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Planning Commission OKs removal of gravel bar in Barton Springs Pool

Monday, December 14, 2009 by Bill McCann

The Planning Commission has unanimously endorsed city code changes that would allow the city to use a large crane to remove a growing gravel bar in Barton Springs Pool.


At last week’s meeting, the Planning Commission joined the Environmental Board and the Parks and Recreation Board in supporting the pool maintenance project, which was included in the Barton Springs Pool Master Plan adopted by the City Council last January.


The Council on Thursday set a public hearing for Jan. 14 on the proposed code changes. 


Past floods on Barton Creek have pushed rocks, sediment, and gravel into a pile trapped in the Barton Springs pool just upstream from the dam, creating what city staff says is a safety concern for swimmers at the pool’s deep end.


As a result, the staff is proposing to move a crane temporarily to the pool’s south lawn next fall to dig out and haul away by truck about 2,000 cubic yards of rocks and other debris. To get the crane in place, staff proposes to build a temporary mulch-covered road near the south entrance of the pool and a specially designed pad for the crane to sit on to minimize impacts. A coffer dam would be installed around the gravel bar to keep water out while the crane is at work. The total cost of the project currently is estimated at roughly $600,000.


City staff says the pool would have to be closed for three to four weeks while the work is under way.


To do the pool maintenance work, the city will need to amend the Save Our Springs section of the city code and get a variance from the Critical Water Quality Zone section of the code. 


At its meeting, the Planning Commission heard from half a dozen speakers who supported the project and two who did not.


The most vocal critic of the project has been Ziola Vega-Marchena, who once again expressed concerns about the environmental impacts of digging out the gravel bar with a crane. She told the commission there is no hurry to remove the gravel and wants the city to do a water-flow modeling study of the pool before deciding what, if anything, to do about the gravel bar. Among other things, Vega-Marchena said she is concerned that massive digging by the crane could disturb contaminated sediment deposited by past floods. (City staff indicated a flow study, which is being planned, would take about 18 months to complete, including negotiating a contract and carrying out the study.)


On the other hand, the project has had a number of supporters, including the Friends of Barton Springs Pool. Several members of that group were among those speaking in support of the gravel bar removal. Calling the project “deferred maintenance,” Robin Cravey, president of the Friends group, told the commission that removal of the gravel bar was long overdue.


Cravey sent a letter to the Council last month to urge moving forward on the project.


“Removing the gravel bar is part of an overall effort to restore the pool to a more natural state,” Cravey wrote. “The giant bulge grows inexorably, slowly filling the pool and increasing stagnation. It also traps silt, building up a deep, oozing sludge on the bottom behind its rocky wall. When the pool is full of swimmers, they stir up the sediment, turning the water thickly murky.”


In voting for the project, Commissioner Dave Anderson expressed confidence in the expertise of city Watershed Protection staff to do the right thing to protect the pool and the endangered Barton Springs salamander that lives there.


Commissioner Danette Chimenti pointed out that there would be considerable oversight of the project as it proceeds, including oversight by the joint committee of the Parks and Recreation and Environmental boards.


One problem caused by the gravel bar occurs when lifeguards at the pool use a fire hose at the deep end to try to wash accumulated silt downstream, Tom Nelson, aquatic division manager at the Parks and Recreation Department, told In Fact Daily. 


“When they (lifeguards) reach the gravel bar, the silt just sits there and does not wash away,” Nelson said. “Also, in the mornings the water may be clear, but by afternoon, especially when a lot of people are using the pool, the silt is stirred up and the water is murky and makes it very difficult for the staff to guard.”


The gravel bar has been building up for years as periodic floods have washed huge amounts of rock, sediment, muck, and other debris into the pool. The dam creates a barrier, so the debris piles up behind it. In 2006, the city hired a contractor to remove the gravel bar by sucking out the material with huge vacuum equipment. But the vacuuming resulted only in taking out smaller rocks and silt. The city then hired Weston Solutions, which is developing a plan using the crane and trucks to remove the bigger debris.


If the Council approves the code changes in January, city staff plans to brief the Environmental and Parks and Recreation boards on final plans before taking a contract for the gravel removal to the Council for approval in the spring or early summer, David Johns, hydrogeologist at the Watershed Protection Department, told In Fact Daily. 


City staff will also be working with the U.S. Fish and Wildlife Service, whose approval will be needed because of the endangered salamander, Johns said.


The city plans to coordinate the gravel-removal work with the renovation of the bypass culvert built in 1975 to divert minor floodwaters at the pool, according to Johns. Doing both projects around the same time will help minimize the time that the pool will have to be closed. City staffers have been studying several repair options for the bypass after finding cracks and holes and other damage.

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