A sump-riser performing as a collection sump, as a riser for the corresponding tank and as a means for secondary containment for the tank's submersible pump, manway, and fittings. The sump-riser comprises a generally cylindrical sump base with an upright annular lip extending upwardly from an upper support surface; an extension riser including a lower annular riser lip which fits over and round the lip of the sump base; a cover for the extension riser; and an access or observation lid. The riser extension is detachable or removable from the sump base and may be inverted and inserted into the sump base for compact shipping. Score lines may be provided on the riser extension to serve as cutting guides for proper sizing and the sump base may be multi-sided to provide flat walls for accurate hole drilling for pipe and conduit entry.