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Moving millions of gallons: Virginia sewer project diverts 15 million gal. of wastewater a day to reline main sewer pipeline.

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The Holmes Run Sewer Improvement project in Alexandria, Va., had a lot of wastewater to move--15 million gal. a day to be exact--to reline the main sewer line that feeds through the area. To divert the wastewater, an 8500 ft. by-pass system was installed by Bridgeport, N.J.-based Godwin Pumps, using 18 Godwin Dri-Prime pumps to divert flow from the main sewer trunk so repairs could be performed.

The bypass system was developed by Greeley & Hansen, an environmental engineering firm specializing in water and wastewater engineering and utility management consulting headquartered in Chicago, Ill. Insituform Technologies, the pipe rehab and reline contractor on the project, began production at the site in mid-June, while crews from Godwin's Upper Marlboro, Md., branch installed 18 pump sets in nine days to divert flow from homes and businesses, using the sewer system to a 24 in. 8500 ft. temporary pipeline.

"The 36 in. pipeline that we're diverting is a gravity sewer pipeline," said Bud Nichols, Southeast regional manager at Godwin Pumps. "We're diverting the flow so Insituform can go in and rehab that 8000 ft. of gravity sewer pipe. We're catching the flow above the construction site, diverting it through temporary piping 8500 ft. and discharging it below their work area into the same 36 in. pipeline."

On the main pipeline, four primary pumps were installed using 12 in. Godwin Dri-Prime CD300M models. These units are equipped with 8.8 L six-cylinder Cat C9 diesel engines rated 275 hp at 1800 rpm, which drive Godwin centrifugal trash pumps offering flow capacities up to 6000 gpm. The pumps have a 200 ft. discharge head and can handle solids up to 3.75 in. in diameter.

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Jetting off the main 36 in. line are lateral pipelines to homes and businesses varying in sizes from 8 to 16 in. These water and sewer services were handled with 14 smaller Godwin Dri-Prime pumps, comprising a combination of 4 in. CD100M and 6 in. CD150M pump models.

The CD100M is equipped with a 2.19 L four-cylinder Yanmar 3TNV88 diesel engine rated 24.6 hp at 2200 rpm. The engine drives a Godwin centrifugal pump end with up to 750 gpm flow, 115 ft. total dynamic head capacity and up to 2 in. diameter solid handling capabilities.

Godwin's Dri-Prime CD150M pump is powered by a 4.5 L four-cylinder John Deere 4045D diesel engine rated 71 hp at 2200 rpm. The Godwin centrifugal pump end has a 1700 gpm flow, 160 ft. total dynamic head and can handle solids up to 3 in.

"The bypass was designed for up to 15 million gal. per day," said Nichols. "The relining process requires a dry pipe, so all flow had to be diverted. The size of the lateral and the flow from that lateral coming in on the main bypass determined the size of the pump."

The pump sets are equipped with Godwin PrimeGuard controller panels, which monitor the engine and pump performance. Digital readouts are provided for system functions such as fuel usage, horsepower output and engine speed. A transducer is integrated into the PrimeGuard to monitor the elevation of flow at the suction point to variably drive the speed of the pumps. This allows the pumps to automatically increase speed as demand requires and reduce speed as demand lessens. Additional monitoring at Holmes Run is maintained by two Godwin mechanics with 24/7 on-site availability.

To keep the 18 pumps running at all times, 500 gal. self-contained, double-walled fuel cubes feed fuel to the engines continuously. The fuel cubes are refilled every two days by a hired fuel company, said Nichols.

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While these are typical procedures in a sewer relining application, the Holmes Run project presented some additional challenges as the main sewer line runs through a parkway and a historical area dating back to 1951.

The location had a noise requirement of 69 dB(A), said Nichols. "We provided sound-attenuated machines--our critically silenced versions. The engine and pump are inside an enclosure to reduce noise level. We make use of sound-deadening insulation, a hospital-grade muffler, and waterproof, high-density fiberglass acoustic jackets on the exhaust piping and manifolds. These machines are as quiet as possible, but have been engineered to continue to operate safely and efficiently."

Holmes Run also resides within a protected park area, requiring trees, greenery and a bike path to remain intact during the repairs. Godwin diverted the flow in the protected areas using custom-built 24 in. road ramps. "We're running right beside a pretty major river with homes on it. There are no parallel pipelines that we could say 'OK, divert the flow out of this line into another one.'

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"It's the only existing sewer in that area capable of handling the 15 million gal. per day. It is one of the main trunk lines for Alexandria going to the treatment plant, so there's really not an alternative method to be able to divert the flow. The flow has to go somewhere."

Total installation of the 18 pump sets ran nine days, with the project going live on June 23. The project was completed July 18. The main pumps remained in place through the entirety of the project. As the Insituform incrementally relined sections of the pipeline, any lateral pumps that were not required were removed from the site.
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Title Annotation:STATIONARY EQUIPMENT
Author:Geske, Dawn M.
Publication:Diesel Progress North American Edition
Article Type:Cover story
Date:Aug 1, 2008
Words:893
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