Although the allegations came from Halliburton's own water quality experts, the company once headed by Vice President Dick Cheney denied there was a contamination problem at Camp Junction City, in Ramadi.
"We exposed a base camp population (military and civilian) to a water source that was not treated," said a July 15, 2005, memo by William Granger, the official for Halliburton's KBR subsidiary who was in charge of water quality in Iraq and Kuwait.
"The level of contamination was roughly 2x the normal contamination of untreated water from the Euphrates River," Granger wrote in one of several documents.
The Associated Press obtained the documents from Senate Democrats who are holding a public inquiry into the allegations Monday.
Sen. Byron Dorgan, D-N.D., who will chair the session, held a number of similar inquiries last year on contracting abuses in Iraq. He said Democrats were acting on their own because they had not been able to persuade committee chairmen in the Republican-run Senate to investigate.
The company's former water treatment expert at Camp Junction City said he discovered the problem last March, a statement confirmed by his e-mail the day after he tested the water.
While bottled water was available for drinking, the contaminated water was used for virtually everything else, including handwashing, laundry, bathing and making coffee, said water expert Ben Carter of Cedar City, Utah.
Another former Halliburton employee who worked at the base, Ken May of Louisville, Ky., said there were numerous instances of diarrhea and stomach cramps, problems he also suffered.
A spokeswoman for Halliburton, Melissa Norcross, said its own inspection found neither contaminated water nor medical evidence to substantiate reports of illnesses at the base. The company now operates its own water treatment plant there, she said.
A military medical unit that visited Camp Ramadi in mid-April found nothing out of the ordinary in terms of water quality, said Marine Corps Maj. Tim Keefe, a military spokesman. Water-quality testing records from May 23 show the water within normal parameters, he said.
"The allegations appear not to have merit," Keefe said.
Halliburton has contracts to provide a number of services to U.S. forces in Iraq and was responsible for the water quality at the Ramadi base.
Granger's July 15 memo said the exposure had gone on for "possibly a year" and added, "I am not sure if any attempt to notify the exposed population was ever made."
The first memo on the problem, written by Carter to Halliburton officials on March 24, 2005, was an "incident report" from tests Carter performed the previous day.
"It is my opinion that the water source is without question contaminated with numerous micro-organisms, including Coliform bacteria," Carter wrote. "There is little doubt that raw sewage is routinely dumped upstream of intake much less than the required 2 mile distance.
"Therefore, it is my conclusion that chlorination of our water tanks while certainly beneficial is not sufficient protection from parasitic exposure."
Carter said he resigned in early April after Halliburton officials did not take any action to inform the camp population.
The water expert said he told company officials at the base that they would have to notify the military. "They told me it was none of my concern and to keep my mouth shut," he said.
On at least one occasion, Carter said, he spoke to the chief military surgeon at the base, asking him whether he was aware of stomach problems afflicting people. He said the surgeon told him he would look into it.
"They brushed it under the carpet," Carter said. "I told everyone, 'Don't take showers, use bottled water."
A July 14, 2005, memo showed that Halliburton's public relations department knew of the problem.
"I don't want to turn it into a big issue right now," staff member Jennifer Dellinger wrote in the memo, "but if we end up getting some media calls I want to make sure we have all the facts so we are ready to respond."
Halliburton's performance in Iraq has been criticized in a number of military audits, and congressional Democrats have contended that the Bush administration has favored the company with noncompetitive contracts.