A leaching chamber having an arch-shaped cross-section, a pair of contiguously molded, opposing end walls, and alternating peak and valley corrugations along its length, is provided interior chambers and fluid communication openings along the base on each extending side of the chamber. Formed within the chamber at locations corresponding to each peak corrugation, an inner wall is attached to an interior surface and extends substantially within the peak corrugation to the base of the chamber. An aperture is formed in both the inner wall and in the opposing outer wall of the chamber, enabling fluid communication through the interior chamber--and thus into and out from the interior of the leaching chamber itself.