It's a bit more complicated than that, and I can put you on to the guy who worked those calcs for Calgary, if you're interested.
The local distribution pipes are a part of the development itself, same as the roads: included in the cost of the developed buildings.
The City comes in when the pipes need to be replaced, many decades later.
But it also comes in when the city grows beyond the size of the feedermains (0.5m+ in diameter. the biggest 2m+, that cost $10/mm to put in.) overall capacity.
You can't go one more mile outward, without running out of water closer in. So then you have to enlarge or twin the major arteries to get enough water out to the new fringe. The added mile requires ten miles of feedermain to enable.
THAT can be very expensive indeed, and putting the cost onto developers would stop development. So Calgary went into debt. A long way into debt, and THAT's when Calgary, even Calgary, started to look more seriously at density. And water conservation. (Finally got meters.)
This issue can be avoided by finding new water sources further out, and building a new water treatment plant on them, basically treating the growth area as a whole new town. All of these issues can vary dramatically depending on local water availability (Calgary is a semi-arid climate with the whole river spoken for).
Thanks Roy! What would a typical feedermain expansion project look like? I'm thinking that replacing an existing feedermain with a higher-capacity pipe must be hugely disruptive, given the number of households that the feedermain serves. Would twinning be more common?
Should add that Sewer trunks DO get twinned - because you can't just put them anywhere. There's some universal law about them having to be downhill from the sewage, apparently. So the existing trunk may be in the only place (along a valley bottom) that's the only place you CAN go.
And, with sewer, OMG yes, you do twin, not upsize. Because the sewage NEVER STOPS COMING and you'd have to pump around your job, which is the least-fun pumping that one can do.
Neither. What's the most-common is to put in another water main somewhere else, miles away, and route the water from there. Basically, you move the flow somewhere else.
The trick is to pre-plan these "second generation" feedermains a whole generation ahead - you put in roads with a median, or wide shoulders, which are then free for construction without blocking the whole road.
I have the perfect example for you: the two-decade debate on when and where to put in an expansion to serve north Calgary better. It was delayed, and moved from one route (through Nose Hill park, not disruptive, but still quite unpopular, parks are sacred) to one that circled way around on roads large enough to not be a neighbourhood disruption - except where there are a few. It'll be done by 2029, supposedly.
It should have been done two years ago - and if it had, nobody would have heard much about the Giant Main Break last year, because supply would have had lots of backup, no water restrictions.
I'll dig you up a map of both proposals, and the larger problem of serving the growing north end.
It's a bit more complicated than that, and I can put you on to the guy who worked those calcs for Calgary, if you're interested.
The local distribution pipes are a part of the development itself, same as the roads: included in the cost of the developed buildings.
The City comes in when the pipes need to be replaced, many decades later.
But it also comes in when the city grows beyond the size of the feedermains (0.5m+ in diameter. the biggest 2m+, that cost $10/mm to put in.) overall capacity.
You can't go one more mile outward, without running out of water closer in. So then you have to enlarge or twin the major arteries to get enough water out to the new fringe. The added mile requires ten miles of feedermain to enable.
THAT can be very expensive indeed, and putting the cost onto developers would stop development. So Calgary went into debt. A long way into debt, and THAT's when Calgary, even Calgary, started to look more seriously at density. And water conservation. (Finally got meters.)
This issue can be avoided by finding new water sources further out, and building a new water treatment plant on them, basically treating the growth area as a whole new town. All of these issues can vary dramatically depending on local water availability (Calgary is a semi-arid climate with the whole river spoken for).
Thanks Roy! What would a typical feedermain expansion project look like? I'm thinking that replacing an existing feedermain with a higher-capacity pipe must be hugely disruptive, given the number of households that the feedermain serves. Would twinning be more common?
Should add that Sewer trunks DO get twinned - because you can't just put them anywhere. There's some universal law about them having to be downhill from the sewage, apparently. So the existing trunk may be in the only place (along a valley bottom) that's the only place you CAN go.
And, with sewer, OMG yes, you do twin, not upsize. Because the sewage NEVER STOPS COMING and you'd have to pump around your job, which is the least-fun pumping that one can do.
Neither. What's the most-common is to put in another water main somewhere else, miles away, and route the water from there. Basically, you move the flow somewhere else.
The trick is to pre-plan these "second generation" feedermains a whole generation ahead - you put in roads with a median, or wide shoulders, which are then free for construction without blocking the whole road.
I have the perfect example for you: the two-decade debate on when and where to put in an expansion to serve north Calgary better. It was delayed, and moved from one route (through Nose Hill park, not disruptive, but still quite unpopular, parks are sacred) to one that circled way around on roads large enough to not be a neighbourhood disruption - except where there are a few. It'll be done by 2029, supposedly.
It should have been done two years ago - and if it had, nobody would have heard much about the Giant Main Break last year, because supply would have had lots of backup, no water restrictions.
I'll dig you up a map of both proposals, and the larger problem of serving the growing north end.