A pumping station equipped with axial-flow submersible pumps in Pasadena, Texas, USA, prevents flooding from blocking hurricane evacuation routes near Gulf Coast.
Pumps solve decades-old stormwater problem in Texas
City officials of Pasadena, Texas, and the Texas Department of Transportation turned to Grundfos and its line of axial-flow submersible pumps to solve a flooding issue that had plagued the city for years.
Located 26 kilometers southeast of Houston, Pasadena is the second-largest city in Harris County and home to 150,000 residents. Its proximity to the Gulf of Mexico means the city receives nearly 1.4 meters (55 inches) of rain each year, 43 centimeters (17 inches) above the state median. Combined with Pasadena’s relatively flat topography and poor drainage systems, heavy rainfall can cause flooding and block major highways.
During significant rainstorms, the city receives several times the flow during dry weather, quickly overwhelming pumping stations. Most alarmingly, ample flow can cause blockage that affects hurricane evacuation routes. Because of this, the city’s main priority during major storms is to keep the routes clear and passable.
Beltway 8 is one of the few main highways used to evacuate residents from the south and southwest during a hurricane. For decades, surface water flooding has impeded motorists at the Spencer Road crossing, and the designated evacuation route was left impassable on several occasions.
In cooperation with the Texas Department of Transportation, the city of Pasadena determined that the cause of the flooding was insufficient capacity. The storm drain systems are installed with flap gates positioned at or near drain outlets to prevent the drainage system from back flooding during major storms.
In the case of Beltway 8, the road’s 1.37-meter (54-inch) storm sewer lacked proper capacity, so a flap gate valve would prevent additional water from flowing back on the road. However, that same safety valve would also limit flow into the drain, causing frequent flooding to the roadway that would result in lane closures and extended traffic delays.
Pasadena had two options to solve the dilemma. It could either create a large detention basin or it could increase the capacity of the storm system. Both of these options required several million dollars, as well as the allocation of real estate and years of construction.
Assistant Director of Public Works for Pasadena, Mark Gardemal explains the project challenges, “The particular application of this storm water pump system was unique in that it was placed in between the Texas Department of Transportation feeder roads and the Harris County Toll Road Authority main lanes in a footprint that most engineers would consider daunting. We had about 25 feet (7.62 m) to work with and we were going to have to do all our pumping arranges, all our piping arrangements below ground.”
The project engineers reconsidered their initial two options because of space restrictions. Instead, they decided to route excess storm water around the existing sewer and push it far enough downstream to create adequate capacity.
“We recommended the Grundfos submersible pumps along with the CU362 and the variable frequency drive,” Cory Marcotte, engineering sales professional at distributor Pumps of Houston, says. “It allows us to maintain high efficiencies during operation, and to also monitor and adjust the speed of the pump depending on how much rainfall we get at a particular time. The Grundfos line of axial-flow submersible pumps is capable of pumping up to 568 cubic meters (m3) (150,000 gallons) per minute and features a compact design, as well as construction cost savings of up to 50 percent.”
The Grundfos storm water pumping station offered project planners a compact, energy-efficient and cost-saving solution, which for the City of Pasadena, saved significant operation and maintenance costs when compared to similar options. “This particular station, in terms of its capability, its design, its execution, and its operation cost about half of what similar pump stations would cost to run and maintain,” Gardemal says.
Since the city installed the pumps in 2012, the area experienced a major storm that generated six inches of rain. Amid fears of flooding, the new pumping station efficiently moved more than 114 m3 (30,000 gallons) of flood water per minute for roughly five hours—keeping the highway clear and safe.