Gold was discovered in the Bendigo area of Victoria in 1851
(Willman and Wilkinson, 1993), and all the early gold mining of
any note involved washing (puddling) the gold out of the regolith
or alluvium. The waste material from this process was a
semi-fluid mixture of rock debris, soil and water, referred to as
`sludge'. Puddling machines were gradually introduced to speed
up the puddling process (Cole, 1994), and by 1855 an estimated
2000 machines were in the district (Anderson, 1978). In 1859 it
was estimated that approximately 2 293 000 m3 of material was
puddled annually by the machines on the eastern side of the
goldfield, whose waste drained into Bendigo Creek and its
tributary gullies. It was also estimated that after the gold was
removed, approximately one-quarter of the residue/sludge
consisted of the heavier, coarse-grained material which settled out
fairly quickly, while the remainder, approximately 1 720 000 m3,
was the fine-grained material which flowed downstream for some
distance (VPP, 1859 - 60). From these figures it can be assumed
that for the ten years during which this volume of puddling was
maintained (1854 - 1864) over 5 700 000 m3 of gravels and sands
and 17 200 000 m3 of fine-grained sludge had been discharged
into and around Bendigo Creek. This was enough to cover an
area of over 400 km2 to a depth of 5 cm. By 1859 the problems associated with the sheer volume of
sludge being discharged were such that a Royal Commission was
appointed to `Enquire into the Best Method of Removing the
Sludge from the Gold Fields' (VPP, 1859 - 60). The goldfields
referred to were those in the Bendigo area around the township of
Sandhurst (now known as Bendigo). The Report of the
Commission (VPP, 1859 - 60) stated that: `... inspection of the
country bordering upon the course of the Bendigo Creek, to a
distance of about fifty miles from Sandhurst . . . ' had revealed
that the sludge had ' . . . filled up watercourses and flooded
pasture lands . . . '. It also noted that ' . . . even on the plains,
thirty or forty miles away from Sandhurst, where the sludge flows
thin, and is relieved from its heavier particles, we found it baked
into a perfect concrete, and in thicknesses varying up to two feet
or more . . . '. The italics were used for emphasis in the original
text. As it was considered unlikely that the physical evidence for
such widespread inundation would have disappeared completely
over the intervening 130 or so years, a project was initiated to
locate any evidence of the inundation in the current landscape. If
such evidence were to be found, then an estimate could be made
of both its extent and its effects on the topography, drainage, and
land-use of the inundated area. Extensive field work has
determined that over 700 km2 to the north of Bendigo was
inundated by the sludge. The area has not been uniformly
covered, but has occasional `inliers' which have obviously
escaped inundation by being slightly higher than the surrounding
areas. Today the sludge is readily identified as a very
fine-grained, hard-setting, concrete-like `capping' overlying a
well-developed, well-structured, pedal horizon, or in some
instances, the gravels and sands of a creek bed. The thickness of
the sludge capping varies between a few centimetres and three
metres (Peterson, 1996). The buried topography was gently
undulating, in direct contrast with the almost unnatural flatness of