World Tunnelling & Trenchless World, July / August 2015 by Webmaster Aspermont Media

Alpine

The century-old Rossh채usern tunnel gets with the times

TBMs

The Saudi seven and a summer of hot tunnelling

Dewatering

The importance of planning to avert disaster

ISSN 1756-4107 CovI_WT1507.indd 1

July / August 2015

www.world-tunnelling.com 16/07/2015 10:12

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CONTENTS

Losing the shackles of superstition

rban India. Swarms of traffic. A thousand vehicle horns. Ribcage cattle. Skyscraper sundries on bicycles. Rickety rickshaws... Seems an ideal set-up for one of those ‘why did the person cross the road?’ jokes.

Our interest with the following story is: why did the woman cross under the road? Delhi is known unceremoniously as the rape capital of India, where public transport is unsafe for females. Lately, one woman – Reiko Abe – has helped bring about a big change in those circumstances. She could not, however, have done it in her native country. In Europe, St Barbara is recognised as the patron saint of mines and tunnels. In other countries, female names are given to tunnel boring machines for luck. In Abe’s home country of Japan, things are a little different. An ancient Shinto superstition said that if a woman entered a tunnel under construction, she would anger the jealous mountain goddess and cause injury to the workers. Japan’s Labour Standards Act banned women from underground construction sites and mines until 2006. Even today, in Japan, less than 5% of managers in the workforce are female.

“An ancient Shinto superstition said that if a woman entered a tunnel under construction, she would anger the jealous mountain goddess and cause injury to the workers”

News

Features Alpine projects TBMs Dewatering Contacts

4 12 19 21

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Two decades since Abe became a civil engineer in Japan and started to pursue the career she wanted, she is often the only woman on site surrounded by tens of thousands of male workers. After overseeing construction safety on Indian metro projects for seven years, she was promoted to head Oriental Consultants India, a unit of Tokyo-based ACKG. The company is extending subway systems in Delhi and Mumbai. Abe is also overseeing a mass-transit project in Jakarta, having previously worked on an undersea tunnel in Norway, Taiwan’s high-speed rail, the metro in Kiev (Ukraine) and an urban-planning project in Qatar. Delhi’s women tell Abe how riding in a modern system in segregated carriages has been liberating. “It was taken for granted by men, but wasn’t the norm for women,” Abe says. “As a result of what I helped construct, women in Delhi are able to have a mode of public transport that’s safe for the first time,” she says. “I’m actually very embarrassed by the attention... [but] I want to be at the top, not just among women, but among all Japanese engineers.” Hats off to you, Abe... and then swiftly back on again if we’re underground – safety first. Finally, I return to the question: why did the woman cross under the road? Why not? LUKE BUXTON, EDITOR luke.buxton@aspermontmedia.com

Next month North America Shaft sinking & raise boring Waterproofing

COVER

Swiss railway operator BLS celebrated breakthrough on a new, twin-track Rosshäusern Tunnel on June 2 on the Berne-Neuchâtel line. See page 7

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NEWS

Final Midtown segment sunk Engineers on the new Midtown Tunnel, which crosses the main channel of the Elizabeth River in Virginia (US), sunk the final segment on July 14. There are 11 segments on the immersed tunnel, each weighing 16,000t. The segments were built in a dry dock in Sparrows Point, Maryland, and floated 220 miles down the Chesapeake Bay to Portsmouth, where they were stored at the Portsmouth Marine Terminal. After dredging the river and preparing the foundation with sand, construction crews began submerging the structures into the river with a lay barge, which assists in anchoring the large pieces into the river. Once each segment is submerged, 30in (762mm)-diameter pipes are used to backfill the segments with about 675,000t of aggregate and soil before 68,000t of large-diameter armour stone is placed on top to protect the tunnel from passing ships. The project is part of a massive US$2.1 billion public/private venture between SKW Constructors, the Virginia Department of Transportation (VDOT) and the Elizabeth River Crossings to improve the state’s ageing and congested bridges and tunnels that connect Portsmouth and Norfolk. The tunnel is due to be complete in December 2016.

Lafarge and Holcim cement merger Cement-product suppliers Holcim and Lafarge have launched their combined building-materials company, which they say is now the largest in the world. LafargeHolcim first announced merger talks in April last year, but faced antitrust concerns, disagreement over the exchange ratio and leadership of the combined company, as well as demands from the French financial regulator to sell some of the plants in their portfolio. LafargeHolcim has combined sales of SF33 billion (US$34.5 billion) and operations in 90 countries, making it larger than the

Holcim plant

Photo: Ingolfson

world’s three remaining top cement players: Cemex, HeidelbergCement and Italcementi. LafargeHolcim is focusing on fast-growing economies in Africa and Asia that are calling for more cement. The company is looking to produce new products but has also embarked on a scheme to reduce expendi-

ture by $1.54 billion each year within three years, chief executive Eric Olsen said. A new taskforce has been employed to investigate improving efficiency in LafargeHolcim’s cement plants. Holcim delivered cement to the Gotthard Base Tunnel in Switzerland. The company provided an integrated ready-mix concrete (RMX) solution on the Bodio and Faido sections of the tunnel. Holcim designed the high-tech RMX and supplied the total volume of 1.3 million m3 for these two sections. 100% of the required aggregates for concrete came from the recycling of the excavated material. Holcim is also responsible for providing the cement required for the Sedrun section.

New MD for Golder Associates Dr Elisabeth Culbard will take over as managing director of global consulting firm Golder Associates’ UK and Ireland business on August 10. In her previous employment Culbard was head of sustainability-engineering and construction company Bechtel’s global infrastructure business and was also a vice-president. Culbard led sustainability for Bechtel’s global infrastructure business for 12 years and has over 30 years of experience as an environmental scientist, with specialisms ranging from urban regeneration to civil-infrastructure financing and assessment. She is a technical expert in the fields of sustainability, environmental and social impact assessments, project planning and project management.

Dr Elisabeth Culbard

Culbard has worked on large infrastructure projects in the US; Crossrail, HS1 and Gatwick Airport in the UK; and water, road, rail and airport projects in Central and South America. She has also worked with waste and environmental management in Hong Kong, Kuala Lumpur and Singapore. Furthermore, Culbard worked for the International Finance Corporation (IFC) at a time

when the IFC’s environmental and social performance standards were beginning to gain ground, Golder said. Culbard has played a vital role in demonstrating the commercial value of sustainability throughout engineering projects. Most recently, she co-authored a report for the US Council for International Business on infrastructure’s role in delivering the UN’s post-2015 millennium goals on sustainable development. Golder in the UK and Ireland works with some of the world’s largest domestic and international companies in the mining, oil and gas, infrastructure, energy and manufacturing sectors. In recent years, the company has been involved in the HS2 in the UK.

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NEWS

Wallasea Island rises with Crossrail spoil The first phase of a project using excavated material from Crossrail to transform farmland into coastal marshland in the UK is now complete. In mid-July the new sea walls of ‘Cell 1’ were breached to allow tidal flow into the marshland on the Wallasea Island Wild Coast project. Over 3 million tonnes of excavated material from Europe’s biggest infrastructure project has been used to raise part of the island

Crossrail spoil

by an average of 1.5m, creating lagoons and other wildlife-friendly features and protecting these areas with new sea-walls. Intertidal saltmarsh is a crucial wildlife habitat for a variety of plants, invertebrates and birds, and acts as an effective sea defence for local communities, the Royal Society for the Protection of Birds said. Some 98% of Crossrail’s excavated material has been re-used, almost half of it shipped to Wallasea Island. At its peak, six ships arrived at Wallasea each day, unloading 8,000t of material. The 2,400 shiploads removed 150,000 lorries from the roads.

Thames Tideway Tunnel plan

‘Super sewer’ investors named UK utility Thames Water’s 25km London sewer tunnel is a step closer to reality after a consortium won the right to invest in the £4.2 billion (US$6.56 billion) project. The Thames Tideway Tunnel will be financed by Allianz, Amber Infrastructure, Dalmore Capital, International Public Partnerships and Swiss Life Asset Managers. The project will hold tens of millions of tonnes of combined raw sewage and rainwater that currently

overflows at least 50 times a year into the River Thames. An independent company, formed by Thames Water, will own the tunnel, licensed by water regulator Ofwat. Thames Water’s 5 million customers face an extra £80 on their annual bills to pay for the project. Construction on the 7.2m-diameter tunnel, at depths of 30m to 70m, is expected to run from 2016 to 2023. Construction will take place on 24 sites.

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ALPINE PROJECTS

The new north-south connection The forthcoming N4 Axenstrasse in central Switzerland will improve safety and traffic flow on an important European route Above: route of the Neue Axenstrasse: tunnel sections (dotted red line), open sections (orange line)

“Tunnel construction is inevitable because of the physical barriers of Lake Lucerne in the west and the Fronalpstock mountain in the east”

he existing Axenstrasse main road between Ingenbohl and Gumpisch is part of the busy north-south connection leading to the Gotthard Pass. In a European context, the existing National Road N4, also called Axenstrasse, is a main transit route (together with the N2/E35 motorway circumscribing the other side of Lake Lucerne) connecting countries such as Germany, France and the Netherlands to southern destinations of the Swiss canton of Ticino and Italy. Unlike the N2/E35, and despite its importance, the existing Axenstrasse is only a standard two-directional main road with one lane in each direction. Although it has been renovated during the past few decades, it does not meet the current demand. Therefore, a new ‘N4 Neue Axenstrasse IngenbohlGumpisch’ project is being evaluated as a joint scheme of the National Federal Roads Office (FEDRO) and the cantons of Schwyz and Uri. The Neue Axenstrasse is needed because: • At present safety and accessibility cannot always be guaranteed. Rock falls and landslides (debris flows) have repeatedly led to road closures. In 1992 the Axenstrasse was com-

•

pletely blocked due to rock falls for an eight-month period. Road closures cause serious consequences, particularly for residents and commuters, as well as for the economy of the cantons of Schwyz, Uri and Ticino. A new road via tunnels will increase the safety and accessibility; The Neue Axenstrasse must be available as an alternative route to the N2/E35 motorway with the Seelisberg tunnel; The traffic on the Axenstrasse passes right through the village of Sisikon (400 residents). On peak days there are up to 14,000 vehicles, causing an enormous burden for the inhabitants. The cross-town link also hinders the traffic flow. Consequently, the Axen project will bypass the village and relieve it of traffic; and Non-motorised traffic (bicycles, agricultural traffic, pedestrians) could benefit from the project because it will continue to use the old Axenstrasse (which will be structurally adapted) and will thus be separated from the principal traffic flow. Tunnel construction is inevitable because of the physical barriers of Lake Lucerne in the west and the Fronalpstock mountain in the east.

The overall costs for the project are estimated at SF980.270 million (US$1.035 billion). This breaks down to SF70 million for the cost of the open track between the tunnels and SF910 million to pay for the tunnels. The operational and maintenance annual costs for the new highway are calculated at SF16.3 million.

TUNNEL CONSTRUCTION The construction of the project is planned to start in January 2018. The Axen engineering consortium comprises: • Lombardi (consortium leader): responsible for geotechnical and rock mechanics as well as design of the tunnels; • Locher Ingenieure: responsible for design of the tunnels; • ARP Ingenieure und Berater: responsible for design of the engineering structures; • B+S: responsible for road design; • BG: responsible for landscape architecture; and • F. Preisig: consultant. The Neue Axenstrasse project consists mainly of two tunnels – the 2,842m (9,324ft)-long Morschacher Tunnel and Sisikoner Tunnel (4,442m) – and a short open section between them. Both tunnels will comprise a single tube, which will be

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ALPINE PROJECTS

Cross-section of tunnel showing safety and trafficcontrol equipment

â&#x20AC;&#x153;Blasted material will be delivered by conveyor to the new open section of the route and loaded on ships on Lake Lucerne. The material will be dumped at the south end of the lakeâ&#x20AC;?

operated bi-directionally. An intermediate ceiling with outgoing air flaps will provide smoke extraction in case of fire and emergency. Emergency chambers and exits are located beside and beneath the road surface. Morschacher Tunnel features four different profiles along its length. The longest section shows a normal profile with intermediate ceiling (2,491m). There is also a section without intermediate ceiling, whose length is 187m. The remaining profiles have free spaces opposite each other on both roadsides, or have a single free space on one side only. Sisikoner Tunnel includes six different profiles. As with Mohrschacher Tunnel, there is a normal-profile track with (3,216m) and without (86m) an intermediate ceiling, as well as a profile with free spaces on both opposite roadsides or with a unique free space on one side. In addition, there is a normal profile with intermediate ceiling and invert arch, as well as a profile with opposite free spaces and invert arches. The minimum clearance profile of both tunnels is 7.75m x 4.5m. The size of the free spaces is 3m x 4.5m and the dimensions of the border are 0.7m x 2m. The air-exhaust duct above the ceiling has an area of minimum 11m2 and a height of 1.8m. At the moment three major topics are under investigation. Rare biotopes on the construction site need to be specified in order to protect plants and

animals. Preliminary measures parallel to the Neue Axenstrasse, that are associated with the crossing point of the Swiss Federal Railways, are being carried out. Preliminary measures for the environmental protection are also being carried out. According to schedule, construction will be complete in 2025. However, there are delays at the moment regarding the tunnel design and planning that may delay the start and completion dates of tunnel construction.

TRICKY GEOLOGY The geological basis of the two tunnels is generally calcareous rock. Apart from the fault zones, the mountains can be considered favourable in terms of stability, despite the modest coverage. Morschacher Tunnel lies entirely in the stratum of the Swiss Drusbergdecke with siliceous limestone, limestone and calcareous marl. Karst cavity with temporarily high water levels can be identified in the massive Schrattenkalk limestone. The same challenges are also noticed in the northern part of Sisikoner Tunnel, where it also crosses the Swiss Drusbergdecke. The southern part of Sisikoner tunnel passes through a sequence of carpal frieze marls, which have an increased protection burden compared with other sections. Both Morschacher and Sisikoner Tunnels will be built with drill-and-blast technology due to the complicated, rigid and fluctuating geology.

The unique feature of the new tunnels is the method of disposing of the blasted material. The steep morphology at the northern portal of Sisikoner Tunnel leads to unacceptable potential settlement of the temporary construction site nearby. The existing open track is very narrow and it would be impossible to deposit the blasted material on it, or transport it with trucks over this area. Therefore, blasted material will be delivered by conveyor to the new open section of the route and loaded on ships on Lake Lucerne. The material will subsequently be dumped at the south end of the lake in order to flatten the bottom surface in this region. Drill and blast is always a demanding implementation method, and compared with the TBM process it places demands in terms of cost, time and knowledge.

PROTECTING THE ENVIRONMENT The construction of Neue Axenstrasse is economically and ecologically sustainable. The project has been subject to a multi-stage environmental impact assessment, which was achieved in 2007. Various legal provisions determine the relevant procedure. During 2008 an intense office consultation procedure took place. The Swiss Federal Office for the Environment and the Federal Commission for the Protection of Nature and Cultural Heritage, among others, submitted a list of detailed opinions about the project and of improvement recommendations. The project has been subsequently adapted in several points, such as environmental changes related to the portal ventilation panels, changes to the exit of Gumpisch tunnel and abandonment of a separate security tunnel (in the current plan the escape route is through a piping duct). A separate environmental documentation is currently in preparation (EIA 3d level).

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ALPINE PROJECTS

Getting with the times Swiss railway operator BLS is replacing the century-old Rosshäusern tunnel with a new twintrack upgrade

Photo: Peter Studer

LS’ railway network in Switzerland extends to 420km. About 20% of the system is in tunnels (83km). The network runs above and through the varied landscape of the country with its many rivers and mountains. There are 402 bridges and 71 tunnels longer than 2m under BLS’ management. Identifying which sections are in need of repair or replacement helps ensure that the system does not come under strain from growing usage. The numerous single-track sections on the Berne-Neuchâtel line have inadequate capacity for future needs and the Rosshäusern-Mauss section has been identified as a bottleneck for high-speed train operations. The Swiss government defined the Berne-Neuchâtel line as part of the country’s high-speed network and, along with the cantons in charge of regional transport affairs, set aside funds for line development. A new, twin-track Rosshäusern Tunnel will save the expensive trouble of restoring the old tunnel and straighten out the slow curved sections. The project aims to bring the section in line with the highspeed transit initiative, boost regional transport services, increase capacity, reduce journey times and help stabilise the Berne-Neuchâtel line timetable.

OUT WITH THE OLD The old tunnel was built at the end of the 19th century and has been in operation since 1901. The Bern-Neuchâtel railway line opened on July 1, 1901. The Bern-Neuchâtel railway tunnel has a length of 1,100m (3,608ft) and the current speed is 90km/h (56mph). The tunnel remains in operation but no longer as a tunnel for the railway line. The railway engineering facility will be dismantled.

After reparation works (including minimal repairs to the tunnel vault), the tunnel will have its purpose in drainage and environmental aspects, such as expanding the Flüelebach stream. The owner of the new tunnel is BLS Netz. The new railway line, including tunnel construction, is planned by the IG Ross-Hü planning consortium, which is also responsible for site management. Various construction companies have also been

Tunnelling workers celebrate the construction breakthrough on June 2, 2015

Below left: comparison of old single-track tunnel and new double-track passage

•

What the project involves

• •

Construction of the new, twin-track Rosshäusern Tunnel with an optimised, shorter profile (twin-track Rosshäusern-Mauss line); Adaptations to and construction of rail, control and catenary equipment; Removal of the existing railway route and restoration of alignment; and Preservation/maintenance of existing tunnels

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ALPINE PROJECTS

Completion of tunnel construction will be in mid-2017. Completion of railway engineering is set for mid-2018 with the beginning of railway operation to follow shortly after. Dismantling of installations, restoration, earthworks and works in the old tunnel construction will take place during 2019. The end of the project is 2020 and all works are going to schedule. Total project costs are SF265 million, including construction of 2.1km of tunnels and 1.6km of railway line.

Photo: Peter Studer

A train on the RosshäusernMauss section of line

contracted. Tunnel-specific construction is being undertaken by a consortium of five companies. The new tunnel has two surface mining areas with a length of 170m and a mining area of 1,910m, with a total length of nearly 2.1km. The cross-section is sized to the profile EBV 4 S3.

NEW PLANS There are discussions going on about developing the Lötschberg-Basis-Tunnel between Frutigen and Raron. The tunnel is 34km long, but only one-third of the tunnel has dual track, with the remaining two-thirds being single-track. Aside from conveying commuters and tourists from Valais to Berne, from German-speaking Switzerland to the Valais mountains or business travellers making the journey to northern Italy, the tunnel also caters for freight. Freight containers pass through the Lötschberg section of the Rotterdam-Genoa international corridor at all hours of the day and night. Around 50 passenger trains and up to 60 freight trains use the line every day. Utilisation of the tunnel’s capacity averages between 80% and 100%.

“Around 50 passenger trains and up to 60 freight trains use the line every day. Utilisation of the tunnel’s capacity averages between 80% and 100%”

One of the portals of the old tunnel

The route has plenty of water, unstable sandstone and marl (Untere Süsswassermolasse). There is not too much earth covering (a maximum of 50m). New safety standards, for example self-rescue and an emergency-exit construction in the middle of the tunnel, make this build unique. There is compact material management with short distances. While works are ongoing, transportation services must continue, such as school buses, near the construction area. Tunnelling began in May 2013. Contractors are using drill and blast in the upper section together with a track-mounted rock cutter. The tunnel excavations were carried out in Kalottenvortrieb mit Rohrschirm (crown drive with pipe umbrella). The mining work in the above section was completed after two years on June 2, 2015. For the project owner this was a milestone and the big day will follow with the completion of the whole construction and the beginning of railway operation. End of tunnel excavation is eyed for November 2016.

Photo: Peter Studer

WORKS UNDER WAY

Relief road Next summer marks the completion of a tunnel to bypass traffic in the east of Switzerland

he Küblis Bypass is the third road structure of the Dalvazza-Selfranga project. The Klosters Bypass opened ten years ago, followed by the Saas Bypass in 2011. The Küblis Bypass tunnel, in the Swiss canton of Graubünden, is part of the A28 national road between Landquart and Klosters and serves to relieve the town of Küblis. The work around the 2.2kmlong tunnel includes the construction of a safety gallery and the management of the adjacent Schanielatobel landfill site. The tunnel will reduce the associated noise and emissions for 800 inhabitants of Küblis. Approximately 70% of the bypass will be in tunnels – 2,255m out of the route’s 3,350m.

CONSTRUCTION SCHEDULE Austria-based Strabag, Central and Eastern Europe’s largest July / August 2015

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ALPINE PROJECTS

Companies involved in the project Subcontractor: Gebr. Vetsch of Küblis, cut-and-cover tunnelling and track construction; Subcontractor: tunnel-sealing consortium consisting of Strabag and SikaBau; Wastewater plant supplier: ZUT/Strabag, Environmental Technology Stuttgart; Concrete supplier: Gebr. Vetsch, Küblis;

construction group, is the lead contractor on the project. The groundbreaking ceremony for the preparatory works for the Küblis Bypass took place on May 14, 2008. Installation of the tunnelling works began on June 10, 2010. The blasting lasted from the end of September 2010 through to March 2013. The main tunnel has a length of 2,255m with a horseshoe-shaped profile of 95m². The trackway is 7.5m wide with a verge of 1.4m on both sides. The tunnel has a total of four safety bays with a length of 50m each. The gradient in the tunnel is 4.5%. The service tunnel is 2,100m long with a horseshoe-shaped standard profile of 13m². It is connected to the main tunnel by 30m-long cross-passages situated every 280m. The concrete lining and finishing works were concluded in June 2015. Work on the trackway began in April 2015 and is

scheduled to be completed during July. Rock support uses anchors and shotcrete with fibre reinforcement. The construction works are on schedule. From today’s standpoint, nothing stands in the way of opening the tunnel in the summer of 2016 as planned, it is reported. The total cost for the Küblis Bypass amounts to SF210 million (US$222 million). Strabag’s share of the project is about SF85 million.

CONSIDERATIONS IN THE ROCK The main rock type encountered is Prättigau flysch (sandstone/ limestone) with at times high proportions of phyllite (finegrained mica, clay and silt fraction, up to 20%). Due to the shallow depth of parts of the tunnel beneath the surface (in some places 5m deep, in others 140m), special attention had to be given to vibrations from blasting below residential buildings. A wastewater treatment plant was set up for compliance with environmental standards. The crossing under the Rhaetian Railway near the Dalvazza Portal is in the groundwater zone. Construction made it necessary to lower the groundwater level over a period of several years and waterproof the site up to about

50m in the excavated tunnel. The undercrossing of the Schaniela Gorge was prepared using cut-and-cover construction (secant-pile wall with concrete slab for the main tunnel, cut-and-cover tunnel for the service tunnel) ahead of the excavation works.

•

Tunnel advance and support: Atlas Boomer E2 C two-boom face-drilling rig in main tunnel; Atlas Boomer 282 two-boom face-drilling rig in service tunnel; Mucking: Liebherr L 566 T

•

wheel loader with four Cat 730 articulated dump trucks; Secondary profiling: Liebherr R 944 CT crawler excavator; Shotcrete: a Meyco Potenza shotcrete robot and two truck mixers.

Views of construction in progress on the Küblis Bypass tunnel

Strabag tunnel projects in Switzerland

Equipment used for Küblis Bypass tunnel •

Dalvazza pre-cut: Prader of Chur; Dalvazza civil-engineering structures: Gebr. Vetsch of Küblis; Prada pre-cut: Franco Somaini, Bonaduz; Prada civil-engineering structures: Toneatti of Bilten; Advance measures for crossing Schaniela Gorge: Toneatti of Bilten

•

Gotthard Base Tunnel, Erstfeld and Amsteg sections (completed) Grimsel Power Plant, office and pressure tunnel (completed) Farettes Power Plant, inflow tunnel (under construction) Rhone Oberwald Power Plant (starting construction)

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ALPINE PROJECTS

Above: a drilling jumbo at work; location map; a tunnel approach

At home under the mountain Works on the Choindez road tunnel in Switzerland are nearing completion

T Below: a portal Below right: drilling advances from face of completed tunnel Bottom: breaking down debris

unnelling is a serious business in the Alps. The difficult mountain terrain is perhaps most evident on the A16 motorway that links the Swiss canton of Jura and the Bernese Jura to the existing network of national roads. It also provides a connection between the Swiss and French motorway networks. There are more than 25km of roads inside the mountains in more than 25 tunnels. These vary in length from Tunnel du Mont Terri (4,068m or 13,346ft) and Tunnel de la Perche (1,027m or 3,369ft, Bypass Porrentruy) to more than 16 structures that are each under 1,000m.

There are 8.5 tunnels in the territory of the Republic and Canton of Jura (the 0.5 corresponds to a horse tunnel on the border with the canton of Berne). 40% of the roads in the territory of the Republic and Canton of Jura are underground. Development of the A16 is expected to stimulate the regional economy and unload the crossroads of Basel.

TUNNEL CHOINDEZ Contractors are extending the A16 by 3,288m, including 2,786m underground in the SF200 million (US$212.4 million) Choindez Tunnel. The radius of the lower surface of the tunnel is 5.4m. The length of the northern cutting is 462m. There are 10 cross-links and two ventilation stations. The Republic and Canton of Jura, infrastructure service, contracted the GETuC group of

engineers: IJA by GVH DelĂŠmont, GGT, BG SA MFR Geology and Geotechnics. The GTC consortium comprises Tunnelbau Marti, Parietti & Gindrat, and NeuchĂ˘tel Marti Special Works. Tunnel construction began in May 2011. The first 400m north of the Alsatian Molasse has very bad geotechnical characteristics, which required the use of specific stabilisation measures. Other geology includes sandstone, marl and limestone. The first 400 metres in the north were excavated by roadheader, protected by a vaultumbrella. The rest of the tunnel has been excavated mainly in traditional drill-and-blast. All northern works are completed today, with 30% left to do in the south portal. The main structure of the tunnel will be completed in October 2015 and commissioning is planned for the end of 2016.

Tunnel Choindez timeline 2006-2009: First stage of construction. Landslide from the surface overburden disrupts progress by 20 months 2009-2011: Excavation of the north portal. 200,000m3 of material removed. Tunnel construction begins 2013: After drilling, excavation continues in both north and south January 2014: Sprayed concrete applied June 2015: Structural works complete Summer 2015 to autumn 2016: Final finishing End of 2016: Tunnel commissioning World Tunnelling would like to thank Thierry Beuchat, infrastructure services engineer, tunnels and bridges, republic and canton of Jura, for his contribution to this article July / August 2015 04,06-10_Alpine_WT1507.indd 10

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TBMs

Ground-breaking works, attended by Prince Khalid bin Bandar, governor of Riyadh province. Jaime Freyre Andrade, head of the FAST consortium, is on the right

The Saudi seven Several tunnel boring machines are in action in tough ground conditions under the Saudi Arabian capital, Riyadh

A “The first TBM for this line, Mneefah, is expected to progress at an average of 100m a week with a mid-2016 completion date”

rriyadh Development Authority awarded the design and construction contract of the US$22.5 billion Riyadh metro in Saudi Arabia to three consortia – BACS, ArRiyadh New Mobility (ANM) and FAST – in August 2013. The BACS consortium includes Bechtel, Almabani General Contractors, Consolidated Contractors Company and Siemens. The consortium is led by Bechtel and will design and construct the Blue and Green lines. The contract value is about $9.4 billion to $10 billion. The ANM contract is worth $5.2 billion and includes construction of the Red Line, Qasr Al Hokom station and Western Station. The ANM consortium includes Ansaldo STS, SaliniImpregilo, Larsen & Toubro, Nesma and Bombardier. Larsen & Toubro and Nesma will provide civil works services, Bombardier will look after the procurement of the vehicles and Ansaldo STS will provide technology support services for the Red Line. FAST, which is led by FCC Construccion, received a $7.9 billion contract to construct and

design the Orange, Yellow and Purple Lines. The consortium includes FCC Construccion, Samsung, Alstom, Strukton, Freyssinet Saudi Arabia, Typsa and Setec. The contract includes construction of 64.6km of rail track (29.8km on viaducts, 26.6km underground and 8.2km at ground level). It is two years since the contracts were awarded and tunnel boring machines are currently under the Saudi soil. In total, seven TBMs will excavate tunnels up to 35km long and 30m below the surface. The 178 km-long system will have 85 stations in total, including underground, ground-level and elevated stations. This July, tunnel boring began on the 38km Line 1 (Blue Line). The first TBM for this line, Mneefah, is expected to progress at an average of 100m a week with a mid-2016 completion date. Construction of the metro is expected to be completed by 2018. Jaime Freyre Andrade, head of the FAST consortium, answers WT’s questions on the work of FAST’s two TBMs to date.

How is construction progress? General construction started on October 30, 2013. The excavation of shafts for the TBMs to be assembled started on May 2, 2014. The First TBM, Dhafrah, began on April 30 and the second TBM, San’ah, started on June 30. By July 3, the progress of Dhafrah was 694m and TBM San’ah had excavated 6m. The construction of Line 5 is the only one that requires TBMs. Lines 4 and 6 are mainly viaducts. An average advancement between 312m and 350m per month is expected, although this forecast was revised upward in the second month, following the production of TBM Dhafrah with a reduced learning curve. With the planned average, the TBMs should finish their tunnel-boring works on December 2, 2016 (Dhafrah) and September 2, 2016 (San’ah).

What are the tunnelling conditions? TBM Dhafrah will excavate 6,704m, while TBM San’ah will bore 4,882m. The overbunden of the alignment is between 14m and 31m. Along Line 5 the tunnel crosses the rock materials of the Jurassic Jubaila and Arab Formations and of the Cretaceous Sulaiy Formation. All these ancient sedimentary formations

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are made up of limestone rocks and brecciated calcareous rocks, habitually in white to yellowish layers of 20cm to 40cm thick with some millimetric marly interbeds. The sedimentary rock layers have a predominant horizontal structure with some local folds and scarce sealed joints. The rock mass is very low weathered to moderately weathered, with areas of ancient cemented breccia and some karstified areas due to dissolution of the calcareous materials; these karsts are sometimes filled with soft soils such as sands and clays. It is expected that the rock mass will be found in dry or slightly wet conditions with low local levels of water. The main difficulties expected are associated with the potential karstified areas because of the presence of large voids or areas filled with soft soils and water. A specific geological investigation plan has been conducted with geophysical methods and boreholes to identify the sections with high probability. This will identify these kinds of geological elements, and will be complemented with mitigation approaches based on probe boreholes and grouting. The TBM operation will proceed based on intense control of the operational parameters, as well as monitoring data and with

a frequent face inspection when crossing the riskiest sections. The competent authorities have prepared a landfill area where excavated material will be disposed of, treated and stored.

What are the other challenges? There are many challenges in this project that must be overcome to reach such strong targets. In order of importance, the list could be: safety (always first); permits to be supplied 24 hours per day, seven days per week; customs and requested documentation; expat labour and co-ordination between different cultures; logistics inside a crowded area; and traffic around the logistics shafts.

What can you tell us about the TBMs? The manufacturer is Herrenknecht and the model is earth-pressure balance, mixed shield, 9.77m

diameter. They were numbered as S-895 (Dhafrah) and S-896 (San’ah). They are identical, each with a total length of 102m. They were ready in Germany in the first week of December 2014 and the last week of January 2015. They were delivered by 66 trucks (most of them special measures) arriving at ports in Europe. They had to cross overseas by vessel and later they crossed more than 1,000km inside Saudi Arabia by truck. Around 7,200 tunnel-segment rings will be used; the plan includes crossing some stations in void (if stations are finished before a TBM reaches them). The segments are produced by PACADAR, a Spanish company that formed a Saudi branch. The precast plant is located very near both shafts (less than 6km to reach to sites). Once the TBMs have finished, they will be dismantled and can be re-used on another project.

“[The TBMs] had to cross overseas by vessel and later they crossed more than 1,000km inside Saudi Arabia by truck”

San’ah is one of two identical Herrenknecht TBMs currently at work under Riyadh

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The delicate art of turning Alice Alice, the world’s 10th largest tunnel boring machine, has successfully completed a unique turn on the Waterview project and is now on the home straight The front end of TBM Alice

Centre column: turning the shield at the northern portal Right column: the same site after the turn, with the TBM now in the righthand tunnel Bottom centre: the pre-cast concrete factory has produced 24,000 segments Bottom right: a vehicle moves segments to the TBM for use

lice, the 14.4m-diameter Herrenknecht EPBM, has been around a bit. It was constructed at the Herrenknecht factory at Guangzhou in southern China. The 2,400t machine was dis-assembled and shipped to New Zealand in 90 containers. The containers were transported from the port through Auckland’s central business district and suburban streets to the construction site during a mainly night-time operation that took a week to complete. It then took three months to reassemble the TBM. Tunnelling began on November 4, 2013, with the leviathan progressing an average of 14m a day on the 2.4km twin highway tunnels. Alice peaked at 36m per day through soft rock, typical 5mpa, but which can reach up to 30mpa. The rock is highly water-bearing in certain zones with highly changeable insitu moisture contents. At the northern end for approximately 200m there is a mixed face of alluvial soils in the crown and soft rock in the invert. The alignment passes beneath numerous dwellings and recreational grounds as well as one of Auckland main arterial routes to State Highway 16 (the Northwestern Motorway).

Alice in numbers amount Alice was turned to start the north-bound drive 180º the space between the TBM and the walls during the turn 150mm the 2,400t the weight of TBM Alice length of the twin-road tunnels 2.4km total tunnel project completion to date 75%

COMMUNITY SPIRIT The Well Connected Alliance comprises NZ Transportation Agency (NZTA) and tunnel contractors McConnell Dowell, Obayashi and Fletcher. One of the biggest challenges for the project, the alliance says, is being a ‘good neighbour’. The 5km of new motorway – half of it underground – runs through several suburbs in west Auckland. The project has been committed from the start to keeping communities well informed of the work and its impact on their lives.

Those impacts include noise, traffic diversions and necessary overnight works. Community concerns at the start of construction have now given way to praise from local leaders for the project’s consistent and proactive engagement. Besides the motorway, the project is delivering a 9km-long cycleway and new parks/playgrounds/sports facilities. The twin tunnels are one part of the project, the other is the construction of the motorwayto-motorway Great North Road Interchange. The four ramps on

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the interchange will connect Auckland’s Southwestern and Northwestern Motorways – the so called ‘missing link’ to complete the Western Ring Route – a 48km-long second motorway through New Zealand’s largest city, which will take pressure off the existing State Highway 1 through the city centre and provide more resilience to Auckland’s motorway network. A total of 1.7km of bridges is being constructed on the interchange. A lot of construction is over or adjacent to a “live” Northwestern motorway. There are seven different companies in the Well-Connected Alliance and there is a strong emphasis on building an alliance culture. The key project objective is that no-one is hurt on the job. The safety of all workers is embedded into the alliance’s culture. Through communications and meetings, workers are encouraged to take care of themselves and their mates to ensure that everyone gets home safely. One recent example of this was hosting a worksite visit from Patrick Tuipulotu, a player in New Zealand’s world-champion All Blacks rugby team, to lead workers through warm-up exercises at the start of their shifts. The well-being of workers is another key driver on site. The project’s 800 workers represent almost 40 countries, and many do not use English as their main language at home.

The Well-Connected Alliance has organised courses to improve communication and confidence. One task for people on those courses was to re-write the project’s 10 Golden Rules of Safety to make them easier to understand. Several of those who graduated from the courses later featured in an award-winning safety video.

MANAGING THE TURN TBM breakthrough took place on September 29, 2014. The shield and G1 turnaround and restart tunnelling started on December 19, last year. The initial northbound drive with shortened TBM was complete by February 20. G2, G3 culvert gantry turnaround was finalised by April 27. The shield and gantries were turned by sliding the parts around on a steel-plate floor on a purpose-built cradle. A hydraulic jacking system was used to pull

the cradles. Another hydraulic jacking system was used to jack vertically to align the cradle onto the drive alignment. There were no problems with the manoeuvre other than the space constraints of the Northern Approach Trench (NAT) structure. The gantries were propelled in and out of the tunnel with a hydraulic jack and cam system to grip a rail in the tunnel invert. One of the biggest challenges was the 180º turn-around on the NAT floor with little more than 150mm to spare between the TBM and the NAT support piers. Alice is now digging the northbound tunnel: the drive is at ring 550, almost 50% complete – 75% complete in total. The first two of 16 cross-passages are complete and a third is 75% complete. The north-bound tunnel drive is due to finish on time in October. The TBM will later probably be returned to its manufacturer.

Top centre: the Southern Vent Building at the south portal. The TBM is due to break through in the trench to the left of the building in mid-October Top right: the Great North Road interchange will link the Southwestern and Northwestern motorways. The northern approach to the tunnels is at the left of the image Bottom centre: breakthrough of the first of 16 cross-passages that will connect the tunnels. The passages are 11m long and located every 150m Bottom right: interior of the first driven tunnel after compaction of aggregate. The tunnel is 2.4km long and will carry three lanes of traffic when it is opened in early 2017

World Tunnelling would like to thank Chris Ashton, Waterview Connection’s tunnel construction manager, and construction director Iain Simmons for their input

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TBMs

The hidden dangers of tunnelling On tunnelling projects, you can only prepare for so much and then something unexpected comes out of the pocket The NeelumJhelum hydropower project in Pakistan, where at least four workers died in a suspected gas explosion

afety is always the numberone priority when it comes to heavy construction work; its importance is felt even more when that work takes place hundreds of feet underground. In early June at least four engineers were reported dead, and 10 others sustained critical injuries, when the tunnel boring machine in use on the NeelumJhelum hydro-power project in Pakistan hit a gas pocket and exploded, the project’s executing agency, WAPDA, has confirmed.

Dr Donald Lamont, animateur of the International Tunnelling Association’s working group WG 5 (‘health and safety in works’) and director of Hyperbaric & Tunnel Safety, shares his expertise on the subject of tunnelling explosions. The reports on the explosion at Neelum–Jhelum are very sketchy and give no indication of where, how or why the explosion occurred. It is only possible to speculate on the possible causes of an explosion in the tunnel. These include hitting a pocket of methane gas followed by the ignition or detonation of the gas. Outbursts can also occur due to very high stress levels in the rock, resulting in the explosive ejection of debris from the tunnel intrados. There could be the slow build-up of an explosive mixture of methane in the tunnel followed again by an ignition or detonation. The gas pocket could contain carbon dioxide or a carbon dioxide/monoxide mix and lead to an irrespirable or toxic atmosphere. A leak of mineral hydraulic fluid could lead to a cloud of atomised oil mist, which again could be the fuel for an explosion. Further causes of an explosion could be a massive electrical fault or over-pressurisation of the hydraulic system on the TBM itself. Gas pockets occur most commonly

The US$1 billion 969MW scheme, located in the Mujohi area of Azad Jammu and Kashmir,

in mining rather than tunnelling, where excavation is taking place in coal-bearing (and hence potentially gas-bearing) strata. Gas outbursts in mining can be of methane or of carbon monoxide/ dioxide mixtures. Coal hardness and high overburden pressures are considered to increase the risk of outbursts. From the limited geological information that is available on the internet, it appears that this tunnel was being driven in sedimentary rock. However, there was no indication of the presence of coal, so the presence of a methane pockets is not particularly likely. Additionally, the TBM, which appears to have been unshielded, would have provided some mechanical protection against the explosive ejection of debris, certainly from the excavated face.

What happens during an explosion?

Following the explosive ignition of a flammable gas such as methane in the tunnel or mine, the oxygen in the atmosphere is consumed by the explosion and an anoxic atmosphere remains, possibly contaminated with toxic carbon monoxide. Death from asphyxiation follows if those in the mine or tunnel suffer blast injuries or

involved a Chinese contractor and thus many Chinese workers. The Chinese embassy has asked the Pakistani government to investigate. Speculation has arisen that international consultants had advised against using mechanised tunnelling on the project. This is the second fatal accident at the site. At the end of 2014 a wall or pillar collapsed, killing at least 10 workers. The project, with an original completion date at the end of 2016, is facing delays and alleged financial shortfalls.

cannot immediately don self-rescuers and escape to a place of safety.

What can be done to prevent them?

Prevention through good ground investigation to detect gas pockets and monitor rock stress is one measure. However, predicting outbursts is a very imprecise science. Atmospheric monitoring coupled with ventilation, the use of HFDU low-flammability fluids and good electrical engineering all reduce the risk of an explosion.

Where has this happened before?

A UK example was a methane explosion in January 1986 at Newton Mearns near Glasgow, which resulted in three fatalities. This was due to methane build-up during the Christmas shutdown along with inadequate monitoring and ventilation in the tunnel. Then in 1995 following an ignition of methane in the tunnel crown, during construction of the Allers sewer between Blantyre and East Kilbride, high methane levels were detected resulting in a suspension of work till appropriate ventilation had been installed. The contractor was later fined for breaches of health-and-safety legislation.

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TBMs around the world In this roundup of global tunnel operations, World Tunnelling magazine discovers that work is heating up this summer for tunnel boring machines NEW TRACKS FOR NETWORK RAIL UK rail-infrastructure authority Network Rail is poised to welcome the arrival of a tunnel boring machine that is to build the new Farnworth tunnel in Bolton. The project forms a major part of Network Rail’s £1 billion (US$1.57 billion) electrification plan for the rail network in the north of England. The machine will arrive from manufacturers in Oldham and will be assembled on site before it bores out the 300m tunnel, enlarging it to make it big enough to house two tracks and the new overhead electrified cables. Network Rail has already demolished platforms at Farnworth station to construct ones

that fit the new track alignment. Contractors have reinforced the existing northbound tunnel, which will no longer be in use, to prevent it from collapsing when boring work starts. Work is on track, Network Rail said, and engineers are confident that the project will be finalised by the original completion date of October 4.

INTERCEPTOR PREPARATIONS

The KaneoheKailua Wastewater Conveyance Tunnel is the first tunnel of its kind in the Hawaiian Islands, on a deeper and larger scale than all previous tunnels there

The TBM on the US$300 million Ohio Interceptor Tunnel in the US is due to start operations soon. The TBM will build a tunnel 6,200ft (1,890m) long, 27ft in diameter and 70ft to 160ft below the surface. It will be capable of holding up to 25 million gallons of

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The TBM has completed the west drive on Bangkok metro MRTA Blue Line Extension Contract 1 and will now start boring east

storm water and raw sewage that combine after heavy rains. That runoff will later be piped to the city’s sewage plant for treatment. The machine is expected to advance 40ft each day, with the dig taking nine to 10 months. The nine sewers that currently overflow will be connected into the new tunnel. The tunnel is expected to be ready for use on December 31, 2018.

BRUISED BERTHA BACK TO BUSINESS? Finally some good news for the Washington State Department of Transportation’s (WSDOT) Alaskan Way Viaduct replacement tunnel: TBM Big Bertha’s rebuilt drive gears will be delivered to the drilling site by early August. All 24 gearboxes and motors have been examined by The Gear Works, a large gearbox-building and repair company in South Seattle, and confirmed as being in good shape with no damage to the motors themselves. The company worked on the gear boxes and the 24 2ft-diameter pinion gears that rotate the drilling head. The 57ft-diameter (17.4m) machine broke down in December 2013, after completing only 1,000ft of the planned 1.7-mile tunnel under downtown Seattle. On July 7, WSDOT received a new schedule from contractor Seattle Tunnel Partners.

“A tunnel on this scale has not been built in the Hawaiian Islands before. Everything from the logistics of the tunnel operation to pre-grouting sections ahead of the TBM for groundwater control are new to the Aloha state” IMMINENT START IN INDONESIA A TBM is soon expected to start boring the tunnels for underground stations on the Jakarta Mass Rapid Transit (Jakarta MRT) project. Excavation was not expected until the end of 2015, but the machines arrived in the

country ahead of schedule. “The first TBM will be able to be used in August for the Bundaran Senayan underground station,” PT MRT first director Dono Boestami commented. The first phase of the MRT construction includes six underground stations planned along the MRT’s Lebak Bulus-Kota line: Bundaran Senayan, Istora, Benhil, Setiabudi, Dukuh Atas and Bundaran HI. The other seven stations will be elevated. Phase 1 of Jakarta MRT is due to open to the public by early 2018.

EAST-BOUND IN BANGKOK Also in August, a Terratec TBM will start the east-bound drive on the Bangkok metro MRTA Blue Line Extension in Thailand. In mid-May the 6.44m earthpressure balance machine broke through at Sanam Chai station. With this, the machine completed the excavation of the west-bound tunnel of the MRTA Blue Line Extension Contract 1. The contractor, Italian-Thai Development PLC, used the machine to bore this 2,800m-long alignment in one go, crossing two unexcavated stations and one ventilation shaft on its way. The excavation was performed through a complex geology and in the presence of high underground water pressure. The soil consisted of stiff clay and Bangkok’s aquifer sand, with large gravel chunks and sand stone at the deepest part of the alignment. The TBM drove under many historic buildings in the old city, so very accurate settlement control was of essence. The Terratec TBM was equipped with a two-liquid type backfilling system and a special clay shock injection system through the shield. The combination of both was proven to be very effective and restricted the settlement to less than 1cm in those critical areas. The EPBM had to bore through eight diaphragm walls, as well as several obstacles such as building foundations. This was expected at the beginning of the project and,

for this purpose, Terratec selected a unique cutterhead design with conical shape to overcome those smoothly without disrupting the soil around. The TBM achieved the planned average rates of 18m per day during the boring cycles.

DEEP DOWN IN HAWAII As of June 2015, a Robbins TBM had excavated more than 300m (1,000 ft) on the 4.6km (2.8-mile) drive for a new sewer tunnel in Kaneohe, Honolulu, Hawaii, US. The machine was boring at a rate of 12 to 15m (40 to 50ft) per day in basalt rock. The 3.96m-diameter main-beam TBM began its journey in spring. Nicknamed Pohakulani, meaning ‘Rock Girl’ in Hawaiian, it was launched from a 23m-deep starter tunnel. Contractor Southland/ Mole JV is building the KaneoheKailua Wastewater Conveyance Tunnel for the City and Council of Honolulu, which will improve wastewater infrastructure by eliminating overflows during rain. The deep-tunnel option was not the first design considered: preliminary plans called for a smaller tunnel under Kaneohe Bay. As the bay is an environmentally sensitive area, a deep tunnel remained an attractive option. During the design phase, it was decided that the tunnel route should travel inland and deeper underground to bypass one of the few residential areas along the alignment. Designers introduced an isolated curve in the tunnel plan of 150m radius, requiring the TBM to be designed with a unique back-up system. It is also specified that when crews navigate the tunnel curve, the machine must be operated using half strokes rather than a full TBM stroke. The curve is not the only unusual aspect of the tunnel; in fact, a tunnel on this scale has not been built in the Hawaiian Islands before. Everything from the logistics of the tunnel operation to pre-grouting sections ahead of the TBM for groundwater control are new to the Aloha state.

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DEWATERING

Dewatering differences The importance of planning to avert disaster

roundwater is not popular with tunnellers and shaft sinkers; other things being equal, most designers and contractors would prefer a ‘dry’ job to a ‘wet’ one. Groundwater encountered during tunnelling can either be a nuisance, reducing operational efficiency and making life underground less pleasant, or it can create major problems, which can threaten the viability of a project if not handled well. However, with careful planning and execution almost any groundwater conditions can be managed to allow successful tunnelling.

GROUNDWATER AND TUNNELS Most tunnellers and designers recognise that the presence of groundwater, even in copious quantities from permeable strata, need not be a major impediment to construction. Even so, many practitioners view groundwater control as a black art best left to the cognoscenti. This need not be the case. Successful tunnelling requires an understanding of ground behaviour, a realistic attitude to risk and uncertainty, and the application of flexible and responsive working methods. The same approach can be successfully applied to dewatering and groundwater control. It is useful to understand how tunnels interact with groundwater. A tunnel with an open face below groundwater level will act as a ‘drain’ and water will flow into the tunnel via the face, and via any unlined sections. If the rates of groundwater inflow are manageable and, importantly, do not cause instability at the face, then water can be simply managed by pumping to keep the face workably dry. This unsophisticated approach is proven and successful in

hard-rock tunnels. Bigger challenges come if the rate of water inflow is very large, or if the tunnel is in soil or soft rock that can be destabilised by groundwater seepage. Facing these challenges, tunnellers developed technologies to effectively pressurise the tunnel to balance the external groundwater head at the face, thereby keeping the water out. The earliest technique to achieve this, developed in the 19th century, was compressed-air working where the tunnel is pressurised with air to balance the groundwater pressure. However, there are health risks associated with operatives working in compressed air, and the use of the technique is now less common, apart from in special circumstances (such as interventions to replace cutter heads) under close medical controls. An alternative technique, the full-face tunnel boring machine (TBM) was developed in the latter half of the 20th century. These complex machines use either the earth pressure balance (EPB) or slurry method to balance external ground and

groundwater pressures and can allow a shirt-sleeve working environment in tunnels, even deep below groundwater level. However, there are cases when the use of a full-face TBM may not be appropriate or feasible, and groundwater-control techniques may be needed to deal with potential groundwater problems in the tunnel.

Sump pumping during shaft sinking in clay strata

DIVERSE PROBLEMS There is an important distinction between two different types of problem caused by groundwater. First is flooding or inundation of the tunnel by groundwater inflow. Second is face instability due to groundwater seepage. In relatively stable ground conditions (such as fissured rock) the main challenge is to find the space to deploy pumps of sufficient capacity to handle the water, without excessively hindering excavation and lining. If inflows are too large to handle, grouting can be used to reduce the permeability of the material ahead of the face; this can reduce (but not eliminate) inflows. However, some inflow can be good, and in hard-rock tunnels

“Many practitioners view groundwater control as a black art best left to the cognoscenti. This need not be the case”

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Sump pumping within an underpinned shaft

Underpinned Shaft with advance dewatering by external wells

Groundwater flow Fine sand

Groundwater flow

Running sand conditions Sump pumping in base of shaft in fine sand creates upward seepage and creates risk of running sand conditions

Above: running sand conditions controlled by pumped-well dewatering Above right: pumped wellpoints installed internally within tunnel for crosspassage construction

Fine sand

Dewatering to reduce pore water pressures External pumped wells around shaft in fine sand reduces pore water pressures in sand at base of shaft and avoids running sand conditions

the urge to seal every inflow should be resisted, as the inflows may usefully depressurise the ground ahead of the face, and inflows to the tunnel may reduce with time. In soils and soft rocks, face stability is the principal concern. Here even small quantities of water seeping into a tunnel face or the base of a shaft can cause significant instability and loss of ground, especially in finegrained sands and silts. Such unstable soils are often described as ‘running sand’, an evocative phrase that is an accurate description of how such material behaves. When a face is cut or an excavation is made in running sand, the exposed soil will flow or ‘run’ into an excavation, filling it up with fluid sand. This is obviously a problem and is hated by tunnellers. But what is not widely realised is that running sand is not a type of material. It is actually a state in

which a granular material can exist, when pore water pressures are high, causing low effective stresses, as result of which the soil looses all its strength and becomes fluid. When this is understood, it can be seen that dewatering can reduce pore-water pressures and transform running sand into more stable ground. This approach has been widely used on the Crossrail project, where depressurisation wells drilled out from the tunnels were used to reduce pore-water pressures in layers of fine sand and silt within the Lambeth Group to prevent instability and running sand conditions.

APPROACHES TO DEWATERING The geotechnical process commonly known as dewatering is more correctly described as groundwater control. There are two principal groups of groundwater-control technologies, as shown in the table. The first

GROUNDWATER CONTROL METHODS Pumping methods

• • • • • • •

Sump pumping Vertical wellpoints Horizontal wellpoints Deep wells with submersible pumps Ejector wells Passive relief wells Electro-osmosis

•

Exclusion methods

•

Steel sheet-piling Vibrated beam walls Cement-bentonite or soil-bentonite slurry walls Concrete diaphragm walls Bored pile walls Grout curtains (permeation grouting; rock grouting; jet grouting; mix-in place methods) Artificial ground freezing

group is pumping methods, where groundwater is pumped from an array of wells or sumps to temporarily lower groundwater levels. The second group is exclusion methods that use low-permeability cut-off walls or zones of ground treatment (such as grout curtains) to exclude groundwater from the excavation or tunnel. Pumping and exclusion methods may be used in combination. The nature of the ground conditions, particularly the permeability of soils or rocks, is obviously an important factor in the selection of the most appropriate dewatering methods. Furthermore, for tunnelling projects, available access space and geometry are key factors. For shafts the construction compound often allows sufficient space and surface access to install vertical dewatering wells or vertical cut-off walls or grout curtains around the shaft. However, on many projects surface access for drilling for dewatering wells or grout curtains from above the tunnel alignment is either limited or impossible, and in most cases this precludes conventional

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dewatering measures drilled from surface for tunnel construction. Where EPB or slurry TBMs are used, this does not cause a problem, because these technologies do not usually need external dewatering. However, dewatering requirements can be much more onerous where cross-passages, tunnel enlargements or other headings are to be dug by hand or mechanical excavation. If the

main tunnels are constructed by TBM, often these cross-passages and other excavations may be the only works that need dedicated groundwater control, to deal with conditions when the tunnel lining is broken out. These can be difficult dewatering tasks, with short or irregularly shaped tunnel drives, often in areas with little ground-investigation information. In these circumstances, groundwater exclusion methods can be attractive; grouting and artificial ground freezing around cross-passages and headings have been used successfully in the past. Groundwater drainage wells (typically pumped by a wellpoint system to give a greater lowering of groundwater pressures) can be drilled radially out from the tunnels to depressurise the surrounding soil or rock. This approach was used on several Crossrail contracts for tunnel enlargements and connections. In conclusion, tunnellers are unlikely ever to look forward to a job where they know they will have to deal with groundwater, but there is certainly no need to fear it. With good ground investigation information to give some foresight to the likely problems, there is a good ‘toolkit’ of pumping and groundwater-exclusion techniques to deal with a wide range of ground conditions and tunnel geometries.

This article was written by Dr Martin Preene, dewatering specialist and groundwater engineer, Preene Groundwater Consulting Editorial Editor Luke Buxton T +44 (0)20 7216 6078 E luke.buxton@aspermontmedia.com F +44 (0)20 7216 6050

Head of production Tim Peters Senior sub editor Jim Adlam Sub editor Woody Phillips

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Pipe rehabilitation

CIPP works during the cold snap

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Western Europe

Expanding the market share

Auger boring

Take-off by the Boeing plant

July / August 2015

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CONTENTS

Data: the Tasmanian devil?

onnectivity is the spice of life. That’s something to shout about. The human yell is about 88dB, a little more than half that of a jet taking off 25m away, the same volume as a motorbike 25ft distant, a printing press, slightly less a lawnmower. You can’t communicate with someone by shouting across a large expanse of water, but you can speak to them on the phone, or e-mail, even power their house. Thanks, in part, to trenchless technologies. In this edition of Trenchless World, we explore the condition of the trenchless sectors in six major countries in Western Europe where societies are very actively networking, giving a voice to their sector and securing its future, by hosting an array of events, connecting solutions “You can’t communicate with potential customers. On page 2, we report on the first contract to connect the electric grids of the UK and Norway under the North Sea. The move should bring down prices for customers, as well as enhance the security of energy supplies between the two nations. In Australia, similar plans are afoot. The Bass Strait, between mainland Australia and its southern island of Tasmania, at its narrowest point is about 240km wide and is being eyed by some as an important doorway to regional economic growth.

with someone by shouting across a large expanse of water, but you can speak to them on the phone, or e-mail, even power their house. Thanks, in part, to trenchless technologies”

News

Features Western Europe Pipe rehabilitation Auger boring

3 13 16

Contacts

The Australian government recently awarded a contract to Hydro Tasmania, the state’s predominant electricity generator, to explore another submarine cable connecting Tasmania to the mainland. Until June 2016, Hydro Tasmania will investigate the case for another Bass Strait interconnector, complementing the first subsea cable completed in the mid-2000s. Directional drilling was used on the first Basslink Interconnector Project, commissioned a decade ago. Contractors completed two 700mm-diameter drill shots in an environmentally sensitive site located on Aboriginal Heritage land. In addition to that, the government had talks with telecommunications infrastructure company SubPartners, which is rolling out a submarine cable from Singapore to Perth to Sydney with planned branches into Hobart, Adelaide and Melbourne. Another fibre connection provider routed to Tasmania “will put Tasmania right in the middle of a major data transfer route across the Australian continent, as opposed to basically at the end of a fibre cul-de-sac,” state innovation minister Michael Ferguson said. Life Down Under? What about life on top? Sorry, this one I couldn’t resist. LUKE BUXTON, EDITOR luke.buxton@aspermontmedia.com

Next month Regional focus: North America Microtunnelling ICUEE preview International No-Dig preview

COVER

A US$1 million programme of sewer and waterpipe renewal took place in York, Maine (US) in spring 2015. Contractor Ted Berry Company used ultraviolet-cured cured-in-place pipe to rehabilitate 414 linear feet of pipe. This view shows installation of the UV light train into the manhole See page 14

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NEWS

Norman Howell has joined Hydrascan

New face at Hydrascan Norman Howell has been appointed as head of business development at Hydrascan, a subsidiary of Kilbride Industrial Services in the UK, which developed the Typhoon Jetting System. Howell’s role will initially be to assist in positioning the company as the preferred choice for Asset Management Programme (AMP6) mains-water cleaning contracts. Howell has published and presented many technical papers relating to the pipeline and utility industries. He also has a history of professional affiliation to national industry bodies such as the UKSTT and Pipelines Industries Guild. Howell has covered many roles as an engineer, most recently establishing a consultancy offering technical and commercial support to a portfolio of clients within the pipeline sector. He has also been integral to the development and sales of emerging technologies and engineering techniques. Within the AMP6 period, water companies need to maximise current assets and minimise total costs, delivering value for money for their customers. The Typhoon Jetting System is a strong contender within that market, Hydrascan said.

Contracts are awarded to deliver North Sea power link UK utility National Grid has awarded contracts to build the first electricity link between the UK and Norway. Switzerland-headquartered power technology company ABB, Italy-based cable supplier Prysmian and French cable supplier Nexans will deliver the convertor stations on the €1.5 billion (US$1.7 billion)

contract shared with Norwegian transmissionsystem operator Statnett. The interconnector will be the world’s longest at 740km (459 miles), running from Blyth, Northumberland, in the UK, to Kvilldal in Rogaland, Norway, National Grid said. The NSN link, which is expected to be in operation by 2021, will deliver a

Doosan releases range of cleaner compressors

Doosan Portable Power has launched a new range of large Stage IV-compliant portable compressors. The compressors are used to provide compressed air for a wide range of drilling and boring machines. They are based on the same platform and are the first to feature a Doosan airend. The new platform covers five large Doosan portable compressors, namely the 9/274, 9/304, 12/254, 17/244 and 21/224 models, offering free-air deliveries from 21.5 to 30.0m3/min at operating pressures from 8.6 to 21.0bar. The new Stage IV compressors build on the high standards established by the Stage IIIB models, combining compact size and easy serviceability to ensure a positive return on investment. The compressors offer reduced size and footprint to minimise transport costs and promise unparalleled service access to optimise

Doosan’s new 12/254 compressor

maintenance operations. They have a full-colour digital display, with manuals in electronic form available on the display. Additional features such as multiple air outlets, a 110% bunded base, central drains and forklift slots have also been incorporated as standard in the new compressors. The modular design offers the flexibility for a wide range of optional equipment to be added easily, the company said. The wide range of options available allows the new Stage IV compressors to be adapted to a specific application, such as the fitting of an aftercooler with water separator and additional filters (IQsystem) as well as the use of a paint scheme to match the customer’s livery.

capacity of 1.4 gigawatts. “The benefits to both the UK and Norway are also huge,” Alan Foster, National Grid’s director of European business development, commented. “When completed, the link will deliver low-carbon electricity for the UK and also add to the security of supply for Norwegian consumers.”

Trelleborg open day draws crowds Around 30 processing companies got experience of trenchless pipelining technologies at the inaugural open day held by Trelleborg’s pipe-seals operation in Duisburg, Germany. Attendees were taught how to handle the new DrainPlusLiner 2.0 correctly in realistic conditions, utilising equipment normally used on construction sites. Trelleborg’s DrainPlusLiner 2.0 pipe liner has a silicone coating that uses synthetic polymers for trenchless pipe rehabilitation. The combination of cutting-edge textile technology and a special coating formulation has created a high-tech solution that meets high standards of quality and versatility, the company said. Trelleborg has expanded its ‘Tried-and-Tested’ courses and seminars to include product events for processors. The first such event was held in Duisburg on June 11. The next event is already scheduled for October, Stephan Raab, commercial manager at Trelleborg’s pipe-seals operation, commented.

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Breaking the 10% barrier Although trenchless methods still remain a small part of construction and rehabilitation jobs in Western Europe, there is plenty to shout about

ogether they propagate over a century of ideas, experience and innovation. For a collective 115 years they have been championing trenchless technology. The Netherlands Society for Trenchless Technology has been around for 27 years, the French Society for Trenchless Technology a quarter of a century, the Austrian Association for Trenchless Technology 24 years, the UK Society for Trenchless Technology is 22 years old, and the Iberian Society for Trenchless Technology is 17. Water, sanitation, telecommunications, energy: these societies have each been involved with major projects in these sectors to keep civilised life moving through non-disruptive techniques, improving living standards. Through networking, education sessions, conferences and seminars, as well as live demonstrations, they represent members who aim to connect modern and novel solutions to the next underground construction project. “Trenchless pipe-rehabilitation technologies are most successfully applied in inner-city areas,” the Austrian Association for Trenchless Technology (AATT / ÖGL) tells TW. The association goes on to highlight the other positives of trenchless compared with conventional techniques: shorter construction periods, a lower burden for residents, less traffic disruption and far fewer truck transports for handling excavation and backfill material.

something of a sloW start Most of the aforementioned societies were formed at the end of the early-1990s recession, a time when funding for infrastructure projects stalled, unemployment rocketed and social unrest

Trenchless technology has seen many innovations in recent years. Sekisui’s spiralwound piperenovation method has been developed for large-diameter pipes

plagued many cities. For the projects that continued, trenchless technology was seen as a specialist, expensive means for the ‘simple’ job of creating holes and putting things in the ground, or digging them out. Surely some sort of large shovel would do? In the ensuing years, national economies in Western Europe picked up and construction got back on track, with many forwardlooking ministers laying out blueprints for efficient systems. Non-disruptive underground installation and rehabilitation gained traction, with many local and national governments coming round to the notion of less-disruptive construction methods. These trenchless societies matured by the time the financial crisis of 2007-08 overshadowed much of the globe. While the

tremors are still felt in certain European countries today, others are forecasting slow growth, alongside the rising awareness of trenchless solutions. “The rapid development of new trenchless technologies in the early years, combined with the generation of a skilled group of practitioners and the development of theoretical knowledge about the techniques as a joint effort of clients, contractors and knowledge institutes, gave the trenchless industry its initial boost,” Jelle de Boer, executive secretary of the Netherlands Society for Trenchless Technology (NSTT), tells TW. “Following these developments, the technical possibilities have gradually changed over time – the size and complexity of projects have become both larger and

“Trenchless pipe-rehabilitation technologies are most successfully applied in inner-city areas”

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A vacuum excavator unit

“Europe is quite an open market for trenchless technologies and many actors – contractors, consultants, suppliers – are active in several countries”

Industry figures get to network and find out about the latest equipment and techniques at conferences such as this IBSTT gathering

smaller. The variety in length and size of the trenchless projects has changed dramatically.” In the Netherlands in 2015 drilling is applicable to large projects (a 4km meeting-in-themiddle HDD project will start in mid-July connecting the mainland to Texel, one of the Wadden islands), as well as to many small projects (i.e. 5-10m long), for example, for telecom-ducts. Jean-Marie Joussin, international director, French Society for Trenchless Technology (FSTT), agrees: “Today there are almost no more technical failures and limits: HDD of very great length or diameter even in hard and abrasive rocks; long, curved microtunnelling pipes up to DN3000; relining of any size or shape can be done using GRP prefabricated or cured-in-place pipe (CIPP) up to DN1200.” Connectivity is the buzz word. There is no shortage of fibre-optic cable installation schemes being rolled out. On such projects microtrenching machines seem to be the compromise for conventional big-trenching contractors, while others pick HDD or auger boring. In the more traditional water sector in France the main challenge of the last two decades for the government was to deal with environmental issues, including minimal asset-management and the need for more efficient potable-water systems. “This has helped business development together with the availability of new equipment and technologies covering microtunnelling, HDD and rehabilitation. Contractors and consultants have invested much more in hiring high-level operators, in educating their staff on equipment and its use, including health and safety.” In Austria, Portugal and Spain, in the early to mid-1990s there were only a few members who offered trenchless services. “We were enthusiastic in bringing new ideas to the market, but our knowledge was limited by traditional barriers focused in trenching,” Angel Ortega,

methods that offer smaller site footprints, faster installation and greater ‘optioneering’ opportunity for the more challenging projects, UKSTT points out. “One sector in particular has seen huge change: technologies associated with locating, surveying and assessing the condition of underground infrastructure have seen a transformation in miniaturisation, camera and visual survey technology, and improvements in data capture, management, transmission and display.”

Collaboration for Change president of the Iberian Society for Trenchless Technology (IBSTT), tells TW. “Prices were very high for the Spanish and Portuguese market.” Twenty years ago, much of the innovation in UK trenchless technology was driven by the need to rehabilitate the Victorian (1837-1901) sewers of London and other large cities, such as Manchester, notes the UK Society for Trenchless Technology (UKSTT). In the early 1990s, techniques such as CIPP (invented in the UK) were already in use for sewer rehabilitation, and methods for relining pressure pipes to reduce leakage in water mains were beginning to be developed and used. Since then, CIPP has seen significant developments in resins, lining materials and curing

National trenchless societies are paramount in championing their respective nations’ abilities and place on the construction field. Many state members are also affiliated with other societies from other countries in this interactive international business. This relationship is extended to educational sessions and events hosted by other societies. NSTT initiates research co-ordinated by the society and member organisations, and participates in research by other organisations on behalf of its members. AATT organises the Austrian no-dig conference and publishes materials for its members. With the support of the ÖGL, trenchless technologies could enhance an even stronger market position and the members capitalise on the

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growing trend towards no-dig techniques, the association notes. “It is very interesting to look to the international standards of no-dig technologies. We are confident that we can keep up very well with innovation, compared with the international market.” FSTT works with many other associations and state organisations, including federations of contractors involved in sewer, water and other network construction; as well as gas associations and water agencies. It is also active in the committees preparing new national rules for pipeline construction (Fascicules 70 & 71), bringing trenchless technologies into the new regulations (initiated by the French government after a series of explosions of gas pipelines). These rules mandate advance notification of works with identification of operators and existing buried networks (DT-DICT regulations); with special requirements for construction close to existing networks. Each year FSTT holds two regional no-dig technical days with 250 to 500 attendees, including an exhibition of 20 exhibitors. The next one will be in Toulouse in November and will cover the south-west regions of the country. “Europe is quite an open market for trenchless technologies and many actors – contractors, consultants, suppliers – are active in several countries,” Joussin remarks. IBSTT’s first handbook for no-dig technologies was printed in 2014. IBSTT, in close co-operation with the Politecnich University of Madrid, is launching in the last quarter of 2015 the first no-dig Masters degree related to this technology, including 40 hours of theory and practice. There are many Spanish and Portuguese subsidiaries of multinational groups already established and the level of the technology used is the same used in the average advanced country.

IBSTT is in close contact with the other European societies. “We have just finished a very interesting project with our Italian colleagues related to critical underground infrastructures.” The UKSTT is another society that offers a busy portfolio of events for its members and anyone interested in the sector. The biennial ‘No Dig Live’ exhibition and conference allows

companies to exhibit their trenchless equipment, while companies run ‘live’ demonstrations. The society’s university outreach programme is now in its sixth year, offering UK universities an undergraduate introductory lecture spanning the wide range of trenchless technologies materials and systems. The UKSTT runs regular ‘road

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Western europe

The trenchless societies work to promote best practice in the industry. Ian Ramsay, UKSTT chairman, presented David Pitt of Infotec with an Innovation Award at the UK’s No Dig Live 2014 event

shows’ at venues throughout the UK and Ireland. These are one-day mini-exhibitions and a programme of presentations on relevant trenchless topics. In addition, UKSTT is embarking on its first of a series of ‘Master Classes’ this year, which will deal with specific topics in much greater depth. Members of the UKSTT Council continue to attend and support several International committees that are currently drafting and updating European (EN) and international (ISO) standards for the trenchless industry.

AppeAling to the young

“During the last four years, the industry in Western Europe faced a slowing down of activity, especially in southern Europe”

Many challenges stand in the way of the proliferation of trenchless sciences. One of these is, of course, geology. The geography of Western Europe is varied, and can bring a plethora of obstacles to each underground job. “The main technical challenges remain issues due to soft Dutch soil conditions (allowable mud pressure, high groundwater table, extremely soft Holocene layers and resulting drifting of pipelines, etc.); and environmental issues (disruption of the surroundings, the environment, needed space in projects),” de Boer explains. Human-made conditions can also construct hurdles. The main problem in Austrian cities is that the surface of the streets spirals downwards and so a part of the

benefit (such as lower costs for the reconstruction of the road surfaces) is gone, AATT remarks. As illustrated earlier in this article, the capabilities of trenchless are far-reaching. The fact is, however, that the market share remains small. “The returns to date from various published papers, reports and investigations by trade and construction industry / utility organisations suggest that trenchless system usage varies between sectors, with percentage usage ranging from 10% to 90% penetration,” UKSTT finds. NSTT’s own research shows that the share of trenchless technologies in the total investment in pipe and cable laying is about 10-15%; in Austria it is 85% open-trench construction, while trenchless technology accounts for 15%. “During the last four years, the industry in Western Europe faced a slowing down of activity, especially in southern Europe, together with the presence of more competitors and decreased price margins,” explains Joussin. In France the main problem was a drop in price levels, but action to promote trenchless has helped to convince more clients that it can offer significant advantages and the volume of activity was not significantly affected. “We still find a barrier in front of

25 years of FSTT The US marks the date as its Independence Day, while the French Society for Trenchless Technology (FSTT) celebrated the fourth of July this year by marking 25 years since its formation. In June, as part of its 11th VST (Ville Sans Tranchée) national No-Dig event held in Paris, FSTT acknowledged the milestone during the gala dinner packed with more than 350 people. The VST attracted 96 exhibitors and more than 1,200 attendees. Founding leader Michel Mermet, Ingénieur des Ponts et Chaussées, head of the Val de Marne technical department in charge of water and wastewater, and

past FSTT chairman, was awarded the prestigious ISTT Lifetime Service Award.

Sam Ariaratnam (with microphone) prepares to present the ISTT Lifetime Service Award to Michel Mermet (far left)

traditional technologies, but through seminars and practical presentations the day-to-day use of no-dig technologies is becoming more and more popular. On the other hand, advanced techniques are becoming valuable when you consider total cost and advantages versus traditional trenching,” Ortega says. Attracting new blood to a small pool is a tricky feat, with “a phasing out of the initial engineers that developed and expanded the technology, so that existing knowledge needs to be preserved and transferred to a new generation,” de Boer says. With one or two exceptions, persuading clients and consultants to specify trenchless methods is a major task, as is persuading them to require their contractors to use properly trained and certified staff, UKSTT notes. “[There is] an increased emphasis on the essential importance of independently accredited and recognised training for all operatives and supervisors and a much greater awareness of this need by most client organisations,” the society says. Yet although manufacturers of various types of equipment used by the trenchless industry can now provide excellent hands-on training for operatives of specific equipment, there is still a shortage

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of nationally accepted accredited and certified training for both operatives and managers. The UKSTT’s annual awards dinner is now in its 22nd year. The society also seeks to recognise and support young engineers, offering the winner a £2,000 (US$3,124) bursary. IBSTT says it still has to convince some water operators of the great choice for renovating water networks using no-dig techniques. “Young engineers change their minds quickly but decision-makers are reluctant to change the way projects are designed.”

Happy Horizons Iberia is leaving the crisis suffered since 2004 and the region’s expected GDP for 2015 is up 3.5% on 2014. Construction is recovering and IBSTT partners are taking advantage of this new scenario. The condition of the Dutch construction industry has worsened since the economic crisis of 2008. However, the trenchless industry seems to be sound. The number of new installations by microtunnelling have recovered from the dip seen around 2010, whereas installations by HDD did not show a marked decrease and have stabilised over recent years. The French construction industry recorded a slowdown from 2013, after recovering from the financial crisis. This is due to economic troubles in the eurozone. “We expect a better trend for the next years thanks to the better international situation and the launching of state-funded big projects mainly in the transportation and building fields,” Joussin adds. The French construction industry is active in exports, with two contracting groups among the top ten in the world: Vinci and Bouygues. With about 40 players, the trenchless sector is a small part of the country’s total construction or even pipe-construction business, but shows a constant volume growth. Major projects are still going ahead. In the Netherlands large

projects in recent times include the extension of the gas-distribution backbone and the relining of sewer networks in several municipalities. “It’s business as usual for the installation of telecom ducts for the new glass-fibre connections to households, and the renewal of ageing water, gas and electricity distribution pipes.” The main projects in Austria using trenchless techniques by order are of demand are: sewer, water, gas, oil, industrial sector, others, confirms AATT. In France, the water sector is the traditional field for trenchless. The sewerage market is still offering the biggest opportunities. “But new sectors are more and more exciting, such as the energy market (including a new pipeline of large diameter, up to 56ft, for GRT Gaz), high-voltage electrical lines for RTE, coastal landfall and offshore wind farms,” notes Joussin. Another promising sector is the transport field (motorways, airports, high-speed and freight railways, urban tramways and container ports), he adds. The situation remains stable and main trenchless projects are focused in the power sector with the new interconnection between Spain and France. “There are also many other little jobs in traditional markets, such as water and gas,” Ortega says. “The gas network is almost complete and there are no big expectations for new and exciting projects. The industry has evolved rapidly and we are now in a phase where contractors ask IBSTT for alternatives to traditional trenching techniques.”

2015 expectations Many players consider that 2015/16 will be a transition time in France, with the economy recovering and more opportunities for trenchless. “New regulations or national recommendations, currently under discussion, covering the pipeline industry and clearly mentioning trenchless technologies as adequate solutions will help to consolidate the business,” Joussin comments. In the UK, with the AMP6 settlement and other utility determinations established, the industry should see increased activity over the coming months. De Boer expects a stable trenchless market in the Netherlands, with a small increase in the turnover of the rehabilitation market, as well as in the installation market this year. AATT also expects an increase of no-dig projects for 2015/16 in Austria. “The Iberian market is growing by 15% in terms of these technologies, but to understand this data we must take into account that 10 years of investment have been lost,” Ortega states.

A coastal application of trenchless technology in Iberia

“Young engineers change their minds quickly but decisionmakers are reluctant to change the way projects are designed”

tHe next generation Education. Environment. Economy. Trenchless technology could be an influence on all three. “In the next 25 years our main issue will be less disruption for people, the economy and the environment in a very crowded country,” de Boer notes. “Less disruption also means that less space is available for works, and limited or no hindrance is expected in environmental areas, as well as for traffic by road, water and rail.”

The UKSTT is promoting academic courses in trenchless tehnology

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Delegates gather for dinner at the IBSTT’s 2014 event

In the next 25 years NSTT sees a stronger shift from new installation to rehabilitation and an upcoming market for the complete trenchless removal of unused pipes and cables. AATT would like to see innovative pipe-rehabilitation technologies promoted better. In order to nurture the next generation of workforce, and ensure that the industry takes off over the next two decades, the only way to grow is through education. “Universities are very interested in including short Master courses for their students, and the concept of ‘smart cities’ is helping politicians

to understand that technology is available for everybody at a reasonable price,” Ortega says. “It would be very important getting a systematic education from technical schools to university degree. That’s a very special field at the TU Wien [The Vienna

University of Technology],” echoes AATT. The UKSTT notes increased emphasis in engineering Continuing Professional Development courses in the understanding and awareness of trenchless systems, materials and techniques and the major, transformatory, environmental and social benefits from their greater use. “CO2(e) savings are potentially huge and must be pursued,” the society says. By 2040, FSTT expects to see lower costs linked with a bigger market, and more efficiency of equipment, products and operators.

In addition to the persons named in this article, TW would like to thank the following for their contributions: Peter Crouch (technical secretary) and Ian Vickridge (vice-chairman) of UKSTT; and members of the board of AATT / ÖGL: Wolfgang Steinbichler, Manfred Loidl and Silke Cubert

taking its toll An underground structure and utility survey on the Dartford Free Flow Project in the UK led to enhanced safety practices and time and cost savings Catsurveys’ Mobile Ground Penetrating Radar (MGPR) was used to survey underground infrastructure

ince its ‘final’ opening over 20 years ago, the Dartford River Crossing has become the busiest estuarial crossing in the UK, with over 130,000 vehicles on average using it to commute every single day. Forming a key part of the M25 motorway, the Dartford Crossing provides motorists with a vital link between Thurrock and Dartford and has regularly seen congestion due to its controversial and ageing tolling system made up of

Project details Project: Project value: Client:

Dartford Free Flow Project £62,000,000 (US$96.9 million) Balfour Beatty Construction Services UK Scope: To identify all utilities and under ground infrastructure and deliver in 3-D BIM to be combined with BBCSUK design data Project duration: 3 weeks

12 toll booths situated on both sides of the M25 motorway. In early 2014 Balfour Beatty Construction Services UK (BBCSUK) was tasked with undertaking major congestionrelief works to replace the tolling infrastructure with a new Automatic Number Plate Recognition (ANPR) system, with the overall goal to alleviate the traffic along this busy motorway section.

the challenges Carrying out works on any live motorway will always come with its fair share of challenges,

including the nature of the Dartford Free flow scheme, its location and the requirement for demolition of the toll booths situated within the centre of the carriageways. One of the more difficult obstacles faced on this project by BBCSUK was the requirement for a full underground structure and utility survey of both sides of the M25 on the run-up to the existing tolls; a service that when carried out using traditional trace-andrecord methods – e.g. Electro Magnetic Locator (EML) or Push Ground Penetrating Radar (GPR) – is a timely and risky operation

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Western europe

The flow of traffic through the toll gates at the Dartford Crossing

“Maintaining the public’s confidence in BBCSUK as a contractor was of great importance to the company and on such large-scale projects is typically quite a difficult feat to achieve”

requiring operatives to physically enter the carriageway. Although achievable, it is certainly not the ideal solution for such an unpredictable and fast-flowing motorway. A large-scale traffic management set-up including several lane closures would have been one way to address the healthand-safety issues involved with carrying out the underground utility mapping. However, the knock-on effects of reducing the number of open lanes on such a vital road would cause serious logistical challenges on the already congested crossing. Maintaining the public’s confidence in BBCSUK as a contractor was of great importance to the company and on such large-scale projects is typically quite a difficult feat to achieve, especially when the public can visibly see you increasing their journey times daily for long periods. This is why BBCSUK urgently needed to find a solution that would enable the mass data collection of underground assets and infrastructure but with minimal impact on commuters using the crossing and provide quality data while reducing the risks to survey operatives.

early engagement BBCSUK engaged with Catsurveys at an early stage in the planning process, enabling the latter to advise and consult on the best practices to adopt when carrying out such a bespoke survey. The Free-Flow project was divided into two sections highlighting online and offline

Project stats

74,108m² of surveyed area for on-site man hours 9,500% saving on complicated traffic management 9,798% saving man-hours’car riageway entry, cut from 4,743 8

areas. Online areas were made up of live roads and active site areas, whereas the offline sections were zones that had zero traffic-management requirements and either limited or no risk to on-site personnel. Utilising traditional trace-andrecord methods, such as EML and push GPR, Catsurveys carried out a full utility survey to detect all mains and services within the ‘offline’ survey areas. Undertaking works within the ‘online’ areas, however, was not as straightforward and required a more innovative approach. Catsurveys suggested the use of its newest piece of equipment and international award-winning system, the Mobile Ground Penetrating Radar (MGPR), for use on these live areas. Its ability to carry out mass GPS/GNSS positional recordings of underground utilities, infrastructure and anomalies made it the obvious choice when choosing a solution to complete the survey efficiently while reducing the health-andsafety risks typically associated with these types of works. Towed by a vehicle, when deployed the MGPR has a surface footprint of 2.02m x 2.10m and a data-collection speed of up to 15km/h, requiring limited to no traffic management and the versatility to be used both during the day and at night. The use of the MGPR system enabled the company to collaboratively plan its works with BBCSUK so that there was

minimal disruption to road users while maintaining a high-quality survey data result. In early October 2014 the company officially completed the full 3-D underground structure and utility survey of the Dartford Crossing of both the online and offline areas. Detecting all mains and services, Catsurveys was able to combine its findings with BBCSUK’s own 3-D building information model (BIM) to carry out a clash-detection analysis, which highlighted possible problem areas where further intrusive investigation works may need to be carried out.

ConClusion Combining the MGPR data with other specialist technologies on offer such as EML, topographical survey data and digital design data enabled Catsurveys to

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create a unique, intelligent 3-D deliverable that provides a vision of below-ground infrastructure and anomalies before any intrusive survey works being carried out. It provided BBCSUK with essential information of where to carry out intrusive works and has allowed the contractor to make the best informed decision possible before breaking any ground. This information has helped reduce risk, cost and time, enabling collaboration between design teams and on-site personnel. Catsurveys believes its MGPR system, operatives and data quality are the main reason why there have been zero strikes on the Dartford Free Flow Scheme, in line with BBCSUK’s policy. After working closely with BBCSUK for the past few months, Catsurveys’ relationship has grown and it is working with the contractor again on a variety of new projects this year.

Cut-away illustration of how MGPR ‘sees’ infrastructure below the ground surface

“After working closely with BBCSUK for the past few months, Catsurveys is now working with the contractor on a variety of new projects this year”

The toll line at the Dartford Crossing

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pipe rehabilitation

Flexible solutions at the fingertips Geopolymer solutions boast several advantages for the rehabilitation of large-diameter pipes Minimising disruption in congested areas (such as Hong Kong) is vital

“Degrading pipes in most urban areas are often located directly under other critical infra structure”

heck your favourite news outlet today. Whether it’s CNN, the morning news, The Straits Times in Singapore, The China Daily in Shanghai or even a local blog, you are likely to read or hear a failing-infrastructure issue. While most related events that become newsworthy are the result of highly visible structural failure, the public never sees the critical issues in many hidden assets. The deteriorating conditions of building, bridges and especially roads are easily seen and experienced daily, but the state of culverts, sewers and underground pipelines are generally unknown, save for owners or engineers directly associated with the asset. An estimated 3,400 miles (5,440km) of wastewater pipelines – roughly the distance from New York (US) to London (UK) – are repaired each year in the US. The vast majority of these rehabbed pipes are relatively small (less than 8in (203.2mm) in diameter) as the water authorities and municipalities look to maximise impact with limited budgets. Repairing larger pipes (greater than 48in) often brings higher associated costs and increased disruption to the community. Degrading pipes in most urban areas are often located directly under other critical infrastructure such as major roadways, buildings, or other assets, making typical

dig-and-replace technology impractical. As a result, trenchless rehabilitation options such as pipebursting, cured-in-place lining, slip lining and spray-on lining systems have become more prevalent. Another one of these newer systems – spin casting of a geopolymer – is actually based on technology that has its root in the past but is taking performance to a much higher level.

history’s technology today French researcher Joseph Davidovits coined the term “geopolymer” to describe a class of cement formed from aluminosilicates. While traditional Portland cement relies on the hydration of calcium silicates, geopolymers form by the condensation of aluminosilicates. Dmitry Glukhovsky and his

co-workers first used geopolymers in trial concrete applications in the Soviet Union after World War II, when they were then known as “soil cements”. Further historical research conducted by the Berkeley Lab has revealed that the same base pozzolanic materials used for geopolymers may have been used to create Roman cement. However, simply adding these materials to a traditional Portland mix, which relies on the hydration of calcium silicates, does not create a geopolymer. In fact, adding fillers that do not react into the system can actually degrade properties. The kinetics and thermodynamics of geopolymer networks are driven by covalent bond formation, which form essentially an “engineered stone”. Likewise, the use of geopolymers in modern industrial applications is becoming increas-

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pipE rEhabilitation

ingly popular based on both their intrinsic environmental and their performance benefits. In order to create a high-performance “pipe within a pipe”, traditional geopolymer formulations require the aluminosilicates to be combined with a solution of sodium or potassium silicates that have been dissolved in water. Installing these formulations requires high water ratios, which ultimately degrades their strength and requires a thicker final product to meet the flexural strength requirements of the rehabilitation. The GeoSpray system, produced by Milliken Infrastructure Solutions, is a formulated geopolymer repair mortar devised to meet all the physical and chemical requirements for rehabilitating sewer and storm-water structures. This system has been specially formulated to provide several key benefits to the contractor and asset owner. Once water is added to the geopolymer at the job site, it can simply be centrifugally sprayed inside an existing structure that has been properly prepared. Unlike traditional commercial geopolymers, the GeoSpray material is a “just add water” job-site solution as the entire system is contained within original powder formulation, allowing a single-step addition. The proper selection of proprietary aggregates allows the GeoSpray material to maintain easy pumpability up to 500ft (152.4m) within a pipe and still be centrifugally cast into large-diameter pipes without clogging or damaging nozzle performance. The most common method when considering the rehabilitation of large-diameter pipes is currently cured-in-place-pipe (CIPP), which is based on a resin-impregnated felt tube of either fibreglass or polyester. These systems date back almost 40 years and have a history of high performance. As such, an ASTM standard (F-1216) has been established to guide usage and

design for the industry. The final structure resembles a plastic pipe, with liners well suited for very acidic environments. However, as operators get into larger diameters, especially above 48in in diameter, the use of CIPP presents some potential issues and limitations. Once the curing of a CIPP liner begins, it must be closely monitored and controlled until completion. Though generally not a challenge in smaller diameters, the curing process using water, steam or UV light can take days for a largediameter pipe. Considering that the flow must be rerouted, or bypassed, for the duration, this can quickly become a costly process. Another disadvantage of CIPP is the fabric’s tendency to wrinkle or tear when going around bends or dealing with jagged or rough surfaces. Although manufacturers have taken several steps to improve performance in this regard, the risk stills exists. When using a spin-casting system with a geopolymer, the

process is extremely flexible and can be started and stopped as needed by the asset owner, reducing disruption to the community. Spin casting, or even hand spraying, the GeoSpray system also allows contractors to work with a variety of pipe conditions and shapes.

ExamplE from asia In a recently completed project in Hong Kong, the water authority evaluated a number of trenchless methods as alternatives to replacing a deteriorated pipe in front of a local hospital. CIPP was a viable solution, but due to the GeoSpray geopolymer spray equipment is small enough to fit down a 500mm manhole

GeoSpray geopolymer lining is suitable for largediameter pipes

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pipe rehabilitation

“The flexibility of geopolymer mortars makes them an excellent choice for the toughest sewer repairs”

short hours in which to work each day, the fumes from the resin in close relation to local residents and hospital patients, and the steep slope of the road, this option was rejected. Instead, the water authority chose to apply a GeoSpray geopolymer lining that was machine-sprayed to create a new structure lining, repair leaking, and return the pipe to its original shape. A mechanical sled system was used to apply the geopolymer liner to meet the engineer’s required 38mm thickness. While the GeoSpray geopolymer material can be placed up to 75mm thick in a single pass, two passes of approximately 19mm helped achieve the design requirement. This flexibility allowed the contractor to maximise application time each day, resulting in a more cost-effective project. From start to finish, the full project was completed ahead of schedule and on budget. As trenchless technologies continue to supplant dig-andreplace, it is good to know that there is an emergent technology in the toolbox for engineers, contractors and asset owners. The flexibility of geopolymer mortars makes them an excellent choice for the toughest sewer repairs.

Irregular shapes can pose a difficult rehabilitation situation

This article was written by John Hepfinger, global market manager, Storm & Sanitary, Milliken Infrastructure Solutions

the pipe that came in from the cold Matt Timberlake, vice-president of contractor Ted Berry Company, talks to TW about CIPP works during a New England cold snap

Installing the UV light train into the manhole and preparing to cure the liner

uring spring, US$1 million in sewer and pipe works took place in a picturesque beach town on the southern tip of Maine, the northernmost state on the east coast of the US. In a combined project, York Sewer District and York Water District oversaw works on Church Street and Shore Road in York. The Church Street project involved replacing existing lines with bigger mains at a cost of $255,000 for the water district and $200,000 for the sewer district. The old piping had structural defects and leaks in the joints that caused water to come into the sewer system. As the clean groundwater

enters the sewer system, it has to be pumped through the waste-water treatment plant and

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pipe rehabilitation

Q&A session

Ted Berry Company project team, left to right: Matt Timberlake, Tyler King, Andy Bryant, Matt Bronish, Shawn Ready, Dave Bilodeau, Isaiah Bean and Matt Therriault

What is Ted Berry Company’s history and experience with CIPP?

Ted Berry Company has been performing trenchless rehabilitation and renewal for over 10 years. However, UV CIPP is our newest service offering and has complemented the company’s core services well. Ted Berry performs pipe bursting, sliplining, sectional CIPP point repairs and traditional felt CIPP for projects of small diameter and length. The company recently performed a CIPP sectional point-repair project under a major New England highway that consisted of installing repairs inside existing and newly constructed storm drains from 15in to 48in in diameter to repair structural defects and joints that did not pass the final inspection by the owner.

treated, which adds expense to the project. Most of the 1,100ft (335m)

How is CIPP received in the construction community?

Traditionally, many parts of North America are very receptive to rehabilitation by CIPP. However, many areas of the country, believe it or not, have still either not heard of the technology or do not understand the technology and how it can be used to structurally rehabilitate buried pipes without the need to dig. In many areas we still see lining specified only on areas where digging would be overly invasive or disruptive, when in many cases it should be considered as part of a long-term CIPP, as it is much more cost-effective than excavating and laying a new pipe.

How is Ted Berry Company finding demand at present?

2014 was a good year for Ted Berry and the company continues to see growth in water-pipe rehabilitation and storm-drain rehabilitation, as those systems are traditionally run to failure and, when they do, the results are very noticeable and disruptive to the public and economy. Ted Berry has a great outlook for 2015 and looks forward to continuing to educate public utility system stakeholders to how trenchless technology works and how it can help them manage their collection and distribution systems long term through reliable and cost-effective solutions.

section of aged and decaying clay pipes was replaced using traditional open-pit excavation and replacement techniques (at depths of around 10ft) where trenchless could not be employed.

time for trenchless Conservationists will be pleased to read that 414 linear feet were rehabilitated using ultravioletcured cured-in-place pipe (CIPP) in two separate runs. One 44ft length had an internal diameter of 8in and the remaining 370ft was 12in ID. “The project was originally scheduled for three days and was completed in three days, even though the Maine spring did not fully co-operate and we had below-freezing tempera-

tures and snow on one of the installation mornings,” Matt Timberlake, vice-president of Ted Berry Company, tells Trenchless World. Timberlake identified challenges as being co-ordination with a nearby excavation project that was replacing water, storm drains and a section of sewer that had failed and could not be rehabilitated with CIPP. Seven crew members worked on the project in total – a senior project manager, construction manager, project supervisor, ultraviolet CIPP cure-system operator, blower-system operator, and two technicians. Reline America from Saltville, Virginia US, manufactured the fibreglass pipe and relining materials.

“The Maine spring did not fully co-operate and we had belowfreezing temperatures and snow on one of the installation mornings”

Preparing the UV light train for installation into the manhole

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auger boring

Keeping the traffic moving Replacement of an aged water main under busy routes feeding traffic to the world’s largest building called for careful planning Overview of Highway 99 distributionsystem improvement programme

he Alderwood Water and Wastewater District (AWWD), located roughly 20 miles (32km) north of Seattle in Washington, was formed in 1931. The area has seen rapid growth and the district now serves over 214,000 customers. In 2012, AWWD began construction of the Highway 99 distribution-system improvements that consisted of the replacement of 80-year-old water mains along Highway 99 and new pipe under State Route 525. These are two major highways carrying Boeing workers to the Everett factory (home to the world’s largest building by volume, housing 42,000 employees), at an Average Daily Traffic (ADT) volume of 38,900 and 61,000 vehicles each day respectively. The basic problem is common to many utility projects: installing new or replacement water and sewer lines, while minimising both safety concerns and impacts to the motoring public. However, when the road involved is a six-lane arterial with a speed limit of 45mph (72kmph), the challenge is to avoid any daytime road interference.

Annual Traffic Report, State Route 525 saw an ADT of 62,000 vehicles on average in 2013 (WSDOT 2013). Construction of the proposed project without disrupting daytime traffic to and from Boeing’s plant was paramount to the overall success of the project. Boeing runs three shifts at the plants, so shift-change times had to be taken into consideration during the planning.

“Construction of the project without disrupting daytime trenchless solutions traffic to During the preliminary design and from phase, in evaluating alignment Boeing’s Potential traffic imPacts and construction options, several plant was In 2011, the federal government, project goals were identified: paramount through the American Recovery • Minimise the possibility of damaging the fragile water to the overall and Reinvestment Act, commissioned a transportation report for mains during construction, success of the Evergreen Way/Highway 99 failure of which would disrupt the project” Revitalization Plan. The report traffic and potentially underidentified Evergreen Way/ Highway 99 as a highway of regional significance within the AWWD project area. According to the 2011 Transportation Report, Highway 99 south of Airport Road currently has an ADT of 38,900 vehicles (Perteet 2011). According to the 2013 Washington State Department of Transportation (WSDOT)

• • • •

mine the road section; Avoid existing utilities where possible to minimise construction conflicts and utility relocations; Minimise water-service interruptions to businesses; Minimise surface restoration within the paved right-of-way; and Minimise traffic impacts.

The risks in using the trenchless techniques included boring into unknown utilities, heaving the road, groundwater seepage, the casing veering outside of tolerances, hitting a large boulder and other more minor risks. These risks were evaluated and in light of WSDOT’s stance on not allowing open-cutting the roadway for transverse crossings, the risks were deemed acceptable. The design called for the installation of three waterline crossings of Highway 99 and one crossing of State Route 525. The crossings of Highway 99 included both water-main replacements and future pressure-zone continuation. The crossing of State Route 525 was part of the concept that eliminated a significant portion of high-cost work along the east side of Highway 99 and allowed the district to eliminate additional ageing infrastructure.

traffic control The overarching goal during construction, other than pipe replacement, was the safety of the travelling public and all parties involved in the project. The contractor’s work hours

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were different for northbound and southbound traffic and depended on whether a shoulder, one-lane, or two-lane closures were required for any given stretch of the several mile-long project. Typically, work hours with lane closures were limited to between 11pm and 5am, which did not allow much time for production. The bore-pit locations were designed to be off the used part of the road, so that work could be completed during the day for more efficient production (and lower cost) and less inconvenience to the public. Some of the tie-in excavations did require construction in the roadway, since the alignment of the water mains was in a travelled lane, and required cutting out a piece of the bore casing in the middle of the highway.

ConstruCtion sequenCing The contractor had flexibility in sequencing the construction work on the highway. The district expected that two or three crews would be working at any given time on the project. Because of the way that the traffic-control work was paid (on a per-unit basis), the contractor had more crews than anticipated with many flaggers on site, so the traffic-control cost was higher than originally projected. There were many drunk-drivers observed, and a few minor incidents and near hits, with additional police presence to minimise the possibility of accidents. The sequencing of the borings was dictated in part by the general contractor’s approach to the project, with the order of the bores following the contractor’s work. The casings were installed during daytime work in a straightforward manner without issues, except for where contaminated soil that was discovered at one bore pit. The contamination delayed the start of the bore for several days while tests were run to determine

Bore 1: Highway 99 and State Route 525 The site of the project’s first auger bore

The first auger-bore crossing of Highway 99 occurred approximately 300ft (91.4m) north of the off-ramp from State Route 525 to Highway 99. This called for the installation of 115ft of 36in (914.4mm)-diameter steel casing, which would house the 12in-diameter ductile iron carrier pipe. The boring had to cross six lanes of traffic while avoiding storm, fibre-optic, phone, gas,

water, and underground and overhead power lines. The jacking pit was constructed in an existing WSDOT access road on the east side of Highway 99, while the receiving pit was built on the west side. The size of the jacking pit was limited to a 40ft by 40ft temporary construction easement. The bore was installed at a depth of approximately 14ft below Highway 99.

“The traffic-control cost was higher than originally projected. There were many drunkdrivers observed, and a few minor incidents and near hits”

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auger boring

Bore 2: Highway 99 and Russell Way Aerial view of the site for the second bore

The second auger-bore crossing of Highway 99 occurred just south of Russell Way in front of a property with a busy recreational-vehicle (RV) sales business. This road crossing was unique because it required the installation of two separate carrier-pipe systems: a 12in ductile iron pipe for the 724 pressure zone, and a 16indiameter pipe for future extension of the 635 pressure zone. This was accomplished through the installation of approximately 80ft of 42in-diameter steel casing, which housed both carrier pipes. The jacking pit was again installed on the east side of Highway 99, but this time it was within the RV sales lot. the contaminants and the affected soils were removed. The timing of the tie-in excavations was co-ordinated and required lane closures. This type of work was completed at night per the permit conditions.

Two stages in the boring process for the second bore

A temporary construction easement was negotiated with the property owner and required that the contractor construct the auger bore within tight site constraints. Access to the RV lot needed to be maintained as well. The receiving pit at this crossing was located within the Highway 99 ROW, which required that the intertie be constructed at night. This crossing was installed at a depth of approximately 15ft.

auger-bore construction Each of the proposed auger bores presented its own unique challenges. Each of the jacking and receiving pits had to be located within the existing right of way (ROW), or additional easements

Bore 3: Highway 99 and Airport Way

â&#x20AC;&#x153;Each of the proposed auger bores presented its own unique challengesâ&#x20AC;?

Third bore location

The final Highway 99 crossing was just south of Airport Road. The new pipe serving the 724 pressure zone had to cross from the west side of Highway 99 to the east and then travel north along it across Airport Road in parallel with a new 12in-diameter ductile iron waterline serving the 635 pressure zone. The crossing was constructed using a 36in-diameter steel casing, 77ft long. The jacking pit

had to be obtained to allow for construction. The pits had to be situated so that they did not interfere with the constant traffic flow and contractors could not move or relocate existing utilities. In addition, two of the four auger-bore installations required that the contractor excavate intertie pits within the travelled lanes of Highway 99 at night to allow for the proper alignment of the proposed water installation. Each of the four auger bores is discussed in further detail in the boxes on these pages.

conclusion and summary Work under way on the third bore

was designed on the west side of Highway 99 in a vacant lot. The receiving pit was in the eastern turn lane for Airport Road, and required night construction for the final intertie. This crossing was at a depth of approximately 14ft below the road.

The success of this project rested heavily on the design research and details, construction sequencing, and selection of good bore and receiving pit locations. Additionally, selecting the appropriate method of trenchless construction avoided major problems during construction. The design team conducted a detailed alternatives analysis to determine the most cost-effective and least risky way of replacing the waterlines in Highway 99.

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The major project risks included construction equipment or vibrations impacting the deteriorated mains, causing a major water-main break in the heavily travelled highway and protecting the safety of the participants and public during construction work, most of which occurred at night with cars speeding by. The team oversaw the installation of new waterlines to improve the pressures in the project area while minimising project risk. The effort was facilitated without affecting existing utilities or interrupting water service throughout construction. Additionally, surface restoration and traffic impacts during construction were minimised. The combined strategies allowed the AWWD to replace this critical infrastructure without significant impacts to the roughly 36,000 local customers, the near-by industries, including Boeing, or thousands of daily commuters. These important improvements are a vital section of the 660 miles of water main used to reliably deliver 9 billion gallons of potable water a year to the district’s residents and businesses.

Bore 4: State Route 525

Views of the final crossing bore

The auger-bore crossing of State Route 525 was part of the low-pressure improvement phase of the project. It was developed by AWWD and Stantec staff to minimise construction on Highway 99 while eliminating additional ageing waterlines. During design it was determined that a route alternative for the replacement of the 635 pressure zone piping could reduce the need for approximately 6,000ft of pipe on Highway 99. The bore involved installing 115ft of 36in-diameter steel casing to carry a 12in-diameter ductile iron pipe across State Route 525. A jacking pit of approximately 20ft by 35ft was

installed on the east side of the road roughly 190ft south of 149th Place SW. The receiving pit was installed in the ROW for State Route 525. The receiving pit had to be installed on a sloped area to avoid existing utilities, which complicated the work. At its deepest point, the casing was 11ft below the road.

“The effort was facilitated without affecting existing utilities or interrupting water service throughout construction”

Boring under State Route 525

This article is an edited version of ‘AWWD uses auger boring to keep the traffic moving’ by Erik Waligorski and Laurie Fulton from Stantec, and Jeff Clarke and Paul Richart from Alderwood Water and Wastewater District. Original presentation given at NASTT’s 2015 No-Dig Show. ©North American Society for Trenchless Technology. All rights reserved. www.nastt.org Editorial Editor Luke Buxton T +44 (0)20 7216 6078 E luke.buxton@aspermontmedia.com F +44 (0)20 7216 6050

Head of production Tim Peters Senior sub editor Jim Adlam Sub editor Woody Phillips

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