Storage and disposal
All animal effluent and wastewater generated from: dairies and adjacent entry/exit races, stock holding/sale yards, feed/stand-off/loafing pads, wintering barns, piggeries, poultry farms, stock underpasses, and transit races (if used for standoff and the like) must be contained and/or reticulated to a storage/treatment system.
- Weeping walls for solids separation.
- Large volume contingency storage.
- Land application as the primary means of disposal.
- Resource consent to discharge when soils are saturated.
Sludge bed/weeping walls are designed to remove solids from farm dairy effluent prior to land application/storage.
Advantages of adequate contingency storage include:
- Ease of management.
- Less demand on labour when farm systems are under the most pressure, that is, during calving and wet conditions.
- Land application can be timed to optimise nutrient recovery.
- Irrigators can be run for long periods in a steady state of operation when conditions are suitable.
Effluent can be stored until conditions are suitable, reducing the risk of:
- Unnecessary contamination of water;
- Non-compliance with regional rules;
- Surface or ground water contamination; and
- Loss of valuable nutrients.
Contingency storage ponds
Northland soils are often saturated from May through to October. It is therefore recommended that enough storage is provided to hold all effluent generated over that period.
The effluent ponds must be at or near empty going into winter. A full pond has no storage. Ponds should be emptied in autumn and kept empty as long as soil conditions are suitable.
Research has proven that if effluent is applied to saturated soils it can result in up to 80% of the effluent running off to surface or ground water. Therefore, to comply with regional rules, effluent must not be applied to pasture when soils are at or near saturation.
Operating procedures should include:
- Ponds at or near empty prior to winter.
- Level of the pond(s) kept low by applying effluent to land for as long as soil conditions allow.
- Store effluent when soil conditions are not suitable for land application.
- Divert as much stormwater as is practical – particularly when rain is forecast.
Note: effluent should only be irrigated to land when soils are in moisture deficit (that is, dry) and pasture is actively growing.
Additional storage is often required when:
- There is an increase in cow numbers;
- The dairy is used for winter milking;
- The yard is used for stand-off;
- There is an open stand-off or feed pad; or
- Stormwater is not routinely diverted.
Recommended storage volumes:
The council's farm dairy effluent team will provide recommended minimum storage volumes on a case-by-case basis, on request.
These volumes are based on:
- The number of cows milked;
- The milking regime;
- Stand-off/feed pad use;
- Average local rainfall;
- Catchment surface areas (including the ponds); and
- Stormwater diversion.