Environmental Protection Agency Administrator Gina McCarthy speaks at a news conference on the recent Colorado mine spill after speaking at a Resources for the Future policy leadership forum, Tuesday, Aug. 11, 2015, in Washington.

(AP Photo/Andrew Harnik)

The head of the U.S. Environmental Protection Agency says it "pains me to no end" to see the 3 million gallons of mine waste that has turned the Animas River in southwest Colorado into an orange-colored pollution stream.

Gina McCarthy made the comments Tuesday in Washington, D.C., as her agency came under siege after federal and contract workers accidentally unleashed the spill as they inspected an abandoned mine near Silverton.

She took full responsibility for the spill and said the EPA is working around the clock to assess the environmental impact. Here's a partial transcript of her statement:

As you may not know, there are thousands of abandoned mines throughout the West, and EPA routinely works with states to clean up these sites. The spill occurred when one of our contracting teams was using heavy equipment to enter the Gold King Mine, an inactive mine north of Durango, to begin the process of pumping and treating the contaminated water inside. In response to this unfortunate accident, we have deployed the full depth and breadth of the agency, with other partner agencies assisting.  

It takes times to review and analyze data, but we have our researchers and scientists working around the clock. Our commitment is to get this right and protect public health. Thankfully, there have been no reported cases of anyone’s health being harmed. Additionally, from initial sampling results, as the plume has advanced seeing elevated levels, and as it moves on, we are seeing a downward trajectory toward pre-event conditions.

McCarthy said she would visit the region on Wednesday. 

The mine waste contains arsenic, lead, various heavy metals and other pollutants and has flowed at least 100 miles downstream to New Mexico. Via NPR:

Water samples taken after the spill showed lead concentrations in some places that were 3,500 times the normal levels in and around Durango. 

Critics clear throats

The accident comes at a sensitive time for the EPA, a frequent and favorite target of conservatives and pro-business groups. McCarthy spoke Tuesday as part of an event on the Obama Administration's Clean Power Plan, which mandates steep greenhouse gas emission cuts from U.S. power plants.

The Animas River near Durango on Aug. 9, 2015. Orange sediment is still visible along the river’s banks.

(Grace Hood/CPR News)

State and local officials in the areas affected by the spill have characterized EPA's initial response as too slow and too small. It took about 24 hours to first notify some downstream communities of the accident and the agency originally underestimated the volume of the spill.

Sen. Jim Inhofe, chairman of the Senate Environment and Public Works Committee, said Tuesday he is closely monitoring EPA's spill response.

"This has and will continue to lead to significant economic damage to local businesses, farmers, tribes and residents," said Inhofe, R-Okla. "I will work within the committee and with my colleagues in Congress to ensure the EPA is held accountable to this grave incident and that those impacted are provided the necessary support to move forward."

Colorado governor tours scene

Gov. John Hickenlooper began his visit to the affected areas Tuesday with a tour of a fish hatchery in Durango. Cages have been placed in the Animas River there to catch fish and measure any effects on them from the spill. So far, officials say they see no problems.

Gov. John Hickenlooper stands next to the Animas River near Durango, Colorado on Tuesday, Aug. 11, 2015. The governor declared a state of disaster emergency on Monday, days after 3 million gallons of toxic mine wastewater were accidently dumped into the river. 

(Grace Hood/CPR News)

Hickenlooper issued a disaster declaration for the area Monday, releasing $500,000 to assist businesses and towns affected. Other stretches of the Animas River, and the San Juan River into which it flows have also been declared disaster areas in New Mexico.

He said Tuesday he thinks a mine spill accidentally triggered by the EPA crew will move the state and federal government to more aggressively tackle the "legacy of pollution" left by mining in the West.

Much of the wastewater has now been plugged up, he added, but the state and the Environmental Protection Agency need to speed up work to identify the most dangerous areas and clean them up.

Members of the news media follow Gov. John Hickenlooper, out of view here, down to the banks of the Animas River on Tuesday, Aug. 11, 2015.

(Grace Hood/CPR News)

The former geologist says that if there's a "silver lining" to the disaster, it will be a new relationship between the state and the EPA to solve the problem.

Davis Filfred, a Navajo Nation Council delegate, says residents on the reservation near the Four Corners area who depend on drinking water from a river contaminated by mine waste have 90 days' worth of water in reserve.

Filfred said Tuesday in Utah that he doesn't know how long the reservation could truck in water and that farmers depend on the San Juan River to irrigate about 30,000 acres of crops.

Filfred said the tribe is frustrated by a lack of information from the federal government about whether the pollutants are harmful to humans and livestock.

Approaching Lake Powell

There are no plans so far to slow water flows on the Colorado River below Lake Powell because of the mine spill, which initially polluted Cement Creek near Silverton, then the Animas River, and then San Juan. The waste is expected to reach Lake Powell and then the Colorado River by midweek. The lower stretch of the river serves parts of California, Arizona, Nevada, New Mexico and Utah.

Chris Watt, a spokesman for the Bureau of Reclamation in Salt Lake City, says it's too early to say what the effects of the contamination might be. The agency is testing water at the request of the Environmental Protection Agency. Calculations indicate the pollution has reached Utah, but tests haven't confirmed it because the water's chemistry has returned to normal.