|
Highlights
- Drilling investigations and permeability testing
- Development of a conceptual model of groundwater flow
dynamics
- Modelling of groundwater inflows and dewatering requirements
during construction.
Background
The need to plan and design settlement basins for sludge
retention necessitated an assessment of hydrogeological
conditions at the site. The intention was to line the settlement
basin with geomembrane to preclude leakage or ingress of
groundwater.
C. M. Jewell & Associates Pty Ltd was engaged to undertake
an investigation and make the assessment. The project entailed
drilling, logging piezometer construction, permeability
testing, water level surveying and sampling of three shallow
boreholes. The derived data was subsequently interpreted
using both analytical and numerical modelling.
Hydrogeological Environment
The basement rock of the area is weathered latite (a volcanic
rock). It is overlain by either estuarine sediments or residual
soil. A thick layer of fill material, comprising slag and
coal wash, covers the site. A water table is perched within
the fill material. The underlying estuarine sediments have
low permeability, of the order of 1x10-6 to 1x10-7 metres
per second. The principal source of groundwater inflow to
the settlement basins is the perched, unconfined aquifer
of the fill materials. The conceptual model and parameters
derived in field investigations were integrated into a two-dimensional
model of a section perpendicular to the settling basin.
This allowed the simulation of the groundwater inflow rates
during the excavation and construction of the settling basin. 
|
Projects