 Due to the lack of any land transportation route to the dam site , the first stage of construction would have involved the building of a temporary road from Eureka , about 30 miles ( 48 km ) away , to the dam site . Consideration also was given to the extension of the Alaska Railroad from Fairbanks to the site . A period of about four years would have been required for <unk> planning , including detailed construction surveying and finalizing the design of the dam , powerhouse , and other structures . Engineers estimated that after the four years of final planning and surveying , three years would be needed to dig river diversion tunnels and construct the cofferdams needed to clear the Yukon River streambed for construction . Housing and construction offices also would have been constructed for workers on the south bank of the site , and the cost for this effort was included in overall cost proposals for the project . 
