Pre‑purchase due diligence: Limited soil investigation and waste classification, Rosehill NSW

Project summary

iEnvi was engaged to undertake a limited soil investigation and preliminary site inspection to support pre‑purchase due diligence for a property in Rosehill, NSW. The site was in use as an open car parking facility and was proposed for redevelopment to accommodate materials storage and a soil conveyor system, which requires an excavation pit.

What we did

• Desktop and on‑site preliminary site inspection targeted to areas of shallow and deeper soils, including the proposed conveyor excavation footprint.
• Targeted soil sampling across shallow areas and at depth in the vicinity of the proposed excavation.
• Identification and inspection of three existing groundwater monitoring wells and measurement of groundwater level during the site visit.
• Preparation of an in‑situ waste classification report based on soil investigation results.

Key findings

• Evidence of historical fill across parts of the site, likely placed by the current owner.
• Asbestos‑containing material (ACM) observed in fill soils (widespread potential impact across site soils).
• Minor concentrations of total recoverable hydrocarbons (TRH) and polycyclic aromatic hydrocarbons (PAH) detected in the saturated zone, indicating potential for groundwater impact in the excavation area.
• Three existing groundwater monitoring wells were located and a groundwater level recorded; groundwater is likely to be encountered at the planned excavation depth for the conveyor pit and may accumulate in the pit during construction.

Implications for development, transaction and compliance

• Development: The proposed conveyor pit will likely intersect the groundwater table and require active water management during excavation (dewatering or pumped water treatment/disposal), which will add complexity, time and cost to construction.
• Remediation & waste management: Presence of ACM in fill triggers the need for an asbestos management plan for construction and long‑term soil management. Soil classification results inform whether excavated material can be reused on site, requires classification and off‑site disposal to licensed facilities, or requires special handling.
• Transaction risk: The findings reduce transactional uncertainty by identifying likely contamination sources and practical mitigation measures to incorporate into purchase negotiations, development budgets and conditions of consent.
• Regulatory: The report noted there would be no duty to report contamination under Section 105 of the NSW Contaminated Land Management Act 1997 if an asbestos management plan is developed for the site; this legal interpretation should be confirmed with regulators and/or legal counsel as part of final due diligence (see verification notes below).

Recommendations

1. Prepare and implement an asbestos management plan covering construction controls, worker protection, soil handling and long‑term management for any soils that remain on site.
2. Commission a focussed groundwater assessment (outside the original scope) to confirm whether TRH/PAH concentrations in saturated soils correspond to dissolved or mobile groundwater contamination and to characterise water quality where dewatering may be required.
3. Collect and analyse groundwater samples that may accumulate in the proposed excavation pit prior to disposal; excess groundwater may require treatment and disposal as contaminated groundwater where analytical results exceed relevant criteria.
4. Use the in‑situ waste classification report to plan segregation, temporary stockpiling, transport and likely disposal routes and costs for excavated soils during redevelopment works.
5. Factor additional time and budget into the development program for asbestos management controls, potential dewatering and off‑site disposal where required.

Practical takeaways for buyers and developers

• Early targeted investigation reduces surprise costs at construction by identifying likely groundwater inflow and the need for asbestos management.
• Waste classification at the site stage allows procurement teams to budget disposal costs and confirm reuse or off‑site disposal options.
• Confirm any statutory reporting obligations and regulatory expectations (including the applicability of s105 CLM Act advice) with local authorities and legal advisers before finalising contracts.

Contact iEnvi

If you need a fast preliminary site investigation or a more detailed site investigation to support development consent, finance or transaction due diligence, contact iEnvi for pragmatic, commercially focused advice. Phone 13000 43684 or visit /contact/ to arrange a confidential discussion.