Shani Wallis, TunnelTalk

There is a network of some 46.4 miles (74.2km) of light rail and metro rail services already in operation in Los Angeles. But tunnel collapses, sacked tunnel contractors, management upheaval, delays and cost increases have brought the wrath of public opinion against the project. Shani Wallis reports from Los Angeles.

Of all the sprawling conurbations in the world that need, but don't have, an efficient public transport system, Los Angeles in the United States was the most needy. As the largest city on the west coast of the United States, Los Angeles has grown up almost totally dependent on the private car and has long since been paying the price. Air pollution is notorious, traffic jams on the 12-lane freeways that snake across the metropolis are a fact of life, and getting around the city is practically impossible without a private means of transport. It looked like relief was on the way when, in 1980, the taxpayers of Los Angeles County agreed to a 0.5% sales tax levy to help pay for a city-wide mass rapid transit system, a figure increased to 1% in 1991. After the promise and enthusiasm of those early days the project has suffered a deluge of bad press. Tunnel collapses, sacked tunnel contractors, management upheaval, delays and cost increases have all brought the wrath of public opinion against the project, just when public support is vital to promote use of the Metro sections already in operation and extension of new sections into other areas. What is going on in LA and will the system ever reach its full potential?

Gaping hole in Hollywood Boulevard after tunnel collapse

There is a network of some 46.4 miles (74.2km) of light rail and metro rail services already in operation in Los Angeles, with another 26.6 miles (42.5km) constructed and a further 32 miles expected to be constructed by 2000. These are substantial achievements, as are the better ridership trends on operating lines than originally expected; all of which represents a major step towards the Los Angeles goal of having 400 miles of commuter rail services constructed by 2010. But those achievements and the goal is overshadowed by a succession of high-profile setbacks, particularly on the Metro Red Line tunnelling works. The tunnel collapse which opened a gaping hole in the road surface of Hollywood Boulevard in June 1995 represented the lowest point in public opinion ratings, a position from where the client, its design and management teams, and its contractors will have to work hard to recover.

Design
As far as excavation is concerned, tunneling under Los Angeles is not difficult. The material for the most part is dense dry alluvial deposits with consolidated sandstone and siltstone and a section of hard rock tunneling to take the North Hollywood Line through the Santa Monica Mountains. The most significant design and excavation considerations concerned the high probability of meeting natural gas and methane gas ingress - a legacy of LA's once-significant oil-producing days - and the area's frequent and sometimes devastating earthquake activity.

In these conditions, the 18.5ft (5.6m) i.d. running tunnels are excavated, for the most part, using open-faced, non-pressurized tunneling shields fitted with backhoes or pneumatic spade-type booms and are finished with a three-part lining system. First is an immediate or primary support of either ribs and lagging or precast concrete segments, followed by a full 1mm thick high density polyethylene (HDPE) membrane to prevent gas infiltration, and finished with a full circle 12in (300mm) thick lining of reinforced in-situ concrete.

Fig 1. Route map of the Los Angeles underground Metro Red Line

The parallel running tunnels lie about 20ft (6m) apart. They run, wherever possible, beneath the streets under a minimum of at least one tunnel diameter of cover and with a minimum curve of 1,000ft (300m) radius. A minimum 50ft (15m) probe is a tunneling specification to warn of pockets of gas, as are breasting plates and an overcut limitation of 3/8in (10mm) on open-faced tunneling shields. The specified line and level tolerance is 4in (10cm) on tunnel diameter. The hard rock tunnels through the Santa Monica Mountains are to be excavated using two refurbished full-face hard-rock Robbins TBMs and immediately supported with steel ribs before being finished with the HDPE membrane and in-situ concrete lining.

Organization
As implementation of the Metro began in the mid-1980s, the principal designer was the JV team comprising Daniel, Mann, Johnson & Mendenhall and Parsons Brinckerhoff, Quade & Douglas, which concentrated particularly on the underground construction design; Kaiser Engineers which was responsible for sub-systems; and Harry Weese & Associates as principal architect. Converse Consultants and Lind-bal-Richter Association were retained for soil and seismic analysis respectively.

Also, as it began, construction management of the Red Line Metro was in the hands of a JV team comprising Ralph M Parsons (no association with Parsons Brinckerhoff), Dillingham Construction and Deleuw Cather & Co, with Deleuw Cather withdrawing from the management organization when the team moved on to Segment 2.

The contractors involved on the various segments and contracts on the project to date are listed in Table 1.

Since then there have been several changes in management as the project has passed through its moments of turmoil and as the client organization itself felt the heavy hand of outside intervention.

At the start of the project, public transport in greater Los Angeles (principally bus services) were run for local county governments by the Southern California Rapid Transit District (RTD). As owner and operator of public transport, RTD pursued Federal US government funding for metro projects and collected the revenue raised by the 1% sales tax levy. In 1980 the Los Angeles County Transportation Commission (LACTC) was set up to manage implementation of new program initiatives which, in addition to the underground Metro system, includes improving bus services and heavy-rail services and developing the surface light-rail services.

In 1990 LACTC established a subsidiary, the Rail Construction Corporation (RCC), to manage the design and construction of new rail construction works, including the underground Metro sections. RCC was expected to improve administration and reduce, or at least control, costs. However, this did not prove the case and in mid-1994 the California state government ordered that RTD, LACTC and RCC be disbanded and merged into one management organisation. From the upheaval emerged the Los Angeles County Metropolitan Transportation Authority (MTA) whose brief it was to unify and consolidate LA's public transportation effort. In the shake-up the two design organizations (one for underground works and another for above-ground works) together with their common principal partners (Daniel, Mann, Johnson & Mendenhall, Parsons Brinckerhoff and Quade & Douglas) were also forced to merge, thus forming the Engineering Management Consultant to avoid duplicating engineering services and administrative costs.

Open-faced shields excavate dry and competent geology

Construction problems
This forced-rationalization, however, could not wipe out previous black spots - and there was worse to come. One of the first major setbacks for the project occurred in the early planning days when an unrelated event caused substantial rerouting of the original alignment.

Methane explosion In summer 1985, before work on Segment 1 had started, an explosion of natural methane leaking into a basement caused extensive damage in an area where the second segment of the Metro was routed. As a result, US Congress passed an injunction forbidding the Metro from following its original course. Instead of continuing down Wilshire Boulevard through the La Brea area and turning north to follow Fairfax Avenue towards the Santa Monica Mountains, the system had to be rerouted to turn north under Vermont Avenue and progress down Hollywood Boulevard before heading through the Mountains. Rerouting the alignment, it was said, would add two years and significant cost to Metro's design and construction program.

In-tunnel fire The second major event occurred in July 1990 when fire broke out on the Tutor-Saliba/Perini Segment 1 contract that brings the line from Union underground station to the surface maintenance depot. The fire started during the process of erecting the HDPE membrane prior to casting the final in-situ concrete, and it burnt out the timber lagging of a 219m length of tunnel. As a result a section of unsupported tunnel collapsed and had to be filled from the surface. Other sections avoided collapse because the ground had been pre-treated with grout injection to avoid excessive ground movement during excavation under the Hollywood Freeway and other major roads. After this, ribs and lagging was disqualified as a temporary tunnel lining, although it was used as immediate support on the open cut station boxes.

Ribs and lagging support banned in 1990 after collapse

Lining deficiencies
Further trouble occurred shortly after the Red Line Segment 1 opened in January 1993 after it was discovered that the tunnel's final in-situ concrete lining was less than half the specified 12in thickness in places. An independent team of professionals was engaged to conduct a thorough review of the Metro's design and construction, and the team was charged with inspecting the operating tunnels for cracks in the lining, signs of water ingress, and subjecting the lining to core sampling and non-destructive testing. The findings of the $1 million study confirmed that the lining was able to meet necessary design requirements but that honeycombing and numerous shrinkage cracks, some quite wide, were evidence of poor concreting work in a 6,000ft (1,824m) length of the twin tube tunnels between Union Station and Pershing Square. Leakage into the tunnels was minimal but it did indicate failure, in places, of the HDPE membrane.

To rectify these faults the contractor, Tutor-Saliba/J Groves JV, completed, at its own expense, an extensive program of cementitious grouting during the non-operating night hours to fill voids behind the thin concrete lining and to stem water leaks where identified.

Earthquake resistance
As a credit to the design and construction of the Metro, the operating system and those segments under construction performed well under the 6.8 magnitude earthquake that shook Los Angeles in January 1994. Water inflows and methane gas levels increased slightly after the event but soon receded. Some shrinkage cracks in the lining also widened slightly, but no serious spalling was observed and no lights or other fixtures fell as a result. This performance, however, could not save the project from bad press and further criticism.

Excessive settlement
In July 1994 excessive surface settlement of up to 9in (228mm) above the two tunneling shields advancing some 40ft (12m) beneath Hollywood Boulevard caused the Hollywood Walk of Fame to buckle and crack, damaging some of the famous celebrity stars embedded in the sidewalk. When water inflows through the open-faced tunneling shields increased, and wooden support wedges used to brace the shoulder joints of the precast concrete segments of the immediate support began to crush, tunneling on the Shea-Kiewit-Kenny contract was stopped.

Heavy steel support installed to arrest excessive settlement under Hollywood Boulevard

A study by the reconvened Tunnel Review Board established five contributory factors:
• water leaking from a broken supply line was said to
   be undermining the natural self-supporting stability
   of the soil
• the ground conditions were said to have changed in
   a subtle manner
• redistribution of the soil stresses had resulted in face
   losses
• downward movement of the tunnel crown segment
   was crushing the wooden wedges
• the wooden wedges (a contractor's alternative to the
   specified steel struts) were of inferior quality to those
   proposed and approved, and the required cement
   drypack filler between the precast segments was
   either non-existent or of very poor quality.

A series of remedial steps finally allowed tunneling to resume in January 1995. These included installing steel posts and supplemental supports in the tunnel, compaction grouting above the tunnels, chemical grouting from the surface ahead of tunnel advance, use of the specified steel struts instead of the wooden wedge alternatives, additional face control - including a second breasting table in the two open-faced shields - and inspection and repair of leaking water mains in the area ahead of tunneling.

Safety violations and cost increases
In addition to these high-profile events, the project to date has been plagued with fines for health and safety violations, serious and minor injuries, events on tunneling sites which had either caused program delays or increased costs or both, and incidents over which State and Federal officials have had cause to take action. In the summer of 1994, for example, it was reported in the Los Angeles Times newspaper that the Federal government withheld $1.6 billion in approved funds for Metro projects until such time as MTA officials could demonstrate that they were able to manage the project. The funding was released soon after; but then, in June 1995, perhaps the last straw in this apparent trail of poor management, poor workmanship and deficient construction supervision occurred when Hollywood Boulevard dramatically collapsed.

When ribs and lagging were banned the expanded precast concrete segmental method was used for primary support

Tunnel collapse
The collapse occurred during attempts by the same contractor, the Shea-Kiewit-Kenny JV, to correct unacceptable misalignment of the running tunnels as they left the working shaft and swung onto the Hollywood Boulevard alignment. The twin tunnels had been excavated using contractor-designed shields and a fleet of ex-Channel Tunnel 15m³ capacity side, self-discharging, muck cars supplied by Mühlhäuser of Germany. The curved tunnels immediately adjacent to the central working shaft had stood, since early 1993, temporarily lined with their 4ft (1.2m) wide x 1ft (300mm) thick rings of four precast concrete segments. Wooden wedges and drypack packings supported the expanded joints between the top of the four segments in each ring and the two side plates (Fig 2). The misalignment had to be corrected before installation of the membrane and casting of the in-situ concrete lining could begin.

To achieve this correction, the contractor, with the EMC's approval, proposed using the same method used before to correct a previous section of misalignment. A length of 20 rings had to be corrected by cutting out the top right quadrant of each ring, removing the two halves of the two adjoining segments, excavating to the correct alignment and relining the exposed ground with rib sections and wooden lagging. The process was then repeated for the lower right quadrant leaving behind a misshaped tunnel that would be corrected during the subsequent in-situ concrete lining.

Fig 2. Cut out of the precast concrete primary support caused the tunnel collapse

Work progressed untroubled until the 19th ring when, as the segment sections were removed, the ground behind was found to be soft and wet. It was suspected that a broken water pipe had progressively saturated the ground which, when left unsupported, had failed, and begun spewing into the tunnel unravelling rapidly to create the huge hole in the road some 60ft (18m) above. About 300,000 gallons of water and muck was said to have spewed into the tunnel in three hours.

Tunnel contractor sacked
In the stand-off immediately after the event, the client made the first move by sacking the contractor from the job. At the time, all tunnel excavation on the contract was finished, in-situ concrete lining was well under way, and the contract was some 80% complete. In a public statement the Chief Executive said that MTA "had lost confidence in (the contractor's) ability to perform work pursuant to the terms of the contract, in good faith, consistent with all applicable laws and regulations," continuing that MTA had "taken this action to protect the taxpayer investing in the Metro."

Since then, the unfinished work has been split up into eight packages and contractors working on adjacent contracts have negotiated to complete parts of the work as extensions to their own contracts.

Broken waterpipe spewed water and muck into the tunnel

In the meantime, as might be expected, the dismissed contractor has filed suit against MTA for "wrongful termination" of contract and the inevitable and costly chain of legal battling has been initiated. Shea-Kiewit-Kenny, the contracting JV, stated that they "deeply regret having to take this legal action" and that they "would prefer to finish the job" rather than "adding to the burdens of the taxpayers." The additional costs of terminating the contract, it was advised, would be "enormous." When Shea-Kiewit-Kenny was sacked off the job, the value of the contract stood at $178.6 million, of which Shea-Kiewit-Kenny had been paid $145.1 million. This had increased from the $163.5 million contract award value. Segment 2, of which the troubled contract was the largest, carried a final cost estimate of $1.517 billion (Table 2). The cost of completing the troubled Vermont-Hollywood tunnel contract was projected to increase its budget by 50-70%.

Construction management changes
Not to be excluded from criticism, the construction management aspect of the project also felt the heat of close scrutiny. When the Parsons-Dillingham JV was appointed as construction manager at the beginning of the project, it was expected that its contract would 'roll over' onto each subsequent phase. However, based on past performance, MTA decided to phase out the Parsons-Dillingham involvement and invited tenders for the construction management of the North Hollywood Line extension of Segment 3.

The successful bidder of the tender was the JMA Group, comprising Jacobs Engineering, Mott MacDonald (of the UK) in JV with Hatch of Toronto (Canada), and ACG Environments. However, an investigation initiated after objections by other bidders revealed irregularities by senior members of the MTA staff regarding the evaluation procedure. The award was cancelled and the contract rebid. Again the JMA was the selected bidder and in June 1995 the contract was awarded.

However, it did not encompass all of Segment 3A as tendered. Construction of Segment 3, with some 37 contracts, was valued at about US$1.3 billion. JMA managed eight of these, representing about 55% of the total. Parsons-Dillingham retained construction management of North Hollywood Station, the soft ground tunnels from North Hollywood to Universal City Station, and elements of the mechanical and electrical installations and operating systems. JMA managed construction of the rock tunnels through the Santa Monica Mountains plus the Hollywood/Highland and Universal City Stations.

Project Manager for JMA is Alastair Biggart of the UK who comes to Los Angeles from the Storebaelt project in Denmark where he was appointed Project Director of the twin tube undersea railway tunnel for the Danish client at about midway through that troubled project's history. As Biggart said in a telephone interview: "Things could have gone better here in Los Angeles and the project has drawn some heavy criticism in the press as well as from among State and Federal politicians. Another serious setback could well signal cancellation of the project and its future phases. We have a mission here to complete our sections as quickly and as efficiently as possible."

Table 2. Current construction costs of the LA Metro Red Line underground system as at mid-1995 stood at $5.76 billion and was broken down as follows Metro Red Line - Segment 1 Length 4.4 miles underground Opened 1993 Closing budget January 1989 Metro Red Line - Segment 2 Length 6.7 miles Current budget $1.517 billion Started January 1989 Due to open Western spur February 1996 Hollywood line March 1999 Metro Red Line - Segment 3 Total length 11.6 miles underground Total current budget $2.79 billion Segment 3 A - North Hollywood Line Length 6.3 miles Current budget $1.3 billion Started March 1994 Due opening May 2000 Segment 3B - Mid-City Extension from Wilshire/Western to Pico/San Vicente Length 2.3 miles Current budget $490.6 million Due to start Not set. Currently in design Due to open 2000 Segment 3C- Eastside Extension from Union Station Length about 3 miles Current budget $979.6 million Due to start Not set. Currently in design Due to open 2000

But might this be a mission impossible? While there is still the question of the unfinished sections of the stalled Segment 2 contract to sort out, work on the soft ground tunneling contract on Segment 3 from North Hollywood Station back to Universal City Station has not got off on a good start. Under the supervision and construction management of Parsons-Dillingham, Obayashi Corp, the contractor, is having trouble controlling excavation of loose dry 'sugar' sands and cobbles of the alluvial geology with its chosen open-faced tunneling shields. When Obayashi launched the first of its two shields from the North Hollywood access point in February 1995, face runs with every shove were causing losses of 2yd3 to 10yd3, and surface settlements of up to 10in (254mm). After a short stretch of stop/start progress, tunneling came to a standstill in April. Again the Tunnel Review Board was convened and concluded that the problems related to deficiencies in the design of the tunneling shields rather than differing ground conditions. To solve the problem Obayashi agreed to modify the shields by adding a hood to the leading edge of the shields, adjusting the position and power of the shield-mounted excavator, and improving the operation of the breasting plates. Modification of the second shield was carried out in the factory. It was then launched in June 1995. The first shield would have to be modified somehow in-situ.

However, although modified, the second shield has not performed much better. It has therefore been agreed that a program of systematic ground treatment ahead of tunnel advance, both from the surface and from the tunnel face, is to be used to consolidate the loose running sands and assist tunnel excavation. This added an estimated $2 million to the contract.

Design concerns
While questions about construction management, construction supervision and the causes of the various problems were a point of focus, questions could also be levelled at the particular design specifications adopted for the project. Why, for example, are the tunnels lined with a three-pass system of temporary support, plus HDPE membrane plus reinforced in-situ concrete? Would not the top quality one-pass bolted and gasketed precast concrete segmental lining systems, such as those used extensively in Europe and Japan and recently used on the railway tunnel under the Saint Clair River between the US and Canada, achieve the same objectives? A one-pass segmental lining, it had been suggested, would meet earthquake as well as normal ground loading specifications and prevent gas infiltration, but at substantial savings in time and money.

Open box station excavation has caused severe disruption to traffic and businesses during the construction phases, however mined stations using the NATM technique is considered too risky in certain ground conditions and in the hands of inexperienced contractors and construction supervisors. Kajima-Ray Wilson, however, has succeeded in introducing the soil mix diaphragm wall-type technique as immediate support for the Hollywood/Vine Station box. This, it is said, has resulted in faster bulk excavation and faster setting of wales and struts. Excavation rates of more than 2,000yd³/day are said to be almost four times the rates achieved using the traditional soldier piles and wood lagging systems.

The Mid-City Extension, as the next phase of the construction program, is in detailed design by the EMC and mined stations are expected to be considered once again; but perhaps the best opportunity for real value engineering design innovation will have to wait for the Eastside extension. In a radical departure from project management to date, MTA is believed to be considering a design-build-finance approach for this extension. This could well provide the contractual climate in which the tunneling industry in the US can break away from its litigious and traditional construction method constraints.

But the Mid-City and Eastside extensions are prospects for the future. The immediate concern for MTA, its design engineers, construction managers, and contractors remains firmly on providing positive solutions and steady-but-certain progress on work before the plug is pulled on what appears to be evident incompetence. Should that happen, as well it might, the US would be left with another useless set of expensive holes in the ground much like the defunct Super Conducting Super Collider project in Texas. Until such time that good news fights to get reported, it seems the busiest people on the LA Metro project are those on the Tunnel Review Board, the staff of bureaucrats in the administration organizations, and the many teams of lawyers involved in the claims and lawsuits that litter the project’s progress calendar to date.

References

Car capital takes to the underground - TunnelTalk, April 1988

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