F. P. Calaprice4, P. Doe5,
K. T. Lesko2, M. L. Marshak3, Charles Nelson1,
D. Lee Peterson1, K. E.
Robinson2, J. Wang2 and J. F. Wilkerson5
1CNA Consulting
Engineers, Minneapolis MN,
2Ernest Orlando Lawrence
Berkeley National Laboratory, Berkeley CA,
3School of Physics and
Astronomy, University of Minnesota, Minneapolis MN,
4Department of Physics,
Princeton University, Princeton NJ,
5Department of Physics,
University of Washington, Seattle WA
Summary
The
Technical Assessment Sub-Committee has investigated four proposed national
underground science laboratory sites in the United States and visited existing
laboratories in Italy and Japan. In addition, the Sub-Committee has met twice
with the full Committee and interacted extensively through site visits,
telephone and email with advocates for the various sites. The Sub-Committee has
also solicited independent engineering and geological advice and has identified
and visited on its own several potential horizontal access sites in the
California-Nevada border region. In aggregate, the Sub-Committee has committed
more than one person-year to its studies.
The
site visits and discussions led the Sub-Committee to identify 28 individual
factors, grouped into 11 categories that are relevant to site selection. The
relative importance of these factors varies. The Sub-Committee reports
information about all of these factors both for the proposed sites and for the
laboratories in Italy and Japan. The Sub-Committee believes that in many
respects the Italian National Laboratory of Gran Sasso (LNGS) sets a “baseline”
that a new American laboratory must exceed. This criterion has led the
Sub-Committee to an assessment that is summarized here and discussed in the
report.
All
four sites investigated in detail are acceptable for underground research. The
depth factor alone justifies narrowing the site search to Homestake and San
Jacinto sites for a primary national facility. These two sites may well be
equivalent within the uncertainties of our criteria and assessments, but the
availability of the Homestake site is more time-dependent. Selecting between
these sites likely requires consideration of other factors, such as the success
probability of various development scenarios and tolerance for risk. With
respect to Carlsbad Underground National Laboratory and Soudan Laboratory, the
Sub-Committee believes that underground science that exploits the special
advantages of each of these sites should and will likely continue. The
Sub-Committee also suggests continued study at an appropriate level of the
California-Nevada border sites, to facilitate a deep alternative if both the
Homestake and San Jacinto sites prove infeasible.
The
Sub-Committee believes the case for a multi-purpose underground science
laboratory is compelling. The technical considerations assessed by the
Sub-Committee indicate that the project is feasible. Within one to five years,
the United States can have a world-leading facility to advance a wide range of
important science that requires very sensitive detectors and a very low
background environment. The Sub-Committee believes this initiative should
proceed on the fastest possible time scale.
This
report is organized in the following manner.
The first section introduces the charge, structure, methodology and
approach of the Technical Sub-Committee.
Section 2 discusses summary characteristics and attributes of each of
the principal sites or laboratories visited by the Sub-Committee. Section 3 explains the evaluation criteria
used in assessing the sites and the comparative characteristics of the sites
and laboratories to these characteristics.
The Sub-Committee analysis and summary are presented in Section 4. Appendix A is a glossary of mining and
excavation terms whose understanding aids in the discussion of the technical
aspects of the various sites. Appendix
B is the criteria document that was communicated to the various site advocates
in order to ensure that all sites would be studied and evaluated in the same
manner. Appendix C is a summary table
of specific items and cost information presented by the four major candidate
sites. Appendix D presents the findings
and preliminary evaluation of possible alternative candidate sites in the California-Nevada
border area.
1. Introduction
The
Technical Evaluation Sub-Committee was charged with developing a set of
criteria to evaluate sites for a possible national underground physics
laboratory in the United States, evaluating a set of sites against those
criteria and making an initial assessment regarding site selection. The
Sub-Committee gratefully acknowledges financial support for its efforts from
the National Science Foundation through the Institute for Nuclear Theory at the
University of Washington and from the U.S. Department of Energy through the
School of Physics and Astronomy at the University of Minnesota. The
Sub-Committee also wishes to express its thanks for the gracious hospitality it
has received from site proponents and interested citizens during its site
visits, and the cordial reception accorded to Committee members during site
visits to existing underground physics laboratories outside the United States.
A
brief summary of the Sub-Committee’s work is as follows: The Sub-Committee
retained the firm of CNA Engineers of Minneapolis to provide expertise and
advice to the Committee during its study. CNA Engineers has 17 years of
experience in engineering design and construction supervision at Soudan
Underground Physics Laboratory and has worked on numerous underground
transportation, workspace and sanitation projects in different parts of the
world. Sub-Committee members participated in a meeting with the full committee
in Alexandria, Virginia, on December 14. On January 9-11, Sub-Committee members
visited the Homestake Mine in Lead SD, followed by a visit to the Soudan Mine,
MN on January 12. Sub-Committee members next visited the National Laboratory of
Gran Sasso in Abruzzo, Italy, on January 29-30. They next visited the Kamioka
Laboratory in Mozumi, Japan on February 12-13, followed by a visit to the WIPP
site near Carlsbad NM on February 16. Several members of the Sub-Committee
visited possible site for a horizontal access laboratory along the
California-Nevada border on February 21-23. Sub-Committee members toured the
San Jacinto site near Palm Springs CA on February 28 and March 1. The Sub-Committee then met in Berkeley CA on
March 2 and reported to the full Committee on March 3-4. During this entire
process, the members of the Sub-Committee exchanged numerous emails and
telephone calls with each other, members of the full Committee, site proponents
and other interested persons.
To
assist site proponents in the preparation of pre-proposals and to help guide
its own thinking, the Sub-Committee prepared a document entitled Criteria for Technical Evaluation of an
Underground Laboratory Site, which is included as Appendix B. The
“Criteria” document includes work breakdown structure (WBS) for both the
capital and operations activities of a national underground laboratory. For
specificity, the “Criteria” document describes four example detectors. Detector
A is a modest-sized, ultra-low-background detector of the type that might be
used for a bb decay or a cold dark matter experiment.
The salient feature of Detector B is a large inventory (perhaps 1 kiloton) of
flammable liquid scintillator, similar to a super-Borexino or a super-KamLAND.
Detector C has an even larger inventory of a liquid cryogen, for example, 5
kilotons of argon. Finally, Detector D is an ultra-K detector, containing
perhaps 0.5 megatons of water. While these four example detectors do not
include all possibilities, they are good indicators of the types of stress that
will be placed on a national underground laboratory. Thus, they provide a good
metric for site evaluation.
The
Sub-Committee believes that in many ways the National Laboratory of Gran Sasso
(LNGS) provides a baseline for
evaluating national underground laboratory proposals and sites in the United
States. While the LNGS seems to be currently full and has a planned program of
experimentation well into the future, the Sub-Committee believes that LNGS
could and quite likely would make space for a new compelling and well-planned
experiment. Thus, the Sub-Committee believes that merely duplicating the
capabilities of LNGS in the United States is not sufficient. The new United
States National Underground Scientific Laboratory (USNUSL) should enable a new
generation of detectors with significant increases in sensitivity over what is
currently available. This goal of significant increase in sensitivity underlies
the discussion in this report.
The
Sub-Committee believes that historically physics detectors have attained
increased sensitivity in two ways—increasing signal and decreasing background.
One or more of the following specific strategies are likely necessary to
achieve the goal of higher sensitivity:
1. Increase
target or detector mass
2. Use
more sensitive and likely more exotic materials, for example, increasingly use
materials which are more costly, unstable, toxic, flammable, explosive or
cryogenic
3. Reduce
both direct and induced cosmogenic background with increased depth underground
4. Reduce
radioactivity background by locating in less radioactive rock, by improved
local shielding and/or by better control of radon
5. Increase
signal and/or reduce background by achieving lower levels of naturally
occurring radioactive impurities
6. Increase
signal and/or reduce background by using more and/or better electronics,
software algorithms and computer processing
The
first five of these strategies directly relate to the properties of the
proposed USNUSL and its infrastructure. Strategies involving electronics and
computer processing or software can presumably be implemented at any laboratory
site. The Sub-Committee criteria for evaluating possible laboratory sites are
thus related to the first five of these strategies to achieve a new level of
sensitivity in a wide range of low background detectors.
The
Sub-Committee’s methodology during its visits was to engage the site
proponent’s in vigorous discussion about how to prepare the best possible case
for each site. First, the Sub-Committee received information from the
advocates, in some cases in advance and in others during the site visit. The
Sub-Committee then inspected the physical site. Next the Sub-Committee
discussed the information received, the on-site observations and the
information received from its consultants with the site advocates. In some
cases, these discussions were quite extensive and resulted in major re-thinking
of their ideas by the site advocates. The Sub-Committee then received
additional and, in some cases, new information from the site advocates.
Finally, the Sub-Committee turned to an evaluative mode and attempted to assess
all the information it had received from the site advocates, from its own
observation and from its consultants with regard to each site.
We
note a caveat that should be used in considering our report. Our entire process
was very short. We very much appreciate the responses we received from site
advocates under extreme time pressure, but we realize, that of necessity, the
scope of these responses was limited. We restricted advocates to 10-page
pre-proposals, again because of the time constraints. Our process is perhaps
best regarded as a preliminary technical review. While we are confident of the
thrusts of our analyses, we believe the scientific communities should subject
actual proposals for a national underground science laboratory to extensive
peer review.
2.
Sites
The Sub-Committee has investigated two existing foreign laboratories—National Laboratory of Gran Sasso (LNGS) and Kamioka, four proposed sites—the Homestake Mine, San Jacinto, the Soudan Underground Physics Laboratory and the Waste Isolation Pilot Plant (WIPP). Near the end of the Sub-Committee’s consideration process, the proponents of a laboratory at WIPP renamed their proposal Carlsbad Underground National Laboratory (CUNL) and that name will be used to describe the WIPP site in the remainder of this report.
The
Sub-Committee also sought to locate possible sites without current proponents,
so-called green-field sites. A
laboratory built at an arbitrary location would require two new vertical shafts
or a single new vertical shaft divided into two independent shafts by a
fire-rated barrier. The construction cost of either arrangement to a depth of
2,500 m is likely greater than $200 million not including the cost of
laboratories, surface facilities or detectors. The Sub-Committee believes that
it would be difficult to justify such an expense. A more feasible alternative
is to find other sites similar to Mt. San Jacinto, where the ground elevation
changes so rapidly that a depth of 2,500 m could be achieved with a
horizontal access adit or tunnel of length 5,000 m to 10,000 m. The
construction cost for access in these sites is perhaps 50% of the cost of
sinking two shafts. In addition, the resultant horizontal access has lower
operating costs, lower costs for excavation of laboratories and lower costs for
detector installation than a vertical shaft laboratory. The Sub-Committee
identified many sites, but selected four such sites in the vicinity of the
California-Nevada border for on-site investigations. These sites are presented
here as a composite in a very preliminary context as the California-Nevada
sites.
2.1
National Laboratory of Gran Sasso (LNGS): The LNGS is located just outside Assergi between L’Aquila
and Teramo in the Abruzzo region of Italy, approximately 150 km east of
Rome. The LNGS was built as a supplement to a 11 km double tunnel on the
A24 autostrada that traverses the
Italian peninsula west-to-east from Rome to the Adriatic coast. The underground
laboratory with a depth of 3,800 mwe consists of three primary halls of
approximate dimension 20 m by 100 m by 20 m high. The access to
the LNGS is by vehicle from the westbound autostrada
tunnel. The experimental halls are connected by a series of underground drifts,
some of which are large enough to permit access by a standard highway
semi-trailer to each of the experimental halls. The LNGS has a campus
consisting of several buildings housing offices, laboratories, supply rooms,
machine shops, dormitory rooms and a cafeteria about 1 km outside the western
tunnel portal. Access from this campus to the underground laboratory requires
driving onto the autostrada, through
the entire length of the eastbound tunnel, accessing a special ramp and then
driving approximately halfway through the westbound tunnel. The return to the
outside campus is shorter, requiring only a drive halfway through the westbound
tunnel and then the 1 km to the campus.
The
LNGS has about 15 years of excellent operating experience. The replacement of
detectors by new detectors is now an ongoing process. An expansion of the LNGS
was authorized in 1990, but has been delayed by environmental and other
concerns. The LNGS is well subscribed by both old and new detectors, but could
likely accommodate a totally new detector within the next five years, if the
detector were funded and had a compelling physics rationale. LNGS is a truly
international laboratory.
2.2
Kamioka Observatory Laboratory (Super-K and KamLAND): The Kamioka Laboratory is located near
Mozumi, about 75 km south of Toyama, a port on the Sea of Japan. Mozumi is
approximately 300 km west of Tokyo. The Kamioka laboratory was built in a
mine complex at a shielding depth of 2700 mwe. It was initially accessed via a
7 km mine rail adit beginning on the mountainside above Mozumi. The
primary access now is through a 3 km vehicular adit capable of passing a
standard highway semi-trailer. The adit portal is located about 10 km by
road from Mozumi. The underground facilities consist primarily of two main
laboratories both upright cylinders with domed roofs. The smaller laboratory
with a liquid volume of approximately 10,000 m3 once housed the
Kamioka detector. The KamLAND liquid scintillator detector is now being
installed in this hall. The second hall, with a liquid volume of approximately
50,000 m3 houses the Super-Kamiokande detector. The complex
includes a few drifts that are used for access and some stub drifts that are
used for control rooms, storage and vehicle parking.
The
Kamioka Laboratory has an office building and a dormitory/cafeteria building,
both located in Mozumi. The round-trip from Mozumi to the laboratory requires
about 30 minutes. Because Mozumi is very small, population less than 1,000,
many visiting physicists live about 3/4-hour drive from Mozumi, towards the coast,
where the population is larger and services more numerous.
2.3
Carlsbad Underground National Laboratory: The proposed CUNL would have an underground laboratory
located at the Waste Isolation Pilot Plant, a government-owned, DOE facility.
WIPP is located about 50 km east of Carlsbad, Eddy County, NM in the
Permian Basin, a large deposit of halite and anhydride layers with underlying
rich deposits of petroleum and natural gas. The office-laboratory-stock room
complex for CUNL would likely be located in Carlsbad, possibly on land owned by
the State of New Mexico and used by New Mexico State University for an
environmental monitoring center.
The
CUNL laboratory site is an extraordinary complex of surface and underground
facilities, including state-of-the-art hoisting, ventilation and materials
handling systems. The underground site is completely dry; no pumping is
required. The current underground complex is located in an extensive salt
formation at a depth of 1,600-1,800 mwe. The CUNL proponents have developed
a plan to locate a laboratory complex near the bottom of the halite, a depth of
3,000-3,200 mwe. The site advocates and their technical consultants report
that depths below 3,200 mwe cannot be achieved at CUNL because of the risk
associated with digging into the hydrocarbon deposits known to exist below the
halite and anhydride beds.
2.4
Homestake Underground National Laboratory: The Homestake Gold Mine is located in Lead, Lawrence County,
SD. This mine has been worked for approximately 125 years and has more than
800 km of drifts at various levels with the deepest workings at
2,600 m. The mine has two active shafts (Yates shaft and Ross shaft) with
multi-compartment hoists that reach a level 1,600 m below the ground. From
there, access to the lower levels is via an internal winze (shaft) or via a
ramp system that accommodates rubber-tired vehicles. The Homestake mine has a
large number of surface buildings, many of which are quite old and probably not
of high utility for an underground laboratory. The heads of both shafts are
located within a 5-minute drive of the center of Lead. The nearest commercial
airport at Rapid City is about an hour drive to the east.
The
Homestake mine has a number of existing underground rooms that are for used for
various support functions at a variety of depths down to 2,100 m. These
rooms are typically 20 m by 50 m by 10 m in height. The rooms
are generally stabilized with conventional techniques such as rockbolting or
shotcreting, but appear stable over time intervals of more than 10 years.
Homestake could house laboratories at several different depths with a maximum
possible depth of about 7,200 mwe. Because of temperature and lithostatic
pressure considerations, the bulk of the low background laboratories would likely
be located at 6,500 mwe. Because of the configuration of the mine systems, a
likely location of less deep laboratories would be at about 4,500 mwe.
Converting the mine to a national underground laboratory would require
renovation of the mine’s mechanical and access systems, closing off a large
part of the mine that will not be used, and construction of new caverns to
house detectors. These detector laboratories would be located in
non-ore-bearing rock. The Homestake Mining Company also requires an indemnification
against liabilities as a result of science activities. This important issue
appears to require federal legislation.
2.5
Mount San Jacinto: Mt.
San Jacinto is located in Riverside County CA with its base rising at the
western edge of the City of Palm Springs CA. An aerial tramway operated by a
public authority traverses up most of the mountain’s western slope. The portal
for a proposed horizontal access adit (tunnel) to the Mt. San Jacinto
underground laboratory would begin about 1 km to the west of the Tramway Valley
Station, about 100 m south and connected to the Tramway access road. The
area around the portal is currently an overflow parking lot for the Tramway,
that has also been used to store refuse from the recent Tramway renovation. The
land required for the laboratory is mostly state-owned, either by the Tramway
authority or as part of a state park. The site of an external campus for the
San Jacinto laboratory is not yet defined, although the advocates suggest a
wide availability of sites in Palm Springs, a roughly 30 minute round trip from
the underground laboratory. These sites include private land and public land
assigned to higher education.
The
initial cost of the proposed San Jacinto Laboratory is significantly affected
by the length of the access adit, which in turn depends on the required
laboratory depth. The Sub-Committee believes the most desirable option achieves
a depth of 6,500 mwe with a slightly upward-sloping adit of approximately
7,700 m in length. Approximately 10% more depth could be achieved with a
somewhat shorter, downward-sloping adit, albeit with an additional operating
cost because of the need to pump water.
2.6
Soudan Underground Laboratory: The
Soudan Underground Laboratory is located at a depth of 2,200 mwe in St. Louis
County in northeastern Minnesota. The Soudan Laboratory is located in a
hematite mine converted to a state park in the 1960’s. Physics experiments at
Soudan started in 1981. Since that time, two large experimental halls have been
excavated, each approximately 15 m wide by 12 m high. The
Soudan 2 hall is about 70 m in length; the MINOS hall is
approximately 100 m in length. Currently, the Soudan Laboratory has only a
single usable shaft with a cage dimension of approximately 1 m wide by
2 m deep with the possibility of carrying lengths up to 12 m and
weights up to 6 tons. The Soudan Laboratory is the target for a Fermilab
neutrino beam that is currently under construction.
Because
of its shallow depth, the advocates of the Soudan Laboratory believe that it is
best suited for detectors that utilize it special capabilities of current
availability, staff experienced in installing and operating physics detectors
and a neutrino beam. Soudan is not suited for ultra-low background detectors
because of its limited depth. It is not suited for the detectors with
flammables or cryogens because of its single shaft. Building the large ultra-K water Cerenkov detector at
Soudan would require a new primary shaft with the existing shaft used as a
secondary escape. Available land exists for this option and the cost of the new
shaft would be a small fraction of the total project cost for “ultra-K.”
2.7
California-Nevada Border Horizontal Access Sites: The sites investigated in the
California-Nevada border region include Charleston Peak, between Las Vegas and
Pahrump in Nevada, Telescope Peak between Panamint Valley and Death Valley in
California, Mount Tom and Mount Morgan, west of Bishop CA and Boundary Peak in
the White Mountains almost directly on the California-Nevada border. It appears
possible to achieve depths of 6,000 mwe or more with horizontal or slightly
inclined adit lengths of 6,000 to 10,000 m. The Mt. Tom/Mt. Morgan site
has an existing, unused mine that allows a detailed investigation of the
geology without additional drilling. More information about these sites is
presented in Appendix D.
3.
Evaluation Factors
The
Sub-Committee used its collective experience in performing nuclear and
elementary particle physics experiments, including underground experiments, as
well as its observations during site visits to existing laboratories to develop
a set of evaluation factors that can be used to assess the potential of various
sites. Clearly, some of the factors are much more important than others. The
weights assigned to the various factors by different people will vary based on
individual experiences, tolerance for risk and general approach. The
Sub-Committee also believes that assessments on each factor can be combined in
different ways—that is, additively or multiplicatively. Indeed, some factors
should likely be combined one way and other factors should be combined another
way. Regardless of these concerns, the Sub-Committee used assessments with
respect to these factors to reach the conclusions that are reported in Section
4. The methodology issues lead to reliability estimates on the conclusions that
are also discussed in that section.
The recommended evaluation criteria
include the following 28 factors collected into 11 groups:
Group 1: Construction
Costs—access, underground halls, outfitting mechanical/electrical systems,
installing detectors
Group 2: Facility
Operating Costs
Group 3: Risk—environmental/permitting,
rock/salt structural integrity, seismic, mechanical systems
Group 4: Management—scientific,
site operations, ownership/sharing
Group 5: Depth
Group 6: Neutrino
Beam
Group 7: Time
to Detector Installation
Group 8: Outreach
Possibilities
Group 9: Local
Awareness and Support
Group 10: Laboratory
Context—cost of living, climate, travel to laboratory area, commuting to
laboratory, local universities, ease of access, local industrial
infrastructure, scientific environment
Group 11: Suitability
for Detectors—ultra-low background, flammables and cryogens, “ultra-K” large
water Cerenkov detector
3.1
Underground Costs: Both
capital and operating costs are clearly important criteria in site selection
and design of an underground science laboratory. During the site evaluation
process, the Sub-Committee developed some general understandings of cost
trade-offs for underground laboratories, which are reported here. Appendix C is a comparative table of the
four principal candidate sites of their shielding depth and estimated costs.
(a) Capital or construction cost: The
up-front cost of building a laboratory depends on a number of factors including
(1) existing physical plant, if any, (2) whether the laboratory is built in
rock or salt, (3) the quality of the ground, (4) the size of equipment that can
be used, (5) the amount of materials handling required and (6) the cost, skill
and availability of labor.
An
existing physical plant is
advantageous for a number of reasons, even if the laboratory is primarily built
new. Existing access permits direct inspection of the ground quality without
extensive test boring programs. An existing access has generally established a
history of permitting for the site, as well a public perception that heavy
construction on a site is expected. Existing access can be renovated, generally
at less cost than new construction. Even if not renovated, an existing access
can provide a secondary egress for safety or a ventilation access, reducing or
eliminating the need for these features in new construction. Finally, since
up-boring of a shaft is generally cheaper than down-boring, an existing access
can reduce the cost of new shaft development.
There
are some cost disadvantages associated with existing access. These include
possibly antiquated mechanical systems that might require substantial
maintenance or updating and buildings that need to be removed; other closure
issues associated with shrinking the size of the existing underground physical
plant to a needed and efficient size, including the cost of sealing off unused
areas and pumping from a larger than necessary physical plant; legacy
environmental issues and a need for workforce re-education and re-training to
adapt from mining to civil construction.
Unit
volume excavation costs in salt are
approximately 3 to 5 times less than construction costs in rock. Salt is generally excavated using continuous grinders that
are able to loosen enormous quantities of salt per person-hour worked. The
density of salt is about 20% less than the density of rock, resulting in lower
materials handling costs. In some locations, excavated salt can be sold, while
excavated rock is generally at best given away, reducing disposal costs. Salt
deposits are dry, so water handling is not required. Salt also exhibits plastic
flow and pure salt does not generally have faults.
Ground quality affects construction
costs in a number of different ways. The best ground is homogenous, high
compressive strength rock or pure halite or anhydride beds without clay or rock
inclusions. Areas with ore generally have heterogeneous rock and are less
desirable. Areas that have been mined or have fractures or faults or inclusions
have inhomogeneous stress fields and are more difficult both for design and
construction. The poorer the ground, the more ground support is required. This
ground support in the form of bolts, mesh and/or shotcrete increases both
project cost and time.
Project
cost is also affected by the size of
equipment that can be used for excavation and transportation of muck and
the amount of materials handling that
is required. Labor typically represents about 40% of total project cost. Larger
equipment can increase worker productivity and reduce labor cost. Each transfer
of excavated rock or muck from one conveyance to another also increases cost.
Since
labor is a significant cost, the cost,
availability and productivity of labor are all important factors. Under the
Davis-Bacon Act, labor costs are determined by the U.S. Department of Labor for
each type of worker in each geographic area. A shortage of labor can increase
costs through delay. Although, in principle, such delay costs to the
contractor, in reality, contractors who are losing money seek to recover some
of these losses from owners in a variety of ways. Well-trained and motivated
workers and efficient management can also reduce project costs. The relatively
high mobility of workers in the United States may limit the effect of these
factors.
The
cost of excavating shafts is
approximately two to three times the cost of excavating adits, drifts or tunnels of similar cross-section and length. This
cost primarily results from the materials handling problem. When rock or other
material is loosen by blasting or continuous mining in a tunnel project, the
loose material or muck can be easily scooped up with a front-end loader and
placed on a conveyer or in a skip or dump truck for disposal. This method
applies to downgrade tunnels, providing the slope of the excavation is not too
large. When material in a down-bored shaft project, it is difficult to pick up
and move. One exception is when the bottom of a new shaft is accessible via
another shaft. Then, the muck can be pushed down a bored hole and retrieved
using heavy equipment at the bottom. Another more efficient alternative is to
drive a shaft upward—a so-called raise. This approach also facilitates
automated mucking.
The
cost of tunnels and shafts can be as much as doubled by water infiltration along the entire length. Water infiltration
occurs in fractured ground conditions. Progress by either tunnel boring machine
(TBM) or drill-and-blast methods is slower in fractured ground due to rock
support issues. Furthermore, tunnels and shafts with water infiltration
generally require watertight linings that also slow the progress of the work.
In many cases, water infiltration and the resultant linings are only an issue
for a fraction of the tunnel or shaft length—perhaps 10%—and the costs are
reduced proportionately.
The
excavation costs for laboratory caverns
can vary by as much as a factor of two with lower costs for horizontal access.
Generally, horizontal access permits use of larger equipment, which results in
higher labor productivity, as discussed earlier. Secondly, horizontal access
generally reduces materials handling because muck can be directly loaded into
over-the-highway dump trucks and taken from the excavation site to a disposal
area with no further handling. A vertical access facility often requires moving
muck with underground transport, shifting it to a vertical skip and then moving
the muck to long distance transport on the surface.
(b) Operating cost: Over a 20-year
project lifetime, the laboratory operating costs are likely to exceed the
capital costs. In general, the operating costs depend on the number, size and
complexity of mechanical and other systems. These systems typically include:
hoisting (in vertical access laboratories), ventilation, pumping (in vertical
or downward-sloping horizontal access laboratories), cooling (depending on
electrical load and rock temperature), electrical and security. These costs for
a laboratory alone—not including the detectors’ operating costs—are likely to
amount to 5-10% of the capital cost per year. Because vertical access
laboratories have more systems than horizontal access laboratories, the
operating costs for a vertical access laboratory could be two to three times
higher than for horizontal access. Local wage scales will certainly affect
operating costs.
3.2 Construction Cost Factors
3.2.1.
Construction Cost for Access:
This factor includes site acquisition costs and costs for renovation and
construction of shafts, adits, roadways, hoisting mechanisms or any other
infrastructure required for both laboratory construction and ongoing physics
access to the actual laboratory sites. Essentially, this item includes all
capital costs other than costs specifically included in Factors 3.2.2 and 3.2.3
described below.
Gran
Sasso: Horizontal vehicular tunnel access mostly built as highway
project
Kamioka: original
access via 7 km mine rail adit built for mining; current main access
through single-lane vehicle adit
CUNL: Existing
access for small or shallow detectors. New shaft required for access to the
maximum 3,200 mwe level
Homestake: Proposed
plan would renovate and extend one shaft in Phase 2 of the project
San
Jacinto: New horizontal tunnel is required
Soudan: Existing
access for small detectors. New shaft would be required for “ultra-K” detector
3.2.2.
Construction Cost for Laboratories: The
Sub-Committee’s Technical Criteria document described three laboratories as
part of the conceptual plan for the USNUSL. This factor includes the cost of
preparing cavities for these laboratories including excavation, rock/salt
disposal, and rock bolting, shotcreting and other procedures required to
prepare clean, stable but empty caverns for detectors.
Gran
Sasso: 3 laboratories, each approximately 20 m by 100 m
by 20 m high built by drill-and-blast techniques with muck removal through
highway tunnel; hard limestone rock; horizontal access
Kamioka: Super-K
cavity holds approximately 50,000 m3 of water of water and
Kamiokande cavity (now housing KamLAND) approximately 5 times smaller; hard
rock; horizontal access
CUNL: Salt;
vertical access
Homestake: Hard
rock; vertical access
San
Jacinto: Hard rock; horizontal access
Soudan: Hard
rock; vertical access
3.2.3.
Construction Cost for Lab Mechanical Systems (Outfitting): In a typical underground laboratory, the
cost for outfitting may nearly equal the cost for construction. Outfitting
includes electrical power distribution, HVAC systems, life safety systems,
general-purpose rigging and detector support systems, networking and
communications systems and any other systems required to convert empty space
into an efficient physics laboratory. Outfitting costs will vary from one site
to another depending on costs of materials, prevailing wage rates and site
properties such as ambient rock temperature that affects HVAC systems and
method of egress that affects life safety systems. Davis-Bacon Wage Index
(DBWI) computed as (1 electrician +
0.5 boilermaker + 1 equipment operator + 1 concrete finisher)
normalized to Soudan as 1.00. The high level of integration in the American
economy may reduce the effects of local wage variations.
Gran
Sasso: Horizontal access
Kamioka: Horizontal
access
CUNL: Vertical
access, DBWI=0.80
Homestake: Vertical
access, DBWI=0.63
San
Jacinto: Horizontal access, DBWI=1.21
Soudan: Vertical
access, DBWI=1.00
3.2.4
Construction Cost for Detector Installation: The cost of installation varies from detector to detector
but it is at least 10 percent of a total detector cost and, in some cases, may
be more than 20 percent of the total cost. Installation may also be a
significant factor in the time required from approval of an experiment to the
first physics publication. In some cases, installation costs are understated,
because post-docs or graduate students perform a significant amount of
installation work. Some sites may have lower installation costs or shorter
installation times than other detectors because of ability to bring equipment
to the laboratory in larger or heavier units or because of lower installation
labor costs.
Gran
Sasso: Horizontal access for large equipment and sub-contractors;
large halls with bridge cranes provide adequate room for staging and good
materials handling capability
Kamioka: Horizontal
access for moderate-sized equipment and sub-contractors; limited staging area
CUNL: Large,
modern hoist currently exists to 2000 foot level
Homestake: Access
for detector installation is presently limited but improves after hoist and
shaft upgrading in Phase 2
San
Jacinto: Horizontal access for large equipment and
sub-contractors
Soudan: Installation
efficiency for “ultra-K” detector improves after construction of new shaft
3.3 Operating Cost
The
operating cost of a site is the expenditure required for site for maintenance
and depreciation of the site infrastructure not including the specific costs of
operation of any detectors. Operating costs for sites will vary depending on
prevailing wage rates and the extent and complexity of the mechanical systems
required by the site. Sharing the site with another entity that contributes to
operating costs for common access or other mechanical systems may reduce
laboratory operating costs.
Gran
Sasso: Maintenance of access mostly by autostrada agency; horizontal access requires fewer mechanical
systems
Kamioka: Access
shared with mining company; horizontal access requires fewer mechanical systems
CUNL: Vertical
access and ventilation systems shared with waste repository; pumping and
cooling not required
Homestake: Vertical
access; science is sole user of all systems including access, pumping,
ventilation and cooling
San
Jacinto: Horizontal access; science is sole user of
ventilation and cooling systems
Soudan: Vertical
access; share access and pumping with state park; mostly natural ventilation
3.4 Risk Factors
3.4.1
Permitting and Environmental Risk:
There is considerable experience both in United States and abroad of delay and
cost escalation in major projects, including scientific projects, due to
permitting and/or environmental considerations. There is no doubt that USNUSL
must operate in a safe and environmentally conscious manner. This factor
suggests more the time and expense required at various sites to determine what
is safe and environmentally sound. It also includes an estimation of the time
and cost that might be required to ascertain whether a particular detector
containing exotic materials could be installed at USNUSL.
Gran
Sasso: Laboratory expansion has been delayed for years over
environmental concerns
Kamioka: Historic
mining area; shared location between science and active mining
CUNL: Extensive
permitting history and experience; shared mission site with primary focus on
transuranic waste disposal
Homestake: Liability
release legislation required; historic mining area; single purpose site after
conversion
San
Jacinto: Large nearby population; single purpose site
Soudan: Historic
mining area; University of Minnesota issues own building permits
3.4.2
Rock/Salt Risk: This
risk factor includes multiple considerations relative to the risk of capital
and operating cost overruns due to unexpected rock or salt conditions. The
sites vary considerably in the degree of knowledge of actual rock conditions at
the proposed USNUSL site. The deep sites have high lithostatic pressures and
laboratory construction could encounter considerable difficulty, even in sites
with relatively well-known rock conditions. The risk in salt is different and
is related mostly to possible unexpected costs due to detector or support
structure misalignment as a result of salt creep or a possible need to re-mine
cavities
Gran
Sasso: Hard limestone rock; autostrada
tunnel permits access to rock in order to choose optimal laboratory site, but
major aquifers present
Kamioka: Hard
rock; extensive mining development permits access to rock in order to choose
optimal laboratory site
CUNL: Extensive
salt layer with clay layer intrusions
Homestake: Multiple
rock types; extensive mining development permits access to rock in order to
choose optimal laboratory site
San
Jacinto: Igneous rock batholith; not feasible to core
much of access tunnel prior to construction
Soudan: Multiple
rock types; schistose
3.4.3
Seismic Risk: Although
engineering can control seismic risk, there is an additional cost required to
build USNUSL and install detectors in a seismically active region. In addition,
there is a risk of a more intense than expected earthquake or an engineering or
installation mistake that leads to failure in an earthquake of expected
magnitude.
Gran
Sasso: Active seismic area; the highway tunnels traverse two
vertical faults and follow under a third horizontal fault.
Kamioka: An
active seismic region with mining-related local seismic activity
CUNL: No
seismic activity in recent geologic history
Homestake: No
seismic activity in recent geologic history:
San
Jacinto: San Jacinto and San Andreas faults within
25 km. Both faults are major and currently active.
Soudan: No
seismic activity in recent geologic history
3.4.4
Mechanical Systems Risk: Sites
with more extensive HVAC, hoisting or other machinery have an operating cost
risk due to the possibility of failure of significant mechanical systems. Such
failure could entail significant emergency operating expenditures and/or
significant lost time in access to the USNUSL. While the importance of this
factor is likely correlated with the magnitude of the operating cost, the
Sub-Committee deems this risk factor of sufficient importance to include it
separately.
Gran
Sasso: Horizontal access; only major mechanical system is
ventilation
Kamioka: Horizontal
access; major mechanical systems are ventilation and radon de-gasification
CUNL: Hoisting
and ventilation systems; risk shared with waste repository facility
Homestake: Hoisting,
ventilation, pumping and cooling systems
San
Jacinto: Ventilation and cooling systems
Soudan: Hoisting
and pumping systems; risk shared with state park
3.5 Management
3.5.1
Scientific Management: While
the ultimate decisions about scientific management will be made in discussion
with the funding agencies, this issue was discussed during several of the site
visits. The usual national laboratory model, both in the United States and
abroad, centers on an established scientist as the Scientific Director. A Board
of Directors appoints the Scientific Director, after extensive consultation in
the scientific community and with the funding agencies. The Board members are
themselves appointed by important national institutions. A Program Advisory
Committee, consisting of a broad range of scientific experts, advises the
Scientific Director. The quality of the laboratory program is reviewed by a
Visiting Committee, which includes expert scientists, who are mostly not
involved in the day-to-day activities of the Laboratory. Those scientists who
are directly involved in the Laboratory form a Users’ Committee to represent
their ideas and concerns.
Gran
Sasso: Management by INFN
Kamioka: Management
by Institute for Cosmic Ray Research (ICRR)
CUNL: LANL
(University of California), Department of Energy, New Mexico State University,
University of New Mexico plus others
Homestake: University
or other consortium including the South Dakota School of Mines & Technology
San
Jacinto: University of California, particularly UC
Irvine, plus others
Soudan: University
of Minnesota plus others
3.5.2
Site Operations Management: Management
of site operations may require somewhat different skills from scientific
management. While in the usual national laboratory model, site operations form
a distinct division that ultimately reports to the Scientific Director, other
models are possible. In particular, some sites have existing operational
structures with extensive knowledge and experience in operating the site. These
human resources are important and care must be taken to retain and enhance
them. In general, civil construction and laboratory operation are different
enough from mining operations and ore extraction that re-training and
re-deployment of existing staff may be advisable.
Gran
Sasso: Site operations management by INFN
Kamioka: Mining
operations and site work performed by Mitsui Corporation
CUNL: Site
operations management by Westinghouse TRU Solutions, the existing management
and operations contractor to the DOE
Homestake: Site
operations by existing staff following re-orientation and re-training
San
Jacinto: Assemble new staff under University of
California management
Soudan: Augment
existing physics operational staff
3.5.3
Ownership and Site Sharing: The
sites considered differ in whether use of the site is exclusive to USNUSL or
use of the site is shared with another entity. Sharing has an advantage in
reducing operating costs, but it has a disadvantage in potential access or
other conflicts. Sharing is particularly disadvantageous if the use other than
scientific research has priority. This factor also considers whether the
management entity for USNUSL has sufficient ownership and/or easements to
provide for future expansion or modification of the site capabilities.
Gran
Sasso: Access shared with autostrada, but otherwise dedicated site
Kamioka: Mining
activities in the past are now sharply curtailed
CUNL: Ownership
by DOE; shared use with waste repository
Homestake: Ownership
by State of South Dakota; exclusive science use
San
Jacinto: Ownership by State of California; exclusive
science use
Soudan: Ownership by State of Minnesota; shared use
with state park
3.6 Depth
Detectors
are placed underground primarily to lower backgrounds due to the direct and
indirect effects of cosmic rays. Direct effects include the passage of muon and
muon-generated particles through the detector. Indirect effects include
radioactivity generated by spallation and nuclear de-excitation following the
passage of a muon or muon-generated particle. Although the sensitivity of
particular detectors to depth varies, for most detectors deeper is better down
to depths at which neutrino-generated muons dominate the muon flux. Depths of
more than 7,000 mwe are probably not important but 7,000 mwe is clearly better
than 5,000 mwe. For the same vertical depth, a site with relatively flat
overburden has integrated flux equivalent depth about 10 percent greater than
that of a mountain. It is possible that some detectors would prefer shallower
depths, either to use remnant muon flux for testing or calibration or because
of somewhat lower costs associated with construction and operation at shallower
depths. For this reason, a site that offers a variety of depths, including one
or more deep locations, is likely preferably to a site with a single, fixed
depth.
Gran
Sasso: 3,800 mwe; mountain; single depth
Kamioka: 2,700
mwe; mountain; single depth
CUNL: 1,600-2,000
mwe now; 3,200 mwe later with new shaft; flat overburden; halite and anhydride
overburden has lower density but higher atomic number than rock
Homestake: 6,700
mwe most likely depth; flat overburden; most feasible depths include
700 mwe, 1,500 mwe; 2,100 mwe; 3,100 mwe; 3,400 mwe;
4,500 mwe; 7,200 mwe
San
Jacinto: 6,500 mwe; mountain; range of depths can
be selected by laboratory location
Soudan: 2,200
mwe; flat overburden; depth measured using muon flux
3.7 Neutrino Beam
The
study of neutrinos is an important feature of underground, low-background
physics. Current thinking is that the “ideal” baseline for a neutrino
oscillation experiment is approximately 2,500 km.
Gran
Sasso: 750 km to CERN
Kamioka: 300 km
to KEK
CUNL: 1,750
km to FNAL; 2,900 km to BNL
Homestake: 1,290 km
to FNAL; 2,530 km to BNL
San
Jacinto: 2,610 km to FNAL
Soudan: Beam
from FNAL currently under construction — 740 km to FNAL; 1,720 km to
BNL
3.8 Time to Install First Detectors
Although
the time scale for accelerator and non-accelerator nuclear and particle physics
experiments has become increasingly long, there is value to achieving the first
physics results as early as possible after authorization to establish a USNUSL.
This criterion clearly favors existing over new sites, but the Sub-Committee
believes that its importance justifies its inclusion.
Gran
Sasso: Currently operating
Kamioka: Currently
operating
CUNL: Small
detectors now; medium detectors in 6 months; large detectors at new, deeper
level in 3 years
Homestake: Small
detectors now, larger detectors in 1-3 years (new larger chambers in 1-2 years,
new hoist in 2-3 years).
San
Jacinto: 5 years
Soudan: Small
detectors now, ultra-K in 5 years
3.9 Outreach
The
American scientific community has a clear responsibility to America’s citizens
to inform them about the goals and progress of scientific research. The science
likely to take place at USNUSL is exciting fundamental science that can be well
communicated to both the general public and to diverse student and other
groups. This factor represents an estimation of both the outreach potential of
a particular site based on the size of the local permanent and vacationing
population and the perceived quality of any outreach plans described by the
site advocates.
Gran
Sasso: Good public visibility regionally and nationally; frequent
tours by school and other groups
Kamioka: Good
public visibility regionally and nationally; tours by school and other groups
CUNL: 500,000
tourists per year visit Carlsbad Caverns; NMSU outreach center program in
Carlsbad
Homestake: 3
million tourists per year in Black Hills
San
Jacinto: 300,000 residents in Coachella Valley; 15
million people live within 3-hour drive
Soudan: Ongoing
experience with outreach programs; history of coordination with state park;
40,000 tourists per year
3.10
Local Support and Awareness: The
siting of the USNUSL is clearly, in part, a political process. Awareness and
support by local citizens, governments and institutions is clearly an important
aspect of the siting process. Local governments and/or institutions can provide
some funding, especially in the early stages of the laboratory development. In
addition, the USNUSL will need to meet local regulations and codes with respect
to construction, transportation of materials and other operational aspects. The
site visits have also suggested to the Sub-Committee that local political
support as reflected through State Congressional delegations will likely have a
real effect on the progress of USNUSL.
Gran Sasso: Strong support by some municipalities and
groups and resistance by others.
Kamioka: Good
community awareness and support within local limited population
CUNL: Strong
local and political support; growing public awareness
Homestake: Strong
local and political support; extensive public awareness
San
Jacinto: Strong local support; limited public and
political awareness
Soudan: Strong
local support; extensive public awareness
3.11 Site Environmental Factors
3.11.1
Cost of Living: This
factor affects USNUSL through the cost to maintain graduate students, post-docs
and visitors at the USNUSL site. Although this cost does not accrue directly to
USNUSL, it likely affects the ability and willingness of collaborating
institutions to maintain people on site for detector installation and
operation. The cost for each site listed below includes a two-week stay at a
moderately priced hotel (for example, Day’s Inn), airfare from Chicago and
meals).
CUNL: $1,547
Homestake: $1,533
San
Jacinto: $2,754