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Environmental Board recommends new rules for underground structures

Monday, August 17, 2009 by Charles Boisseau

Most people know if you start digging you might hit water.

 

The City of Austin is now finding that it may need to adopt new rules and procedures as dense developments disturb groundwater in its urban core.

 

On Aug. 5, the city’s Environmental Board heard a presentation from Tom Ennis, an engineer with the city’s Watershed Protection Department, about the challenges the city faces as more developments dig into the subsurface of the city.

 

Ennis has led a study of underground structures and groundwater with an aim of strengthening the city’s development codes and policies to avoid problems from flooding and groundwater pollution.

 

The city began the project after several cases of flooding and pollution involving underground structures in the past year:

 

  • The most highly publicized was an underground fuel oil tank leak, which sent fuel oil into the alley behind Sixth Street and eventually into Waller Creek. Later, it was discovered the leak came from a nearly 100-year-old underground storage tank originally connected to the Littlefield Building, the city’s second modern high-rise.
  • Another event was extensive flooding on Pearl Street in the West Campus area after two new large multifamily buildings with underground parking structures started discharging groundwater onto the pavement, causing rippling and potholes. Ennis said this required the city and developers to come up with an agreement to tear up the street, install a pipeline to discharge the water to a storm sewer and repave the street.
  • Ennis said yet another underground problem was the discovery of a release of perchloethylene, a chemical used in dry cleaning, which leaked from a private sewer main in Block 21 downtown. To clean up the mess, a large carbon filtration system was installed to treat 18,000 gallons of groundwater a day.  
  • Finally, a parking garage being built by the United Methodist Church in Tarrytown sprung an underground leak when water began pouring into the area for a garage foundation. The city provided Tarrytown $5,000 to help pay to install underground storage tanks to capture and reuse the water.

 

Ennis said city staff is continuing its work to identify and map underground structures and contaminated sites, sites that may need special attention if developed in the future.

 

In the meantime, he recommended that the city adopt new rules to – among other things – review potential underground structures during the development approval phase, promote groundwater reuse and come up with ways to fund drainage infrastructure projects, such as charging developers impact fees or sharing costs on infrastructure improvements.

 

Already, he said, staff in the city’s One Stop Shop have been directed to review new development plans to determine whether they have underground parking or other structures that might disturb groundwater and whether they are located in an area where a groundwater contaminated site has been identified. Using information from the Texas Commission on Environmental Quality, staff has mapped hundreds of contaminated sites citywide and more than 800 locations of underground tanks, Ennis said.

 

On a motion by Chair Mary Gay Maxwell, the Environmental Board recommended that the City Council direct City Manager Marc Ott to implement Ennis’ recommendations, including coming up with new development codes to address the issues, such as requiring properties along stream corridors to recharge base flows by use French drains or other methods, encourage water reuse and investigate alternatives for funding drainage infrastructure projects.

 

The Board passed the recommendations by a 4-0 vote, with three members absent.

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