Blockage of a critical 5-inch overflow pipe beneath a large artificial lake at Dospat Dam, Bulgaria, posed extreme danger to dam wall integrity — risking catastrophic failure. 

Over 50 years of hardened sediment and debris had accumulated, and drainage was reduced to a trickle. Construction of a new removal conduit proved unfeasible. 

The remote setting also eliminated heavy cleaning equipment from consideration. And the 460-foot line descended over a 2.5% grade from 157 feet beneath the dam wall through four tight bends to its terminus — rendering clear-out extremely difficult. 

That’s when Double D Engineering Ltd., European specialists in industrial cleaning technologies and services, stepped in with an “outside the box” idea. 

“Economics and facility condition forced us to work with the existing pipeline,” says Dimiter Dimitrov, company manager. “So we opted for a compact, portable water jet solution.” 

Portability and power

Representing the Russian company Zevs Technologies Ltd., Double D chose the powerful, compact and maneuverable J-3080 gas-powered water jet from General Pipe Cleaners. 

Part of General’s popular Jet-Set line, the high-flow device is perfect for clearing larger, more difficult lines of grease, sediment, ice and other “soft” blockages. A 20 hp Honda engine with electric start provides an 8 gpm flow rate at 3,000 psi, without risking pump damage if water supply can’t match pump demand. A 12-gallon frame-mounted buffer tank provides enhanced safety margins and extends operating time. 

“We’ve specialized in industrial cleaning since 1998, and this was our first project with the J-3080,” Dimitrov adds. “We were enormously pleased with its portability, power and performance.” 

General’s gas- and electric-powered water jets also feature on-demand Vibra-pulse for greater nozzle thrust around tight bends and down long lines. Dimitrov especially liked that feature. 

“The steel overflow line featured four turns over its length,” he says. “And Vibra-pulse technology helped ensure thorough removal of the built-up sediment and debris.” 

Dimitrov also appreciated the J-3080’s positive lock braking system and heavy-duty frame with four 13-inch "flat-free" foam-core tires. 

“Our J-3080 often sat in precarious locations on the job site at Dospat,” Dimitrov says. “And its stability, tough construction and reliable wheel brakes really kept the machine solidly positioned.” 

Standard J-3080 safety features include a thermal relief valve to protect the pump from heat damage, as well as a backflow check valve and inlet filter. It comes complete with toolbox and spray wand with trigger. 

Fresh approach yields results

Partially tapping lake water 130 feet away — and using two hoses, three high-performance nozzles, and two standard nozzles — Double D cleared the blockage in three steps over roughly 12 hours and three days: 

• Phase 1 — About 295 feet were cleaned from the lower end of the pipe with all three high-performance nozzles. Total work time: five hours, 15 minutes.
• Phase 2 — Another 75.5 feet from the lower end were subsequently cleaned with the three high-performance nozzles. By then, however, the J-3080 had hit maximum reach. Total work time: five hours, 30 minutes.
• Phase 3 — Double D then repositioned the J-3080 to clean 164 feet from the pipeline’s upper end. Total work time: one hour, 24 minutes. 

Conditions on the final project leg proved especially hazardous. Personnel had to descend to a gallery about 164 feet below lake water level. And they risked catastrophic flooding from large chunks of loosened sediment blocking the clean downstream end. But by employing smaller jet nozzles — and gradually removing the blockage from the center out — workers successfully completed the job. 

Sediment and debris blockages plague thousands of dam, waterway and waste treatment pipelines. But not all are accessible to larger trailer-mounted water jets. Nor is larger wheeled equipment always economical to employ. 

But Double D blended innovative removal techniques with a compact, powerful General water jet for a creative, yet effective, solution. 

“Everything worked beautifully,” Dimitrov says. “We could not have achieved those positive results without our J-3080.”

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