Dam

Several weeks of debate over the fate of a grove of oaks and sycamores in the Arcadia highlands have left a community at odds, even after nearly 200 trees were bulldozed by Los Angeles County work crews. At least 179 coastal oaks and about 70 sycamores were uprooted and ground into wood chips on an 11-acre site just below Santa Anita Dam to make way for 500,000 cubic yards of sediment to be dredged from behind the structure. Three of four tree-sitters arrested after a 12-hour standoff Wednesday with Los Angeles County sheriff's deputies were released on their own recognizance Thursday after being charged with misdemeanor counts of trespassing and obstructing a police officer.

Residents of Brisbane, Australia's third-largest city, braced Wednesday for potentially monumental flooding as a river overflowed its banks from a combination of rain, runoff and the forced release of large amounts of water from a dam that had been designed to protect the city from raging storms. At least 40,000 properties were expected to be affected by the overflowing Brisbane River, as water let out of the Wivenhoe Dam to the north bore down on the city at a rate of 7,000 cubic meters a second.

San Gabriel Dam operator Herbert Romero led 16 engineers clad in hard hats and yellow vests down a long flight of metal stairs on Wednesday to a cast-iron wheel on a ledge overlooking a stream bed a few miles above Azusa. At 9 a.m., Romero turned the wheel, opening one of the earth-and-rock dam's two 123-inch-diameter valves. The ground rumbled and water blasted forth with a roar in a horizontal stream more than 200 feet long, as if from a mammoth rocket engine. The biannual release of water at a rate of up to 3,800 cubic feet a second was needed to ensure that the dam, as high as a 25-story building, would be able to control floods out of the San Gabriel Canyon's 200-square-mile watershed.

A new bridge soaring across the Colorado River uniting Arizona and Nevada was formally dedicated Thursday, eliminating a 75-mile detour around Hoover Dam. Named for heroes from different wars, the bridge will be the key part of a faster route between Phoenix and Las Vegas. It is the Western Hemisphere's longest single-span concrete arch bridge and one of the highest in the world, officials said. The 1,900-foot bridge, which is 890 feet above the river, is part of a $240-million four-lane bypass that will shift traffic away from the two-lane U.S. 93 across Hoover Dam. It is about 1,500 feet south of the dam and crosses over Black Canyon.

Named for heroes from different wars, the bridge designed to speed traffic by bypassing the area around the Hoover Dam was formally dedicated Thursday morning. Top officials including Transportation Secretary Ray LaHood dedicated the bridge, which soars across the Colorado River uniting Arizona and Nevada and will be the key part of a new, faster route between Phoenix and Las Vegas. It is the Western Hemisphere's longest single-span concrete arch bridge and one of the tallest in the world, officials said.

Two Wynn experiences I was fascinated by the letter regarding the McGrahams' Wynn hotel "Inn-Excusable" situation [On the Spot by Catharine Hamm, Sept. 19]. I also received a promotional letter from the Wynn/Encore and, in fact, just returned from Las Vegas. My package was for a three-night/four-day stay for two at the Wynn, including two tickets to "Le Rêve. " My e-mail confirmation was apparently sent from the Wynn (printed in very tiny letters); however, Encore was printed in large, bold lettering in the confirmation, so I thought the reservation was for the Encore.

THE BEST WAY TO HOOVER DAM AND BOULDER CITY, NEV. From Los Angeles, take Interstate 10 east to Interstate 15 north toward Las Vegas. Take Interstate 215 east to U.S. 93 south to Boulder City and the dam. Hoover Dam tours, (866) 730-9097, http://www.usbr.gov/lc/hooverdam/service/index.html . The Bureau of Reclamation has conducted tours through the day since 1937. Visitor Center admission is $8; tours of the power plant and the dam and its passageways vary in price but include Visitor Center admission.

Clayton Sellers'voice echoes off the sheer rock walls that rise from his vantage point along the Colorado River in Black Canyon, just downstream from the base of Hoover Dam. "[The dam] was started in 1931 and completed in 1935, about two years ahead of schedule and under budget," he says as he maneuvers a pontoon raft across the water. Sellers' passengers, mostly tourists staying in nearby Las Vegas, are awed by that fact, and even more so by the massive engineering marvel standing before them.

On the sloping western shores of Lake Tana in central Ethiopia, where villagers gape at new tractors as if they were Ferraris and power lines pass over lean-tos lighted by candles, a poor nation's hopes hum inside a new hydroelectric plant. Lured by the plant's promise of powering villages and irrigating 350,000 acres of farmland, intrepid investors are venturing across misty hills and navigating sprawling savannas. The World Bank has lent the country $45 million to "unleash" the region's growth potential, and Ethiopian leaders have promised that development along the tributaries feeding the Blue Nile will raise crops for the hungry and bring jobs to a rustic swath of Africa.