# Future Circular Collider Feasibility Study Report:
## Volume 3, Civil Engineering, Implementation and
Sustainability

M. Benedikt, F. Zimmermann, B. Auchmann, W. Bartmann, J.P Burnet, C.

Carli, A. Chancé, P. Craievich, M. Giovannozzi, C. Grojean, et al.

► To cite this version:

M. Benedikt, F. Zimmermann, B. Auchmann, W. Bartmann, J.P Burnet, et al., Future Circular Collider Feasibility Study Report: Volume 3, Civil Engineering, Implementation and Sustainability. Eur.Phys.J.ST, 2025, 234 (3), pp.5113-5383. 10.1140/epjs/s11734-025-01958-5. hal-05057622

HAL Id: hal-05057622

https://hal.science/hal-05057622v1

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Review

# Future Circular Collider Feasibility Study Report

## Volume 3 Civil Engineering, Implementation and Sustainability

M. Benedikt¹, F. Zimmermann¹, B. Auchmann¹,², W. Bartmann¹, J.P. Burnet¹, C. Carli¹, A. Chancé³,
P. Craievich², M. Giovannozzi¹, C. Grojean⁴,⁵, J. Gutleber¹, K. Hanke¹, A. Henriques¹, P. Janot¹, C. Lourenço¹,
M. Mangano¹, T. Otto¹, J. Poole¹, S. Rajagopalan⁶, T. Raubenheimer⁷, E. Todesco¹, L. Ulrici¹, T. Watson¹,
G. Wilkinson¹,⁸, A. Abada⁹,¹⁰,¹¹, M. Abbrescia¹²,¹³, H. Abdolmaleki¹⁴,¹⁵, S.H. Abidi⁶, A. Abramov¹,
C. Adam⁹,¹⁶,¹⁷, M. Ady¹, P.R. Adžić¹⁸, I. Agapov⁴, D. Aguglia¹, I. Ahmed¹⁹, M. Aiba², G. Aielli²⁰,²¹,
T. Akan²², N. Akchurin²³, D. Akturk²⁴, M. Al-Thakeel¹,²⁵,²⁶, G.L. Alberghi²⁵, J. Alcaraz Maestre²⁷,
M. Aleksa¹, R. Aleksan³, F. Alharthi⁹,¹⁰,²⁸, J. Alimena⁴, A. Alimenti²⁹, S. Alioli³⁰,³¹, L. Alix¹,⁹,¹⁶,
B.C. Allanach³², L. Allwicher⁴, A.A. Altintas³³, M. Altmh³³,³⁴, M. Alviggi³⁵,³⁶, G. Ambrosio³⁷, Y. Amhis⁹,¹⁰,¹¹,
A. Amiri³⁸,³⁹, G. Ammirabile⁴⁰, T. Andeen⁴¹, K.D.J. André¹, J. Andrea⁹,⁴²,⁴³, A. Andreazza⁴⁴,⁴⁵, M. Andreini¹,
T. Andriollo⁴⁶, L. Angel⁴⁷, M. Angelucci⁴⁸, S. Antusch⁴⁹, M.N. Anwar¹²,⁵⁰, L. Apolinário⁵¹, G. Apollinari³⁷,
R.B. Appleby⁵²,⁵³, A. Apresyan³⁷, Aram Apyan⁵⁴, Armen Apyan⁵⁵, A. Arbey⁹,⁵⁶,⁵⁷, B. Argiento³⁵,³⁶, V. Ari⁵⁸,
S. Arias⁵⁹, B. Arias Alonso¹, O. Arnaez⁹,¹⁶,¹⁷, R. Arnaldi⁶⁰, F. Arneodo⁶¹, H. Arnold⁶², P. Arrutia Sota¹,
M.E. Ascioti⁶³,⁶⁴, K.A. Assamagan⁶, S. Aumiller⁶⁵, G. Aydin⁶⁶, K. Azizi³⁸,⁶⁷, P. Azzi⁶⁸, N. Bacchetta⁶⁸,
A. Bacci⁴⁴, B. Bai⁶⁹, Y. Bai⁷⁰, L. Balconi⁴⁴,⁴⁵, G. Baldinelli⁶³,⁶⁴, B. Balhan¹, A.H. Ball¹,⁷¹, A. Ballarino¹,
S. Banerjee²⁷, S. Banik²,⁷³, D.P. Barber⁴,⁷⁴, M.B. Barbero⁹,⁷⁵,⁷⁶, D. Barducci⁴⁰,⁷⁷, D. Barna⁷⁸,
G.G. Barnaföldi⁷⁸, M.J. Barnes¹, A.J. Barr⁸, R. Bartek⁷⁹, H. Bartosik¹, S.A. Bass⁸⁰, U. Bassler⁹,⁸¹,⁸²,
M.J. Basso⁸³,⁸⁴, A. Bastianin⁴⁵,⁸⁵, P. Bataillard⁸⁶, M. Battistin¹, J. Bauche¹, L. Baudin¹, J. Baudot⁹,⁴²,⁴³,
B. Baudouy³, L. Bauerdick³⁷, C. Bayndir⁸⁷,⁸⁸, H.P. Beck⁸⁹, F. Bedeschi⁴⁰, C. Bee⁶², M. Begel⁶, M. Behtouei⁴⁸,
L. Bellagamba²⁵, N. Bellegarde¹, E. Belli¹,⁹⁰, E. Bellingeri⁹¹, S. Belomestnykh³⁷, A.D. Benaglia³⁰,
G. Bencivenni⁴⁸, J. Bendavid¹, M. Benmergui⁹², M. Benoit⁹³, D. Benvenuti¹,⁴⁰, T. Bergauer⁹⁴, N. Bernachot⁹⁵,
G. Bernardi⁹,⁹⁶,⁹⁷, J. Bernardi⁹⁸, Q. Berthet⁹⁹,¹⁰⁰,¹⁰¹, S. Bertoni¹⁰², C. Bertulani¹⁰³, M.I. Besana²,
A. Besson⁹,⁴²,⁴³, M. Bettelini¹⁰⁴, S. Bettoni², S. Beuvier¹⁰⁵, P.C. Bhat³⁷, S. Bhattacharya¹⁰⁶, J. Bhom¹⁰⁷,
M.E. Biagini⁴⁸, A. Bibet-Chevalier¹⁰⁸, M. Bicrel¹⁰⁹, M. Biglietti¹¹⁰, G.M. Bilei⁶³, B. Bilki¹¹¹,¹¹²,
K. Bisgaard Christensen¹, T. Biswas¹¹³, F. Blanc¹¹⁴, F. Blekman⁴,¹¹⁵,¹¹⁶, A. Blondel⁹,¹⁰¹,¹¹⁷, J. Blümlein⁴,
D. Boccanfuso³⁵,¹¹⁸, A. Bogomyagkov¹¹⁹, P. Boillon¹⁰⁸, P. Boivin¹⁰⁰, M.J. Boland¹²⁰, S. Bologna¹²¹,
O. Bolukbasi³³, R. Bonnet¹⁰², J. Borburgh¹, F. Bordry¹, P. Borges de Sousa¹, G. Borghello¹, L. Borriello³⁵,
D. Bortoletto⁸, M. Boscolo⁴⁸, L. Bottura¹, G. Boudoul⁹,⁵⁶,⁵⁷, V. Boudry⁹,⁸¹,⁸², R. Boughezal¹²²,
D. Bourilkov¹²³, M. Boyd⁸³,¹²⁴, D. Boye⁶, G. Bozzi¹²⁵,¹²⁶, V. Braccini⁹¹, C. Bracco¹, B. Bradu¹, A. Braghieri¹²⁷,
S. Braibant²⁵,²⁶, J. Bramante¹²⁸, G.C. Branco¹²⁹, R. Brenner¹³⁰, N. Brisa¹⁰², D. Britzger¹³¹, G. Broggi¹,⁹⁰,
L. Bromiley¹, E. Brost⁶, Q. Bruant³, R. Bruce¹, E. Bründermann¹³², L. Brunetti⁹,¹⁶,¹⁷, O. Brüning¹,
O. Brunner¹, X. Buffat¹, E. Bulyak¹³³, A. Burdyko⁴⁴,¹³⁴, H. Burkhardt¹,¹³⁵, P.N. Burrows¹³⁶, S. Busatto⁴⁴,⁹⁰,
S. Buschaert⁸⁶, D. Buttazzo⁴⁰, A. Butterworth¹, D. Butti¹, G. Cacciapaglia¹³⁷,¹³⁸,¹³⁹, Y. Cai⁷, B. Caiffi¹⁴⁰,
V. Cairo¹, O. Cakir⁵⁸, P. Calafiura¹⁴¹, R. Calaga¹, S. Calatroni¹, D.G. Caldwell¹⁴², A. Çalışkan¹⁴³,
C. Calpini¹⁴⁴, M. Calviani¹, E. Camacho-Pérez¹⁴⁵, P. Camarri²⁰,²¹, L. Caminada²,⁷³, M. Campajola³⁵,³⁶,
A.C. Canbay⁵⁸, K. Canderan¹, S. Candido¹, F. Canelli⁷³, A. Canepa³⁷, S. Cantarella⁴⁸, K.B. Cantún-Avila¹⁴⁵,
L. Capriotti¹⁴⁶,¹⁴⁷, A. Caram¹⁴⁸, A. Carbone⁴⁴, J.M. Carceller¹, G. Carini⁶, F. Carlier¹,
C.M. Carloni Calame¹²⁷, F. Carra¹, C. Cartannaz⁸⁶, S. Casenove¹, G. Catalano¹⁴⁹, V. Cavaliere⁶,
C. Cazzaniga¹⁵⁰, C. Cecchi⁶³,⁶⁴, F.G. Celiberto¹⁵¹, M. Cepeda²⁷, F. Cerutti¹, F. Cetorelli³⁰,³¹, G. Chachamis⁵¹,
Y. Chae⁴, F. Chagnet¹⁵², I. Chaikovska⁹,¹⁰,¹¹, M. Chalhoub⁸⁶, M. Chamizo-Llatas⁶, M. Champagne¹⁵³,

S. Beuvier and M. Klein are deceased.

M. Benedikt is the Study Leader.

F. Zimmermann is the Deputy Study Leader.

B. Auchmann, W. Bartmann, J.P. Burnet, C. Carli, A. Chancé, P. Craievich, M. Giovannozzi, C. Grojean, J. Gutleber,

K. Hanke, A. Henriques, P. Janot, C. Lourenço, M. Mangano, T. Otto, J. Poole, S. Rajagopalan, T. Raubenheimer,

E. Todesco, L. Ulrici, T. Watson and G. Wilkinson are Editors.

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M. Benedikt
H. Chanal¹⁹,¹⁵,¹⁴,¹⁵, G. Chapelier¹⁰⁸, P. Charitos¹, C. Charles¹⁰⁵, T.K. Charles¹⁵⁶, C. Charlot⁹,⁸¹,⁸², S. Chatterjee⁴, A. Chaudhuri¹⁵⁷, R. Chehab⁹,¹⁰,¹¹, S.V. Chekanov¹⁵⁸, A. Chen⁶, T. Chesne¹⁵⁰, F. Chiapponi²⁵,²⁶, G. Chiarello¹⁵⁹,¹⁶⁰, M. Chiesa¹²⁷, P. Chiggiato¹, P. Chomaz³, M. Chorowski¹⁶¹, J.P. Chou¹⁶², M. Chrzaszcz¹⁰⁷, W. Chung¹⁶³, S. Ciarlantini⁶⁸,¹⁶⁴, A. Ciarma⁴⁸, D. Cieri¹³¹, A.K. Ciftci¹⁶⁵, R. Ciftci¹⁶⁶, R. Cimino⁴⁸, F. Cirotto³⁵,³⁶, M. Ciuchini¹¹⁰, M. Cobal¹⁶⁷,¹⁶⁸, A. Coccaro¹⁴⁰, R. Coelho Lopes De Sa¹⁶⁹, J.A. Coleman-Smith¹, F. Collamati¹⁷⁰, C. Colldelram¹⁷¹, P. Collier¹, P. Collins¹, J. Collot⁹,¹⁷²,¹⁷³, M. Colmenero¹, L. Colnot¹⁴⁹, G. Coloretti⁷³, D. Contardo⁹,⁵⁶,⁵⁷, E. Conte⁹,⁴²,⁴³, F.A. Conventi³⁵,¹⁷⁴, A. Cook¹, L. Cooley¹⁷⁵,¹⁷⁶, A.S. Cornell¹⁷⁷, C. Cornella¹, G. Cornette¹⁰⁵, I. Corredoira¹⁷⁸, P. Costa Pinto¹, F. Couderc¹, J. Coupard¹, S. Coussy⁸⁶, G. Crawford¹⁷⁹, R. Crescenzi¹⁸⁰, I. Crespo Garrido¹,¹⁸¹, T. Critchley¹,¹⁰¹, A. Crivellin⁷³, T. Croci⁶³, C. Cudré¹⁰⁵, G. Cummings³⁷, F. Cuna¹², R. Cunningham¹, B. Curé¹, E. Curtis¹⁸², M. D’Alfonso¹⁸³, L. D’Aloia Schwartzentruber¹⁸⁴, G. D’Amen⁶, B. D’Anzi¹²,¹³, A. D’Avanzo³⁵,³⁶, D. d’Enterria¹, A. D’Onofrio³⁵, M. D’Onofrio¹⁸⁵, M. Da Col¹⁴⁹, M. Da Rocha Rolo⁶⁰, C. Dachauer¹⁸⁶, B. Dağlı²⁴, A. Dainese⁶⁸, B. Dalena³, W. Dallapiazza¹⁸⁷, M. Dam¹⁸⁸, H. Damerau¹, V. Dao⁶², A. Das¹⁸⁹, M.S. Daugaard¹, S. Dauphin¹⁰⁸, A. David¹, T. Davídek¹⁹⁰, G.J. Davies¹⁸², J. Davighi¹, S. Dawson⁶, J. de Blas¹⁹¹, A. de Cosa¹⁵⁰, S. De Curtis¹⁹², N. De Filippis¹²,⁵⁰, E. De Lucia⁴⁸, R. De Maria¹, E. De Matteis⁴⁴, A. De Roeck¹, A. De Santis⁴⁸, A. De Vita¹,⁶⁸,¹⁶⁴, A. Deandrea⁹,⁵⁶,⁵⁷, C.J. Debono¹⁹³, M. Deeb¹⁰⁰, M.M. Defranchis¹, J. Degens¹⁸⁵, S. Deghaye¹, V. Del Duca⁴⁸, C.L. Del Pio⁶, A. Del Vecchio⁹⁰, D. Delikaris¹, A. Dell’Acqua¹, M. Della Pietra³⁵,³⁶, M. Delmastro⁹,¹⁶,¹⁷, L. Delprat¹, E. Delugas¹⁴⁹, Z. Demiragli¹⁹⁴, L. Deniau¹, D. Denisov⁶, H. Denizli¹⁹⁵, A. Denner¹⁹⁶, A. Denot¹⁰⁸, G. Deptuch⁶, A. Desai¹⁹⁷, H. Deveci¹, A. Di Canto⁶, A. Di Ciaccio²⁰,²¹, L. Di Ciaccio⁹,¹⁶,¹⁷, D. Di Croce¹,¹¹⁴, C. Di Fraia³⁵,³⁶, B. Di Micco²⁹,¹¹⁰, R. Di Nardo²⁹,¹¹⁰, T.B. Dingley⁸, F. Djama⁹,⁷⁵,⁷⁶, F. Djurabekova¹⁹⁸, D. Dockery³⁷, S. Doebert¹, D. Domange¹,¹⁹⁹, M. Donegà¹⁵⁰, U. Dosselli⁶⁸, H.A. Dostmann¹,²⁰⁰, J.A. Dragovich³⁷, I. Drebot⁴⁴, M. Drewes²⁰¹, T.A. du Pree²⁰², Z. Duan²⁰³, C. Duarte-Galvan²⁰⁴, O. Duboc²⁰⁵, I. Dubovyk²⁰⁶, M. Duda², P. Duda¹⁶¹, H. Duran Yildiz⁵⁸, H. Durand¹⁰⁵, P. Durand¹⁰⁵, G. Durieux²⁰¹, Y. Dutheil¹, I. Dutta³⁷, J.S. Dutta²⁰⁷, S. Dutta²⁰⁸, F. Duval¹, F. Eder¹, M. Eisterer⁹⁸, Z. El Bitar⁹,⁴²,⁴³, A. El Saied²⁰⁹, M. Elisei⁴⁴, J. Ellis¹,²¹⁰, W. Elmetenawee¹², J. Elmsheuser⁶, V. Daniel Elvira³⁷, S.C. Eno²¹¹, Y. Enomoto²¹², B.A. Erdelyi⁶⁸,¹⁶⁴, O.E. Eruteya¹⁰¹,²¹³, M. Escobar²¹⁴, O. Etisken²¹⁵, I. Eymard¹⁴⁴, J. Eysermans¹⁸³, D. Falchieri²⁵, C. Falkenberg²⁰⁵, F. Fallavollita¹,¹³¹, A. Afalou¹,⁹,¹⁰, J. Faltova¹⁹⁰, J. Fanini¹, L. Fanò⁶³,⁶⁴, K. Fanti¹⁰⁵, R. Farinelli²⁵, M. Farino¹⁶³, S. Farinon¹⁴⁰, H. Fatehi³⁸, J. Fatterbert¹⁰⁵, A. Faure²¹⁶, A. Faus-Golfe⁹,¹⁰,¹¹, G. Favia¹, L. Favilla³⁵,¹¹⁸, W.J. Fawcett³², A. Federowicz³⁷, L. Feligioni⁹,⁷⁵,⁷⁶, L. Felsberger¹, Y. Feng²³, A. Fernández Téllez²¹⁷, R. Ferrari¹²⁷, L. Ferreira¹, F. Ferro¹⁴⁰, M. Fiascaris¹, C. Fiorio⁴⁵, S.A. Fleury¹, L. Florez¹⁸⁷, M. Florio⁴⁵,¹⁴⁹, A. Fondacci⁶³, B. Fontimpe²¹⁴, K. Foraz¹, R. Fortunati², M. Fouaidy⁹,¹⁰,¹¹, A. Foussat¹, A. Fowler¹, J.D. Fox²¹⁸, M. Francesconi³⁵, B. Francois¹, R. Franqueira Ximenes¹, F. Fransesini⁴⁸, A. Frasca¹,¹⁸⁵, A. Freitas²¹⁹, J.A. Frost⁸, K. Furukawa²¹², A. Gabrielli²⁵,²⁶, A. Gaddi¹, F. Gaede⁴, A. Gallén¹³⁰, R. Galler²²⁰,²²¹, E. Gallici¹⁰⁵, E. Gallo⁴,¹¹⁵, H. Gamper¹, G. Ganis¹, S. Ganjour³, S. Gao⁶, A. Garand¹⁴⁸, C. Garaus²⁰⁵, D. Garcia¹, R. García Alía¹, R. García Gil²²², C.M. Garcia Jaimes¹,¹¹⁴, H. Garcia Rodrigues²,²²³, C. Garion¹, M. Garlaschè¹, D. Garnier¹⁵², M.V. Garzelli¹¹⁵, S. Gascon-Shotkin⁹,⁵⁶,⁵⁷, M. Gasior¹, G. Gaudino³⁵,¹¹⁸, G. Gaudio¹²⁷, V. Gaur²²⁴, K. Gautam⁷³,¹¹⁶, V. Gawas¹, T. Gehrmann⁷³, A. Gehrmann-De Ridder⁷³,¹⁵⁰, K. Geiger¹, M. Genco¹⁴⁹, F. Gerigk¹, H. Gerwig¹, A. Ghribi¹,⁹,²²⁵, P. Giacomelli²⁵, S. Giagu⁹⁰,¹⁷⁰, E. Gianfelice³⁷, S. Giappichini¹³², D. Gibellieri¹,²²⁶, F. Giffoni¹⁴⁹, G. Gil da Silveira²²⁷, S.S. Gilhardoni¹, M. Giovannetti⁴⁸, T. Girardet¹⁰⁵, S. Girod¹,¹⁰⁵, P. Giubellino⁶⁰, P. Giubilato⁶⁸,¹⁶⁴, F. Giuli²⁰,²¹, M. Giuliani¹⁰², E.L. Gkoukousis¹,⁷³, S. Glukhov²²⁸, J. Gluza²⁰⁶, B. Goddard¹, C. Goffing¹,¹³², D. Goldsworthy¹, T. Golling¹⁰¹, R. Gonçalo⁵¹,²²⁹, V.P. Gonçalves⁴⁷,²³⁰, T. Gonçalves Da Silva²¹⁴, J. Gonski⁷, R. Gonzalez Suarez¹³⁰, S. Gorgi Zadeh¹, S. Gori²³¹, E. Gorini¹⁵⁹,²³², L. Gouskos²³³, M. Gouzevitch⁹,⁵⁶,⁵⁷, E. Granados¹, F. Grancagnolo¹⁵⁹, S. Grancagnolo¹⁵⁹,²³², A. Grassellino³⁷, A. Grau¹³², E. Graverini⁴⁰,⁷⁷,¹¹⁴, F.G. Gravili¹⁵⁹,²³², H.M. Gray¹⁴¹,²³⁴, M. Grazzini³³, Mario Greco²⁹,¹¹⁰, Michela Greco⁶⁰,²³⁵, A. Greljo⁴⁹, J.-L. Grenard¹, A.V. Gritsan²³⁶, R. Gröber⁶⁸,¹⁶⁴, A. Grudiev¹, E. Gschwendtner¹, J. Gu²³⁷, D. Guadagnoli¹⁷,¹³⁷,²³⁸, G. Guerrieri¹, A. Guiavarch²⁰⁹, G. Guillermo Canton¹,²³⁹, M. Guinchard¹, Y.O. Günaydin²⁴⁰, K. Gurcel⁹², L.X. Gutierrez Guerrero²⁴¹,²⁴², D. Gutiérrez Rueda¹, A. Gutiérrez-Rodríguez²⁴³, V. Guzey¹⁹⁸,²⁴⁴, C. Haber¹⁴¹, T. Hacheney²⁴⁵, B. Hacışahinoğlu³³, K. Hahn¹²², J. Hajer¹²⁹, T. Hakulinen¹, J.C. Hammersley²⁴⁶, M. Hance²³¹, J.B. Hansen¹⁸⁸, B. Härer¹³², E. Hauzinger²²⁰, M. Haviernik¹⁹⁰, B. Hegner¹, C. Helsens¹¹⁴, Ana Henriques¹, C. Hernalsteens¹, H. Hernández-Arellano²¹⁷, R.J. Hernández-Pinto²⁰⁴, M.A. Hernández-Ruíz²⁴³, J. Hernández-Sánchez²¹⁷, J.W. Heron¹, L.M. Herrmann¹, R. Hirosky²⁴⁷, J.F. Hirschauer³⁷, J.D. Hobbs⁶², K. Hock⁶, S. Höhe³⁷, M. Hofer¹, G. Hoffstaetter⁶,²⁴⁸, W. Höfle¹, M. Hohlmann²⁴⁹, F. Holdener²⁵⁰, B. Holzer¹, C.G. Honorato²¹⁷, H. Hoorani²⁵¹, A. Houver¹⁰⁵, E. Howling¹,⁸,¹³⁶, X. Huang⁷, F. Hug²⁵², B. Humann¹, P. Hunchak¹²⁰, Y. Husein¹, A. Hussain¹,²⁵³, G. Iadarola¹, G. Iakovidis⁶, G. Iaselli¹²,⁵⁰, P. Iengo³⁵, A. Ilg⁷³, M. Iodice¹¹⁰, A.O.M. Iorio³⁵,³⁶, V. Ippolito¹⁷⁰, U. Iriso¹⁷¹, J. Isaacson³⁷, G. Isidori⁷³, R. Islam²⁵⁴, A. Istepanyan¹⁰⁵, S. Izquierdo Bermudez¹, V. Izzo³⁵, P.D. Jackson¹⁹⁷, R. Jafari¹,³⁸, S.S. Jagabathuni¹,¹⁰¹, S. Jana²⁵⁵,²⁵⁶, C. Järmyr Eriksson¹, P. Jausserand¹⁵², M. Jensen²⁵⁷, J.M. Jimenez¹, F.R. Joaquim¹²⁹, O.R. Jones¹, J. Joos¹⁰⁸, E. Jourd’huy⁹,²⁵⁸, E. Jourdan²¹⁴, J.M. Jowett¹,²⁵⁹, A. Jueid²⁶⁰, A.W. Jung²⁰⁷,
M. Kagan⁷, I. Kahraman⁵⁸, V. Kain¹, J. Kalinowski²⁶¹, J.F. Kamenik²⁶²,²⁶³, A. Kanso²⁶⁴, T. Kar²⁶⁵,
S.O. Kara²⁶⁶, H. Karadeniz²⁶⁷, B. Karmakar²⁶⁰, S.R. Karmarkar²⁷⁰, V. Karpati²⁶⁸, I. Karpov¹, M. Karppinen¹,
P. Karst⁹,⁷⁵,⁷⁶, S. Kartal³³, V.V. Kashikhin³⁷, U. Kaya⁵⁸, A. Kehagias¹,²⁶⁹, J. Keintzel¹, M. Kennouche¹,
M. Kenzie³², M. Kerréveur-Lavaud⁴⁶, R. Kersevan¹,²⁷⁰, V. Keus¹⁹⁸,²⁷¹, H. Khanpour¹⁴,²⁷²,²⁷³, V.V. Khoze²⁷⁴,
V.A. Khoze²⁷⁴, P. Kicsiny¹, R. Kieffer¹, C. Kiel¹¹⁴, J. Kieseler¹³², A. Kilic²⁷⁵, B. Kilminster⁷³, S. Kim²⁷⁶,
Z. Krca²⁷⁵, M. Klein¹⁸⁵, A. Klimentov⁶, M. Klute¹³², V. Klyukhin¹¹⁹,²⁷⁷, M. Knecht¹³⁷,²⁷⁸,²⁷⁹, B. Kniehl¹¹⁵,
P. Ko²⁸⁰, S. Ko¹, F. Kocak²⁷⁵, T. Koffas²⁸¹, C. Kokkinos²⁸²,²⁸³, K. Kołodziej²⁶⁰, K. Kong²⁸⁴, P. Kontaxakis¹⁰¹,
I.A. Koop¹¹⁹, P. Kopciewicz¹, P. Koppenburg²⁰², M. Koratzinos¹,², K. Kordas²⁸⁵, A. Korsun⁹,¹⁰,¹¹,
O. Kortner¹³¹, S. Kortner¹³¹, B. Korzh¹⁰¹, T. Koseki²¹², J. Kosse², P. Kostka¹,¹⁸⁵, S. Kostoglou¹, A.V. Kotwal⁸⁰,
G. Kozlov¹,²⁷⁷, I. Kozsar¹, T. Kramer¹, P. Krkotić¹, H. Kroha¹³¹, K. Kröninger²⁴⁵, S. Kuday¹,⁵⁸,
G. Kuhlmann²⁸⁶, O. Kuhlmann¹,²⁸⁷, M. Kuhn²⁸⁸, A. Kulesza²⁸⁹, M. Kumar²⁹⁰, F. Kurian⁶, A. Kurtulus¹,¹⁵⁰,
T.H. Kwok⁷³, S. La Mendola¹, M. Lackner⁹⁸,²⁹¹, T. Ładziński¹, D. Lafarge¹, P. Laïdouni¹, G. Lamanna⁹,¹⁶,¹⁷,
N. Lamas¹⁹, G. Landsberg²³³, C. Lange², D.J. Lange¹⁶³, A. Langner¹, A.J. Lankford²⁹², L. Lari⁶,
M.S. Larson²⁹³, K. Lasocha¹, A. Latina¹, S. Lauciani⁴⁸, M. Laufenberg¹⁰⁵, G. Lavezzari¹, L. Lavezzi⁶⁰,
L. Lavezzo¹, M. Le Garrec¹,⁹,¹⁶, A. Le Jeune¹⁰², P. Lebrun¹,²⁹⁴, Y. Léchevin¹, A. Lechner¹, E. Lecointe¹⁰⁵,
J.S.H. Lee²⁹⁵, S.W. Lee²⁹⁶, S.J. Lee²⁸⁰,²⁹⁷, T. Lefevre¹, C. Leggett¹⁴¹, T. Lehtinen²⁹⁸, S. Leone⁴⁰,
C. Leonidopoulos²⁹⁹, S. Leontsinis⁷³, G. Leprince-Maillère³⁰⁰, G. Lerner¹, O. Leroy⁹,⁷⁵,⁷⁶, T. Lesiak¹⁰⁷,
P. Levai⁷⁸, A. Leveratto⁹¹, R. Levi¹⁵², A. Li⁶, S. Li³⁰¹,³⁰², D. Liberati³⁰³, G.L. Lichtenstein⁴⁷, M. Liebe²⁴⁸,
Z. Ligeti¹⁴¹, H. Lin³⁰⁴, S. Linda¹⁴⁴, E. Lipeles³⁰⁵, Z. Liu³⁰⁶, S.M. Liuzzo³⁰⁷, T. Loeliger²⁸⁸,
A. Loeschcke Centeno³⁰⁸, A. Lorenzetti⁷³, C. Lorin³, R. Losito¹, M. Louka¹²,³⁰⁹, M.L. Loureiro García¹⁸¹,
I. Low¹²²,¹⁵⁸, K. Lubonis¹⁵², M.T. Lucchini³⁰,³¹, V. Lukashenko⁷³, G. Luminati⁴⁸, A.J.G. Lunt¹,³¹⁰,
A. Lusiani⁴⁰,³¹¹, M. Luzum³¹², H. Ma⁶, A. Maas³¹³, E. Macchia¹,⁹⁰,¹⁷⁰, A. Macchiolo⁷³, G.E. Machinet²⁶⁴,
R. Madar⁹,¹⁵⁴,¹⁵⁵, T. Madlener⁴, C. Madrid²³, A. Magalotti²⁹, M. Maggiora⁶⁰,²³⁵, A.-M. Magnan¹⁸²,
M.A. Mahmoud³¹⁴, Y. Mahmoud³¹⁵,³¹⁶, F. Mahmoudi¹,⁹,⁵⁶, H. Mainaud Durand¹, J. Maitre¹⁰⁸,
Y. Makhloufi¹⁰¹, B. Malescu⁹,¹¹⁷,³¹⁷, A. Malagoli⁹¹, C.H. Malan¹⁰⁸, M. Malekhosseini³⁸, A. Maloizel¹,⁹,⁶⁹,⁹⁷,
S. Malvezzi³⁰, A. Malzac¹⁴⁸, G. Manco¹²⁷, L.S. Mandacarú Guerra¹⁶³, P. Manfrinetti⁹¹,³¹⁸, E. Manoni⁶³,
J. Mans³⁰⁶, L. Mantani³¹⁹, S. Manzoni¹, L. Marafatto¹⁶⁷, C. Marcel¹, T. Marcel¹⁰⁹, R. Marchevski¹¹⁴,
G. Marchiori⁹,⁹⁶,⁹⁷, F. Mariani⁴⁴,⁹⁰, V. Mariani⁶³,⁶⁴, S. Marin¹, C. Marinas³¹⁹, V. Marinozzi³⁷, S. Mariotto⁴⁴,⁴⁵,
C. Marquis¹⁰⁵, J. Martelain³²⁰, G. Martelli⁶³,⁶⁴, A. Martens⁹,¹⁰,¹¹, I. Martin-Melero¹,
V.I. Martinez Outschoorn¹⁶⁹, F. Martinez²¹⁷, C.M. Jardim²⁷, L. Marzola³²¹,³²², S. Masciocchi²⁵⁹,²⁶⁵,
A. Mashal¹⁴, A. Masi¹, I. Masina¹⁴⁶,¹⁴⁷, P. Mastrapasqua²⁰¹, V. Mateu³²³, S. Mattiazzo⁶⁸,¹⁶⁴, M. Maugis¹⁰²,
V. Maura²¹⁰, D. Mauree¹⁴⁴, G.H.I. Maury-Cuna³²⁴, A. Mayoux¹, E. Mazzeo¹, S. Mazzoni¹, M. McCullough¹,
M. Meena⁹,⁴²,⁴³, E. Meftah¹⁰¹, Andrew Mehta¹⁸⁵, Ankita Mehta¹, B. Mele¹⁷⁰, R. Mena-Andrade¹, M. Mentink¹,
D. Mergelkuhl¹, V. Mertinger²⁶⁸, L. Mether¹, S. Meylan¹⁰⁵, T. Michel¹⁰², T. Michlmayr², M. Migliorati⁹⁰,¹⁷⁰
A. Milanese¹, C. Milardi⁴⁸, G. Milhano⁵¹, M. Minty⁶, C. Mirabelli³²⁵, T. Miralles⁹,¹⁵⁴,¹⁵⁵, L. Miralles Verge¹,
D. Mirarchi¹, K. Mirbaghestan⁷³, N. Mirian⁴,³²⁶, V.A. Mitsou³¹⁹, D.S. Mitzel²⁴⁵, M. Mlynarikova¹, S. Möbius⁸⁹,
M. Mohammadi Najafabadi¹,¹⁴, G.B. Mohanty³²⁷, R.N. Mohapatra²¹¹, S. Moneta⁶³, P.F. Monni¹,
E. Monnier⁹,⁷⁵,⁷⁶, S. Monteil⁹,¹⁵⁴,¹⁵⁵, I. León Monzón²⁰⁴, F. Moortgat¹,³²⁸, N. Morange⁹,¹⁰,¹¹, M. Moretti¹⁴⁶,¹⁴⁷,
S. Moretti⁷¹, T. Mori¹,²¹², I. Morozov¹¹⁹, A. Morozzi⁶³, M. Morrone¹, A. Moscariello¹⁰¹, F. Moscatelli⁶³,³²⁹,
I. Moulin²¹⁶, N. Mounet¹, A. Mueller³³⁰, A.-S. Müller¹³², B.O. Müller²⁸⁶, J. Mundet²²², E. Musa¹,⁴
V. Musat¹,⁸, R. Musenich¹⁴⁰, E. Musumeci³¹⁹, M. Mylona¹, V.V. Mytrochenko⁹,¹⁰,¹³³, B. Nachman¹⁴¹,
S. Nagaitsev⁶, T. Nakamoto²¹², M. Napsuciale³²⁴, M. Nardecchia⁹⁰,¹⁷⁰, G. Nardini³³¹, G. Narváez-Arango³³²,
S. Naseem⁶¹, A. Natochii⁶, A. Navascues Cornago¹, B. Naydenov¹, G. Nergiz¹, A.V. Nesterenko²⁷⁷,
C. Neubüser³³³, H.B. Newman³³⁴, F. Niccoli¹,³³⁵, O. Nicrosini¹²⁷, U. Niedermayer²²⁸, G. Niehues¹³², J. Nielsen¹,
G. Nigrelli¹,⁹⁰,¹⁷⁰, S. Nikitin¹¹⁹, I.B. Nikolaev¹¹⁹, A. Nisati¹⁷⁰, N. Nitika¹⁶⁷,¹⁶⁸, J.M. No³³⁶, M. Nonis¹,
Y. Nosochkov⁷, A. Novokhatski¹,⁷, J.M. O’Callaghan³³⁷, S.A. Ochoa-Oregon²⁰⁴, K. Ohmi²⁰³,²¹², K. Oide¹,¹⁰¹,²¹²,
V.A. Okorokov¹¹⁹, C. Oleari³⁰,³¹, D. Oliveira Damazio¹,⁶, Y. Onel¹¹², A. Onofre³³⁸,³³⁹,³⁴⁰, P. Osland³⁴¹,
Y.M. Oviedo-Torres³⁴²,³⁴³,³⁴⁴, A. Ozansoy⁵⁸, F. Ozaydin⁸⁷,³⁴⁵, K. Ozdemir³⁴⁶, A. Ozturk¹,
M.A. Pérez de León²⁰⁴, S. Pacetti⁶³,⁶⁴, H. Pacey⁸, J. Paciello¹⁰⁸, C.E. Pagliarone³⁴⁷,³⁴⁸, A. Paillex¹⁰⁵,
H.F. Pais da Silva¹, F. Palla⁴⁰, A. Pampaloni¹⁴⁰, C. Pancotti¹⁴⁹, M. Pandurović³⁴⁹, O. Panella⁶³,
G. Panizzo¹⁶⁷,¹⁶⁸, C. Pantouvakis⁶⁸,¹⁶⁴, L. Panwar⁹,¹¹⁷,³¹⁷, P. Paolucci³⁵, Y. Papa¹⁰⁵, A. Papaefstathiou³⁵⁰,
Y. Papaphilippou¹, A. Paramonov¹⁵⁸, A. Pareti¹²⁷,³⁵¹, B. Parker⁶, V. Parma¹, F. Parodi¹⁴⁰,³¹⁸, M. Parodi¹,
B. Paroli⁴⁴,⁴⁵, J.A. Parsons³⁵², D. Passarelli³⁷, D. Passeri⁶³,⁶⁴, B. Pattnaik³¹⁹, A. Patwa³⁵³, C. Paus¹⁸³,
F. Pauss¹⁵⁰, F. Peauger¹, I. Pedraza²¹⁷, R. Pedro⁵¹, J. Pekkanen¹, G. Peon¹, A. Perez¹⁰⁹, E. Perez¹, F. Pérez¹⁷¹,
J.C. Perez¹, J.M. Pérez²⁷, R. Perez-Ramos¹³⁷,¹³⁸,³⁵⁴, G. Pérez Segurana¹, A. Perillo Marcone¹, S. Perna³⁵,³⁶,
K. Peters⁴, S. Petracca³⁵,³⁵⁵, A.R. Petri⁴⁴, F. Petriello¹²², A. Petrovic¹, L. Pezzotti²⁵, G. Piacquadio⁶²,
G. Piazza¹⁸⁰, A. Piccini¹, F. Piccinini¹²⁷, A. Pich³¹⁹, T. Pieloni¹¹⁴, J. Pierlot¹, A.D. Pilkington⁵², M. Pillet³²⁵,
M. Pinamonti¹⁶⁷,¹⁶⁸, N. Pinto²³⁶, L. Pintucci¹⁶⁷,¹⁶⁸, F. Pinzauti¹, K. Piotrzkowski²⁷², C. Pira⁴⁸, M. Pitt¹,
R. Pittau¹⁹¹, S. Pittet¹, P. Placidi⁶³,⁶⁴, W. Płaczek³⁵⁶, S. Plätzer³¹³,³⁵⁷, M.-A. Pleier⁶, E. Ploerer⁷³,¹¹⁶,
H. Podlech³⁵⁸,³⁵⁹, F. Poirier⁹,¹⁶,¹⁷, G. Polesello¹²⁷, M. Poli Lener⁴⁸, J. Polinski¹⁶¹, Z. Polonsky⁷³, N. Pompeo²⁹,
M. Pont¹⁷¹, G. Alexandru-Popeneciu³⁶⁰, W. Porod¹⁹⁶, L. Porta¹, L. Portales³, T. Portaluri³⁰⁸, M.A.C. Potenza⁴⁵, C. Prasse²⁸⁶, E. Premat¹⁸⁴, M. Presilla¹³², S. Prestemon¹⁴¹, A. Price³⁵⁶, M. Primavera¹⁵⁹, R. Principe¹, M. Prioli⁴⁴, F.M. Procacci¹², E. Proserpio⁴⁴,¹³⁴, A. Provino⁹¹,³¹⁸, C. Pueyo¹, T. Puig¹⁹, N. Pukhaeva²⁷⁷, S. Pulawski²⁰⁶, G. Punzi⁴⁰,⁷⁷, A. Pyarelal³⁶¹, J. Qian³⁰⁴, H. Quack³⁶², F.S. Queiroz⁴⁷, G. Quintas-Neves³⁰⁰, H. Rafique⁷¹, J.-Y. Raguin², J. Raidal³²¹, M. Raidal³²¹, P. Raimondi³⁷, A. Rajabi⁴, S. Ramírez-Uribe²⁰⁴, S. Randles¹⁸⁵, T. Rao⁶, C.Ø. Rasmussen⁶, A. Ratkus³⁶³, P.N. Ratoff⁵³,³⁶⁴, P. Razis³⁶⁵,³⁶⁶, P. Rebello Teles¹,³⁶⁷, M.N. Rebelo¹²⁹, M. Reboud⁹,¹⁰,¹¹, S. Redaelli¹, C. Regazzoni¹⁰⁵, L. Reichenbach¹,³⁶⁸, M. Reissig¹³², E. Renou¹⁰⁵, A. Rentería-Olivo³¹⁹, J. Reuter⁴, S. Rey¹⁰⁵, A. Ribon¹, D. Ricci¹, W. Riegler¹, M. Rignanese⁶⁸,¹⁶⁴, S. Rimjaem³⁶⁹, R.A. Rimmer³⁷⁰, R. Rinaldesi¹, L. Rinolfi¹,²⁹⁴, O. Rios¹, G. Ripellino¹³⁰, B. Rivas³⁷¹, A. Rivetti⁶⁰, T. Robens³⁷², F. Robert¹⁸⁴, E. Robutti¹⁴⁰, C. Roderick¹, G. Rodrigo³¹⁹, M. Rodríguez-Cahuantzi²¹⁷, L. Röhrig¹⁵⁴,¹⁵⁵,²⁴⁵, M. Roig³⁷³, F. Rojat¹⁰⁸, J. Rojo²⁰²,³⁷⁴, J. Roloff²³³, P. Roloff¹, A. Romanenko³⁷, A. Romero Francia¹, H. Romeyer³⁷⁵, N. Rompotis¹⁸⁵, N. Rongieras¹⁰², G. Rosaz¹, K. Roslon³⁷⁶, M. Rossetti Conti⁴⁴, A. Rossi⁶³,⁶⁴, E. Rossi³⁵,³⁶, L. Rossi⁴⁴,⁴⁵, A.N. Rossia⁶⁸,¹⁶⁴, S. Rostami³⁸, G. Roy¹, B. Rubik³⁷, I. Ruehl¹, A. Ruiz-Jimeno³⁷⁷, R. Ruprecht¹³², J.P. Rutherford³⁶¹, L. Rygaard⁴, M.S. Ryu²⁹⁶, L. Sabato¹,¹¹⁴, G. Sadowski⁹,⁴²,⁴³, D. Saez de Jauregui¹³²,³⁷⁸, M. Sahin³⁷⁹, A. Sailer¹, M. Saito³⁸⁰, P. Saiz¹, G.P. Salam³⁸¹,³⁸², R. Salerno⁹,⁸¹,⁸², T. Salmi²⁹⁸, B. Salvachua¹, J.P.T. Salvesen¹,⁸,¹³⁶, B. Salvi³⁰⁰, D. Sampsonidis²⁸⁵, Y. Villamizar¹³⁷,¹³⁸,¹³⁹, C. Sandoval³³², S. Sanfilippo², E. Santopinto¹⁴⁰, R. Santoro⁴⁴,¹³⁴, X. Sarasola¹¹⁴, L. Sarperi²⁸⁸, I.H. Sarpün³⁸³, S. Sasikumar¹, M. Sauvain³⁸⁴, A. Savoy-Navarro³,⁹, R. Sawada³⁸⁰, G. Sborlini³⁸⁵, J. Scamardella³⁵,³⁶, M. Schaer², M. Schaumann¹,⁴, M. Schenk¹, C. Scheuerlein¹, C. Schiavi¹⁴⁰,³¹⁸, A. Schloegelhofer¹, D. Schoerling¹, A. Schöning²⁶⁵, S. Schramm¹⁰¹, D. Schulte¹, P. Schwaller²⁵²,³⁸⁶, A. Schwartzman⁷, P. Schwemling³, R. Schwienhorst³⁸⁷, A. Sciandra⁶, L. Scibile¹, I. Scimemi³⁸⁸, E. Scomparin⁶⁰, C. Sebastiani¹, B. Seeber³⁸⁹, J.T. Seeman⁷, F. Sefkow⁴, M. Seidel²,¹¹⁴, S. Seidel⁷⁴, J. Seixas³⁴⁰,³⁹⁰,³⁹¹, N. Selimović⁶⁸, M. Selvaggi¹, C. Senatore¹⁰¹, A. Senol¹⁹⁵, N. Serra⁷³, A. Seryi³⁷⁰, A. Sfyrla¹⁰¹, Pramond Sharma³⁹², Punit Sharma⁶, C.J. Sharp¹, L. Shchutska¹¹⁴, V. Shiltsev³⁹³, M. Siano⁴⁴,⁴⁵, R. Sierra¹, E. Silva²⁹, R.C. Silva⁴⁷,³⁴⁴, L. Silvestrini¹⁷⁰, F. Simon¹³², G. Simonetti¹, R. Simoniello¹, B.K. Singh³⁹⁴, S. Singh⁶, B. Singhal⁷⁹, A. Siodmok¹,³⁵⁶, Y. Sirois⁹,⁸¹,⁸², E. Sirtori¹⁴⁹, B. Sitar³⁹⁵, D. Sittard¹, E. Sitti¹⁵⁰, T. Sjöstrand⁵⁹, P. Skands³⁹⁶, L. Skinnari²⁹³, K. Skoufaris¹, K. Skovpen³²⁸, M. Skrzypek¹⁰⁷, P. Slavich¹³⁷,¹³⁸,¹³⁹, V. Slokenbers²³, V. Smaluk⁶, J. Smiesko¹,³⁹⁷, S.S. Snyder⁶, E. Solano¹⁷¹, P. 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Tomasini¹⁴⁰, G. Tonelli⁴⁰,⁷⁷, T. Tong⁴¹¹, F. Toral²⁷, T. Torims¹,³⁶³, L. Torino¹⁷¹, K. Torokhtii²⁹, R. Torre¹⁴⁰, E. Torrence⁴¹², R. Torres⁵³,¹⁸⁵, T. Mitsuhashi²¹², A. Tracogna¹⁴⁹, O. Traver¹⁷¹, D. Treille¹, A. Tricoli⁶, P. Trubacova¹, E. Tsesmelis¹, G. Tsipolitis²⁶⁹, V. Tsulaia¹⁴¹, B. Tuchming³, C.G. Tully¹⁶³, I. Turk Cakir⁵⁸, C. Turrioni⁶³, J. Tynan¹⁰⁵, F.P. Ucci¹²⁷,³⁵¹, S. Udongwo⁴¹³, C.S. Ün²⁷⁵, A. Unnervik¹, A. Upegui⁹⁹,¹⁰⁰, J.P. Uribe-Ramírez²⁰⁴, J. Uythoven¹, R. Vaglio³⁶,⁹¹, F. Valchkova-Georgieva⁴¹⁴, P. Valente¹⁷⁰, R.U. Valente¹⁷⁰, A.-M. Valente-Feliciano³⁷⁰, G. Valentino¹,¹⁹³, C.A. Valerio-Lizarraga²⁰⁴,³²⁴, S. Valette¹, J.W.F. Valle³¹⁹, L. Valle¹, N. Valle¹²⁷, N. Vallis¹,²,¹¹⁴, G. Vallone¹⁴¹, P. van Gemmeren¹⁵⁸, W. Van Goethem¹, P. van Hees⁵⁹, U. van Rienen⁴¹³, L. van Riesen-Haupt¹,¹¹⁴, P. Van Trappen¹, M. Vande Voorde⁴¹⁵,⁴¹⁶, A.L. Vanel¹, E.W. Varnes³⁶¹, J.-L. Vay¹⁴¹, F. Veit²⁸⁶, I. Veliscek⁶, R. Veness¹, A. Ventura¹⁵⁹,²³², S. Verdú-Andrés⁶, M. Verducci⁴⁰,⁷⁷, C.B. Verhaaren⁴¹⁷, C. Vernieri⁷, A.P. Verweij¹, J.-F. Vian⁴¹⁸, A. Vicini⁴⁴,⁴⁵, N. Vignaroli¹⁵⁹,²³², S. Vignetti¹⁴⁹, M.C. Villeneuve²²⁰, I. Vivarelli²⁵,²⁶, E. Voevodina¹,¹³¹, D.M. Vogt¹⁴⁹, B. Voirin⁴²⁰, S. Voiriot¹⁰⁵, J. Voiron¹⁴⁴, P. Vojtyla¹, V. Vökl¹, L. von Freeden¹, Z. Vostrel¹,⁴²¹, N. Voumard¹, E. Vryonidou⁵², V. Vysotsky¹¹⁹, R. Wallny¹⁵⁰, L.-T. Wang⁴²², Y. Wang⁹,¹⁰,¹¹, R. Wanzenberg⁴, B.F.L. Ward⁴²³, N. Wardle¹⁸², Z. Was¹⁰⁷, L. Watrelot¹, A.T. Watson⁴²⁴, M.F. Watson⁴²⁴, M.S. Weber⁸⁹, C.P. Welsch⁵³,¹⁸⁵, M. Wendt¹,⁶, J. Wenninger¹, B. Weyer¹, G. White⁴²⁵, S. White³⁰⁷, B. Wicki¹, M. Widorski¹, U.A. Wiedemann¹, A.R. Wiederhold⁵², A. Wiedl¹³², H.-U. Wienands¹⁵⁸, A. Wieser¹⁵⁰, C. Wiesner¹, H. Wilkens¹, D. Willi⁴²⁶, P.H. Williams⁵³,⁴²⁷, S.L. Williams³², A. Winter⁴²⁴, R.B. Wittwer⁷³, D. Wollmann¹, Y. Wu¹¹⁴, Z. Wu⁹,¹⁶,¹⁷, J. Xiao⁹,⁵⁶,⁵⁷, K. Xie³⁸⁷, S. Xie³⁷,³³⁴, M. Yalvac²², F. Yaman⁴²⁷,⁴²⁸, W.-M. Yao¹⁴¹, M. Yeresko⁹,¹⁵⁴,¹⁵⁵, A. Yilmaz¹⁹⁵, H.D. Yoo²⁷⁶, T. You²¹⁰, F. Yu²⁵²,³⁸⁶, S.S. Yu⁷⁹, T.-T. Yu⁴¹², S. Yue¹, A. Zaborowska¹, M. Zahnd¹⁰⁵, C. Zamantzas¹, G. Zanderighi⁶⁵,¹³¹, C. Zannini¹, R. Zanzottera⁴⁴,⁴⁵, P. Zaro¹⁰², R. Zennaro², M. Zerlauth¹, H. Zhang²⁰³, J. Zhang¹⁵⁸, Y. Zhang²⁰³, Z. Zhang⁹,¹⁰,²⁰³, Y. Zhao¹, Y.-M. Zhong⁴²⁹, B. Zhou³⁰⁴, D. Zhou²¹², J. Zhu³⁰⁴, G. Zick³⁷³, M.A. Zielinski¹, E. Zimmermann¹⁰⁵, A. Zingaretti⁶⁸,¹⁶⁴, J. Zinn-Justin³, A.V. Zlobin³⁷, M. Zobov⁴⁸, F. Zomer⁹,¹⁰,¹¹, S. Zorzetti³⁷, X. Zuo¹³², J. Zurita³¹⁹, V.V. Zutshi³⁹³, and M. Zykova²
Received: 18 June 2025 / Accepted: 10 September 2025 / Published online: 13 October 2025
© The Author(s) 2025, corrected publication 2025

**Abstract** Volume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to support the development of an improved 3D subsurface model of the region. The report describes the development of the project scenario based on the ‘avoid-reduce-compensate’ iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain—including numerous urban, economic, social, and technical aspects—confirmed the project’s technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a summary of the studies conducted to document the current state of the environment.

*Note from the Editors* One of the recommendations of the 2020 update of the European Strategy for Particle Physics was that “Europe, together with its international partners, should investigate the technical and financial feasibility of a future hadron collider at CERN with a centre-of-mass energy of at least 100 TeV and with an electron-positron Higgs and electroweak factory as a possible first stage.”

In June 2021, the CERN Council launched the FCC Feasibility Study to be completed by 2025, in time for the next update of the European Strategy for Particle Physics. The study results are made publicly available through this FCC Feasibility Study Report, as input to the European Particle Physics Strategy update process, initiated by the CERN Council in March 2024. The studies presented in this FCC Feasibility Study Report do not imply any commitment by the CERN Member or Associate Member States to build the Future Circular Collider.

This report and the assumptions contained in it do not prejudice further territorial feasibility analysis by the Host States, France and Switzerland, as well as the outcome of their respective public debate and concertation processes, and future decisions of their relevant authorities.

*Acknowledgements* We would like to thank the **International Steering Committee** members:

F. Gianotti (Chair), CERN

R. Bello, CERN

P. Chomaz, CEA, France

M. Cobal, INFN and University of Udine, Italy

B. Heinemann, DESY, Germany

T. Koseki, KEK, Japan

M. Lamont, CERN

L. Merminga, FNAL, United States

J. Mnich, CERN

M. Seidel, PSI and EPFL, Switzerland

C. Warakaulle, CERN

and the **Scientific Advisory Committee** members:

A. Parker (Chair), Cambridge University, UK

R. Bartolini, DESY, Germany

A. Chabert, SFTRF, France

H. Ehrbar, Heinz Ehrbar Partners LLC, Switzerland

B. Gavela Legazpi, UAM Madrid, Spain

G. Hiller, TU Dortmund, Germany

S. Krishnagopal, FNAL, U.S.

P. Križan, University of Ljubljana, Slovenia

P. Lebrun, ESI, France

P. McIntosh, STFC, ASTEC, UKRI, UK

M. Minty, BNL, U.S.

R. Tenchini, INFN Sezione di Pisa, Italy

for their continued guidance and careful reviewing that helped to complete this report successfully.
<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

The research carried out by the international FCC collaboration hosted by CERN, which led to this publication, has received funding from the European Union’s Horizon 2020 research and innovation programme under the grant numbers 951754 (FCCIS), 654305 (EuroCirCol), 764879 (EASITrain), 730871 (ARIES), 777563 (RI-Paths), 101086276 (EAJADE), 101004730 (iFAST), 101131435 (iSAS), 101131850 (RF2.0) and from FP7 under grant number 312453 (EuCARD-2)

This work has also benefited from the support of CHART (Swiss Accelerator Research and Technology), founded in 2016 as an umbrella collaboration for accelerator research and technology activities. Present partners in CHART are CERN, PSI, EPFL, ETH-Zurich and the University of Geneva.

*Image Sources and Credits* The FCC Project formally acknowledges and credits all organisations and contributors whose data and imagery form part of the basemaps used in this work. These include © Esri, Airbus DS, FAO, FEMA, GSA, NASA, NGA, NOAA, USGS, CGIAR, NCEAS, Rijkswaterstaat, SITG – State of Geneva (CH), swisstopo, Facebook, Garmin, Geoland, Geodatastyrelsen, Google, Intermap, Maxar, Microsoft, N Robinson, NLS, NMA, OS, Planet, TomTom, as well as © OpenStreetMap contributors, Esri Community Maps contributors, and the GIS User Community.

Every effort has been made to correctly acknowledge all data providers and rights holders. Any omission is unintentional, and the FCC Project remains available to review and amend credits upon request from legitimate data owners.

## Preface from CERN's Director-General

In 2021, in response to the 2020 update of the European Strategy for Particle Physics, the CERN Council initiated the Future Circular Collider (FCC) Feasibility Study.

This report summarises an immense amount of work carried out by the international FCC collaboration over several years. It covers, inter alia, physics objectives and potential, geology, civil engineering, technical infrastructure, territorial implementation, environmental aspects, R&D needs for the accelerators and detectors, socio-economic benefits and cost. It constitutes important input for the ongoing update of the European Strategy for Particle Physics.

The Feasibility Study required engagement with a broad range of stakeholders. In particular, throughout the Study, CERN has been accompanied by its two Host States, France and Switzerland, and has been working with entities at local, regional and national level. I am very grateful to the Host State authorities and teams for their invaluable help. Furthermore, significant sections of the Study were supported by the European Union under the Horizon 2020 and Horizon Europe framework programmes. The Study also greatly benefited from contributions from accelerator laboratories and universities from across Europe, such as the Swiss Accelerator Research and Technology (CHART) initiative, and from the Americas, Asia, Africa and Australia.

The proposed FCC integrated programme consists of two possible stages: an electron-positron collider serving as a Higgs-boson, electroweak and top-quark factory running at different centre-of-mass energies, followed at a later stage by a proton-proton collider operating at an unprecedented collision energy of around 100 TeV. The complementary physics programmes of each stage match the physics priorities expressed in the 2020 update of the European Strategy for Particle Physics.

A major achievement of the Feasibility Study is the choice of placement of the collider ring and the entire infrastructure, including the surface sites and the access shafts, which was developed and optimised over several years following the principle 'avoid, reduce, compensate'. Sustainability studies have assessed energy efficiency, land use, water and resource management, and socio-economic impact, ensuring that the FCC is designed in accordance with the latest environmental and societal standards.

I would like to thank all contributors to this report for their hard work and commitment, which allowed the outstanding results presented here to be achieved.

Fabiola Gianotti

CERN, Director-General

## Preface from the FCC Collaboration Board Chair

Building on the earlier Future Circular Collider (FCC) Conceptual Design Study conducted between 2014 and 2018, the FCC Feasibility Study (2021–2025) has been undertaken by a robust international collaboration, now comprising over 160 institutes worldwide. The FCC ‘integrated programme’, developed in the framework of the Feasibility Study, consists of an initial electron-positron collider, the FCC-ee, which could be followed by a proton-proton collider, the FCC-hh. This staging takes into account the physics priorities as formulated in the updates of the European Strategy for Particle Physics of 2012 and 2020, as well as the relative technology readiness and costs of the FCC-ee and FCC-hh.
Over the years, I have closely followed the steady progress of the study, representing the FCC collaboration at the international steering committee and participating in annual FCC Week meetings, which include sessions of the International Collaboration Board. The commitment and enthusiasm of the members of the collaboration has always been impressive. The collective effort is clearly visible. Participation by students and early-career researchers is increasing. There is a shared determination and momentum to move forward.

The strong international collaboration around the FCC and its global network provides a solid foundation for the future of this project. The FCC community continues to grow, with increasing engagement from new institutes and partners worldwide. This broad support will be essential as the project enters its next phase.

The FCC Feasibility Study demonstrates not only the technical viability of the project, but also the strength of the international community that supports it. As we move towards the next step in the decision-making phase, this collective effort is key to showing a possible path forward. The FCC promises far-reaching scientific opportunities and long-term benefits for innovation, training, and global collaboration in science and technology.

Philippe Chomaz

CEA, Chair of the FCC International Collaboration Board

## Contents

<table><tr><td>1</td><td>Civil engineering</td><td>5119</td></tr><tr><td>1.1</td><td>Introduction</td><td>5119</td></tr><tr><td>1.2</td><td>Underground structures</td><td>5120</td></tr><tr><td>1.3</td><td>Surface structures</td><td>5136</td></tr><tr><td>1.4</td><td>Staged approach</td><td>5149</td></tr><tr><td>1.5</td><td>Subsurface site investigations</td><td>5151</td></tr><tr><td>1.6</td><td>Management of excavated materials</td><td>5163</td></tr><tr><td>2</td><td>Territorial implementation</td><td>5173</td></tr><tr><td>2.1</td><td>Introduction</td><td>5173</td></tr><tr><td>2.2</td><td>Methodology to develop a sustainable project</td><td>5174</td></tr><tr><td>2.3</td><td>Requirements and invariants</td><td>5182</td></tr><tr><td>2.4</td><td>Territorial constraints</td><td>5189</td></tr><tr><td>2.5</td><td>Initial variants</td><td>5196</td></tr><tr><td>2.6</td><td>Reference scenario</td><td>5200</td></tr><tr><td>2.7</td><td>Territorial infrastructure needs</td><td>5220</td></tr><tr><td>3</td><td>Environment</td><td>5247</td></tr><tr><td>3.1</td><td>Context</td><td>5247</td></tr><tr><td>3.2</td><td>Environmental aspects</td><td>5251</td></tr><tr><td>3.3</td><td>Current state of the environment</td><td>5278</td></tr><tr><td>3.4</td><td>Conclusion</td><td>5324</td></tr><tr><td>4</td><td>Sustainability</td><td>5325</td></tr><tr><td>4.1</td><td>Context</td><td>5325</td></tr><tr><td>4.2</td><td>Introduction</td><td>5326</td></tr><tr><td>4.3</td><td>Methodology</td><td>5332</td></tr><tr><td>4.4</td><td>Socio-economic sustainability enablers</td><td>5333</td></tr><tr><td>4.5</td><td>Comprehensive sustainability performance assessment based on Cost-Benefit Analysis</td><td>5338</td></tr><tr><td>4.6</td><td>Limitations</td><td>5339</td></tr><tr><td>4.7</td><td>Lifecycle analysis</td><td>5341</td></tr><tr><td>4.8</td><td>Socio-economic performance</td><td>5345</td></tr><tr><td>4.9</td><td>Returns to participating countries</td><td>5361</td></tr><tr><td>4.10</td><td>Requirements and constraints for a preparatory phase</td><td>5364</td></tr><tr><td>4.11</td><td>Recommendations for a preparatory phase project</td><td>5364</td></tr><tr><td></td><td>References</td><td>5366</td></tr></table>

# Chapter 1

## Civil engineering

### 1.1 Introduction

Since the completion of the FCC conceptual design in 2018, several significant modifications have been made to civil engineering. They derive from the improved maturity of requirements for the systems that interface with
civil engineering, such as the accelerators, the detectors, and the technical infrastructure to be housed within the underground and surface structures. Furthermore, more precise localisation of the surface sites has facilitated a greater understanding of the geographical and environmental constraints to be accounted for in the development of the civil engineering infrastructure. The main improvements that have occurred since the conceptual design of the underground civil engineering required for the FCC-ee collider was completed are as follows:

* A reduction in the overall circumference of the accelerator tunnel from 97.8 km to 90.6 km.

* A reduction in the number of surface sites (and access points to the underground) from 12 to 8.

* A reduction in the number of permanent shafts needed for operation from 18 to 12.

* A reduction of the depth to the deepest shaft from 578 m to 400 m.

* Additional underground civil engineering for the RF systems at technical sites PH and PL.

* A simplification of the civil engineering needed for the beam absorber system.

* Simplification of the underground infrastructure required for the beam transfer lines, with the use of a single tunnel to house both clockwise and anti-clockwise transfer to the FCC.

In addition to the above, a more detailed—yet still evolving—understanding of the requirements for surface civil engineering has been built up. Initial spatial arrangements for all eight surface sites have been developed, with preliminary dimensioning of the necessary buildings, roads, and other surface infrastructure providing a framework for further refinement. For two of the eight sites, and under a collaboration with the U.S. Fermi National Accelerator Laboratory, preliminary design studies for buildings have been carried out. The results offer valuable insights into space requirements, user access needs and cost envelopes. They were mainly informed by the technical needs of the interfacing systems. The integration of the ‘Avoid, Reduce, Compensate’ approach to develop the surface sites is an iterative process, requiring continued efforts to understand the technical needs, the territorial requirements and constraints and the project cost and risk implications. Understanding the technical system requirements is an essential guiding element. The analysis of the current state of the environment also carried out in the frame of the feasibility study, is another aspect that will inform the subsequent activities.

A staged approach to civil engineering has been studied. Infrastructure essential for the operation of the FCC-ee collider and its associated experiments is included within the initial stage, along with any civil engineering needed for FCC-hh for which it would be impossible, impractical, or inefficient to construct during a second stage. This staged approach primarily concerns the surface infrastructure since it is relatively straightforward to construct additional buildings in a second stage.

The civil engineering for the FCC-ee, as defined in this document, builds on the studies completed for the conceptual design phase and carried out for the feasibility phase. The current design demonstrates the technical feasibility of FCC civil engineering. It is to be noted, however, that there are still areas where further work needs to be done in order to reduce technical risks, in particular taking into account the remaining data that will be provided upon completion of phase 1 of the sub-surface site investigations that commenced in October 2024 and is expected to be completed before the end of 2025.

The work carried out since the completion of the conceptual design has largely maintained similar spatial elements for the underground works (sizes of caverns, shafts, tunnels, etc.), and therefore, it has not been necessary to undertake additional calculations for the overall structural stability of these elements. Furthermore, the construction methodologies remain largely as identified during the conceptual design phase, although the sequence for undertaking the works has now been revised, in particular, to account for the reduced number of access points to the underground civil engineering.

A key input to the feasibility study has come from the early interaction between the FCC civil engineering team and potential future stakeholders from the industry. CERN has held a number of meetings and workshops with several major contractors specialising in underground civil engineering. The feedback received has proved invaluable in developing not only robust technical solutions but also a realistic and efficient schedule for the execution of civil engineering. Feedback from the industry has also helped shape CERN’s initial thinking on potential contractual routes for the delivery of the design and construction of civil engineering. The civil engineering schedule developed as part of the feasibility study has been integrated with the subsequent infrastructure and machine installation activities. The resulting integrated schedule results in a gradual handover of the civil engineering for each of the eight sectors, thus allowing parallel and more efficient execution of installation activities in the main tunnel.

## 1.2 Underground structures

Several improvements have been made to the underground structures since the conceptual design report was completed. A thorough identification has been made of the underground structures necessary for the FCC-ee collider as well as those for the FCC-hh collider, which cannot be deferred. The latter will be constructed as part of the civil engineering necessary for the FCC-ee collider and associated experiments.

A Product Breakdown Structure (PBS) has been produced down to level 4, containing 205 uniquely identified structures. Table 1.1 lists the PBS and associated structures for the sector PA to PB. The PBS of other sectors
<table><caption>**Table 1.1** PBS for sector PA to PB underground structures</caption><thead><tr><th>PBS Level</th><th> PBS Description</th></tr></thead><tbody><tr><td>0</td><td>Civil engineering</td></tr><tr><td>1</td><td>Underground structures</td></tr><tr><td>2</td><td>Site PA</td></tr><tr><td>2</td><td>Experiment shaft</td></tr><tr><td>2</td><td>Service shaft</td></tr><tr><td>2</td><td>Experiment cavern</td></tr><tr><td>2</td><td>Service cavern</td></tr><tr><td>2</td><td>Alcoves</td></tr><tr><td>2</td><td>Beam tunnel sector AB</td></tr><tr><td>2</td><td>Bypass tunnel AL</td></tr><tr><td>2</td><td>Bypass tunnel AB</td></tr><tr><td>2</td><td>Connection tunnels and galleries</td></tr><tr><td>2</td><td>Tunnel widenings</td></tr></tbody></table>

<figure><img src="image_6.png" /><figcaption>**Fig. 1.1** Schematic layout of FCC-ee underground civil engineering</figcaption></figure>

follow a similar structure. In total, the underground civil works consist of twelve permanent shafts for operation, one temporary shaft required only during the civil engineering construction, twelve large caverns with spans exceeding 20 m as well as numerous smaller caverns, alcoves, connection and bypass tunnels that collectively make up the underground civil engineering. Figure 1.1 shows a schematic arrangement of underground civil engineering.

The overall circumference of the accelerator tunnel that will house the colliders is 90.6 km, a reduction of about 7% compared to the 97.8 km tunnel developed at the conceptual design phase. The accelerator tunnel, which will house the collider, has an internal nominal diameter of 5.5 m. On the basis of the pre-existing and recent site investigation data, the average elevation is 300 m above datum and the inclination of the tunnel plane has been maintained at 0.1% and 0.4% in the two axes. This results in a tunnel depth that varies between 30 m where the
tunnel passes under the Rhône river and 560 m where the tunnel passes under the Borne plateau on the eastern side of the overall study site. The average depth of the tunnel is approximately 240 m below the ground surface.

Two sizes of experiment cavern complexes are envisaged; these are similar in layout and function. The first type includes a cavern to house the largest planned FCC-hh detector with a 35 m span (similar to that of the existing ATLAS detector cavern) and the second type includes a cavern to house the smaller FCC-hh detectors with a span of 25 m (similar to that of the existing CMS detector cavern).

A single transfer tunnel connecting the injection system to the FCC is envisaged. This tunnel starts close to the surface of the existing CERN Prévessin site where it will connect to the cut and cover tunnel that will house the high-energy LINAC. The tunnel will descend over a distance of about 5 km at which point it will bifurcate at a location close to PA to allow symmetrical clockwise and anticlockwise injection into the FCC. The injection will take place on either side of the experiment area located in PA.

Expectations regarding the geology to be encountered during the civil engineering of the underground structures are consistent with those established during the conceptual design phase of the FCC-ee study, providing a solid foundation for further refinement and risk mitigation in subsequent phases. The current expectation is that the majority of the tunnels and the cavern complexes will be located within the molasse rock, a low to medium-strength sedimentary rock made up of complex sequences of marls and sandstones. This material is well suited for tunnelling since it is typically watertight and can be supported through the implementation of a range of standard rock support measures such as rock bolts, shotcrete, reinforced concrete segments etc. Larger caverns can become more challenging and will require more complex methods for the excavation and support of the rock mass. This is further detailed in Sect. 1.2.5.

The accelerator tunnel will pass through approximately 4.4 km of limestone rock. Whilst it will certainly be possible to excavate the rock by either tunnel boring machine or traditional drill and blast methods, this rock mass may contain large interconnected voids (karsts) with water and silt, potentially under high pressure. Specific construction measures may be needed in this area, as presented in Sect. 1.2.1. Placement optimisation of the underground structures has ensured that the location of larger underground structures, such as caverns and shafts, avoids areas where limestone formations are likely to be encountered. This will require careful review at the conclusion of the ongoing site investigation campaign. The shafts will need to be excavated through varying depths of so-called moraine strata before the molasse rock is reached. This stratum is a mix of clays, sands, gravels and boulders. It is known to contain aquifers.

CERN has over 40 years of experience in managing projects that involve the construction of tunnels, shafts, and caverns in the molasse rock and, therefore, has the experience and knowledge to undertake the FCC civil engineering. Some aspects, as listed below, will be challenging but nonetheless well within the capabilities of many Member States civil engineering contractors.

* The average depth at which the underground structures will be constructed is about three times greater than the average depth of the LHC tunnel. This will present higher ground stresses that will need to be considered in the design of the underground structures and when selecting the construction methodologies to be used. Proven engineering solutions will be applied to effectively mitigate potential challenges, such as ground deformation, and ensure the smooth operation of the tunnel boring machine.

* The tunnel will need to pass through a zone of so-called 'molasse charrié' a geological formation with different characteristics compared to the molasse rock in which CERN's existing underground structures were constructed. These factors will be carefully addressed in the design and construction methodology to ensure a safe and efficient excavation process.

* The tunnel will pass through several kilometres of limestone, which may contain water at high pressure. Similar conditions were encountered during the construction of the LEP tunnel, providing valuable insights into mitigation measures. Careful consideration will need to be given to the tunnel design, selection of tunnelling methods and the provision of ground treatment ahead of the tunnelling face in this zone of limestone rock. Modern engineering solutions, coupled with CERN's experience, ensure that potential challenges are well understood and can be managed effectively.

* The tunnel will pass under Lac Léman. As far as possible, the tunnel horizon will be kept within the molasse rock. If this is not possible then alternative tunnelling techniques for traversing water-bearing sands/gravel/silts will need to be used, such as earth pressure balance tunnel boring machines or so-called slurry tunnel boring machines).

* It is likely that during the construction of some shafts, water-bearing moraine strata will need to be traversed before reaching the more favourable moraine rock. Again, this will require the use of specialised construction methodologies such as diaphragm walls or ground freezing.

Although some aspects of the civil engineering underground construction will be technically more challenging than previous CERN construction projects, it is considered that the underground civil engineering structures can be designed and constructed using existing, proven, conventional techniques, including CERN's extensive experience in underground construction. This consideration is supported by the technical discussions that CERN has held with tunnelling contractors.
<figure><img src="image_7.png" /><figcaption>**Fig. 1.2** Accelerator tunnel cross-section</figcaption></figure>

The constraints arising from the large-scale geological environment on underground civil engineering, as described in the conceptual design report, are still largely valid. It is to be noted, however, that the reduction in the circumference of the collider and accelerator tunnel has resulted in a higher probability that the tunnel can be predominantly located in the favourable molasse rock due to the general displacement of the tunnel away from the limestone regions associated with the Jura, Vuache and Mandallaz outcrops. Again, this should be confirmed with the completion of the ongoing site investigations.

### 1.2.1 Accelerator tunnel

The majority of the 90.6 km circumference FCC tunnel alignment consists of a 5.5 m internal diameter tunnel, as illustrated in Fig. 1.2. There are eight sectors, each approximately 11.3 km in length. The majority of each sector consists of an arc of a radius of 14.5 km.

The accelerator tunnel houses the beam and service infrastructure, as well as a transport corridor. The current design of the tunnel assumes that where tunnel boring machines (TBMs) are used for excavation, a precast reinforced concrete segmental lining will be used to support the tunnel. In areas where TBMs will not be employed, primary support consisting of rock bolts and fibre-reinforced shotcrete will be used with a secondary cast in-situ concrete lining. The tunnel floor is to be cast in-situ concrete and installed over void formers for the tunnel drainage and the fresh air duct. Access chambers for the drainage network will be spaced every 100 metres along the tunnel. To ensure that the internal diameter is at least 5.5 m for the integration of technical infrastructure, the accelerator tunnel will be constructed with a tolerance envelope of 100 mm.

The installation of the precast segmental lining that supports the ground is carried out automatically from within the TBM. CERN has discussed with a European TBM manufacturer the potential machine requirements for the construction of FCC. They stated that either a double shield or single shield TBM (like that shown in Fig. 1.3) could be utilised.
<figure><img src="image_8.png" /><figcaption>Fig. 1.3 Single shield TBM. Source: Herrenknecht</figcaption></figure>

A typical benefit of a double shield TBM over a single shield is the increased speed of construction, this is because the machine can simultaneously excavate the ground and install the segmental tunnel lining. Conversely, a single-shield machine requires these two phases to occur sequentially. A double-shield machine is also better suited and more adaptable to variable geology and unstable ground.

However, the increased complexity of the double shield machine TBM leads to greater capital cost, higher maintenance demand and increased risk of TBM breakdown, when compared to single shield TBM.

Feedback from civil engineering contractors specialised in tunnelling indicates that in the relatively stable molasse rock of the FCC a single shield TBM could be a more cost-effective solution. Furthermore, the increased speed of construction offered by a double shield machine may not actually be achieved, since the logistics of material delivery and spoil extraction at the shafts, and over the long tunnelling distances, would be more of a constraint to the TBM advance rate than the capability of the machine itself.

Whilst the majority of tunnel excavation will be within the molasse rock, which lends itself to TBM excavation, as detailed above, a specifically designed TBM may be used for the 4.4 km section of Mandallaz limestone likely to be encountered in the sector PG to PH. This TBM, which would be designed for soft and hard rock conditions, would also have the capability to probe ahead of the tunnel face and provide a real-time assessment of the ground conditions in front of the TBM. The machine would have the capability to inject cement-based grout ahead of the excavation to reduce the risk of ground collapse and water inflow. To take account of the potential difficulties that may be encountered in the limestone, the TBM advance rate has been reduced from an average of 16 m/day to 9 m/day in the construction schedule.

If not excavated by a TBM, this section of limestone would need to be excavated by drill and blast. This is a conventional tunnelling technique involving the use of explosives to excavate the rock face. Depending on the condition of the limestone in this area, additional ground treatment may be required ahead of the tunnel face to prevent water ingress during excavation. The ongoing site investigations will characterise the composition of the limestone along the FCC alignment and, therefore, provide greater certainty of the tunnelling conditions.

For the current feasibility study, it has been assumed that a single-pass precast lining will be the most efficient and effective ground support system, as this is the fastest and most cost-effective construction method. In the case that future site investigations reveal more challenging ground conditions than those that have been assumed, then a review of the tunnel support system will need to be carried out. Where necessary, a more appropriate ground support system, consisting of a drained, reinforced concrete in-situ lining, may be required.

Table 1.2 shows the excavation and lining parameters assumed for the feasibility study.

The current assumption for the start and finish sites for each of the TBMs is shown in Fig. 1.4. The main advantage of this arrangement is that it allows an earlier completion of the technical sites because these do not have TBM installation or deinstallation activities associated with them. This is a major benefit as it allows earlier installation of the infrastructure and accelerator components in the underground areas. Further benefits of this approach are:

* TBMs are large and heavy machines and as such cannot easily be manipulated in the confined spaces of an underground worksite. To install a TBM takes four to six months and requires a cavern large enough to allow the installation. At the four experiment sites, the two large caverns and the long, widened sections of the main beam tunnel can be used for the installation and commissioning of the TBMs.
<table><caption>**Table 1.2** Proposed TBM excavation and lining parameters</caption><thead><tr><td>Parameter</td><td>Properties</td></tr></thead><tbody><tr><td>Minimum internal diameter (m)</td><td>5.5</td></tr><tr><td>Characteristic concrete compressive strength for pre-cast concrete, fck (MPa)</td><td>50</td></tr><tr><td>Pre-cast concrete thickness (m)</td><td>0.30</td></tr><tr><td>Reinforcement density for steel fibre reinforced pre-cast concrete (kg/m³)</td><td>35</td></tr><tr><td>Reinforcement density for steel bar reinforced pre-cast concrete (kg/m³)</td><td>80</td></tr><tr><td>Gasketed segments</td><td>yes</td></tr><tr><td>Total radial construction tolerance (m)</td><td>0.10</td></tr><tr><td>Excavation diameter</td><td>6.6</td></tr></tbody></table>

<figure><img src="image_9.png" /><figcaption>**Fig. 1.4** Proposed arrangement of TBM drives</figcaption></figure>

* The presence of a shaft located directly above the axis of the main beam tunnel gives a significant advantage for the installation of the TBM. It enables the TBM to be installed in relatively large pieces, thereby reducing installation time.

* Provision of two shafts, each capable of providing the necessary logistics and services to support a TBM (transport of people, spoil removal, material, power, water etc.), provides a level of redundancy since, if one shaft is out of action, work can continue via the second shaft.

* Two shafts provide better provision for the evacuation of people in case of an accident or an emergency when access to one shaft may not be possible.

* Concentrating the underground civil engineering at the four experiment sites will allow the four technical sites to have a reduced impact on the local community and the local environment (less dust, noise, traffic etc.).

CERN commissioned a study into the safety, ventilation, and logistics aspects of the FCC construction to address concerns that the 5.5 m internal diameter tunnel and 11 km TBM drives would present significant safety and logistical risks, particularly with only a single means of access and egress. It was demonstrated that using currently available technology, the tunnel could be constructed safely, and the assumed TBM advance rate could be achieved. Ventilation requirements were shown to be met over the full length of the tunnel, with ducting and fan specifications calculated to supply adequate fresh air to the excavation front. Finally, safety measures were outlined to ensure that construction activities would meet the required standards both nationally and internationally. An example of the tunnel cross-section during construction is shown in Fig. 1.5. An example of the safety refuge chambers specified in the study is shown in Fig. 1.6.

To accommodate the separation of the $e^+$ and $e^-$ beams of the FCC-ee machine near the detector locations and the need to maintain space for the booster ring, the accelerator tunnel requires enlargement on each side of the experiment caverns at PA, PD, PG, and PJ. There are a total of 8 tunnel enlargement areas, which extend for 1.1 km on either side of the experiment caverns. To minimise construction costs and optimise efficiency, the enlargements will be created in a stepped design, as shown in Fig. 1.7.
<figure><img src="image_10.png" /><figcaption>**Fig. 1.5** Cross-section of the accelerator tunnel during construction. Credit: Amberg</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>**Fig. 1.6** Example refuge chamber placed at the back of the TBM. Credit: mineARC</figcaption></figure>

The widened tunnel sectors are split into 6 sections on either side of the experiment cavern, ranging from 18.6 m to 14.5 m in span and section lengths varying between 20 and 160 m. A seventh sector of widening tapers from 14.5 m span to the regular 5.5 m diameter of the accelerator tunnel. This seventh sector commences from the end of the long straight section through into the arc section for a length of 438.5 m. The beamstrahlung absorber will be located 500 m from the interaction point (IP) within Sect. 3 of the tunnel widening. A 20 m section of increased tunnel height may be required to provide space for a crane around the beamstrahlung absorber. This is not currently incorporated in the feasibility study baseline for civil engineering. If confirmed as necessary, this will be incorporated in the baseline during the next design phase.

The construction of the tunnel-widening sections is proposed to be undertaken using conventional excavation methods such as roadheader and/or hydraulic rock-breaker machines. A shotcrete final lining is proposed with the aim of reducing construction time, thereby enabling an earlier installation of the TBMs, which will be carried out within the tunnel widening sections on either side of each experiment cavern.
<figure><img src="image_12.png" /><figcaption>Fig. 1.7 Plan view of the typical tunnel widening at an experiment cavern</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>Fig. 1.8 Plan view of PA showing the layout of connection tunnels between the service cavern and experiment cavern</figcaption></figure>

1.2.2 Bypass tunnels

Bypass tunnels are required at each of the four experiment areas to allow access for transport, personnel, and services directly from the service cavern to the accelerator tunnel, therefore bypassing the experiment cavern and detector areas. These tunnels will have an internal diameter of 5.5 m, similar to the cross-section of the accelerator tunnel. The length of the bypass tunnels varies between 110 and 115 m, depending on the experiment area. The 30 m radius bends allow transport vehicle movements as well as provide radiation protection between the accelerator tunnel and the service cavern. The bypass tunnels connect the service cavern to the accelerator tunnel within the first section of the tunnel widening, approximately 74 m from the experiment cavern. The junction between the accelerator tunnel and bypass tunnel is at an angle of 45 degrees, for the purpose of civil engineering constructibility. However, transport needs may require a shallower angle to be specified. In the next design phase, the details of the junctions between the two tunnels will be reassessed, and if required, a junction cavern or other more effective means of accommodating the connection will be implemented.

The bypass tunnels will be constructed using a roadheader machine and lined with in-situ concrete for the final lining. The construction of these tunnels will be completed in parallel with the works for the connection tunnels and tunnel-widening sections at each experiment point.
<figure><img src="image_14.png" /><figcaption>**Fig. 1.9** Cross-section through the 12 m diameter service shaft, as proposed at the four technical areas</figcaption></figure>

### 1.2.3 Connection tunnels

The connection tunnels between the service caverns and experiment caverns provide personnel access and materials/equipment transportation. These tunnels also house the service ducts, cables, and pipes linking the service caverns to the detectors and accelerator tunnels. Figure 1.8 shows a typical layout of connection and survey galleries at an experiment point. Two 5.5 m diameter connection tunnels link either end of the service cavern directly to the accelerator tunnel. These tunnels have an additional forked section of tunnel, of 2.8 m span, to allow personnel access whilst the radiation shielding doors remain closed across the full 5.5 m tunnel section. Two 3.3 m span evacuation tunnels provide a safe means of escape for personnel from the experiment cavern directly to the service cavern. These tunnels are designed with a chicane to provide radiation protection between the two caverns. At the lower level, a 5.5 m diameter connection tunnel is required for service connections and personnel access to the floor of the experiment cavern. The transport tunnel is 10 m in span to accommodate the movement of large equipment, and the connection tunnel has a span of 5.5 m for personnel access and the conveyance of services between the two caverns. At each of the 4 experiment points, a 10 m internal diameter connection tunnel between the bottom of the access shaft and the experiment cavern is required to transport large detector components to the areas inaccessible via the main shaft serving the experiment cavern.

### 1.2.4 Shafts

There are thirteen shafts proposed for accessing the underground structures:

* Four 12 m diameter shafts (like that shown in Fig. 1.9), one at each of the technical areas PB, PF, PH, and PL, for access and service requirements.

* Two 18 m diameter shafts, one at each of the experiment areas, PA, and PG, for access and installation of the detector components in the experiment cavern.

* Two 15 m diameter shafts, one at each of the experiment areas, PD, and PJ, for access and installation of the detector components in the experiment cavern. Note that these smaller experiment shafts are dimensioned to accommodate the smaller detectors planned for PD and PJ.

* Four 18 m diameter shafts, one at each of the service caverns at points PA, PD, PG, and PJ, for access, service requirements and to facilitate the lowering of the largest accelerator components.

* One 10 m diameter shaft on the CERN Prévessin site, to enable the construction of the transfer tunnel from the Injection Complex to the FCC. This shaft will only be used for construction, in particular, to allow the assembly of the TBM to drive the 5 km transfer tunnel length.

The service shafts at each of the eight points provide access to the service caverns. During the construction phase, these will be used for the installation and commissioning of the infrastructure and accelerator components. They will also be used during machine shutdowns for maintenance and upgrade of the accelerator and supporting infrastructure. They will be equipped with two lifts and a stairwell located within a pressurised inner shaft, which provides a safe escape route in case of fire. The shaft also contains a continuous vertical clear space for the crane to lower the equipment.

All four of the experiment caverns are served by either a 18 m or 15 m internal diameter shaft directly above the experiment cavern. These shafts primarily serve for the transportation of the detector components, which will be lowered down the shafts from the Surface hall(SX) for installation in the underground experiment caverns (UX). These shafts will also contain ventilation ducts and other services necessary to support the operation of the detector within the UX caverns. As PA and PG are the largest of the experiment areas, 18 m diameter shafts are required. Being the smaller experiment areas, PD and PJ only require a 15 m experiment shaft at each location.
<table><caption>**Table 1.3** Shaft depths at each site</caption><thead><tr><th>Site</th><th>PA</th><th>PB</th><th>PD</th><th>PF</th><th>PG</th><th>PH</th><th>PJ</th><th>PL</th><th>Transfer Tunnel</th></tr></thead><tbody><tr><td>Moraine Depth [m]</td><td>54</td><td>30</td><td>25</td><td>&lt;5</td><td>24</td><td>20</td><td>31</td><td>40</td><td>12</td></tr><tr><td>Molasse Depth [m]</td><td>147</td><td>171</td><td>156</td><td>400</td><td>202</td><td>215</td><td>222</td><td>210</td><td>17</td></tr><tr><td>Total Depth [m]</td><td>201</td><td>201</td><td>181</td><td>400</td><td>226</td><td>235</td><td>253</td><td>250</td><td>29</td></tr></tbody></table>

<figure><img src="image_15.png" /><figcaption>**Fig. 1.10** Plan view of the sub-surface arrangement at PF, showing the offset service shaft and access tunnel arrangement</figcaption></figure>

The construction shaft proposed for the TBM drives of the transfer tunnel may be used during the infrastructure installation phase to transfer equipment and/or components from the surface into the transfer tunnel.

The shafts have varying depths around the ring, ranging from 29 m to 400 m. Table 1.3 summarises the depths of the shafts at each site, including the depths of the moraine and molasse geological layers. Generally, the shafts are located directly above the corresponding cavern. However, at PF and PB, surface constraints require the shaft to be offset from the service cavern. At PF, this is achieved by constructing a 9 m internal diameter access tunnel 585 m in length, as shown in Fig. 1.10.

All the shafts will be excavated through the moraine strata. Historically, supporting methods such as diaphragm walls, secant piles, and ground freezing have all been used on CERN projects and, therefore, will be appropriate for the construction of FCC shafts.

The shaft depths below the moraine strata will be located in molasse rock. Shafts in molasse have historically been built most cost-effectively using conventional construction techniques (roadheader, hydraulic hammer) combined with shotcrete and rock bolts as primary support followed by a permanent cast in-situ reinforced concrete lining. Diaphragm wall construction consists of excavating a number of straight sections of wall to form a quasi-circular shape. The sides of these excavations are supported with a temporary bentonite slurry mix, which is replaced by reinforcement cages and concrete to form the primary lining, inside which the shaft excavation can proceed. Figure 1.11 shows an example of the cross-section of a typical 12 m diameter service shaft in the moraine using the diaphragm wall technique.

Once stable rock (i.e., the molasse) is reached, the excavation is supported temporarily by rock reinforcement such as rock bolts and shotcrete, before installing a waterproof membrane and the permanent cast in-situ reinforced concrete lining. The slip-forming technique can be used for the permanent lining, where the concrete is poured into a continuously climbing formwork.

The staircases and lift shafts required within the service shafts for personnel and material access are constructed from prefabricated elements that are stacked on top of each other from the top of the shaft. These are placed as
<figure><img src="image_16.png" /><figcaption>**Fig. 1.12** Cross-section through the 3D model at PA, showing the service cavern (left) and experiment cavern (right)</figcaption></figure>

<figure><img src="image_17.png" /></figure>

one of the final construction activities once all major civil engineering works are completed below ground and before the civil engineering structures are handed over to CERN.

As the shafts for FCC are deeper than any previously constructed at CERN, a specialist shaft-sinking consultant provided an assessment of possible excavation techniques suitable for these greater depths. The study focused on the logistical considerations of the construction and the servicing of shafts to up to 400 m in depth (the deepest shaft at site PF). The assessment concluded that utilising current technologies and best working practices, the shafts as proposed are feasible to construct. They advised that with all shafts being constructed in parallel, procurement of sufficient specialised labour and equipment ahead of time would be key to ensuring that sufficient resources are available, thus minimising the risk of a delay to the construction schedule. The study also highlighted that there would be potential for equipment used during shaft sinking, also to be utilised during later cavern and tunnel excavation works. This could offer benefits to both the cost and the construction schedule. Furthermore, CERN was advised that advances in mechanisation and future shaft-sinking technologies could reduce construction durations as well as project risks, in particular through the recent development of a vertical shaft-sinking machine that does not require human intervention within the shaft itself.

### 1.2.5 Caverns

Large-span caverns are required at both experiments, PA and PG, to accommodate the FCC detectors and associated infrastructure. The proposed cavern dimensions are 66 m × 35 m × 35 m (L × W × H) and the caverns will be constructed at a depth of up to 226 m in the molasse rock. Although these will be the largest caverns ever constructed at CERN, they will not be significantly larger than the current ATLAS cavern of the LHC.

The construction sequence will consist of benched excavations using rock breaker and roadheader machines, with the primary support being provided by rock bolts, cable bolts and layers of steel-reinforced shotcrete. During the widening of the crown area of the experiment cavern, additional lattice girders and layers of steel-reinforced shotcrete will be installed. The lattice girders for the various excavation steps can be bolted together to ensure continuous rock support along the excavated area. The secondary lining will be constructed from cast in-situ concrete to provide additional strength and protection to the cavern walls. A waterproofing and drainage membrane will be installed between the primary and secondary linings to ensure that the cavern remains dry and that the structure is not subject to excessive water pressure arising from any groundwater that may be present.

Two smaller experiment caverns, 66 m × 25 m × 25 m (L × W × H), are required at PD and PJ. These caverns will be constructed at up to 253 m depth using the same techniques for excavation and support as the experiment caverns situated at PA and PG.
<figure><img src="image_18.png" /><figcaption>**Fig. 1.13** 3D model view of the klystron gallery arrangement at PH</figcaption></figure>

A service cavern at the same elevation as the accelerator tunnel with dimensions of 100 m × 25 m (L × W) is required adjacent to each of the four experiment caverns. Figure 1.12 is a cross-section through the 3D model for PA showing the service and experiment caverns. Below the service shaft, the height of the service caverns is 22.4 m thereby providing direct access to the experiment cavern floor for large equipment and detector components. The remainder of the 100 m long service cavern has a height of 15 m. Shorter service caverns of 60 m length are necessary at the remaining four technical points. The service caverns will house infrastructure equipment such as electrical, cooling, ventilation and cryogenics. Furthermore, the caverns will provide a safe refuge in the event of an emergency, with a dedicated pressurised area at the bottom of the shaft. These caverns will be constructed in the same manner as the experiment caverns. At the experiment sites, the spacing between the two caverns is approximately 50 m, to mitigate electromagnetic effects from the detector on the nearby electrical components. This also improves the overall structural efficiency by providing a sufficiently large rock pillar between the experiment and service caverns, thus minimising the structural support needed and reducing the risk and complexity of construction.

The service caverns will contain three floor levels, with steel structures providing the frame for each level. This greatly increases the usable space for technical infrastructure and services. Steel structures will also be used to create the gallery levels around the detectors in the experiment caverns. These will be similar to the galleries currently in place within the LHC experiment caverns, such as ATLAS and CMS.

Where tunnels of similar cross-section dimensions connect, a junction cavern is required. PF, PH and PL each require a junction cavern where the 7 m diameter connection tunnel from the service cavern intersects with the 5.5 m accelerator tunnel. Each cavern is 16 m long and at a span of 10 m.

An additional cavern for the FCC-ee machine beam absorber will be located at PB, and this will accommodate two beam absorbers, one for each of the two beam lines. Further details of this structure are provided in Sect. 1.2.8.

Survey galleries are required at each of the four experiment caverns to survey the beam alignment on either side of the detectors. These consist of 1.5 m span tunnels of 60 m length, running parallel to the accelerator tunnel, with perpendicular connections made every 15 m into the tunnel widening Sect. 1. The possibility of incorporating these into the widened tunnel sections to reduce complexity and cost of construction will be studied in the next design phase.

### 1.2.6 Underground structures for Radio Frequency Infrastructure

The klystron galleries are an essential part of the FCC-ee civil engineering, as they will house the klystrons and other components of the Radio Frequency (RF) system. To accommodate the necessary infrastructure, two separate galleries will be constructed, one at PH and the other at PL. The klystron gallery at PH (Fig. 1.13) will be 2012 m long for the collider RF system, while the gallery at PL will be 1446 m long for the booster RF system. To allow access to the klystron galleries during the operation of the FCC-ee machine, sufficient radiation shielding needs to be provided. To achieve this, 10 m of rock will be maintained between the RF galleries and the accelerator tunnel. The internal dimensions of the galleries are 10 m in span and 5.5 m high to accommodate the transport and placement of the equipment within the galleries, as well as allowing access for maintenance and repair during the operation phase.

The galleries are sized with a 50 m extension in length at either end to incorporate the space for service equipment. This is proposed instead of constructing the large alcoves along the accelerator tunnel, thereby enabling a more efficient use of tunnel excavation and space.
<figure><img src="image_19.png" /><figcaption>**Fig. 1.14** Cross-section through the klystron gallery and accelerator tunnel, including wave-guide duct between</figcaption></figure>

The galleries are connected directly to the accelerator tunnel via 1 m internal diameter wave-guide ducts, spaced every few metres along the gallery (see Fig. 1.14. There will be 428 individual wave-guide ducts at PH and 312 at PL.

The safety concept for FCC requires that for emergency egress, stairwell shafts are spaced at intervals of 341 m along the gallery to connect the galleries to the accelerator tunnel.

For access to the klystron galleries, a 7 m internal diameter connection tunnel links the upper level of the service cavern and the klystron gallery. This connection tunnel has a length of 62 m. The size of the connection tunnel is designed to accommodate personnel access and the transport of the RF equipment into the gallery.

The klystron galleries will be excavated using the same road header type machines that will be used for the excavation of the caverns and connection tunnels at points PH and PL. Roadheader excavation is efficient and accurate, allowing precise excavation of the galleries. The klystron gallery lining will consist of a shotcrete primary lining and a cast in-situ concrete secondary lining. It may be feasible to use shotcrete for the final lining of the gallery, as this would potentially offer faster construction and lower cost. This option will be studied during the next phase. The floor of the gallery will also be made of cast in-situ concrete and will include a drainage channel and the entry of the waveguide ducts up through the floor slab. The entry of the wave-guide ducts into the gallery will require the use of a chicane to provide radiation protection. This will likely be constructed with a precast concrete unit placed after the final installation of the cryogenic line (QRL) infrastructure through the duct.

The wave-guide ducts, which will contain the wave-guides linking the klystrons to the RF cavities in the accelerator tunnel, will be excavated by raise boring. This process involves first drilling a pilot hole and then attaching a reamer head at the bottom, which is pulled up, excavating the duct from below in a vertical direction. This method of excavation is efficient and minimises disruption to the surrounding rock. A steel or concrete lining will be grouted into the rock to provide a suitable finished surface and final lining.

### 1.2.7 Alcoves

At 1.6 km centres around the circumference of the machine, equipment alcoves, as illustrated in Fig. 1.15, are required to accommodate electrical equipment, services and transport needs. The majority of these alcoves are considered ‘regular’, measuring 40 m in length, 10.6 m in width, and 4.6 m in height. Positioned on the inside of the ring, the alcoves are arranged perpendicular to the accelerator tunnel.

In addition to the regular alcoves, twelve ‘large’ alcoves are needed on either side of each of the FCC access points to provide extra space for electrical equipment. These larger alcoves are 29 m in length, 18 m in width and 8.3 m in height. These large alcoves will be located at the end of the long straight sections on either side of the caverns. Two large alcoves are required at PA, PB, PD, PF, PG, and PJ, but not at PH or PL, because the additional size of the klystron galleries provides the necessary volume for the equipment. An example of a large alcove is shown in Fig. 1.16. In total, the project requires 40 regular alcoves and 12 large alcoves.
<figure><img src="image_20.png" /><figcaption>Fig. 1.16 Model view of a large alcove and transport passing bay</figcaption></figure>

An access area to each alcove is provided to accommodate the radiation protection chicane walls. This section is 6 m long and has a 10.6 m span at the entrance to both large and regular alcove types.

A transport-passing bay is required at the entrance to each alcove. This will facilitate the passing of transport vehicles travelling in opposite directions through the tunnel. The passing bay also provides space for the parking of transport vehicles during installation and shutdowns, with additional space for servicing/repairing the vehicles if necessary. The majority of the passing bays are accommodated in a cavern along the accelerator tunnel alignment and measure 16 m in length and 11 m in width. Additional larger passing bays are required at the mid-section of each accelerator tunnel arc. There will, therefore, be a total of 8 larger passing bay caverns, measuring 30 m by 11 m. These facilitate the passing of the magnet delivery vehicles during the installation phase of the FCC-ee machine. An example of the large passing bay is shown in Fig. 1.17.

Unlike the caverns and tunnels in proximity to the FCC points, which can be at least partially excavated in parallel with the TBM drives, excavation of the alcoves and passing bays will need to be completed after the TBM drive is complete. This is because the full tunnel section is required to support the TBM (ventilation, conveyor for spoil removal, transport corridor for concrete segmented linings, corridor for personnel etc.). It will, therefore, be necessary to break out the concrete tunnel lining and excavate the passing bay cavern and alcoves using roadheader excavation. The inner lining works for the alcoves will then be carried out ahead of the relining of the accelerator tunnels. This will have to be coordinated with the installation of the tunnel floor. The overall construction sequence and structural design will be similar to the caverns, as detailed in Sect. 1.2.5.

The complexity of the alcove construction and the associated logistical challenges have a major impact on the construction schedule, since each alcove is potentially on the critical path for civil engineering. CERN has
<figure><img src="image_21.png" /><figcaption>**Fig. 1.17** Example of a regular alcove and large passing bay located at the centre of each arc sector</figcaption></figure>

commissioned an additional study to investigate the optimal method of constructing the alcoves in order to minimise the impact on the overall construction schedule. As a result, the current assumption in the schedule remains that alcoves can be constructed in parallel to one another, maintaining sufficient access, safety and logistical standards. By adopting an overlapping sequence of construction activities, all alcoves of each sector can be constructed within a 12-month period, thereby achieving the targeted handover date of each sector for the subsequent infrastructure and accelerator installation.

### 1.2.8 Beam absorber cavern

The absorbers for the FCC-ee beams will be located at PB. The beam absorber cavern layout includes a 708 m long cavern with a span of 13.6 m, to house both the $e^+$ and $e^-$ absorber infrastructure. The size of the cavern has been dictated by the beam extraction length and angle, which requires a separation from the accelerator line of at least 5.5 m and a septum/kicker angle of 10 mrad. The two beam extraction lines are arranged to cross at the centre of the cavern, adjacent to the centre of the PB long straight section. This ensures that the beam absorber cavern volume is optimised.

To accommodate the separation of the two FCC-ee beams on the approach to PB, a series of tunnel widening sections is required either side of the cavern. Three sections of tunnel widening, of lengths from 83 to 330 m will be constructed either side of the cavern to increase the span of the accelerator tunnel from 5.5 to 7.8 m.

The absorber cavern will be excavated in the same manner as other caverns, using roadheader and/or rock breaker machines to excavate from the roof level down using a series of ‘benches’. Due to the constraints at the surface, the service shaft and cavern will need to be offset from the centre point of the long straight section (LSS). The offset service shaft will, therefore, be positioned 350 m from the centre of the LSS and connect to the beam absorber cavern via a connection tunnel of 97 m length.

The absorber cavern will be constructed as mentioned in Sect. 1.2.5. There will be a shotcrete and rock bolt primary lining with an in-situ concrete secondary lining. However, the option to create the final lining from shotcrete will be considered in future design development to potentially reduce costs and reduce the construction time. It is yet to be confirmed whether a shielding wall/structure is required within the cavern to shield the accelerator from the beam absorber apparatus; however, this would be constructed with precast concrete blocks well after the civil engineering has been completed. A schematic view of PB including the beam absorber cavern is shown in Fig. 1.18.

### 1.2.9 Excavated material

To construct the subsurface structures, approximately 6.3 million m³ (in-situ volume) of rock will be excavated. This material will be extracted via the eight FCC access points. The predominant rock type will be molasse,
<figure><img src="image_22.png" /><figcaption>**Table 1.4** Excavation volumes for each FCC sector</figcaption></figure>

<table><thead><tr><th></th><th>In-situ Vol,<br>10<sup>3</sup> m<sup>3</sup></th><th>Bulk Vol.,<br>10<sup>3</sup> m<sup>3</sup></th><th>Compacted Vol.,<br>10<sup>3</sup> m<sup>3</sup></th><th>% of Total</th></tr></thead><tbody><tr><td>PA</td><td>1378</td><td>2205</td><td>1791</td><td>22%</td></tr><tr><td>PB</td><td>148</td><td>237</td><td>192</td><td>2%</td></tr><tr><td>PD</td><td>1274</td><td>2038</td><td>1656</td><td>20%</td></tr><tr><td>PF</td><td>165</td><td>264</td><td>215</td><td>3%</td></tr><tr><td>PG</td><td>1365</td><td>2184</td><td>1775</td><td>22%</td></tr><tr><td>PH</td><td>312</td><td>499</td><td>405</td><td>5%</td></tr><tr><td>PJ</td><td>1289</td><td>2062</td><td>1675</td><td>20%</td></tr><tr><td>PL</td><td>241</td><td>386</td><td>313</td><td>4%</td></tr><tr><td>Transfer Tunnel</td><td>122</td><td>195</td><td>159</td><td>2%</td></tr></tbody></table>

accounting for 96% of the total material. Moraine rock accounts for 1.5% of the excavated material, and limestone makes up the remaining 2.5%.

Figure 1.4 in Sect. 1.2.1 shows the baseline arrangement for the TBM drives. As mentioned, the accelerator tunnel sectors will be excavated using TBM. Shafts will be excavated by conventional mined excavation or vertical shaft-sinking machines. The use of diaphragm walls will be necessary to support the excavation of shafts through the initial moraine layer. All other excavations for subsurface structures will be constructed by hydraulic hammer (rock breaker) and roadheader machines. The physical characteristics of the excavated material will differ according to the excavation method utilised.

Table 1.4 provides a breakdown of the excavated material quantities extracted from each of the eight sites and the transfer line between Prévessin and the FCC tunnel. The volumes are expressed as the in-situ volume i.e., the volume prior to excavation, the bulked volume i.e., the volume after excavation and the compacted volume i.e., the volume after the material has been re-compacted for example in a spoil deposit zone.

Two TBM drives will commence at PA, one driven towards PB and the other driven towards PL. The resulting total material extracted from PA will be almost 1.4 million m³, of which, 62,721 m³ is expected to be moraine.

No TBM drives are planned from PB, the volume of excavated material, therefore, arises from the subsurface structures at PB, including the beam absorber cavern. Of the total quantity of, 147,852 m³, 10,473 m³ is expected to be moraine and the remainder is molasse.

Two TBM drives will commence at PD, one driven towards PB and the other towards PF. The resulting quantity of material to be extracted from PD is 1.3 million m³ of which, 24,925 m³ is expected to be moraine.

No TBM drives are planned from PF. As with PB, the excavated material at PF only arises from the subsurface structures directly located at PF and not the accelerator tunnels either side. Almost all the excavated material at PF will be molasse as there are little or no quaternary deposits.

Two TBMs will be driven from PG, one driving towards PF and the other towards PH. The total quantity of material excavated from PG is almost 1.4 million m³. Moraine makes up 30,829 m³ of the total excavated material at PG. However, due to the 4.4 km long sector of limestone along the accelerator tunnel between PG and PH, 141,175 m³ of the total material will be limestone rock. The remaining 1.2 million m³ of excavated material will be molasse.
No TBM drives are planned from PH, therefore all the excavated material comes directly from subsurface structures at PH, including the klystron gallery and associated structures. 7482 m³ of the total excavated material at PH is expected to be moraine, and the remainder is molasse.

Two TBMs will be driven from PJ, one driven towards PH and the other towards PL. Therefore, the quantity of material extracted from PD is around 1.3 million m³ of which, 29,910 m³ is expected to be moraine.

No TBM drives are planned from PL, the volume of excavated material is therefore attributed to the subsurface structures at PL, including the klystron gallery and associated structures. Moraine rock is expected to make up 13,468 m³ of the total excavated material at PL.

The Prévessin to SPS and SPS to FCC injection tunnels account for 122,329 m³ of excavated material, the majority of this material will be extracted from the Prévessin site, by means of the proposed construction shaft. A small proportion of the excavated material will be moraine, from the initial excavation of the shaft, but the majority of the shaft and transfer tunnel excavation will be in molasse rock.

### 1.2.10 Tunnelling in the molasse rock

The large-scale geological environment within which the FCC underground infrastructure will be excavated is shown in Fig. 1.19, with most of the tunnel located within the Lower Freshwater Molasse (USM) and Lower Marine Molasse (UMM). The FCC will be excavated at depths of up to 560 m, with a total combined length of all excavations exceeding 100 km. Whilst the experience gained by CERN over the previous 50 years for the construction of the LEP, LHC and Hi-Luminosity LHC has given valuable insight into the likely characteristics and behaviour of the molasse rock, other projects excavated within the molasse rock have also been the subject of a desktop study in order to improve the understanding of the environment in which the FCC civil engineering will be constructed.

Most of the projects reviewed were transport tunnels (road and rail) from a few hundred metres to a few kilometres in length at shallow depths. Tunnels were excavated by means of conventional excavation, cut and cover, and TBM. One project in particular, the Moutier tunnel, was excavated by a single shield TBM in the Alsace tertiary molasse (a mix of marl, sandstone and limestone). Due to an unforeseen geological environment, the TBM became stuck 190 metres into the tunnel drive. As a result, the remainder of the tunnel was excavated using conventional methods. This project highlights the need for sufficient geotechnical investigations and appropriate analysis to be completed before construction begins. At the greater depth of FCC, the molasse is likely to be more consolidated and unlikely to have been altered due to weathering. However, appropriate geotechnical investigations and numerical analysis will be required to better predict the likely behaviour of rock and its influence on the performance of the tunnel boring machine.

Generally, the review confirms that excavations in molasse rock have been extensively conducted in Switzerland using both TBM and conventional methods. However, the FCC will require a comprehensive geotechnical investigation to assess the characteristics of molasse as well as the in-situ stress regime. The investigation will address potential risks, including those arising from changes in pore water pressure, rock squeezing, and geological faults.

A tunnelling project has been identified in the UK with characteristics similar to those of the FCC. It is currently under construction as part of a new Halite mine development. A single TBM excavates a 37 km long tunnel with cross-sectional dimensions that are very similar to those of the FCC. Furthermore, the tunnel is being excavated at comparable depths and within sedimentary geology that is not dissimilar to that expected for the FCC. An average tunnelling excavation rate of 20 m/day have been achieved. CERN will assess this project for lessons learned in more detail during the next phase of the FCC.

In conclusion, it is considered that underground civil engineering for the FCC is feasible and within the current experience and capabilities of many of the major designers and contractors currently active within the CERN member states. Additional site investigations will be required to finalise the precise depth and inclination of the FCC tunnel and to determine the geotechnical properties of the rock mass, which are necessary for CERN to move forward to the detailed design and construction phases.

## 1.3 Surface structures

Since the completion of the conceptual design, there has been a rationalisation of the surface sites associated with the FCC-ee civil engineering, with the number of surface sites reduced from twelve to eight. The eight surface sites will comprise four areas suitable for siting experiments and four assigned as technical areas. The eight sites are spread evenly around the circumference of FCC-ee collider ring. The four experiment areas are symmetrically distributed such that each site is diametrically opposite another experiment site, as illustrated in Fig. 1.1. The experiment sites are at sites PA, PD, PG and PJ with the technical sites at the remaining sites PB, PF, PH and PL. The location of the four experiment surface sites is interdependent since the interaction points for each of the four sites define the location of the experiment and service shafts at each site as illustrated in Fig. 1.20
<figure><img src="image_23.png" /><figcaption>**Fig. 1.19** Geographical map of Switzerland. Credit: Philippos Garefalakis, F. S. (2019). Tectonic processes, variations in sediment flux, and eustatic sea level recorded by the 20 Myr old Burdigalian transgression in the Swiss Molasse basin</figcaption></figure>

The experiment access shafts can only be in one of two locations with respect to the interaction point, and the machine access shafts should ideally be placed directly above the service cavern, which itself needs to be located approximately 50 m from the experiment cavern for structural stability of the two caverns and for electromagnetic shielding. Since each of the four interaction points associated with the experiment areas is located precisely with respect to each other, the locations of the shafts at each experiment point are also fixed with respect to the shafts at the other experiment points. This interdependency across the four experiment sites influences the layouts of the surface sites, since the two shafts are associated with specific building configurations.

The selection of surface site locations for the experiment areas requires careful coordination, as each site is interconnected with the location of the other three. For the technical sites, while proximity to the centre of the associated long straight section (LSS) is a key factor, some flexibility exists. The single machine access shaft can be linked to the accelerator tunnel via an access gallery, which, if required, can extend several hundred metres in length.

For a comprehensive discussion on environmental considerations, including landscape integration, readers are referred to the relevant sections in Chaps. 2 and 3 in this Volume.

The engineering designs of the surface site constructions that are eventually part of the project authorisation files need respond to the requirements of the equipment that will eventually be housed at each site. Noisy equipment will be adequately noise insulated and placed in constructions that permit containing the residual noise within
<figure><img src="image_24.png" /><figcaption>**Fig. 1.20** Options for experiment and service shaft locations relative to the interaction point</figcaption></figure>

the applicable regulatory frameworks in place at the time. Examples of structures that may require such specific
measures include:

* Cryogenic plants comprising compressors.

* Cooling and ventilation equipment with pumps, motors and fans.

* Electrical equipment such as transformers.

The choice of construction materials and techniques for surface site buildings is guided by multiple factors, including durability, safety, cost and environmental considerations such as landscape integration and regulatory constraints such as urbanism prescriptions. Newly emerging materials and technologies, as well as continuous monitoring of the environmental and regulatory prescriptions, including applicable energy efficiency standards, will be considered during the subsequent design phase. In line with CERN's governance framework, the territorial principle applies, i.e., the national laws and guidelines apply for infrastructure on the surface sites in the Host States.

At this stage, no architectural strategies have been adopted. This will be done in the next design phase. The development of the architectural solutions will include a robust consultative process with the Host States, regional stakeholders and local communities. A more detailed discussion can be found in Sect. 2

For technical feasibility and costing purposes, the U.S. Fermi National Accelerator Laboratory has analysed the technical needs of two of the eight surface sites in the framework of the international FCC collaboration. The study used an experiment site (PA) and a technical site (PB) as generic examples. The work resulted in the production of detailed drawings of the buildings at the sites. These designs were used as the basis for an initial cost estimate for the surface works. It should be stressed that these designs represent preliminary input for technical and financial feasibility and construction planning purposes only and are not approved designs.

The subsections below present simplified versions of these concepts that permit further development of site configurations and cost estimates.

The Chaps. 2 and *Territorial implementation* provide a further detailed examination of the contextual considerations, planning strategies, and logistical challenges associated with the surface sites, offering further insight into how these elements are being harmonized within the broader project vision.

1.3.1 Surface site - PA

The surface site PA will be the location for one of the four experiment areas. The site is located close to the existing CERN LHC surface site P8 which allows the re-purposing of some of CERN’s existing LHC facilities and infrastructure to support the FCC-hh activities at site PA.

The buildings and other necessary civil engineering surface infrastructure for all surface sites have been identified and included within the civil engineering product breakdown (PBS) structure, which is shown for PA only in Table 1.5.

A significant feature of this and all experiment area surface sites is the large assembly hall that will be used for the sub-assembly and preparation prior to the transfer of the detector components to the underground experiment cavern. It is to be noted that any future assembly hall for an FCC-hh detector may need to be larger than that for an FCC-ee detector, and therefore, a footprint is reserved on the site for such a future expansion/reconfiguration of the assembly hall. The final details of a conceptual design for this building at the FCC-hh phase will be determined in parallel with a future fabrication and assembly strategy for the associated detector.
<table><caption>**Table 1.5** PBS for PA surface structures</caption><thead><tr><th colspan="5">PBS Level</th><th rowspan="2">PBS Description</th></tr><tr><th>0</th><th>1</th><th>2</th><th>3</th><th>4</th></tr></thead><tbody><tr><td>2</td><td></td><td></td><td></td><td></td><td><strong>Civil Engineering</strong></td></tr><tr><td>2</td><td>2</td><td></td><td></td><td></td><td><strong>Surface Structures</strong></td></tr><tr><td>2</td><td>2</td><td>1</td><td></td><td></td><td><strong>Site PA</strong></td></tr><tr><td>2</td><td>2</td><td>1</td><td>1</td><td></td><td>Roads, parking spaces, footpaths, fences, gates, landscaping, drainage</td></tr><tr><td>2</td><td>2</td><td>1</td><td>2</td><td></td><td>Technical galleries</td></tr><tr><td>2</td><td>2</td><td>1</td><td>3</td><td></td><td>Fire fighting equipment and medical station</td></tr><tr><td>2</td><td>2</td><td>1</td><td>4</td><td></td><td>Control building</td></tr><tr><td>2</td><td>2</td><td>1</td><td>5</td><td></td><td>Assembly hall</td></tr><tr><td>2</td><td>2</td><td>1</td><td>6</td><td></td><td>Magnet storage</td></tr><tr><td>2</td><td>2</td><td>1</td><td>7</td><td></td><td>Shaft head building</td></tr><tr><td>2</td><td>2</td><td>1</td><td>8</td><td></td><td>Tunnel ventilation</td></tr><tr><td>2</td><td>2</td><td>1</td><td>9</td><td></td><td>Chilled water production facility</td></tr><tr><td>2</td><td>2</td><td>1</td><td>10</td><td></td><td>Experiment cavern ventilation</td></tr><tr><td>2</td><td>2</td><td>1</td><td>11</td><td></td><td>Service cavern ventilation</td></tr><tr><td>2</td><td>2</td><td>1</td><td>12</td><td></td><td>Cooling plant and waste heat recovery</td></tr><tr><td>2</td><td>2</td><td>1</td><td>13</td><td></td><td>SF annex</td></tr><tr><td>2</td><td>2</td><td>1</td><td>14</td><td></td><td>Warm compressor</td></tr><tr><td>2</td><td>2</td><td>1</td><td>15</td><td></td><td>Helium gas tanks foundations</td></tr><tr><td>2</td><td>2</td><td>1</td><td>16</td><td></td><td>Liquid Nitrogen storage tank foundations</td></tr><tr><td>2</td><td>2</td><td>1</td><td>17</td><td></td><td>Power converters building</td></tr><tr><td>2</td><td>2</td><td>1</td><td>18</td><td></td><td>Electrical equipment building</td></tr><tr><td>2</td><td>2</td><td>1</td><td>19</td><td></td><td>Electrical substation</td></tr><tr><td>2</td><td>2</td><td>1</td><td>20</td><td></td><td>Waste material storage building</td></tr></tbody></table>

The site location has some specific constraints, including:

* The presence of a gas pipeline running adjacent to but outside the site. The layout of the buildings within the site takes into account the presence of this pipeline and, in the future development of the design, how to cross the pipeline to allow services to connect to the existing LHC site P8 prior to the FCC-hh construction.

* Likely urban development in the close vicinity of the proposed site, with direct views across Geneva to Mont Blanc. These views have been taken into account and building heights have been kept as low as possible, and the overall elevation of the platform has been minimised. To this end, the requirements brief included a target roof elevation no greater than that of the buildings located adjacent to the proposed site.

* The presence of a protected environmental compensation area immediately to the north of the site, an existing development to the south of the site and a major arterial road to the west of the site restricts the available area and layout of buildings within the surface site.

The functional requirements of the surface buildings at PA are similar to those built for previous CERN experiment areas. Some key requirements are:

* A large assembly hall for the pre-assembly of the detector. This building will house at least one crane capable of lowering the detector subcomponents from the surface down to the underground cavern located about 200 m below. The precise crane dimensions and weight will need to be considered during the detailed design phase.

* A shaft head building to accommodate the lifts, cranes, and staircases needed for personnel access to the underground areas and for the movement of material, equipment, and services between the surface and underground areas. This building also houses an unloading bay for trucks transporting material and equipment for installation in the underground areas.

* Buildings to house the equipment necessary to ventilate the underground areas. The equipment for ventilating the experiment cavern is housed separately from that for ventilating the rest of the underground areas, since these two systems enter and exit the underground areas via different shafts. This equipment requires effective noise insulation, therefore these buildings will either be made of reinforced concrete or have specific noise reduction measures incorporated or attached to the building structure.
<figure><img src="image_25.png" /><figcaption>Fig. 1.21 Preliminary simplified surface requirements for PA site</figcaption></figure>

* Buildings to accommodate the compressors and other equipment necessary for the cryogenic systems that will be used by the detector. Similar noise abatement measures to those used for the ventilation buildings will be necessary.

* Cooling plant buildings will include the cooling towers and associated pump houses, basins etc. Although traditionally constructed in reinforced concrete, the use of prefabricated fibreglass reinforced polyester (FRP) may be considered, in which case the civil engineering component would be reduced to the provision of the cooling basin and appropriate supporting foundations, with the towers themselves delivered as part of cooling, mechanical, and electrical infrastructure. In this case, additional noise abatement measures may be needed around these pre-fabricated cooling towers.

* Control building to house offices and control room for the operation of the detector. This building would also house areas for receiving visitors, noting that as PA is the closest FCC experiment area to the CERN main campus, it is likely to be an important focal point for CERN visitors.

* Buildings and support structures for transformers, switches, pylons etc. will be required for the electrical infrastructure.

* Other smaller buildings for various purposes as listed in the PBS given in Table 1.5.

Based on initial conceptual layouts developed by the Fermi National Accelerator Laboratory and evolving requirements for the PA surface site, the conceptual designs have been further refined to develop site layout scenarios, elevations, and earthwork estimates suitable for cost and schedule planning. It should be noted that these representations merely serve early-stage feasibility inputs for planning purposes and have not been reviewed, validated and approved. Figure 1.21 presents a simplified view of the proposed civil engineering buildings and associated works, while Fig. 1.22 illustrates a streamlined cross-section of the site.

One aspect in which PA differs from the other three experiment sites, PD, PG and PJ, is the presence of an existing LHC surface site (P8) in the immediate vicinity. This presents an opportunity to reduce the land required for FCC-hh by re-purposing the existing LHC P8 site after the LHC finishes its physics programme. A technical gallery from the existing site to PA would need to be constructed prior to FCC-hh to connect the services of the two sites together.
<figure><img src="image_26.png" /><figcaption>Fig. 1.22 Preliminary cross-sectional diagram of PA site</figcaption></figure>

<table><caption>**Table 1.6** PBS structure for surface site PB</caption><thead><tr><th colspan="6">PBS Level</th><th rowspan="2">PBS Title</th></tr><tr><th>0</th><th>1</th><th>2</th><th>3</th><th>4</th><th>5</th></tr></thead><tbody><tr><td>5</td><td>3</td><td></td><td></td><td></td><td></td><td>PB Construction, testing, commissioning</td></tr><tr><td>5</td><td>3</td><td>1</td><td></td><td></td><td></td><td>Surface works</td></tr><tr><td>5</td><td>3</td><td>1</td><td>1</td><td></td><td></td><td>Roads, footpaths, parking, fences, gates</td></tr><tr><td>5</td><td>3</td><td>1</td><td>2</td><td></td><td></td><td>Technical galleries</td></tr><tr><td>5</td><td>3</td><td>1</td><td>3</td><td></td><td></td><td>Access control building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>4</td><td></td><td></td><td>Fire fighting equipment and medical station</td></tr><tr><td>5</td><td>3</td><td>1</td><td>5</td><td></td><td></td><td>Shaft head building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>6</td><td></td><td></td><td>Ventilation building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>7</td><td></td><td></td><td>Chilled water production building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>8</td><td></td><td></td><td>Cold box and control Building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>9</td><td></td><td></td><td>Cooling plant Building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>10</td><td></td><td></td><td>SF Annex (demineralised water)</td></tr><tr><td>5</td><td>3</td><td>1</td><td>11</td><td></td><td></td><td>Power converters building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>12</td><td></td><td></td><td>Electrical building</td></tr><tr><td>5</td><td>3</td><td>1</td><td>13</td><td></td><td></td><td>Electrical substation (foundations)</td></tr><tr><td>5</td><td>3</td><td>1</td><td>14</td><td></td><td></td><td>Waste material storage</td></tr></tbody></table>

### 1.3.2 Surface site PB

Site PB is a technical site. At this site, there will be no experiment area, and therefore, civil engineering is limited to the provision of buildings necessary to support the FCC-ee machine and the associated beam absorber, which will be sited in the underground areas of PB. The site also reserves the necessary space for the civil engineering required to accommodate a future hh machine, although these buildings will not be constructed during the FCC-ee phase. The space reserved will be used temporarily during the construction phase to house the civil engineering contractors plant, equipment, material etc. This surface site is the only one planned to be located on Swiss territory. The collaboration with the Fermi National Accelerator Laboratory also studied the need for a technical site, taking PB as an example. Building on the initial work, CERN has developed further layout scenarios for cost and planning purposes.

The product breakdown structure (PBS) for the buildings and associated civil engineering works to be constructed at site PB is given in Table 1.6.

Site PB is one of the smaller technical sites. Nonetheless, its location close to a protected water-course and within sight of nearby residential and agricultural properties will require rigorous integration studies to be carried out. The smooth integration in the existing landscape will be further studied during a subsequent project preparatory phase.

At FCC-ee phase, the principal surface infrastructure at site PB consists of:
<figure><img src="image_27.png" /><figcaption>**Fig. 1.23** Preliminary simplified area requirements for PB surface site</figcaption></figure>

* A shaft head building to accommodate the lifts, cranes, and staircases needed for personnel access to the underground areas and for the movement of material, equipment, and services between the surface and underground areas. This building also houses an unloading bay for trucks bringing material and equipment for transportation via the shaft to the underground areas. This building must be located directly over the associated shaft. The position of this building and the associated shaft could be adjusted within the site boundary to accommodate any changes or additions to the surface requirements and constraints. This building would typically be constructed as a steel-framed building on reinforced concrete foundations and a reinforced concrete slab to sustain the load imposed by the vehicles entering the building for unloading. The building would include a secure access area to ensure appropriate access control to the underground areas.

* A building will be constructed to house the equipment necessary for ventilating the underground areas, including the shaft, access gallery, accelerator tunnel, and beam absorber cavern. As this equipment includes motorised components that may generate noise, the building design will incorporate appropriate noise-reduction measures to ensure that noise levels at the site boundary remain within the required limits. The choice of construction materials and noise mitigation solutions will be determined based on technical and environmental considerations.

* Cooling plant buildings, including the cooling towers and associated pump houses, basins and the demineralised water plant building.

* Various buildings and structures to house electrical equipment, including buildings for power converters and an emergency power system.

* An access control building to house personnel undertaking security and safety operations at the site.

The location of site PB in flat, open countryside requires careful consideration of its integration into the surrounding landscape. To ensure minimal environmental impact, particular attention will be given to architectural and noise mitigation measures, both during the construction phase of FCC-ee and its subsequent operation.

As with site PA, the FCC-ee layout for site PB has taken into account the needs of a future FCC-hh collider, and space has been reserved for the necessary civil engineering. The site boundary fence at the FCC-ee phase will already encompass these future needs.

Figure 1.23 shows a simplified view of the PB surface site. The specific buildings required for FCC-ee are illustrated, along with the necessary space reservations for future FCC-hh civil engineering. A simplified cross-section is shown in Fig. 1.24.
<figure><img src="image_28.png" /><figcaption>**Fig. 1.24** Preliminary simplified cross-section of PB surface site</figcaption></figure>

### 1.3.3 Surface site PD

Site PD has an identical function to site PA, namely, to house an experiment and provide support to the accelerator. As such, the requirements for civil engineering are almost identical, although the specificities of the local terrain and land plots require a different approach to the layout of the site.

The layout of the PD site has a number of constraints that need to be addressed. The main constraint is the planned future extension of the public road network in these areas, which reduces the potential land space for FCC at PD and requires a site access scenario that is compatible with the future layout. After several iterations, a site layout that meets CERN requirements and is compatible with the road development project has been developed. The proposed PD site is located on sloping agricultural land. The elevation change from one end of the site to another is about 20 m. This will require earthworks to be carried out to create a single flat platform on which to site the surface structures.

Other specific features of the site which will need to be addressed after the feasibility study include:

* The scheduling compatibility of the FCC-ee civil engineering works with the planned road extension project

* The proximity of a medical facility to the site will be taken into account in the site's design. Measures such as tree planting and landscaped features may be incorporated to ensure a well-integrated and visually harmonious environment.

* The need to pass under bridges local to the site may result in a limitation on the height of oversized components that can be transported to the site.

A simplified view and section of the civil engineering structures at PD are given in Fig. 1.25 and Fig. 1.26.

### 1.3.4 Surface site PF

PF is a technical access point with surface civil engineering structures similar in function to PB. In order to avoid siting surface buildings within an existing village, the PF surface site is offset by about 600 m from the axis of the accelerator tunnel.

The site is adjacent to a major road, minimising the need for new external roads to access the site. The necessary platform needed for the surface buildings will be of sufficient size to accommodate the future FCC-hh buildings. A simplified view and cross-section of the PF site are given in Fig. 1.27 and Fig. 1.28.

The main constraints at PF relate to the presence of a so-called 'humid zone' in the vicinity of the proposed site. This will require specific attention during the detailed design of the civil engineering structures to ensure that water run-off during the construction and operational phases does not impact this zone.

In summary, the construction of the surface civil engineering required for FCC-ee at PF is considered technically feasible. Particular attention will be given to implementing measures that ensure minimal environmental impact.

### 1.3.5 Surface site PG

PG is an experiment point with civil engineering requirements similar to those of PA. The site is situated on a plateau that is currently partially used for pasture and partially forested. To minimise the impact on the forested area, the surface buildings associated with the cooling plant and some of the electrical systems will be positioned in a secondary location approximately 300 m from the main site. This approach follows the example of the existing
<figure><img src="image_29.png" /><figcaption>Fig. 1.25 Preliminary simplified area requirements for PD surface site</figcaption></figure>

<figure><img src="image_30.png" /><figcaption>Fig. 1.26 Preliminary simplified cross-section of PD surface site</figcaption></figure>

CERN LHC Point 4, where cooling towers and pump stations are located in an area remote from the main site, in this case, to reduce their visual impact. A simplified layout for PG is given in Fig. 1.29 and a simplified cross-section is given in Fig. 1.30.

In addition to mitigating visual impact, the layout of PG will be designed to ensure efficient use of space while maintaining accessibility for operations and maintenance. Noise reduction measures will be implemented where necessary to minimise any potential disturbances to the surrounding environment. Furthermore, efforts will be made to integrate the site harmoniously into the landscape.

### 1.3.6 Surface site PH

PH will be a technical area that will support not only the access and ventilation systems necessary for the accelerator tunnel, but also the infrastructure associated with the RF systems installed at this site.
<figure><img src="image_31.png" /><figcaption>**Fig. 1.27** Preliminary simplified area requirements for PF surface site</figcaption></figure>

<figure><img src="image_32.png" /><figcaption>**Fig. 1.28** Preliminary simplified cross-section of PF surface site</figcaption></figure>

The surface site will have a larger footprint than PB and PF, as the power and cryogenics associated with the RF systems require additional buildings and dedicated foundations for infrastructure such as tanks and transformers.

The layout will be designed to optimise space efficiency while ensuring accessibility for maintenance and operations. Additionally, consideration will be given to minimising environmental impact and integrating the site with its surroundings through appropriate architectural and landscaping measures.

A preliminary simplified layout of PH is given in Fig. 1.31 and a simplified cross-section is given in Fig. 1.32
<figure><img src="image_33.png" /><figcaption>Fig. 1.29 Preliminary simplified area requirements for PG surface site</figcaption></figure>

<figure><img src="image_34.png" /><figcaption>Fig. 1.30 Preliminary simplified cross-section of PG surface site</figcaption></figure>
<figure><img src="image_35.png" /><figcaption>Fig. 1.31 Preliminary simplified area requirements for PH surface site</figcaption></figure>

<figure><img src="image_36.png" /><figcaption>Fig. 1.32 Preliminary simplified cross-section of PH surface site</figcaption></figure>

Site PH is currently located on sloping ground within an agricultural and forested area, with some houses in the near vicinity. This site will require specific studies into the visual impact of the site in order to identify measures that could be taken to reduce its visual impact on the surrounding area.

### 1.3.7 Surface site PJ

PJ will be an experiment area with similar civil engineering structures to those described for site PD. The site is located within agricultural land close to an autoroute. Beyond ensuring that the site is visually integrated into its surroundings, no significant challenges have been identified at this stage. A simplified layout for PJ is given in Fig. 1.33 and a simplified cross-section is given in Fig. 1.34
<figure><img src="image_37.png" /><figcaption>Fig. 1.33 Preliminary simplified area requirements for surface site PJ</figcaption></figure>

<figure><img src="image_38.png" /><figcaption>Fig. 1.34 Preliminary simplified cross-section of site PJ</figcaption></figure>

### 1.3.8 Surface site PL

PL will be a technical area with similar requirements to PH due to the location of the Booster RF systems at this point. The potential presence of an aquifer linked to a potable water supply will need future investigation and if necessary, construction techniques and processes will need to be selected to ensure the aquifer is protected. A simplified layout for PL is given in Fig. 1.35 and a simplified cross-section is given in Fig. 1.36

In summary, preliminary requirements for all eight surface sites have been gathered and **preliminary** plan views and sections have been developed to a level sufficient for costing and planning purposes. The construction of these sites is considered technically feasible. However, a project preparatory phase will need to focus considerable effort to ensure that these sites are carefully integrated into their specific local environments. This process will need to be carried out in close collaboration with appropriate architectural specialists and must include a consultative process with the local inhabitants and other stakeholders. It may be necessary during this process to **adjust and**
<figure><img src="image_39.png" /><figcaption>**Fig. 1.35** Preliminary simplified area requirements for surface site PL</figcaption></figure>

<figure><img src="image_40.png" /><figcaption>**Fig. 1.36** Preliminary simplified cross-section through site PL</figcaption></figure>

**optimise the current preliminary layouts and locations** to achieve an acceptable outcome for all stakeholders that conforms with technical requirements.

## 1.4 Staged approach

An assessment has been made of both the underground and surface civil engineering to identify structures that will only be needed for a subsequent FCC-hh machine and its associated detectors and to classify the identified structures into those for which construction can be deferred until after the completion of FCC-ee physics and those which need to be constructed simultaneously with the civil engineering for the FCC-ee machine. Consideration was given to both the cost and practicality of undertaking civil engineering for FCC-hh in a second stage after the operation of the FCC-ee machine.
1.4.1 Underground structures

Several underground civil engineering structures have been considered for staging as follows:

*Experiment detector caverns*
The experiment detector caverns required for the FCC-hh are almost 100% larger by volume than those required for the FCC-ee detectors. The possibility of constructing the smaller experiment caverns in the initial FCC-ee phase and then enlarging them prior to FCC-hh was investigated. However, this scenario was eventually rejected as a feasible approach since very few of the first-phase structural elements of the cavern would be retained for the second phase, and it would be necessary to demolish the majority of the first-phase works. This would not only be prohibitively expensive and create significant quantities of waste material, but it would also represent a significant risk from a safety perspective since the reinforced rock around the periphery of the smaller FCC-ee cavern would need to be removed and re-supported for the larger FCC-hh caverns.

*Service caverns*
The possibility of undertaking the construction of the service caverns that are adjacent to the experiment caverns at points PA, PD, PG and PJ was also considered. The driver for this was the possibility of co-locating the systems that would traditionally be housed in the service cavern, such as air treatment and demineralised water systems, in the experiment cavern. Alternatively, it was considered only to construct a part of the service cavern for the FCC-ee phase and construct the remaining part necessary for FCC-hh at a second stage. Constructing the second phase would require a complete re-mobilisation of the construction site at the surface and removing all systems from the service cavern and partially, at least, from the machine access shaft. It was eventually concluded that neither a full nor partial staging of the service cavern would bring any major benefits since the cost of relocating the services from one cavern to another and the cost of remobilising the construction site would increase costs considerably compared to completing the service cavern in one stage only.

*Civil engineering for beam absorber*
The beam absorber system for FCC-ee requires only a localised enlargement of the beam tunnel over a length of 708 m. This will be constructed at PB.

The FCC-hh beam absorber system, although not yet fully designed, will be more complex and located at PF. It will require the construction of over two kilometres of additional tunnels, two beam dump caverns and several junction caverns. Since none of the FCC-hh beam absorber structures can be used at FCC-ee phase and given the criticality of PF for the overall construction schedule, it was deemed preferable to defer the construction of the FCC-hh beam absorber civil engineering to a second stage. The downside to this approach will be the need to re-establish a construction site and remove all services from the beam tunnel over several hundred metres on either side of PB. Furthermore, it will not be possible to transport personnel or equipment through the main tunnel in this area for a period of about two years while the FCC-hh beam absorber civil engineering is being carried out.

*FCC-hh transfer tunnels*
The FCC-ee civil engineering includes a single transfer tunnel from the Prévessin site down to the FCC machine. The tunnel bifurcates to provide clock-wise and anti-clockwise injection into the FCC-ee. For a future FCC-hh machine, the pre-injection complex is likely to utilise either the current SPS or LHC tunnels with two new transfer tunnels for the clock-wise and anti-clockwise injection into FCC-hh. In the case that the SPS tunnel is re-configured to house the FCC-hh injector system, then a single additional transfer line with an approximate length of 3000 m and shaft for constructing the tunnel will be required. In the case that the LHC tunnel is re-purposed then two transfer tunnels each of about 2500 m length will be required, each with a single temporary shaft for construction purposes. A tunnel diameter of about 4 m would be required, and connection caverns would be created to connect the transfer tunnels to the FCC main tunnel.

*Additional by-pass tunnels*
The FCC-ee civil engineering only includes by-pass tunnels at the four experiment sites PA, PD, PG, PJ. At the technical sites, by-pass tunnels are not required since a continuous transport corridor can be maintained through the accelerator tunnel.

For FCC-hh there is a possibility that at PB and PH new by-pass galleries may be required in order to avoid the need for personnel to frequently pass through areas of higher radiation (due to the presence of collimators). If a definitive need for these additional by-pass tunnels can be confirmed prior to FCC-ee civil engineering design works being completed, then it may be more efficient to include them at FCC-ee phase. In the case that the need is not fully confirmed, they can be constructed after the FCC-ee machine operation is complete. These would be constructed similarly to the additional by-pass tunnels that were constructed for the LEP 200 upgrade in 1995.

1.4.2 Surface structures

Staging of surface civil engineering for a future FCC-hh presents less technical difficulty than underground civil engineering since access to the construction zones is readily achieved. Although detailed assessments of civil engineering requirements for all eight surface sites have not yet been fully completed, initial studies at points PA and PB suggest that the following buildings could be constructed after FCC-ee physics is completed and before FCC-hh commissioning and operation.
*Assembly halls for FCC-hh detectors elements* Assessments of the assembly space needed for the larger FCC-hh detector elements, such as the superconducting magnet coil, indicate that for at least the two larger detectors, some components will have physical dimensions and weights that will make it impossible to transport them on the existing public roads without modifications to the existing public infrastructure. As such, it is likely that larger spaces and buildings will be required for the associated assembly activities.

This additional space would be required for manufacturing activities that would not normally be carried out at the site, such as coil winding. Since the precise needs for a potential FCC-hh detector are not known at this stage and since there will be at least a 20-year gap between the facilities needed for FCC-ee and FCC-hh detector assembly, it is not considered efficient or necessary to construct the larger facilities already at FCC-ee phase. However, to avoid unnecessary demolition and re-construction work in the future, the necessary space reservation for larger assembly halls will already be made at each of the four experiment sites. The space may be used for easily transferable facilities such as car parks or storage areas, but no complex facilities will be installed within these reserved areas, and, as far as possible, underground utilities will be avoided, including technical galleries.

*Cryoplants* A future FCC-hh machine will require greater cryoplant capacity than during the FCC-ee phase. It is currently expected that the four experiment sites and sites housing RF systems will require cryoplant facilities for the FCC-ee phase. However, a future FCC-hh would require upgraded larger plants at sites PA, PD, PG and PJ as well as new plants at Points PB and PF where no cryoplants are planned for FCC-ee. The same approach as the one adopted for the assembly hall will be taken, whereby space will be kept available and free of FCC-ee infrastructure for the currently expected FCC-hh cryogenics infrastructure. Furthermore, the landscaping and tree planting carried out for FCC-ee will, as far as possible, be executed in a manner that also serves the future FCC-hh needs.

*Cooling and ventilation buildings* Although cooling and ventilation systems will be required at all surface points for the FCC-ee phase, it is currently anticipated that cooling needs for the machine and experiments at FCC-hh will require plant upgrades including a possible increase in the cooling capacity and therefore number of cooling towers. This will be accommodated in the same manner as the cryoplant, with due account taken of potential space needs and visual/acoustic screening for the FCC-ee phase.

## 1.5 Subsurface site investigations

A dependable and comprehensive 3D geological model is essential for assessing the feasibility of underground civil engineering projects. Reliable geological and geotechnical data integrated into the model are required to design tunnels, caverns, and shafts. As the model evolves, the understanding of subsurface geology improves, enabling the identification of potential risks and constraints that could affect these structures. These factors may influence design, costs, and scheduling, making it vital to gather extensive subsurface information during the early stages of planning.

Since the autumn of 2024, CERN has been making a series of subsurface site investigations (SSI) using a combination of data acquisition methods. Once complete, the information obtained from these SSI will be used to enhance confidence in the 3D geological model for the FCC study area. The phase one SSI is currently about 40% complete, and the preliminary results are positive when compared to the model's predictions.

### 1.5.1 Geology in the region

For the purposes of the feasibility study and the targeted depths of the underground infrastructure, CERN has considered that the Geneva region features three primary geological strata: moraines, molasse, and limestone. A plan view of the Geneva basin geology is shown in Fig. 1.37.

The glacial moraines, characterised by their low strength, overlay the sedimentary molasse, which consists of horizontally bedded layers of marl and sandstone that vary significantly in strength. The thickness of the moraines ranges from just a few metres to over 100 metres. Bordering and intersecting the molasse are limestone formations, including the Alpine foothills and the Jura, Vuache and Salève chains. Limestone in the Jura and Vuache foothills can potentially contain karsts caused by chemical weathering. These karsts, often filled with water and sediment, can lead to water inflow and structural instability if encountered during excavation.

Beneath Lake Geneva, prior investigations have revealed very soft deposits, including lacustrine clayey silts and glacial-lacustrine silts and clays, with compressive strengths ranging between 2 MPa and 10 MPa. These deposits extend from the lakebed to approximately 260 metres in depth. Limited data exists for the Arve and Rhône Valleys, but soft deposits, including alluvial and alluvial-glacial moraines, are expected to reach depths of up to 100 metres. To mitigate construction risks and reduce water inflow challenges, the tunnel alignment has been situated at a depth that is expected to remain entirely below the moraines.
<figure><img src="image_41.png" /><figcaption>**Fig. 1.38** FCC long geological profile</figcaption></figure>

The molasse is composed of horizontally bedded layers of marl and sandstones. These layers can vary in strength but are considered to be mostly stable and dry. Molasse is generally considered a favourable geological stratum for tunnel boring machine excavation. For large-span caverns, constructing in stronger sandstone layers is preferable. The objective throughout the feasibility study has been to locate underground infrastructure within the molasse, as can be seen in Fig. 1.38, wherever possible.

### 1.5.2 Development of geological 3D model

Within the feasibility study, one of the primary objectives was to identify and locate the interfaces between the moraines and the molasse, and between the molasse and the limestone more precisely. Although data on the individual sub-strata of each layer exists, its quality is inconsistent and does not currently allow a clear separation of the moraines, molasse, and limestone into distinct sub-layers.

In collaboration with the University of Geneva (UNIGE) and specialist consultants from CERN's Member States, CERN has been developing a 3D geological model. This model is based on data from previous borehole investigations, geophysical surveys in the study region and the ongoing SSI campaign. Urban areas such as Geneva and its suburbs benefit from numerous logged boreholes, which provide a high level of confidence for the upper 50 metres of the subsurface. In contrast, rural areas have fewer logged boreholes, and certain locations, such as the foot of the Bornes and Mandallaz limestone outcrops, extend several kilometres without relevant geological data at the depths where the FCC underground infrastructure is proposed.

To improve understanding of the geological conditions along the proposed FCC tunnel, a targeted subsurface investigation campaign has been designed and is currently underway in areas of greatest geological uncertainty.
This campaign, which commenced in October 2024 and will continue until December 2025, combines geophysical surveys with deep borehole drilling. Geophysical surveys are first conducted using seismic refraction to examine shallow strata and seismic reflection to explore deeper layers. The collected data is then processed and interpreted to guide targeted drilling at depths ranging from 70 to 500 metres. By integrating these complementary methods, the reliability of the geological model in previously uncertain areas is significantly enhanced. This, in turn, increases confidence in the estimated construction costs and schedules, provides valuable information for the preliminary civil engineering design stage, and establishes key geological and geotechnical parameters prior to more targeted investigation campaigns.

Once the updated geological model is finalised, it, along with all individual borehole logs and geophysical interpretations, will be made publicly available. This data will contribute to a broader understanding of the geology in the region of the FCC, serve as a foundation for academic research, and potentially support future infrastructure projects beyond the FCC.

### 1.5.3 Phase 1 subsurface site investigations

To identify the site investigation to undertake in the first phase, three main criteria were considered:

1. Areas where there is a risk of the tunnel crossing the molasse interface into moraines or limestones.

2. Areas where crossing limestone is unavoidable.

3. Areas where there is a complete lack of relevant geological information.

Using these three criteria, the phase one SSI campaign has been divided into nine separate sections namely; Jura 1, Jura 2, Lake, Arve, Bornes, Mandallaz, Usses, Vuache and the Rhône.

The individual sections depicted in Fig. 1.39 each present unique uncertainties and challenges. The following sections will describe the current uncertainties in each area, explain the objectives of the subsurface investigations, and present the preliminary results from the investigations already completed.

Jura 1 Section Jura 1 is situated at the base of the predominantly limestone Jura mountain range, extending for approximately eight kilometres from Challex in France in the south to Satigny near CERN in Switzerland in the north. The proposed alignment is located at depths ranging from about 140 metres beneath the Allondon Valley at its shallowest point to 250 metres at its deepest on either side of the valley.

The understanding of the subsurface conditions in this section has been enhanced through recent investigations by other parties. In 2021, an extensive campaign of 2D and 3D geophysical investigations was conducted by the Canton de Geneve and the Services Industrial de Geneve as part of the GEothermies programme. Additionally, borehole data obtained near Satigny clearly identified the molasse-limestone interface, and encountered artesian water flows near this interface. The data from this campaign was incorporated into a 3D geological model developed in collaboration with UNIGE, which allowed a reduction in the planned scope of further investigations and provided an updated prediction that, in the northern part of the section, the limestone is located at a greater depth than previously expected.

Despite these advances, residual uncertainties remain—most notably in accurately defining the interface between the limestone and the molasse. As confidence in the updated data diminishes toward the southern portion of the section, further subsurface investigations remain necessary. Such investigations are required to confirm the current hypotheses and to ensure that the tunnel and associated underground infrastructure avoid limestone wherever feasible, thus mitigating the risks associated with unforeseen high water pressures and challenges associated with tunnelling in limestone.

The SSI in Jura 1 are scheduled to begin in mid-2025 and will continue until the end of 2025. The following is planned:

* thirteen boreholes ranging from 230-270 m in depth:

* one fully cored

* twelve destructive and cored

* three boreholes are optional, depending on the results achieved from geophysics and adjacent boreholes

* 13 high-resolution seismic reflection profiles with a total length of 23,510 m

The locations of the SSI in the section Jura 1 are shown in Fig. 1.40.

Jura 2 Section Jura 2 is located between Lake Geneva and the base of the Jura mountains, extending approximately three km from Meyrin in Switzerland to Fernet-Voltaire in France. The civil engineering infrastructure in this area is planned to be situated at about 200 m below the surface. At this depth, 3D geological models indicate the potential for limestone to be present near the tunnel and primary infrastructure, similar to the risks identified in Jura 1.
<figure><img src="image_42.png" /><figcaption>**Fig. 1.39** Areas of geological uncertainty</figcaption></figure>

Recent improvements in understanding have been achieved by incorporating seismic data from the nearby *GEothermies* programme into the geological models. This updated information suggests that the top of the limestone is deeper than predicted.

The targeted SSI will enable further improvements to the understanding of the molasse-limestone interface.

The following SSI is planned to start in mid-2025 and will last until late 2025:

* three boreholes ranging from 240-250 m in depth.

* one destructive and partially cored.

* one fully cored.

* one optional destructive and partially cored depending on the results of the geophysics and adjacent boreholes.

* 7300 m of high-resolution reflection seismic geophysics.

The locations of the proposed SSI are shown in Fig. 1.41.
<figure><img src="image_43.png" /><figcaption>**Fig. 1.40** Jura 1 section showing the locations of the investigations</figcaption></figure>

<figure><img src="image_44.png" /><figcaption>**Fig. 1.41** Jura 2 section showing the locations of the investigations</figcaption></figure>
<figure><img src="image_45.png" /><figcaption>**Fig. 1.42** Lake section showing the locations of the investigations</figcaption></figure>

*Lake* Under Lake Geneva, the proposed FCC tunnel is at a depth of approximately 100 m below the bottom of the lake. The subsurface geology is characterised by moraines of mixed characteristics; however, the absence of pre-existing borehole data in this area has led to uncertainty in the geological model.

Improvements in understanding have been achieved by incorporating data from the GEothermies programme (acquired south of the proposed alignment) into the 3D geological model. Although this data does not clearly define the interface between the moraines and the underlying molasse to the north where the proposed FCC tunnel is foreseen, it does indicate that the interface is located at a higher depth than previously considered.

Avoidance of the moraines is considered a key design priority, as tunnelling in water-bearing moraines can be challenging. This will be confirmed after the SSI campaign.

The following SSI is planned to start in mid-2025 and will last until late 2025:

* four fully cored boreholes ranging from 130-180 m in depth.

* 16,340 m of offshore seismic reflection.

The locations of the proposed SSI are shown in Fig. 1.42.

*Arve* The Arve section, located at the eastern extremity of the proposed FCC tunnel, extends approximately eight km in length, with the proposed FCC tunnel depth varying between 140 and 170 m. Situated within the Arve Valley and adjacent to the Arve River, the area is known to be made up of a mixture of molasse and glacial moraines near the surface, although geological data at the proposed FCC tunnel depths is limited.

Further investigations will confirm the depth of the molasse-moraine interface and ensure that the tunnel remains within the molasse, thereby avoiding the potentially water-bearing moraines.

The following SSI is planned to start in early 2025 and will last until mid-2025:

* five destructive and cored boreholes totalling 990 m in depth.

* Up to three of these boreholes may not be undertaken following results from geophysics.

* three high-resolution seismic reflection lines totalling, 13,150 m.

The locations of the proposed SSI are shown in Fig. 1.43.

*Bornes* The area adjacent to the Bornes Plateau is the deepest section of the project, with depths ranging from 500 to 560 m over five km. The deepest access shaft at PF, approximately 400 m deep, is also located within this section.
<figure><img src="image_46.png" /><figcaption>**Fig. 1.43** Arve section showing the location of the investigations</figcaption></figure>

The proposed FCC tunnel will remain within the molasse, as the limestone is situated much deeper—nearly 1000 m below the surface. However, little is known about the characteristics and quality of the molasse. Additionally, thrusts, faults, and potential tectonic materials have been identified in the region.

Given these factors and the high overburden, further investigations are required to obtain detailed information on the molasse and reduce geological uncertainties in this sector.

The following SSI is planned to start in early 2025 and will last until mid-2025:

* one fully cored borehole totalling 425 m in depth.

The locations for the SSI are shown in Fig. 1.44.

*Mandallaz* The Mandallaz is an anticline limestone range characterised by faulting and thrusting over the underlying molasse on its western side. Little detailed geotechnical information was available prior to the start of the SSI campaign. This presented uncertainties regarding the extent of the limestone and the nature of its structure.

Improvements in understanding have been achieved through geophysical investigations as part of the SSI. Data acquisition has been completed, and provisional interpretations indicate that the limestone at the depth of the proposed FCC tunnel is narrower than modelled before the campaign. This revised interpretation suggests that the section requiring tunnelling through limestone is shorter than initially foreseen. Additionally, preliminary borehole data have revealed the presence of small karsts and traces of hydrocarbons, and provisional geophysical interpretations have identified an east-west strike-slip fault across the Mandallaz mountains, although this has yet to be confirmed by the boreholes.

The following SSI has been carried out or is taking place:

* three fully cored boreholes totalling 1240 m in depth

* one of these boreholes is inclined at 30° from vertical

* one of these boreholes may not be required to be undertaken following the results of the first two boreholes.

* three high-resolution seismic reflection lines totalling, 5100 m.

The locations for this SSI are shown in Fig. 1.45.

*Usses* The Usses, a small section extending roughly one km, is where the proposed FCC tunnel is closest to the surface, with about 50 m of cover above the tunnel at the lowest point in the Usses Valley.
<figure><img src="image_47.png" /><figcaption>Fig. 1.44 Bornes section showing the locations of the investigations</figcaption></figure>

<figure><img src="image_48.png" /><figcaption>Fig. 1.45 Mandallaz section showing the locations of the investigations</figcaption></figure>
<figure><img src="image_49.png" /><figcaption>**Fig. 1.46** Usses section showing the locations of the investigations</figcaption></figure>

On-site investigations have improved the understanding of the subsurface conditions in this sector. All data acquisition has been completed, and the final interpretation of the geophysical data is underway. Borehole results indicate that the moraine-molasse interface is encountered at 15 m, shallower than modelled, suggesting that the proposed tunnel does not intrude into water-bearing moraines beneath the Usses River. This will be confirmed once the final geophysical interpretations are complete and compared against the borehole log.

The following SSI has been undertaken:

* one fully cored borehole of 70 m.

* two seismic refraction lines totalling 780 m, the first performed using an explosive source and the second utilising a weight drop source.

* one very high-resolution seismic reflection of 770 m in length.

The locations for the SSI are shown in Fig. 1.46.

*Vuache* The Vuache section at the southwestern extent of the proposed FCC tunnel extends over approximately four km, with proposed tunnel depths ranging from 190 to 300 m and an average depth of around 250 m. The Vuache mountain range, primarily an anticline structure bounded by thrust faults, underlies this section, with the prominent Vuache Fault located to its south-west. The geology is dominated by Jurassic-Cretaceous limestones and marls, overlain by the typical molasse found elsewhere in the Geneva basin.

Geo-physical investigations carried out as part of the SSI have improved the understanding of the subsurface conditions. One completed borehole has confirmed that molasse is present to about 30 m below the tunnel. The ongoing analysis of the geophysical data, along with additional borehole results, will identify whether this is also the case for the remainder of the section.

The following SSI has been carried out or is taking place:

* five destructive and partially cored boreholes totalling 1270 m in depth.

◦ two of these will be optional, depending on the conclusions of the geophysics.

* five high-resolution seismic reflection lines totalling, 9370 m.

The locations of the SSI are shown in Fig. 1.47.

*Rhône* In the Rhône Valley, the proposed FCC tunnel is located approximately 50 m below the surface under the Rhône River and the environmentally sensitive Marais de l'Etournel. The overlying soils are predominantly
<figure><img src="image_50.png" /><figcaption>Fig. 1.47 Vuache section showing the locations of the investigations</figcaption></figure>

composed of moraine or alluvial sands, gravels and boulders, and the area was formerly quarried as a source of gravel. These layers are saturated due to the influence of the Rhône River.

The current geological model predicts that the tunnel is situated entirely within the molasse, although the interface between the molasse and the overlying moraine is predicted to be close. While limited available data has allowed this initial interpretation, the scarcity of detailed geotechnical information limits its precision.

As a result, further investigations are required to accurately define the moraine–molasse interface and confirm that the proposed FCC tunnel remains fully within the molasse, thereby mitigating potential risks associated with the water-bearing overlying layers.

The following SSI could start in mid-2025 and finish by late-2025:

* six destructive and partially cored boreholes totalling 765 m in depth.

* Four of these boreholes may not be required following results from geophysics.

* eleven geophysics seismic lines.

* four profiles of high-resolution seismic reflection totalling 4920 m towards the upper part of the valley.

* four profiles of very high-resolution seismic reflection totalling 2990 m towards the bottom of the valley.

* four profiles of seismic refraction at the bottom of the valley using a weight drop source, totalling 240 m.

* five high-resolution seismic reflection lines totalling 9370 m.

The locations of the SSI are shown in Fig. 1.48.

### 1.5.4 Phase 2 sub-surface site investigations

After the completion of the first phase of the SSI at the end of 2025, a geotechnical and civil engineering specialist may be contracted in early 2026—subject to the decision-making process—to analyze the campaign results and the corresponding geological model. Working in collaboration with CERN, this specialist would define the scope and technical specifications for the second phase of the sub-surface site investigation and oversee the on-site operations.

This second phase would focus primarily on obtaining the necessary geotechnical data for the detailed design of all underground and surface works to be undertaken. In particular, the second phase would focus on the sites where experiment and service caverns are required since these require very detailed knowledge of the lithology and rock engineering properties in order to undertake the complex numerical analysis required to define the rock support necessary to create stable underground structures.
<figure><img src="image_51.png" /><figcaption>**Fig. 1.48** Rhône section showing the location of the investigations</figcaption></figure>

<figure><img src="image_52.png" /><figcaption>**Fig. 1.49** Example of targeted borehole investigations for experiment cavern complexes</figcaption></figure>

*Detailed Investigations Around Key Infrastructure* Precise geological, geotechnical, and hydrogeological data are essential for the effective design of both experiment and service caverns, which are typically located at depths of several hundred metres. This information ensures structural integrity and supports the selection of appropriate construction methodologies. An indicative example of a typical drilling configuration can be observed in Fig. 1.49.

These boreholes will accurately characterise the molasse at the cavern depth, identifying structural features such as fractures and weak zones that could affect cavern stability. Core samples and in-situ testing will determine the molasse's strength, deformability, and stress state, enabling precise structural analyses and the design of appropriate excavation and support systems. In addition, data on groundwater levels, permeability, and pore pressures will inform dewatering plans and help manage water ingress - factors critical to ensuring safety and stability during and after construction. Consequently, the borehole data from this campaign will be essential for optimising excavation methods, reducing risks, and estimating construction costs accurately.
<figure><img src="image_53.png" /><figcaption>**Fig. 1.50** Fault map of FCC study area</figcaption></figure>

### 1.5.5 Fault Mapping and Seismic Modelling

The FCC study region is known to contain active or potentially active faults, including the Vuache Fault. Historical seismic events have provided valuable insights into the area's seismic behaviour.

While detailed study of seismic activity and structural faulting was not the primary focus of the first phase of the SSI, CERN, in collaboration with the University of Geneva, has utilised historical data to identify the main fault zones in the region, as shown in Fig. 1.50.

The proposed FCC tunnel is expected to pass through a zone with faulting, as illustrated in Fig. 1.51. In areas such as the Mandallaz and Jura sections, where faults are known to be present, further refinement of fault characterisation will be possible once the fully processed results from the phase one SSI campaign become available. This will continue to be developed in collaboration with external partners over the coming years.

### 1.5.6 Summary of the Subsurface Site Investigations

The subsurface site investigations that have already been carried out as part of Phase One have improved the reliability of the 3D geological model for the proposed FCC tunnel. The preliminary results from investigations in the key sections of Mandallaz, Usses, Vuache and Arve have been integrated into the model, and early results show promising signs that the FCC tunnel would be located within the molasse except in the Mandallaz section, where crossing the limestone is unavoidable.

The results from the remainder of the campaign will need to be fully acquired and processed before any definitive conclusions on the precise elevation of the tunnel can be made. However, current indications are that the tunnel might be shallower than currently planned. This would allow an overall reduction in shaft depth, reducing the impact and, therefore, have positive cost and schedule implications
<figure><img src="image_54.png" /><figcaption>Fig. 1.51 FCC long profile with potential faults</figcaption></figure>

## 1.6 Management of excavated materials

### 1.6.1 Introduction

Building the underground infrastructures of the Future Circular Collider (FCC) in the Franco-Geneva Basin would produce approximately 6.3 million cubic metres of excavated materials, mainly constituted by molasse, a soft heterogeneous rock (96%).

The management of excavated material stands as a key element in the realisation of the FCC within the local region. Furthemore, it exemplifies a visionary investment designed to reduce environmental impact and unlock benefits that extend well beyond the local context. Accordingly, from the earliest stages, an approach to the strategy for the excavated material management was incorporated into the feasibility study as part of the FCCIS project, co-funded by the EU under the H2020 programme (grant agreement no. 951754).

The French tunnel design centre, (CETU), the Centre for studies and expertise on risks, environment, mobility and urban planning, (CEREMA), the Montanuniversität Leoben (Austria) collaborated with the FCC study on this subject. Technical information and legislations were provided by the Swiss cantonal ‘Service de géologie, sols et déchets’ (GESDEC).

Current regulations still consider excavated materials as waste as soon as they exit the project boundaries, but the legislation is evolving in many European Countries. Excavated materials can be reused on-site (prevention of waste production) or recovered off-site. Final disposal as waste must be the last option when no reasonable recovery (even after suitable preparation or treatment) is possible. The successful management and use of excavated materials strongly depend on the early implementation of a management strategy shared and agreed upon with the Host States by the project owner.

The presentation of a management plan of the excavated materials is considered to be the responsibility of the future project owner, irrespective of who implements the actual tasks. To satisfy this requirement, a report outlining the approach to the strategy for the management of the excavated material (in French ‘Stratégie de gestion et d’usage des matériaux excavés’ [1] also available in English [2]) was developed. The following aspects are included:

* Quantities of excavated materials and current knowledge of the geological characteristics.

* General principles for the management of the materials.

* Identification of the potential risks.

* Legal framework in the two Host States.

* Potential reuse cases.

### 1.6.2 The excavated material quantities

The FCC excavation work is estimated to generate approximately 6.3 million cubic metres of excavated material, equal to approximately 8.2 million cubic metres of expanded material over nearly a decade. The quantities of
<figure><img src="image_55.png" /><figcaption>**Fig. 1.52** Geological profile along the FCC path. The part of the tunnel under French territory is shown in blue; the part under Swiss territory is shown in red</figcaption></figure>

excavated materials (see Table 1.4) were calculated on the planned design of the underground structures (shafts, tunnels, caverns, alcoves, etc.). They correspond to the materials in place and the expanded materials (applying an expansion factor of 1.3).

### 1.6.3 The excavated material characteristics

The material extracted will mostly comprise different types of heterogeneous soft rocks, called molasse (96%), along with limestone (2.5%) and quaternary deposits (1.5%).

The molasse is formed by a series of horizontal layers of cemented and silty sandstone interspersed with layers of marl and argillaceous rocks. Geogenic anomalies such as the presence of natural hydrocarbons or enhanced concentration of metals including nickel and chromium may exist naturally in varying quantities in parts of the various molasse layers.

The Lemanic basin features three main geological groups: quaternary formations (glaciolacustrine, fluvio-glacial and moraines), molasse and limestone bedrock. The reference placement proposed for the FCC has been optimised to place the tunnel infrastructure in the Franco-Geneva molasse basin (Fig. 1.52). The limestone elements of the Jura and Vuache mountains, along with the Mandallaz and Salève ranges, skirt and intersect the molasse layers. It is hard to excavate limestone in the region due to its karstic characteristics caused by chemical alteration of the rock. These deep karsts are likely filled with water and unconsolidated materials, which could penetrate the excavation because of strong water pressure. CERN experienced these effects when conducting excavations in the limestone of the Geneva region during previous projects (e.g., LEP in the '80 s). Because of these difficulties, the design deliberately avoids the Jura and the limestone of the Vuache. However, despite every effort to minimise crossing limestone strata, one stretch of the proposed tunnel still passes through the Mandallaz limestone.

The molasse in the region is generally made up as follows:

* 30 to 50% clay,

* 10 to 15% silt,

* 10 to 15% sand, with a grain size of between 63 µm and 4 mm,

* 15 to 20% sandstone particles larger than 4 mm.

The sandstones (detrital sedimentary rocks formed from grains of sand cemented by silica, calcite and iron oxide) in the Lake Geneva region are mainly made up of:

* 40 to 70% quartz,

* 20 to 45% calcite,

* 5 to 10% feldspar,

* 5 to 20% phyllosilicates (micas, chlorites, serpentinite, etc.)

The marls (sedimentary rocks containing clay and limestone) present in the region exhibit a wide variety of compositions. Marls are ductile, micro-cracked and subject to swelling following contact with air or significant changes in soil moisture.

The nature of the excavated materials depends on the longitudinal profile of the geological structures encountered. Different formations and different facies may be encountered. Homogeneity in terms of the nature and properties of the excavated materials is a key consideration, as it will determine their subsequent use.

A strategy will have to be devised during the construction phase to select the materials to be reused, based on the following:

* Initial visual selection at the face.

* Tests on the geological formations and updates in case of changes in petrographic properties or indications of lithological changes.
* Rapid and effective material quality control as soon as possible after the extraction of the material, or at the latest when the material reaches the surface.

Specific investigations would be required prior to the start of the excavation to determine the geological characteristics of the subsurface through which the FCC will pass and to assess the potential geological risks. CERN is conducting an initial investigation campaign (2024 - 2025) as part of the FCC feasibility studies. These first subsurface investigations could be later complemented by extensive subsurface investigations, devoted mainly to confirming the geological model and, therefore, to anticipating the possible risks and preparing adequate mitigation. Laboratory tests are being conducted on core samples extracted during the subsurface investigations to identify and characterise the rocks in view of their potential for reuse and to analyse the presence of geogenic anomalies.

### 1.6.4 Approach to the management of excavated materials and associated risks

Defining what could constitute a basis for a future strategy for managing and utilising excavated materials is a key feasibility criterion for the FCC study, reflecting both the alignment with the regulations of the Host States and a broader commitment to sustainability and environmental stewardship. The basic concept has been documented in a stand-alone deliverable of the FCCIS study [1]. The core principles, summarised here, present the high-level aspects, related constraints and the opportunities identified for treating the material as a resource instead of disposing of it as waste.

The approach to excavated materials management marks the initial step toward a comprehensive approach, conducted in accordance with the regulatory frameworks of both Host States. Its implementation, in the form of a preliminary operational management plan, can only begin once the first set of subsurface investigations is completed (by the end of 2025). Subsequently, this preliminary plan should be revised whenever significant new information is obtained, following an iterative process that would culminate in a final operational management plan to be shared and agreed with the Host States, and should be adopted before the start of excavation.

**Approach to the excavated material strategy** The studies carried out to develop an approach to the excavated material strategy were:

* Iterative development of a 3D subsurface geological model (see Sect. 1.5.2).

* Inventory of the regional opportunities for reuse in France and Switzerland.

* Investigation of the possible connection to the regional railway network.

* Investigation of the possible connection of the railway sidings to the extraction sites by conveyor belts, to avoid local nuisances due to truck transport.

The FCC schedule allows the possibility of optimising potential reuse scenarios. Accordingly, rather than centring on fixed solutions, the excavated materials management focuses on flexible approaches and guiding principles that can be adapted to accommodate:

* Evolutions in technology that could result in improvements in the techniques applied to the excavation and separation and treatment of the excavated materials.

* New recovery pathways which are better suited to the characteristics of the extracted materials that may become available in the future.

* Evolution of regulations governing the management of excavated materials for specific applications (e.g., use as soil improvers in agriculture).

The main parameters to be taken into consideration when building a strategy for the management of the excavated materials are:

* TBM kinematics (Fig. 1.4) and the logistic aspects that determine the output and availability of excavated materials within the area as well as the nearby storage and treatment areas required.

* Identified uses and streams: specifications, demand (quantities and variation over time), location, accessibility and service, criteria for acceptance of the material.

* Modes of transport and distances, as well as whether existing infrastructures can be used or whether new infrastructures will need to be built.

A schematic overview of the approach to the excavated materials management appears in Fig. 1.53. Experience from previous CERN projects shows that the proportion of materials affected by geogenic anomalies (such as hydrocarbons or elevated chromium and nickel levels) may vary, ranging from approximately 15% to 45%, in part due to different regulatory thresholds of the Host States. For the record, exemptions have been granted for specific materials, for example, in 2019, during the HL-LHC project, to facilitate higher recovery rates in various recovery streams.
<figure><img src="image_56.png" /><figcaption>**Fig. 1.53** Schematic diagram of the scenarios defined for the excavated material strategy. (not including transport)</figcaption></figure>

*Evaluation of risk in the management of excavated materials* The fraction of re-usable excavated materials depends on the geochemical, mineralogical and geotechnical properties of the materials excavated from the tunnel. When preparing a management plan for these materials, particular attention must be paid to the management of both technical and non-technical risks, which have a direct effect on limiting costs, optimising transport and avoiding compromising the schedule. Typical technical risks relating to the external context for excavated materials are associated with:

* The nature of the materials, which determines their classification as a specific type of material and their potential reuse;

* The proportion of facies, in the case of a heterogeneous formation or a mixed facies with several types of material;

* The position of the contacts between geological formations, which has an impact on the distribution of the volume of material per formation.

The technical risks of the internal context, regarded as points to keep in mind by the project owner, are associated with:

* The impact of the excavation methods, chosen according to the characteristics of the excavated materials and, in particular, the additives necessary for the excavation, which can potentially pollute the materials and hinder certain reuse cases.

* The equipment used in the transport and in the treatment of the excavated materials, for the potential of unforeseen mixing and potential pollution of the excavated materials.

* The availability and extent of the temporary and final storage areas for excavated materials.

Along with the technical risks, non-technical challenges, such as political or administrative factors, should also be taken into account in the development plan. For example, there may be modifications to environmental regulations. These non-technical challenges must be considered from the study phase.

Excavation methods can have an impact on the potential use of molasse and other excavated materials, since they can alter their properties and quality. At this stage of the FCC study, the use of shielded Tunnel Boring Machines (TBMs) is likely to be possible for most of the main tunnel. Further studies should provide more detail for the data provided in Table 1.7, specifying the impact of the chosen excavation techniques on the quality of the excavated materials (type of TBM, explosives or road header).

### 1.6.5 Regulatory frameworks

In France, AFTES recommendation GT35R1F2 on the management and use of excavated materials [3] and the CETU information document on naturally occurring geological materials excavated in underground structures [4] are the main reference texts for the management of excavated materials.
<table><caption>**Table 1.7** Quantity of excavated material by excavation method</caption><thead><tr><th></th><th>Using TBMs</th><th>Using conventional method</th><th>Shafts</th><th>Total</th></tr></thead><tbody><tr><td>Collider infrastructure (m³, in situ)</td><td>2,689,500</td><td>2,828,500</td><td>652,600</td><td>6,170,600</td></tr><tr><td>Connecting infrastructure to existing tunnels (injection) (m³, in situ)</td><td>97,900</td><td>9800</td><td>14,600</td><td>122,300</td></tr><tr><td>Total (m³, in situ)</td><td>2,787,400</td><td>2,838,300</td><td>667,200</td><td>6,292,900</td></tr><tr><td>Percentage of Total</td><td>44%</td><td>45%</td><td>11%</td><td>100%</td></tr></tbody></table>

In Switzerland, the ordinance on the avoidance and the disposal of waste [5], complemented by the ordinance on the movement of waste [6], the ‘Aide à l’execution relative à l’OLED’ (help for the execution of the ADWO, not available in English) and the ‘Guide pour la réutilisation des matériaux d’excavation non pollués’ (guide to the reuse of unpolluted excavated materials, OCEV), provide the framework for the subsequent steps.

The main regulations in force in the two Host States regarding the application of international agreements on the export of excavated materials are:

* In Switzerland, Article 15, paragraph 1 of VeVA 814.610 requires that anyone exporting waste (including unpolluted excavated materials) must obtain authorisation from the Federal Office for the Environment (VeVA 814.610, 2005).

* In France, since 12 July 2007, the cross-border movement of waste has been subject to the provisions of Regulation (EC) No 1013/2006 of 14 June 2006, which incorporates the provisions of the Basel Convention [7]:

- Article 43 permits the importing of waste for the purposes of recovery from countries which are Parties to the Basel Convention to a European country.

- Articles 40 and 41 prohibit the importing of waste for the purposes of disposal from countries which are Parties to the Basel Convention except where one of the countries (including Switzerland) presents a prior duly reasoned request (paragraph 4).

Article 4.2 of the Basel Convention [7] states that each country must take measures to reduce the generation of waste and ensure the availability of adequate disposal facilities located, where possible, within the country, with a view to the environmentally sound management of dangerous waste and other waste, whatever the place of its disposal.

In the north-west sector of the FCC, its path crosses the Franco-Swiss border at several points. If the excavated materials were to be managed by each state, this would lead to the excavation of additional shafts for the specific purpose of material evacuation, which is not realistic and does not respect the ‘avoid, reduce and compensate’ approach because it would increase the quantity of materials to be managed and the number of nuisance zones on the surface due to the extraction points. For this reason, it would be desirable to propose the adoption of the principle of each state managing the equivalent mass of spoil excavated on its territory. This adjustment, which remains to be agreed with the two Host States and in association with CERN, would make it possible to deal with the small enclaves that cannot be managed by the TBMs without changing the principle of division laid down in the Basel Convention.

A further point where an agreement between the project owner and the Host States seems appropriate concerns the country in which the materials are extracted. In principle, according to the Basel Convention, each country is responsible for extracting and managing its share of the mass on its territory and for dealing with the associated adverse effects (dust, noise, traffic, etc.). The distribution of the TBMs, however, does not necessarily correspond to this mass distribution (e.g., no TBM launched from site PB) for technical reasons. For such a scenario, compensatory measures will have to be agreed with and by the Host States.

Various tools will have to be developed to ensure that the management of the materials respects an established and agreed management plan that is part of the project authorisation files. These will have to be devised sufficiently early, in consultation with the Host States and relevant authorities, to ensure they are properly implemented when the time comes:

* Administrative tools for the authorisation procedures for spoil transport and storage to enable effective recovery of the material.

* Regulatory tools to enable the validation of the innovative processes, particularly in terms of characterisation, and to ensure they can be standardised.

* Cross-border agreements: if relevant optimisations are identified, these will need to be made explicit, substantiated and submitted for joint approval by the two Host States.

* Agreements with offtakers of materials and owners of land plots that would receive materials before the start of the excavation process.
* Logistics tools: an adequate traceability system is the responsibility of the owner and it provides a useful way of improving the recovery of the materials and acts as a guarantee that the spoil is of sufficiently high quality.

The first three points could be governed by a bilateral international agreement.

Materials excavated during underground works are considered as ‘waste’ in the European Union (EU) countries and Switzerland unless they can be reused on the site of the project. The definition of the status of excavated soil and its classification as ‘waste’ or ‘non-waste’ are fundamental aspects, as they determine the legal framework to be followed for managing the excavated materials. The status of the excavated soil must be specified according to the various on- and off-site management scenarios with the French and Swiss authorities.

To develop an integrated plan for the management of the excavated materials that is part of the authorisation process, it would be advisable that the FCC is treated as a single indivisible and transnational project in the meaning of 1.c) of Article 2 of the ‘waste’ directive 2008/98/EC of 19 November 2008 [8]. The integrated approach facilitates the development of the agreements between the project owners and the customers for the materials that must be in place before the construction works start. It also enables the possibility to reuse materials on either side of the border, independent of their extraction site of the unique, indivisible project.

### 1.6.6 Scenarios envisaged for the management of the excavated materials

As a long-term project offering sufficient lead time, the FCC may represent an opportunity to develop innovative approaches for the management of excavated materials. For this reason, the study invested already in launching the research and development of new technologies and solutions that have the potential to reduce the amount of waste that needs to be transported to deposit sites.

The identification of uses must comply with the waste hierarchy put forward by the European Union parliament (‘waste’ Directive 2008/98/EC) and implemented in the French and Swiss regulations. The national policy for the prevention of waste production and reduction of waste impacts, outlined in the Environment Code (Art. L-541-1), supports the transition to a more sustainable management of the excavated materials, by fostering the application of the waste hierarchy: avoid waste production (including reuse), preparation for reuse, recovery and disposal. It also includes achieving a total ‘material’ recovery of the waste stemming from the building and public works sector of 70%. This target is evaluated at the regional level.

The general principle of avoid/reduce/compensate will also be applied to the management of excavated materials of the FCC: the ‘avoid’ and ‘reduce’ principles are applied mainly at the time of the subsurface infrastructure planning (i.e. avoiding producing unnecessary spoil and reducing the overall excavations by optimising location, design, and depth of underground infrastructures) and in the choice of the excavation methods (minimisation of pollutants during the excavation, thus reducing the quantities of excavated materials that will need specific land filling).

The various types of reuses and recovery calls for material storage and treatment areas close to the extraction sites. The surface areas necessary depend on the detailed technical concept of the construction work, the construction schedule and the dimensional design of the treatment unit on the sites. These elements will have to be developed at a later stage.

Among the identified pathways, the most likely to be realised are:

* **Use for development requirements within the project** (e.g., FCC worksite tracks, landscaping purposes, etc.)

* **Use in earthwork (backfilling of quarries and mines and rewilding) and development projects.** This reuse case concerns most of the materials, as it can be applied for both the inert material and the polluted excavated materials, after appropriate decontamination. As each quarry is subject to specific environmental impact restrictions, specific acceptance criteria for the backfilling materials must be respected. In total, it is estimated that all material that will not be addressed to specific land filling due to pollution can, in principle, be reused for quarry landscaping, after treatment. However, in order not to saturate the region, other reuse cases are investigated at the same time.

* **Use of the limestone fraction** in concrete production and stabilisation of structures. The limestone, marl and clay deposits of the Jura and the northern Alps have provided the raw material for lime and cement since ancient times. Produced by calcining limestone, lime is used to improve soils and whitewash walls; mixed with sand and water, it produces a mortar that is very easy to produce and therefore very common. All limestone that will be extracted during the FCC construction project will be destined to these reuse cases. Due to the costs of production of these resulting construction materials, it is assumed that the reuse of limestone is at zero gain and zero cost for the project.

* **Use of the sand fraction in concrete production.** Direct reuse of sand and gravel could be envisaged, eventually after treatment of sieving and/or washing of the excavated materials. The use of cyclones for the washing of excavated materials is an established treatment method that allows separation of the clay and other materials and obtains good-quality materials. The study on the efficiency of this separation method remains to be performed.
* **Transformation of the molasse into fertile soil** for applications in the development of brownfield sites, urban recreational areas and forest areas, as well as improving the fertility of acidified land and/or as technical areas along the verges of roads and motorways (pollutant filtration). The use of excavated materials transformed into reconstructed soil requires the identification of areas for backfill in agricultural areas. The locations desired include hollows, slopes, areas of poor ground quality such as polluted or acidic soils, or of poor agronomic quality (e.g., low water retention potential). The application may be different depending on the type of land and topography. This type of measure could be particularly suitable for certain rural areas in the Auvergne-Rhône-Alpes region and in several cantons in Switzerland and would also allow deposits to be made near drilling sites. Due to the unknown topography of the chosen areas, it is currently difficult to identify the location and total areas. It is estimated that about 2 million cubic metres (about 4 million tons) of excavated materials could be reused via this pathway, provided the appropriate areas are identified.

* **Use of a part of the molasses as technical materials:** trench cover (e.g., roads), acoustic screens, farm tracks, forest paths etc. Both the French and Swiss neighbouring landscapes are constituted by woods of different nature or of rural areas. In particular, the zone in the proximity of Annecy has approximately 500 km of rural paths and tracks. In total, there are approximately 705,000 km of rural and forest paths in France. These paths and tracks must be maintained regularly; for this, inert materials are necessary to ensure their stability. Raw molasse is also suitable for the implementation of vegetation-free strips near roads. With the installation of noise-reducing and privacy-screening gabions, this scenario can generate significant savings in the development and maintenance of public roads. Support from the relevant authorities is required to identify suitable roads and locations near extraction sites, establish certifications, and grant permits necessary to carry out this type of application. A further application in the layout of roads is the use of reconstructed soil based on molasse as landscaping of trenches of covered streets or highways.

* **Development of building components** by compression (bricks or compressed earth using 'sandwich' technology) for use within the scope of the project where possible or outside the project (opportunities within the region to be investigated).

* **Development of new building materials** containing a part of the molasse (e.g., shotcrete ingredients, supporting materials, insulating panels for surface buildings), to be used within the scope of the project where technically feasible or outside the project (opportunities within the region to be investigated). Literature shows that considering excavated materials for the reuse as recycled concrete aggregates (RCA) in the structural concrete of the tunnel or of the basement of the tunnel could turn out to be not feasible because of the decreased strength and therefore further thorough studies are required. A prudent approach, until more complete studies are performed, could be to use RCA in shotcrete with fibre-reinforcement for non-structural parts only.

Some of these pathways are listed in excavated material management guides used in France e.g., from Cerema/UMTM (publication pending) and from the Ministère de la transition écologique et solidaire [9] and in Switzerland from the OCEV [10] and also in the AFTES recommendation GT35R1F2 [3] (currently in revision). The other pathways must be identified and a framework for cross-border use could be proposed to the respective authorities in the Host States.

The first four in the list correspond to traditional reuse cases already in use in other tunnel construction projects. These are taken into consideration and will be applied in priority whenever the geo-mechanical, mineralogical and chemical characteristics of the material are suitable for these applications.

In addition to these traditional reuse cases, innovative reuse pathways were identified during the 'Mining the Future®' international competition carried out in 2021 and 2022. The competition aimed to identify innovative pathways for excavated material from tunnel construction which could be profitable not only to the FCC but to any further projects in the subalpine region. The competition was launched under the Horizon2020 project 'Future Circular Collider-Innovation Study' (Grant Agreement n. 951753) and was jointly organised by CERN and Montanuniversität Leoben. The submissions were scrutinised by a jury panel of international experts. The four finalists' concepts ranged from the manufacturing of substrates for agriculture and forestry to the production of raw construction materials like concrete and shotcrete, compressed earth bricks and other hydraulically bound building materials. They all need to analyse and separate the materials during the tunnelling process in real-time, with subsequent on-site pre-processing directly on the excavation surface sites. Geogenic contamination by hydrocarbons and heavy metals must be removed or at least be reduced to levels that are compatible with the proposed processes and end-use conditions. The consortium led by BG Engineering was selected as the most innovative and comprehensive concept and won the competition.

Some of the solutions are now being integrated into a unique design and evaluated in the field, in a project planned to reach maturity by 2030. The objectives of the evaluations are twofold. Firstly, to establish how to conduct the online identification, sorting and pre-treatment of the materials during the excavation process. Secondly, to prepare different reuse pathways to sort and pre-treat materials, including transforming molasse into usable soil for forestry and rewilding applications, in line with the principles of a circular economy. The quality-assured creation of the reconstructed soil is a lengthy process spanning several years and has been chosen as the first large-scale experiment with field tests at OpenSkyLab.
The OpenSkyLab, is a project based on a plot of about 10,000 m² located near LHC Point 5 (CMS, Cessy, France) that has been made available by CERN. Molasse extracted during the HL-LHC excavations will be transported to this field to be used in the tests. Initial laboratory analyses will be performed off-site to identify the most suitable mix of molasse and other natural additives (compost). These will be followed by field tests in the OpenSkyLab’s controlled environment (monitoring of the field, weather, and plant growth conditions), using scientific protocols developed by a collaboration of universities working in this domain.

In keeping with CERN’s long-standing tradition, this project relies on an open collaboration with academia and industry. Currently, the collaboration includes university and research experts in agronomy, pedogenesis and geology (HEPIA, BOKU, BRGM, Montan University Leoben) and industrial partners in soil engineering and phytoremediation (Microhumus, Edaphos), soil treatment techniques (WSP-BG) and monitoring and supervisory control systems (BECC).

In order to facilitate acceptance into the reuse pathways of the excavated materials, it will be necessary to set up material-separating units during the tunnel construction phase, at the starting point of two TBMs as a minimum. These units could combine the screening, sorting, sieving and cleaning operations of the extracted materials.

Assuming a two-shift 24-hour working day over 240 days per year, the consortium that won the Mining the Future competition proposed a facility that could treat approximately 750,000 tonnes per year at an hourly rate of 200 tonnes. Each facility would employ a team of five people. A pilot project for the testing of the efficiency of these sorting and treating facilities could be envisaged during the next phase.

The working hypothesis assumes that the previously listed solutions will account for a global reuse of about 70% of the overall excavated materials, among which the reconstructed soil reuse pathway could amount to up to 2 million cubic metres (corresponding to about 25% of the total). The backfilling of quarries as well as more traditional reuse pathways (e.g., limestone and sand direct use) should overall account for about 45%. These quantities remain to be confirmed during the next phase.

*Regional opportunities* CERN commissioned a study to identify the regional opportunities available in France and Switzerland for the evacuation of the excavated materials. This included:

* A global inventory of the final storages and of the opportunities for landscaping of quarries and mines at the end of their operational lifetime, but holding a prefectural permit valid beyond 2033.

* A study on potential industrial railway sidings for the evacuation of the materials.

*Global inventory of regional opportunities* This study started with a preliminary inventory of potential regional opportunities for landscaping (quarries, mines) and storage, which was carried out at the start of the feasibility study (2021-2022) in France and Switzerland to provide initial indications of potential host sites and the capacities for excavated materials of the various pathways. The current status of the inventory is presented schematically in Fig. 1.54. These detailed inventories list the existing and planned facilities (horizon 2030) with sufficient capacity to receive and treat the excavated materials from the FCC. They will need to be repeated once the excavated material management plan has been defined to take account of the final material extraction fluxes and the possible availability of new reuse cases. Subject to updating and optimisation with respect to transport, these studies show that it is possible to find a pathway for all the materials excavated from the potential future FCC project and provide an initial estimate that can be used as a basis to begin the optimisation process according to the ‘avoid, reduce, compensate’ principle. It should be underlined that the inventory of the potential recipients of the excavated materials was carried out with the aim of evaluating the financial envelope and identifying potential showstoppers for the FCC feasibility. It is not possible at this stage to identify the specific recipients without engaging in contractual agreements. This step will be performed during the establishment of the final material management plan.

*Railway sidings* The study investigated the option of constructing industrial rail sidings near the surface sites to take away the excavated materials. Potential locations near existing railway lines (shown on Fig. 1.55) were identified, and the feasibility of creating sidings was examined. To supplement this study, the feasibility of a conveyor belt link has been assessed for the two sites deemed most appropriate for the installation of sidings: Vulbens (removal of materials from PJ) and Charvonnex (removal of materials from PG). This exploratory phase was completed by an initial assessment of greenhouse gas emissions from transporting excavated materials by road and/or by rail from the production site to the disposal site or to the location of the hypothetical reuse cases.

The feasibility study of railway sidings only took technical factors into account. The weighing of certain factors linked to the acceptability of creating a railway siding (e.g., environmental aspects such as the nuisance factor in a densely populated area) must be carried out before a decision is reached.

The creation or refurbishment of railway access, already considered to lower the nuisances due to truck transport, would further facilitate the use of quarries and reuse cases not in the immediate vicinity. A technical study could be conducted to analyse the possibility of cross-border transport by conveyor belts from Challex (PL) to the railway network at La Plaine in Switzerland and from Ferney (PA) to the rail network at the Geneva Airport in order to use the existing railway infrastructure for the transport of the materials to their final destination.
<figure><img src="image_57.png" /><figcaption>**Fig. 1.54** Schematic diagram of the inventory of the regional opportunities for material reuse (status 2021)</figcaption></figure>

<figure><img src="image_58.png" /><figcaption>**Fig. 1.55** Study of the potential locations for railway sidings</figcaption></figure>

### 1.6.7 Outline of the next studies

The scenarios for the reuse of excavated materials are based on preliminary assumptions regarding the proportion of materials with geogenic or anthropogenic characteristics that may require specific handling. At this early stage,