The top may include {HEAD ~ a slab} of {TAIL ~ water impermeable material} having a substantially central opening through which plant material grows, as well as an inlet opening for receiving stormwater to be treated 
of
The top may include { HEAD ~ a slab } of { TAIL ~ water impermeable material } having a substantially central opening through which plant material grows , as well as an inlet opening for receiving stormwater to be treated
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH