station duopoly between two full-power stations under FCC regulations, which disallow duopolies in metropolitan areas with fewer than nine full-power television stations and require that there be eight unique station owners that remain once a duopoly is formed (there are only seven full-power stations on the California side of the San Diego-Tijuana market). Though the E. W. Scripps Company owns KGTV and KZSD-LP, they are not considered a duopoly under the FCC's legal definition as common ownership between full-power and low-power television stations in the same market is permitted regardless to the number of stations licensed to the area. As a whole, the Mexico side of the San Diego-Tijuana market has two duopolies and one triopoly (Entravision Communications owns both XHAS-TV and XHDTV-TV, Azteca owns XHJK-TV and XHTIT-TV, and Grupo Televisa owns XHUAA-TV and XEWT-TV along with being the license holder for XETV-TV, which was formerly managed by California-based subsidiary Bay City Television). San Diego's television market is limited to only San Diego County. The Imperial Valley, including El Centro, is in the Yuma, Arizona television market while neighboring Orange and Riverside counties are part of the Los Angeles market. (Sometimes in the past, a missing network affiliate in the Imperial Valley would be available on cable TV from San Diego.) As a result, San Diego is the largest single-county media market in the United States. The radio stations in San Diego include nationwide broadcaster iHeartMedia; Entercom Communications, Local Media San Diego, and many other smaller stations and networks. Stations include: KOGO AM 600, KGB AM 760, KCEO AM 1000, KCBQ AM 1170, K-Praise, KLSD AM 1360, KFSD 1450 AM, KPBS-FM 89.5, Channel 933, Star 94.1, FM 94/9, FM News and Talk 95.7, Q96 96.1, KyXy 96.5, Free Radio San Diego (AKA Pirate Radio San Diego) 96.9FM FRSD, KWFN 97.3, KXSN 98.1, Big-FM 100.7, 101.5 KGB-FM, KLVJ 102.1, KSON 103.7, Rock 105.3, and another Pirate Radio station at 106.9FM, as well as a number of local Spanish-language radio stations. Infrastructure Utilities Water is supplied to residents by the Water Department of the City of San Diego. The city receives most of its water from the Metropolitan Water District of Southern California. Gas and electric utilities are provided by San Diego Gas & Electric, a division of Sempra Energy. Street lights In the mid-20th century the city had mercury vapor street lamps. In 1978, the city decided to replace them with