section of I-515 around Henderson before currently ending at the Henderson Spaghetti Bowl interchange with I-215 and SR 564. I-11 will be extended through the Las Vegas Valley along the existing alignments of I-515/US 93/US 95 to downtown Las Vegas, then running concurrently with US 95 northwest to SR 157. History As recently as 1997, US 93 was mostly a two-lane road between Wickenburg and Hoover Dam, and was known for its dangerous curves and hills in the stretch between Wickenburg and I-40. In the late 1990s, ADOT began widening US 93 to four lanes, and in some areas building a completely new roadway. In other places along the route, ADOT simply repaved the old highway and built two new lanes parallel to it. ADOT also began studying the possibility of adding grade separations to US 93 near the Santa Maria River to make the road a full freeway. At the same time Nevada and Arizona began looking at US 93's crossing of Hoover Dam, a major bottleneck for regional commerce, with hairpin turns, multiple crosswalks for pedestrians, and steep grades. Plans for a bridge to bypass the dam became even more urgent when the road was closed to trucks after 9/11 in 2001, forcing commercial traffic to detour through Bullhead City, Arizona, and Laughlin, Nevada, causing major transport delays as a result. With the completion of the Mike O'Callaghan–Pat Tillman Memorial Bridge on October 14, 2010, the vast majority of the roadway is now a four-lane divided highway. Still, with Phoenix and Las Vegas as the two largest neighboring cities in the United States not connected by Interstate Highway, leaders in both cities lobbied to include I-11 in the next Transportation Equity Act reauthorization. With the rise of the concept of "megapolitan" urban regions, I-11 is considered a key connector to unify the triangle formed by Las Vegas, Phoenix, and the Los Angeles area (the triangle consisting of I-15 to the north/west, I-10 to the south and I-11 on the east). The Federal Highway Administration (FHWA) approved NDOT's environmental review of a bypass around Boulder City, which would connect the end of the recently constructed Hoover Dam Bypass bridge east of Boulder City to I-515 west of the town. In December 2013, University of Nevada, Las Vegas (UNLV), researchers discovered naturally occurring asbestos in the route of the Boulder City bypass. Containing the asbestos and monitoring the surrounding air