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Lake Brazos Labyrinth Weir, 2008 OCEA
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The Lake Brazos Labyrinth Weir was commissioned by the City of Waco to replace the Lake Brazos Dam, which had posed maintenance and operational problems and was unable to provide the stable lake levels that would be ideal for downtown development. Freese & Nichols refined the initial concept and were able to design the project in a way that eliminated the costly need to divert the river, empty the lake for construction, or to build downstream of the existing dam by constructing the weir in two phases over the foundation of the existing dam. The concept underwent extensive modeling to determine the most advantageous configuration and to develop optimal phased construction processes and river management practices. Ultimately, the design and construction of the weir was successful, allowing the City of Waco to benefit from reliable lake levels at nearly half the cost of earlier estimates.

 

In addition to minimizing cost, engineers were able to limit disruption to lake levels during construction through the phased construction process. Existing hydraulic gates remained operable while the left labyrinth was constructed and work started on the right labyrinth only when the left was completed and river flows were passed over it. Additionally, city-approved lake lowerings were accommodated at pre-determined times to facilitate specific work items. Although initial progress put the project five months ahead of schedule, heavy rains late in the construction process caused river flows to exceed 20,000 cfs and delayed completion of the right labyrinth weir, which had originally been scheduled for September, until October 2007. Despite the inconvenience, the floods in March and July offered a full-scale test of performance of the left labyrinth weir, which completely validated expectations while still in the construction phase. The weir has continued to perform as designed and has enabled city planners, developers, and businesses to look to downtown for events and development as steady lake levels have at long last become a reality in Waco.   


Owner: 
The City of Waco, Water Utilities
Engineer: 
Freese and Nichols Inc.
Contractor: 
Archer Western Contractors Ltd.
Photo: 
Freese and Nichols Inc.

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