A team of experts investigating the Quail Creek dike failure has asked for an exploratory trench to be dug in the bedrock at the spot where the structure collapsed.

The investigators said Saturday they are looking for vertical cracks in the bedrock which could have provided a route for reservoir water to escape beneath the dike. If the flow through the cracks became large enough, the rushing water could have undermined the earthen dike.This appears to be the leading theory for the New Year's Eve dike failure which caused $11 million damage.

Robert James, chairman of the investigating group, said investigators were keeping an "open mind" to other possibilities.

The five-member team completed its on-site visits Saturday with a series of interviews with witnesses to the dike failure and preparation of a list of documents, maps and research they need to determine the cause of the collapse.

In addition to the trench, they asked for an analysis of the material used to build the dike to determine whether construction problems may have contributed to the problem. They also want a detailed geologic map of the site, and copies of all records dealing with leaks from the dike and the steps which were taken to plug them.

Each investigator will spend the next several weeks reviewing the information before holding another meeting in St. George. At that meeting they are expected to exchange ideas, determine whether additional research is needed and begin preparing their reports on the cause of the collapse and the possibility of rebuilding the dike.

They also authorized the Washington County Water Conservancy District to trim the 50-foot-high vertical walls on either side of the dike rupture. District officials are concerned that a sightseer could be injured by chunks of rock and dirt which continue to fall from the broken dike.