Topeka ? A review team concluded Monday that the deaths of six people in a Labor Day weekend flash flood south of Emporia were caused by a “truly extraordinary weather event” and not by any design deficiencies of the Kansas Turnpike.

In a report presented to Gov. Kathleen Sebelius, officials with the Kansas Highway Patrol, Kansas Turnpike Authority and Kansas Department of Transportation concluded the Aug. 30 flash flood along Jacob Creek would have occurred even if the design of the highway’s culvert was flawless.

The flood occurred as heavy rains fell along the turnpike, sending as much as 4 feet of water over the four-lane road. The raging water claimed the lives of a mother and four children from Glenaire, Mo., and a Fort Worth, Texas, man who was trying to save them.

Sebelius said she was satisfied with the results of the investigation and the response of officials.

“My initial belief has also been reinforced,” Sebelius said. “Law enforcement and emergency personnel performed admirably under the most difficult of circumstances.”

The flooding occurred when a thunderstorm dropped heavy rains along the turnpike between 1:41 a.m. Aug. 28 and 9:30 a.m. Aug. 30 on soil that had been baked by several weeks of high temperatures and little precipitation. According to the report, the area received rain at a rate exceeding 5 inches per hour on Aug. 30, with 9.4 inches falling in a six-hour stretch.

It was determined that the culvert exceeded its capacity, allowing water to pool on the roadway and against the 32-inch concrete barrier dividing the north and south lanes.

Two engineering firms — HNTB Corp. and George Butler Associates Inc. — conducted concurrent studies of the section of turnpike and determined that even if current technology and design information had been available when the turnpike was constructed in 1955, more than 4 feet of water would have been on the roadway.

Engineers found that there was a problem in measuring the drainage area in 1955 when the road was built and that the concrete barriers, to some extent, “delayed the water’s flow from the road and increased the high-water measurement.”

Using measurements of the time, the report said, Jacob Creek was given a 7-by-7-foot culvert, but new estimates show it should have received a 12-by-8-foot culvert, improving water flow.

“The difference would have been minimal and the flooding equally deadly,” the report determined. “Not only did the storm exceed 1955 design criteria … but it would exceed the current design criteria for similar roadways.”

Turnpike officials responded to the flooding by subscribing to a weather-monitoring service, which provides specific data for each mile of the turnpike. Procedures for issuing warnings also will be improved to notify drivers along the route, and additional law-enforcement personnel will be sent to specific areas to monitor stream flows.

Additional monitors will be placed at two locations known to have flooded in the turnpike’s history.