Eagle Mountain Dam and Lake (formerly Eagle Mountain Reservoir) are located about 5 miles northwest of Fort Worth, on the West Fork Trinity River in northwestern Tarrant County, Texas, USA. The dam is 85 feet (25 m) high and 4,800 feet (1.463 m) long with the top of the dam at an elevation of 682 feet (207 m) above mean sea level. It is owned and operated by the Tarrant Regional Water District (TRWD) for flood control, water supply, irrigation, and recreational purposes. Deliberate impoundment of water began on February 28, 1934.
Minimizing seepage in the foundational sandstone bedrock and protecting the water resource was of critical importance for TRWD. The Engineer, Freese & Nichols, designed a 265-foot (80 m)-long cut-off wall extending 60 feet (18.3 m) down into the sandstone foundation within the Eagle Mountain Lake Spillway Dam, in an effort to slow down the amount of water seeping through the bedrock foundation of the earthen structure.
BAUER Foundation Corp. (BFC) was awarded the execution of this cut-off wall by means of Cutter-Soil-Mixing (CSM) with a maximum depth of 18.3 m. In addition to Tube-à-manchette grouting with the objective of providing closure between the CSM alignment and spillway approach wall.
The cut-off wall was installed by BFC using specialized equipment that is capable of advancing into the soil by means of a double wheel rotary cutter, the rotating wheels breakup and mix the in-situ material while cement-bentonite slurry is pumped through a nozzle, creating a homogeneous soil cement mix that ultimately decreases the porousness of the soil, resulting in a significant reduction of seepage.
At Eagle Mountain Dam the cutter soil mixing panels were constructed in an alternating pattern. First an 8-foot (2.4 m) panel was executed (Primary). Then the equipment moved 6 feet (1.8 m) and executed another 8-foot panel (another Primary). Then, it returned to construct the missing connecting panel (Secondary) achieving an overlap of 0.3 m between panels.
Location
The site of the Eagle Mountain dam project is located approximately 5 km northwest of Fort Worth, Texas.
Scope of works
Geological conditions
Interbedded layers of weakly cemented sandstone and shale, with the uppermost sandstone layer being highly permeable, thus favoring water infiltration from the upstream side of the Dam.
Equipment
Construction period
April-June 2022