Dairy Effluent Storage: Ponds, Tanks and Liners
It goes without saying that effluent storage is critical & requires careful planning and design.
Dairy effluent storage on NZ farms is usually one of four types: an above-ground tank, a lined pond, a compacted clay pond or a concrete pond. The right choice depends on your soils, your herd size, wet-period rainfall and what your consent requires. Good storage gives you the flexibility to irrigate only when conditions are right, which protects waterways and gets more value from the nutrients in your effluent.
- Peace of mind
- Increased flexibility around irrigating
- Effective utilisation of nutrients and water
- Reduced risk of effluent non-compliance
- Environmental protection
A well-designed storage pond is:
- sealed to avoid leakage to groundwater
- allows for ongoing operation and maintenance, and is appropriately sized for the volume of effluent produced now and in the foreseeable future
- compliant with regional and district council and Building Act requirements.
The right effluent storage pond for your farm
To help guide your decision-making, see A farmer’s guide to building a new effluent storage pond. It covers everything from planning and design to post-construction. The information below details some areas covered by the guide.
Storage options
Lined ponds and above ground tanks are the two options available when choosing an effluent storage system for your farm. Below are some pros and cons for each…
Above ground tanks
| Pros | Cons |
|---|---|
| Can usually be installed year-round little costs associated with earthworks not significantly affected by water table | Can be more expensive than lined ponds may require a building consent from district council some size restriction on what is available commercially. |
Lined ponds
| Pros | Cons |
|---|---|
| Less cost than above ground options can be less intrusive on the farm more accommodating of shape and design No size restriction | Wider range of costs depending on lining options and earthworks needed installation can be weather affected especially for clay lined ponds in some wetter parts of the country |
Selecting the right liner
Liners can be formed from compacted clay, concrete or specifically manufactured materials such as polyethylene (PE), polypropylene (PP), or rubber (EPDM).
To choose the right liner for you see the options below.
Compacted clay
| Pros | Cons |
|---|---|
| May have suitable clay on site for pond construction | Requires soil testing by a professional Requires technical expertise to compact clay correctly to achieve sealing requirement cracking can appear when ponds are empty, risk of leaking warranties may be more difficult to obtain potentially high cost if importing clay from off-site may require periodic re-lining of the pond after cleaning not favoured by all councils, you need to check first |
Concrete (Engineered cement composite)
| Pros | Cons |
|---|---|
| Less earthwork preparation required than with clay liners Flexible to withstand ground movement Withstands mechanical damage May have suitable clay on site for pond construction | Relatively new product for effluent ponds in New Zealand Warranties may be difficult to obtain, engineering expertise is essential Moderate to high cost |
Synthetic
| Pros | Cons |
|---|---|
| Good range of liners available good warranties available installation allows for gas and ground water dissipation may have suitable clay on site for pond construction | Some variation in quality of synthetics on the market moderate to high cost |
A Farmers Guide To Building A New Effluent Storage Pond
How much storage do you need?
Download the Dairy Effluent Storage Calculator (DESC) to determine storage needs. It contains a database of soil types and 30 years of daily rainfall records for many sites throughout New Zealand.
Converting storage calculator information to a working volume
DairyNZ has developed the Effluent Storage: Working Volume Calculator to calculate the dimensions and working volume of your effluent pond or tank, which is also useful for existing ponds or tanks. This article was kindly supplied by DairyNZ
Once you know which type suits your farm, the next step is working out how big it needs to be. Our guide on how to size effluent storage covers herd numbers, wet-period rainfall and consent conditions. For concrete builds, see our concrete effluent ponds. Whatever you choose, you will need to stir the pond to keep it working at full capacity.