LBNF Excavation Alternatives SURF Team Follow up from LBNF Risk Review February 1st thru 4th, 2015

Option 1 Lower exhaust drift Would require another geotechnical program (perhaps adding ~ 1 year) Lots of excavation overall and in phase 1 Phase 1 does not allow a second cryostat to be built, so filling of detector 1 is delayed until phase 2 is complete Combined exhaust may offer opportunity to combine cooling, but it will be dusty during excavation Difficult to fully isolate excavation and outfitting In Domain 4 Outside Studied Area Antechamber should be longer Outside Studied Area, in domain 4 (?) This is the same layout that you have seen before.

Option 1 Schedule/Cost Total Cost: $174M+$5M exhaust path = $179M Both of these are required to allow detector 1 to fill Total Cost: $174M+$5M exhaust path = $179M Duration to allow filling of detector 1: 37 months as shown. Could be compressed to 22 months if excavation of caverns 1 and 2 overlap Total Duration: 60 months Cost and schedule include antechambers and septums (previous comparisons did not) This cost does not include the lower exhaust drift, which would add ~$5M to phase 1 (and overall) as drawn. It should not affect schedule.

Option 5 With septums and antechambers The septum and antechamber spaces can be rearranged in this layout with little impact on cost and schedule. For example, the antechamber could be in the middle. While not shown, additional drifts would be included between antechambers and between the northern antechamber and the existing drift. This is the same layout that you have seen before.

Option 5 Schedule/Cost Total Cost: $157M Phase 1 Duration: 20 months Total Duration: 36 months Cost and schedule include antechambers and septums (previous comparisons did not)

Option 6 : “H” arrangement This is the layout most recently proposed. The dominant new feature is a common antechamber area CF Does not recommend this option for several reasons: The large intersections create stress concentrations that may not be possible in this rock mass The concept of installing walls at the full cavern width is not feasible for excavation isolations due to air blast pressures without significantly reducing the efficiency of excavation Ventilation is complicated both during construction and operation. Most heat is in the utility space, so we would like to exhaust from that space. Additional drifts above or below could help with this. Because of items 2 and 3, all excavation would need to be completed in phase 1. Since CF does agree that a central utility space could have benefit, we offer two variations on the following slides

Option 6 Schedule/Cost For the reasons described on the previous slide, Option 6 has not been estimated. It is our belief, however, that this option cannot be efficiently constructed in phases as drawn, so the first and only phase would be on the scale of 3 years. Note that it may be possible to excavate with isolation as envisioned, but the blasting techniques would be much slower and more expensive. It may also be possible to excavate the large intersection as shown, but ground support would increase, increasing cost and schedule. A detailed 3d modeling of this would be required to deem whether it’s possible.

Option 5a Parallel Central Utility Space The southern cavern is outside the studied area, but we believe it may be close enough. Since the CF and cryogenics are in a separate chamber, there is no conflict with cryostat & detector laydown Option 5 modified by the Option 6 common antechamber concept.

Option 5a Schedule/Cost Total Cost: TBD Duration to allow filling of detector 1: 17 months Total Duration: 28 months

Option 5b Perpendicular Central Utility Space This alternative could allow for independent excavation of 4 caverns, but only with an independent exhaust drift (not shown) The eastern caverns extend into domain 4 The orientation of the central utility space is less favorable based on the rock foliation orientation. Option 5 modified by the Option 6 common antechamber concept. Perhaps more closely tied with Option 1

Option 5b Schedule/Cost Option 5b has not been estimated as of this presentation. Complications with rock foliation orientation suggest that a cost and schedule based on our “normal” assumptions would be misleading.

Comparison Our charge was to evaluate options 1, 5, and 6. Option 6 has too many complications to be evaluated fully, but we thought that the common antechamber area was interesting enough that we decided to add options 5A and 5B to the evaluation. Jim Strait edited the list of requirements generated by iEFIG for evaluations, classifying them as category 1 and 2. Jim suggested that only category 1 items be considered for comparison. Of the category 1 requirements, we believe that 7 are considered equal across all options and are therefore not helpful in comparing options. Three others are considered to be closely interrelated, and therefore have been combined into 1. Of the remaining requirements, 7 represent a fundamental distinction between options. The other 4 are items that require more or less design work/cost to achieve, but the core requirement can be met in any case. The following slides attempt to summarize the “engineers” analysis of options 1, 5, 5A, 5B, and 6 using the methodology described above.

Category 1 items that are the same for all options

Category 1 items with differences between options The 7 criteria that represent a fundamental difference between options are highlighted in yellow and simplified and ranked on the next slide. The other 4 are items that require more or less design work/cost to achieve, but the core requirement can be met equally in any case. All requirements CAN be met with any option.

Ranking and cost/schedule summary Criteria should be “weighted” based on importance. Rankings are based on the assumptions we’ve been using for layouts and phasing. Examples: Analysis to date has focused on quickest 10 kT. If the focus were on quickest 40 kT, we could approach excavation differently to make any option faster (parallel vs. serial excavation). This could change the rank of the second row. If stress distribution is more important than fitting within the geotechnical studied area, we could spread out options and change the ranking in that row.

Comparison Schedule Time during which interference would exist between excavation and all other activities (efficiency decrease, potential damage)

Option 5 with detector construction

Comments CERN and FNAL Cryogenic Engineers (Johan Bremer, David Montanari, Barry Norris, Mark Adamwoski) From the cryogenics point of view, we do not see large differences between the various options (1, 5, 5a, 5b, 6). Any potential difference is in the noise of the current estimates. In any scenario, there will be multiple activities in parallel: Construction of cryostat. Construction of cryogenic system (details below). Excavation of cavern. The following shall be ready when the first cryostat module is ready for cool down (perhaps this could be added as requirement for CF considerations?): Central facilities (electricity, cooling, etc.) for the common cryogenics and local cryogenics of cryostat n. 1. Common cryogenics (at least for Cryostat n. 1)  Cold Box(es), etc. Local cryogenics for Cryostat n. 1  LAr purification, condenser, etc. As long as the work can be done safely and in parallel as needed, we believe that we can work with any of these layouts. As already pointed out by CF, we also would like to underline that, in addition to multiple construction activities going on at the same time (construction of cryostat, construction of cryogenic system, excavation of subsequent caverns), there might be the need to handle a lot of equipment up/down the Ross shaft at the same time as well: parts for the installation of cryogenic equipment and cryostat, and waste rock removed by the excavation process. Installation sequences should be studied, but all layouts will be affected in the same way. We believe that the choice of the cavern layouts comes down to cost/schedule and CF and ODH considerations.

CF Concerns All previous cost discussion has been based on unimpeded access for excavation. If excavation is slowed due to vibration control and/or scheduling blasts, the costs could rise significantly. The standard evacuation distance during blasting is 2000 feet (610m). Alternatively, blasts could be restricted to shift change times. Either way, either excavation or experiment construction schedule will be affected. It is not possible to install cryogen piping in the Ross Shaft while excavating, nor prior to Ross Rehab completion. Installation of this piping is expected to take on the order of 6 months. This will impact critical path if excavation is phased with no delays. If a “hiatus” is introduced between phases to allow for this, it will add cost. For any phased excavation option, sharing the mucking ramp with deliveries of experiment equipment may be a problem. We have not addressed this. A better understanding of the cryostat/detector installation sequence is needed. If the number of deliveries per day is low we may be able to deliver materials to the base of the pit using the lower mucking drift. If materials can be installed from the upper elevation, using the mucking drift or a dedicated installation drift is not required. If excavation duration is too long (beyond 2024), the proposed rock disposal site may not be able to accept all waste rock.

Backup These are slides that you’ve seen before, included for reference if needed.

Alternative Excavation Comparison 1. Ross 10 kT’s 2. Parallel 10 kT’s 3. 10 + 30 kT 4. Single 40 kT 5. Two 20 kT Total Cavern Excavated Volume 162,000 m3 Total Drifts Excavated Volume 86,800 m3 88,300 m3 84,500 m3 58,800 m3 84,200 m3 Distance from Ross Shaft to Common Space (first cavern) 240m 510m Distance between Common Space and furthest cavern 200m 570m 220m 0m Conflict with operation) (Rank) 2 1 3 Clean/Dirty Interface (Rank) Egress (Rank) 4 Excavation cost of phase 1 (No escalation , EDIA, MR) $80M $46M $79M $121M $96M Total Excavation Cost (No escalation, EDIA, MR) $140M $134M $135M Excavation Schedule to 10 kT 19 mo 18 mo 14 mo 30 mo 17 mo Total Excavation Schedule 48 mo 49 mo 46 mo The schedules for caverns larger than 10 kT assume excavation from both ends. 10 kT caverns are assumed too short to allow this efficiently. Note that there are no antechambers, septums, concrete pit lining or steel structure, but this comparison has equal assumptions in all options. Options 1 and 5 have been changed in the main body of this presentation.

Septum/Antechamber Discussion Antechamber space costs ~$90,000/m ($363/m3) Septum space costs ~$162,000/m ($223/m3), but also provides 4-5 stories of space. Discussions with the cryo group have suggested two possible solutions: In any situation, CF requires 25m in an antechamber for electrical transformers and switchgear, chillers, air handlers, etc.. With 15m septums in each cavern, two caverns would have 25m antechambers for cryo equipment (50m total) and any additional caverns would have no cryo space in antechambers (25m total). Note that whether a septum is supporting one or two cryostats, it remains 15m for this discussion. A single cryostat scenario may be able to reduce that by ~5m. Without septums, two caverns would have 61.5m for cryo equipment (86.5m total), and any additional caverns would have 36.5m for cryo equipment (61.5m total). Each septum wall adds $1.2M. If the cryostats are steel supported, concrete walls may not be needed, so this cost isn’t considered here. Each septum steel structure adds $2M. It is not clear whether walls or steel structure are needed in antechambers, so this cost is not considered here. 4 Caverns w/septum 4 Caverns w/o septum 2 Caverns w/septum 2 Caverns w/o septum 1 Cavern w/septum 1 Cavern w/o septum Total septum length 60 30 45 Total Antechamber length 150 296 100 173 75 133 Cost $23,000,000 $27,000,000 $14,000,000 $16,000,000 $12,000,000

Septum, Antechamber Assumption Backup 4 cavern Scenario with septum: (4) 15m septums = 60M, (2) 50m antechambers + (2) 25m antechambers = 150m 4 cavern scenario without septum: (2) 86.5m antechambers + (2) 61.5m antechambers = 296m 2 cavern scenario with septum: (2) 15m septums = 30m, (2) 50m antechambers = 100m 2 cavern scenario without septum: (2) 86.5m antechambers = 170m 1 cavern scenario with septums: (3) 15m septums = 45m, (2) 25m cryo equipment spaces plus 25m CF space = 75m With a septum, the lay down space goes away. 1 cavern scenario without septums: (2) 46.5m cryo equipment spaces plus (1) 15m laydown space plus (1) 25m CF space = 133m

Cryo Equipment Layout This equipment and laydown area moves to the septum if a septum is used

CF Equipment Layout (25m) Chillers Standby Generator Fuel Chilled Water Pumps and Distribution Electrical Room Standby Generator

Other costs 1. Ross 10 kT’s 2. Parallel 10 kT’s 3. 10 + 30 kT 4. Single 40 kT 5. Two 20 kT Anticipated Infrastructure Cost Impact +$12M +$13M +$4M Reference Anticipated CM Cost Addition Total +$4.5M +$4.75M +$0M If only antechambers are used +$15M If septums are also used +$8M Maximum total impact for costs other than excavation +$31.5M +$32.75M Excavation Cost (from previous slide) +$19M +$14M Maximum Total CF Impact +$51M +$46M +$25M +$22M The table above is based on the following simplified assumptions Each cavern adds ~$4M infrastructure cost for power, HVAC, fire protection, etc. somewhat independent of size Each meter of drift length costs ~$1,600 for lighting, pipes, supports, etc. (for access drifts; ramps are much less). This has a minor effect. Note that this does not account for cryogen systems. Each month of excavation costs ~$250,000 for Construction management Antechamber and septum costs are from the previous slide