Upper Brushy Creek Dam 101 — Round Rock, Texas

Sundt Construction finished a $34 million flood control dam north of Austin in July 2026, and the numbers behind it explain why earthen embankment work is harder than it looks. Dam 101, built for the Upper Brushy Creek Water Control and Improvement District near Round Rock, runs nearly a mile end to end and stands up to 40 feet tall.

Project Scope

The structure is a zoned earthen embankment with a clay core, the classic configuration for a flood-detention dam: a low-permeability center wrapped in coarser fill that provides mass and drainage. Sundt self-performed the major scopes, moving 60,000 cubic yards of excavation and placing 190,000 cubic yards of zoned embankment.

The spillway is the interesting piece. Dam 101 uses a labyrinth weir running roughly 0.6 miles, a folded crest geometry that passes far more flow per foot of dam length than a straight weir. It’s the standard answer when you need spillway capacity and don’t have the width to get it conventionally. Building one means precise concrete geometry over a long run, where cumulative layout error compounds fast.

Crews also installed the drainage systems, a 60-inch steel outlet pipe and several concrete structures supporting long-term performance. Sundt won the project in 2023.

Why It Matters

The dam reduces flood risk for more than 1,000 residents along roughly five miles of Lake Creek, in one of the fastest-growing corridors in the country. Williamson County has been absorbing development at a pace that outruns its drainage infrastructure, and impervious cover upstream turns a design storm into something the original 1960s-era flood control network was never sized for.

That’s the pattern across Texas. Many of the small flood-detention dams protecting suburban Austin, Dallas and Houston were built by the Soil Conservation Service for farmland and now sit above subdivisions. Reclassifying them as high-hazard triggers a rebuild, and the district-level owners running these projects tend to be small agencies procuring their largest-ever contract.

Water work has been the steadiest segment in heavy civil for two years running, and the pending Water Resources Development Act would add $30.5 billion more. Dam 101 is what that money buys: unglamorous, mile-long, and the difference between a wet street and a flooded one.

Project Team & Details