Planting a "Containerized" Cedar Hedge

Hi gang,
I have a 28' wide structurally-sound rooftop terrace that is looking pretty bare, garden-wise. The terrace overlooks a major street in central Toronto. There is a newish 5' tall black chain-link fence running the entire 28' width that sits on top of a 3' brick "knee" wall, probably erected to keep people from falling off the roof onto the sidewalk below.
Several friends have suggested I erect a cedar hedge against the 5' fence, growing from a to-be-contructed trough-like P.T. container that would be permanently attached to the steel flashing that covers the top of the 3' brick wall.
The only problem is that I have only 12" of width for the "trough" to sit on, and would like to restrict the depth of this to 12-15" maximum.
My question is this. Is there enough soil mass in a 28 foot-long 10" wide x 12" deep container to support 9 or 10 cedar shrubs placed 30" apart?
How durable would such a container be, assuming I used pressure-treated (P.T.) wood? Would 1/2" diameter holes drilled near the bottom provide adequate drainage?
Thanks for any advice any of you may have.
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In my opinion, no. At least, not long term, without laboriously removing the trees periodically, root pruning, trimming the foliage, and replenishing the soil.

Very durable, however care would have to be given to cupping and splitting of the wood, especially near the fasteners.
Dave
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