Tennessee Valley Authority, Duke Power Company and Other Utilities Use UMI Trash Skimmers

UMI Trash Skimmer clearing debris at Safe Harbor Water Power Corp. in Pennsylvania

UMI Trash Skimmer clearing debris at Safe Harbor Water Power Corp. in Pennsylvania


Offloading debris from UMI trash skimmer using shore conveyor

Offloading debris from UMI trash skimmer using shore conveyor

What do the Tennessee Valley Authority, Duke Power Company, and American Electric Power Co. have in common? They all use a UMI trash skimmer to solve their floating debris problems.

Many hydropower companies are using a new technology for removing floating trash in reservoirs. The companies all say that the UMI trash skimmer is efficient, easy to maneuver, and transportable.

Floating trash and debris are a “fact of life” for operators at many hydroelectric facilities. Typically, seasonal ice thaws and rain generate surges in water volume. The resulting rush of water carries along anything that gets in its path, including trash and debris grounded on shallow flats and embankments during the low season. Each spring brings with it a massive volume of floating trash for the hydroelectric plant operator to contend with. At times, the accumulation can become a real nuisance. At worse, it can pose a hazard to smooth or continuous operations.

Current trash removal technologies such as automated trashrakes and conveyors, floating booms, and cranes with clamshells greatly improve upon traditional manual trash removal methods by saving time and labor. A new technology that several hydro plant operators are finding useful is a specially designed marine trash skimmer boat called the “TRASHCAT™”. Designed by United Marine International (UMI), the pontoon boat features an operator’s cab that straddles an open hull between the “skis” of the pontoon. This trash skimmer uses dual propellers to maneuver through the water. The “TrashCat” permits the operator to approach the trash problem from “the water side” upstream of the plant. Users of the trash skimmer boat agree that the design has many advantages, including mobility, stability, and the opportunity to reduce labor required to remove the debris.

Customizing the Design

The Tennessee Valley Authority (TVA) has used the “TRASHCAT™” successfully for several years. TVA learned about the boat from the cities of Chicago and Baltimore. These cities were among the first to have marine trash skimmers for removing floating debris from their inner harbors.

TVA representatives examined the design of the original model, identified some changes that could be incorporated to make the boat more practical for TVA use, and met with UMI who agreed to modify the design to fit TVA specifications. One feature that TVA officials required is a conversion capability that allows for weed removal. The “swing wings” on TVA’s boat can be equipped with reciprocating knives (that operate similar to a hedge trimmer) to cut out undesirable aquatic vegetation in recreational lake areas. After an initial operating period, TVA and UMI decided to strengthen the boat’s main skimmer head to withstand handling of large trees and water-soaked logs that continually find their way into TVA reservoirs. These logs, sometimes as large as 60 feet long and 2-1/2 feet in diameter, had to be cut up into 4- to 5-foot lengths by a chainsaw to be handled manually. Even then, a water-soaked oak section could weigh as much as 250 to 300 pounds – enough to bend and distort the original steel frame of the boat’s skimming head.

Improving on Progress

Safe Harbor Water Power Corporation of Conestoga, Pennsylvania, which operates the Safe Harbor hydroelectric facility on the Susquehanna River, also purchased a UMI “TRASHCAT™”. As part of its license agreement with the Federal Energy Regulatory Commission, Safe Harbor’s management agreed to research methods of collecting debris that floated from upstream locations on the river down to the plant. Prior to installing the “TRASHCAT™”, trash was sluiced past the dam.

Safe Harbor management, engineering, and operating staffs met with UMI engineers and drew up specifications for a design that would meet their needs. UMI agreed to make design changes to its “TRASHCAT™” including reinforcement of the skimmer head and raising the cab height to permit more efficient collection of large objects.

Marshall Kaiser, president of Safe Harbor, estimates the “TRASHCAT™” is in use seven months out of a year. As many as seven runs per day are required to remove debris from the river. Last season, the “TRASHCAT™” collected approximately 4,000 cubic yards of mixed debris!

During periods of ice cover or high river flow, when it is impossible to remove trash with the skimmer, the spillway gates are opened and debris is washed downstream.

Workers at Safe Harbor recently have undertaken several projects designed to protect the company’s investment in the “TRASHCAT™”. They upgraded the machine’s berthing and docking facilities, building a launch-recovery ramp and an adjacent dock for unloading the debris. They also modified warehouse storage facilities to provide shelter for the “TRASHCAT™” during the winter and spring runoff months when it is not operating.

In addition to the “TRASHCAT™”, Safe Harbor purchased supplementary equipment to form a complete trash collection and removal System. Their equipment includes:

A land based Shore Conveyor that receives debris being unloaded from the “TRASHCAT™” rear storage conveyor and transfers it to a dump truck for land disposal;

A portable power pack that provides hydraulic power to the conveyor; and

A tilt-deck trailer, used to launch and retrieve the “TRASHCAT™” in water and on land, as well as transport it from site to site.

Introducing Efficiency As Well as Cost Savings

Duke Power Company has acquired a UMI “TRASHCAT™”. Trash poses a problem at ten of Duke Power’s 27 reservoirs. For years staff at these projects had manually removed trash from trashrakes using hand rakes, hauled the debris to shore on barges, and shoveled the trash off the barges. “The “TRASHCAT™” has enabled us to reduce a six-man crew to two (an operator and assistant), thus freeing four men to do other jobs.” said Edgar Bell, Jr., manager of hydro production for Duke’s Lower Catawba Area. Duke Power is using the same boat at several reservoir sites.

Enhancing Public Relations

American Electric Power of Columbus, Ohio, purchased a UMI “TRASHCAT™” System for debris handling at its Appalachian Power hydro facility on Smith Mountain Lake, a 20,000-acre reservoir near Roanoke, Virginia. Because the area has 500 miles of highly developed residential and recreational shoreline, including coves and backwater areas, trash cleanup and removal is a high priority. Appalachian’s image as a “good neighbor” while ensuring greater hydropower generating efficiency.

Leasing to Save

According to Alan Mitchell, manager of Conowingo Hydro Station and Muddy Run Pumped Storage Plant on the Susquehanna River at Conowingo, Maryland has added a “TRASHCAT™” to its operations. Mitchell said officials there initially were attracted by the “TRASHCAT™” mobility, sturdy design, and navigability in both deep and shallow waters.

Mitchell estimates the “TRASHCAT™” will save his company $35,000 to $40,000 per year in operating expenses. (Conowingo previously had contracted with a trash-removal service.) Conowingo leases the “TRASHCAT™” through a third party, amortizing the purchase as an operating expense over a ten-year period.

Conclusions

Users of the “TRASHCAT™” marine trash skimmer agree that several features of the equipment are advantageous:

Transportability makes this technology useful for facilities with trash problems at both the plant site and at recreational lakes, or for facilities with multiple debris-infested reservoirs;

Unlike trashrakes, floating booms, or cranes with clamshells (solutions that can collect only the debris that floats into their paths), the “TrashCat” is mobile. The operator can go to the trash and remove large obstacles before they pose a threat to hydro operations; and

Cleaning up the debris, and thus the environment, promotes a “good neighbor” image.

Safe Harbor’s president Marshall Kaiser may have summed up the collective sentiment best: “I measure the success of a program by how little I hear about the problem once the program is under way. The “TRASHCAT™” must be working – I hardly ever hear about our trash problems any more!”

See article on TVA’s TRASHCAT™ from KnoxNews