Gravel Bar Q&A

15 Nov 2009 by admin, Comments Off on Gravel Bar Q&A

Here, we offer answers for a few questions we have received regarding removing the Barton Springs Pool gravel bar.

Q: Is the gravel removal project a Monster Dredging process that will kill every living thing in the dredge zone?

A: Absolutely not. The gravel removal project is driven by the need to return the pool to a more natural state. There is nothing natural about the gravel bar: it is a huge pile of rocks, sludge and sediment washing from upstream against a man-made dam, and it is filling the deep end of the pool. The accumulated gravel has covered and suffocated the aquatic life that once inhabited the pool bottom in that area. The ecosystem of the pool is managed by Watershed as part of the mandate to protect the salamander. They have introduced plants and will continue to work towards promoting the growth of plant and animal life in the pool that will improve the conditions for salamander habitat and not interfere with the swimmers.

Q: How will the Pool benefit from the gravel removal project?

A: It will make the pool cleaner and easier to keep clean. This project will increase water flow in Barton Springs Pool. If left to its own devices, the pool will eventually fill completely with sediment that make up the gravel bar (silt, rocks, and boulders), and we can go and hang out on the Barton Springs Gravel Bar, because there will be no pool. The amount of time for this to occur can be calculated by simply dividing the volume of the pool by the volume of total accumulated sediments, and then multiplied by the time it took for that volume of sediments to collect. The removal of the gravel bar has the potential to reduce the amount of silt kicked up by swimmers during high use times because the silt would be in 10-15 ft. deep water. It also provides the opportunity to explore more routine methods for management of sediment accumulation in the pool during spring cleaning and the weekly Thursday closing of the pool for cleaning.

Q: Will the gravel removal project wash away the underpinning of the bypass tunnel?

A: No. The gravel bar is not supporting the bypass tunnel: it was not there when the city built the tunnel. The only relationship that the gravel bar removal project has in common with the bypass tunnel project is that they both require pool closure to complete. They should not be done together because the potential of the unique challenges of each project should be dealt with in separate projects.

Q: Why not have an incremental plan to remove accumulated gravel over a period of 15 years?

A: Once this huge mass is removed, we can have an incremental plan. An incremental plan was proven to not be effective with the attempt to vacuum the gravel back in 2006. This mass of gravel needs to be removed to allow BSP staff to explore gravel removal options that fit into the spring cleaning shut down, but that cannot happen unless we start with a clean slate.

Q: One reason to remove the gravel bar is to increase water flow to lessen the amount of nuisance algae. Why has this type of algae has not been nearly as bad as it was in previous years and why must we still remove the gravel bar?

A: Algae reduction was accomplished through the volunteer efforts by FBSP and Watershed managing the ecosystem of the pool better than in the past. There are a lot more challenges ahead to improve this even more, and the removal of the gravel bar is an integral part of providing that opportunity.

Q: Should we complete the flow studies approved in the Master Plan before removing the gravel bar?

A: No. The gravel bar is blocking the completion of scientific studies at the pool. The Master Plan process identified six short-term water quality studies for the pool. One, a topographic survey, can’t be finished because the buried bottom of the pool can’t be surveyed, and another, the hydrodynamic study, waits on the completion of the topographic survey.

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