Klotz Associates has been selected by the Chambers Liberty Counties Navigation District to provide professional services for planning, design and construction phase services associated with reconstruction of a 150-foot wide overflow spillway for Lake Anahuac in Chambers County. The low flow spillway passes stormwater from Lake Anahuac (freshwater) to Trinity Bay (saltwater).

 

Lake Anahuac is a source of freshwater for municipal, industrial and irrigation water users in Chambers and Liberty Counties. The lake supplies water to a canal system with over 100 miles of main canal and over 300 miles of laterals. Located at the upper end of Trinity Bay, flood surges of over 20 feet in height from Hurricane Ike destroyed about 4.5 miles of the earthen embankment and the low flow spillway. The top of dam elevation is approximately 8 feet above mean sea level and the crest of the low flow spillway is at elevation 4 feet msl.

 

The District is in the process of reconstructing the earthen embankment and is moving forward with reinstallation of the low flow spillway.  The current conceptual design for the spillway includes a reinforced concrete cap supported by rows of sheet pile driven to depths of 40 to 60 feet below sea level. Challenges identified for the project include the spillway foundation materials (reported by the District as “sugar sand”), energy dissipation as water flows over the spillway, toe scour at the upstream and downstream ends of spillway, the saltwater environment, water management during construction, use of the spillway as a roadway to travel along the dam and hardening of the spillway to improve survivability in future hurricane events.

Klotz Associates plans to use the services of Chambers County Land Surveying for surveying services and Terracon Consultants for geotechnical services. The current project schedule calls for six months to complete design and six months for construction.

City of Austin Fort Branch Channel Improvements
The Klotz Associates team surveyed portions of the channel and updated the hydrologic and hydraulic models for the watershed.  The team also conducted several field reconnaissance visits to the channel and photo documented it. Additionally, we performed a GIS evaluation of drainage area development conditions and extended the current hydraulic model upstream past US 290 to an approximately 64-acre drainage area.  More than 260 structures were surveyed to update City database information for the Fort Branch Channel.  Klotz Associates utilized updated information, hydrology, hydraulics, and slab data along with some high water marks calibrate the models to historical recent storm event.  The drainage area, parent development, location of houses in the floodplain, and the floodplain boundaries were prepared in our GIS ArcView computer system.  The team prepared several analyses to utilize available construction plans and reduce the structural flooding of homes and businesses.  Klotz Associates then prepared six alternative analyses and cost estimates to provide the best reduction in structural flooding for the least cost.  Options included structural improvements to the channel, culvert or bridge replacements, natural channel sections, and combinations of these options.  Klotz Associates also prepared a hydraulic analysis of storm sewers along a portion of Westminster Drive to evaluate system capacities and to make recommendations to provide more storm sewer capacity in this area.  Recommendations were submitted to the City of Austin in a report which documented the analyses, alternatives, and recommendations.