With the sewer and water component largely wrapped up and the trench backfilled, the crew has moved onto the storm water connection. This is the element of the project that has been so difficult to manage, primarily because the shallowness of the city main. Imagine a concrete storm sewer below the road, and it is filled by surface water from gravity drainage. Now, with a City requirement to actually store the rainwater on your property, you would naturally want to stick a big manhole into the ground, and connect it to the main. This requires some slope, and some depth. Both of which we don't have here.
The storm water main is about the depth of a shovel from the road surface. This is causing a lot of storage issues upstream.
The 12 inch plastic pipe is the connection to the City storm main. Coring through this really old hardened concrete was exceptionally difficult. The outside diameter of the pipe is very large and the bit needed to cut concrete is undoubtedly very costly. I never saw it done or would have taken a photo.
The truck with the concrete vessels arrives on site. Now we see the implication of the shallow City connection. We have to also use really shallow and short manholes. In order to gravity drain, the bottom of our storage has to be higher than the storm main, plus some slope for the pipe.
Everything on the truck is used for storing rain water from the building so that it does not overload the City infrastructure with water in a flood event. The idea is the water backs up into the concrete vessels and pipes connecting them, and even into the landscaped areas and slowly trickles out.
The problem with this idea, of storing water on site so it slowly releases downstream (eventually into the Bow River), is the cost benefit analysis hasn't been done. The cost of these tiny installs on each project is inefficient, due to the custom nature, engineering requirement for the design, the City fees for reviews and change, the inspections, etc. It doesnt make any sense to do it this way because the volume of actual storage created per cubic meter is so low vs the cost per cubic meter of installing it. Of course the City doesnt care about these issues because it has no concern for the well-being of small business owners like home builders. Every time the City changes the rules on these DSSP installs, it increases storage requirement and decreases outlet flow rate. Eventually the install becomes impossible, or so onerous, when combined with unworkable elements like shallow mains, that the cost will be enough to wipe out the project economics. Again, the City doesn't know or care about these realities. When the City does projects of its own, it has no budget constraints for DSSP, and it will just pay whatever it takes to solve a compliance challenge. Builders tend to have a lot less budget for compliance matters that customers don't appreciate than the City departments.