Remediation

Where a change of use and development of land is proposed and contaminant residues exceed the relevant criteria for the proposed land use then remediation or management measures may be necessary.

Once a site has been identified as requiring mediation or management a Remediation Action Plan (RAP) should be prepared. A RAP should: ⁴⁷⁴⁶

• Set remediation or management goals;
• Document all risk-reducing procedures and plans;
• Establish recording and reporting mechanisms;
• Establish the environmental safeguards required to complete the remediation in an environmentally acceptable manner; and
• Identify and include proof of the necessary approvals, permits etc.

In some instances remediation, or a “full clean up” will not be achievable, or the risks from are adequately mitigated by preventing exposure to the contaminant, for example through concentrating the exposed site and only using non-exposed areas. In this instance a Site Management Plan (SMP) will be used alongside an RMP. The LMP will generally set out a clear monitoring strategy.

RAPs and SMP will generally form the basis for proposing consent conditions. Consent conditions for contaminated properties may include any of the following:

• Full site clean-up, which can include but is not limited to excavation and removal of contaminated soils;
• Dilution;
• Containment such as 'cap and contain'
• Treatment of the contamination to safe levels in the soil; or
• Vertical blending by deep ploughing of the soil with clean soils. (though this is the least preferred method of the council as it can lead to larger volumes of soils being contaminated).

Case study: Remediation of the Tui Mine at Mt Te Aroha in the Waikato

 Tui mine was mined for metals, including copper, lead and zinc operating from 1967 to 1973. When the mine became uneconomic, the owners went into receivership, and the mine was abandoned in 1975. The tailings, ore dumps and mine workings continually leached heavy metals and acid rock drainage contaminating the neighbouring streams, which flowed into two different catchments including the river running through the centre of the Te Aroha township. Reports on the mine tailings impoundment indicated the structure was at risk of ‘collapse in a moderate seismic event or an extreme weather event and such events could have resulted in over 90,000 m³ of mine waste liquefying and flowing down the Tui stream past the edge of Te Aroha.' ⁴⁷⁶⁵

The Remediation Project took 2 years. It was designed to: ⁴⁷⁶⁶

• Stably and securely contain the tailings;
• Reduce levels of contaminants into the neighbouring streams;
• Improve the safety and security of the site;
• Improve the sites visual appearance; and
• Address the impacts of the mine, as far as practicable, on the taonga of the Te Aroha maunga (Mt Te Aroha) for iwi. 

The remediation project was a collaboration of central, regional and local government agencies working with iwi and the local community. It cost $21.7 million and 160,000 man hours went into the planning, management, engineering and construction processes. 

Post-remediation monitoring undertaken for Waikato Regional Council has revealed significant improvements in the ecological health of both the Tunakohoia and Tui streams. ⁴⁷⁶⁷

 

The Contaminated Sites Remediation Fund

The Ministry for the Environment administers the Contaminated Site Remediation Fund to assist regional councils with the investigation and remediation of contaminated land where a party cannot be held liable.

Last updated at 3:04PM on February 8, 2018