SDSU Transit Center is a station on San Diego Trolley's Green Line. The station is underground (the only such station in the system) and has side platforms. The station is located in the Aztec Green on the south portion of the campus of San Diego State University. The station entrances are between College Avenue and Campanile Drive. The station is very popular with students and staff who commute to the university because of the high cost and low availability of parking around campus.HistoryIn 1989, the San Diego Metropolitan Transit Development Board began developing plans for an additional trolley line connecting its Blue and Orange lines. The new line was initially expected to cost $506 million and cover 5.6 miles of track. After initially looking at over ten different routes to connect the two lines, the Board initially recommended connecting San Diego State University at the north end of its campus, near Interstate 8. However SDSU officials wanted the trolley station to go through the center of the campus, which would require tunneling underneath the campus. The Board initially balked at this concept as it would increase construction costs by $40–50 million. Once the Board learned that tunneling would be cheaper than purchasing adjacent land they agreed to alter the route. Final construction costs for the new trolley station were $103 million. Construction for the new trolley line first began in 1999.ConstructionSeveral methods were used to excavate the tunnel that would contain the station and the tracks to be used for the trolleys to pass underneath the campus. 2,915 feet (of the total 4,000 feet of track) were excavated using the cut-and-cover method where a current road above the tunnel would have its pavement removed, the underlying ground entrenched, and the pavement for the road re-added. For the remaining 1,085 feet, the New Austrian Tunnelling method was used, which required the use of the geological stress of the surrounding rock mass to stabilize the tunnel.
