2 Herbicides in Ground Water Traced to County Use at Whittier Narrows

Water quality tests first revealed in 1986 that two common herbicides had made their way into Southeast ground water supplies. The concentrations do not present a significant health hazard, but the discovery of the chemicals raised eyebrows nevertheless.

Local water officials eventually learned that the Los Angeles County Flood Control District had been using the herbicides near the county’s so-called spreading grounds along the San Gabriel River just south of Whittier Narrows. Water is pumped into the spreading grounds and allowed to seep down to replenish underground water supplies for the Southeast.

Rainwater apparently carried the herbicides atrazine and simazine down to ground water supplies, where they can remain for more than 20 years before breaking down chemically, water officials said.

Tests on lab animals indicate that the herbicides can damage the heart and other organs if ingested in large enough quantities. They also may cause cancer in humans.

But the herbicides, detected in wells as far south as Downey, are present in small amounts, not at levels considered by state health officials to be dangerous.

The county last used the herbicides near the spreading grounds in 1988, said Ken Erhard, a county engineer in charge of spray crews in the Whittier Narrows area.

“At the time we thought the soil itself would absorb the material” and it wouldn’t reach ground water supplies, Erhard said.

Erhard also noted that the herbicides have been widely used throughout the Los Angeles area over the years and the contamination has never been linked directly to the county spraying.

But local water officials point to the county as the most likely culprit.

“Having found it prevalent in almost all wells (near the Whittier Narrows) it would lead you to believe it came from the spreading grounds,” said Harold V. Morgan, an engineer who monitors underground water quality for the Central Basin Water Replenishment District. Southeast cities draw water from underground aquifers in the Central Basin.

“It was the best theory we were going on, and we simply asked them to stop,” Morgan said.

Atrazine and simazine are widely used herbicides favored by corn farmers and citrus growers. They also are used as general weed-killers.

Erhard said county trucks sprayed the herbicides on unpaved roads that pass by the spreading grounds and not on the spreading grounds themselves. Those roads have since been paved.

The herbicides were not used directly on the spreading grounds, Erhard said.

The atrazine and simazine contamination was found during the first round of new, extensive testing mandated by the state in the mid-1980s.

Only after the herbicides were detected did the state and, later, the federal government move to establish legal limits for the two chemicals in tap water.

In 1989, the state set the limit for atrazine at 3 parts per billion; simazine is 10 parts per billion.

During that first round of testing, about 25% of the wells sampled in the Southeast area were contaminated with the herbicides, Morgan said. The highest concentration of atrazine detected in 1985-86 was 3.4 parts per billion. The highest concentration of simazine was 2 parts per billion.

Last year, about 17% of the 270 wells tested in the Southeast area showed traces of the herbicides. The highest concentration of atrazine was 1.5 parts per billion, with simazine found at 1.4 parts per billion.

The U.S. Environmental Protection Agency has adopted the 3-parts-per-billion standard for atrazine, but the regulation is not scheduled to take effect until July, 1992. There is no federal standard for simazine, but federal officials have proposed a limit of 1 part per billion.

Because of the contamination, the county agricultural commissioner’s office has banned the use of the two herbicides in much of the Whittier Narrows area.

The use of atrazine has been banned in 24 square miles of the Whittier Narrows area since 1988, said Mel Makos, an environmental monitoring officer for the agricultural commissioner. Simazine is banned in 16 square miles of the area, he said.

For now, the levels of the chemicals detected in local water supplies are within state and federal limits, and there is no need for local water officials to take any action. But that could change if the EPA adopts the 1-part-per-billion standard for simazine.

“It’s possible that some treatment could be needed on several wells down the road if that ends up being the standard,” Morgan said.