KXAN Austin

Why are some Austinites finding sinkholes in their yards?

Investigative Summary:

What if the city’s underground infrastructure was changing the foundation of your biggest investment? That’s what some Austin homeowners say is happening to them as sinkholes form at their homes around Austin’s aging stormwater pipes. KXAN investigated Austin’s storm system and found this infrastructure, intended to prevent erosion and flooding, is largely uninspected and in unknown condition.

AUSTIN (KXAN) — Michael Sanford looks at his backyard and wonders if he’ll ever see a permanent fix. Exposed by heavy rain, a large sinkhole formed there around an underground City of Austin storm drainage pipe.

“It was very deep,” Sanford said. “It was about five feet deep, 12 feet wide.”

After we first brought you this story in June, the city filled the hole with rocks.

“If they told me this was the final solution, I’d be throwing a fit,” the homeowner said.

The city’s underground inspection revealed a deeper cause for the erosion: the stormwater pipe had corroded.

In an internal email from June, Austin’s then-Watershed Protection Assistant Director said it “does not appear to have a bottom” and “needs to be pulled and replaced.”

Sanford said he hasn’t gotten many answers from the city since it temporarily filled the hole.

“Any heavy rain is going to pull that rock through,” he said. “The biggest concern for me is — a child falls in during a rain event.”

From his backyard Michael Sanford speaks to KXAN’s Kevin Clark. (KXAN Photo/Ben Friberg)

The city’s Watershed Protection Department told KXAN it is working on a fix to relocate the drainage system. It first unsuccessfully tried to purchase an easement on a neighboring property, then recently partnered with the property’s owner to get temporary construction access.

“[Watershed Protection] is currently finalizing a solution for the infrastructure repair that we plan to present to the neighborhood,” a department spokesperson said. “We have begun work on design and permitting while also working with a contractor. Our goal is to start construction by the end of this year.”

The solution won’t be simple. Sanford is far from the only one affected; the corroded pipe runs under nearly 20 homes in the Villages of Shady Hollow subdivision in south Austin. Sanford and his neighbors have counted five sinkholes along the pipeline so far.

“One neighbor has bought flood insurance,” Sanford said. “Another neighbor has put in a retention wall.”

Photos of the sinkhole in Michael Sanford’s yard from June, along with the rusting stormwater pipe below his and his neighbors’ properties. (Courtesy Michael Sanford)

‘It started getting bigger and bigger’

Twenty minutes away live Barrett and Nicolet Morgan.

“We were really excited when we bought this home,” Barrett said.

Barrett and Nicolet Morgan. (KXAN Photo/Ben Friberg).

The couple bought their Travis Heights home in 2012 and learned the stormwater system under their property was active two days after they closed on it.

Now, along that underground line, they’re seeing pockets of erosion, including a sinkhole in their front yard.

“I don’t want my three or five-year-old stepping off their porch and falling into a hole,” Barrett said.

The city, which promises a fix here, too, told us it believes ground water is entering through cracks in the pipe, leading to the erosion and loss of soil. It estimates the pipe was constructed between 1915 and 1937, meaning it could potentially be more than 100 years old.

“At the time of construction, the City did not have standards or criteria that regulated the design or construction of storm drain systems,” a Watershed Protection Department spokesperson told KXAN. “As a result, the current storm drain system is not up to current City requirements or standards.” 

Long-term, the department tells KXAN it’s investigating realigning the pipe into the right-of-way.

“I’m trying to voice my concerns and be the squeaky wheel, so they can see this as a problem that needs to be addressed,” Barrett said.

How well does the city know its stormwater system?

Austin has nearly 1,200 miles of stormwater pipe. The system, maintained and inspected by Watershed Protection, is intended to store, treat and discharge stormwater runoff to prevent adverse flooding and erosion.

However, a Comprehensive Infrastructure Assessment from 2019 notes that several legacy infrastructure
networks are not built to standards not able to meet the current demands on those networks. The document notes this is a particular issue with the stormwater network, where “deficiencies have potential health, life and safety impacts.”

“Before a certain time frame in the 1970s and 1980s, the criteria for the storm pipes didn’t necessarily have reinforced concrete pipe,” said Jorge Morales, Director of Austin Watershed Protection.

With several families experiencing sinkholes, we wanted to know how often Watershed Protection inspects and repairs its stormwater infrastructure.

Our investigation found, the system meant to protect Austinites from flooding and erosion is less scrutinized than other types of city infrastructure.

According to Austin’s Long-Range Capital Improvement Program Strategic Plan, the city has labeled 93% of its storm drain pipe in “unknown condition” while the condition of its manholes and inlets are also labeled as unknown.

According to the Comprehensive Infrastructure Assessment, which is included in Austin’s Long-Range Capital Improvement Program Strategic Plan, the condition of 93% of the city’s stormwater pipes is unknown. (KXAN Graphic)

Compare that with Austin’s water utility: none of its water and wastewater pipes are in unknown condition, according to the infrastructure assessment within the Capital Improvement Plan.

“What would the reason for that be?” KXAN Investigator Kevin Clark asked Morales.

“I think it probably has to do with the age, the time we’ve had our program relative to the water utility,” Morales said. “From an asset management standpoint, they’ve probably been doing things for a lot longer.”

A department spokesperson added because there are so many storm drains in the city, “inspections require quite a bit of time and resources. In addition, this infrastructure does not face the same state and federal regulatory requirements as some of the other infrastructure within the City of Austin.”

These requirements are referring to Texas Commission on Environmental Quality, or TCEQ, regulations that require all sewage collection systems to be tested every five years. That does not apply to storm drain infrastructure, the city said.

Morales said Watershed Protection inspects drain pipes by putting cameras in them to keep track of inventory and identify potential problem spots. This is part of the department’s Asset Management Plan, which looks at the age, condition, material and size of the city’s storm drain pipes.

A view from inside one of the city’s drainage pipes. Austin’s Watershed Protection Department uses cameras to proactively inspect its pipes. However, the department is budgeted to only be able to inspect 1% of its inventory per year. (City of Austin Photo)

Proactive monitoring is slow; Morales said the department has inspected about 100 of its near-1,200 miles of pipe since it began inspecting pipes 10 years ago. A city spokesperson added the Watershed Protection Department’s budget allows it to inspect 1% of its storm drains annually and that pipes are not repeatedly inspected because of “limited resources.”

The department said through its Asset Management Plan, it has identified 75 miles of high-risk storm drains to be prioritized for inspection. It says at the department’s current rate, it will take nearly five years to complete.

Despite the city’s own reporting of its manholes and inlets in unknown condition, the department says it visually inspects and cleans manholes and inlets on a recurring two-year cycle.

“We’re trying to be strategic based on risk, based on age and material type, where we get our eyes on some of those pipes,” Morales said.

Meanwhile, in his backyard, Michael Sanford hopes for more urgency in conducting proactive inspections.

“I know there’s miles and miles of it,” he said, “But waiting to react doesn’t seem like the right solution.”

For Barrett and Nicolet Morgan, their home is their biggest investment. They even bought the property next door, in preparation for the possibility of physically moving their home off the stormwater system, in case the city doesn’t realign the pipe.

“The hard part is when I asked the city if this was a safe place for my children and my family to be, they couldn’t give me that answer,” Barrett said.

A challenge for cities

UT Professor and Civil Engineer Ben Hodges. (KXAN Photo/Chris Nelson)

For more perspective, we spoke with Ben Hodges, a UT Professor and Civil Engineer who has expertise in stormwater systems and fluid mechanics.

We asked: is it possible for cities to know the condition of its stormwater pipes, in order to proactively prevent sinkholes and other issues?

“As a professor, I can say, theoretically, we can do it as a practical matter,” Hodges said. “The question would be the costs associated with the surveying, the landscape around understanding where the possibilities are.”

Hodges mentions budget constraints, adding cities tend to put stormwater systems on the backburner when there’s a crunch in city budgets. Problems with stormwater systems tend to be more isolated and less obvious to the general public.

“We see the roads every day and when the roads get bad, people are complaining because they’re driving over potholes,” Hodges said. “But when the equivalent of a pothole occurs in a stormwater drain, who sees it?”

He said Austin is far from alone in facing the challenge of detecting cracks in the system or predicting where they occur. He cited constant development cities need to keep up with; Austin has annexed areas where stormwater systems were previously not under its control. He also mentioned factors like the surrounding geology, the earth and the condition of the pipe itself.

“There’s no easy answer,” he said. “But we need a better understanding of resilience, especially under large storms.”

Photojournalist Ben Friberg, Director of Investigations & Innovation Josh Hinkle, Photojournalist Chris Nelson, Digital Director Kate Winkle and Graphic Artist Jeffrey Wright contributed to this report.