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Dredging an 80-Foot Secant Shaft With Zero Dewatering | Flatiron Construction Case Study
Georgetown Wet Weather Treatment Station
Barred from dewatering the shaft and unable to reach depth with conventional equipment, Boulder-based Flatiron suspended a 6-inch EDDY Excavator Dredge Pump Attachment from a single crane, dredging a 100-ft-diameter secant shaft more than 80 feet down at up to triple clamshell production.
CASE STUDY
A customizable EDDY Excavator Dredge Pump Attachment delivered a creative solution for a wet weather treatment station.
Taking advantage of the diversity of a modular excavator dredge pump attachment and a water-jetting ring, Boulder-based Flatiron Construction was able to creatively design and build an equalization basin at depths of more than 80 feet to dredge a wet weather treatment station in historic Georgetown, Colorado.
EXCAVATION DEPTH REACHED — WITH NO DEWATERING
CONTINUOUS PRODUCTION — UP TO 3× CLAMSHELL OUTPUT
HANDLED THE ENTIRE APPARATUS — INSTEAD OF TWO
The Challenge.
As part of a large wet weather treatment station, the project required the construction of an equalization basin. The basin was formed by installing 104 individual secant shafts side by side in a circle, creating a single 100-foot-diameter shaft — which then had to be excavated to a depth of more than 80 feet, removing roughly 25,000 cubic yards of material.
Several constraints made conventional methods unworkable. The contract documents did not allow the shaft to be dewatered during excavation, yet the water table sat only about 10 feet below the surface. Standard excavation equipment could not reach the 80-foot depth, and the onsite crane could not support the clamshell-type excavation typically deployed for similar applications.
The Solution.
The dredge pump ran on three lines — power, water source, and discharge — all supported at depth by the pile-driving-lead framework, which doubled as a giant depth-measurement tool. Key choices that made it work:
- 6-inch hydraulic-powered EDDY Pump Excavator Dredge Pump Attachment
- Water Jetting Ring — high-pressure nozzles that break up consolidated material and feed more of it to the pump
- Crane-suspended deployment on pile-driving leads, which also served as a live depth gauge
- Hydraulic — not electric — power, so the pump and cord could be submerged with no risk of electric shock
- Closed-loop water source: discharge water was recycled back into the secant shaft, introducing no outside water
“The dredge pump would produce approximately 150 cubic yards per hour regardless of the excavation depth — double clamshell production at shallow depths, and triple clamshell production at deep depths.”
KEN HORTON · CONSTRUCTION MANAGER, FLATIRON CONSTRUCTION
The Power Of EDDY Pump Technology
The EDDY Pump Excavator Dredge Pump Attachment is a state-of-the-art dredging system that pins into an excavator’s existing bucket linkage and runs off its auxiliary hydraulics. When conditions demand more power and production, a Hydraulic Power Unit (HPU) drives it instead.
At its core is the patented EDDY Pump — not a centrifugal, positive-displacement, or vortex pump, but a geometrically designed spinning rotor that harnesses the principles of a tornado to create a synchronized EDDY current. The result: it moves a higher percentage of solids with less water, outperforming conventional pumps in the most difficult applications.
Using a cutterhead or high-pressure water-jetting rings depending on the job, the system can pump slurries up to 4,500 feet without a booster pump. Every EDDY Pump suction dredge and excavator cutterhead is powered by field-proven, U.S.A.-built industrial slurry pumps.
The Results: 150 YD³/HR at Triple Clamshell Output
One piece of equipment, deployed creatively, cleared every constraint the project faced — faster, cleaner, and at lower cost than conventional methods.
- Reached the full 80-foot depth without dewatering the shaft
- ~150 yd³/hr of continuous production — double clamshell output at shallow depth, triple at deep depth
- One crane instead of two, saving significant cost on the project
- No outside water source required — the jet-pump water was recycled on site
- Continuous spoil delivery straight to the stockpile / loadout area
- Crane positioned away from the spoil pile, improving site mobility — and a far cleaner operation than clamshell excavation
About Flatiron Construction
Flatiron Construction develops innovative solutions to build critical infrastructure and landmark projects — roads, bridges, rail, airports, dams, industrial, water, and underground works, from common to complex large-scale jobs. Founded in Boulder, Colorado, in 1947, Flatiron now operates across the U.S. and Canada and is a subsidiary of German-based HOCHTIEF, one of the world’s largest international construction service providers.
About Eddy Pump Corporation
Founded in 1984, EDDY Pump Corporation delivers breakthrough technology and service to industries including the U.S. Navy, oil & gas, mining, wastewater, paper/pulp, dredging, fracking, and chemical. At its core is the patented EDDY Pump — not a centrifugal, vortex, or positive-displacement pump, but a geometrically designed spinning rotor that harnesses the power of a tornado into fluid dynamics, handling material once deemed impossible or cost-prohibitive.