TRG Review of Preliminary Engineering Phase I DEEP

TRG Review of Preliminary Engineering Phase I

DEEP GEOLOGICAL REPOSITORY PROJECT

Original signed by

Morris Medd

Original signed by

Wolf Seidler

Original signed by

Peter Tiley

Date: 2 October, 2009

Submitted To: Ian Pritchard, NWMO

Original signed by

Bill Smyth .

Original signed by

Evert Hoek

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mion

Text Box


TABLE OF CONTENTS

SUMMARY ................................................................................................................................................................ 3 T-H-E HANDLING ....................................................................................................................................................... 5 REPOSITORY VENTILATION ............. ........... ........................... ..... ..................................... .......................................... 7 SHAFT LINING ........................................................................................................................................................... 9 SHAFT EXCAVATION and LINING ............................................................................................................................. 10 UNDERGROUND EXCAVATIONS .............................................................................................................................. 11 FIRE ......................................................................................................................................................................... 13 MAIN CAGE and HOIST ........................................................................................................................................... 14 MAIN CAGE ROPE CHANGING ........................................................ : ....................................................................... 15 MAIN SHAFT AUXILIARY CAGE HOIST ..................................................................................................................... 16 VENTILATION SHAFT HOIST .................................................................................................................................... 17 VENTILATION SHAFT LOADING STATION ......................... ........................................................................................ 17 ROAD HEADERS ................ .................................................................................................. ..................................... 18

Application to Shaft Work ................................................................................................................................. 18 Application to Development .............................................................................................................................. 19

INTEGRATING A SINKING CONTRACTOR INTO THE DESIGN TEAM ......................................................................... 20 VARIOUS ................................................................................................................................................................. 21 APPENDIX - COMMENTS ON ROADHEADER EXCAVATION .................................................................. 23

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SUMMARY

1. The Technical Review Group (TRG) met with Hatch Limited (Hatch) during the week of 27 September 2009 to review the information Hatch and NWMO have provided us for the DGR Project.

2. The purpose of the review was to determine if there were any possibilities for fatal flaws in these designs as well as provide comments and recommendations to NWMO on various aspects of the project.

3. We have concluded that there are no fatal flaws in the proposed design. We do, however, have concerns about the provision for handling and storing the T-H-E (TIle Hole Equivalent) packages. We believe that if these units, as well as any other "Non-Fork Liftable" packages, can be reduced in size or repackaged, on surface, to permit them to be transported to the underground storage areas and placed there with fork lifts numerous simplifications to handling and storing these packages will result. Reduction in the height of the maximum package to 4.6m will lead to overall reduction in height of the cage, headframe and DGR level brow.

4. It is not clear why the main cage footprint is S.2m. The largest item we have data on is a part of the heat exchanger which is 3.6m wide. If the cage width could be reduced to 4m the shaft could be reduced to Sm.

S. We believe that the vent shaft is too small in diameter to be sunk efficiently. It should be increased to Sm.

6. The shafts should be sunk by conventional drill and blast methods because road headers have yet to been proven in hard ground for shafts of the sizes being contemplated.

7. Although road headers are an acceptable option for lateral development we recommend testing one in an exposed Coburg formation before approving this approach. Notwithstanding the possibility of using road headers for development, we believe that properly controlled blasting can produce an equal quality of rock face and an EDZ almost comparable to a road header.

8. The loading pocket design in the ventilation shaft should be altered so that its discharge path is vertically down and use a pan feeder to load the measuring flask.

9. A production rate of 1S0 tonnes per hour can be achieved using a pair of 8.0 tonne capacity skips in balance when operating at a maximum speed of 10 m/s. This will produce about 3000 tonnes per day (assuming -12 hours available for hoisting) to match the anticipated requirement of excavating approximately 2MT of lateral development in 2 years.

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10. From the information and analyses that were made available for review it appears that the Cobourg formation is tectonically undisturbed, very uniform, its strength is high in relation to the in situ stress field, it appears to have relatively few adverse structural features and its permeability is very low. These characteristics make it a favourable host rock for the construction of a stable waste repository. Further testing and analyses are required to confirm these observations but the TRG is optimistic that these conclusions will be shown to be valid.

11. The preliminary design of the emplacement rooms has been reviewed and found to be generally satisfactory. However, suggested changes in the ventilation system and in the placement procedures for large waste packages would result in rooms of lower height and hence the design will need to be re-considered.

12. The decision to design a dead end ventilation system has resulted in a design which requires extensive ductwork. The system will be complex to install and maintain and will introduce unnecessary extra steel to the project. We recommend re-designing the system to be a flow through with minimal ductwork. We believe that this approach will also reduce the total amount of excavation required for the repository. We have provided a sketch of a possible arrangement.

13. The original main cage hoist is satisfactory for the duties which will be required. The rope safety factors, tread pressures and T1 fT2 ratios are well within normal practice. The head ropes should be a low rotation, stranded design such as Trefileuropes Notorplast.

14. At present there is no provision for changing head or balance ropes on the main cage hoist. We recommend using a multi-rope, rope changing system. This equipment would allow all ropes to be changed from the surface. This represents a significant increase in safety for these procedures.

15. The Mary Ann ( auxiliary service ) hoist in the main shaft should be a two rope Koepe supporting a cage and counterweight. This option will eliminate the need for wooden guides and dogging systems.

16. The main cage should be equipped with dogs designed to operate on steel guides. This option will eliminate any arguments that the cage might fall if the headropes failed.

17. We see no necessity for using reinforcing steel in the shaft liner concrete. We believe that this exposes the concrete to the risk of spalling because the rebar will corrode. We also recommend replacing the ground control shotcrete with a poured concrete inner liner.

18. We did not receive any information on the work carried out to define fire hazards and how to respond to them. These studies will be required before the design can be finalized.

19. Proper HAZOPS analysis will have to be carried out on the various sections of the facility.

20. We would like to see an overall system schedule prior to the next meeting with Hatch.

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T-H-E HANDLING After reading the material provided before hand and with the benefit of two days of comprehensive

presentations by various members of the design team the TRG has identified only one issue that could

be a potential fatal flaw - the handling of the "T-H-E PACKAGES". Fortunately the NWMO had already

independently identified this matter as needing some redesign and apparently steps are already

underway in that re.gard.

The TRG believe that one solution that should be given serious consideration is to arrange for the

cutting or repackaging of the T-H-E tubes into lengths that can be placed inside a concrete (or steel)

canister probably similar in size to the canisters used to emplace the resin liners. A hot cell or shielded

work area will need to be installed. We recognize that this would involve considerable expense to put

in but a revised approach whereby all waste can be put into canisters that are no larger than the resin

liner containers could result in many off setting savings on top of providing a safer and more robust

emplacement scheme for T-H-E packages. If a decision is made to reduce the size of the T-H-E

packages then other large pieces such as the heat exchangers should also be reduced in size to

make them transportable by forklift either in a canister or on a pallet. This would add more uniformity

to the equipment and to the emplacement procedures. On this basis some examples of potential

savings and/or other advantages include:

• Don't need steel overpacks for T-H-E packages because several shorter pieces can be put in

concrete overpacks (will reduce cost and long term hydrogen gas production)

• Head frame and shaft length could potentially be shorter

• The repository station would not have to be so high

• The self propelled rail cart can be shorter

• The diameter of the main waste shaft could potentially be reduced

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• The track would not have to be extended beyond the end of the repository level shaft station as

forklifts could handle all waste from the station to the emplacement rooms (assumes that all

non-forkliftable LLW would also be reduced to a size that can be put on a pallet and placed via

a forklift

• The sequencing of room filling would have more flexibility i.e. don't have to put large pieces in

NW rooms first

• The use of gantry's in the rooms could potentially be eliminated

• The height of some rooms can consequently be reduced or have a higher fill factor

• There would be less steel in the repository for producing hydrogen gas

• The 14m turning radius restriction could be reduced

Alternately if this approach is absolutely not possible consider designing and fabricating prototype

versions of the related equipment so that safe handling can be demonstrated to NWMO in advance of

any public hearings.

Recommendation: Abandon the current transport and emplacement scheme for T-H-E packages in

favour of cutting the pipes into more manageable lengths and repackaging the cut pieces and/or their

contents in concrete.

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REPOSITORY VENTILATION The ventilation system currently proposed by Hatch embodies the following salient features:

• The system is a pull system; the total mine airflow is pulled down the intake shaft and up the

ventilation shaft utilizing a primary fan located on surface.

• Return air from each room is conveyed from the end of the room back to the ventilation shaft

via permanently installed steel ventilation ducting fitted with an exhaust fan.

• Airflow volume through filled rooms is to be three to four air exchanges per hour.

The TRG suggests an approach (which is shown below) as follows:

• The surface fan exhausting the total mine airflow would be eliminated. The flow from shaft

entry to exit would be powered by return air fan(s), located near the base of the ventilation

shaft. The fans would be equipped with silencers to keep ambient noise within acceptable

levels.

• Flow-through ventilation would be employed to ventilate filled rooms. Rooms would be

connected to a return air drift which would convey the total room airflow to the base of the

ventilation shaft.

Attributes of the suggested approach are:

• The surface exhaust fan is eliminated thereby eliminating surface noise, reducing collar

construction requirements and lowering capital cost.

• All room and access drift heights would be excavated with a lower back height. The overall

underground excavation volume will be significantly reduced, even considering the additional

requirement of the return air drift.

• The requirement for the placement and maintenance of permanent steel ducting is drastically

reduced, positively impacting capital cost and lowering the risk of operating disruptions due to

damage of metal ducting.

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PROPOSED FLOW THROUGH VENTILATION SYSTEM

The above changes are expected to reduce the required excavation by approximately 63,000 m3 and

the length of ventilation ducting by approximately 9,000 metres.

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Rockbolts

Wire mesh

SHAFT LINING

Concrete tlning down in 6 m pours

0.3 m slipform wall

Water stop at joints

Geotextile

In order to alleviate problems with rough wall and water control while sinking, an option for sinking with

a thin wall concrete lining is shown above. This would use a typical drop form in 6 m intervals.

The walls would be rock bolted and meshed as required to protect the workers at the bottom from

rockfalls. However, these bolts would not contribute to the long term stability of the shaft.

A geotextile membrane would be placed between the rock surface and the initial lining in order to

provide a water course into a collection ring. The geotextile will be required thru all water bearing

areas to provide a watercourse to the nearest water ring and will likely have to be continuous. There

may be a requirement for more than one water ring.

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Waters stops would be used at cold joints between pours.

Dry wall grouting can be carried out prior to slip forming the final lining.

In the better quality impermeable rock in the lower reaches of the shaft the excavated diameter could

be reduced and the lining continued downwards with the drop form without the rock support and

geotextile layer.

This system allows a smooth shaft wall to jack against as well as providing a suitable surface for

installing pipes and Mary Ann guides. It also allows drywall grouting. where required. prior to slipform

lining.

SHAFT EXCAVATION and LINING Although it may be possible to excavate a shaft using a road header this approach has not been

proven yet and would entail high expense to design and supply what would be a one-off custom

design.

We believe that the EDZ can be minimized by carefully controlled drilling and blasting.

The Reach 1 zone could also be sunk using a slurry wall from surface. This approach is well proven

and possibly less expensive than the proposed method.

We believe that the use of a steel reinforced concrete liner will compromise the effectiveness of this

liner because water will permeate the concrete leading to rusting and subsequent swelling of the

rebar.

The proposed liner has only one seal boundary i.e. at the bottom of Reach 2. It is standard practice to

have another backup seal. perhaps at the bottom of. or part way down Reach 3. There should also be

facilities provided to detect leaks (Tell-tales ) and allow grouting behind the wall by embedding grout

pipes in the liner.

We foresee difficulties aligning the stage if the primary ground control is shotcrete. We recommend

drop-forming a thin inner liner on the way down to provide a secure and smooth surface to ensure

proper alignment of the stage. The final lining can then be slip formed over top.

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UNDERGROUND EXCAVATIONS

From the information and analyses that were made available for review it appears that the Cobourg

formation is tectonically undisturbed, very uniform, its strength is high in relation to the in situ stress

field. It appears to have relatively few adverse structural features and its permeability is very low.

These characteristics make it a favourable host rock for the construction of a stable waste repository.

Further testing and analyses are required to confirm these observations but the TRG is optimistic that

these conclusions will be shown to be valid.

The proposed cross-section of underground excavations for the emplacement rooms is based on the

space required for efficient storage of the waste packages with 300 mm of sidewall clearance and an

allowance for ventilation above the stacked packages. For the typical waste packages this results in

an excavation with a span of 8.6 m and a height of 7 m. Some higher excavations are required at

certain locations to deal with larger or longer package requirements.

O.3Om

""- 150rnm ALLOWANCE T "--FOR SHOTCRETE ok

DOWELS

-- --- ,---------- ---- - -- ----- --: "'- UNITS OF PACKINC I

ENVElOPE

~ is O.3Om ~ ....::1oI=IN:.:..... ---=--+-;t ~ 11.

PACKING ENVELOPE VtlOTH

III ". ..

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A typical excavation cross-section is illustrated above showing a concrete floor, unsupported lower

sidewalls and a fibre-reinforced shotcrete layer over the upper sidewalls and drift. In addition a pattern

of rockbolts will be placed in the roof and upper sidewalls in order to stabilise the surrounding rock

mass.

The dimensions and shape of the room, depending upon final decisions on waste emplacement and

ventilation, remain to be finalised. However, the general approach to the geotechnical design of the

rooms is unlikely to change and this will be discussed below.

It is proposed that the waste storage rooms will be located at a depth of approximately 680 m below

surface in the Cobourg limestone. This is a horizontally bedded horizon of good quality rock with an

average uniaxial compressive strength of about 120 MPa. The bedding planes, with an estimated

average spacing of 0.7 m, are assumed to be relatively rough and tight. The vertical in situ stress is

assumed to be directly proportional to the overburden depth while the maximum horizontal stress is

estimated at twice the vertical stress and the minimum horizontal stress is equal to the vertical stress.

The emplacement rooms are aligned parallel to the maximum horizontal stress in order to achieve

maximum stability in the surrounding rock.

The in situ stresses and the characteristics of this rock mass have been assessed by both Itasca

(Contractor in the NWMO Geoscience program) and by Hatch Mott MacDonald (HMM) in their

preliminary design work. Numerical analyses of the emplacement room stability have also been

performed by both Itasca and HMM.

Detailed discussions were held with HMM on the preliminary designs that they have carried out to date

and, while a few detailed refinements have been proposed, the TRG is in general agreement with the

analyses performed. However, in view of the discussions elsewhere in this report on changes in the

ventilation arrangements and in the handling of large waste packages, it is likely that the emplacement

room designs would have to be re-examined and modified. If these proposed changes are accepted it

is anticipated that the room heights can be reduced and that the roof shape can be optimised in order

to reduce the potential for spalling and bedding plane separation.

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FIRE The risk of fire will always be an important preoccupation in any underground setting. The TRG did not

see any evidence (although this may have been thoroughly considered by Hatch but not presented)

that this issue had been dealt with in sufficient detail, especially since the design group are hoping to

finalise the underground layout and the associated ventilation scheme as soon as possible. In our

opinion, these matters cannot be frozen until after there has been a complete simulation of all the

potential fire types and locations and only if these simulations show that the latest underground layout

and the ventilation schemes together are capable of satisfactorily protecting the life of all underground

workers. The designs should also include the appropriate fire detection systems, fire suppression

systems as well as the rescue stations (fixed and or mobile), fire doors etc. Potential fire locations

could include the shaft collar areas, the shafts, the repository level station, the services area

(especially the repair shop, the warehouse and the fuel storage site), the access drifts and in the dead

end emplacement rooms (during excavation and during filling). The simulations also need to consider

the possible location of any workers near a fire location. For example a worker could be either in front

of or behind a burning rubber tired truck or loader in a dead end emplacement room.

Recommendation: Prepare a simulation of possible fire events showing that the DGR is designed for

to cope with such events.

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MAIN CAGE and HOIST

Although the present design recommends a 6.0m diameter hoist the original six rope, 4.27m diameter

Koepe hoist would be adequate for handling the loads required. The options to increase the diameter

to 6.0m and the rope size from 42mm to 56mm are unnecessary.

Most Koepe hoists in North America now use low rotation, stranded headropes such as the Notorplast

design produced by Trefileurope. Low rotation is necessary to avoid scrubbing of the rope tread liners

through torque build up in the ropes.

The balance ropes must also be of a flexible design to avoid kinking at the tail-loop.

The main cage height could be drastically reduced if the T-H-E packages are kept below 4.6m in

height.

The main cage should be equipped with safety dogs. This will ensure that the cage cannot fall down

the shaft should the ropes fail ( this incident occurred at a potash mine in western Canada when a fire

annealed the headropes ). Safety dogs are required in California on all conveyances, even those

suspended by mult-ropes. Safety dogs designed to operate on HSS guides are in operation in many

installations in the USA.

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MAIN CAGE ROPE CHANGING

The present design has not considered the facilities that are required for rope changing. It is ,

however, necessary to replace the head ropes and balance ropes on the main cage hoist on a regular

basis. We expect that the frequency will be between 3 and 5 years for the duty required of the main

service hoist.

The safest method utilizes a multi-capstan winch system in conjunction with a specialized rope

handling device located in the headframe.

This system, as illustrated below, was developed by Siemag to permit all headropes or all balance

ropes to be changed at the same time without requiring personnel to work in the shaft.

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MAIN SHAFT AUXILIARY CAGE HOIST

The present design proposes using a single drum hoist to operate the auxiliary cage. This approach

will require the use of wooden guides and a cage equipped with dogs. These lead to problems in

maintenance and present a fire hazard.

The installation of a two rope Koepe with cage and counterweight will allow the use of steel guides

and avoid the necessity of dogs. This Koepe would be installed in the headframe at the same level as

the main hoist.

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VENTILATION SHAFT HOIST

The ventilation shaft will be the only means of developing the underground for about 8 months. As a

result the time available for hauling muck is only about 12 hours per day ( 50% per shift ). We estimate

that development will produce about 2 million tonnes of waste rock. This could be removed in 2 years

( say 700 days ). The daily rate is therefore about 3000 tonnes. The hoist will need to be equipped

with 8 tonne capacity skips in order to produce at this rate using 12 hours for production.

VENTILATION SHAFT LOADING STATION

The possible use of road headers to carry out the development means that the waste rock could be

small in size, wet and sticky. To avoid the muck hanging up in the waste pass it should be installed

vertically, directly below the grizzly. The pass will terminate over a pan feeder installed in a station

below the DGR level. This feeder will then discharge into measuring flasks at the shaft wall.

Grizzly

I I '\.. /

Pan Feeder

Measuring FLask

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ROAD HEADERS

Road headers have been proposed for application to both sinking the shaft ( Reach 3 ) and developing

the repository.

Application to Shaft Work The consensus among the review group is that this is not a viable option and is made even less

attractive as it is can only be used in Reach 3.

The machine would be a one-off design and would be a different design for each shaft if they remain

at the present dimensions of 4.Sm and 6.Sm diameter.

We believe that there is insufficient room to work with this machine in a shaft as small as 4.Sm

because of the space required on the shaft bottom for men and buckets. The presence of the boom

will also make probe hole drilling and cover grouting a major problem.

We also believe that it will be difficult to install ground support close to the bottom and also forsee a

major problem in supporting this machine. These devices require two sets of three large hydraulic feet

to support the structure and resist the massive torques produced by the cutting heads. These feet will

likely damage the ground support as the machine walks down the shaft.

In addition to the difficulties stated above the delivery of a machine will be about 2 years and high

cost.

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Application to Development The consensus on the use of road headers for lateral development is somewhat mixed as no one in

the TRG has personal experience with successful application of this machine in limestone for

development. Some members have, however, experienced poor performance of these machines in

what was thought to be reasonable conditions for their application.

We have contacted other personnel who have worked in limestone mines and have found the

productivity of road headers to be far below that of conventional drill and blast mining. The people we

have contacted also anticipate poor performance of these machines in rock that is not jointed and

layered. The Cobourg formation is free of both features and may therefore be difficult to break. A

summary of our correspondence with these users is provided in the Appendix.

The roader header option, if selected, means a large financial commitment to something which might

fail ( and failure is not an option ).

If road headers are used they will create a huge amount of dust. To eliminate the dust as much as

possible a large amount of water will have to be used to try to suppress the dust. The water will create

a wet sticky muck. The drill and blast approach, on other hand, eliminates both dust and wet sticky

muck as well as a pan feeder at the loading station. It will be possible to utilize a standard loading

arrangement with a conventional raise to a pair of lip pockets.

Unless there is a successful and representative test in a surface or near surface outcrop of the

Cobourg formation, the TRG is unanimous in its opinion that drill and blast techniques should be

selected for the lateral development ( as well as for the shaft sinking ).

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INTEGRATING A SINKING CONTRACTOR INTO THE DESIGN TEAM

The TRG concur 100% that integrating contractor experience into the design team early will be a real

plus for the project. However we are concerned that choosing one contractor from amongst 3 or 5

potential bidders to be a part of the design team (even if this contractor is subsequently dissociated

from the project a year or more before the bidding starts) has a high probability of discouraging one or

more of the other (not chosen) contractors to withdraw from the bidding process. This could have a

serious cost implication and in a worst case scenario leave the NWMO with only one bidder. A number

of the TRG members have previously worked as contractors and we have all at one time or another

declined to present a bid when we felt that another contractor had an inside track. This would certainly

be the assumption in case NWMO proceed as currently contemplated.

As an alternative we suggest that there are at several companies that could provide input to the

design team similar to that which would otherwise be provided by a contractor without offending any of

the potential bidders. We would further recommend that the firm so selected by the NWMO be

mandated to consult regularly (and confidentially) with those contractors that have (or are expected to

be) pre-selected by NWMO to bid the shaft work.

Recommendation: Give consideration to integrating an engineering firm qualified in the area of shaft

sinking and shaft design into the design team.

Alternately the NWMO could build up the Owner's team by hiring one or more individuals with the

requisite shaft design/sinking experience.

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VARIOUS

1. VENT DUCT: In the event that the disposal room ventilation scheme is maintained as

presented then two things might be considered: a) rolling the vent tubing underground and b)

installing the vent duct in such a way that it could be retrieved just prior to closing a room; this

would help reduce total vent duct cost AND would reduce the amount of steel in the rooms

susceptible to corrosion and the production of hydrogen gas

2. EMPLACEMENT ROOM HEIGHT: With detailed planning it should be possible to determine

the ultimate contents (which type of waste package) in most of the rooms. Hence it should be

possible to adjust the excavated back height of the rooms to height of the packages and of the

emplacement equipment (probably forklifts only if the TRG recommendations are adopted).

This should result in a significant reduction in room excavation costs.

3. DISPOSAL ROOM CONCRETE FLOORS: The TRG is concerned, but nevertheless believes,

that with lots of care and effort the quality of floor needed to successfully stack up to 6 or 7

waste packages can be constructed. However it needs to be noted that in the event that a drill

and blast method is adopted for the disposal room excavation it will be significantly more

difficult to construct a floor with the required tolerances. In fact with either excavation method a

small amount of non-uniform floor heave is to be expected and this will require excavation and

stabilisation before the concrete floor is cast. Stabilisation of the excavated floor can be

achieved by placing short grouted dowels which can also be used to anchor the concrete slab.

4. AUTOMATION AND ROBOTICS: Any operation that is under full manual control is more prone

to error (human) than a partially or fully automated process with multiple sensors, built in

redundancy and a failsafe design. A more automated process would probably increase the

public's confidence during hearings and give evidence of a more robust design. The design

team should consider looking for opportunities where some automation is practical.

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5. GROUTING AND PILOT HOLES: There are concerns that grout may travel between shafts

and that the shaft pilot holes will cause problems for sinking unless they are sequentially

grouted during the sinking program. If pilot holes are drilled in the shaft they will have to be

properly grouted to insure they do not provide a high inflow water course into the shaft while

sinking. These holes will have to be stage grouted as water is intersected when the holes are

drilled.

A second issue arises if one shaft advances ahead of the other; this will likely be the case.

When grouting the main shaft the grout may want to travel to the line of least resistance which

will likely be towards the vent shaft.

We highly recommend a grouting consultant be approached, such as Mr. Doug Morrison, who

is with Golder Associates Ltd.

6. VENTILATION SHAFT DIAMETER: The ventilation shaft diameter will need to be increased if

development ventilation is needed prior to the main shaft arriving at the level.

7. GROUTING: The grouting pattern will need to be reviewed (possibility of needing 3 drilling

Jumbos) and a surface grouting plant will be needed to feed them.

8. MINE RESCUE: A mine rescue team will be required with back-up from Goderich.

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APPENDIX - COMMENTS ON ROADHEADER EXCAVATION

Introduction

It has been proposed that the low- and mid-level waste repository rooms of the DGR should be

excavated by means of roadheaders. The Technical Review Group (TRG) unanimously recommends

against this option and favours the use of conventional drill and blast methods. The reasons for these

recommendations are discussed below.

Roadheader Experience

Roadheaders have been used on a number of civil engineering projects with varying success.

Important factors that have to be taken into account in deciding upon the suitability of roadheaders

are:

• Intact rock mass properties - roadheaders appear to have been most successful in rock with a

uniaxial compressive strength in the range of 50 to 80 MPa. In rocks of this strength, a uniform

rock mass with few significant structural features helps in the creation of stable openings and

road headers have been very successful in materials such as salt and potash.

• Claims that machines will cut massive rock with intact strengths of up to 120 MPa have to be

questioned since joints, bedding planes and other structural features will reduce the rock mass

strength significantly and it is this strength reduction that is exploited by the cutters. Cutting of

high strength rock with very few structural features, such as the Cobourg limestone, may be

possible but will result in high bit wear, the generation of fines rather than chips and in high

loading on the machine components.

• Dust generated during cutting is a health hazard and has to be dealt with by the provision of

adequate ventilation for each road header as illustrated in Figure 1.

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Figure 1: Roadheader excavation of tunnels for the CERN project in Switzerland. The rock is a soft molasse -a combination of sedimentary and tertiary materials including sandstones, laminated marls, clays, gravels and sand. Uniaxial compressive strength of the intact materials range from 2 to 50 MPa. Layer thickness varies from a few centimetres to several metres and the molasse is prone to swelling and slaking when exposed to air and water. Note the ventilation arrangement for dealing with dust generated during cutting.

• Attempts to use water sprays to suppress dust leads to problems in handing the muck. The

following comments have been extracted from a report (sent to Evert Hoek) on the Subansiri

Lower Hydroelectic project in India where 4 roadheaders are being used to excavate a number

of 9.5 m diameter tunnels in relative weak rock masses: "The water sprinkling efforts on the

cutter face results in slush formation since the excavated rock is in the form of a fine powder.

This has resulted into non-workability of the conveyor system available for mucking. Therefore

the mucking operations are not concurrent with the rock cutting. The road header is shifted back

and then mucking operations are carried out in the conventional system of using load/haul

equipment resulting in additional cycle time for mucking".

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The following comments were offered, in an email to Peter Tiley dated 5 October 2009, by Mike

Marksberry, Director of Mine Engineering, Compass Minerals, 9900 West 109th Street, Suite 600,

Overland Park, KS 66210:

"I don't have direct experience with road headers in Limestone, but before I joined Lafarge the

technical people up in Montreal did a fair bit of work on using roadheaders in the mine instead of

drill/blast. They worked with the Colorado School of Mines and Voest-Alpine. At that time they

concluded that continuous mining wouldn't produce the same TPH as economically as drill/blast in

our limestone. The machines can definitely work in limestone, but they just felt in our particular

situation for production mining it would not be as cost effective. After I got on board and was

responsible for ordering the equipment I was not a real fan of "experimenting" with Lafarge's first

underground effort. We had a lot riding on it and I knew the "old-fashioned" way would work.

Not all limestone is the same, and there are big differences in compressive strength, chert content,

and rock mass. Rock mass is a big variable, and bedding, jointing, etc. has a lot to do with how it

will break and is probably more critical than compressive strength alone.

Lafarge bought an aggregate company up in Chicago several years ago and they used a

road header to develop a slope to a limestone formation, and then mined limestone with it for a

while to open up the area before production drill/blast began. From what I know it was quite

successful. The main guy behind it was a friend of mine and he now works for us. I will contact him

to find out more.

In short, it can definitely work, and I imagine there are a lot of civil jobs in similar materials where

they were successful. It depends on the unique geology and production rates trying to be obtained.

I'll get back to you if I learn more from my buddy.

Mike"

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In a follow-up email, dated 6 October 2009, Mike added the following comments:

"Massive limestone would be more difficult. You would have to cut it all without getting any

breaking from bedding or jointing. It would be slow, dusty, and consume a lot of bits. It can be

done though.

I talked more to my friend who used one in Chicago. He indicated that it worked OK, but they

switched over to drill and blast as soon as they could as the productivity was just too slow and the

product coming out of it didn't make a good aggregate.

He said the machine that he used, which is a Voest Alpine AM 105, was bought by another guy in

the Chicago area (Joliette) and he apparently is mining with it. From what my friend says this guy

likes to talk about it and is a real proponent of it , so you should give him a call.

You might even be able to go see it. The company is Mining International and the guys name is

Gary Smyth. The last number he had for him is 815-274-0303.

Mike"

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Conclusions

Based on their personal experience and on comments such as those quoted above, the TRG has

concluded that the suitability of roadheaders for the excavation of the waste repository rooms has not

been demonstrated in similar rock formations.

From the information presented to us for review it appears that the Cobourg limestone is a relatively

massive rock with few structural discontinuities. The average uniaxial compressive strength of the

intact limestone of 114 MPa within a range of strengths from 55 to 175 MPa (based on information

provided to the TRG during a briefing on the Geoscience Program) is at the upper end of the range of

rocks considered to be suitable for roadheader excavation. The scarcity of discontinuities to weaken

the rock mass suggests that the roadheader operation would be slow and costly in terms of bit, bit

holder and other equipment replacement.

The scarcity of discontinuities also means that the excavation process would be dominated by cutting

rather than chipping and that the resulting waste would be in the form of dust and fines. It is unlikely

that much of this material could be marketed as aggregate.

Dust generation during excavation is a health hazard which would have to be dealt with by ventilation

or by water sprays. High volume ventilation has to be provided for each roadheader and has to be

engineered to move with the roadheader as illustrated in Figure 1. Water sprays will result in the

formation of mud which, as described earlier, can have a negative impact on muck removal.

In view of the uncertainty associated with the operation of road headers in the Cobourg formation and

the practical difficulty of carrying realistic in situ trials before the decision on excavation method has to

be made, the TRG cannot support the proposal to use road headers for any of the excavations in the

DGR.

The TRG recommends that conventional drill and blast methods should be used for excavation of the

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DRG and that controlled basting methods should be used to minimise damage to the excavation

perimeters. The result that can routinely be achieved by these methods is illustrated in Figure 2 and

experience is available in Canada on the use of controlled blasting to minimise excavation damage.

Figure 2: Results achieved using well designed and carefully controlled blasting in a 7.2 m

diameter tunnel in jointed gneiss in the Victoria hydroelectric project in Sri Lanka. Note that

no support was required in this tunnel as a result of the minimal damage inflicted on the

rock. Drilling was carried out using Atlas Copco hydraulic jumbos and the blasting design

was provided by Atlas Copco. A cast in place concrete lining was placed after the

excavation of the entire tunnel had been completed. Photograph by Evert Hoek in 1981,

reproduced with permission from the British Overseas Development Administration and

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from Balfour Beatty-Nuttall. Reference

http://www.rocscience.com/hoeklpdf/17 Blasting damage in rock. pdf.

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Documents

TRG Review of Preliminary Engineering Phase I DEEP