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Flooding concerns prevent BoA from approving increased impervious cover

Friday, June 14, 2019 by Jessi Devenyns

When it comes to drainage controls, how much of a good thing is too much? The answer is, when drainage control threatens to heighten flood risk due to the increase in impervious cover required for its installation.

Jason Asbury came on behalf of Homex Partners to the Board of Adjustment’s June 10 meeting to ask for a variance at 1128 and 1130 Lott Ave. to increase impervious cover entitlements from the code-required 45 percent to 50 percent. The board voted 9-1 to deny the request for a variance, with Board Member Jessica Cohen voting in opposition.

Asbury explained to the board that the variance request was a product of bad calculations made by the previous project engineer. “I got involved when all four lots had been formed … that’s when I asked the client what is happening here,” he said.

What happened was that the two lots are flag lots and had been divided to allow for four homes to be constructed on the premises. However, due to the topography of the property, there is a 54-foot vertical change in a 300-foot span, which necessitates some drainage engineering to route water down the slope and away from the homes. Instead of installing drainage ponds, the previous engineer opted for retaining walls.

Those retaining walls, according to Asbury, were designed with bad calculations. When he picked up the project, he told the board, “I did my calculations and I found there was a problem.” The calculation error of about 5 percent only existed on lots C and D of the two flag lots.

Asbury explained that a variance to increase impervious cover would compensate for the incorrect calculations as well as offer an aesthetically pleasing solution for the future homeowners. “I’m using driveways with curbs next to houses to protect houses from water,” he said.

He acknowledged that there was an option to design within the code-allowed 45 percent impervious cover limitation but it would not be as nice a design. In order to come within compliance, the carport would be removed and retaining walls would need to be installed in lieu of the curbs along the driveway.

Neighbor Joel Nolan came to speak against the proposed variance, saying that even a 5 percent increase in impervious cover limits could have a catastrophic impact on a street where flooding is already an issue. While the 5 percent increase would translate to 900 square feet on the two flag lots in question, Nolan pointed out that several hundred square feet here and there adds up. “This new impervious cover (limit) totals 14,000 square feet. … That’s what we would be adding if we gave everyone the 5 percent over.”

Several board members expressed hesitation at judging the efficacy of the drainage solution that Asbury had designed.

“I’m not the right person to judge aesthetics nor am I a drainage engineer,” said Board Member Rahm McDaniel, adding, “I don’t know who on this board is.”

Board Member Michael Von Ohlen, who owned a construction business for three decades, noted that a retention pond would have been another solution that does not require an increase in impervious cover. “I find it very hard to understand why those two areas (backyards) were not used as a retention pond or this site does not have a retention pond on it,” he said.

Even with the understanding that drainage control on the property was crucial, Chair William Burkhardt noted that “your best case in this is maxed out at 45 percent, and that bothers me.” He pointed out that maxing out the impervious cover in the construction phase does not leave any wiggle room for homeowners who may want to install patios or pads for their trash bins and air conditioners.

Cohen, who voted against the motion to deny the variance, explained that she commended Asbury for attempting to divert the water and make it aesthetically pleasing. “I’m probably the only person on this board that lives in a duplex,” she said. She said that sharing a yard can make a duplex less desirable than a single-family home, so “why should it have to be ugly too?”

Board Member Melissa Hawthorne was absent.

Photo courtesy of the city of Austin.

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