In 2010, many parts of the United States saw severe flooding. In late March, Rhode Island received storms that in some areas produced what observers later called a 500-year flood.
That meant big trouble for the Warwick and West Warwick wastewater treatment plants, both built on sections of 100-year floodplain along the Pawtuxet River. The flood overwhelmed both plants, taking them completely out of service for a time.
The events began with what plant personnel call the “little flood,” about six inches of rain that fell in four hours on March 17. The area then received nearly eight inches of rainfall in a 24-hour period leading up to March 30, on ground already well saturated. Cumulative rainfall for March was nearly 15.5 inches — a record for the month.
After weeks of struggling to get treatment back online, the managers and staffs, along with engineering consultants and contractors, spent much of the year restoring and replacing equipment and electrical systems.
Representatives from both plants shared their experiences, and lessons that may someday help other plants face emergencies of their own, in interviews with Treatment Plant Operator. Participants were:
- Janine Burke, executive director of the Warwick Sewer Authority.
- Patrick Doyle, assistant superintendent of the Warwick Wastewater Treatment Facility, a 7.7 mgd advanced secondary treatment plant.
- Peter Eldridge, superintendent of the West Warwick Regional Wastewater Treatment Facility, a 10.5 mgd tertiary plant.
TPO: Can you describe the location of your treatment plant?
Burke: We’re in a little nook, a little bend of the Pawtuxet River. The river basically wraps around us on three sides. In the early 1980s, they built a levy around the treatment facility. It’s only on three sides — we have Interstate 95 on the fourth side. The levy is 17 feet high and 21 feet above the 100-year flood elevation.
Eldridge: We’re about two miles upstream from Warwick. We’re not protected by a levy. We have an average of four-and-a-half-foot walls on the clarifiers. For the pump stations that are below grade, we have to climb stairs and then go down into the pump room. All of our walls had been high enough, until this event.
TPO: What exactly happened on and around March 30?
Burke: On Monday (March 29), it began to rain. Tuesday morning it was obvious things were getting pretty bad. Our superintendent, Joel Burke (no relation to Janine), told me we would need to shut down a couple of pumping stations. I went to the city’s Emergency Operations center to record a reverse 911 call to the residents served by those pumping stations, telling them not to flush their toilets or their facilities until further notice.
Meanwhile, our guys were moving equipment and vehicles out, getting our camera equipment and vacuum trucks secured on high ground. A little after one o’clock, they called me to say the river water was coming up over the levy and starting to fill the treatment plant.
Doyle: At that point our facility was like a big soup bowl that started filling up. The water overtook the tanks and ended up being as high as three feet above the levy.
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Burke: I would say within 45 minutes this place had a couple of feet of water in it. Some of the guys stuck around to move records and computers up to the second floor of our operations building, trying to get things out of harm’s way. But then finally they had to get the heck out of here.
Eldridge: I could see the water backing up into our facility and just overtaking our secondary clarifiers. In what seemed like a really short time, we were underwater. We were able to keep on pumping from our eight pump stations. If anything was good about this event, it’s that we didn’t have any wastewater backing up into people’s houses.
TPO: What were conditions like at the height of the flood?
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Burke: In my office, which is at the high end of the plant near Route 95, there was six feet of water. And at the low end of the plant, there was about 10 feet. One of our people did a quick calculation and determined that we had about 75 million gallons of raw sewage and river water sitting in our plant basin.
Doyle: While the treatment plant was underwater, we still had 42 or 43 of our 48 pump stations pumping raw wastewater into the basin. So there was a big bypass right into the Pawtuxet River. We had to keep the wastewater flowing so it didn’t back up into the rest of the city. It kind of tugged at the heartstrings to come to a treatment facility that had run so well and see raw wastewater being discharged to the environment.
TPO: As the floodwaters crested and began to recede, how did you begin to restore treatment?
Eldridge: It took at least three days for the river to recede totally out of the plant. And then we started a lot of cleanup, a lot of hosing down, as the days went on. Right off the bat we had chlorine delivered — we normally have UV disinfection — and we started disinfecting.
All our pump stations were still pumping to us. We had flows going through the primary clarifiers, although we couldn’t pump our sludge out. We had no aeration at all. We were able to settle everything out that we could, and the water we had going out, we were able to disinfect.
Doyle: We’d been able to save our SCADA servers and get them to high ground, and that enabled us to get monitoring capabilities back for our pump stations within a week. Once the plant basin was pumped out, we got back in and started cleaning up.
Burke: The flood didn’t go down far enough until Friday for us to start dewatering the facility. So in the interim, all we could do was plan for how we were going to get out of this thing. We brought in our engineers (Hart Engineering Corp. of Smithfield, R.I.), and anybody we thought could help us, and we figured out a plan.
Joel and Patrick worked with the engineers to come up with a critical path — what equipment we needed to address first. Obviously, we wanted to get the preliminary treatment up and running and re-establish forward flow at least through some tanks so we would have a point where we could disinfect it.
Doyle: One advantage of getting Hart involved early on was that they had the resources and contacts. They were able to quickly mobilize some huge dewatering equipment and get it here fairly quickly.
TPO: Presumably the flood knocked out utility power. How did you go about restoring electricity?
Eldridge: As soon as the plant was going underwater, I ordered a 1,500 kW generator from the local Caterpillar dealer. It arrived in the late afternoon and was set up. As of late August, we were still on generator power. At that point we had the 1,500 kW unit and one 800 kW machine.
Our engineers (James J. Geremia & Associates of Providence, R.I.) came right in, and we started bringing in contractors to remove damaged pumps and motors and start restoring the electrical system.
Doyle: Power was one of the first critical things we had to address. We had some of our own generating equipment, but here again Hart helped us. At one point there were nine portable generators, stationed at each of the treatment buildings. We had anywhere from a 60 kW generator for small loads up to a 400 kW for the larger-amperage draws. In total, we probably had 1,000 kW in temporary power capacity.
Hart subcontracted an electrical contractor, who hooked up, in each building, a temporary switchboard. The generators were wired directly into those temporary panels, which we were still using as of late August.
As new equipment came in, they removed the older equipment that was damaged and installed new motor control centers. Then once everything was wired in, they jumped from the temporary panel boards over to the new motor control centers.
The biggest cost in this recovery is for the electrical system. All of the electrical was underwater, and because of a wicking effect, water went into all the wires, and we basically had to pull out every single wire in the plant and rewire it.
TPO: What about restoring secondary treatment? How long did that take?
Burke: We do biological nutrient removal. We had primary treatment and disinfection back up in about a week. The next critical path was air. The blowers were completely wiped out, so we spent a lot of time getting that equipment back up and running. By the end of May, we had that system in pretty good shape. We had to get some bugs from a neighboring community.
Around the beginning of June, we had secondary treatment, and then within a couple of weeks we were back to meeting all of our permit conditions. With the BNR system and the aeration system going, we were pretty quickly able to start removing nitrogen again.
Eldridge: We had primary treatment online two weeks after the flood event, and we had to run that way for a number of weeks before we could get anything else going. Our maintenance staff did a lot of work on the secondary clarifier motor. Then with the help of our electrical contractor, and more portable generators, we were able to get the secondary skimmer arms going. That was accomplished by the end of June.
Tertiary treatment came back online in mid-August. We have a biologically aerated filtration system made by Infilco Degremont with upflow media filtration. We spent about six weeks changing out all the valves, pulling all the wiring and installing all new drain valves. Then we backwashed the media, started running methanol for a carbon source, and gradually got our numbers back to where we’re supposed to be.
TPO: How well would you say your plant team responded to this event?
Eldridge: It’s amazing what the guys and women that work here have been through. We had some tough conditions. There were no refrigerators, no soda machines, no sinks. There were portable toilets around the plant. They really stepped up to the plate and did everything they could, as safely as they could, to help us get this plant back online.
Burke: When this first happened, I said to myself, “This is going to take a year.” Yet in a week, we established forward flow through the plant. It was amazing to me.
Doyle: The first week, our guys were working anywhere from 65 to 70 hours. That tapered down to maybe 60 or 65 hours the second week. Within four weeks we were back down to 40 hours a week.
TPO: What was the total cost of this disaster?
Eldridge: We are a little shy of $10 million. Our insurance policy is $10 million, so we should be able to handle the recovery without going through FEMA.
Burke: We estimate $10-12 million, and we have $10 million flood insurance.
TPO: What lessons did you learn from this experience that might help other operators deal with emergencies or natural disasters?
Burke: You need to have a plan. We didn’t really have a plan for this, to be honest. We thought we were protected by our levy. Still, it all came together and things really worked out well. A bigger issue is that we need to get the wastewater profession involved in emergency response exercises. It seems like people just forget about us, and yet it’s a major public health issue if your treatment facility is not operating.
I think as a result of this flood, the fire and the police departments, the mayor’s office, the department of public works, and everyone has much more respect for what we do and how we do it. Wastewater needs to be part of the incident command structure in every local community.
Doyle: From a more hands-on perspective, before the flood our SCADA system was down on the ground level. We have a second floor in our operations building, so we’ve moved all our computer equipment upstairs to get it out of harm’s way. We’ve moved our servers, the city servers, and the SCADA network servers.
Eldridge: At the time of the flood, we were in the process of upgrading our filing system and converting our stored documents to digital. We had a number of things that got wet. If I could do anything over again, that’s one thing I would address. We can’t move the plant, but we can keep on documenting everything we’re doing and putting it in electronic format, and put paper documents in off-site storage.
TPO: Where are the positives in this experience?
Burke: If there is a silver lining arising from the sludge, it’s that in the end we’re going to basically have a brand-new treatment facility, with new turbo blowers and some new energy-efficient equipment.
Eldridge: We’ll also be installing a new turbo blower, and we’ll be upgrading our emergency generators based on what our electricity demand will be with our new phosphorus requirements. We bought three 800 kW Cat generators.
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