What are the large cylinders for on top of the first hill north of Mira Mesa along the I-15?

Dear Matt A.:

There are these large cylinders on top of the first hill north of Mira Mesa along the I-15. I think that the same type of twin cylinders exist (because I've climbed up them) in Mission Trails Park on one high peak. There was air rushing in (I think) through a metal grate. Do these go straight to hell, or do we have some sort of underground shelter, tunnels, sewers, or what?

-- Gary, Linda Vista

We deployed a unit of elves along the 15, and they reported back with a sighting of three large silos sitting on Miramar Hill, west of the f'way, near the Mercy Road exit. Easy to see when you're stuck in the backup along 15 northbound. When we assembled back at base camp, we compared notes with our Mission Trails unit and determined that what we have here are air vents. They don't go straight to hell, they connect to water pipes in the second San Diego Aqueduct, which passes through both Mira Mesa and Mission Trails. Nobody was glad you climbed the tubes at Mission Trails, but everybody was glad at least that you heard rushing air. That's what you're supposed to hear.

The aqueduct runs roughly from Lake Skinner to Lower Otay and is basically a gravity system with siphon-like sections where the terrain requires it. At high spots on the route, the vents prevent vapor locks and keep the water moving without interruption. The County Water Authority asked me to tell you that the vents are inspected periodically by the health department and are designed so no gross stuff can fall into the pipes.