Watershed Vortex

Construction by the I-10 freeway overpasses in West LA. The city is building what looks like large rainwater cisterns at a lot of the freeway overpasses in West LA. Are they for rainwater capture and storage? That could be useful for watering the surrounding freeway buffer landscape. Although, I bet that rainwater draining from the freeway is fairly nasty. Maybe they are part of the City of Los Angeles Storm Water Program. Perhaps they are structures to hold in line netting systems or Continuous Deflection Separator (vortex?)