Highway on the Aquifer (Oak Hill Parkway)

Please see the letter below detailing SBCA’s position on the Oak Hill Parkway.


Save Barton Creek Association

October 29, 2018


Re: Environmental Concerns regarding Oak Hill Parkway

To: Mayor Adler and Austin City Council

Cc: Mike Kelly, Ed Peacock, Chris Herrington, Environmental Commission


Save Barton Creek Association (SBCA) has serious concerns about the “Oak Hill Parkway” project. This construction project on highways US 290 and State Highway 71 West in Austin has a huge footprint in an environmentally sensitive area. It is likely to significantly degrade the Barton Springs Edwards Aquifer, local springs and wells, and waterways, especially Williamson Creek. The City of Austin and its citizens will be greatly affected by this project. We implore the Austin City Council to get involved and work with TxDOT to improve the project.


The proposed highway expansion is over the Trinity and Barton Springs Edwards Aquifers. According the Draft Environmental Impact Statement (DEIS), 64 percent (255.55 acres) of the project area lies over the contributing zone of the Barton Springs Edwards Aquifer, while 36 percent (140.09 acres) is in the recharge zone.


The project intersects with Williamson Creek which is hydrologically connected to Barton Springs and Cold Springs. According to Nico Hauwert, preeminent hydrogeologist studying the aquifer, “Since we started tracing Williamson Creek in 1997, we showed a much higher sensitivity to Barton Springs than what was previously known. Groundwater from Williamson Creek could reach it as fast as 1-2 days as opposed to years referenced in the 1989 SH45SW EIS.”


This fast recharge means that construction sediment, run-off pollution, or spills from the highway would affect local wells and Barton Springs Pool almost immediately. The project area also crosses over the Barton and Slaughter Creek watersheds.


The DEIS lists 6 known karst recharge features in the project area. Several are immediately adjacent to proposed excavation. The DEIS did not discuss the impacts to nearby Gaines Sink and Flea Market Sink, which could also be affected.


This project proposes approximately 74 acres of new impervious cover. Impervious cover decreases recharge by blocking recharge features and removing vegetation; and decreases water quality through run-off pollution.


While SBCA encourages the use of Best Management Practices (BMPs) during construction and water quality ponds to treat run-off, even the best BMPs and water quality treatment features will not be able to fully mitigate the enormous environmental impacts of this project. For example, construction BMPs may fill large voids (recharge features), but the karst environment will transport pollutants through small unmitigated features as well. Further, lack of available land in the right locations will render it impossible to fully treat all of the run-off from this project.


Below, we make recommendations for substantive project changes and for mitigation through BMPs that would lessen environmental harm. Save Barton Creek Association implores the City of Austin not to enter into contracts or dedicate funds to this project unless TxDOT will work with the City on the below recommendations. 


Recommendations for TxDOT

  • Remove the 2.65 miles of excavation from the project. Excavation is arguably the most significant impact this project will have on water quality and quantity in the Barton Springs and Trinity Aquifers. The proposal would dig up and remove 1,968,000 cu yards of earth and rock, digging 25 ft into rock above the aquifers. For perspective, that is more than the entire volume from floor to ceiling of the Astrodome, 3/5 the size of the Great Pyramid of Giza,[1] or more than three feet depth covering I35 from Austin to San Marcos.


Excavation poses numerous problems. During construction, scraping this much earth will lead to significant sedimentation in the aquifer, creek, and recharge features. The excavation will also cut off underground flow paths. Based on his hydrologic studies, Nico Hauwert says  that water held in the Upper Glenrose Formation “typically discharges from springs or may flow in the subsurface to the Edwards Aquifer. Excavations in the Upper Glen Rose Formation may potentially redirect shallow flows from their original destination or replace it with new sources such as roadway runoff.”


Excavation was not in the original project scope and was only included in the most recent proposal due to neighborhood concerns about a triple decker highway at the Y. Neighborhood residents were seeking an at-grade parkway, not excavation.


When asked what the alternatives to excavation could be, TxDOT team said “The alternative to excavating would be to have the mainlanes raised which is opposite of the community feedback we have received through the years.  Currently we are going no higher than the existing Pizza Garden. Otherwise, the overall height would be increased.”


This response is not an adequate analysis of alternatives. The original twelve lanes in the project incorporated six tolled mainlanes and six non-tolled parallel frontage road lanes. This is now planned as a completely untolled project and citizens in the Fix 290 coalition have argued that therefore access lanes are unnecessary in the critical piece of the project near the Y which sits between a cliff and Williamson Creek. We agree.


TxDot should not excavate. Instead, they should remove access lanes between the “Y” intersection and the US 290 bridge over Williamson Creek. They are already acquiring two commercial properties and one residential property as part of this project. Buying out three more businesses eliminates the need for access roads in this area. If absolutely necessary, they should return to entirely elevated lanes instead of depressed lanes in other areas of the project.


While we hold that no excavation is necessary in this project, it is especially important that no excavation is done from the Y to William Cannon, because the Balcones Fault Zone will rush this sediment into the aquifer. The DEIS lists 6 known karst recharge features in the project area, including several immediately adjacent to proposed excavation.


Furthermore, the DEIS recognizes several endangered species including the Austin Blind Salamander and Barton Springs Salamander that could be impacted by this project. We know that these amphibians are very sensitive to pollution. This project is in an environmentally sensitive ecoregion, and as such it is not appropriate to excavate.


  • Act sensitively toward Williamson Creek. This should include a detailed mitigation and restoration plan for areas altered through overbank mitigation to increase ecological function over pre-construction conditions; as well as preservation of bottomland riparian vegetation and creek ecology; and preserving adequate space on either side of the creek for riparian habitat and a greenbelt trail.

The current plan calls for conducting overbank mitigation of Williamson Creek in 4 locations, or for a total of 2,700 feet. TxDot says that they are revising their schematics so this number may change. Overbank mitigation, also called benching, widens the channel starting 5 feet above the bottom of the creek. This preserves the ecology at the center of the creek, and if properly planned, allows the riparian ecosystem to heal.


According to the Watershed Protection Department at the City of Austin(COA Watershed), “The worst losses, from a floodplain and riparian perspective are in and around the 290/William Cannon intersection, where some of the best bottomland vegetation occurs in the wide channel there…there will be significant removal of mature riparian vegetation, including large sycamores, willows and cottonwoods.” Local citizens are also aware of mature bottomland vegetation and bedrock lined pools, with possible recharge features, upstream of Old Bee Caves road that is also slated for overbank mitigation.  For this reason, TxDot should re-evaluate their plan by more accurately describing the conditions in these two areas and avoiding damaging this high quality riparian habitat.


In the other overbank mitigation locations, TxDOT should provide a detailed mitigation and restoration plan as part of the Construction Environmental Compliance Plan and also include these actions in bid items and call-outs on the construction plan sets. TxDOT did this in the SH45 project. Through these actions, the benched areas will be able to recover.


Austin’s Watershed Protection Department “expects to see these benched areas recover, assuming they get robust restoration treatment, including follow-up to insure sufficient diversity, cover and removal of invasive species.”


We also suggest preserving adequate greenbelt on either side of creek that supports ecological function and improves the atmosphere around the proposed shared use path. SCBA does not support the channelization of Williamson Creek near William Cannon or in healthy bottomland habitat upstream of Old Bee Caves Road, and instead recommends that the design avoid this sensitive habitat. We also want to see a restoration plan that includes the input of COA Watershed Protection.


  • Comply with DEIS Comments from Austin Watershed Protection Department. TxDOT should work with Austin Watershed Protection Department as a partner. Watershed has offered to build and maintain the water quality ponds as a part of this project. This gesture should be met with a commitment by TxDOT to provide funds for the purchase of Water Quality Protection Lands. TxDOT should be asked to provide funding for Water Quality Protection Lands because (1) due to available land area in the right locations, run-off may not be fully mitigated and (2) because this project will speed up development over the Barton Springs Edwards Aquifer, through the proven concept of “induced demand”. Increased highway capacity will lead to increased development and use of that capacity. The City of Austin will need to purchase more water quality lands to maintain water quality at current levels, because of the impact of this project.


TxDOT should comply with the other recommendations in Watershed’s DEIS comments including flood detention requirements, and inviting COA Watershed to contribute as part of design team through design, prevention, inspection, and mitigation of voids. We also recommend TxDOT work closely with the Barton Springs Edwards Aquifer Conservation District(BSEACD) on these plans, also allowing them to participate in design, prevention, inspection, and mitigation of voids.


  • Avoid Historic Oak Trees to the maximum extent possible. The DEIS states that the project will remove 281 trees greater than 10 inches DBH. Many of these are trees that are legacy, heritage, or protected trees by City of Austin standards. Oak Hill citizens conducted a tree study that can be found at SaveOakHill.com that geolocates the trees, indicates their size, protected status according to the City of Austin regulations, and includes photographs. We have not yet seen a study from TxDOT that shows exactly which of these trees will be taken by the project. TxDOT should work with the COA arborist to ensure the plans do in fact save trees. For example, it looks like even “saved trees” in the plan will have their root zone cut into, likely killing the trees. They should also pay close attention to the proposed overbank mitigation to avoid these protected trees.


The project should do everything possible to protect legacy and heritage trees and specifically should protect the trees and habitat that are part of the bottomlands of Williamson Creek near William Cannon Drive and upstream of Old Bee Caves Rd.


  • Include the points below in the Construction Environmental Compliance Plan. This plan should be drafted through collaborative meetings with COA Watershed Protection, environmental nonprofits, and the Barton Springs Edwards Aquifer Conservation District.
  1. Utilize Best Management Practice (BMP) construction phase erosion and sedimentation controls to protect aquifer and Williamson Creek to the maximum possible extent.
  2. Avoid recharge features encountered during construction, not just filling potentially significant features. The design-build nature of this project gives the opportunity to change the design if these features are encountered. Clean water should be diverted to recharge features, avoiding roadway run-off reaching these features.
  3. Work with Barton Springs District and COA Watershed Protection on Void Mitigation protocol. Allow COA and BSEACD to monitor any voids encountered during construction.
  4. Hazardous material spill plan and infrastructure, since a spill could almost immediately affect nearby wells and pollute Barton Springs and threaten endangered salamanders within two days. This may include a plan to shut down the water quality ponds if hazardous materials were to enter them.
  5. Proper protocol for saving protected trees including input from COA arborist
  6. Proper protocol for restoring creek habitats after overbank mitigation, including appropriate plantings.
  7. COA environmental staff and BSEACD have the right to oversee construction and environmental compliance.


Save Barton Creek Association strongly urges the Austin City Council to pass a resolution that identifies the City of Austin’s goals as they relate to this project, and direct staff to negotiate with TxDOT for these community and environmental benefits.


A City Council Resolution might include reaffirming the prior council’s support for a ‘parkway concept,’ trying to get this project as close to possible to meeting that ground-level roadway design vision. It should also lay out the priorities for watershed protection above, including a taking position against excavation in this project. It should also ask TxDOT to work closely with COA staff including transportation and environmental staff.


Further, a resolution should give council, not staff, the authority to enter into contracts with TxDOT to ensure that city-wide community needs are being met, and that valuable leverage is not given away. Council approval of any contract or funding connected to this project should be based on a conclusion that the project will improve traffic flow without significantly damaging the aquifer, environmental resources, or nearby neighborhoods. The City needs to be creative in partnering on this project, offering resources and funds including 2016 bond funding only if the project will not harm the qualities that make Austin so special.


In the Imagine Austin Comprehensive Plan, the project area was in the Oak Hill Activity Center, which was defined by a mix of uses and multiple transportation options. This project must be built in such a way that it preserves water and environmental resources and gives future citizens of Oak Hill a high quality of life, including the opportunity to walk and bike along Williamson Creek, and utilize future public transit.


Please consider the importance of this project to Austin’s future. What is Austin without Barton Springs? What is Oak Hill without its heritage oaks?


Thank you for considering this important matter.



Angela Richter

Executive Director

Save Barton Creek Association


[1]            http://www.bluebulbprojects.com/MeasureOfThings/results.php?amt=1968000&comp=volume&unit=cy&searchTerm=3+cubic+yards%2C+a+measure+of+volume)