The Environmental Protection Agency said it remains fully responsible for the toxic wastewater spill it caused one year ago in Colorado, while remaining silent on demands for someone at the agency to be held responsible.

The one-year anniversary of the spill is Aug. 5, when EPA contractors attempted to open the abandoned Gold King Mine in Silverton, Colo., that had been plugged a decade earlier.

The result was three million gallons of toxic sludge bursting out of the mine and sullying the waters of three states: Colorado, New Mexico and Utah.

Lawmakers, primarily Republicans, came down hard on EPA Administrator Gina McCarthy to take action by holding a senior official responsible.

The House Natural Resources Committee held a number of hearings and did its own internal probe, finding that the spill demonstrated EPA negligence.

"A year later, the Obama administration still won't tell us the whole truth," House Natural Resources Committee Chairman Rob Bishop, R-Utah, said in a statement to the Washington Examiner. "Accounts of events from Interior and EPA have been inconsistent and artfully misleading. The EPA insists they had no plan to dig out the plug [closing the mine], but they did and without testing."

"There has been zero accountability" for the incident on the part of the administration, Bishop said. "EPA's disaster dumped hundreds of tons of pollutants into a river that flows across four states — affecting farmers, treatment systems for safe drinking water and livelihoods, but no one has been punished."

He said the affected communities "deserve better. They deserve answers."

No federal employee has been fired for the mine spill. The head of Colorado's Natural Resources Department, Mike King, resigned in December after clashing with the EPA over the agency's record of events that said Colorado approved the plan at the Gold King Mine. King said in a letter that he neither approved nor rejected EPA's plan.

An EPA spokeswoman said the agency "cannot comment on personnel decisions" at this time. She said the agency is awaiting pending reviews from the General Accountability Office and EPA's Office of Inspector General "before making any final personnel decisions."

The EPA's inspector general started a probe in conjunction with the Justice Department on Monday to identify if federal officials engaged in criminal activity in the aftermath of the spill.

The agency issued a one-year retrospective report on Monday, detailing what it has done to clean up the spill and make sure it never happens again, while reiterating that it is to blame for causing the incident.

"EPA fully recognizes the impacts that the Gold King Mine release has had on communities and residents who live along and use the Animas and San Juan rivers," the one-year anniversary report said. "We continue to be accountable, and working with our federal, state and tribal partners, we are implementing and sharing best practices and lessons learned from this event."

It details the $29 million it began giving recently to states and tribes affected by the spill to monitor and prevent water run-off from the mines in the area from creating a potentially harmful situation.

The EPA pointed out that the region has dealt with mine run-off for years and the administration is working to find a long-term solution to fix the problem.

"Countless communities and their residents throughout the country are dealing with the legacy of abandoned and inactive mines," the report said. "The public should not have to bear the costs of cleaning up the contamination."

The administration has proposed a fix in its fiscal 2017 budget that would hold mining companies responsible for cleaning up hardrock mining operations through collection of a fee.

The EPA points out that it has done all it can to remedy the situation, but now it is up to Congress to act.

"We will continue to pursue parties responsible for creating these conditions and support the Obama administration's request for an abandoned mine lands fee to help cover the costs of cleanups at these sites," the report said.

"The president's proposal would levy a cleanup fee on the hardrock mining industry for public minerals similar to the royalties paid by the oil and gas industry and the abandoned mine reclamation fee paid by the coal industry," the EPA report said. "To date, Congress has not acted on the president's request."

Meanwhile, the EPA is back at the Gold King Mine to make sure a water treatment plant it set up near the site is operating correctly. It is also working on the mine opening that erupted last year. It will be at the site through November, before the Colorado snows make it impossible to continue construction work there.

The report said the Gold King Mine spill released the equivalent of four days of normal acidic runoff from mines in the area, with enough soluble metals in the toxic plume to build a number of big-rig trucks.

"EPA's analysis finds that the release of three million gallons of acid mine drainage was equivalent to four days of current acid mine drainage," the report said. "The total metal mass in the [Gold King Mine] plume was comparable to the mass of metals carried in one day of high spring runoff."

The EPA spill sent more than 1 million pounds of iron and other metals into the Animas River. That's the equivalent weight of nearly 330 Toyota Prius hybrid cars stacked on top of each other.

The agency said it is working with the Justice Department to respond to tort claims regarding damages and will be doing so shortly.

The EPA is expected to have an information booth set up at an event Friday in the town of Silverton, Colo., where the mine is located. The town is hosting a two-day event to mark the one-year anniversary of the spill to raise awareness.

The town is taking the spill in stride. A 5K run on Saturday will require participants to paint themselves the color of the toxic plume that flowed down the Animas River last year. Runners will be given the option of donning orange, red or yellow powder to color themselves during the race.