The Everglades tends to make national news for one of two reasons: a hurricane, or someone hauling an absurdly long python out of it. So I doubt many of you caught the press release the Army Corps of Engineers put out on Nov. 5. It was about a wall, and you’ll never get to see that wall, because it’s underground.<\/p>\n
Still, it’s arguably one of the more important things being built in South Florida right now. The Corps says<\/a> the foundation and cutoff wall on the Everglades Agricultural Area Reservoir, usually shortened to the EAA Reservoir, are now 50 percent complete. That works out to about eight miles finished out of a 15.84-mile line, and the job’s running 34 days ahead of schedule.<\/p>\n Then there’s the machinery. The Corps says three draglines are working on the project right now, and one of them is a fairly unusual Dutch-built machine. We’ll get to that.<\/p>\n A cutoff wall is basically a barrier buried in the ground beneath a dam. Water pushes against a dam, but it also goes looking for a way underneath, and the wall’s there to block the route.<\/p>\n So why should anyone care about a little water sneaking under a dam?<\/p>\n Because this reservoir’s going on top of limestone, and the Corps knows how that can go. Wolf Creek Dam in Kentucky sits on limestone and spent decades leaking through the bedrock, and the fix was a second, deeper cutoff wall built while the lake was kept low. We also covered a channel carved under a 111-year-old lock and dam in North Carolina<\/a> a few days ago. Water’s persistent like that.<\/p>\n Fixing this kind of problem after the fact is miserable. The Corps’ Pittsburgh District spent seven years putting a 1,500-foot cutoff wall into East Branch Dam<\/a> in Pennsylvania, and it had to lower the lake and dig 150 separate panels to do it. The Florida wall goes 35 to 60 feet deep, compared with East Branch’s 250, according to Forgen-Odin, the joint venture building it. It’s also going in before there’s a dam on top to work around, which strikes me as the smart order to do things in.<\/p>\n It’s a different kind of wall, too. Forgen-Odin describes it as a slurry wall made from slag cement, regular cement and bentonite clay. Walls like that generally start as a narrow trench held open by the wet mix, which then hardens in place, so picture a very long, very skinny strip of stiff underground mud.<\/p>\n If you go through older documents, you’ll also find this wall listed at 15.3 miles and 15.75 miles. I’m going with the Corps’ latest figure, 15.84. The rest of the dam’s 17.75-mile length falls under a different contract, which has about two miles of cutoff wall of its own.<\/p>\n I did some math of my own here, so take it for what it’s worth. The Corps awarded this contract about four years ago, and it’s due to wrap up in March 2028, roughly 16 months from now. So the first half took close to four years and the second half gets a little over one.<\/p>\n That sounds worse than it probably is. The contract also covers clearing the land, digging out muck, blasting and preparing the foundation, and I’d assume a lot of the early years went to that. The Corps says it’s pulled the finish date in by 15 months, too. It hasn’t said whether those 34 days ahead are measured against the old schedule or the new one, and I’d genuinely like to know.<\/p>\n All of this is tied to a bigger deadline. The Army and Florida struck a deal last year to finish the reservoir by 2029, when the original target was 2034. “Delivering it five years early is what happens when we build infrastructure, not paperwork,” said Lee Forsgren, the senior official performing the duties of the assistant secretary of the Army for civil works. It’s a pretty good line, although a $2.87 billion dam contract still generates a fair bit of paperwork.<\/p>\n It’s easy to read the Corps’ release and assume the dragline’s digging the wall. As far as I can tell, it isn’t. North American Mining, which runs the draglines, says its job is moving more than 25 million tons of earth for the 17.75-mile dam. That’s a separate contract, held by Thalle Construction.<\/p>\n A dragline is essentially a crane that digs. It hangs a huge bucket from a long boom on steel cables, drops it out in front of the machine, then reels it back across the ground full of dirt.<\/p>\n The one getting all the attention is an Mteck 2100E, made by a Dutch crane builder. North American Mining lists it at 1,618,000 pounds, or 809 tons, with a 180-foot boom and a 20- to 22-cubic-yard bucket. That’s a pretty serious piece of equipment, and Mteck says its draglines run 18 to 22 hours a day, seven days a week in Florida. They kind of have to. The Corps counts 33.2 million cubic yards of excavation on this project, which would take about 1.6 million scoops if a single 21-yard bucket did it all.<\/p>\n Before you get too impressed, mining has much bigger toys. Caterpillar’s 8750 dragline works at up to 15.9 million pounds, against 1,618,000 for the 2100E. So unusual doesn’t mean huge here.<\/p>\n Fewer than you’d think, though the exact count depends on who you ask. Mteck’s own website<\/a> says four 2100E units have been delivered worldwide, and Heavy Lift News reported on Oct. 12 that the fourth was about to set off for Florida. It would join one 2100E and two smaller 825E draglines already on the Everglades job.<\/p>\n Those three line up with the three draglines the Corps says are running now. I can’t find anything confirming the fourth 2100E has reached the site yet. Either way, you’re not likely to see one of these at your local quarry.<\/p>\n You might picture a reservoir as a big hole full of water. This one’s closer to an above-ground pool, if your above-ground pool covered 10,500 acres. The Corps describes<\/a> a 37-foot embankment holding water 23 feet deep, and the design calls for more than 78 billion gallons.<\/p>\n At 37 feet, this dam’s a lot shorter than the 390-foot earthen dam in Colorado<\/a> and the 402-foot earth dam in New Mexico<\/a> we’ve covered recently. It makes up for that by running 17.75 miles.<\/p>\n Which brings me to a couple of things in the Corps’ fact list that I’d read carefully. It calls the project nearly seven stories tall, and that seems like a stretch for a 37-foot embankment. Thalle puts it at 34 to 38 feet above grade. Maybe the seven stories includes the foundation, but the release doesn’t say.<\/p>\n The 17,000 acres, the 26.5 square miles and the comparison to Manhattan also include a 6,500-acre treatment wetland next door. The reservoir itself is about 16 square miles. And the 725,000 dump truck loads work out to about 46 cubic yards each, so these aren’t the dump trucks you get stuck behind on I-95.<\/p>\n Lake Okeechobee gets too full, basically. When that happens, water gets sent out toward both coasts, where the Corps says it does real damage to the estuaries, while the Everglades to the south doesn’t get enough. The reservoir sits 27 miles south of the lake, and it’s meant to catch that water and hold on to it until it can head south.<\/p>\n Before it goes anywhere, the water runs through that treatment wetland. The Corps expects the whole setup to send as much as 470 billion gallons of clean water a year to the Everglades and Florida Bay. The South Florida Water Management District is handling the pump stations and the Blue Shanty Flow Way, which moves the water on toward the park and the bay. That seems like a fair split, since a giant pool isn’t much use without a way to fill it.<\/p>\n None of this holds any water yet, of course. The Corps says the foundation and cutoff wall are scheduled to finish in March 2028, and Thalle’s dam contract is due by December 2029.<\/p>\n","protected":false},"excerpt":{"rendered":" The Everglades tends to make national news for one of two reasons: a hurricane, or someone hauling an absurdly long … <\/p>\nSo what is a cutoff wall?<\/h2>\n
So where does the dragline come in?<\/h2>\n
How many 2100Es are out there?<\/h2>\n
It’s basically a giant above-ground pool<\/h2>\n
So why build any of this?<\/h2>\n