10 March 2006 Chapter 14 - Discharges of Waste to Land Education is the key means of changing people’s attitudes and behaviour. If most of the community is attempting to achieve desired outcomes then regulation is only needed to ensure complete community achievement of outcomes. 14.3 On-site Management of Domestic Wastewater in the Marlborough Sounds Almost all houses, holiday homes and buildings used for visitor accommodation, outside of Picton, Waikawa and Havelock, rely on on-site systems to manage domestic wastewater. This means that domestic wastewater generated in the building(s) receives initial treatment in some form of treatment unit, such as a septic tank, and is then discharged into or onto a land application area on the property. Contaminants present in the wastewater, such as bacteria and nutrients, are then further treated or absorbed as the wastewater passes through the soil. In the Marlborough Sounds, domestic wastewater is discharged into soils of low permeability, into thin soils with limited ability to treat contaminants, or into extremely permeable alluvial soils. In all cases, there is the potential for contaminants to travel beyond the land application area, and into the surrounding environment, through runoff or infiltration. Most buildings used for residential or accommodation purposes in the Sounds are located in close proximity to streams, creeks, underlying groundwater or coastal water. This means that, if the on-site wastewater management system servicing the building performs poorly, there is a risk that the subsequent discharge will contaminate water. The Council’s monitoring has already established that there are elevated levels of bacteria in some coastal waters over the summer months. The Marlborough Sounds support significant marine farming and tourism industries that rely upon a high standard of water quality. The coastal waters are also an important recreational resource and have spiritual and cultural significance to local iwi. For these reasons, objectives contained elsewhere in this Plan create an expectation that water quality is to be maintained at or enhanced to an SG standard (see Chapter 9 for further details). It is therefore clear that the risk of contamination needs to be managed. This involves two key steps. Firstly, it is important to improve the performance of existing on-site systems over time. It is estimated that there are in excess of 3000 existing systems in the Marlborough Sounds, the performance of which is extremely variable. This is because: (a) The systems are not necessarily compatible with the site conditions or current occupancy of the building, and were often based on dated standards. For example, many septic tanks in the Sounds discharge wastewater into soak pits or short trenches, which have a tendency to eventually fail when installed in soils of low permeability. The older the system, the greater the potential for failure; (b) The age of the on-site system can mean that the various components are no longer watertight and may therefore leak; (c) Not all systems are maintained in an efficient operating condition. A lack of maintenance can contribute to the potential for failure identified in (a). 14 - 7