LOS ALAMOS — Readings from a monitoring well in Mortandad Canyon near Los Alamos National Laboratory show levels of chromium that are 16 times higher than state drinking water standards.

The laboratory said the readings are the first from a new monitoring well in the canyon.

Officials are looking to the well to help define the size, boundaries and direction of the contaminated plume. The contamination is thought to have originated in the main administrative area of the lab before 1972.

"We could be looking at a plume that's stationary," said Danny Katzman of the lab's environmental stewardship project.

Katzman said models and calculations pointed to the location as a likely spot for either finding the backside or the heart of the plume.

Another well in Sandia Canyon to the north will add an additional piece to the puzzle, since it is designed to investigate an area in the regional aquifer below where an intermediate well has found elevated readings.

Some indication of the tail of the plume may be discerned after the first samples are collected from that system in February.

Two more wells also are coming on line farther down gradient to help trace the front edge of the plume.

According to the lab, most of the chromium contamination in an aquifer beneath Los Alamos National Laboratory can be traced to a power plant that operated during the height of the Cold War.

Effluent from the plant went into Sandia Canyon and is thought to have migrated into the neighboring Mortandad Canyon.

Since the chromium was detected in early 2005 and brought to the attention of regulators and the public more than a year later, it has brought attention to the groundwater monitoring project at the lab.

Last year, the state Environment Department reached a settlement with Los Alamos National Laboratory over the nuclear weapons lab's failure to report chromium contamination in one of its monitoring wells in Mortandad Canyon.

In addition to a $251,870 fine, the settlement required the lab to regularly review data from all groundwater monitoring and to report findings quickly if previously undetected contaminant concentrations exceed state or federal water quality standards.