Exploring what Sand Burr Cave is. Another one of Austin’s lesser known caves and karst features.

Sand Burr Cave aka Sand Bur Cave is one of Austin’s lesser known caves and karst features located in an environmentally sensitive area. This news article will explain what Sand Burr Cave is.

Sandbur Cave is a cave located in the environmentally sensitive area Edwards Aquifer.  This karst feature consists of a cave opening in a Kainer Formation outcrop in the far northern area of the Edwards Crossing 82 Tract. The opening measures about 5 feet long by 4 feet wide and is about 5 feet deep. The cave appears to open up and extend toward the west. The recharge potential to the aquifer from this feature is considered small due to the relatively small size of the opening and the limited contributing area to the feature. (Ref: https://www.researchgate.net/profile/Raymond-Slade-3/publication/304351769_Perspectives_of_the_Effectiveness_of_Structural_Runoff_Filtering_Systems_on_the_EdwardsAquifer_Recharge_Zone/links/576cbf1008aedb18f3eb30c5/Perspectives-of-the-Effectiveness-of-Structural-Runoff-Filtering-Systems-on-the-EdwardsAquifer-Recharge-Zone.pdf)

The City of Austin has used Sandbur Cave as a dye injection site, where they have injected rhodamine WT into the karst feature. (Ref: https://www.researchgate.net/profile/Raymond-Slade-3/publication/304351769_Perspectives_of_the_Effectiveness_of_Structural_Runoff_Filtering_Systems_on_the_EdwardsAquifer_Recharge_Zone/links/576cbf1008aedb18f3eb30c5/Perspectives-of-the-Effectiveness-of-Structural-Runoff-Filtering-Systems-on-the-EdwardsAquifer-Recharge-Zone.pdf)

The most recent tracer injection at Sand Burr Cave was in 2013 when a Rhodamine WT tracer injection was injected in the Bear Creek watershed. The most recent Rhodamine WT tracer injection before 2013 was six years prior at Sandbur Cave in 2007 in the Bear Creek watershed. This cave was selected in place of Flint Ridge Cave as an injection site since Sandbur Cave is near Flint Ridge Cave but is not a BCP permit preserve site. (Ref: https://bseacd.org/uploads/Report_OnionCkDyeTrace_20180831.pdf)

[Sandbur Cave lies near the extrapolated flowpath from 10A Hangtree Cave, from which eosine dye was detected in numerous wells. We interpret that the RWT injected in Sandbur Cave followed a different flow path than the eosine injected in Hangtree Cave, because both dyes were not detected together in monitored wells. One possibility is that the flowpath from 10B Sandbur is to the northeast and joins the Manchaca Flow Route at a point downgradient of wells where eosine was detected.]

Sandbur Cave is located about 1,200 feet (365 m) from proposed SH 45 SW and about 1,600 feet (488 m) from Flint Ridge Cave. Sandbur Cave does not have a passage which extends beyond about 15 feet. Siliceous remnants can be found inside of the cave. That is where those cladophyllia-bearing siliceous remnants come from. (Ref: https://www.austintexas.gov/watershed_protection/publications/document.cfm?id=196481)

Sandbur Cave is located on CoA Water Quality Protection Lands and is off limits to the public. Sandbur Cave located at the address of 12512 Red Mesa Hollow, Austin, Texas, US 78739.