The following is the lone reference to catch basins within the within the NPC:

2.2.6.2. (1)  Cast iron frames and covers used with manholes shall conform to CSA B70.1 (Frames and Covers for Maintenance Holes and Catch Basins)

Catch Basin Location and Layout

Catch basins are strategically placed to capture excess water and move it into a wastewater system or other underground system. While many residential properties do not require catch basins, the mandate for those that do will have come from either the architect during the drafting process, the AHJ through the plan approval process, or the general contractor in recognition of specific site conditions that require them. The need for a catch basin “after the fact” should be avoided at all costs because it is much more difficult to install remedial equipment after the site has been landscaped.

Here are some points to consider in determining where a catch basin may be needed, and points to help in its installation.

Pick the Location

If it’s already clear where the drain needs to be, start by planning the material and height that will be needed for optimal water handling and capture. If necessary, it’s helpful to wait until a heavy rain to observe where water and debris tend to flow and gather, provided possible damage from flooding during the process doesn’t occur. Having a slight slope of at least 1% (approx. [latex]\dfrac{1}{8}[/latex]″/ft) toward that area will be ideal for directing water there.

Install the Catch Basin

A hole slightly deeper and larger than the catch basin itself should be dug. This will allow the placement, compaction and leveling of bedding material under the basin. This is especially important if there is to be any vehicular traffic on top of it. Make sure the construction of the catch basin will support those potential loads. The catch basin can be bedded and backfilled enough to allow the attachment of the piping without dislodging the basin.

Create the Trenches

Trenches should be wide enough to contain the pipes, with about 3 inches of clearance on either side for working room and bedding. Make sure to grade the trenches to a minimum of 1% (approx. [latex]\dfrac{1}{8}[/latex]″/ft) or to the grades specified in the plans. Trenches should start at the catch basin and be dug straight towards the junction of other drainage pipes or its destination. Any changes in direction should be accomplished by using manufactured fittings. If not using sand or other fine bedding material, make sure there are no large rocks or boulders left in the trench that may damage the pipe. If the ground is made of aggregate that allows good drainage through it, it is sometimes a good idea to line the trench bottom with drain rock and use perforated sewer pipe which creates a “French drain”; if not wishing to let any water seep out into the surrounding soil, sewer pipe with tight joints should be used and the trench bottom should be compacted.

Lay the Pipe

Now it’s time to lay the pipes in the trench. Start by connecting the first pipe to the catch basin, bedding and backfilling it just enough so that the pipe doesn’t shift when the next section downstream is attached to it. “Flow-through” type catch basins have an inlet and an outlet so they can be installed inline on a run of pipe. This only works if the top of the catch basin grate is exactly at the desired elevation; if it isn’t, subsequent downstream catch basins are installed and connected to the piping through a wye fitting.

Testing and Back-Fill

Using water from a hose, test out the system. Get a good flow of water going through the most upstream catch basin and look for leaks or problem areas that should be fixed before the back-filling process. Make sure the flow into the catch basin is smooth. Once satisfied there are no issues, back-fill the trenches and holes with sand, gravel or whatever material has been specified. If inspection is required, it should be done at this step. Once tested and inspected, the backfilling can be completed and the final grade can be met.

Now complete Self-Test 2 and check your answers.

Self-Test 2