Patent ID: 7419332

Claim:
A molded plastic corrugated arch shape cross section leaching chamber, comprising: a first chamber end having a dome and an outer edge; an opposing second chamber end, shaped to overlap the dome of a like chamber and to thereby form a pivotable joint between the chambers, wherein the second end overlies the dome when chambers are joined together, the second end having a flange, the interior concavity of which fits the exterior surface of the dome, wherein the exterior surface of the dome has at least one upwardly running elongated depression, wherein a projection of the at least one upwardly running elongated depression into the vertical plane has the shape of a trapezoid, wherein the larger trapezoid base end is at a higher elevation than the opposing smaller trapezoid end and wherein the at least one upwardly running elongated depression includes a first trapezoidal depression and a second trapezoidal depression, the second trapezoidal depression having smaller dimensions than the first trapezoidal depression and being located further from the outer edge of the end of the chamber than the first trapezoidal depression.