She said she reported most of the incidents to the company's managing director and manager Warren Pitches, but he did not take the complaints seriously.
Another former employee, Josh Kereama, gave evidence that PWP was a "horrible work environment".
"Pete was abusive to everyone. He was not a very nice person," he said of Powell.
"I once heard Pete call her 'black bitch'. I also heard [another employee] call her 'n*****'."
In addition, Kereama said that Powell had heard racist comments from other employees and when Kereama expressed concern about it, Powell told him that was just the way those employees were "so accept it".
ERA member Christine Hickey said that generally she placed little weight on the issue of witness demeanour because it was not a reliable indicator of credibility.
"However, some of Mr Powell's behaviour and comments at the investigation meeting revealed some aspects of his character which make it more likely that certain things he is alleged to have said are correct.
"Mr Powell likes to say things that are amusing to him and to see people react to them, even if it affects them negatively. He characterises what he says as banter and humour," Hickey said.
Powell had admitted being behind gossip and malicious rumours that had negative consequences for those involved.
He had also agreed that he used to call Whaiapu "Rabbit".
"When he was asked why, he said it was 'because she's got 11 children', and then added as an after-thought that it was because she worked quickly," Hickey said.
Powell denied that he called Whaiapu "black bitch". He did not comment on the accusation that he called her "baby killer".
"However, I find it proved that he called her both names," Hickey said.
Allegations also emerged during the ERA's investigation meeting that Powell had driven without a licence and while under the influence of alcohol. Powell denied that he drank in the mornings and said he only drank at night.
There were further instances of Powell telling lies to Whaiapu in which he claimed that her job was in jeopardy and that Pitches was angry with her. The ERA accepted that Powell had said these things.
For his part, Pitches called many of Whaiapu's concerns "petty", the ERA decision said.
He gave inconsistent evidence to the ERA, in particular, denying that there had ever been accusations of racist language to him when his diary entries showed he had spoken to a staff member after three such complaints.
In another instance, Pitches became upset when he found out staff had forgotten to bring equipment on a job.
He took off his hard hat and threw it on the ground. It bounced up and hit Whaiapu on the shin, the ERA decision said.
In his defence, Pitches said: "Peter, Paul and Marsha had arguments and disagreements from time to time. I always dealt with them when they were drawn to my attention but a lot of the time the issues were petty. I put it down to the fact that they were such good friends and bickered like brothers and sister."
He said of Whaiapu: "She gave as good as she got and I was never aware that she felt bullied or intimidated by Peter, or anyone else for that matter."
Hickey said that a reasonable employer would have taken Whaiapu's complaints seriously and investigated Powell's behaviour.
She said there was a history of racist abuse at PWP and it was not surprising that the two employees to give evidence were Maori.
"PWP failed to protect its employees from racist abuse," she said.
"Sometimes there is a fine line between acceptable banter and humour and unacceptable, abusive and unreasonable work behaviour. However, racist comments, such as 'black bitch', and name-calling such as 'baby killer', are far over that line and well into unacceptable and unreasonable work behaviour."
Hickey found that Whaiapu's resignation amounted to a constructive dismissal and ordered PWP to pay her $9360 in lost wages and $12,000 compensation.
Pitches hung up the phone when contacted for comment by the Herald.
