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Crews are working to drain a section of the San Antonio River at Brackenridge Park for the second time in two years to work on an aging section of river wall.
Workers first attempted in Fall 2018 to build dams to isolate a section of the river, where parts of the channel built in the early 1900s through the 1930s are deteriorating. The area is known as Lambert Beach, a popular swimming hole in the early 20th century when people were allowed to swim in the river.
Though dam construction began this week, the actual draining is likely to happen the second week of March, with the channel staying dry for about two months, said Bill Pennell, assistant manager for the City’s Parks and Recreation Department.
Crews attempted a similar task in October 2018, but frequent rains left the water table too high and flows from the Blue Hole, the headwater spring of the San Antonio River, and other nearby springs too intense to lower the water enough to get the work done, officials with the City and Brackenridge Park Conservancy said.
“[The dams] just could not keep the water out,” Brackenridge Park Conservancy Director Lynn Osborne Bobbitt said.
Contractors with San Antonio-based Amstar are this week building coffer dams on either side of the 100-foot section of river from a pedestrian bridge to a vehicle bridge, then using sluice gates to divert water around the main river channel. Officials prefer the technical term “dewatering” when they speak of drying out the river bed.
Like other sections of the river downtown, the stretch at Lambert Beach is lined with a concrete channel, Pennell said. That will allow architects with Houston-based SWA Group to assess the conditions of the historic stone walls, he said.
“We need to be able to do an investigation and figure out what the issues are so they can design the appropriate repairs,” Pennell said.
Voters in 2017 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
The City had water removed from a small section of the river under the 1877 pumphouse last summer, Pennell said. Architectural experts say the structure could be one of the oldest intact industrial buildings in Texas.
“It was actually in better shape than we expected,” Pennell said.
As part of lowering the river level, federal and state wildlife officials signed off on permits to allow contractors to move native fish and other aquatic life to the other side of the dam, Pennell said.
As always when parts of the river are drained, there could be surprises, including nonnative species that workers typically kill and send to the landfill.
“There’s always going to be something interesting,” Pennell said. “I’m sure we’ll find some fish we didn’t expect to be there. You just never know.”