The team conducted a national search for a steel mill suitable for the film's climax, and selected a dormant Kaiser Steel mill in Fontana, California, after weeks of negotiations. Locating the Cyberdyne building was more difficult, as the site was to host numerous stunts, shootouts, and explosions. An industrial park in Fremont, California, was eventually rented for the duration of the film's production. Cameron and William Wisher completed the 140-page screenplay draft on May 10, 1990, and by July 15, the first shooting draft had been distributed to the cast and crew; particulars of the technically detailed scripts were shrouded in secrecy. Both the six-week turnaround for the script and the film's accelerated production schedule were to enable a 1991 Fourth of July release. Principal photography of "Terminator 2" spanned 171 days between October 9, 1990, and March 28, 1991, during which the crew filmed at the Mojave Desert before visiting 20 different sites throughout California and New Mexico. These locations ran the gamut from the crowded Santa Monica Place shopping mall, where the two Terminators converged on John, with brief shots coming from the Westfield MainPlace and Los Cerritos Center, to flood control channels in the San Fernando Valley, which played host to the chase between the Terminators and John; a river had to be redirected to allow filming on the otherwise wet channels. Cameron and his crew also filmed "Terminator 2" at The Corral Bar and the Lake View Medical Center (known as Pescadero State Hospital for the Criminally Insane in the film), both located in Lake View Terrace. The external shots of Cyberdyne Systems Corporation were filmed on location at an office building on the corner of Gateway Boulevard and Bayside Parkway in Fremont, California. Working with up to 1,000 crew members, the production team oversaw numerous stunts and chase sequences, the most notable of which took place on the Los Angeles–Long Beach Terminal Island Freeway, prior to "Terminator 2"s climax. Ten miles (16 km) of electric cables were laid to illuminate the night-time chase, which saw a full-scale helicopter crash, a sliding tanker, and other elaborate paraphernalia. Hamilton's twin sister, Leslie Hamilton Gearren, was used in some shots that required two Sarahs, including a scene where Sarah and John perform repairs on the Terminator's head (deleted from the theatrical release, but restored on the extended edition), and in some of the shots where the T-1000 impersonates Sarah.