Hydrogeological investigations in two pediplain basins at Lanyon, in the southern Tuggeranong Valley of the ACT, have identified areas which require remedial drainage for urban development. The rocks of the central Lanyon area consist of faulted Silurian dectic to rhyolitic ash-flow tuffs and interbedded sediments. Significant storage and transmission of groundwater occurs in well developed sets of open tensile fractures which formed in response to at least two reversals in regional principal stress directions during epeirogenic uplift and erosional unloading. Hydrogeological parameters measured in the field and laboratory included infiltration capacities, effective proosities, and hydraulic conductivities. From these data a predictive model for drain spacings is developed for all hydrogeological populations and for any given rainfall event. Constraints on locations of drains are also identified. It is recommended that a sufficient number of bores and piezometers be preserved after urban development to adequately assess changes to the groundwater regime.

Legacy product - no abstract available

Legacy product - no abstract available

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Legacy product - no abstract available

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Legacy product - no abstract available

J54/B1-95 Vertical scale: 30

22-2/J54-2/1-3

22-2/J54-2/1-3 Contour interval: 5