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Powerhouse Civil

Dumping. Another slip. The gravel below the high tide line.
Dumping. Another slip. The gravel below the high tide line.

I was looking for erosion sites when I saw Powerhouse Civil actually dumping material into Tamaki Estuary here. I will let Auckland Council know tomorrow.

UPDATE: (2 Weeks later) Rowan from By-Laws called me and is referring it to a pollution dept.

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Zinc

Zinc contamination in sediment
Zinc contamination in sediment

I didn’t really get how zinc from galvanised roofs could be poisoning the estuary until I made this map. I found a presentation by Marcus Cameron which suggests that sites the source (the head of the estuary) are trending up (more zinc). At the same stormwater conference Judy Anne Ansen showed a pie chart on Industrial (Mt Wellington) zinc sources with about 80% attributed to roofs.

Marine report card for Tamaki is here:
http://stateofauckland.aucklandcouncil.govt.nz/marine-report-card/tamaki-estuary-reporting-area/

More in depth articles on the zinc problem here:
http://www.aucklandcouncil.govt.nz/EN/planspoliciesprojects/reports/technicalpublications/Pages/technicalreports2008.aspx
This one is the best SOURCE CONTROL OR TRADITIONAL BMPS? AN ASSESSMENT OF BENEFITS AND COSTS IN AUCKLAND CITY

My Questions/ Answered:

  1. How bad is zinc for the environment & what is it hurting? / 50% of organisms are expected to be affected
  2. Can we remove it without moving the mud?
  3. Is painting industrial roofs clearly the most effective fix? / Yes, tho storm water ponds can be great and they have other benefits
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My Nursery

20130303-160001.jpg

READY TO PLANT
1 Karaka Trees (grown from urban seed)

GROWING
2 Karaka Trees (grown from urban seed)
3 Locquet Trees (grown from urban seed)
10 Carex Lessoniana (bought – will divide)
8 Passionfruit plants (grown from stray seedlings)
1000 Pohutakawa seeds (grown from local seeds)

CLONING
16 Pear Trees (cloned from urban source)
6 Pohutakawa Trees (cloned from urban source)

GERMINATING
10 Puriri Trees (Wai O Taki Bay seed)
30 Cabage Trees (urban seed)
10 Nikau Trees (Maungatapere seeds)
10 xxx? Trees (Maungatapere seeds)
12 Karaka Trees (Mt Wellington seed)

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Seawall experiment

We need to extend the retaining walls in the Tamaki Estuary and I don’t want to have to lug a bunch of stone down there so I thought ‘what if we use the mud to make concrete blocks?’ It makes sense right? Use the product from the erosion problem (mud) to fix itself.

I got advice from a chemical engineer who thought ‘as long as I don’t use any rebar I should be ok with the salt water’. He also gave me a mix to try which I adapted to fit the local conditions:

  • 10% Ordinary Portland cement
  • 10% Mc Donalds fine lime
  •  80% Mud

I premixed the cement and lime so I did not have to lug the 25 kg bags on site. I bought a 45 litre bolt box to use as a mould. I put the whole thing in a plastic bag to cure as I am working below the high tide mark (concrete does not need air to cure). Things I learnt:

  • Mixing takes ages, I was very thorough but this took an hour!
  • The first block will not sit on flat ground so you need to add more cement and lime (I did not have any more so I put a large stone in the middle of this block).
  • I tried to keep the mix as dry as possible for as long as possible. One advantage of this method meant I could pull any crabs out that I accidentally scooped up.
  • Multi coloured mud helps you monitor your mix. It looks like mine had a lot of clay in it, which makes sense given the eroding banks are clay.
  • Update 2018: Mudcrete is a thing
Here is where I took most of the mud. It will be interesting to take another photo of this spot in a month or two.
Here is where I took most of the mud. It will be interesting to take another photo of this spot in a month or two.

UPDATE: 5 DAYS

Well it filled in pretty fast!
Well it filled in pretty fast!

UPDATE: 26 DAYS

Hard to believe I have taken 90 LTRs of Mud from this spot.
Hard to believe I have taken 90 LTRs of Mud from this spot.

UPDATE: 3 MONTHS

Impossible to tell I have dug here, even the layering looks the same to the un-dug areas.
Impossible to tell I have been digging here, even the layering looks the same to the un-dug areas.

 

This is the location ( you can see how well the old wall has done ).
This is the location ( you can see how well the old wall has done ).

 

This is what the mixing process looked like. I cut the bag open and taped it up later.
This is what the mixing process looked like. I cut the bag open and taped it up later.

One thing I quite like about this mix is the lime, which is a much more environmentally friendly product than cement. Tho the engineer has told me ‘If it’s not strong on compressive strength, increase the cement and reduce the lime’.

Here is the rock before I covered it. And the whole thing sealed up ready for high tide.
Here is the rock before I covered it. And the whole thing sealed up ready for high tide.

Let’s see if it turns into a rock or not. I am optimistic because of the clay but I am worried because concrete is usually made of sand. The engineer reckoned it might take a month!

UPDATE: 18HRS: Its solidifying! It feels like brand new plasticine. My 30kg son was able to stand on the block without leaving much of a dent. The bag has worked well and I am confident if it came off now the impact from the sea would be negligible.

UPDATE: 9DAYS

1 Plastic off. 2 Bad mixing (I will mix outside the box next time). 3 I had to saw the bolt box off.
1 Plastic off. 2 Bad mixing (I will mix outside the box next time). 3 I had to saw the bolt box off.

 

Ideally I would find a way of sliding up the box without having open it up. The second block is better mixed than the first one (it also took half the time). The mud did not look different, but most of it was infill from the small hole left by the last brick.
Ideally I would find a way of sliding up the box without having open it up. The second block is better mixed than the first one (it also took half the time). The mud did not look different, but most of it was infill from the small hole left by the last brick.

UPDATE: 48HRS After Mixing

Second brick removed from the mould a lot earlier, some areas a lot harder than the previous brick others still a bit soft. It will be interesting to see how it handles the ocean at this age.
Second brick removed from the mould a lot earlier, some areas a lot harder than the previous brick others still a bit soft. It will be interesting to see how it handles the ocean at this age.Parts of it look very white.

UPDATE: Third Brick

Made it even faster this time. I also dug in some footings.
Made it even faster this time. I also dug in some footings (1 brick high).

When I pushed it over it did not break up at all! Even tho the top brick was still very soft at only 5 days old. The bottom bricks are rock hard.

UPDATE: Fourth & Fifth Bock

L shape should help with wave erosion. Clay like lumps in my mix.
L shape should help with wave erosion. Clay like lumps in my mix.

This is all I need to do for the experiment but I am keen to go one or two blocks higher. I was short on time doing these last blocks so the mix was not that good, I am worried the sea will eat them away leaving me with swiss cheese bricks.

UPDATE: Icing

icing

It’s been 3 months and the blocks have held together against the sea no sweat. The swiss cheese does not look good though so I have added a coat of 20% PC, 20% Lime, 60% Mud.

UPDATE: Infill Brick

New brick made from 60% softer mud (infill). Also the bottom brick at high tide.
New brick made from 60% softer mud (infill). Also the bottom brick at high tide.

UPDATE: Another wall

I found this wall on the otherside of the estuary. It has been made recently as part of a Rotary/ Council funded walkway. It has large chunks in it and although huge seems softer than my mix.
I found this wall on the otherside of the estuary. It has been made recently as part of a Rotary/ Council funded walkway. It has large chunks in it and although huge seems softer than my mix.

UPDATE: 7 Months later

View from above at High Tide. I have added another thin layer 50 / 50 cement & lime / mud.
View from above at High Tide. I have added another thin layer 50% cement & lime and 50% mud to the top two bricks.

UPDATE: 8 Months later

Finished! Apart from a few cracks on the top I am happy with it.
Finished! Apart from a few cracks on the top I am happy with it.

 

The base is about 795mm deep. I am looking forward to measuring it over the next few years.
The base is about 795mm deep. I am looking forward to measuring it over the next few years.

UPDATE: 3 Years 5 Months later (August 2016)

mud brick
It’s so ugly!

The front bit has broken off, probably from people walking on it when the supporting mud it was sitting on got eroded away (I should have built a footing). It has stood up surprisingly well to erosion, the front bit is 390mm and the back 375mm a total of 765mm. So it’s loosing about 0.8mm per month. It’s in the waves for at least two hours per day. Not bad for a first try, and a heck of a lot better than the bank behind it! It’s kind of nice to see algae growing on it, I think I would like to find out if bivalves will grow on it if I moved it (maybe just the broken off bit) further out into the estuary. Bivalves might also help prevent it from eroding. I think this kind of mud sequestration is a great way to deal with legacy sediment, I want to create more prototypes.

UPDATE: 6 Years later (February 2019)

seawall

The rate of erosion seems to have slowed down a lot.

Little shag roosting. November 2020. Photo by David Doleman.
Note scouring at foot. August 2021

UPDATE: 10 Years later (February 2023)

The marine mud bricks finally fell over during Cyclone Gabrielle but are still working hard to reduce erosion.
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Organic rubbish collection

All this trash was in the creek just S.E.E of Taniwha St.
All this trash was in the creek just S.E.E of Taniwha St.

While I was watering the dying trees on Omaru Creek (please rain soon) I noticed people were putting out their trash for the local in-organic rubbish collection. So I hauled a bunch of stuff out of the water. Some of it was so rusted it must have been in there for years. The pile was bigger but some of the stuff I found in the bush (bike parts) got picked up by some collectors (sweet!).

I just walked past the pile after going to the 'River Talks' in GI, and 80% of the trash is gone. It must have had value to scavenging recyclers as it's not back in the creek. Wahoo!
I just walked past the pile after going to the ‘River Talks’ in GI, and 80% of the trash is gone. It must have had value to scavenging recyclers as it’s not back in the creek. Wahoo!

UPDATE: Inspired by the recyclers my son and I just pulled out about 60kgs of rusting steel from below the high tide line. I would have photographed my pile of fencing mesh, corrugated iron and shopping trollies but they picked it up so fast!

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Removed 25 TVs from Tamaki estuary

I decided not to wait for the council to get these out. It looks like a scrap dealer threw them over the cliff at Wai O Taiki Nature Reserve years ago and they have been leaking poison into the estuary ever since.

How I found them, tho most of them were covered in the mud (yes that is a dead dog). How I found them, tho most of them were covered in the mud (yes that is a dead dog).

In the other trash at the bottom of the cliff someone left me an old tent which I was able to use as a tarp to keep my car clean. In the other trash at the bottom of the cliff someone left me an old tent which I was able to use as a tarp to keep my car clean.

They did not want them at the local e-waste collection day but they said I could take them down to upcycle.co.nz during the week. They did not want them at the local e-waste collection day but they said I could take them down to upcycle.co.nz during the week, this is all of them on a trailer.

Upcycle were so awesome! They were happy to recycle the TVs for me even tho they would normally charge someone $250 for this much waste. And thats if the TVs are in good condition with valuable parts (these have been stripped). They were just as happy as me to see them out of our estuary, what heroes!

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Watering on Omaru creek

Dying Rewarewa
Dying Rewarewa

I have tried to find out who planted these trees but no one seems to know. Many are completely dead – it has been a very dry summer. I am trying to revive the rest with local creek water (only when the tide is going out) but I am worried about the salt content. I tasted it once and it was a lot less salty than the sea but I will not again, not since I smelt the waste water being pumped into the creek upstream!

UPDATE: It’s officially a drought. I have been giving each tree approx. 4L of creek water once a week. There is no noticeable return of any green leaves. Tho one of the Rewarewa with a tiny amount of green has not lost it. The creek water is getting smellier I am not sure how good it is for the trees. I am bringing my house water down for the only Kauri.

UPDATE: They all died. The drought was bad, but I don’t know why Auckland Council plants trees and does not look after them.

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Map of Tamaki erosion sites


View Tamaki erosion sites in a larger map

After a very muddy swim, my son (8yrs old) and I have started mapping local erosion areas. It looks like there are lots of obvious places where we can fix tracks, plant trees and build retaining walls. I would like to help get the silt and mud out of the Hauraki Gulf.

Check out a large version of the map here