HDC 26-006 Hawarden Oxidation Ponds Desludging

2026-11-03

Hurunui District Council is looking for a suitably qualified Contractor to undertake the desludging of the Hawarden oxidation ponds. Hurunui District Council (HDC) operates the pond-based wastewater treatment plant of Hawarden. The plant consists of two oxidation ponds. Pond and sludge surveys were undertaken in 2024, which showed sludge accumulation requiring desludging to ensure continuing discharge quality in line with the conditions set out in the Resource Consents.The following Tender is for the desludging of both treatment ponds and the disposal of the sludge in geotextile bags to be located in a lined containment bund on adjacent land. The design and construction of the bund, the supply and installation of the geobags as well as of the filtrate return pumping station are also part of the contract.The work includes in particular:-The preparation of the ground and construction of a lined containment bund in the location indicated on the aerial photo and specified in the attached drawings (refer Appendices 3 and 4)- The supply and installation of adequately sized geotextile dewatering bags.- The design and construction of a filtrate return pumping system, its connection to the lowest point of the bunded area and the supply and installation of a discharge line to the inlet of the primary treatment pond.- The desludging of the treatment ponds using a sludge dredge or similar and the pumping of the sludge into the geotextile bags with optimised injection of a polymer to promote rapid dewatering.- The establishment, after a minimum of two months after the final filling of the bags, of the quantity of sludge removed through a sludge dryness analysis and bag volume calculations- A post-desludging survey of the ponds using the same coordinates as per the last survey to establish the ponds’ base and remaining sludge level.On completion of the desludging work, the Contractor is to leave a clean site with a robust and safe geotextile bag containment, drainage and automated filtrate return pumping system

New Zealand

2026-08-15