It’s the most wonderful(ly dangerous) time of the year

It’s the most wonderful(ly dangerous) time of the year

I’ve never been one of those people that gets amped up for Christmas before December 1st, getting the tree and decorations up, listening to the Christmas Carols-only radio stations, and putting the Christmas fire log channel on in the background while I do housework. Christmas was always a stressful time around our house as kids; our parents would always host extended families sometime during the holidays, leading to increased workloads for them as they prepared for the yearly event. This meant their child-slaves were also worked extra hard to ensure the house looked as perfect as possible for the event. I feel this yearly ritual helped me to empathize with people that have a difficult time dealing with stress, but the extra tension in our household leading up to Christmas was always something I dreaded.

Beyond that though, November in Edmonton generally has huge weather fluctuations – some days it’s above zero degrees and some it’s below, making it a very slow transition from fall to winter that results in closets being populated by the entire wardrobe rather than only seasonal necessities. It’s bizarre having to switch between wool coats and bomber jackets almost daily, and with the temperatures always hovering right around the freezing point, precipitation can come in either rain or snow formats. Or both. For me, it’s hard to get into the Christmas spirit while the weather is still making up its mind about what season it is.

It’s the 30th of November today and the same old song is being played again this year. There is very little snow on the ground, minute-by-minute wardrobe and footwear changes occur like a Super Bowl halftime performance, and daytime and nighttime temperatures are equal and opposite. This is the time of year that those getting their news primarily from an uncle’s Facebook activity would call “a benefit of global warming”. I call it the most dangerous time of year.

With the constant freezing and thawing of precipitation as temperatures swing daily, the threat of ice building up on roads and sidewalks is a daily reminder that we are not in control of our outdoor environments. We have evolved though, no doubt through generations of slipping and falling on ice at this time of year, to the point where we have developed methods of dealing with the ice using everyday products. It takes 20 generations to see a mutation in genetics in response to environmental factors, so if my great-grandparents were the first generation sliding around in the early 1900s, maybe my great-great-great-great-great-great-great-great-great-great-great-great-great-great grandchildren will have developed better balance on ice. Until then, we’ll fight the problem by sprinkling particulate over top to try and melt the ice.

In Edmonton, the three main products used for this attack are salt, gravel and sand. Each have their own benefits – all three are readily available, very cheap, and reasonably effective at returning the roads and sidewalks to clean, safe conditions. When looked at in isolation, scattering any of these products is a simple way to deal with ice buildup. The issue with these products is their lifecycle once they’ve completed their task – where does all the particulate go?

The short answer is into the soils, rivers and bodies of water, by way of the sewer system and ground absorption. This article details the impacts of salting roadways on the entire water system, including damage to pipes and seasonal increases in salt levels found in drinking water. Gravel and sand are alternatives being used that have fewer environmental risks, however their effectiveness in melting the ice is far less than that of the salt.

Doing the math shows us that there are two key issues: keeping the roads/sidewalks clear of snow and ice, and the environmental impacts of the substances used to solve the first issue. Is there a design solution that can solve both problems?

What I see standing in the way is standard practice for the design and construction of roadways. For those binge-reading this blog, you’ll remember from a previous post that sidewalks are used to convey major drainage – because sidewalks are hard and mostly linear, they are efficient at moving water. But the unintended consequence of the sidewalks’ secondary task is that water can also build up and freeze, causing this type of look:


What’s happening here is straightforward. Water (snow melting) is being directed towards the sidewalk from both sides. From there, the sidewalk does the rest and takes the water to catch basins – the entry point to the sewer systems, at either end.


The top image is a cross section of the system, with the slopes being exaggerated. The second image shows a top-down look at the overall system. Catch basins are easy to spot, and are found on an awfully lot of street corners:


See if you can spot it.

Their location makes sense when using the sidewalks as a waterway, but we’ve already seen what can happen when ice or debris builds up in these areas.

But if the water doesn’t flow quickly enough and freezes before it gets to this point, or if there’s a slope issue with the sidewalk, of course you get this:


Not exactly a pedestrian paradise.

But what if we didn’t use the sidewalks as the drainage canals? If you separated the two functions of the sidewalk, could that solve the problem?


The sidewalk is now crowned in the centre – a term I love in this circumstance because I love double entendres and the sidewalk is both crowned the undisputed winner of this alternative and is also crowned in shape. Swales on either sides of the sidewalk collect water from both sides, and can be a snow dump in the winter. The boulevard can even extend the swale to collect runoff from the street in certain places. The top image shows drainage now filtering through the swales into catch basins – larger in number but smaller in size compared to the original, located away from the pedestrian walkway. Water that lands on the sidewalk now has a shorter distance to travel into the swales than the length of the sidewalk as before, so there is a smaller likelihood of water pooling, and freezing, on the sidewalk.

This all sounds great, but you can see both the positives and negatives of this system. The positives are that the sidewalk clears itself a lot easier, reducing the need for and amount of salt/sand/gravel on the sidewalk. The sidewalks are also more usable year round, and as mentioned the swales can act as additional snow storage areas. The vegetation also acts as a filter for the water before going into the sewer system, and in large storm events the slowing of the water from entering the sewer system all at once can really benefit the rate at which the storm system reacts to and recovers from these events.

The downsides are that this doubles the infrastructure, and even if you can argue that having two smaller catch basins is the equivalent of one larger one, construction costs to build this would be increased and require a certain level of expertise (in addition to the increased complexity of the sidewalk construction). On top of that, plants ain’t super cheap and the swale would have to be specially designed with sediment controls to keep as much of the salt/sand/gravel out of the catch basins as possible. Maintenance costs will also increase as a higher expertise is required, for both hard and soft elements.

But another way to frame the issue is that it boils down to deciding whether to prioritize people or efficiency (costs). A tale as old as time for the tall foreheads in charge. Costs are a very real thing that cities must manage, as I’ve yet to meet a single person that enjoys increases to their taxes and service fees; but when your pedestrian infrastructure is unusable for large parts of the year, is it really serving its two important purposes?


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