A new poo tank

By Samantha Tennent

Time was tight as a Waikato farmer tackled the big job of cutting himself a new effluent pond.

It took two tractors and trailers operating for a week to remove all the dirt that had been tracked into a Waikato farmer’s effluent pond over the past 40-odd years.

Stephen Neville owns the 164ha farm milking 330 cows at Reporoa. Over the years the property has been expanded, and more cows, more concrete and modern regulations meant the old system was due for an upgrade – but first he had to excavate the old one.

“The original pond was built in 1984 by damming the gully below the cowshed and forming two ponds,” Neville said.

“Back then the farm was 90ha with a 10-a-side dairy shed and we were milking 160 cows.

“Now there are 330 cows calving in autumn on 164ha, with a 24-a-side shed and covered feedpad and due to the new regulations we needed to upgrade our effluent pond.”

The pipework from the cowshed, the races and the feedpad were all going to the existing pond and to prevent solids and dirt from entering the tank again Neville was keen to install sandtraps. But due to the location, it would have been difficult to install a lined pond so he decided the best option was an aboveground pond from Kliptank with a 1.4 million litre capacity.

But it was a challenge to get the new pond installed in time for the herd to start calving again.

Over the years the farm has expanded and a new effluent system is being installed and a covered feedpad built. Earthworks at the site of the new storage site.

“There was a tight window to have the new pond ready, though, as we only had four weeks between dry-off and calving since we were using the same location.

“It was full steam ahead the day the cows were dried off, removing the old dam and digging out the sand and dirt that had accumulated over the years.

“Using two tractors and trailers we carted a massive amount of dirt to enlarge the pond to fit the new tank.”

Kliptank provided some basic information that guided Neville in the preparation process as he did a lot of the work himself. He credits his experience in farming and “give it a go” attitude for his ability to tackle projects like this.

“I’ve always just given things a go, you can only learn it by trying.”

Since it was the middle of summer he did not anticipate the amount of groundwater they would be dealing with as well as contending with one of the wettest summers on record. They excavated the back of the hill and laid 70m of drainage pipe to remove the water, which flowed like a creek.

For the pond foundation, they utilised pumice from the farm to fill the hole and layered a geotextile cloth before adding 200mm of metal and another layer of pumice.

The new tank should be more than enough for their system.

“A lot has certainly changed since we built that old pond and there were a lot of considerations to determine what would be the most appropriate system now.

“Being solely autumn calving, the shed is in full swing during the wettest part of the season and there is a lot of concrete around the shed and feedpad that captures rain and runoff.

“We are hoping to have at least a month’s worth of storage but we do have the ability to move it.”

They will maintain the same effluent spreading processes they had before, using the irrigator for liquid and a slurry tanker for the solids. They purchased the tanker to help deal with the solids coming off the feedpad as it does not get blocked like an irrigator tends to. The solids get spread monthly, usually onto crop paddocks.

The sandtraps will help capture silage and the feed trough overflow that mixes in with the effluent on the feedpad before it makes its way to the pond.

“We have always tried to scrape off as much silage as we can into the solids bunker but there’s always some that gets into the effluent, so the sandtraps will help prevent that problem.

“We should have all our bases covered now, it has been a lot of work but I am really happy with how it has turned out.”

His son, Alastair Neville purchased the herd in 2010 and has been back home running the farm since he returned from university at the end of 2011. They began transitioning to autumn calving in 2017 with that being their final spring calving.

Despite having a feedpad, pasture is their main focus. They installed it to help utilise grass better and the herd spend around four hours on it each day around milkings. Their staple diet consists of grass, maize and lucerne silage, which is stored in bunkers beside the feedpad. They also utilise kiwifruit, a palm kernel blend and sometimes carrots or other vegetable waste.

Now the system is almost complete,

Neville is feeling relieved as it will be their final piece of main capital expenditure for a while.

“It should be smooth sailing from now on.”

His feedback to other farmers who are starting to look at their effluent options is to take it on a farm and site basis to determine the best fit.

“A lot depends on where your cowshed is situated and the type of system you are running. Do your homework and get a good understanding of what will be right for your farm.” n