Wairau/ Awatere Resource Management Plan Performance Conditions are included to protect surrounding residential land Conditions uses from excessive noise. The above methods are required to ensure the effective, efficient, and safe operation of the District’s airport facilities, whilst minimising any adverse effects on surrounding areas. 12.8 Lake Grassmere Salt Works Area 12.8.1 Issue The sustainable management of the existing environment of Lake Grassmere, its surrounds and adjacent waters of Clifford Bay whilst enabling solar salt production of Lake Grassmere. Lake Grassmere has been used since 1943 for the solar production of salt. The ability to produce solar salt at Lake Grassmere arises from low rainfall, high sunshine hours, strong drying winds during the summer months, generally from the north-westerly direction, a large area of flat terrain with impervious soils located close to the coast, unimpeded access to sea water and ready access to transport facilities. While these factors are important, the production of solar salt is difficult and it must be carefully managed. Approximately 50% of New Zealand's annual salt consumption and specialist high grade salt is produced from Lake Grassmere and exported. The operations are unique in New Zealand, while some of the methods used to produce the solar salt are unique in the world. It is because of this uniqueness, its importance nationally, regionally and to the district, that special provision for the salt works is made in the Plan. Sea water (coastal water under the Resource Management Act 1991) is pumped into the Lake and then through a series of concentrating ponds as it increases in strength. Salt is finally deposited on the bottom of the crystallising ponds in summer and harvesting usually begins by early March. Solar salt production is adversely affected by rain storm events. Production can also be adversely affected by dust and air-borne contaminants and the possibility of contaminants in stormwater from adjacent sealed roads and farmland. These adverse effects are mitigated to an acceptable level by careful management of the stormwater in three ways: • A dedicated system of canals for stormwater extending generally northwest, north and east from the Cattle Creek rail bridge around the western, northern and eastern periphery of the property; • Decanting rainwater off the top of the crystallising and deep storage ponds, either to the main lake area or disposal via the stormwater canals; and • Management of the inflow of stormwater via creeks and drains into the main lake. In extreme storm conditions (twice in the last 45 years) it has been necessary to cut a temporary outfall through the sand dunes and gravel beach about 100 metres south of the sea water intake to allow the excess stormwater to escape. A variety of storage and processing facilities on the property is associated with the harvest of solar produced salt from the crystallising ponds. Salt is stockpiled in large 12 - 24