LOS ANGELES, Calif., Jan. 17, 2003 — When the winds kick up, power lines often get knocked down by swaying branches or fallen trees. In Los Angeles, however, such tree-related power outages have dramatically declined in the last five years, thanks to an aggressive tree-trimming program instituted by the Los Angeles Department of Water and Power (LADWP).
The Department’s vigilant tree trimming effort, which clears trees and branches that might come into contact with power lines, reaches every neighborhood in Los Angeles each year. Through this initiative, the LADWP reports that number of outages caused by trees declined by 65 percent in the past five years — from 345 in 1997-98 to 122 in 2001-02.
“The LADWP is consistently a leader in service reliability,” said Mahmud Chaudhry, LADWP assistant general manager — power. “One of the key ways we prevent damage and outages during storms is by being proactive throughout the year — by continually inspecting and carefully pruning trees to ensure they are clear from power lines and poles.”
In addition to the tree-trimming program, the Department prevents outages and equipment damage through its stepped-up power pole inspection and replacement programs. LADWP annually replaces 1,200 to 1,500 poles, as well as inspecting almost 25,000 poles annually, said Thomas Parker, manager of distribution, construction and maintenance.
LADWP consistently ranks in the top 10 percent of all utilities in providing reliable service to large customers, according to industry indicators such as the System Average Interruption Duration Index (SAIDI) and the System Average Interruption Frequency Index (SAIFI).
Between Jan. 5 and Jan. 7, the LADWP reported about 60,000 customers — about 5 percent of its customer base — were affected by outages caused by the Santa Ana winds. Overall, some 300,000 residents and businesses experienced power failures in areas served by LADWP and Southern California Edison. The LADWP electrical system withstood winds estimated at 70 to 75 mph. Only seven LADWP poles were damaged.
Regular tree trimming prevents outages by keeping the foliage away from power wires. Furthermore, the yearly cycle enables the Department to trim trees only as much as needed to clear the lines for that year. As a result, the work goes faster and maintains the aesthetics of neighborhoods.
The Department utilizes certified arborists, who follow pruning guidelines set by the International Society of Arboriculture and the National Arbor Day Foundation. A cadre of 25 tree surgeons and 10 assistant tree surgeons works out of Department service yards in Northridge and Lincoln Heights. According to Deal, they assess the species of tree and pace of its growth, along with the location and voltages of nearby power lines to determine how much to prune the trees each year.
The Department’s tree maintenance practices were recognized by the National Arbor Day Foundation and the National Association of State Foresters, which honored LADWP with the Tree Line USA Award in 2000.
Through its pole inspection and replacement programs, LADWP has dedicated crews to examine and test every pole that is at least 15 years old in a given neighborhood to determine if it is structurally sound. Depending on the pole’s condition, the crews apply a wood preservative, repair the pole with steel supports, or replace it entirely. Throughout its system, LADWP maintains about 300,000 power poles, 100,000 overhead transformers, and more than 6,000 miles of overhead distribution lines.
“These are detailed inspections by people who do the work day in and day out, testing and treating these poles. They check each pole to ensure the cross arms, transformers, and lines are all in good condition,” Parker said. Crews are also regularly inspecting about 4,200 miles of underground distribution lines. Within the past two years, the Department accelerated the program by adding contract crews and increasing the number of pole replacements to the current level.
The Department also uses infrared technology to test for “hot spots” — loose connections that could trigger failures — throughout the power system. Parker said LADWP is aiming to complete infrared inspections of the entire system every four years.
The Los Angeles Department of Water and Power was established more than 100 years ago to provide a reliable and safe water and electric supply to the city’s businesses and residents. For more information, call 1-800-DIAL-DWP, or log on to www.ladwp.com.