A Massive Cover-up

In the second half of the 19th century, David Mitchell was one of Melbourne’s best-known builders. Riding the city’s gold-fuelled growth, the former mason’s apprentice was responsible for many of its new structures, including the Presbyterian Ladies’ College and the Royal Exhibition Building. In 1874, perhaps in a bout of self-congratulation, Mitchell decided to take his teenage daughter Helen Porter Mitchell on a tour of his latest project: the “decorated Gothic” Scots’ Church on Collins Street. The highlight of their visit was a trip to the top of the 64-metre spire, which required ascent in a barrow. It is nice to think the excursion had father and daughter swaying above Marvellous Melbourne – his top hat pulled tight, her parasol fringe fluttering – and that the experience may have prompted Miss Mitchell to follow her “higher calling” as a singer. But the outing took place at least 10 years before she reinvented herself as Nellie Melba; back then her father was the household name. Mitchell soon entered the lime and cement game, so that he could put the squeeze on those monopolising Geelong limeburners. In 1878 he established the Cave Hill Limestone Quarry, on Melbourne’s outer-eastern flanks, and it grew quickly to feature steam-powered cranes, rail links and 24-hour limeburning facilities. And, as the city expanded, Mitchell’s quarry deepened – providing the essential mineral for mortar and other construction materials. The Mitchell family only sold the Cave Hill concern in 2002, and at the end of 2015, 99 years after Mitchell’s death, it ceased operations entirely. But to pack up a quarry is no easy task. Three years on, commuters on the final stretch of the Lilydale train line still pass the site’s processing plant: a tangle of lime-caked corrugated-iron sheds that resemble the finest in Romanian heavy industry circa 1950. There was a time when, if you looked at the right moment while on the train, you could see the incendiary glow coming from the round-the-clock kilns. Now, as we tour the Cave Hill site on the sort of winter’s day that makes your ears ache, the space holds no residual heat, and moss has crept into corners that would once have been blasted dry.

Our tour is led by Maxwell Shifman, chief operating officer of Intrapac Property, which is part of a consortium that is filling the quarry before it commences construction of a new housing development. Even when wearing the obligatory hard hat and hi-vis vest, Shifman is an incongruity: he’s sharply dressed and fresh faced, while other workers on the site wear KingGee and have a lightly limed complexion. By Shifman’s measure, Cave Hill is “the biggest single urban-infill site in Australia” (as opposed to a greenfield site). Size is a hard thing to convey; suffice to say, if you wanted to nick the Melbourne Cricket Ground and bury it, including its light towers, this quarry would be more than fitting. And yet the quarry makes up less than one-sixth of the development area. While we travel around the site surrounding the quarry, Shifman points out historical landmarks that he plans to retain in the precinct’s final design. In fact, he is as versed in the site’s heritage as in its geotechnical specifications, most notably the legacy of Mitchell, who “was constantly innovating, constantly trying new things out, new methodologies, improving the extraction process”. As Shifman explains, Mitchell even diversified within the property. One of his other ventures on the site is remembered by a sturdy Victorian-era brick structure: a smokehouse that was “the official supplier of bacon to the government”. More impressive is the limestone-processing plant, accessible only with the help of a workman called Bazza, who, after trying numerous keys on a lime-caked padlock, achieves ingress by way of an angle grinder. Bazza worked at the quarry when it was still active, and has stayed on for the transition. “So Bazza’s confused,” says Shifman. “One minute he’s taking stuff out of the hole …” Bazza leads us to the nine kilns located inside one of the larger corrugated-iron sheds: a massive space known as “the tunnel”. As Shifman says, “it’s like a cathedral – really quite spectacular”. At one end of the tunnel are remnants of the spur rail track that connected to the Melbourne line. And at the other splays the expansive maw of Cave Hill quarry. From the quarry’s northern lip we peer down 120 metres. In the fog-softened distance, below darting eastern spinebills and hardy vegetation clinging to the pit’s scarred edges, are yellow trucks the size of houses taking part in a revving, clunking, beeping dance. As we watch the lumbering activity below, Shifman details how one goes about filling a 9-million-cubic-metre hole. “We’ve devised an engineering methodology that requires us to place the material in certain layers and test it in certain ways …” Shifman then measures the comprehension of his audience and changes tack: “Simplistically, we are picking things up, putting them in a big yellow truck, driving them down and squashing them all.” A site worker who has accompanied us points to a large vehicle that has what looks like a monster’s hair roller tacked to its front, and helpfully adds, “That’s doing the squashing.” At the lowest point of the hole sits a pooling “sump” of water, which is being pumped out at a rate of 1.8 million litres a day. Yes, this is big stats territory. “Disappearing” the quarry using the mille-feuille strategy will involve 400,000 truckloads carrying 20 million tonnes of fill, and take about five years. And as to what the quarry is being filled with? Shifman explains that some 40 hectares of the surrounding area (also part of the development) are covered by “overburden”: useless rock that also came out of the hole. “So when they extracted the material, not everything went offsite. Only about 25 per cent was the actual limestone.” What’s more, Cave Hill was indeed a hill when David Mitchell began digging, and there is enough overburden available to reach a level surface. So the quarry will not be employed to solve Australia’s refuse woes. And when asked whether a request to “disappear” a package of incriminating documents would be considered, Shifman does not blink. “Every load of material that goes down has to be geotechnically suitable, and is supervised by a geotechnical engineer full time. ’Cos we need to make sure it’s safe and stable at the end.” While another big yellow truck circles slowly down into the pit, Shifman sums up the process of undoing Mitchell’s 140-year-old enterprise: “We are literally putting back what came out.”