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The Marion 7820 Walking Dragline is a monster of a machine. Picture a crane on steroids attached to a truncated ocean tanker. When the dragline's boom is fully extended, the Marion wouldn't fit into Pro Player Stadium. It weighs more than four million pounds and rests on two 52-foot-long treaded shoes. This industrial titan may be mobile, but agile it is not; to drive this beast two miles takes twenty hours.
When fully operational the machine can draw on ten separate motors offering a total of 110,000 horsepower. The juice to run it comes from an extension cord thousands of yards long attached in this case to its own Florida Power & Light electrical substation. It's a special perk for the machine's owner, White Rock Quarries, which carries a monthly electric bill of more than $100,000, befitting a company that ranks number seven on the list of the nation's top stone-crushing operations.
To truly appreciate what the Marion can do, one must see it at work. Hanging from the boom is a huge metal bucket that could easily hold a pickup truck. The bucket swings at the end of giant chains. An operator sits in an imposing throne of a chair before a huge window. Using a system of levers, he repeatedly drops the bucket into the submerged water of the quarry and retrieves as much as two dump-truck loads of dripping, crushed rock. The dragline swings to the shoreline and the bucket deposits its cargo into an ever-expanding brownish mound. The rock is precrushed with dynamite. Working 24 hours a day, four days a week, the dragline excavates about 100 acres per year. One acre yields about 125,000 tons of rock.
Prior to being shipped to Miami in 1995, the Marion pulled coal, the original lifeblood of industrialism, from the strip mines of Kentucky. Today it feasts on limestone. The South Florida rock bonds exceptionally well with cement and has become a cheap, easy, high-quality material with which to build roads and houses.
All of Miami-Dade County's limestone and half of Florida's supply currently comes from one 89-square-mile area in Northwest Miami-Dade. Bordered by Krome Avenue on the west, the Dade-Broward line on the north, and Florida's Turnpike on the east, on maps the 49,700-acre tract looks a little like a perched bird with a beak that overlaps I-75 and a tail that touches Kendall Drive. The rock miners own 26,600 acres of this territory. Every year the area produces about 35 to 40 million tons of rock, turning roughly 300 acres into artificial lakes. (Like most of the county, here the water table is directly below the soil. As soon as the muck and rock are removed, the aquifer is exposed and lakes form.)
Dominated by four major rock miners and six smaller outfits, the region has become known over the past ten years as the Lake Belt. While still mainly just a vision for planners and miners, machines such as the Marion 7820 are quickly digging the Lake Belt into reality. At the current pace, by 2050 the Lake Belt will be mined out, transformed into a latticework of interconnecting water reservoirs, leaving South Florida with a new ecosystem and the need for an alternative source of limestone.
But like the open coal pits that litter Appalachia, poisoning its rivers and streams, the operation of this dragline might bring severe environmental consequences to Miami-Dade County that could cost future taxpayers a small fortune to fix. To retrieve the limestone, vital wetlands that filter pollutants out of the water, help flood control, and provide important habitat to a variety of endangered wildlife must be removed. Of perhaps even greater concern is that just a few miles from the quarry are two of the county's last pockets of clean drinking water: the west and northwest wellfields.
The vision for the Lake Belt articulated in government documents sounds much like a Chinese tea that promises to remedy everything from infertility to toothaches. The Florida legislature, the South Florida Water Management District, and the Army Corps of Engineers seem to believe the Lake Belt can enhance the water supply, maximize efficient recovery of limestone, promote the social and economic welfare of the community, create a sportsman's paradise, halt urban sprawl, protect the environment, eliminate nonnative plants, revive wetlands, and help restore the Everglades.
Not everyone is buying the magic cure. Critics argue the Lake Belt will do little more than temporarily mask the ill effects of rock mining. Most environmentalists reject the Lake Belt plan as potentially dangerous for the surrounding ecosystem and the water supply. They are not alone. Miami-Dade County Water and Sewer Authority, Everglades National Park, and the Miccosukee Tribe of Indians, to name only a few, have responded critically to a draft environmental study of the plan. Finally some homeowners are fearful that blasts from explosives used to crush the rock will crack their houses.
Despite the growing show of skepticism, the Lake Belt's journey into acceptance until now has been remarkably smooth. Its success over the past ten years can be attributed to political goodwill purchased with an avalanche of rock-miner cash, a toothless regulatory system, a split among environmentalists, and Paul Larsen.