A leak in a Charlottesville, Va., pipe leads to a quick emergency bypass
The Rivanna Water & Sewer Authority (RWSA) in Charlottesville, Va., operates four water resource recovery facilities (formerly called wastewater treatment plants) and serves more than 120,000 customers in the city of Charlottesville and Albemarle County in central Virginia. RWSA takes pride in its record of facility discharge permit compliance and reputation for not only meeting, but exceeding requirements in its permits. So when the authority discovered a compromise in the 54-in. secondary effluent water line in the middle of its Moores Creek Advanced Water Resource Recovery Facility, it took immediate action to address the problem as quickly as possible.
Calling in the Experts
The RWSA team knew it needed to do a full inspection to determine whether the 54-in. line needed to be repaired or replaced. The first thing it needed to do was to implement a temporary bypass. The team called its local Xylem branch for assistance. RWSA had worked with the Xylem team previously, so it knew it would be in good hands.
“We needed to get it done fast, and we needed to get it done right,” said Tim Castillo, wastewater manager for the Moores Creek facility. “The expertise and capabilities that the Xylem team brings to the table are what we needed going in. They are a strong partner and they got it done as designed, and that eased a lot of concerns with our staff.”
Over the River
The secondary effluent water line that the temporary bypass had to circumvent crossed from one part of the Moores Creek facility to the other, going under the creek—which runs through the middle of the facility—along the way. As a result, the bypass had to circumnavigate natural and manmade obstacles, including the creek bed, a number of clarifiers and the Moores Creek Lane Bridge. Since the bridge was the only access point to the back half of the complex and the authority’s administration building, shutting down the bridge for any length of time during the bypass was not an option.
No Time to Waste
Time was of the essence for getting the emergency bypass in place, so as soon as the plan was finalized by RWSA and Xylem engineers, the Xylem team started mobilizing pipe and necessary rental equipment.
To handle the 30 million gal per day of flow RWSA needed, the bypass required three flanking lines of 18-in. high-density polyethylene pipe. The length of the bypass turned out to be approximately 1,400 ft, so 5,000 ft of pipe were mobilized from various Xylem facilities. Once on location at Moores Creek, the pipe was fused and assembled by Xylem technicians, 500 ft at a time, and then dragged into place and fused together.
To drive the bypass, four Godwin diesel-driven, critically silenced CD400 pumps were mobilized and installed. To save energy and diesel fuel costs, the bypass design called for the pumps to be installed and started sequentially, only kicking on as needed. Each pump was set up with a level transducer, which was pre-set to turn the diesel pumps on or off depending on the fluid level in the wet well. There was a dedicated pump on each of the 18-in. lines and each one handled approximately 10 mgd of flow. Each pump was only activated if increased system flows called for additional pump activity. During lower flow, one or two pumps would be running. As many as three pumps would run during higher, peak flow activity. The fourth pump was an open-canopy, redundant mechanical backup, should any of the other three pumps fail.
For additional peace of mind for the RWSA team, the bypass system also was set up with an alarm agent programmed to alert RWSA personnel if the pump was not running at optimal levels, or if it was approaching failure.
Since the bypass had to negotiate the busy bridge without shutting down traffic, the Xylem team worked 24/7 shifts to expedite the installation, getting it done in less than a week. Once the flank of pipe was installed across the bridge and line of traffic, three road ramps were provided to maintain bridge access during the month-long emergency bypass operation.
RWSA was fortunate to be able to identify the problem with its 54-in. secondary effluent water pipe before it became a bigger issue. It certainly could have been a challenging situation, but the quick response by the Rivanna team is an example of the environmental stewardship RWSA is known for, with a focus on keeping local streams and rivers safe from negative environmental impact.