Stormwater discharge to kerb - advice needed!

[DIY_guy]

Hi,

I'm working on the final stormwater plans for my 2 lot development and discharge to kerb (via detention tank) is the only suitable option available. Auckland Council perfer stormwater discharge to kerb to go through into a reticulated system, however.

Has anyone got recent experience of discharge to kerb being consented to common cesspits (that flow through to soakage only)? This would be unbelievably helpful if anyone has knowledge / experience of such discharge?

(zone 6a, Onehunga region, road frontage).

Many thanks,
Charles

[John the builder]

have you talked to a stormwater engineer?

[DIY_guy]

Yes, currently working with an engineering consultant.. we've asked council for their likelihood to accept / decline on these terms... however still awaiting their response.

I'm interested to hear of examples of where this has been allowed in the past, so I can use as a precedent.

[John the builder]

as long as ground is suitable for soakage then this should be in accord with councils desire to retain surface water on site, but sorry cant help with recent examples. Is the councils concern at kerb discharge warranted (i.e is the area under stress already)?.

[DIY_guy]

The area has a lack of infrastructure (we have already exhausted all other stormwater alternatives), with discharge to kerb the only remaining option, with a sound engineering solution. This system, however, isn't reticulated (and leads to soakage).

Using detention tanks, we can ensure that discharge remains at current (pre-development levels), thus there is zero effect on the load of the network. My question is, despite the nil effect we'll have on the network, are they likely to decline on the basis that the public network isn't reticulated?

[Bluekiwi]

Since you guys know what you are doing.

How does it work when stormwater on road, is higher ground level than proposed new site ??

Council expects you to somehow get water up to that level somehow ?
And unless you can do that, I have no idea how, then your going nowhere.

[Davo36]

You can pump it up BK, it's done all the time.

[John the builder]

if your spouting is above the kerb you can seal the sytem and syphon it

[BAB]

Hi Charles

I'm a stormwater engineer. If the soakage is an Auckland Council asset and there are other private discharges going to it then provided it has capacity you may be able to discharge to it. Typically you are not allow to discharge to cesspits however. You need to make a separate connection. If it's a cesspit leading to soakage with no other private discharges it will be an AT asset and you probably won't be allowed to discharge to it.

As a rule council does not allow pumping stormwater but it does happen occasionally. Their default position will be "no" but you might be able to win them over with a good argument.

[Grundy]

Onehunga even up to a few years ago I was told is blessed with some large natural water aquifers fed by the large areas of very porous volcanic rock and soil. Many old timers used to just have house SW discharge straight into the gardens and the storwater would dissapear faster than it got across boundaries. That said I know a developer a couple of years back got permission to install some quite deep concrete manholes (sumps) with porous concrete bases sat on scoria. The manholes easily took any flood intake several times over and slowly drained away over the course of many hours. Trouble I predict will be finding a council engineer with local geotech knowledge under the new super (hah) city. Good luck.

[John the builder]

it isnt hard most drilling companys will do investigation that involves drilling a test hole to evaluate soakage rate $1200 ?? and that is accepted by council if the nubers stack up

[Wayne]

That said I know a developer a couple of years back got permission to install some quite deep concrete manholes (sumps) with porous concrete bases sat on scoria. The manholes easily took any flood intake several times over and slowly drained away over the course of many hours. Trouble I predict will be finding a council engineer with local geotech knowledge under the new super (hah) city. Good luck.

You mean a soak pit?
Quite standard stuff really

[Grundy]

You mean a soak pit?
Quite standard stuff really

To the layman - yes
But a soakpit usually has porous sides as well as base and can even incompass those useless 'rain gardens' that no one bothers cleaning out every decade. The concept of ongoing maintenance is easily forgotten.
It was explained to me that a manhole with a porous base can be manufactured to regulate the discharge and does not greatly impact on the sorrounding water table that field, french type drains or soakpits generally do. In other words its primary function is building or hard surface stormwater collection, not general ground drainage.
Its all academic anyway as in parts of Onehunga the water disappears so fast it makes for lovely spring water for the local factories to use.