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City crews are working in Brackenridge Park to drain a 500-foot stretch of the San Antonio River in Brackenridge Park this week as part of an investigation into how best to preserve remnants of bygone times.
Workers overseen by the San Antonio Parks and Recreation department will place two dams in a section of the river known as Lambert Beach, once a swimming hole in a crook of the river held up by a 1930s stone wall.
Lambert Beach lies across the river from the 1877 pump house that once diverted river water into San Antonio’s first public water system.
Plans to divert the river around Lambert Beach were originally scheduled for September, but frequent rains and a steady flow from the Blue Hole upstream at the river’s headwaters have delayed plans, Brackenridge Park Conservancy Director Lynn Bobbitt said.
“We can’t be disappointed about that, but it slowed us down,” Bobbitt said.
Emptying the river at Lambert Beach will allow experts to investigate the lower sections of the wall and pump house to see what kind of repairs are needed, Parks Assistant Manager Bill Pennell said.
“We’re able to shut this elbow of the river off,” Pennell said Friday, standing on an ornate metal bridge that spans the river over a shallow weir dam upstream of Lambert Beach.
During the investigation, sluice gates and pipes upstream will channel the river around the drained section, Pennell said.
Workers will cut off the river’s flow by pilling sandbags atop the weir dam and placing a bladder dam farther downstream under a pedestrian bridge, Pennell explained. He said the bladder dam looks “kind of like those bounce houses,” but filled with river water.
Before draining the channel, a consultant will use nets and other gear to pull fish and turtles out of the river and send them safely downstream, he said.
Plans to restore both structures were included in 2017 bond funds for Brackenridge Park last year. Voters approved $7.5 million to preserve and restore the river wall and other historic structures, including the pump house and traces of a 1776 Spanish colonial dam and associated irrigation ditches known as acequias.
The San Antonio Conservation Society is also contributing $300,000 over three years for work on the pump house, which architects have said might be the oldest intact industrial building left in Texas.
“This is work and restoration that needs to be done,” Bobbitt said. “It’s the opportunity to save the walls, the pump house, and the acequias before we lose these historic features.”
Pennell thinks Lambert Beach was last drained in the early 2000s. There’s no telling what crews will find at the bottom, Bobbitt said.
“There’s probably six feet of silt that’s piled up over the years,” she said. “It’s like cement, it’s so hard.”
The river could remain dry for six to eight weeks while the investigation proceeds, Bobbitt said.