storm water detention tanks

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PolicyGuy

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#3042252 26-Feb-2023 15:27

mattwnz:
Does your stormwater go into the councils system?

In Whanganui the stormwater and sewage systems are fully separated.

Since the 1980s, every metre of street in town has been dug up and new separate sewage and stormwater mains laid, replacing the old single pipe system. In the old single-pipe system, a lot of raw sewage went straight into the river: not any more. The stormwater goes into the river, the sewage now all goes to a treatment plant. There are supposed to be no interconnections at all between the two systems.

One advantage is that you can now swim in the lower reaches of the Whanganui River, whereas back in the 1970s & 1980s, swimming downstream of the Aramaho railway bridge was strongly contra-indicated. Another advantage is that the mana of the Awa is being more respectfully and sensitively addressed. A third advantage is that very little of the sewage & stormwater infrastructure is more than about forty years old, in strong contrast to most other towns & cities in NZ.

There are two major disadvantages: firstly our rates are rather high* to pay off the debts incurred in this dual-pipe upgrade; and secondly under the new Three Waters arrangements we fear that we will end up paying for less provident and less forward-seeing towns & cities to be brought up to the standard we've achieved and been paying for.

Why are their ugly above-ground rainwater tanks in Buckingham Place?
The purpose is to act as a surge absorber on the stormwater system: when it rains a lot, your house rainwater fills up the tank, then flows more gently (15mm pipe?) into the shared stormwater system. It is a requirement for all new builds.
They are above ground because: (a) this is cheaper for the developer; also (b) the water table is only about 1 - 1.5 metres below surface level in most of Springvale, so putting in an underground rainwater retention tank is both difficult and expensive {see (a)}

* My home in 2022: CV ~$400K. Rates ~$3,500 (District Council) + ~$400 (Regional), total ~$3,900 p.a. for a modest 130m2 house on a 500m2 section

tweake

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#3042261 26-Feb-2023 15:52

mattwnz:

Does your stormwater go into the councils system? In many areas this is not permitted, and people instead have to install soak pits. In my parents areas, they have a water tank underground, which then goes into a soak pit if it overflows.In the recent storms, the manhole on the watertank popped off when it filled up.
But soak pits with urban intensification is more and more difficult as it needs land. Then are the council increasing their stormwater network capacity and pipes to cope with the increase of new houses connecting to it.

???

storm water has to go somewhere. if your in town its always into a council system of some type, either piped or open drain. you have to use their system, its more of a case that your not permitted to do anything you like with it.

soakage pits are used in areas with drainable soils. here its all clay so they are not used. also soakage pits clog up over time. there is also things like drainable tarseal, but that suffers the same problem of clogging up.

mattwnz

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#3042277 26-Feb-2023 16:37

PolicyGuy:

There are two major disadvantages: firstly our rates are rather high* to pay off the debts incurred in this dual-pipe upgrade; and secondly under the new Three Waters arrangements we fear that we will end up paying for less provident and less forward-seeing towns & cities to be brought up to the standard we've achieved and been paying for.

* My home in 2022: CV ~$400K. Rates ~$3,500 (District Council) + ~$400 (Regional), total ~$3,900 p.a. for a modest 130m2 house on a 500m2 section

I don't think it is a case of other towns being less forward thinking, but more that they are trying to keep their costs at an affordable level, as ratepayers already pay more in smaller council catchments than they do in big cities like Auckland. Your rates for example look quite low relative to what we pay for a similar sized house and smaller land which is in the 4ks. Small towns rates can be the most expensive, eg Cartertons rates are very high and some of the highest in NZ, because they have a lower number of rate payers paying for infrastructure and appear to have been doing lots of water upgrades. It is a bit like roads in NZ, people in small towns don't get to use the expensive roading projects in other places on a day to day basis, but still have to pay all the roading taxes. Often roading in those areas is poor, as it is in the Warairapa where they have had to decrease limits on SH2.

So nothing is fair or perfect. But 3 waters does allow these small areas to get up to the required standard without imposing massive unsustainable costs on everyone living in them. Anyone visiting those towns will also have good water to use, and is needed for our tourism economy . We are also supposed to be trying to get less people moving to the main centres , and instead moving into other areas of NZ. But growth in those other areas is restricted when infrastructure is poor and that effects the entire country and economy. Some of the problems is Gisbornes infrastructure, esp. roading, are related to cheap band aid solutions in the past. That is the whole problem with taxation, it isn't necessarily proportional to the value you get back out of it. Some people get great value from the tax they pay, some people get terrible value, but people need to think of the country as a whole.

tweake

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#3042285 26-Feb-2023 16:58

mattwnz:

I don't think it is a case of other towns being less forward thinking, but more that they are trying to keep their costs at an affordable level,

catch22 is keeping costs low has caused issues down the track. for eg here town water supply used to be dirt cheap, water was damn near free. they never charged enough to cover repair/replacement costs. so now it needs upgrading, the whole cost is being dumped on the existing ratepayers. it doesn't help when councils raid the repair fund piggy bank for pet projects and leave an IOU.

one of the other issues is many people have fought against paying any form of taxation, including rates or water bills. ie cheap for me and screw everyone else. most of those have long since buggered off, leaving everyone else to pay the price.

also being cheap results in a lot lower quality level of supply. ie dirty water supply. of course the incident which kicked this off, infected water supplies. it makes you wonder why they bothered with a town supply in the first place, just let everyone have tank water and look after their own water quality. a lot of these small towns don't need a town supply.

Bung

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#3042303 26-Feb-2023 18:17

PolicyGuy:
In Whanganui the stormwater and sewage systems are fully separated.

There are supposed to be no interconnections at all between the two systems.

All it takes is an idiot plumber and maybe a useless drainage inspector and you too could end up with a multi-storey building with its connections reversed.

https://www.stuff.co.nz/dominion-post/news/wellington/131161030/years-of-sewage-flows-into-wellington-harbour-after-pipe-error

MikeAqua

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#3043070 28-Feb-2023 09:40

One thought (not knowing the physical situation of your section) ... you're adding 15,0000kg to the weight on the site during peak rain. Does that increase the risk of slips etc?

Mike

MadEngineer

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#3043138 28-Feb-2023 10:47

PolicyGuy:

mattwnz:
Does your stormwater go into the councils system?

In Whanganui the stormwater and sewage systems are fully separated.

Why are their ugly above-ground rainwater tanks in Buckingham Place?
The purpose is to act as a surge absorber on the stormwater system: when it rains a lot, your house rainwater fills up the tank, then flows more gently (15mm pipe?) into the shared stormwater system. It is a requirement for all new builds.
They are above ground because: (a) this is cheaper for the developer; also (b) the water table is only about 1 - 1.5 metres below surface level in most of Springvale, so putting in an underground rainwater retention tank is both difficult and expensive {see (a)}

Thanks for that detail - wasn't aware and the agent didn't let us know that either. Apparently some people do add taps to it for watering the garden which would be the first thing I'd be doing. It'd also provide us with water for the boy's fish tank. I think there was talk of it being a requirement here in Palmy too

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Bung

6477 posts

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#3053505 22-Mar-2023 22:09

Bung:
PolicyGuy:
In Whanganui the stormwater and sewage systems are fully separated.

There are supposed to be no interconnections at all between the two systems.

All it takes is an idiot plumber and maybe a useless drainage inspector and you too could end up with a multi-storey building with its connections reversed.

https://www.stuff.co.nz/dominion-post/news/wellington/131161030/years-of-sewage-flows-into-wellington-harbour-after-pipe-error

Wellington Water have backtracked on this story. The private building owner wasn't responsible for the fault, the error was found in council pipes.

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