|
Highlights
- Hydrogeological characterisation of Botany Sands
- Regional flow modelling
- Fine scale modelling of drainage/dewatering works.
Background
The motorway from Woolloomooloo to Sydney Airport includes
an extended cutting through unconsolidated sediments (the
Parkway) and a cut-and-cover tunnel (the Dacey-Todman Tunnel).
The depth of the cutting necessitated evaluation of dewatering
options and assessment of impacts which might arise from
a reduction in the groundwater pressures in the surrounding
area.
Leighton Contractors Ltd and Maunsell Pty Ltd commissioned
C. M. Jewell & Associates Pty Ltd to undertake an assessment
of groundwater conditions to support the engineering design.
Hydrogeological Environment
The cutting or Parkway section was excavated within the
upper part of the Botany Sands, which here comprises dune
sands up to 15 metres thick. Beneath the dune sands lie
alluvial and estuarine deposits, with variable proportions
of soft peat and clay. The sands form a highly productive
aquifer, from which industrial and irrigation abstraction
is made. The unconfined aquifer is recharged by local precipitation
excess and through-flow from up-gradient recharge zones,
such as Moore Park.
Scope
C. M. Jewell & Associates Pty Ltd initially undertook
a desktop analysis of the problem. Groundwater modelling
at a regional scale was then undertaken by Noel Merrick
of the University of Technology, Sydney, using a refinement
of a finite element model originally developed for research
purposes. Concurrently, drilling and pump testing for the
derivation of aquifer properties, and a reinjection trial,
were undertaken. The need for high model resolution led
to the development of a local finite difference groundwater
flow model capable of simulating conditions close to the
Parkway and the Dacey-Todman tunnel.
The final report included recommendations for dewatering
system design, a groundwater level and quality monitoring
program, and a contingency reinjection system design. 
|
Projects