Just in Time for Memorial Day, Rio Vista Dam Open Again

May172nddrop.59.jpg Rio Vista Dam, about a mile south of the San Marcos River headwaters, was opened to the public again yesterday after several months of reconstruction work. The dam was deemed unsafe last November, after its foundation was discovered to be in danger of collapse. The San Marcos City Council decided in December to restructure the entire dam into its current design: three separate tube drop chutes buffered by pools of water, with a terraced river bank for sunbathing.

Ignorant as we are of any reconstruction efforts more complicated than replacing a toilet seat, the 47 day, $2.4 million project sounded awfully complex:

May11.29.jpg (from a press release)

Installation of two parallel 48-inch wide pipelines from the left bank of the dam to an area 370 feet downstream just above the Cheatham Street bridge.
Installation of a 12-inch pipe and valve near the outfall of the diversion pipes that will direct flowing water over four stands of Texas Wild Rice, an endangered plant that grows only in the San Marcos River. Protective barriers have been placed around the wild rice stands in the river.
A port-a-dam has been installed from the left side of the dam up river about 100 feet. The temporary dam is diverting flow away from the existing dam into the pipelines.
The “dewatering” process around the dam was completed April 24. Teams of firefighters and City employees swept the area with seines, nets and buckets above and below the dam to capture and release fish and other aquatic animals.
Both rock and concrete grout will be used to fill in underneath the dam where it has been undermined by decades of swift river flows and periodic floods.
More than 3,000 tons of rocks are being transported in stages to the site over the next three weeks for use in rebuilding the dam and the two downstream drop structures.
Retaining walls on the right bank are being removed. The bank will then be sloped back to create a sunbathing and spectator area.