3.1 Introduction
This chapter gives a brief overview of the history of Paokahu landfill from its inception in the late 1960’s to its eventual closure in 2002. The area around the landfill is located in the former Awapuni Lagoon, for which a brief description of the geology, hydrology and soils is given. Finally, the current management practices used at the landfill are summarised.
Much of the information contained in this chapter, particularly relating to the history, was obtained by reviewing the Gisborne District Council’s files held on Paokahu Landfill, while the information of the management practices comes from personal experience gained during my time managing the site as Solid Waste Engineer, for Gisborne District Council.
3.2 Site History
Gisborne City Council (which amalgamated to become Gisborne District Council in 1989) first became interested in developing a landfill in the Awapuni Lagoon area in the late 1960’s early 1970’s. The Council was interested in this area because of its proximity to the city, lack of residential housing, large potential capacity and plentiful supply of sand dunes which it intended to ‘mine’ for use as cover material. The proposed site was not within the boundaries of Gisborne City, but in the adjacent Cook County. The site was on a 522 acre block of Maori Freehold land, locally known as the Paokahu Block. At the time the land was under lease to the Economic Butchery Ltd who used the land for grazing. The
area was zoned as Rural under the Cook County Council’s District Scheme, which prohibited development of a landfill.
Gisborne City Council formally announced its interest in the site in June 1970.
The City Council applied under Section 35 of the Town and Planning Act (1953) for consent for a specified departure from the Cook County District Scheme on 20 March 1972, for 321 acres of the Paokahu Block to be rezoned as a refuse disposal site. Thirteen objections to the departure notice were lodged which included objections from the landowners, the trustees of the land and the Poverty Bay Catchment Board. A hearing took place on 6 July 1972 which resulted in
“consent in part” being given. Sixteen conditions were imposed on the development by the Cook County Council, most notable were:
• Consent was only given for 50 acres of the 321 applied for.
• The dune section of the block was not included.
• The GCC had to develop a comprehensive site plan detailing what the site would look like once the landfill had reached the end of its life.
Gisborne City Council appealed the decision under section 35(5) of the Town and Country Planning Act on the grounds that the whole site was needed to give some long term certainty to the City’s waste disposal operations. Gisborne City Council also stated that using the sand from the sand dunes for landfill cover was essential to the site operating successfully. The Town and Country Appeal Board heard the appeal in May 1973. The appeal was dismissed and the conditions imposed by the Cook County Council were upheld.
Although their appeal was dismissed the Gisborne City Council decided to continue with its plans to develop a landfill at Paokahu but in accordance with the conditions of the consent. As only 50 acres were consented, Gisborne City Council did not pursue acquisition of the land through the Public Works Act.
Instead it was decided to try and obtain a lease for the site. After some negotiation the Council and Mungatu Blocks (the trustees of the Paokahu Block at
the time) agreed terms on a 15 year lease. The lease was signed on 4 September 1975 upon which the Council took possession of the site.
The landfill opened 14 February 1977 and received a mixture of domestic, agricultural and industrial waste. Approximately 100 million cubic metres of waste was disposed of in the landfill during its life, averaging approximately 4 000 000 cubic metres per annum. Disposal peaked at 70 000 tonnes per annum in the1980/90’s of which approximately 60% was organic waste produced in the city’s vegetable processing plants. Tip fees were phased in during the 1990’s after which the total tonnages began to decrease and at closure the landfill was receiving less than 20,000 tonnes per annum.
An engineered liner was never installed beneath the landfill; instead the designers relied on the low permeable nature of marine sediments located under the site to prevent leachate migration into the surrounding ground water.
Only a portion of the site was ever used for dumping at any one time, and the active tip face moved across the site over time (Figure 3.1). The landfill typically practiced an accept, compact, and cover method of landfilling. Waste was tipped at the tip face (Figure 3.2), then compacted using a caterpillar compactor and the tip face covered at the end of each day. Initially sand from the adjacent beach was used for daily cover, but this practice was stopped in the1990’s and replaced by bark, a waste product from the Port of Gisborne log export operation. The exact volume of sand used in the landfill is unknown, but up to 8,000 m3 of sand per year was extracted between 1977 and 1997 for capping purposes.
In 1997 Gisborne District Council applied for consents to extend the landfill into adjacent land, known locally as the Gavins Block. The consent application was unsuccessful and the landfill closed on 31st December 2002; after which it was used as a temporary transfer station while a more permanent refuse transfer station was constructed in Gisborne.
Figure 3.1: Paokahu Landfill December 2000, showing the active tip face in the northern corner.
The landfill was finally completely capped in 2003. The cap is made up of 100 mm layer of bark placed directly over the refuse, overlaid with a 250mm thick layer of clay, 150mm of beach sands and finally a 200mm thick layer of top soil. Some older areas which had previously been capped had an additional cap placed on top consisting of 250mm layer of clay, 150mm of beach sands and a 200mm thick layer of top soil. The landfill cap is classified as a Buried Refuse Anthropic Soil under the New Zealand Soil Classification (Hewitt, 1992).
Figure 3.2: Paokahu tip face 1996.