Client: Central Otago District Council

In 2019, Central Otago District Council (CODC) commenced a project to install a reticulated network to collect wastewater from all residential and commercial properties in the township of Clyde. More than 37,000 m³ of soil disturbance was required to install main lines and lateral connections to each property including soil disturbance on land where contaminants may be present in soil due to hazardous substance storage, use or disposal.

e3Scientific was commissioned to complete a Preliminary Site Investigation (PSI) to assist CODC manage the risks associated with contaminants in soil, as well as satisfy requirements of the National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health (the NESCS). The primary purpose of the PSI was to identify areas of potential contamination within the project area so that appropriate protocols for soil disturbance could be developed.

Based on a systematic review of multiple historic and contemporary sources of information, twenty-two discrete areas of likely HAIL activity were identified within the project area. These sites were associated with persistent pesticide use, printing, fuel and chemical storage, metal work, motor vehicle repair, railway yards, wastewater treatment and disposal, and poultry farming. Potential contaminants associated with these HAIL activities included persistent pesticides, heavy metals, petroleum hydrocarbons, per and poly-fluorinated alkyl substances (PFAS), and asbestos. Additionally, e3s identified the potential for lead and asbestos to be present in soils immediately surrounding buildings where lead-based paint and/or asbestos containing material may have been used.

As a practical alternative to completing additional detailed site investigations, suitable precautions for ground-breaking activities within the investigation area were established and documented in a construction-phase Contaminated Soils Management Plan (CSMP). Land within the project area was classified into three categories, with different management procedures applicable for earthworks to reflect the risks associated with each category. Controls on dust management, stormwater and groundwater management, soil handling, stockpiling, re-use of soils, off-site soil disposal, use of imported material, accidental discovery, worker health and safety, and management responsibilities were included within the plan.

The PSI and CSMP were used to support non-notified applications for consent and have since been used by the lead contractor to safely manage soils disturbance during this project.