Boston Big Dig Project Profile

8/6/2019 Boston Big Dig Project Profile

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PROVEN AND EFFECTIVE

Copyright 2006. Turbo-Seal is a registered trademark of RE-New Systems, Inc. All right

P R O J E C T P R O F I L E

Cutting through the heart of Boston, the original ele-

vated six lane Boston Central Artery displaced 20,000residents and limited the economic vitality of Bostons

North End and Waterfront neighborhoods. By the timeit was demolished, the antiquated roadway carried up

to 200,000 vehicles a day, 125,000 more than the

design limit. This overload created eight hours of dailybumper to bumper traffic, an accident rate four times

the national average, and acted as a large drag on the

quality of life in Boston. Something had to be done.

In the early 1980s, the Big Dig was conceptualized toalleviate the crippling traffic on the Central Artery. The

Boston Big Dig project is one of the most ambitiousAmerican engineering projects ever undertaken. Today,

the eight-to-ten lane underground Central Artery can

accommodate 250,000 vehicles a day.

Constructing 7.8 miles of new highway (161 lane miles

in all), over half in tunnels, while keeping Boston openfor business was a formidable challenge. To keep the

city operational, special care was given to the designand scope of work. The newly constructed Central Ar-

tery was unprecedented in scale. It required theplacement of close to 4 million cubic yards of concreteand the excavation of more than 16 million cubic yards

of soil. Enough soil was moved to create a 120 acrepark on top of a reclaimed island landfill. Lead JV

partner Bechtel and Parsons Brinckerhoff Quade &

Douglas consulted on the design, construction man-agement and program management for the project

owner. With the projects substantial completion markpast, the new Central Artery has greatly improved traf-

fic, created over 320 acres of new park land and now

adds to the quality of life for people in the city of Boston.

Despite the new Central Arterys successful alleviationof traffic concerns and the improvements made to the

quality of life, there was public discontent concerning

the projects 10+ billion dollar price tag and that leakswere found shortly after the tunnel was opened to traf-

fic.

A New Approach, The Big Dig, Boston, MA

Figure 1: Old Central Artery at rush hour

Figure 2: New Central Artery

Figure 3: Economic development and new parkland

Phone: 612-872-1900; 866-99-RESYSWebsite: www.re-systemsgroup.com


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PROVEN AND EFFECTIVEhone: 612-872-1900; 866-99-RESYS

Website: www.re-systemsgroup.comCopyright 2006. Turbo-Seal is a registered trademark of RE-New Systems, Inc. All right

Most public discontent can be traced to the fact that

the tunnel was actually opened two years before itsscheduled completion. The tunnels needed to be

opened to motorists to allow for the demolishing of theelevated roadway. Motorists drove through a partially

completed tunnel system while contractor crews

worked to seal leaks as a part of the ongoing construc-tion process. It is industry standard to grout new tun-

nels to seal them against ground water, snow and rain.In the case of the Big Dig, the size and scope of the

project magnified the visibility of the grouting and pub-

lic discontent.

During the construction process, contractors were di-rected to use waterproofing materials and techniques

accepted by the Federal Highway Administration.

Crews applied waterproofing materials to floors, roofsand other joint locations to minimize water leakage.

Many different types of waterproofing products wereused at different locations throughout the tunnel sys-

tem. In the year 2000, despite these efforts, inspec-

tors identified hundreds of leaks in 30,000 linear ft. oftunnel walls. A leak task force was assembled to fix the

leaks. Ongoing leak mitigation efforts have been in

process for the past six years. Special attention hasbeen paid to the interface of the soldier piles and the

slurry wall. It has been suggested that thermal expan-sion and contraction may contribute to some of the

leak issues.

After a complete inspection of the tunnel system in the

summer of 2004, the number of leak mitigation crewswas increased from 2 to 15 to meet the overall sched-

ule for leak mitigation. Project managers Bechtel/

Parsons have been responsible for monitoring and en-

suring the consistency and adequacy of each repair.

According to a Bechtel / Parsons report based on a

three-month investigation of tunnel leaks and related

issues, an independent panel of FHWA engineers re-

ported in March 2005 that the low-level leaks found


Figure 1: Water leaking down a slurry wall

Figure 2: Water pooling in the tunnel



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in the I-93 tunnels would be expected to occur to

some degree because the tunnel is constructed signifi-cantly below the water table. The report noted that

trained crews were proceeding systematically to stop the leaks by injecting them with appropriate sealants

and expressed confidence that their work would suc-

ceed. Their report concluded, The [Assessment] Teambelieves that the Project is adequately addressing the

tunnel leaks.

Mostly urethanes and acrylic based resins have been

used for leak sealing. Early in the leak repair process itwas found that some of the urethanes had the ten-

dency to revert. Some products were not ideally suited to adverse soil conditions and continuous wet/dry cy-cles. Materials that can respond to thermal expansion

and contraction and withstand adverse soil conditions

will be most effective in the long term.

Test Case: A New Approach

The Re-Systems Group, USA contacted project manag-ers from Bechtel/Parsons to offer them a case study

evaluation of a new approach to grouting repair at theCentral Artery. The RE-Systems Group, USA is bringing

the products and systems of RE-New Systems, Korea

and RE-Form Systems Korea to the US market. The Re-Systems Group, USA works to preserve assets and

natural resources through the development of high

tech materials and the creation of effective building

and repair systems.

The approach offered by Re-Systems Group, USA em-

ployed the use of Turbo-Seal, an innovative liquid poly-mer rubber infused with special adhesives. Turbo-Sealis an ideal solution for all types of structural water-

proofing and injection grouting. As an injection grout,Turbo-Seal is specially formulated to be compatible

with existing waterproofing membranes, resistant to

chemical attack and can adhere to wet surfaces. Turbo-Seal is one component, non-toxic, non-solvent based

and non-flammable.


Figure 1: Reverted urethane spilling out of drill hole



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Turbo-Seal does not completely cure and remains in a

gel type state, giving it the flexibility necessary to

weather the constant stress of thermal expansion andcontraction without debonding.

Turbo-Seal is injected to the backside of a structure to

stop water at its source, creating an effective restora- tive waterproofing membrane on the positive side of

the structure. Unlike most grouting pumps used withurethanes and other chemicals, Turbo-Seals pump

system is easy to use and maintain. Since Turbo-Seal

does not cure, cleaning the pump is unnecessary between applications. Application is also simplified by

not having to mix chemical components, limiting the

potential for misapplication.

After meetings with Bechtel/Parsons project managers,RE-Systems Group, USA was offered three case studies

at sites where water intrusion continued to persist even

after repair grouting work had been done. Turbo-Seal is the first non-urethane/acrylic based resin grout used

on the project. The Re-Systems Group, USA partnered

with McCourt/Obayashi for the installations.

Site #1: Slurry wall adjacent to a utility room.

Numerous methods for leak mitigation had been at-tempted at this site including the use of polyurethane

and acrylic based resin grouts. The site would be best

classified as experiencing a seeping leak. Injectionholes were hammer drilled through the five foot slurry

walls and Turbo-Seal was pressure injected close to thesoldier piles. Working from the bottom of the slurry

wall to the top, the course of one of the persistent leaks

was followed. Application consisted of drilling 5/8 inchholes followed by the installation of injection packers.

When counter flow of Turbo-Seal was achieved throughthe adjacent drilled hole, the injected port was capped

and the process repeated at the next drill point. An

electric rotor stator pump and a specialized high pres-

sure hand drill pump were used.


Figure 2: Site #1, slurry wall condition


Figure 1: Turbo-Seal injection method detail


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Injection pressure ranged between 600 1500 psi.

Where Turbo-Seal was applied, the leaks stopped.Turbo-Seal was effective where other products had

failed.

Site #2: Slurry wall adjacent to road way

A similar approach was used at site two. This slurry

wall was experiencing an active water leak. Holes weredrilled through to the backside of the slurry wall and

pressure injected at two locations simultaneously. One

injection point was injected at a pressure of 600 psi

while the other injection point was injected at 1500 psi.After three separate injection points were grouted, the

active water leak was stopped.

Site #3: Duct bank connecting vent building to tunnel

Site three was a more involved repair. Water was

found infiltrating a buried duct bank and its conduitssomewhere between a recently constructed vent build-

ing and the Central Artery tunnel structure. The water

infiltration had been leaking out of the conduits, fittings,and junction boxes in both the building and ramp andwas of concern to the long-term maintenance and op-

eration of the systems. Most of the leakage had been

observed at junction boxes and conduit fittings in thevent building as these are at the low point of the sys-

tem in the area.

During construction, the duct bank was excavated and

a waterproofing membrane detail was installed on the

top and two sides of the interface joints with the tunneland vent building. No membrane was installed under-

neath the duct bank. Subsequently, the duct bank ex-cavation was backfilled and an active paved parking lot

was constructed. Water was observed seeping in sincethe construction of the duct bank and subsequent to its

backfilling. Various repair methods had been at-

tempted, yet none had succeeded in


Figure 1: Slurry wall injection at site #1

Figure 2: Slurry wall injection at site #2



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stopping the water infiltration. Excavating the private

parking lot and exposing the below grade structure wasnot an attractive option due to increased cost, time and

effort.

The duct bank consists of a series of eleven 3 diame-

ter rigid, galvanized steel conduits carrying 480 voltelectrical feed lines to jet fans in the CNS (and other

tunnels) from the Vent Building 8 power supply. Thevent building is constructed partially above and below

grade with the conduits penetrating the exterior con-

crete wall of the vent building about 10 to 12 belowgrade into a concrete encased duct bank. The duct

bank is situated near and sometimes under the localwater table in the area. The duct bank travels a shortdistance underground and then penetrates into the

cast in place roof structure of a cast in place highwaytunnel in the Central Artery. At the penetration into the

tunnel a non-watertight expansion-deflection fitting is

installed on each RGS conduit, a concrete box castaround them, and foam filler board was placed be-

tween the concrete duct bank and the tunnel concrete.The duct bank at the vent building wall was cast directly

against the wall concrete.

A grout cutoff was installed immediately below the bot-

tom of the duct bank effectively sealing the gap alongthe foam filler and construction joint at both the vent

building wall and the tunnel wall locations. Turbo Seal

filled the void space around the expansion-deflectionfittings. Turbo Seal was compatible with the existing

waterproofing. Also, Turbo-Seals relatively high viscos-ity formed a mass in the vicinity of the joint. Because

Turbo-Seal is not subject to drying and shrinkage when

water table levels fall below the bottom of the duct

bank, it was ideally suited for this type of application.

Conduit runs were field confirmed by location pull/

junction boxes in the ceiling and drilling was targeted to

intercept the planned locations. Conduits were 6 to

12 above the bottom surface of the roof.


Figure 1: Drawings for Vent 8

Figure 2: Application team at Vent 8



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The drilling, angled upward, from the roof-wall interface

joint to intersect the void space constructed in the ductbank for the expansion-deflection fittings. Once pene- trated, Turbo Seal was injected until refusal was ob-

tained. All drill holes were patched with a fast set mor-

tar. Injections were repeated as necessary until refusal

was attained and leakage was stopped.

A series of holes were drilled laterally at 6 to 12

spacing to intersect the bottom of the duct bank and a

minimum of one gallon of Turbo Seal was injected ineach hole (6 spacing) or 2.5 gallons (12 spacing) or

until refusal was reached. Injections were repeated as

necessary until refusal was attained and leakage was

stopped.

Conclusion

Bechtel / Parsons completed a follow up inspection ofthe test sites two months after application. It has been

confirmed that Turbo-Seal has effectively stopped wa-

ter infiltration at each test site. The RE-Systems Group,USA is committed to helping the Central Artery stay dry.Turbo-Seals unique qualities as an injection grout

make it ideally suited for areas where other products

are ineffective or other methods too costly or time con-

suming.

Despite some challenges, the Central Artery is stayingdrier. In fact, it is now drier than most completed tun-

nels. Sealing leaks will be a part of the ongoing maintenance of the tunnel. The Massachusetts Turnpike

Authority will be responsible to maintain the Central

Artery for many years to come. Proven methods to dif-ficult water intrusion issues will be an important ele-

ment to any effective maintenance plan. With a com-mitment to an effective maintenance plan, the people

of Boston will have a Central Artery that they can be

sure will last for generations to come.



NOTICE: This report expresses the views of RE-Systems Group, USA

necessarily the views of Bechtel/Parsons, their subsidiaries or any o

affiliated party to the Boston Central Artery project. All views represehere allow no liability upon the publishers of this document and the o

of said views assume no liability for any ill will resulting from this doc

The information contained in this document is for educational as we

marketing purposes and as such anyone using this document must a

these views as statements of opinion and agrees to release the auth

from any and all liability.

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