Sediment

At the bottom of a lake near Japan's Wakasa Bay, more than 50,000 years of history has been pulled out of the ground in the form of sediment and leaves. The information contained in those samples will allow scientists to determine the age of organic materials and fossils with new clarity by improving carbon dating, according to a study published Thursday in the journal Science. Carbon dating works by detecting the relative amounts of two varieties of carbon: carbon-14, or C-14, and carbon-12, or C-12.

At the bottom of a lake near Japan's Wakasa Bay, more than 50,000 years of history has been pulled out of the ground in the form of sediment and leaves. The information contained in those samples will allow scientists to determine the age of organic materials and fossils with new clarity by improving carbon dating, according to a study published Thursday in the journal Science. Carbon dating works by detecting the relative amounts of two varieties of carbon: carbon-14, or C-14, and carbon-12, or C-12.

Silt, sand and clay scraped from the ports of Los Angeles and Long Beach could be dumped in an underwater canyon off Newport Beach, under a federal proposal released Monday. The proposal by the U.S. Environmental Protection Agency would allow 2.5 million cubic yards of sediment a year to be dumped off Newport Beach. A similar proposal would allow for 1 million cubic yards of sediment to be deposited at a site off Los Angeles. And although the site off Newport Beach is proposed for 4.

Work crews have finished scooping tons of chemical-laden sediment from the historic Rhine Channel in Newport Harbor, completing a $4-million project ahead of time. The channel, once a bustling home to fishing fleets and cannery operations, has long been contaminated by mercury, pesticides and other toxic chemicals. The city's contractor, Dutra Dredging, beat the year-end deadline to dredge the channel and haul the contaminated sediment to Long Beach, where it will be used as fill dirt for a construction project.

Los Angeles County and the Army Corps of Engineers announced Thursday that together they will fund a dredging project in Marina del Rey to clear a silt-choked waterway that leads from the marina to the ocean. At a cost of $1.25 million, about 360,000 tons of sediment that has built up in the marina's entrance channel is to be scooped out, much of it silt carried down the coast or from Ballona Creek to the channel during storms. The dredged material will end up on nearby Dockweiler Beach.

To his doubters, Bill Blomgren came across as a hopeless neophyte and dreamer, a small-time excavation man who said he could move a mountain and pay the government for the privilege of doing it. No ordinary mountain, this one covered 1,500 acres in the northeast San Fernando Valley and was as flat as the Mojave Desert.

Off Southern California's shore, purity is an illusion that lies only a few feet deep. The trouble's not with the water; it's with what lies beneath it. From Santa Catalina Island to New York Harbor, the mud and silt that line the bottom of rivers, bays and lakes contain chemicals deemed potent enough to kill aquatic animals and endanger the health of people who consume marine life.

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.

Earl Billiot guides his boat down a quiet bayou and explains how it used to be, when the water that runs as wide as a two-lane highway was so narrow you could reach out and touch the land. Branches heavy with Spanish moss draped over the bayou, and forests covered marshes that are bare now except for the skeletons of dead cypress trees. Eighty miles away, tourists and locals gather atop a levee in New Orleans to gape at the magnificent Mississippi River, swollen by floods and higher than most have ever seen it. They relax in the afternoon sun with plastic cups of daiquiris and beer, certain that the structure they sit on will keep the water back.

Weather permitting, work will end Friday on a dredging project in Marina del Rey to remove sediment that is blocking part of the entrance channel to the marina. Next week, when the dredging is completed, workers will remove a discharge pipeline installed along Dockweiler State Beach as part of the project, said Deputy Fred Pausch of the Los Angeles County Sheriff's Department. The 235,000 cubic yards of sediment dredged out of the entrance channel is being deposited on the beach.

The removal of 25,000 cubic yards of sediment from the basin behind Devil's Gate Dam in Pasadena has been put on hold until August in order to prevent the destruction of a habitat for toads. Work was set to begin last week, but Pasadena officials decided to postpone the job pending further environmental review after Hahamongna Watershed Park users complained that Johnson Field, where the dirt was to be temporarily stored, was home to a large number of toads that would be smothered underneath the piles of dirt.

Earl Billiot guides his boat down a quiet bayou and explains how it used to be, when the water that runs as wide as a two-lane highway was so narrow you could reach out and touch the land. Branches heavy with Spanish moss draped over the bayou, and forests covered marshes that are bare now except for the skeletons of dead cypress trees. Eighty miles away, tourists and locals gather atop a levee in New Orleans to gape at the magnificent Mississippi River, swollen by floods and higher than most have ever seen it. They relax in the afternoon sun with plastic cups of daiquiris and beer, certain that the structure they sit on will keep the water back.

Water won't wait Re "Messing with Devil's Gate," Editorial, May 6 I lived in La Crescenta during the great flood of 1938. I remember listening to radio reports that Devil's Gate Dam was in imminent danger of collapsing. Fortunately it didn't, and the Arroyo Seco and the communities below were saved from a deluge of mud and water. The fact that the dam's basin has been allowed to fill with sediment over the years is a sign of ignorance and mismanagement. The L.A. County Board of Supervisors should make clearing out the basin a top priority.

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.

On a southern-facing slope of the San Gabriel Mountains, Glen Owens strode through the dappled sunlight of century-old oaks and sycamores that the Los Angeles County Department of Public Works wants to replace with muck dredged from a nearby reservoir. Eyeing the trees marked for removal with strips of black and white ribbons nailed to their trunks, Owens shook his head in dismay. "I've got the same feeling I get when I see cattle on their way to slaughter," he said. "Don't get me wrong ?

On the surface, Malibu Lagoon would seem a shining example of a restored wetland, a rarity along Southern California's built-up coastline. In an estuary that was once filled with dirt to create baseball diamonds, snowy egrets and black-crowned night herons now hunt for fish along the grass-covered banks of tidal channels, while sparrows and red-winged blackbirds perch on tule reeds swaying gently in the sea breeze. But beneath all that are stagnant, polluted waterways with steep banks so poorly constructed when the lagoon was restored that state parks officials say they must be drained, dredged and rebuilt to meet even basic water quality standards.

Sudden tremendous gushes of water from underground most likely carved out unusual fan-shaped geological formations like staircases long ago on the surface of Mars, scientists said. The Martian surface has about 200 large basins with fanlike formations, about 10 of which are terraced with what look like steps into the basin. Since they were first seen three years ago, scientists have debated how these formations, some of them nine miles wide, were created. Dutch and U.S. researchers dug a crater in sand in a room-size tub, then started water flowing in through a channel.

In the first large-scale analysis of polluted sediment, the U.S. Environmental Protection Agency has named 96 areas on the bottom of the nation's oceans and rivers as severe threats to marine life or people.

St. Petersburg, Fla. — Scientists have found evidence that oil has become toxic to marine organisms in a section of the Gulf of Mexico that supports the spawning grounds of commercially important fish species. Researchers from the University of South Florida said Tuesday that, in preliminary results, there appear to be droplets of oil among the sediments of a vital underwater canyon where clouds of oil from the BP spill were found. "So, indeed, the waters have a level of toxicity that needs to be recognized, and I think these were some of the first indicators that the base of the food web — the bacteria and the phytoplankton — may be affected," said David Hollander, chief scientist on a research vessel that just returned from a 10-day trip in the gulf.

A tsunami triggered by a massive earthquake in Chile surged across Hawaii on Saturday, churning up sediment with minor waves and tidal surges, but causing no apparent damage. The National Tsunami Warning Center canceled a tsunami alert that prompted the evacuation of nearly 100,000 residents and tourists and emptied the state's beaches on a warm, sunny weekend morning. "I think we've dodged a bullet," Gerard Fryer of the National Tsunami Warning Center told reporters in Honolulu.