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Effluent storage

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3 min read

Storage options Selecting the right liner How much storage do you need? Pond videos Technical Resources FDE Pond Design and

Effluent storage on your farm is crucial and requires careful planning and design. With a well-designed storage system, you'll experience peace of mind, improved irrigation, efficient use of nutrients and water, and enhanced environmental protection. Your storage options include lined ponds and above-ground tanks, each with their own advantages and drawbacks. To select the perfect storage, consider factors like cost, installation conditions, and local regulations. Liner choices range from compacted clay to synthetics like polyethylene. Tools like the Dairy Effluent Storage Calculator can help determine your storage needs. Also, resources like video guides and technical literature are available to help in the planning and construction process.

DairyNZ is currently consulting on an update to IPENZ Practice Note 21 - Farm Dairy Effluent Pond Design and Construction. The new appendix updates the best practices for pond seepage testing: Pond Seepage testing appendix

We would like your feedback on this update. You can either:

Consultation closes on 25 May 2024

Having well-designed and constructed storage facility will save you time and money. The key is good planning and working with the right people. The benefits of a well-designed storage system include:

  • 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

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.

Pond videos

The video playlist below shows the various aspects of designing and constructing an effluent pond including site selection, soil testing at the lab, and the construction process. A pond safety video is also included.

Dairy Effluent Pond Construction Soil Testing

1 / 4 videos 3:14 min

Dairy Effluent Pond Site Selection

2 / 4 videos 2:19 min

Dairy Effluent Pond Construction Process

3 / 4 videos 4:43 min

Pond Safety

4 / 4 videos 3:49 min

Technical Resources

IPENZ Practice Note 21 - Farm Dairy Effluent Pond Design and Construction has a strong engineering focus and covers design and construction principles, clay liners for ponds, geomembrane (synthetic liner) selection and details about ponds and tanks constructed on peat.

FDE Pond Design and Construction with Hauraki 'Marine' Clays

Constructing effluent storage ponds in Hauraki marine clay may require different construction techniques. This chapter describes the engineering process. The case study shows the first pond to be built using this method.

Last updated: Sep 2023
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