From addressing the unexpected storm surges that hurricanes dump on coastal communities to flooding that occurs from antiquated systems or increased impervious surfaces, communities throughout the United States are finding relief through the installation of modern pumping systems that are bigger, faster, and stronger.
They may be temporary or permanent measures, but the multimillion-dollar systems that deal with flooding or storm sewer problems bring a satisfactory return on the investment, community leaders say.
Ocean Ridge: Protecting Low-Lying Development
Consider the town of Ocean Ridge, FL. In 1999, Hurricane Irene blew through the tiny town, which is sandwiched between the Atlantic Ocean and the Lake Worth Lagoon on the state’s southeast coast. The hurricane dumped more than 18 inches of stormwater on the town, which had in place an infrastructure dating back some 50 years.
“We know from our modeling that the system itself is not sized to adequately remove the stormwater based on total build-out of the town,” says Lisa Tropepe, vice president of SFRN in West Palm Beach, FL, and a licensed professional engineer for Ocean Ridge. “We also know that the Federal Emergency Management Agency elevations have been changed over the years, which doesn’t help older communities because finished floor elevations are well below the 100-year flood stage. A finished floor has to be able to sustain a 100-year storm,” she says.
“Many homes in the southern part of Ocean Ridge are below the 100-year flood stage, she adds. It makes it very difficult to train water uphill. We have to use mechanical means to remove the stormwater. We have an issue not only of quantity, but also an issue of quality because we cannot discharge stormwater into the Atlantic Ocean, and the Lake Worth Lagoon is an impaired water body.”
To handle quantity issues, Tropepe set up two large pit pump stations–one underneath a road in the lowest part of the town and one in a detention area–in a project initiated in May 2000 with a flood control study.
The project includes a basin covering more than 65 acres of dense residential development. At the south of the layout is the pumping station under a roadway that houses three submersible 15,700 -gallon-per-minute and two duty 5,600-gallon-per-minute pumps. The smaller duty pumps will be used during minor rainfall events, with the second duty pump available as a backup. The station will pump into a 48-inch C900 PVC force main approximately 2,000 feet in length. The force main will outfall into a 2.5-acre detention/passive park area that will ultimately overflow into the Lake Worth Lagoon (Intracoastal Waterway). The pumps are manufactured by Farmers Pumps Inc. in Pompano Beach, FL.
She adds that the quality issues concern an existing 48-inch outfall that drains the area and State Road A1A. It has no pretreatment and is silting up a residential marina, so it will be eliminated and replaced with a detention area with several pollution control mechanisms in place to ensure the ultimate discharge into the Lake Worth Lagoon will be clean water.
The north end of the project layout involves gravity pipes that flow into another pump station of similar pumping capacities. This station pumps into the detention/passive park area as well and is located there.
“The approach enables the town to handle stormwater flows for the densely populated area and will enhance the quality of life for more than 1,000 people, Tropepe notes. Now during daily rainstorms, like in the wet season [summer], the duty pumps will be able to maintain the stormwater removal.”
Tropepe says the solution of two stations is rooted in the need for redundancy. “If the one doesn’t work, then the other one will work,” she says. Same with the three main pumps–“we’ve got it set up so that two pumps will be working at the same time. If one pump goes down, then the third one will kick on.
“Since the main pumps are there for major or frequent storms, the duty pumps might not be able to handle all of the flows.”
In the storm sewer modeling Tropepe’s company used to create its plan, engineers evaluated the existing system, a setup of concrete and metal stormwater pipes and catch basins that meanders in and out of roads, between homes, and in some cases underneath structures. In running the model through several storm events, the system proved to be inadequate because of road elevations that would make it impossible to move stormwater without doing so mechanically.
Ocean Ridge received $900,000 from a state grant toward the cost of the project, which is $5.5 million for the construction phase. Through the Clean Water Act, the town received a $300,000 federal grant for its detention area. The state’s Department of Transportation is also contributing $230,000 because its roads go through the town. The rest of the cost is being financed through a low-interest state loan for stormwater purposes. Because Ocean Ridge is a small town, the construction was contracted out through bid. The project is expected to be completed by the end of January 2006.
“They made a conscious effort to utilize that area for this stormwater project with the hope it also can be utilized for a passive park, and we’ve been able to achieve both,” Tropepe says.
Tropepe’s firm also considered a drainage injection well system. “We received permits for that from the state Department of Environmental Protection [DEP]; however, the regulations put forth on the permit caused the bid to be just as costly as it would have been to do the conventional pumping, the force main detention area system,” she says.
“The multiple injection well system has never been permitted in Palm Beach County before. The DEP limited our ability to initially utilize only two wells with the capability of going up to six wells, so that uncertainty, plus the fact that the costs were the same, took the decision back to a conventional force main pumping detention system.”
“There have been other complications, namely right-of-way issues. The road where one of the pumping stations will be located is on what originally was a private road,” Tropepe says. “The people owned the property to the center line. We needed 100% participation for the homeowners to give us the easement ability to use that road, and part of the five years it has taken us was getting permission from the homeowners to utilize that road, which we do have now.”
The state has been cooperative in offering permits in order for the system to be constructed in the DOT’s right of way, she adds. The detention property already was owned by the town.
The project has been so challenging and complex that Tropepe was recently awarded a Technical Achievement Award for 2005 for the project by the Palm Beach County chapter of the Florida Engineering Society.
“The biggest challenge is not necessarily the technical ability to move the stormwater, but it’s the educational aspect of changing an area where homeowners have lived for many, many years,” Tropepe says. A lot of what we have to do as civil engineers is be able to communicate complex systems.”
“Another residential concern of those who live in the upscale community is what the passive park will look like. Right now, it’s an upland area full of exotic vegetation, but to a lot of people that exotic vegetation is beautiful, so it’s been a little bit of a challenge to explain what’s going to happen there and how it is going to look,” Tropepe says.
One thing that has been a blessing in a way is that people understand what a generator is now that we’ve gone through Hurricanes Irene and Frances,” she adds. They didn’t really understand the purpose of that big box on one of the sites, but now when I explain to them a generator is going to be located there, they are much more supportive than they were before.” The generator will kick in when the electricity goes out, a frequent occurrence on a barrier island.
“Residents will soon realize the return on their investment. The result will be that the townspeople should be able to drive their cars down the road during high tide when it is raining,” Tropepe says. What occurs now is during a high tide, or during a rainfall event, the police department sends emergency mobile pumping units to the site and places those pumping units in the catch basins so people can get out of their homes.”
When Irene hit in 1999, not only the roads but also several homes were left flooded. During Florida’s particularly busy hurricane season of 2004 when four of the weather events came through the state, everyone became aware of the importance of moving stormwater, Tropepe notes.
“Sometimes good things come out of a disaster, and one of them is education,” she says. Pumping systems and generators now are terms that are in our everyday language more than they were before.”
Virginia Beach: Raising Against Hurricanes
Another area familiar with the effects of hurricanes is Virginia Beach, VA, where the US Army Corps of Engineers, in conjunction with city personnel, built an extensive pumping system. It started as a result of a 1995 hurricane protection project for the oceanfront.
The project required raising the beach elevation from a six to a nine to make it bigger and higher. That elevation, though, blocked all of the gravity storm drains that had existed in the oceanfront area. With the outfall blocked, the city had to collect the water behind the line of protection and pump it.
Enter the Corps of Engineers, which designed a pump project and chose the components. The project was done in cooperation between the corps and Virginia Beach, with 35% of it funded by the city and the remainder by the federal government. The corps took the lead in design and construction, and the city provided technical personnel to work through the design and the construction with the corps.
The corps built two pump stations over a seven-year period, with sections of boardwalk and seawall being built each winter. The 16th Street Pump Station was built in the winters of 1999 and 2000, and the 42nd Street Pump Station was completed in 2001.
The 16th Street station has three 48-inch-diameter, 50,000-gallon-per-minute pumps, each with its own discharge line. Project Manager Phill Roehrs, who works for Virginia Beach’s public works beach management, explains that the pumps are set to operate in parallel. The first pump will begin operating, and if the flows are larger than it can manage, the second pump can engage, and then the third pump if necessary. The city uses pumps from KSB, a European manufacturer.
“Once we set the criteria for the project, chose the beach grade, and selected the elevation of the seawall and the boardwalk, our options for pump configuration were pretty well limited,” Roehrs says. Given all of the other constraints of the project, this would be the most obvious solution.”
Roehrs says the pumps have performed flawlessly in terms of maintaining positive drainage for the service area, for the basin. Their being ocean outfalls, they are 2,200-foot-long pipelines that extend offshore in concrete pipelines.”
However, there have been some challenges. The city had some difficulty with some of the pipelines at the 42nd Street project site, which has four 50,000-gallon-per-minute pumps. The station has a slightly larger drainage basin, and the city had problems with the outfall pipelines as they were being constructed at 42nd Street.
“We ended up sliplining the concrete pipeline that had been cracking with HDPE for the first 500 feet through that problem area,” Roehrs says. Otherwise, the stations have performed as planned.”
Other solutions that had been considered included a gravity discharge system, which would have involved using pumps to lift the water where necessary and then allowing it to flow by gravity through the pipe system.
In considering hurricane measures, the city also looked at providing more protection with the seawall and less protection at the beach, thus leaving the beach low enough to allow the old gravity system to stay the way it was.
“But in the end, we choose the best economical solution in providing a nice, big beach and a seawall that’s not impressive and doesn’t overwhelm the landscape, and then balancing that with the higher beach,” Roehrs says. That then caused the need to pump.”
“Their operation is obviously more energy dependent,” Roehrs says. But the old gravity system it replaced required an enormous amount of labor to keep the sand from clogging the pipes. “There used to be gravity outfalls onto the beach at about the same elevation as the beach, so every storm would come up and clog our pipes. There were ongoing costs from the gravity system that shouldn’t be ignored.”
Together, the pump stations cost $20 million to construct. The last phase of the project, which awaits funding, is a detached phase at the northern extent of the project area, which involves the installation of an ocean outfall pipe for the pre-existing 79th Street ocean outbound pump station.
Roehrs explains that a coastal community’s main worries about hurricanes are storm surge and wave attack. “When the sea has risen and is elevated by water being pushed up in a storm surge, that’s your tailwater elevation you’re draining to, so if your tailwater rises, then you’re losing the ability to discharge stormwater. That’s a significant concern,” Roehrs says.
Another concern is the city’s intention to build and maintain a beach and a seawall that would prevent the hurricanes expected in Virginia Beach’s latitudes from overtopping the protective structures and flooding the land behind it, he adds. “That has some obvious stormwater implications–the huge amounts of seawater that might flood the streets here,” he says. If we can prevent that overtopping, that’s a major stormwater issue all by itself. The way we can overcome the risen sea and the higher tailwater is by adding energy pumping.”
Roehrs cites another benefit of the project. We used to allow our stormwater from the beach resort area to flow by gravity across the beach, and there were some 80 or so discharges through our seawall out to the beach,” he explains. There were puddles and pools of water on the beach from stormwater with various types of litter.” Now, the debris is removed before the discharge goes into the ocean.
“We discharge 2,300 feet offshore, out of direct contact with sunbathers and others,” he says.” If you had seen these ponds with their rings of pollen in the spring and cigarette butts and cups and now you don’t see any of that, you’d realize the environmental enhancement it’s created.”
Northern Illinois: Cooperating to Alleviate Flooding
Another region pleased with the environmental results of its new pumping system comprises the towns of Loves Park and Machesney Park in northern Illinois. The towns share a common border along Elm Avenue, which had been experiencing a lot of flooding. But for a long time, opposing political clashes kept a resolution at bay. The area didn’t offer much topographic relief, and the nearest drainage source–the Rock River–is located far from the project area.
In the late 1980s, Machesney Park reconstructed Elm Avenue to a curb and gutter standard that used a series of dry wells. An engineer had designed a system of pipes to collect the runoff, connecting to concrete tanks with holes that allowed the stormwater to seep into the ground. Over time, however, the holes filled with silt, rendering the tanks ineffective and causing flooding.
“We’ve got sandy soils in this area, and for lack of storm sewers, when the Village of Machesney Park reconstructed its portion of Elm Avenue, it did so on dry wells. Those dry wells flood rampantly,” says Chris Dopkins of the engineering firm McMahon & Associates in Machesney Park
In fact, many times if we had a lot of rain, the news would set up its trucks on the corner of Elm and Evans and watch cars drive through 10-inch-high water,” he says, adding that local municipal officials were well aware they had a problem on their hands.
“For years and years, it never really got solved,” Dopkins says of the problem, citing political factions. “One day, Loves Park decided some businesses in the area were really affected by the flooding in the older sections of Elm.”
Loves Park officials wanted to reconstruct the system and approached Machesney Park officials with a plan. That’s when McMahon & Associates, which serves as a municipal engineer for Machesney Park, considered the options, drawing from the experience of nearby communities.
“Loves Park secured a few drainage easements and an area we could use as a small detention pond north of some businesses,” says Dopkins. We took a look at the hydrologic analysis of the whole site and came up with what we would need for a detention pond and stormwater lift stations.”
With fresh political blood in place, the cities agreed to cooperate. Dopkins’s design solution was to connect the old dry wells along Elm Avenue and install a 48-inch trunk line storm sewer system that feeds into a 4.5-acre detention pond, which is then pumped out by a large triplex lift station. The pond has emergency overflow in case of power loss or a 100-year storm event. Dopkins used TR-55 watershed modeling.
The pump in the lift station runs off of a variable-frequency drive connected to a level sensor, so that as the pond fills up, the pump adjusts its pumping capacity. The lift station keeps the pump from turning on and off and allows it to match flows coming in.
The pump being used is a vertical, dry pit-type pump manufactured by SRS Crisafulli in Glendive, MT. It is located in the fluid area and the motor is not submersible; it is set up for relatively lower heads.
The station pumps down to an Army Corp of Engineers drainage ditch in Loves Park. Now when it rains, once the existing dry well system begins to fill up, the water discharges into the lagoon and the lift station and then pumps it over to the ditch.
The first phase of the $1.2 million project was completed in 2000 in a five-month period that included road reconstruction and the digging of the pond. As funds allow, more pipes will be connected to the lagoon to relieve flooding problems in Machesney Park, and two more simple on and off” pumps are planned, with the end result being three stations and 30,000-gallon-per-minute pumping capacity.
The project has rejuvenated the dry wells, Dopkins says. “We’ve done a number of projects in Machesney Park, and the soils around here are so sandy. We go into these areas that would just flood tremendously and connect them with storm sewers; many times we are connecting them about 5 feet up into a 12-foot-deep dry well. It’s like a big catch basin,” he says.
He says the dry wells are nothing but giant 6-foot-diameter concrete cisterns with holes in the side and no bottom, and with 3-inch wash stone around them for about 7 feet outside the concrete portion.
“As we go in and disturb that stone and the media around it, we tend to make those dry wells work a lot better, and the ground around it starts absorbing more water,” Dopkins says. “Now we really have some good infiltration reestablished upstream of us.”
“Another huge benefit was realized, he says, when old political grudges between the old order” of the towns’ officials were set aside and they began cooperating. Two intergovernmental agreements have the communities share the cost for the project as well as lift station operation and maintenance. The towns also worked out boundary issues that had been in dispute for many years.
“Traditionally, the two communities fought like cats and dogs,” Dopkins notes. This laid the basis for the cooperative relationships that are there today. For Machesney Park, it was a tremendous benefit in that we didn’t have to pick up a lot of water and carry it a long distance to the Rock River in order to solve this problem.” That saved the village a couple of million dollars, he estimates.
“In Loves Park, the solution they came up with would have functioned; however, it wouldn’t have functioned to the level it does now,” Dopkins says. Both communities benefited hugely from the project.”
One of the reasons the SRS Crisafulli systems were chosen for this project was because of the trash that accompanies the stormwater, says Ron Bond of Marshall Bond Pumps in Oswego, IL. Coming from residential areas, the stormwater pulls in everything from Frisbees to basketballs, and one of the prime concerns was whether the pumps could handle the trash buildup rather than them getting bound up with solids.
They didn’t want to go into a situation where they had to station a person out there during a storm event to ensure the trash could be kept away,” Bond says. The other options may have been to install another mechanical device to screen out large solids, but that would have made the project more complex and expensive for the cities.”
Dopkins says there was not a workable gravity solution in this case for stormwater drainage.
Phoenix: A Quick Temporary Setup
Phoenix, AZ, recently needed a temporary solution to an unanticipated problem. Ordinarily, the Phoenix 91st Avenue Wastewater Treatment Plant, with a capacity of 180 million gallons per day, discharges its processed and treated wastewater to the normally dry Salt River. But an excessive amount of rain during winter and spring resulted in water levels rising in the river, threatening to compromise the plant’s discharge capabilities.
We got concerned that the water level was rising, and a significant increase from the upstream dam was being predicted,” says Rick Shane, project construction manager for the city. This had happened before, and when the river starts backing up into the plant, we can’t discharge our effluent out of the plant and the plant would go offline.”
The situation called for an immediate temporary solution: a system that would pump up to 350 million gallons per day from the plant’s effluent channel to the river. Currier Construction installed a system of Godwin pumps at the site that was operational within eight days.
The system consisted of 14 Godwin CD400M Dri-Prime 16-inch pumps, 14 Godwin DPC300 12-inch pumps, and three large axial flow pumps powered by Godwin Heidra hydraulic submersible diesel-power units. The installation took place along a 30-foot-wide dike road, which included the dry riverbed–flooded at the time–on one side and the effluent channel, a concrete-lined ditch. The city then pumped from one side of the earthen berm to the other.
As it was an emergency installation, the pumps were chosen because they are portable and are able to prime from dry. Shane says there was not a lot of time to explore other options in detail.
“We didn’t care if they were going to use 20 little pumps or 20 large pumps or a combination, as long as it worked out to 350 million gallons per day,” he says. The pump setup we got is not the one we envisioned at the time, because they were able to bring in larger pumps.
They initially thought they were going to bring in smaller pumps, and then they were able to get the three axial flow pumps. One of the axial flow pumps by itself pumps 65 million gallons per day. So we just said we need 350 and we have this much space, and the vendors came out, saw the setup situation, and we left it up to them.”
After a short time, the risk of flooding decreased and the city had the system dismantled.
