- Additional soil and groundwater investigation,
- Acid sulfate soil (ASS) assessment
- Waste classification
- Preparation of waste management plan
The site area was small in the context of the development proposal and there were numerous access issues associated with the staging of the demolition works and the retention of some structures. Deep excavation and piling, in excess of 30m below ground level, was proposed and there were various soil waste streams to be generated. The management of soil waste was identified as a key project risk.
Anecdotal information was provided after the commencement of the JKE investigation that indicated that an adjoining property had identified hydrogen sulfide gas and odours during their basement construction. JKE needed to adapt the investigation plan to assess this issue.
JKE completed the investigations concurrently with JK Geotechnics to maximise the cost effectiveness of the drilling works. The deep geotechnical boreholes, required to facilitate the pile and basement shoring design, were utilised to obtain environmental samples at depth and to install groundwater monitoring wells. The design and installation of the wells was altered (from the initial investigation plan) so that the wells could be used to sample groundwater and also to assess potential risks associated with hydrogen sulfide gas. Multiple rounds of gas monitoring were undertaken and a Level 1 and 2 gas risk assessment was completed.
JKE also prepared a pile spoil management plan for the contractor to implement during the piling works in order to reduce the potential for mixing waste streams. The plan was designed to reduce the overall waste disposal costs substantially for the piling phase of the project.