Dairy effluent

As a general rule, farm dairy effluent must be discharged to land.

Key points

• All discharges of farm dairy and feed pad effluent require a resource consent.
• Those with existing consents allowing discharge of treated effluent to water are required to switch to land-based disposal within a reasonable timeframe as consents expire or earlier. Plan ahead and talk to the Council at a very early stage.
• Contingency discharge to water is allowed only on farms with high-risk soils, generally on the upper ring plain where there is high rainfall, undulating steep terrain, and high drainage density limiting the ability to irrigate to land at all times. High levels of effluent treatment are required.
• Before upgrading or putting in new systems discuss with Council compliance staff what’s required.

Other useful information

• If you've got an existing consent allowing discharge to water, the Council can provide advice and assistance before the consent is due to expire and discuss current requirements with you to ensure the renewal/change process runs as smoothly as possible.
• Effluent holding pond storage requirements are determined by the Massey University Farm Dairy Effluent Storage Calculator or its equivalent, based on the size of the herd and other farm-specific factors. A list of people accredited to use the calculator is available online(external link).
• It's critical to provide sufficient storage to ensure effluent is not irrigated when soil is saturated, causing run-off to surface water. You'll also need a stormwater diversion device, so that rainwater is directed to land and not to the holding pond. Irrigation of effluent to land must be done via an irrigation system that is properly designed and operated.
• Existing oxidation ponds may be used for storage. New ponds can be lined with compacted clay or synthetic liners. Industry best practice is that the permeability of the pond sealing layer must not exceed 1 x 10⁹  m/s.
• Any slope greater than seven degrees is considered high risk for irrigation. This means that a low-rate application system should be used on these areas so no surface runoff or ponding occurs. Generally, more storage will be required in these cases.

What you need to ensure

When discharging effluent to land, resource consent conditions typically include:

• Design, construction, location, operation, and maintenance of the effluent storage facilities, including the storage volume;
• Location, size and physical characteristics of the irrigation area;
• Application rate and frequency of the discharge, including the return period between applications;
• Separation distances from property boundaries, dwellings, places of public assembly, surface water or bores, wells or springs used for water supply purposes or from known urupa and marae sites;
• Prevention of ponding or run-off to surface water;
• Managing effects of the discharge on any public water supplies;
• Duration of consent (this will be for a longer period of time for a discharge to land consent, than for a discharge to water consent);
• Review of the conditions of consent and the timing and purpose of the review;
• The payment of administrative charges; and
• Monitoring and information requirements relating to matters that the Council has reserved control over.

Design guidelines

The Taranaki Regional Council uses industry good practice guidelines for the design, construction and maintenance of systems for the land disposal of farm dairy effluent that will meet its requirements.

Taranaki Regional Council Dairy Effluent Pond Guidelines

Guide to Managing Farm Dairy Effluent - DiaryNZ(external link)