Lorimer Gray told a fatal accident inquiry at Kirkcudbright Sheriff Court this week there were flaws in the management system and, sadly, it had failed to look after Laura McDairmant, 15, of Wetherall, Carlisle.
Mr Gray said the gorge-jumping activity appeared to have been handed down over the years and there was an inherent issue that there were rocks below and someone could slip.
And he said: "I think they were oblivious to the dangers because of the practice of using it over a number of years."
Laura was on an adventure holiday at the Barcaple Outdoor Centre at Ringford, Castle Douglas, owned by the Abernethy Trust, in July 2006 when she plunged 31ft onto rocks at the Black Loch, near Newton Stewart.
She died 24 hours later in Dumfries Infirmary, despite the efforts of doctors and surgeons, after being airlifted to hospital suffering serious face and neck injuries in the fall.
"We have to make sure it never happens again and we have put in place a number of things to prevent that," Mr Gray said.
He also said it appeared that a former chief instructor had introduced the gorge-jumping activity at Barcaple in 2001-02 and the pattern of operation had been passed on to his successors and the same activity had been carried on until 2006.
According to Mr Gray, gorge- jumping was carried out at the three other sites in Scotland but the one at Barcaple where the teenager died was the highest of the lot and the nearest to the 31ft was three-and-a-half metres.
Mr Gray also said he was surprised that the operations director at Barcaple did not know the jump from the large pool was being used.
He was unaware that concerns had been raised by some instructors about the jump and added that systems were now in place where concerns raised would be discussed and looked at.
The risk assessment then in place for gorge walking, he said, was too vague and was a flawed document.
Mr Gray said he had gone to the pool to inspect it after the accident to Laura and the more he explored it the more he realised the dangers of the pool.
Asked if his organisation would ever take children gorge-jumping where there was an object that had to be cleared with the risk of death or serious injury, Mr Gray said: "Definitely no."
The inquiry before Sheriff Johanne Johnston is continuing.