The city of El Paso, Texas, lies on the tip of the Chihuahuan desert. It is not uncommon for a year’s worth of rain to occur in a matter of days during the summer. These rain events have caused serious damage throughout the city for years, and the flooding has always been particularly bad in the Chihuahuita historic district. A new storm water pumping station with Xylem’s Flygt pumps has helped solve this problem.
In 2006, after a 100-year flood, El Paso formed a storm water utility to address the flooding issues. It hired an engineering firm, CEA Group, to conduct a drainage study with the goal to reduce the impact of these storm events.
CEA Group determined that the flooding in El Paso was directly linked to high water levels in the Rio Grande River during heavy rains. Storm sewer inlets that were added in the past in an attempt to drain the area were connected to a system that drained a watershed at a higher elevation. This caused the runoff from upstream storms to create a backup in the drainage system, flooding the Chihuahuita neighborhood.
Limited space for storm water pumping station
A new pump station was determined to be the best solution to control the river water level and subsequently prevent the flooding. However, the solution would be difficult because the neighborhood did not have the footprint or the funding for a conventional storm water pumping station.
The storm water utility required the pump station to function both while the river is low (or at normal level) and also while the river is at the flood stage. The design would need to be able to overcome these restrictions by utilizing a siphon when the river is low and the full pump horsepower while the river is at its normal level.
In 2012, a representative from Flygt distributor James, Cooke and Hobson, Inc. (JCH), contacted Flygt for assistance. With input from CEA Group, JCH and Flygt engineers, a pump station design was developed that could function properly even when the space requirements were less than the recommended Hydraulic Institute Standards for high volume pump stations.
Constant pumping regardless of the river level
The project required the design of a pump station that would be able to efficiently transport the storm water and utilize the smallest footprint possible. The Flygt axial flow propeller pumps PL7061 were selected due to their high efficiency and low power consumption. The design also utilized Flygt Formed Suction Intake (FSI) devices to ensure optimal pump inlet hydraulic conditions. In addition, this configuration allowed a more constant pumping condition regardless of the river level.
The Flygt FSI is an inlet device that provides optimal inflow to the axial flow propeller pump by gradually accelerating and redirecting the flow toward the pump inlet. Its primary function is to condition the incoming flow into a uniform profile and redirect it. By providing a reliable pump intake in limited space, the Flygt FSI is able to achieve a more economical pump station solution with a smaller footprint and better hydraulic performance than with standard inlet devices.
Able to handle 100-year storm events
With a pumping capacity of 27,000 gallons per minute (GPM), the station can handle 100-year storm events. By utilizing siphoning methods, the city was able to accommodate the large swing in river elevations, allowing the station to operate at both high and low river levels.
The pump station project included storm drain improvements and the relocation of numerous existing water and sewer lines serving the downtown area.
In 2012, torrential rains hit the Chihuahuita historic district of El Paso, and this time the results were different. With the new storm water pumping station in place and functioning well, flooding was not an issue, bringing much-needed relief to this historic area.