Residents were worried the chemicals used to control weeds and shrubs along train tracks would leak into a springs in nearby yards and kill fish in streams.

To control weeds, the state-owned railroad asked regulators last year for permission to spray three herbicides, which included the active chemicals glyphosate, 2,4-D and sulfometuron methyl. But the herbicides are labeled with the prohibition: “Do not apply directly to water,” state regulators said Thursday.

That was one of several reasons the proposal was rejected, said Kim Stricklan, pesticide program manager for the Alaska Department of Environmental Conservation.

Another reason was the hundreds of streams and rivers that lie next to the rail line, not including thousands of other water resources, such as drinking water wells, wetlands and springs. The 10-foot buffer proposed by the railroad wouldn’t keep chemicals from leaking into the water, regulators said.

In addition, the railroad failed to identify all of the potentially affected water bodies in the area, regulators said.