Sonic tests After concreting, each pile had to go through tests laid down by HD in order to verify both the integrity of the concrete and the length of the pile. All large diameter bored piles were required to pass a sonic test. Once Hui Hon reported that all the concreting had been completed, HD hired a contractor to conduct sonic tests, as stipulated in the contract. When questioned by an ICAC officer, the testing officer said that the piles of two buildings at the Yuen Chau Kok site had been tested between July and October 1998. He discovered that most of the sonic tubes in 18 of the piles were blocked. Some tubes were blocked at their very top, making it impossible to insert the test probe. The HD site staff considered that such blockages had been caused by faulty tube installation and they requested Hui Hon to come up with remedial measures. On 23 September 1998, however, Zen Pacific took charge of the project with Hui Hon's site agent still on the job. The site agent now suggested to HD that vibration tests should be carried out in addition to the planned core tests.