The Upper Brushy Creek Water Control and Improvement District owns and operates a network of 23 flood control dams across Williamson County, Texas. This complex watershed is located within “flash flood alley” along the Balcones Fault – in one of the most rapidly developing regions in the nation. One of the dams within this watershed had been compromised for more than a decade. The District called in Schnabel to take on the issue.

Longitudinal cracking and shallow slides had been observed on the downstream slope at Dam 14 since at least 2004. In 2018, the District performed a risk-informed dam safety assessment of all of their dams with the goal of prioritizing future dam safety actions and projects. For Dam 14, slope stability improvements were recommended to address the longitudinal cracking and shallow slides.

The District selected Schnabel to focus on the Dam 14 rehabilitation project in 2020. Voters approved funding for additional engineering and rehabilitation at Dam 14 and other district dams through an $85M bond program. During an initial assessment phase, Schnabel performed a subsurface exploration, a hydrologic and hydraulic evaluation, an integrity/stability analysis of the vegetated auxiliary spillway, and an evaluation of alternatives to address slope instability and spillway upgrading measures.

In 2021, as a follow-up to the assessment phase, the District retained Schnabel to prepare a preliminary rehabilitation design. During preliminary design, the Schnabel team performed pairwise analysis of the various embankment and spillway alternatives to refine the overall design concept. The preferred alternative included the reconstruction and stabilization of the downstream slope and crest with lime treated earthfill (Phase 1), and construction of a cutoff wall through the auxiliary spillway to protect against headcut erosion. Schnabel completed the design of Phase 1 in 2022. Construction of Phase 1 will be complete in early 2024.