Old Lampasas Dam Modernization

This project will modernize the Old Lampasas Dam, located on a tributary of Bull Creek, off Spicewood Springs Road.

Status

On August 29, 2024, the Austin City Council approved the construction contract for this project. Construction is slated to start at the beginning of October. Please join us at a public meeting to meet the contractor and project team and find out more about the project.

5:30 p.m.
Tuesday, September 17, 2024
Canyon Vista Middle School, 8455 Spicewood Springs Road

Project Overview

The dam is currently in disrepair and is at risk of failing with a large enough storm. This could cause catastrophic flooding for about 30 homes and two roads downstream of the dam. This project will modernize the dam so that it meets City of Austin and State of Texas dam safety regulations and significantly reduce the risk of failure. Other benefits of the project include:

Increasing capacity of the dam and reducing flood risk downstream
Hardening the dam to help prevent erosion or failure
Improving water quality in Bull Creek downstream of the dam, including in St. Edwards Park
Maintaining habitat for the Jollyville Plateau Salamander

The project has many components including replacing the damaged outlet pipe, improving the spillway, modifying the shape and elevation of the embankment, installing new flood early warning systems and relocating a wastewater line.

Background Information

Built in 1984, the Old Lampasas Dam was built to offset the impact to Bull Creek of development occurring at that time. In 2010, the primary outlet pipe of the dam was damaged during Tropical Storm Hermine. Due to the condition of the outlet pipe and poor construction materials, the embankment as well as the downstream slope has eroded and continues to do so when it rains. Numerous holes have formed on the upstream slope of the dam. The eroding slopes are unsafe.

Project Map

Map of project area

Trees

Trees are important to us, but we are required to remove many trees that have grown up on the dam. This is a state requirement as well as a best practice for maintaining a dam. Trees compromise the safety and functioning of the dam and make it difficult to inspect the condition of the dam. To offset the impact, the City of Austin purchased an undeveloped tract nearby to preserve trees. We will also be taking bird nesting season into account to mitigate the impact to wildlife.

Staging and Construction Traffic

There are two staging areas for this project shown on the map above. There will be some construction traffic going from the staging areas to the dam. There will be temporary lane closures between the hours of 9 a.m. and 3 p.m., Monday through Friday. If work occurs on the weekend, the lane closures will be from 7 a.m. to 7 p.m. A message board and a speed trailer will be stationed along Spicewood Springs Road to alert road users of potential construction activities.

Timeframe and Cost

Our capital improvement projects take many years from start to finish. The process typically includes the following phases:

Preliminary Engineering – when a solution is identified and costs are estimated.
Design – when the details are worked out and construction plans drawn up.
Permitting and Bidding– when a contractor is hired and all permits are acquired.
Construction – when the project is built.

This project has received permits from the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service and the City of Austin. Construction is anticipated to begin in October 2024. The construction cost is estimated at $14.9 million.