The site of the old Hamilton Gasworks was contaminated with toxic chemicals that were leaching into the ground water. The owners and Hamilton City Council have rehabilitated the site, removing the most heavily contaminated soil and sealing the site.
Assessing the risks
In the early 1990s, a derelict site in central Hamilton on the corner of Clarence and Tristram Streets was purchased for redevelopment and found to be contaminated with hydrocarbons, phenols, cyanide and metals. Ground water under the site was also contaminated, and tar and toxic sludge were stored in an old underground pit.
Further research found that the site had been a gasworks from about 1895 until the early 1970s.
Risk assessments concluded that, given the current land use, the contamination posed little threat to human health or the environment, but maintenance workers would be at risk. However contaminants had degraded the ground water, making it unsuitable for use.
Making the site safe
A joint site investigation and management programme involving the new owners and the Hamilton City Council (in consultation with Waikato Regional Council) led to the removal of the tar and sludge together with the most heavily contaminated areas of soil. The whole site was then sealed with a waterproof surface to:
- protect future site users
- ensure any residual contaminants in the soil would not contaminate ground water.
Ongoing monitoring of the ground water is tracking the reduction in contamination since the site clean-up.
The waste tar, sludge and heavily contaminated soil removed from the site are being securely stored at a specially designed storage facility at Horotiu landfill until they can be treated to the required standards.
Because of this clean-up work, a previously unusable and unsightly piece of contaminated land has become a useful property.