Dallas' Flood Caverns

Hefner, John W.; Kwiatkowski, Thomas P.; Brock, Don O.; ,

Dallas' Flood Caverns

by John W. Hefner, (A.M.ASCE), Proj. Mgr.; Albert H. Halff Associates, Inc., Dallas, TX,
Thomas P. Kwiatkowski, (M.ASCE), Assoc.; Jenny Engineering Corp., Springfield, NJ,
Don O. Brock, (M.ASCE), Vice Pres.; Albert H. Halff Associates, Inc., Dallas, TX,

Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 3, Pg. 79-81

Document Type: Feature article

Abstract:

Dallas' North Central Expressway floods during heavy rains, but the dense development that helps create excessive runoff also precludes large detention ponds. The high-quality, low-strength bedrock and an existing (inadequate) drainage tunnel made detention caverns the best solution. The alternatives, tunneling or cut-and-cover construction through the soft ground, would have required extensive ground-water control, soil stabilization and underpinning of adjacent improvements. The caverns are among many modifications being made to the North Central Expressway (U.S. 75). The original outfall, the Mill Creek Diversion, has a capacity of 1,200 cfs, which is now enough for a two-year frequency flood. The SDHPT standard is a 50-year flood, in this case equivalent to about 5,400 cfs. The $28 million caverns, scheduled to be complete in the fall of 1993, will have a total volume of 71 million gal. When flood flows are greater than 1,200 cu ft/sec, the difference will be diverted from the bypass tunnel, flow over two weir structures and discharge into the detention vault. After the flood passes, the hydraulic grade line in the bypass tunnel will drop below the water surface in the detention vault and the vault will empty into the bypass. A pump station will empty the lower portion of the vault, which will be below the flow-line elevation of the Mill Creek Diversion.

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