Dredging World News Blog

SRS Crisafulli Explores Dredging and Hydropower

Posted by Elizabeth Kaiser on Wed, Jan 25, 2012 @ 08:01 AM

By Elizabeth Kaiser, SRS Crisafulli Marketing Manager

Energy production and consumption worldwide is influenced by many factors.  Resource availability, economic activity, population growth and environmental regulations, for instance, all affect the types of energy production that may be available to consumers.   One of the cheapest methods of energy production is hydroelectric power.

Last spring’s press release by the U.S. Department of the Interior, Departments of Energy and Interior Announce $26.6 Million in Funding to Develop Advanced Hydropower Technologies, announced  “funding for research and development projects to advance hydropower technology, including pumped storage hydropower.”  Hydropower is a sustainable and clean power generating process.  “These funding opportunities will help unlock innovative approaches to hydropower development that emphasize sustainable, clean power generation while reducing environmental impacts.” 

What is the hydropower process?  In short, falling water is passed through a hydroelectric generator to produce electricity. Another hydropower process involves what is called “pumped-storage”. As explained by the Tennessee Valley Authority, “A pumped-storage plant uses two reservoirs, one located at a much higher elevation than the other.  During periods of low demand for electricity, such as nights and weekends, energy is stored by reversing the turbines and pumping water from the lower to the upper reservoir.”

Watch this YouTube video "Hydroelectic Power - How it Works"

 

How is dredging part of this scenario?  The most serious technical problem for hydroelectric dams is accumulation of silt which reduces the water storage capacity of the dam.   Reduced storage capacity limits both electricity generation and the availability of fresh water for downstream uses.  Periodic maintenance dredging removes silt deposits from the dam reservoir and restores water storage capacity, thereby allowing the hydroelectric dam to function more effectively. Periodic dredging can reduce potential negative impacts on fresh water availability without interrupting energy production.

 

Want to learn more about hydroelectric dam dredging?  Contact us.

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Topics: Dredges, crisafulli, dredge, dredging, srs crisafulli, dredging abrasive materials, lagoon dredges, dredging system, dredging and pumps, lagoon, rotomite 6000c, Hydraulic dredging

Proactive Dredging: A Little Now or a Lot Later

Posted by Elizabeth Kaiser on Wed, Oct 19, 2011 @ 08:10 AM

By Isaiah Helm, Applications Engineer, SRS Crisafulli

 

If public works departments had a list of fun things to do, dredging sediment out of holding ponds would not be on it.  It’s like cleaning the shower in your bathroom.  Whether you make it a frequent quick job or an occasional laborious task, time and effort must be set aside to maintain a fixture that is as critical as it is uninteresting.  This is the scenario that played out for Georgia’s Cobb County-Marietta Water Authority (CCMWA) during the summer and fall of 2010, as reported in Public Works Magazine

CCMWA had two water treatment plants and a 25 million gallon reservoir in need of upgrade to meet the EPA’s Stage 2 Disinfectant and Disinfection Byproduct Rule of 2006.  During the upgrade, one plant would be running, one shut down.  The reservoir had to be at full capacity to do this.  Unfortunately, it hadn’t been dredged since 1978 and was half full of sludge.  

 proactive dredging resized 600The reservoir was restored to its original 14-foot depth
within six months.  (Photo Credit:  Public Works Magazine)

Timing of all the different upgrade stages coupled with the EPA deadline meant the reservoir had to be cleaned out in six months.  (The dredging had originally been scheduled to take place 2013-2014.) 

In other words, the CCMWA had to make up over 30 years of maintenance in 6 months (that would be one nasty shower!).  The result: increased scale, decreased competition, and ultimately an increased cost.  The amount of dewatering equipment doubled.  Four mobile belt presses and four recessed chamber presses were used.  Fifty trucks made four 45-mile round trips per day.  Bidding on the project was limited to the few large contractors who were even capable of completing the project.  There were five bidders and all five of them listed the same two companies as their subcontractors.  Total cost to dredge the reservoir and perform maintenance on the banks and sluice gates totaled just over $4 million.

The World Dredging Mining & Construction Journal [1] contains a version of the article authored by Steve Gibbs.  It goes on to discuss some observations from the project:

One of the lessons learned by CCMWA is the need for regular dredging of the reservoir.  One benefit of regular dredging is economics – greater capacity in the reservoir reduces the amount of pumping necessary to bring water from the Chattahoochee, thus saving electrical costs.  Also, doing a smaller dredging project every five years or so will eliminate the need to do a massive project such as the one just completed.

A deeper, cleaner reservoir will allow suspended solids to settle out better, which will enhance treatment efficiency.  The reservoir will also have ample capacity while the treatment plants are in their construction phase.

“This (the reservoir dredging project) will decrease the potential for water quality problems or process issues at our treatment plants,” said Ginn (CCMWA process engineer). “It’s a very good proactive preventive maintenance step.”

There you have it.  Proactive dredging of sludge-collecting ponds really does make life easier in the end.  It also increases the options:

  • Put out a request for bids on that smaller dredging project every five years

  • Contract with a dredging company to clean out the pond every five years

  • Rent dredging and dewatering equipment directly and eliminate the middleman

  • Purchase an automated or remote dredging and dewatering system and have it permanently installed for complete self-sufficiency

At least it’s something to think about while you’re cleaning your shower tonight.

 

[1] World Dredging Mining & Construction Journal, “Proper Planning for a Perfect Project” (Volume 46, Nos. 11/12, Page 16)

 

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Dredging Abrasive Materials? Learn about SRS Crisafulli’s New Dredge

Posted by Elizabeth Kaiser on Fri, Apr 29, 2011 @ 06:04 AM

dredging abrasive materials rotomite 6000cThe Rotomite-6000-C, SRS Crisafulli’s newest self-propelled dredge, broadens the Rotomite-6000’s capabilities to include removal of highly abrasive materials. The Rotomite-6000-C also increases the customer’s return on investment (ROI) by cutting sludge management costs, increasing user productivity, and enhancing the unit’s maneuverability for the removal of toxic and non-toxic solids.

The new design offers capabilities that will benefit industrial companies, including; chemical companies, food processing plants, domestic and international construction and contracting companies, oil, mining and refining companies, petrochemical plants and refiners, and coal fired utility companies. Municipalities, County, Regional and Federal agencies, as well as lake associations, and landfill operators, will be able to use the Rotomite-6000-C in many applications. In addition, the Rotomite-6000-C helps companies comply with domestic and foreign mandates by ensuring manufacturing by-products are contained safely in order to prevent contamination of drinking water.

This versatile, self-propelled design is a horizontal auger, hydraulic dredge that can work in odd-shaped areas where a cable dredge unit cannot go. It can remove, pump and discharge dredged solids in water/solids slurries through a floating discharge pipe to disposal sites up to 5,000 feet away, or more when a booster pump is used.

The Rotomite-6000-C is 40 feet long by 9.5 feet wide, and is easily transported by truck.  Its 255-horse power motor and new propulsion system provide increased production and propulsion thrust. It will dredge most soft or abrasive materials, including alum and lime sludges, bentonite, biosolids, bottom ash, clay, coal fines, fly ash, gypsum, mine tailings and slimes, mill scale, mud, pigmentation sediments, industrial and municipal wastes, pulp and paper residuals, peat, oil API sludge, sediments silt and sand.


Capabilities include:

  • Dredging depth of 23 feet standard (up to 30 feet optional)
  • Up to 235 cubic yards of sludge solids produced hourly
  • A discharge volume of up to 3,400 gallons per minute @ 180’ TDH (water)
  • A dredging speed of up to 25 feet per minute
  • A dredging cut up to 8.5 feet wide
  • A cutterhead torque of 11,500 inch/lbs.
  • A draft of 30 inches

The self-propulsion feature provides increased maneuverability, more forward and reverse speeds and a 72-horse power hydraulic motor that powers a propeller system capable of 2,500 pounds of force. SRS Crisafulli’s exclusive Cobra cutterhead, which provides 11,000 inch-pounds of digging torque and up to 235 cubic yards of sludge solids per hour, increases productivity. The hydraulic ladder results in enhanced downward force by providing 30,000 pounds of down pressure to dig into the settled solids materials more aggressively thereby increasing cutting capacity. An improved cab design provides operator safety and convenience features, including air conditioning and heating.


rotomite 6000c cta button resized 600

Topics: dredge, dredging, srs crisafulli, dredging abrasive materials, rotomite 6000c