Blevins said the chemicals could have entered the aquifer along a 7-mile stretch of the Los Angeles River near Glendale that is not lined with concrete. He estimated that it would take less than a year for chemicals there to reach the aquifer.
Chromium 6 may also have seeped directly into the soil in areas surrounding industrial facilities, then into the ground water, because not all runoff water goes into storm drains, said Dixon Oriola, a senior engineer with the Los Angeles Regional Water Quality Control Board.
"Percolation over a 30-year time period in any unlined water conduit would impact the soil and possibly the ground water," Oriola said.
Decades of industrial pollution--much of it from aerospace manufacturing--turned the San Fernando Valley aquifer into a federal Superfund site. Chemical contamination in water wells remains an issue for area residents who say they were sickened by drinking poisoned water.
Since 1996, thousands of San Fernando Valley residents have sued the Lockheed Martin Corp. and other area companies alleging they were sickened over the years by chromium 6 and other toxins in the air, soil and drinking water.
Lockheed Martin has paid $60 million to date to settle claims, but has not admitted liability and says toxin concentrations were too small to make anyone sick.
Toxic Levels in Drains, Wells
Until the 1960s, industrial discharges were not regulated and water officials say they have no indication any laws were broken. Lockheed Martin spokeswoman Gail E. Rymer said the company has always complied with government regulations.
"Our record is very public on our use of chromium," Rymer said. "We've always said we've used chromium and hexavalent chromium in our operations, as did many other companies in the area."
The city records detail monthly chromium 6 levels in storm drains and a few water wells in Burbank, Glendale and Los Angeles between 1945 and 1982. The records were compiled by the DWP's Sanitary Engineering Division, now known as the Water Quality Division.
Pankaj Parekh, the DWP's manager of regulatory compliance, said the department conducted the studies at the request of a Los Angeles County task force studying pollution in the Los Angeles River.
Because the records only recently came to light, Parekh and other water officials could not say how the information was used.
The records were recently found by Blevins while preparing a report on chromium pollution for the Los Angeles City Council. After the existence of the records was hinted at in a public hearing, Blevins provided copies to The Times.
Blevins, 65, has studied upper Los Angeles River water issues for more than four decades, first at the DWP, then as water master. He was appointed in 1979 by the Los Angeles County Superior Court, which oversees the legal rights to pump water from the aquifer.
The records show that the highest level of chromium 6--80,000 ppb--was found in a storm drain near the former Glendale Grand Central Air Terminal on May 24, 1961. The highest sustained concentrations of the chemical were found in the Burbank Western Wash, a storm channel that discharges into the Los Angeles River, where levels reached 70,000 ppb in May 1955.
The DWP records show there were 37 days in the 22 years between 1945 and 1967 when chromium 6 was recorded at 1,000 ppb or higher.
In one instance, on March 23, 1955, workers tested for chromium 6 in the Burbank storm drain every 15 minutes for two hours, according to the handwritten DWP logs. The levels ranged from 5,000 to 17,500 ppb.
Chromium 6 concentrations dropped to under 1,000 ppb for all but a few months after February 1957, records show. There was another increase in chromium 6 levels in 1962, ranging from 1,500 to 4,000 ppb from March to August.
After 1967, the contamination levels dropped to less than 3 ppb for most months.
The documents do not identify the sources of the chromium 6 contamination, but the Los Angeles Regional Water Quality Control Board has targeted more than 200 manufacturers in the east San Fernando Valley as potential polluters.
The board is overseeing chromium 6 cleanup at former and current sites of Lockheed Martin, ITT Industries and Menasco, all in Burbank, and Courtaulds Aerospace and Drilube in Glendale, board documents show.
Scientists Divided Over Threat
Chromium is a metallic element found in nature. Relied on to harden steel, make paint pigments and other tasks, it is used in everything from aircraft manufacturing to electroplating. Chemical reactions can transform some amount of total chromium into chromium 6, a toxic form of the metal that can be dispersed as particles into the air, or into soil and water.
Although chromium 6 is considered a carcinogen when inhaled, scientists are divided over the threat posed by chromium 6 in tap water. The state does not require water agencies to test for chromium 6. Instead, agencies test for the presence of total chromium, which is limited to 50 ppb.