Construction of Storage Facilities    

Answers to frequently asked questions about the construction of storage facilities.

Do I Need to Pay an Engineer to Permeability Test My Ponds?    

Tasman District Council supports IPENZ Practice Note 21 – ‘Farm Dairy Effluent Pond Design and Construction’ in getting a suitably qualified person and/or experienced pond constructor to provide specific written details to support that the pond is constructed to the appropriate standards. These details should at least include the design, construction and material used. This will help provide evidence that best management practices were adhered to and may spread the liability if a problem occurs in the future.

IPENZ Practice Note 21 – Farm Dairy Effluent Pond Design and Construction

Clay liners have a number of complex issues which may result in the sealing standard not being met. It is therefore recommended that new clay ponds are constructed as recommended by IPENZ Practice Note 21, which includes being overseen by a suitably qualified person and issue of a supporting producer statement.

If you have an existing pond and a compliance officer suspects that is it unsealed you may be required to prove that the pond is sealed to the required standard. If you have no construction records available that prove the pond is sealed you may need to hire an engineer to perform a permeability test which can cost several thousand dollars. It may be most cost effective to upgrade your storage facility than prove it is sealed. If you cannot provide information proving the pond is sealed further enforcement action could result. This could include a notice ordering you to cease using an unsealed holding facility.

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I Have a Digger, Can I Build My Pond Myself?    

There are no rules that state you can not construct the pond yourself. However, in order to achieve a safe and compliant pond the construction work needs to meet a high standard. Consideration needs to be given to the materials used and the level of compaction in order to achieve the permeability requirements. The farmer needs to be able to prove compliance with the pond sealing standards, which is likely to require engineer signoff. Farmers may not be able to establish appropriate sealing if they build the pond themselves.

If the site is not properly selected and pond properly constructed there can be issues with groundwater intrusion. It is recommended, under best management practice, that experienced and qualified professionals are employed in the design and construction process. These professionals will be familiar with the ‘Farm Dairy Effluent Design Standards and Code of Practice’ as published by Dairy NZ, and the ‘IPENZ Practice Note 21 – Farm Dairy Effluent Pond Design and Construction’ and follow up-to-date information about pond construction as it becomes available.

However, it should always be remembered that, even if professionals are referred to or engaged, the ultimate responsibility for the construction and compliance falls to the farmer.

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Do I Need Consents for Earthworks or Other Matters to Construct an Effluent Storage Pond?    

Possibly – some effluent storage ponds are very large, requiring extensive earthworks to both construct the dam and to clay line the impoundment (where required). Consents may be required by the Council for the construction earthworks, the damming and diversion of existing watercourse depending on the scale, nature and location of the impoundment and associated earthworks.

Even if no consents are required, appropriate erosion and sediment controls must be installed and maintained for all earthworks to be a permitted activity.

If the maximum potential (the dam crest level) exceeds 20,000m³ and 3m depth then a building consent is also required from Tasman District Council. Consent requirements in relation to earthworks, damming and diversion are very site and project specific and you should always seek specific written advice from Council Planners or Building Consent staff at Tasman District Council at the earliest possible stage when planning your effluent storage pond. Our staff are happy to help you with information on requirements.

You may also need to meet additional requirements from your Council so you should consult with them before constructing any effluent pond or tank.

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How Do I Find a Good Effluent System Designer/Advisor? Who Will Give Me the Best Advice?    

DairyNZ in conjunction with Regional Council’s and industry representatives have produced the ‘Farm Dairy Effluent Design Standards’ and ‘Farm Dairy Effluent Codes of Practice’, and the ‘IPENZ Practice Note 21 – Farm Dairy Effluent Pond Design and Construction’ which can be accessed from Dairy NZ. Professionals involved in dairy effluent systems should adhere to these and any technical documents as released. It is recommended to use only qualified and experienced professionals who can give you some written design guarantees to show that they system would be fit for purpose providing best management practices are adhered to.

An accreditation system has recently been established primarily for effluent land application system designers. As companies are approved by the scheme they will be listed on the effluent accreditation website. Many of these designers will have been through the Massey University course on effluent system design. However, it will take time to get all companies registered, so it is important to consider this when making your decisions. Chartered professional engineers can also be found on the IPENZ website.

Useful Links

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Do Contractors Used for Construction of Effluent Facilities Have To Be Certified?    

Ultimately the responsibility of the effluent system falls to the farmer. If a farmer engages the services of an effluent system designer, the roles and responsibilities of engaging and overseeing contractors can be shared as agreed with the designer.

It is recommended that whoever is responsible for engaging contracted services ensures they have given clear instructions to the contractor, that the contractor has experience of the work they are carrying out and a written contract or agreement is in place outlining the details and responsibilities of both parties.

DairyNZ in conjunction with InfraTrain and the Opus Environmental Training Centre are developing short training courses on farm dairy effluent pond design and construction for effluent service provider contractors which are now available.Moren information on these training courses is available from the NZ Water & Environment Training Academy website.

NZ Water & Environment Training Academy

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Can Tasman District Council Audit My System and Give Me Advice on Upgrading It?    

Council compliance staff are not technical specialists in effluent system design or construction and therefore cannot provide specific technical design advice. They are skilled in assessing the system for non-compliance and will be able to tell you if your system is compliant at that point in time. Dairy companies and DairyNZ are also key drivers in industry standards so can provide some on farm services and access to advice. There are also a number of independent consultants who provide on farm advice around effluent systems. Some Council staff are familiar with available systems and can give you some advice as to where the information you require can be obtained.

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If You Have an Existing Two Pond System Already Is It Best To Combine To Make One Pond?    

Each two pond system should be assessed individually as to whether it is suitable for use in an upgraded effluent system. If the system was previously part of a consented discharge to water treatment system, then it is likely to be located near a watercourse. If this is the case it is worth considering whether it is an appropriate location for a storage facility as current recommendations are to site facilities a minimum of 20m away from a watercourse. Siting facilities further away from watercourses helps lessen the risk of significant contamination should the storage facility fail for any reason.

Electing to have a two pond system can provide some additional management benefits. For example the ability to carry out maintenance work on individual ponds, increased pumping potential by pumping from multiple ponds at optimum times, and the potential to manage effluent of different nutrient and water values in different ways to maximise on farm efficiency.

Two pond systems could incur additional costs associated with construction, maintenance and management. Therefore it is still important to assess ongoing management and financial implications when selecting a system.

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What Are The Options for Separating Rainwater From The Effluent System?    

Diverting rainwater from the effluent system can help reduce the amount of storage required and the volume of effluent to manage. Options to consider are:

  • Gutter and divert existing roofs and other sealed areas to minimise the catchment area.
  • Use cambers and cross drains to divert rainwater off raceways to prevent it collecting in yards.
  • Have a separate system for collecting diverted rainwater from cleaned yards. This may only have a low nutrient content so while it may not be of an acceptable standard to be discharged to waterways, it could be used for irrigation.

There are also opportunities to make use of rainwater in other aspects of the farm system. DairyNZ have developed a guidance book ‘Smart Water Use on Dairy Farms’.

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How Do I Construct Ponds on Peat?    

Construction on peat can be very challenging and each site may have different issues. It is recommended to engage a suitably qualified person or engineer to help establish the most appropriate design to avoid any substance or water intrusion issues. This would also be the case for other challenging soils, high water tables and steep topography.

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Can You Use Retired Effluent Ponds?    

If an old effluent pond is brought back into use it must meet the same compliance standards as stated by the Council. There may be some construction issues around relining an old pond due to gas and oil composition. It is recommended to consult with a professional before commencing any work.

Tasman District Council supports the recommendations in ‘IPENZ Practice Note 21 Farm Dairy Effluent Pond design and construction’ surrounding pond siting. Some old ponds may not meet good practice guidelines and careful consideration should be given as to whether a new pond would be the best solution for the farm.

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