Astron was engaged by the Shire of Manjimup to address a work approval response from the Department Environmental Regulation. This involved undertaking an assessment of subsurface conditions and permeability testing within the proposed liquid waste ponds and existing overflow pond to inform the adequacy of the proposed construction standard. An additional two groundwater monitoring bores were installed and sampled to complement the existing monitoring bore network and provide a baseline up-gradient and down-gradient assessment of the groundwater for the proposed pond location.
Five test pits were excavated to a maximum depth of 3.1 m below ground level within the vicinity of the proposed liquid waste ponds and existing overflow ponds. Geological samples were taken with laboratory submission for permeability and bulk dry density analysis undertaken. Extensive geological logging on site was also recorded. Installation of two strategically positioned groundwater monitoring wells at the waste management facility where successfully installed and geological logging provided additional insight to the aquifers and presence of semi-permeable clays on site. Collection of three primary groundwater samples were analysed for hydrocarbons, metals and coliform based on the liquid waste acceptance categories and DER requirements.
Following this initial stage of data collection, a detailed hydrogeological and geological report was compiled to accompany the landfill approval documentation in accordance with the DER requirements. This report extensively detailed the geological/hydrogeological stratum, hydrogeological contours, groundwater sampling plan, groundwater quality and any potential environmental constraints. Works approval was successfully submitted with the waste ponds scheduled to be installed in early 2016. Groundwater sampling to monitor the health of localised groundwater will occur once the ponds are in use.