secured the main contract and in February 2015 commissioned AMS No Dig Ltd to carry out the trenchless installation on their behalf.

Design: The available site information indicated the ground conditions consisted of sand and river terrace gravel to 6m below ground level on both sides of the river overlying Sandstone rock formation. The 432m crossing was designed with a 1700m entry and exit radius with a 7 degree entry and exit angle to provide 5m cover within the Sandstone rock under the river bed with a maximum overburden of approximately 12m. The pipe for the diversion of the 85 bar MOP pipeline was standard 914mm NB steel but with a heavier wall (19.1mm) in accordance with the institute of gas engineers IGE standards.

AMS’s Prime 250 tonne drill rig was selected to complete the installation together with high performance mud management equipment positioned both rig and pipe side of the crossing.
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AMS No-Dig’s Pit Launch directional drilling rig in place ready to start drilling
AMS No-Dig’s Pit Launch directional drilling rig in place ready to start drilling

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Project Name: Pit Launch

Project Summary: AMS No Dig Ltd, commissioned by a main contractor, has recently completed the installation of multiple cable ducts into an existing substation by below ground HDD techniques.

Project Details: The scheme was originally designed to be completed by conventional HDD techniques using a standard surface launch drilling rig. Drilling from the surface each duct was to pass under numerous buried services and into the existing substation.

However, due to site constraints it was not possible to position the drilling rig in its intended drill position which meant a surface launched HDD was not feasible in order to meet the required drill profile.

AMS engineers looked at other trenchless solutions such as auger boring and micro tunnelling before settling on a pit launched HDD which offered the simplest and most commercially beneficial solution.

AMS No-Dig’s new Pit launch HDD rig which fitted the bill perfectly. The Pit Launch Drilling Rig is a heavily engineered machine capable of producing 12 tonnes pull force with 3000 ft/lbs of rotary torque and is fully steerable.

Utilising pressure compensating load-sensing hydraulics, the rig will only demand the required amount of power from the 126 BHP Cummins 4BTA diesel engine.

Rotary torque is produced by a proven Poclain MS11 Hydraulic piston motor. To keep the overall length to the minimum, the breakout wrench is designed to travel up the mast during the final ream and product installation. This allows a reamer of up to 355mm diameter to come up onto the bed of the rig with the product pipe behind it. A hydraulically controlled push plate is fitted to the rear of the mast to clamp the rig into position between the pit face and the rear wall.

The Pit Launch is an all hydraulic rig. There are no electrical controls in the pit even the engine emergency stop is on a flying lead that can be removed at night.

Designed to operate 1 metre long drill rods the rig will set up in a pit approximately 3 metres long x 1.6 metres wide. The Power Unit will remain on the surface connected via a 10 metre long hydraulic umbilical.

In total seven cable ducts were installed from a single 8m wide by 4m deep shaft. Each pilot was drilled with a 1m separation from the shaft on a profile up to surface within the substation.
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The above drawing shows the planned drill paths under the railway
The above drawing shows the planned drill paths under the railway

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Project Name: Crossing of the Railway for the Turnford 33 Kv FFC Replacement Scheme

Project Location:: Cozens Lane East, Broxbourne, Hertfordshire

Project Summary:: AMS No-Dig was contracted on behalf of UKPN to carry out two directional drills beneath the main Network Rail lines between London and Stansted Airport.
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The location of the launch pit with the rig in the background.   The narrow confines of the site can be seen.
The location of the launch pit with the rig in the background. The narrow confines of the site can be seen.

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Project Name: River Medina Sewer Replacement Project, Isle of Wight

Project Summary: The project involved the replacement of an existing 400mm sewer with a new 500mm pipe over a distance of 550m from Cowes to East Cowes, Isle of Wight.

Project Details: As part of Southern Water's £10.5 million investment in works to replace 30km of sewers across the south east of the UK, AMS No-Dig were contracted by main contractors Clancy Docwra to install the new 500mm sewer pipe over 500m from Medina Road in Cowes to The Esplanade in East Cowes, Isle of Wight.

The entire length of the drill was beneath the bed of the River Medina at depths of up to 25m below the river bed.

Due to the nature of the drill, traditional 'walk over' tracking methods could not be used to track the drill head's progress, so AMS used a hi-tech Gyro steering tool.

The DrillGuide GST system is an optical gyro tool that does not require any surface wire grids to guide the drill bit. The accuracy of the Gyro Steering Tool is 0.04° azimuth and 0.02° inclination, allowing the new pipe to be installed with pin point accuracy even over the 550m length of this drill shot.

Due to the limited space available at the drilling compound in Medina Road, AMS opted to use the Powerbore 70t Drilling Rig.

The rig is very compact at 10m x 2.2m and when considering it offers 70 tonnes of thrust and pullback it proved to be the ideal choice for this application.

The drilling fluid adhered cuttings which were removed from the hole were processed using one of AMS No Dig’s bespoke mud management systems.

The innovative modular design consists of an 18,000 litre mixing tank, a mud cleaning system and two 26,000 litre storage tanks. This arrangement provided optimum flexibility in terms of both site planning, as dictated by circumstances on the ground, and operational requirements.

The high performance recycling unit has been custom designed to process 3000 litres of high viscosity drilling fluid per minute.

Screening is carried out using the revolutionary pyramid screening system which ensures consistent cleaning down to 20 microns.

This project was featured in the latest edition of UK Water Projects Online - to see this Case Study, click here.
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The Prime Drilling PD250
The Prime Drilling PD250

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Project Name: River Tyne River Crossing

The project: The requirement of the project was to install two shots across the River Tyne, from Wallsend to Hebburn, each consisting of a bundle of 180mm ducts to be used for new electric cables to replace existing old oil filled cables. The total length of each shot was 400m. Several problems were encountered during the course of the project, all of which were overcome by AMS No-Dig to achieve a successful installation of the ducts. The project was carried out using AMS No-Dig's largest drilling rig - the Prime Drilling PD250 which has 250 tons of pull back force.

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The Powerbore 70 tonne rig
The Powerbore 70 tonne rig

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Project Name: Selby Rail and River Crossing

Project Summary: Length 300m
Depth -18.5m
Ground conditions, Clay, Sand and Sandstone
Date completed 27/7/12
Product pipe- 4 way 180mm PE SDR-11
Drilling assembly 6 5/8” GST (Gyro Steering tool) 6 ¾” 7-8 Lobe 3 stage downhole mud motor and 9.7/8” MT Drill bit

Project Details: Drilling Contractor AMS No Dig from Scunthorpe, North Lincolnshire, UK was commissioned by Network Rail through Global Rail Construction to design and build a project to replace electricity cables as part of the Selby Swing Bridge Interlocking Renewal scheme. The works consisted of a HDD installation under a grade 2 listed building, Ouse Road ,the River Ouse, and the main railway line in the town centre of Selby, North Yorkshire, UK.

The project faced some difficult challenges from the start. Due to land access and easement issues the requirement was to design a complicated three radius horizontal plan, this involved a 32° left turn followed by a 12° turn to the right with a combination radius of 225m. What is meant by combination radius? This is the combination radius of the drill string changing direction vertically and horizontally at the same time, this project had a 475m vertical radius and 250m Horizontal radius to ensure that once installed, the cables would be located within agreed land boundaries.

In addition to the drill passing under listed buildings, a road and river parallel to a metallic railway swing bridge, it also passed beneath a sheet piled flood defence and under the railway lines, all areas of very high magnetic interference.

AMS No Dig Ltd worked closely with SlimDril International to provide the most cost effective and technically sound engineering solution to steer the pilot and given the lack of area to lay out surface coils and beacons, and given the large amount of magnetic interference present, the Brownline DrillGuide GST system was deemed the best steering tool for the job, as traditional wireline steering tools would not be suitable for such an application.

The DrillGuide GST is an optical gyro tool that does not require any surface wire grids and is not affected by any external magnetic interference. The tool does not require to be housed inside a non-magnetic drill collar and therefore can be positioned nearer to the drill bit, giving accurate hole data as soon as possible. The accuracy of the GST tool is 0.04° on azimuth and 0.02° on inclination.

Network Rail maintained a close monitoring regime throughout, and as there was very little tolerance for the steering engineer to work to, this called for careful project planning and attention to detail to ensure the pilot hit the many critical tangent points along the route, including providing enough space for future planned piling works.

The project commenced on 13th July 2012 using a standard jetting assembly but unforeseen ground conditions encountered after just 20m meant that one of SlimDrils 6 ¾” 7-8 Lobe 3 stage mud motors had to be quickly dispatched from their Great Yarmouth base over the weekend to minimise downtime. The motor was fitted with a 9.7/8” sealed bearing milled tooth bit (IADC 1-1-7) which was run in hole to drill the harder formation. Once the hard section had been negotiated, the motor was tripped out and exchanged for the softer formation jetting assembly to enable steering through the remaining soft formation to the exit point.

Reaming was carried out over a five day period using a combination of fly cutters, barrel reamers and fluted rock reamers. Initially a 508mm fly cutter and barrel reamer combination was used to ream from chainage 300m to chainage 80m which consisted of stiff clays down to 7m below ground level (bgl) followed by sand and silt down to hole bottom at 21m bgl. The reamer was then tripped out of the hole and exchanged for a rock reamer which was used to ream the harder rock section situated between chainage 80m and chainage 20m.

Due to the limited space available at the drilling compound and with the requirement to run 5” drill pipe to satisfy the criteria set by the steering tool insurer, AMS opted to use the Powerbore 70t. The rig is very compact at 10m x 2.2m and when considering it offers 70 tonnes of thrust and pullback it proved to be the ideal choice for this application. In total 100cu of fluid adhered cuttings was removed from the hole. This was processed using one of AMS’s bespoke mud management systems. The innovative modular design consists of an 18,000 litre mixing tank, a mud cleaning system and two 26,000 litre storage tanks. This arrangement provided optimum flexibility in terms of both site planning, as dictated by circumstances on the ground, and operational requirements, as dictated by conditions encountered under the ground.

The high performance Derrick recycling unit has been designed to process 3000 litres of high viscosity drilling fluid per minute and comprises two Derrick Equipment FLC-504 shale shakers for primary screening and a Derrick FLC-504 mud cleaner, complete with 3 x 10’’ de-sander cones and 20 x 4” de-silter cones, for de-sanding and de-silting. The Derrick 504 units are mounted on a 24ft base tank which incorporates integrated centrifugal pumps to feed the de-sander and de-silter cones. Screening is carried out using the revolutionary pyramid screening system which ensures consistent cleaning down to 20um.

The two 20 foot holding tanks include strategically placed agitators to ensure quality and flow of clean mud is maintained to the drilling rig, even when the 1500l mud pump is working to capacity.

The entire plant can be mobilised and made operational within hours of arrival on site, helping to eliminate the long lead times usually associated with installing a liquid mud plant.
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The AMS No-Dig Powerbore 70 tonne drill rig set up on site. The mud recycling system can also be seen behind the drilling rig
The AMS No-Dig Powerbore 70 tonne drill rig set up on site. The mud recycling system can also be seen behind the drilling rig

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Project Name: River Tees Railway Crossing

Project Summary: AMS No-Dig has recently completed a high profile project for Balfour Beatty Utility Services, on behalf of CE Electric, which involved the installation of multiple cable ducts under the River Tees at Middlesbrough. The purpose of the scheme was the replacement of the existing overhead power lines with new cables running under the river bed and the main railway lines which run along the side of the river.

Project Details: Under normal conditions a Magnetic Guidance System (MGS) would be used to steer the pilot bore. The problem with using standard MGS steering tools is that if the steering engineer does not have the facility to lay out an energised wire grid on the surface above the drill path the accuracy of the tooling can be affected by magnetic interference either naturally occurring or from metallic structures in the vicinity.

This scheme was particularly challenging as it called for the installation of two drill shots at 5m centres with a tolerance +/- 1m at the drill exit points. It was not possible to lay out a wire grid due to the presence of railway lines and the River Tees. To further complicate matters Newport Road Bridge, a major steel structure, is situated just 20m to the side of the proposed drill line.

Taking this into account it was clear an alternative solution would be required to drill the pilot bores.

Enter the Drillguide Gyro Steering Tool (GST). The GST does not require a surface grid or non-magnetic drill collars as it is not affected by magnetic interference. The GST is accurate, on azimuth, to within 0.04 degrees. This means that at 500m it will steer to within +/-0.35m of the target line, well inside the tolerance specified.

The system was ready to operate within a couple of hours of arrival on site. Input of entry and exit co-ordinates to WGS84 and of the tangent points along the route were all the set-up that was required.

The steering tools performance exceeded all expectations and the scheme was completed without incident and within the required tolerances to the delight of all concerned.
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Guided Auger Boring Rig
Guided Auger Boring Rig

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Project Name: Auger Boring - Rail Crossing, North Lincolnshire

: AMS No-Dig has recently completed a difficult scheme installing a 300mm gravity sewer as part of a culvert replacement project under railway lines close to our offices in North Lincolnshire.

The main challenge faced by the AMS engineers was the achievement of the tight tolerance in the gradient necessary to ensure that the system would flow properly after completion.

Although not ideal, the topography of the site and ground water levels meant that the pipe would be just 600mm below the tracks once installed. To further complicate matters, the work was to be carried out whilst the lines were in use and not during a ‘no trains’ period as would be normal for such work.

A special dispensation was granted by Network Rail to allow the installation to go ahead at the reduced cover, but only when a strict installation and monitoring regime was agreed and in place.

The work was completed over a two week period during January 2012. Twenty four hour track monitoring was in place throughout and work was paused every twenty minutes or so when a train went by.

A 2 inch pilot string was installed to line and gradient before the critical auger and jacking process could commence.

Because of the limited ground cover, in order to minimise the risk of lifting or moving the lines, the auger process was slowed to 300mm per hour. Requiring great patience, the 15 meter crossing was completed with minimal ground movement.

Now in commission, this is the shallowest trenchless installation completed by AMS to date.

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Sizewell nuclear power station
Sizewell nuclear power station

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Project Name: 132kv Cable Circuits, Sizewell B power station

The contract: Commissioned by SEESA and Magnox South, the works involved the installation of 4 x 132kv cable circuits from the main Sizewell power station to a new power station currently under construction. The purpose of the work was to connect the existing power station to the new power station which will take electricity from the Greater Gabbard off shore wind farm which is due to go into service in 2012.

The project: The project was to fabricate and install 5 way 180mm hppe duct configurations under areas of engineering difficulty along the cable route. In all, a total of 12 drills were carried at three locations each ranging from 60m to 380m in length. The scheme presented a number of high risk implications: crossing under wetlands, forested areas, streams and the Sizewell B access Rd.
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6.75 inch mud motor fitted with 9.87 inch tricone bit
6.75 inch mud motor fitted with 9.87 inch tricone bit

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Project Name: Franklaw to Barnacre 630mm Water Improvement Scheme

The contract: Commissioned by United Utilities, the aim of the scheme was to lay a new potable water main from Franklaw water treatment works (WTW) to Hoghton reservoir as part of large diameter pipe cleaning enabling works. In total 6km of pipe had to be installed between the WTW and the reservoir by a combination of open cut and horizontal directional drilling (HDD), with HDD used to negotiate two areas of engineering difficulty.

The project: Balfour Beatty Utility Solutions Ltd commissioned AMS No-Dig in 2008 following a competitive tender process. The project involved horizontal directional drilling under the River Wyre, The Avenue and a farm access road installing a 630mm HPPE water main. The length of the crossing from entry to exit point was originally 270m. In addition a further 150m of 630mm HHPE was drilled under a factory forecourt.
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