Solutions For A 100-Year Problem

The City of Dallas created the Able Pump Station to remedy this issue of its past

By Sophia Acevedo

Aging infrastructure continues to be a significant topic that states across the United States need to address. In the state of Texas, which has unique geography and significant populations along the coast and urban areas, flooding is an important topic of concern because it can threaten the lives of residents or cause significant losses in property. According to the ASCE 2017 Report Card for Texas Infrastructure, flood control received a “D.”

However, the city of Dallas, Texas has worked to permanently solve this very problem that has plagued their city through the LEED Silver certified Able Pump Station, which is why it has won American Infrastructure’s Stormwater Project of the Year.

 Just one of the new pumps equal the capacity of the two original stations, so this doubles the pumping capacity for Able Pump Station,” Sarah Standifer, assistant director of Stormwater Operations

 Since its beginnings, the City of Dallas has tried to come up with several solutions to address flooding. After a significant flood in 1908, citizens made the Kessler Plan, a citywide masterplan which recommended 22 miles of levees to control floods. Known as the Dallas Floodway, this project was constructed in the 1920s and 1930s, moving stormwater away from populated residential and business areas and into the Dallas levee system. However, the solution was not exactly perfect; the levee system cut off stormwater that flowed from the downtown areas into the Trinity river which forced the City of Dallas to come up with ways to drain the area that was behind the levee. 

In the 1950s, the City of Dallas made the Able sump complex, which served the city for more than 50 years until the U.S. The Army Corps of Engineers examined it in 2003 and found that it would no longer be a sufficient solution to protect the city in cases of severe storms or significant rainfall.

Again the city went back to the drawing board and came back with The Trinity River Corridor Project, which included the Able Pump Station No. 3, to fix the dilemma of its past. For the project, the City of Dallas hired engineers from HDR and Campos Engineering, with Lance Ferland of HDR serving as the team leader of the project.

Going Abroad for Solutions and Reviewing Ideas

While coming up with the design for the pump station, City of Dallas engineers went overseas to Europe to examine concrete volute pumps which at the time, hadn’t been used in the U.S. They found that the pumps did not show wear and tear and would be ideal for the pump station.

Previously to the Able Pump Station two pump stations had been created in 1932 and 1954, however, the new project would be a vast improvement from the previous stations, according to Sarah Standifer, assistant director of Stormwater Operations.

“Just one of the new pumps equals the capacity of the two original stations, so this doubles the pumping capacity for Able Pump Station,” Standifer said.

In addition to traveling for inspiration, the engineering team also designed a scaled physical model of the pond in front of the pump station. In doing so they could analyze sump and intake changes and improve inlet flow and pump performance. According to Public Affairs Officer Nichelle Sullivan, this allowed the team to develop additional features such as straightening vanes behind the trash racks, rounded sump sidewalls and floor fillets under pump suction entrances.

The team also made another model that simulates pump discharge into the Trinity River and found that another air vent was needed in order to release pipe air when the river was above 388.5 feet deep, said Sullivan.

Overcoming Hurdles

Due to the size of the pumps, the team didn’t test the water volume until pumps were installed. Furthermore, field testing also proved to be a challenge as they could only test for discharge flow when it rained; the team had to simulate back pressure on the pumps without valves.

According to Sullivan, the team came up with solutions to these challenges, manipulated the pond’s water by holding it back, recirculating flow, adding a rise pipe and orifice plate so that it would cause back-pressure on the pump, and installing manholes that would have pip access hatches. This would essentially allow for flow and pressure measurement instrumentation, which solved the dilemmas they couldn’t test for.

Lastly, one of the other great hurdles the team had to overcome was dealing with soft, sandy soil and loose clay in the Trinity River flood plain. To address this, the team removed soft soil that was above the shale and replaced it with cement-treated crushed concrete. They also had to do deep soil mixing and build a groundwater management system to protect the foundation, while also making discharge pipes to rise and lower depending on the elevation of the embankment.

The Final Result

Finally in April 2019, the Able Pump Station was completed, set to provide the City of Dallas with 100 years of flood protection to 3 square miles of the city. Upon completion, the Dallas’ flood management team has found the pump station to be striking as they can see the water being whisked away before their eyes.

“It’s almost like dropping a straw into a malt jar and you suck it up…You can see it go down,” said Rick McRay, senior program manager, Dallas Water Utilities in a press release. “That’s how much difference there is.

Due to the success of the Able Pump Water Station, the Corps has planned to build three more pump stations of similar design. With the ability of churning out the volume of an Olympic-size swimming pool every 45 seconds, it should be of no surprise.

Overall, the Able Pump Water Station has served as a valuable piece of new infrastructure for the City of Dallas, and very deserving as the Stormwater Project of the Year.

Sophia Acevedo is the assistant editor at American Infrastructure Magazine. She can be reached at sophia@builder.media.