Rendering: the current Fletcher Hills 2 Pump Station is located between the Aldwych Reservoir Tanks. The new station will be built west (left) of the tanks, as shown.
Ever wonder what a pump station is for and why we need them? Check out the new pump station project Helix will be constructing over the next year! This station will serve the Fletcher Hills area and provide enhanced reliability. Last spring, the District met with residents in the immediate area surrounding the new station site to discuss the project during the initial phases of design. Now that the project design is complete and the construction contract has been awarded, a follow-up meeting has been scheduled for 9:30 a.m. on Monday, October 24 at the Aldwych Reservoir Tanks.
Pump Stations 101
The new station, called the Fletcher Hills 2 Pump Station, is one of 25 pump stations within Helix’s water distribution system. They play a critical role: filling reservoirs and pressurizing water mains.
Helix’s 25 Pump Stations
Many of you reading this are probably familiar with the basic concept of water distribution, which is to pump water to reservoirs on hilltops, and let gravity distribute the water to homes, schools and businesses. This is the most energy efficient way to operate a public water system.
A public water system, like Helix, strives to maintain water pressure at an adequate level for every customer. Water pressure is the force exerted per square inch (psi) of wall – whether in a reservoir, a water main or the pipes in your home. If water pressure is too high, pipes burst. If it’s too low, firefighters can’t put out the fire, and you can’t take a morning shower, do laundry and irrigate at the same time.
The catch is that water pressure is directly related to elevation, or more specifically, the height of a water column. One foot of water height is approximately equal to 0.434 psi. So, if we provide 50 psi to customers near the top of Mt. Helix at an elevation of 1,300 feet, the water pressure for customers at a low elevation, for example, the western edge of Lemon Grove, elevation 270 feet, will be 497 psi.
(1,300 – 270) x 0.434 = 447 psi
50 psi + 447 psi = 497 psi
The solution to this issue is to serve water to customers at different elevations, such as Mt. Helix and at the western edge of Lemon Grove, from different reservoirs. In fact, we group customers over the 50 square miles based on their elevation and we serve into 33 pressure zones. The zones are isolated from each other with specialized valves and each zone has its own reservoirs and pump stations. Check the map to see which zone you are in.
Map: Ctrl-click then click “open image in a new tab” to see a larger map.
Fletcher Hills 2 Pump Station
The Fletcher Hills 2 Pump Station pumps water from the Aldwych Tanks (that serve the Aldwych pressure zone) into the Fletcher Hills Combined Tank that serves the Fletcher Hills pressure zone.
Photo: Helix stores water in the saucer shaped section of the Fletcher Hills Combined Tank.
Diagram: note the elevation gain from the Aldwych Tanks to the Fletcher Hills Combined Tank.
The Fletcher Hills Combined Tank is actually two tanks in one — Padre Dam Municipal Water District operates the lower, cylindrical section and Helix utilizes the higher elevation, saucer section. The saucer is at a higher elevation than Helix’s old tank, which was demolished to make way for the 125 freeway, and provides higher water pressure for customers in the Fletcher Hills pressure zone.
The Fletcher Hills 2 Pump Station now must pump to a higher elevation than it was originally designed to handle, requiring both of the station’s 50 horsepower pumps to operate simultaneously. Neither pump can be taken offline for maintenance. The industry term for this is lack of redundancy, and Helix requires redundancy in all facility designs to ensure a reliable water supply. Even our water treatment plant has two of everything.
The new pump station includes three pumps that are capable of pumping 2,000 gallons per minute more efficiently than their predecessors. The third pump is a standby unit, allowing maintenance of the other two. The state of the art design also includes automated control valves, flow metering, electrical switchgear and instrumentation coordinated with the district’s SCADA control network.
Rendering of new pump station
Current pump station
Helix maintains and replaces our pump stations as needed, and nearly all of our older stations have been improved at some point to ensure reliable service. The average age of our pump stations is 33 years old. If you want more information about the Fletcher Hills 2 Pump Station, please feel free to contact Helix Water District’s Engineering Department or click on the following link.