Planning for the westside extension resumed in January 1988. Prior to the start of preliminary engineering efforts, the Portland City Council asked TriMet to consider building a rail tunnel through the West Hills instead of following the Sunset Highway alternative's proposal to run tracks on the surface alongside Canyon Road. TriMet's engineers noted that this surface option would carry a steep six- to seven-percent grade as opposed to only two percent in a tunnel. That May, TriMet awarded a $230,000 contract to surveying firm Spencer B. Gross of Portland to map out the proposed area and another $200,000 contract to a partnership between Cornforth Consultants of Tigard and tunneling firm Law/Geoconsult International International of Atlanta to determine alternative tunnel routes. After several months of soil testing, TriMet announced that a tunnel would be feasible. In October, the agency released a report that identified three tunnel options: a "long tunnel" with a station serving the Oregon Zoo, the same long tunnel without a station, and a "short tunnel". Both long tunnels featured a western portal west of Sylvan while the short tunnel featured one on Canyon Road, and all three had an eastern portal near Jefferson Street in Portland's Goose Hollow neighborhood. These proposals were immediately met with opposition from West Hills residents who feared that tunneling activity would trigger landslides.