Weather permitting, the city of San Marcos will begin the Rio Vista Dam maintenance and whitewater improvements project this week, with the goal of finishing by Memorial Day.

The city plans to repair the crumbling bank and transform the damaged low water dam into a series of whitewater rapids for swimming, tubing and kayaking.

Fencing will be installed on both sides of the river beginning Tuesday, blocking off access to the dam from both banks of the river.

The west bank reconstruction will take four to five weeks to complete. In-stream work to repair the foundation of the dam and create whitewater rapids is expected to begin by the end of March and take about eight weeks to finish.

Several consultants have been hired in the past month to work on different aspects of the project.

Halff Associates, Inc. of Austin, and Recreational Engineering and Planning of Boulder, Co., are two engineering firms hired to design the bank reconstruction, dam stabilization and whitewater features. Fugro Consultants of Austin has provided geotechnical services.

Greenway Inc. of Austin has been hired as the contractor for the bank work. Greenway will remove the existing retaining walls on the west bank, including the wall containing a painted mural.

Greenway will re-grade and slope the bank for a terraced sunbathing area, improving access from the swimming pool area and park.

The contractor will install buried "soldier pilings" near the existing gazebo to stabilize a remaining retaining wall and protect the bank during floods.

Numerous trees will be removed on the west bank near the dam, said Rodney Cobb, director of Parks and Recreation.

"Most are hackberry and ligustrum," he said. "One diseased oak tree will be removed and a small cypress tree will also be taken out. The trees will be replaced after the bank work is completed," Cobb said.

The century-old dam, located about a mile south of the springfed headwaters of the San Marcos River, was closed to the public in November after it was discovered that the foundations of the dam and embankment were in danger of collapse.

In December the City Council decided to redesign the dam into rapids to enhance the recreational value of the popular swimming hole as well as the safety of the dam. Since then staff has worked with state and federal agencies to obtain needed permits for the reconstruction work.