BCAB #1093 - Concrete and Steel Storm Drain

August 29, 1989

BCAB #1093

Re: Concrete and Steel Storm Drain

With reference to your letter of August 8, 1989 regarding acceptance of a drain trench.

The drain in question is beneath a building, and consists generally of a 20 inch diameter pipe falling under, and presumably complying with the B.C. Plumbing Code. It is proposed that for a certain length, a 12 inch by 30 inch rectangular concrete trench with a steel plate cover be substituted.

While the rectangular section may in theory carry the same volume of water as the circular pipe, objections have been raised by the municipality. In addition to points made in the submissions, we have serious concerns on other aspects. In lieu of a complete pipe you propose a two part section, and while the concrete portion may well be adequate, there is the matter of the upper steel plate. The trench must effectively operate as a pipe, which makes the steel plate a part of the pipe; as steel pipe is not permitted underground inside a building, this rules out that material. The sealed joint between the steel plate and the concrete would also be unacceptable. Quite apart from the materials, we have doubts over the transition from a circular pipe to a rectangular trench; neither the behaviour of a full flow of water making this transition, or the actual mechanical details of the transition appear to have been addressed in your submission.

Taking into account all circumstances we are unable to agree with your request, and must support the objections of the municipality.

J.C. Currie, Chair