A senior medical advisor for the Department of Defence says taking blood samples from people living in the Williamtown contamination zone will only cause anxiety.

A Senate committee looking into the response to the leaching of chemicals into ground and surface water near the Air Force base held a public hearing in Newcastle yesterday.

Some locals have been calling for blood testing of residents due to concerns about health impacts.

Defence's occupational and environmental senior medical advisor Dr Mathew Klein told the inquiry, in his opinion, blood testing is not a good idea.

"Unfortunately, it does not give us an indication of a particular level of risk," he said.

"It does not give us an indicator of a particular medical management.

"It also creates a huge degree of anxiety and, as we've heard, the level of anxiety is already very high."

Defence spokesman Steve Grzeskowiak told the inquiry he could not dispute claims contaminants were running off the base during rain this week.

He said Defence cannot stop water run off leaving the base.

"We have engineers and consultants working for us, and none of them are telling that there is a way that that can be done," he said.

"I heard today there might be ways and we'll definitely investigate those, but even those methods, as I've had them described to me, are unlikely to stop contaminated water leaving the base under all circumstances."

Federal Newcastle MP Sharon Claydon said the public has been kept in the dark about the contamination for too long.

"It distresses me if any agencies have had prior knowledge, and have not sought to disclose this," she said.

"So, it's information that should be in the public realm, no more secrecy.

"The more we open the windows, let the sun shine in, the better for everyone."

Williamtown residents say they are relieved to have finally had the opportunity to put their cases to the Senate committee.

One of the main issues discussed yesterday was compensation, with residents demanding a thorough package to help them get back on their feet in the wake of the contamination.

Williamtown and Surrounds Residents' Action Group president Cain Gorfine said he does not believe Defence will deliver compensation any time soon.

"They've clearly got their head stuck in the sand, and they have not admitted fault at this stage, and there were no substantial talks of compensation," he said.

"So, in relation to Defence, at this stage no, we think their hand is going to have to be forced."

The committee will finalise an interim report by early February 2016.