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Dear Richard,

We very much appreciate the opportunity to respond to the questions generated by thepanel review and to clarify issues related to the Kimballton DUSEL proposal. Below wehave provided summary statements and detailed responses to the questions received.However, if we have misinterpreted the questions, or if our responses do not provide therequired detail, we would be happy to provide additional information.

1. Have you considered that the rock may be gas (methane) bearing? Is this aproblem for performing the tunnel excavation? For operations?

We have considered the possibility that the rocks might be gas bearing and haveevaluated whether this would be a problem during construction and operation.The likelihood of intersecting gas-bearing structures is minimal, and a strategyis being developed to minimize problems associated with gas.

First, we wish to emphasize that co-PI Bob Hatcher and Kimballton ScienceTeam member Bill Henika have extensive (combined 80+ years) experience inAppalachian Thrust Belt geology and oil and gas exploration. They have mappedthe area extensively during their careers, have led exploration and drillingoperations to search for hydrocarbons, and are universally considered to beleading experts in the geology and hydrocarbon distribution in the Appalachians.These experts conclude, based on the well-known geology at Kimballton, thatrocks to be encountered during excavation and construction of DUSEL areunlikely to contain hydrocarbons that would negatively impact construction andoperation of DUSEL.

The stratigraphic section that will be encountered during construction contains nocoal seams. Regional coalfields are in younger Carboniferous strata that overlythe local geology and have been eroded away. The rocks have experiencedtemperatures sufficient to destroy (over-cook) any oil that might have beenpresent. Of the formations to be encountered at depth, only the Martinsburg hasany source rock potential, and this unit will largely be avoided duringexcavations. Local and regional exploration (including many wells drilled duringexploration) indicates that the Martinsburg Formation is not an important gassource. The nearest petroleum deposits are greater than 200 km to the southwestin rocks similar to those locally, but which did not experience the higher pressuresand temperatures associated with folding and thrusting in the Kimballton area (seemap of “Mineral Industries and Resources of Virginia”, Palmer C. Sweet,published by the Commonwealth of Virginia, Division of Mineral Resources,1983).

If trace quantities of gas were generated in the local rocks, the structure at ButtMountain is not of the type that is typically associated with accumulations ofhydrocarbons. Butt Mountain is a syncline (see Figure 1), and the dips of the rockunits allow hydrocarbons to migrate to the surface. No petroleum occurrences

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have been identified in the fold and thrust belt in synclinal structures similar tothose at Butt Mountain. If the rocks that comprise the Kimballton stratigraphy didproduce hydrocarbons during burial, we might expect to find hydrocarbonaccumulations in the adjacent Bane Dome (Fig. 2), which contains similar rocksbut which has an anticlinal form that is more conducive to trapping hydrocarbons(e.g., the large gas deposits of Wyoming are contained in similar anticlinalstructures). However, no hydrocarbons have been found in this area.

Figure 1. Cross section through the Butt Mountain syncline and the adjacentBane Dome anticline.

The deepest parts of the existing Kimballton mine are currently at 2300 feet andno gas hazards have been encountered during the 40+ years of mining these samerocks. Mr. Ray Roeder, Mine Manager at the Kimballton Mine, has repeatedlymonitored locations underground and at the portal (conveyor belt) where allthe exhaust air comes out of the mine, and no methane has been detected.

While the abundant data from earlier exploration drilling in the vicinity of theKimballton DUSEL argue strongly against encountering methane duringconstruction (and operation of the laboratory) the deep drill hole that will becompleted during the S2 process will monitor for the presence of hydrocarbons asdrilling proceeds. Additionally, core samples from the hole will be analyzed fortotal organic carbon (TOC) and other hydrocarbon chemical signatures.

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Figure 2. Geologic map showing the relative locations of Butt Mountain, theBane Dome, Kimballton Mine site and Blacksburg.

Finally, if methane is unexpectedly encountered during construction, the rock canbe degassed completely by drilling ahead of tunneling and hydrofracturing therock. This process would also provide an opportunity to conduct fundamentalresearch related to fracturing during tunneling. Tunnel construction would providethe opportunity to “mine by” the fractured rock to study characteristics of thefracture network produced by hydrofracturing. Note that predrilling andfracturing is not practical if TBMs are used to excavate the tunnel – the tunnelingtechnique that will be employed to excavate tunnels at Kimballton DUSEL will bedetermined as part of the S2 process. If it is determined that TBM excavation isappropriate, gas problems are handled using properly shielded equipment, gasmeasurements and ventilation.

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2. Will the one borehole tell you what you need to characterize the geology andthe geomicrobiology? With what uncertainty?

The geology at Kimballton is already known with a high degree of certainty.The single borehole will confirm the sub-surface geology and provide a uniqueopportunity for geomicrobiology research.

Geology:The Appalachian fold and thrust belt has been studied for hundreds of years and,while the rocks are folded and thrusted, the geology is very predictable andsystematic. Individual rock units can be traced over hundreds of miles, and theexpected subsurface stratigraphy has been confirmed by thousands of drilling andmining operations conducted to explore for and extract mineral and energyresources. Thus, it is important to emphasize that the stratigraphy and structure atthe Kimballton site are already known with a high degree of confidence. Sourcesfor this knowledge include:

• Outcrops around the margins of the syncline• A deep well and seismic imaging in the nearby Bane Dome• Seismic imaging of Butt Mountain• Published U. S. Geological Survey maps and reports• Structurally balanced cross-sections• Seventy km of drifts in the Kimballton Mine

In the 1980s a seismic survey was conducted across the Bane Dome, an anticlinalstructure adjacent to the Butt Mountain syncline (Figure 2). Based on that survey,the subsurface geology at the Bane Dome was predicted. Later drilling in the areato depths of several thousand feet confirmed the subsurface geology predictedfrom the earlier seismic survey.

In the summer of 2004, the Kimballton team conducted a seismic survey acrossthe top of Butt Mountain. Based on results of that survey, the subsurface geologyat Butt Mountain was confirmed. The interpretation is consistent with knownoutcrops and underground excavations, and showed no “surprises” in thestratigraphic column.

The planned deep borehole will serve to confirm the structure and rock unitthicknesses. Various downhole logging techniques will also be applied, includingdip-meter analysis, optical televiewer for fracture imaging, borehole breakout-based stress analysis and down-hole geophysics to better characterize the geologyand engineering properties of the rocks. Finally, while we describe the boreholeas a single, deep hole, in fact it will function as several holes. Side-track drillingtechnology will be used in the bottom several hundred feet of the hole, withseveral angle-holes drilled away from the main hole to produce a cone-shapedregion from which we will gather geologic information. Thus, at the level of the

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deep campus we will develop a 3-dimensional image of the geology from thesingle deep drillhole.

The planned deep borehole is only one of the strategies to reduce uncertainty withregard to geologic characteristics. Additional strategies described in the S2proposal include:• Several intermediate depth boreholes in the vicinity of the proposed portal• Additional fracture studies within the Kimballton Mine• In situ stress measurements• Electrical resistivity studies in the portal areas

Geomicrobiology:A single borehole drilled and cored in a collaborative manner with thebiogeoscientists (tracers, good coring regimens, rigorous sample handing andQA/QC for sample integrity assessment as per the extensive experience andrecognition of program participants) will give us crucial information as to thelithology, interfaces, structure, integrity of formations, groundwater chemistries ofthe formations encountered, and constraints on the environments encountered, andprovide far more high quality samples from the deep subsurface than have everbeen recovered previously. Additionally, the salinity, groundwater chemistries,gasses present and stable isotope profiles will be crucial in describing thethermogenic/diagenic and biogenic processes in these deep hydrologically andgeologically isolated environments, and will prove useful in delineating the lengthof time of isolation from surficial processes.

Any and all deep subsurface organisms or communities encountered fromsediments (rocks) that pass the rigorous QA/QC will substantially increase ourunderstanding of deep subsurface environments. Yes, there will be uncertainty asto the extent and dominance of any observed communities but the insights gainedwill be sufficient to design an in-depth, long-term program. Or alternatively,results may suggest the local environments may be less than appropriate (as wasthe case in 2 tightly sealed and recently heated subsurface environmentsinvestigated in the western US in the 1990's). In either case, this information iscritical to developing a long-term science plan and evaluating the range ofexperiments that might be possible.

To adequately assess the subsurface and the potential of its resident biologicalpopulations will eventually require multiple boreholes with more refinedhypotheses. But, when done properly, the first hole is the best single return oninvestment in defining the environmental constraints, publishing the first glimpsesof that extreme environment, the first molecular sequences, the firstunderstanding, and the first microorganisms. Future endeavors will refine thehypotheses, relate to surface events, highlight relationships between formationsand ecology/adaptation, and examine deep, dark life in the terrestrial subsurfaceand limits of life.

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It may be worth noting that no such endeavor has been undertaken at great depthssince the US DOE corings in the early 1990's. Molecular screening ofenvironmental DNA/RNA sequences (with or without PCR) were not developedin that era. That single borehole resulted in dozens of peer reviewed publicationsincluding "Science"; greatly enlarged our understanding of deep subsurfacebioprocessing; two unusual species of microorganisms were described, novelprocess observed; and two or more patents were derived from those processes.Importantly, in the 1992 Taylorsville endeavor less than one kg of deep materialswere recovered and less than 50g passed the QA/QC and were deemedrepresentative of the subsurface. In the proposed corehole we will recover farmore than 100-X more high quality materials distributed between severalformation and repeating units of those formations for an unprecedented look intothe Earth's deep subsurface.

3. Who will be the project manager for the next 6 months? Who is going to dothis work, given that the PI is the senior academic officer of the university,and the two physicists are very involved in other things?

A highly-qualified, fulltime project manager has been hired for KimballtonDUSEL. The position of the PI in the University administration guaranteesthat Kimballton DUSEL will have the resources necessary to be successful.One of the strongest assets of the Kimballton leadership team is its breadth,including physicists, geoscientists, engineers and biologists, all of whom arefully engaged in the process.

The Kimballton S2 proposal listed Dr. John Wilson, Assistant Vice President forAdministration in the Research Division at Virginia Tech as the interim projectmanager. At that time, the Kimballton team was actively searching for a highlyqualified individual who could serve as a full-time project manager forKimballton DUSEL. Since the S2 proposal submission, Dr. Mark Pierson hasbeen hired as a full-time project manager to work exclusively for the KimballtonDUSEL team. He will assume these duties beginning June 1, 2005. Dr. Piersonhas 22 years of experience in the Navy, attaining the rank of Commander beforereturning to academia and earning his PhD in Mathematics. During that time, heserved as second-in-command on nuclear submarines, as an action officer at thePentagon, and as a deputy department head at the Office of Naval Research. As anaction officer at the Pentagon, he prepared and justified cost estimates and long-term budgets for all submarine maintenance for the entire Navy – a $2 billionbudget – and developed cost savings of $300 million from the program. At ONR,he was Program Manager for the $30 million Strategic Ballistic MissileSubmarine Security program. His experience managing large projects, coupledwith his military, nuclear, business and math background, makes him an idealchoice to serve as project manager for Kimballton DUSEL. Dr. Pierson’s CV isattached to this response.

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Who is going to do this work, given that the PI is the senior academic officer ofthe University and the two physicists are very involved in other things?

While the U.S. scientific community provides the technical expertise and drivebehind the DUSEL effort, an initiative of this magnitude cannot succeed withoutconsiderable support and encouragement form the senior administration ofuniversities, national laboratories and Federal agencies. Having this group asactive participants in the DUSEL effort facilitates and expedites many of thedecisions that must be made to move the project forward.

The VT component of our team includes not just physicists, but rather spansmultiple departments and colleges, and also includes expertise in financial, legal,community relations and political support. In his role as PI, Provost McNameereaffirms the University’s current and ongoing commitment of its resources toDUSEL. He can, and does, speak for the University in a manner that facultysimply cannot and has the authority to make decisions regarding allocation ofresources, including personnel, quickly and in the best interests of the DUSELeffort.

Completing the S2 process requires harnessing and integrating the expertise andwork of individuals in many disciplines. The unique geologic features of theKimballton site have greatly facilitated this, with the individuals tasked in ourproposal eager to start, driven by their own research interests and curiosity. Manyfaculty have already received teaching relief and have committed major fractionsof their time to accomplish the S2 program.

Most of the senior collaborators listed in our proposal are not just interested in aDUSEL, but rather, specifically in DUSEL at Kimballton (see their letters ofsupport). This broader team has worked very well together for over a year indeveloping this project, and is committed to seeing the S2 goals accomplished.(See individual roles listed within the proposal.) If Kimballton is selected as an S2site, we anticipate many other DUSEL advocates will bring their expertise,leadership and interests to the Kimballton project, making the combined teameven stronger.

Local coordination of the S2 related activities is under the direction of thefollowing members of our executive committee:

Bodnar (University Distinguished Professor of Geosciences – full time)Mauldon (Associate Professor of Engineering – half-time with teaching buy-out)Vogelaar (Associate Professor of Physics – half-time with full teaching buy-out)Westman (Associate Professor of Engineering – half-time with teaching buy-out)

The day-to-day coordination and project management will be led by ProjectManager Mark Pierson. Several subtasks in S2 will be sub-contracted tocompetent firms to take advantage of their capacity or expertise in these areas.

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We note that ALL of the PIs associated with Kimballton DUSEL are active,successful, leading researchers in their respective fields, with large ongoingresearch programs. We consider this to be a distinct advantage, and guaranteesthat our S2 process will meet the goals set forward in the S1 report, where wehave also been engaged.

DUSEL is a multi-disciplinary project, and we note that most tasks to becompleted in S2 are related to constructability and are not physics driven. WhileVogelaar and Raghavan are co-PIs on this proposal, they are certainly not the onlyphysicists on the Kimballton team (see list of senior collaborators).

Vogelaar is involved with the underground Borexino solar-neutrino detector atGran Sasso, was an active participant in the recent APS neutrino study, is theworking-group coordinator for solar and low-energy neutrinos in the S1 process,and was recently appointed to the NuSAG sub-panel of the NSAC and HEPAPadvisory boards. These activities enhance the credibility of his role in DUSELwhere many future neutrino experiments are expected to be hosted. Raghavan isvery well known in the underground neutrino physics community and is workingon developing the LENS and HSD detectors, as well as continuing work with theBorexino experiment. Again, these activities are directly related to the futurescience program of DUSEL. Together, Vogelaar and Raghavan provide localexpertise and contact for the broader physics community interested in physics atDUSEL. Since neither will be teaching this fall, they will devote significant timeto DUSEL. The other VT physics team members, including Pitt, Takeuchi, andChang, along with other members of the Kimballton team, enable us to addressand interact with the full range of physics research planned for DUSEL.

4. Does the bond apply just to the Kimballton DUSEL, or are there otherprojects to which it would apply? If the latter, how much would apply to K-DUSEL?

The only initiative that will be supported using the $150M from the bondrequested by Governor Mark Warner and approved by the Virginia GeneralAssembly is Kimballton DUSEL.

From the very earliest involvement of Kimballton in the DUSEL initiative,Virginia Tech President Charles Steger has kept Governor Mark Warner informedof the progress of our effort. Governor Warner has been a strong supporter of thiseffort from the beginning. In the Fall, 2004, a member of Governor Warner’s staffcontacted Virginia Tech to request language to be included in the Governor’sbudget to establish bonding authority in support of the Kimballton DUSELproject. The Governor included a request for a $150M bonding authority in hisbudget and is included in the final budget approved by the General Assembly. Thecomplete language of the budget entry follows:

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In the event the Commonwealth of Virginia is selected as the site for theNational Science Foundation project known as the Deep UndergroundScience and Engineering Laboratory (DUSEL), the Commonwealth shallundertake all practicable efforts to facilitate the location and construction ofsuch facility. Contingent upon commitments from the National ScienceFoundation authorized by the United States Congress and subject to theapproval of the Virginia General Assembly, the Commonwealth shall issuebonds, through an existing economic development authority or authorityestablished for such purpose, for construction and infrastructure of saidproject in an amount not to exceed $150 million. Such bonds shall be retiredin an agreed upon period time not to exceed ten years through federal fundsappropriated for the DUSEL project. Funds made available through thismechanism shall be intended for infrastructure, including access roads,tunneling, construction of laboratory facilities, and other such purposes asmay be agreed upon between the National Science Foundation and theCommonwealth.

5. Why the expert on conflict resolution? Are you anticipating problems thatshould be addressed? Do they already exist?

We have actively engaged the local communities and have not identified anyopposition to the Kimballton DUSEL project, and we do not anticipate anyproblems.

To the contrary, there is remarkable local community and stakeholder support forKimballton DUSEL. Continued and enhanced community involvement in allphases of Kimballton DUSEL will be critical to building the ongoing trustrequired not only during construction, but to eventually allow implementation ofthe full range of experiments envisioned for DUSEL. To guide us in this process,we have invited Dr. Jim Phillips, Director of the Center for Conflict Resolution atVirginia Commonwealth University, to join the Kimballton team. He will beworking to ensure the best possible political environment for the project.

The strategy of the Public Relations/Participation component of KimballtonDUSEL is to avoid possible future opposition to the project by engaging thepublic in a series of interactive processes to build partnerships, therebyconstructing broader consensus by all stakeholders. The cornerstone of thisstrategy is to educate the public about the project and to respond to questions andconcerns in a timely fashion, and preserve and strengthen current communityrelationships.

Dr. Phillips has successfully managed this type of strategy over his career. Forexample, in 2000 he was a member of the facilitation team under contract with theUnited States Department of Defense to educate stakeholders living aroundmilitary bases targeted for closure. This process was successful and avoided

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organized opposition to those targeted closings. He found that by providingstakeholders a forum to have their questions answered and to receive information,he was able to build stronger consensus for the community. This resulted in aninformed and educated community and avoided opposition resulting from lack ofunderstanding of the process and its implications. A similar strategy will beemployed at Kimballton DUSEL.

6. Do you have any experience on rock bursts in this type of rock at extremedepths? Have you considered this potential problem?

The Kimballton Science team includes several researchers with considerableexperience in rock bursts, and we have considered the possibility of rock burstsoccurring during construction. Technology exists to manage rock bursts,should they be encountered during construction.

Rock bursts can be a serious problem, typically occurring in strong, stiff (highmodulus) rocks under high stress. Experience with rock bursts in rock similar tothose at Kimballton is limited, however the physical properties of the carbonaterocks (e.g. strength) are similar to those at other existing deep mines (e.g.Creighton, Homestake). These physical properties are described in greater detailin Appendix C of our proposal, and included below. While the rockburst hazardis undefined at Kimballton, no problems are apparent in current high extractionmining to 750 m. Large underground caverns excavated 40 years ago remainstable and safe to work in to this day with little or no rock bolting.

The Kimballton-DUSEL team has significant experience with rock bursts andother aspects of underground construction. PI Herbert Einstein (St GotthardTunnel) and team members Nick Barton (Norwegian and Himalayan tunnels) andDerek Martin (URL-Canada) are well-known experts in construction in highly-stressed ground. Erik Westman, a member of the Mining and MineralsEngineering Department at Virginia Tech and the K-DUSEL executive council,has an NSF CAREER grant to develop the use of seismic tomography to imagestress-related density changes in advance of mining, with the goal of predictingrockbursts. A currently-funded NSF-ITR project (AMADEUS) includes membersof the K-DUSEL team and supports the use of image analysis, fracture modeling,numerical modeling, tomographic imaging, and virtual reality to allow a tunnelengineer to virtually walk ahead of the tunnel face to evaluate ground conditions,including burst potential. Marte Gutierrez of the Civil andEnvironmental Engineering Department at Virginia Tech is the PI for theAMADEUS project. He has wide experience in modeling of failure andinstabilities in rocks and modeling of tunneling in rock.

The Kimballton DUSEL site is hosted by rocks with strength similar to that of theother DUSEL candidate sites and existing deep mines. While rock bursts are aserious issue, our team has sufficient practical experience and expertise in the areaand can employ existing methods (e.g. hydro-fracturing ahead of excavation) to

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mitigate any rock burst hazards that might be encountered during construction.The fact that this construction is feasible has been clearly demonstrated during thedesign and construction of the Sudbury Neutrino Observatory at 2200 m depth inCanada. While the Creighton mine is burst-prone, the cavern was constructedwithout incident (Castro et al., 1996).

There are several uncertainties to the prediction of rockbursting potential due tothe large sizes of caverns to be excavated. In common with other candidate sites,other potential sources of rockbursting are fault activation and movements alonglarge fractures close to the excavation (although attempts will be made to avoidintersecting major faults). Local seismicity from seismically active regional faultscan be a source of rockbursting only if earthquakes occur during tunnel/cavernconstruction (very unlikely considering earthquake recurrence in CEUS). Postconstruction, excavations will be permanently stabilized and will not bepotentially rockburst prone during earthquakes (earthquake loads can be includedin the design of tunnel/cavern final support). So the main possible source ofrockbursting is from failure of intact rock along unsupported excavation surfaces(i.e., spalling, buckling, strain burst, shear rupture), as discussed above.

Concern for rockbursting in civil structures is different from that encountered inmining. Unlike mining environments, the completed tunnels/caverns in a civilstructure such as DUSEL will have permanent supports, and in general shorterspans. Mining techniques (e.g. using pillars) are particularly rockburst prone, butthese will not be used in tunnel/cavern construction for DUSEL. Long-term, therewill be much less excavation-induced seismic risk (compared to mines) associatedwith DUSEL tunnel/caverns because permanent support systems will be usedduring construction.

Major issues for rockburst potential in civil engineering excavations are workersafety during construction and tunnel/cavern stability during construction. Workersafety can be ensured by more accurate predictions of rockburst potential andcontinuous seismic monitoring during construction. Tunnels/caverns can besecured against rockbursting by excavating pilot tunnels and using pre-reinforcement prior to tunnel enlargement (either by drilling or controlledrockbursting). Support systems with yielding components can also be designedand used to absorb and dissipate some of the rockburst energy.

The following references coauthored by members of the Kimballton DUSEL teamconfirm that this group has the experience to identify and mitigate any problemsassociated with rock bursts that might be encountered.

Johnston, J. C. & Einstein, H. H., “A Survey of Mining Associated Seismicity”,Proceedings, 2nd International Symposium on Rockbursts and Seismicity in Mines,Minneapolis, Minnesota, 1988, Fairhurst, Charles (Editor), A. A. Balkema,Rotterdam, Netherlands, ISBN 90 6191 145 1, 1990, pp. 121-127.

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Martin, C.D.; Kaiser, P.K. & Christiansson, R., “Stress, instability and the designof underground excavations.,” Int. J. Rock. Mech. Min. Sci, 2003, 40:1027-1047

Westman, E.C. and K.Y. Haramy, 1996, “Seismic tomography to map hazardsahead of the longwall face,” Mining Engineering, Vol. 48, No. 11, pp. 73-79.

Westman, E.C., K.Y. Haramy, and A.D. Rock, 1996, “Seismic tomography forlongwall stress analysis,” Proceedings of 2nd North American Rock MechanicsSymposium (Montreal, Quebec, June 19-21), ed. By M. Aubertin, F. Hassani, andH. Mitri, A.A. Balkema, pp. 397-403.

Westman, E. C., K. A. Heasley, P. L. Swanson, and S. Peterson, 2001, “Acorrelation between seismic tomography, seismic events and support pressure,”Rock Mechanics in the National Interest, Proceedings of the 38thU.S. RockMechanics Symposium, DC Rocks 2001, Washington D.C., July 10, 2001,Elsworth, Tinucci and Heasley eds., A.A. Balkema Publishers, p. 319 - 326.

Gutierrez, M. (1998), “Shear Band Formation in Rocks with a Curved FailureSurface,” International Journal of Rock Mechanics and Mineral Science, vol. 35,No. 415, pp. 447, paper no. 95.

Vadakos, S. and Gutierrez, M. (2005), “Distinct Element Modeling of theShimizu Tunnel #3, Tomei II, Japan,” Proc. Alaska Rocks 2005 Conference,accepted for publication.

Gutierrez, M. (2001), “Scale-Dependent Failure Model for Rocks Based onFracture Mechanics,” Proc. 2001 ASME-ASCE Mechanics and Materials SummerConf., San Diego, CA, June 27-29, 2001.

The following reference describes construction of SNO in rock burst prone rocks.

Castro, L.A.M.; McCreath, D.R. & Oliver, P. Rockmass damage initiation aroundthe Sudbury Neutrino Observatory cavern Proc. 2nd North American RockMechanics Symposium, Montreal, Aubertin, M.; Hassani, F. & Mitri, H. (ed.)A.A. Balkema, 1996, Vol 2, pp.1589-1595.

− CV of Dr. Mark Pierson was attached (4 pgs) − email correspondence the next day: Subject: Kimballton reply - accidental omission Rick and Dick - In the process of finalizing the Kimballton Team's response to the DUSEL panelists, one important statement was inadvertently dropped. The final question from the panel specifically asked about rock bursting in carbonate rocks at depth. Few data are available, however, the Gotthard Tunnel is currently being excavated through carbonate rocks (similar to those at Kimballton) to depths of over 2000 m and has had no problems with rock bursting. This point is significant and we regret its omission from our final reply. If possible, please forward this to the panel members. Many thanks, Erik Westman NSF reply: Erik, It would be difficult to include this in the panel decision now, but I also don't think it will affect the result. The Panel concluded that geoscience and engineering members of your team were so strong that if anyone could know the answer to that question they would. Best wishes, Richard