| 摘要 |
An underground storage tank has an inner wall and an outer wall defining a generally annular space for receiving a leak detecting fluid, and a plurality of ribs bonded to the inner and outer walls and projecting radially outwardly from the inner wall, each rib comprising sidewalls and a top wall, the outer wall being attached to the top wall of each rib but substantially unattached to the sidewalls of each rib, and the outer wall substantially conforming to the contour of the inner wall and the ribs.
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