As rain poured down on Clarksville, Tenn., and floodwaters rose in early May 2010, the city’s utility collections team members could do little besides wait to find out what they would face when the waters receded.

As it turned out, that was quite a bit. In the months afterward, they scrambled to keep diesel-driven bypass pumps at lift stations fueled and maintained, refurbished or fully rebuilt several major lift stations, jet-vacuumed countless cubic yards of silt, sand and gravel from 16- to 48-inch mainlines and a great deal more.

In the weeks just after the flood, crew members worked ridiculous hours, some staying for several nights in hotels because flooded roads and closed bridges kept them from going home. It took 30 months before the system was fully restored and functioning normally.

The city’s wastewater treatment plant had its own issues during the flood and as of late 2014 still had not resumed normal operations (see a feature story in the March 2015 issue of Treatment Plant Operator magazine).

Pat Hickey, general manager of Clarksville Gas & Water, the city’s utility, praises the collections team members for their proactive approach at the flood’s onset and for their diligence in the long weeks and months that followed. “One thing we learned is that we have great people who know their jobs,” he says. “As the emergency developed, they had the vision and the ability to look forward and take appropriate measures.”

Rain and more rain

Rain began on April 30, 2010. “The forecast called for some heavy rains, but nothing out of the ordinary,” recalls Mike Crawford, Public Utilities senior manager, Wastewater Collections. “But as the night went on, it rained more and more.

“The first thing we noticed was the river rising. At the wastewater treatment plant, the influent flowmeter went up to 60 mgd instantaneous flow. At somewhere between 40 and 50 mgd, the influent lift stations were maxed out, pumping all they could pump. I called my supervisor [Kevin Buchanan, Public Utilities director, Water and Wastewater Division], and together we decided to cut some of the lift stations off. We were worried about washing out the plant and losing the biomass there.”

As they turned off a main lift station along Riverside Drive, a downtown thoroughfare, river water started coming up through the street drains. “We called several people in and directed them to turn off the influent lift stations,” says Crawford. “An hour later, water started coming over Riverside Drive. It kept rising. We looked at the weather radar and said, ‘Oh boy, this is going to be a big deal.’”

How right they were. As entities including the Federal Emergency Management Agency (FEMA) began reporting flooded roads, Crawford realized that some team members living outside the city would not be able to get to work in the morning. He called several to come in and arranged hotel rooms for them.

“We did a quick inventory of our emergency bypass pump fleet and realized we would not be able to meet our needs,” Crawford says. In a frenzy of phone calls, he arranged to rent 14 diesel bypass pumps (Godwin, a Xylem brand) from Heartland Pump Rental & Sales in Nashville. The pumps, sitting on a barge in San Francisco Bay, arrived in Clarksville in 28 hours, with help from a high-speed state trooper escort starting from the state line at Memphis.

Garth Branch, wastewater engineer, observes, “Every community along the Cumberland and Red rivers was facing the same difficulties that we were, and everybody was scrambling for the same limited resources. We were fortunate that Mike was able to procure those pumps. If we had waited until we actually needed them to start looking for them, we wouldn’t have had any luck.”

Nowhere to go

Unfortunately, the pumps (300 to 3,000 gpm ratings) were useless until the water receded. Even then, the wastewater treatment plant remained under water. “We had nowhere to pump to,” says Crawford. “We had to make a choice: protect the public or protect the environment. We chose to get the water as far away from the public as possible. So we did a lot of bypass pumping at neighborhood pump stations that were overflowing.”

Utility leaders worked closely with the Tennessee Department of Environmental Conservation (TDEC) to identify overflow points on the river as far downstream from the city as possible. That pumping continued, with TDEC’s approval, for about two weeks, after which the wastewater plant had restored primary treatment.

At that point, says Crawford, “We still had limited treatment capacity at the plant. It was a balancing act to decide what we could pump through the system and what the plant could handle. There was hour-by-hour communication between the collections system team and the treatment plant on where their flow was at any given time. We even had some of the bypass pumps on timers so they would pump at a higher rate overnight.”

In the final analysis, the flood inundated 13 lift stations, destroying the motors, electronics and wiring. Those flooded were the largest, the most important and the farthest downstream, several of which were in the city’s combined sewer area along the Cumberland River. Smaller pump stations were flooded as well, some more than 500 feet above sea level and up to 10 miles from the river.

“There were six larger main stations that we ended up not just repairing but doing extensive work on,” says Branch. “Those were capable of 10,000 to 13,000 gpm, and those were the ones that took 30 months to come online. Some other stations damaged were small grinder pumps and suction lift pump stations rated from 10 gpm to about 300 gpm. Those were rebuilt in a month and a half.”

Plans accelerated

The major pump stations were aging and already on the utility’s long-term capital plan for upgrade. “Our schedule got accelerated and compressed,” Hickey says. “I don’t think otherwise we would have chosen to do them all at once. What we might have done in the course of 20 years, we had to do in two.”

In three separate construction contracts totaling $13.5 million, overseen by the Camp Dresser McKee engineering firm, the city refurbished four major lift stations and demolished, redesigned and reconstructed two.

“Everyone worked together great,” says Hickey. “Our engineering team got right in with the design group. As soon as they realized what we needed to do, they rolled up their sleeves and worked many hours a day. In everything they did, they followed FEMA guidelines to make sure we wouldn’t preclude the ability to be reimbursed. CDM relied heavily on our team for expertise and knowledge of the system.”

The projects included installation of 16 wet-pit and dry-pit submersible pumps (Flygt, a Xylem Brand), two or three per station, in ratings from 900 gpm to 4,500 gpm. The pumps are outfitted with variable-frequency drives. The work also included:

• Upgrades to meet current codes (such as handrails on steps down to the wet wells)
• Permanent emergency bypass pumps in two stations
• Emergency generators in four stations (Kohler, rated 300 to 500 kW)
• SCADA integration for the lift stations (completed by SAS of Dallas)
• Construction of powerhouses separate from the pump stations to house the VFDs, motor control centers, electrical equipment, switches and other gear above the flood line

“Those powerhouses were very interesting to move into place,” recalls Chris Lambert, Public Utilities senior director, Water and Wastewater Division. “The size of the structures and the locations made it challenging. One of them had to go down a narrow, winding, wooded road. We had to cut trees out to get the truck and the powerhouse through. Then a crane had to lift the powerhouse over a set of power lines, reach over and set it down. It made us all nervous.”

Down in the pipes

The storm damage to the collections system brought challenges of its own. “We had one area of mainline that stayed surcharged for 30 months, really until the new pump stations came online,” says Crawford. “We had an exorbitant amount of sediment in some of the big mainlines. In the combined sewer area, grit and gravel from the storm system accumulated in the pipes.”

The utility owns two CCTV inspection vehicles (outfitted by Aries Industries and Envirosight), but because they were committed to normal duty, the team called in a contractor (Hydromax) to help inspect the lines most affected by the flood. The most critical section involved about a mile of 16- to 48-inch pipes along Riverside Drive.

Teams used two Vactor combination trucks (one 80 gpm/2,500 psi, one 40 gpm/2,500 psi) to jet and vacuum the lines, some of them up to three-fourths full of debris. “We would pull the debris back, vacuum it up and haul it off,” says Crawford. “On some of the lines along Riverside Drive, we were doing well to clean 2 to 3 feet an hour. At 100 pounds per cubic foot, that’s a lot of dirt. The process took months.”

The team deployed basic jetting nozzles as well as special units designed to travel across the pipe bottom and flush out sediment. Primary nozzles used include:

• StoneAge Tools’ Warthog WG-1, Warthog WG-1 Classic and Warthog WG-1 with descaling head (50 to 80 gpm/5,000 psi maximum) for 8- to 36-inch lines
• Torpedo nozzle from KEG Technologies (1-inch, 3,000 psi maximum) for 6- to 18-inch lines
• Flounder floor cleaner nozzle from USB Sewer Equipment Corp. (1-inch, 52 gpm/2,000 psi maximum) for 12- to 24-inch lines

Lessons learned

The Clarksville experience brought lessons that could help other communities that face the threat of severe flooding. “We spent a lot of time and a lot of effort trying to react, trying to prepare, trying to see what was coming next,” Crawford recalls. “In reality, the best thing we could have done as the storm took shape was have everybody go home and get some rest, because you can’t do anything until the water goes down – nothing, aside from lining up equipment and resources.”

Hickey adds, “One big thing we had in place that everybody should consider is an emergency purchasing policy. We found out early that whenever you called to get three quotes, by the time you called back, sometimes the item you needed was gone.

“Our emergency purchasing procedures allowed us to get equipment. Sometimes vendors are sitting waiting, and the first one to send a purchase order gets the equipment. We could have a PO within a minute. That’s huge in a situation like this, especially one as widespread as this was. It encompassed a huge area.

“It’s also important to have contacts already in place, to know people’s names and put faces with names. It’s invaluable to have that set up, because then when you have an emergency it’s a lot easier to call on those people and get a response.”

One such relationship was with pump supplier Heartland Pump Rental & Sales, now owned by Xylem. “We had dealt with them many times on many things, but this was by far the largest, and they were extremely responsive to our needs,” says Lambert. “We had worked with them at all of our lift stations, so we could just call and tell them where we needed it, and they already knew what we needed. The credit for that goes to our engineering and collections staff for working with them and having that relationship set up.”

And now that it’s all in the rear-view mirror? “We’re glad it’s over,” says Lambert. “And we hope we never see anything like it again.”

More Information

Aries Industries, Inc. - 800/234-7205 - www.ariesindustries.com

Envirosight - 866/936-8476 - www.envirosight.com

Flygt - a Xylem Brand - 855/995-4261 - www.flygtus.com

Godwin, a Xylem brand - 800/247-8674 - www.godwinpumps.com

Hydromax USA - 877/389-2227 - www.hydromaxusa.com

KEG Technologies, Inc. - 866/595-0515 - www.kegtechnologies.net

KOHLER Power Systems - 800/544-2444 - www.kohlerpower.com

StoneAge, Inc. - 866/795-1586 - www.stoneagetools.com

USB Sewer Equipment Corporation - 866/408-2814 - www.usbec.com

Vactor Manufacturing - 800/627-3171 - www.vactor.com