Alternate site selection and development for the Thirty Meter Telescope at Observatorio del Roque de los Muchachos, La Palma, Spain

M3 is a full-discipline architecture, engineering and construction management firm hired by TMT International Observatory to design and manage the construction of several aspects of the Thirty Meter Telescope (TMT). The TMT is a next-generation extremely large telescope that is approaching its start of construction. While the TMT continues to consider construction at the originally proposed site on Maunakea, Hawaii, the project is ensuring viability while addressing challenges at its baseline site through establishing an alternate design for facilities at Observatorio del Roque de los Muchachos (ORM) on the island of La Palma, Spain. With both locations actively being developed in parallel and with a similar scheduled start of construction in mind, this paper offers an overview and insight into how and why TMT and M3 established a practical design for the Canary Islands, how it differs from the design at Maunakea, and discusses the legal processes followed to establish access to a suitable site in La Palma.