The project was an important one: Drew Gangnes and his fellow engineers had built five green roofs scattered throughout downtown Seattle. The goal: to see how much rainwater runoff the roofs prevented from hitting the streets of the city and entering Seattle’s system of stormwater sewers.
Gangnes and his team needed accurate data. They needed to know exactly how many inches of rain landed on each roof and how much of that rainfall became runoff. Inaccurate data would render the experiment’s results useless.
The team turned to Bourne, MA–based Onset Computer Corporation. The manufacturer of weather stations and data loggers has long provided its software and technology to engineers working in the stormwater industry, engineers who need accurate rainfall data. The engineers from Seattle’s Magnusson Klemencic Associates, where Gangnes works, relied on Onset’s data loggers from February 2005 until January 2007, when they officially ended their project.
Gangnes, director of civil engineering with Magnusson Klemencic, says the data loggers not only provided accurate information, but also saved his team valuable time.
“With the loggers, we were able to get a snapshot each month of the rain that fell and the runoff that came from each roof,” he says. “We did this for two years. We were able to analyze our data for each month and then for each quarter. It helped us convey very effectively the results of our study.”
A whole industry of software and technology products has sprouted up to serve stormwater professionals. Engineers can work with data loggers, hydraulic modeling programs, systems that help monitor water quality, and pipe-inspection equipment and software. They can even purchase software that helps them make sense of the stormwater permitting systems spelled out by the National Pollutant Discharge Elimination System (NPDES) Phase II regulations.
The good news is that technology providers are constantly working on new products and software. And this is a trend that few in the field—whether engineers or technology manufacturers—see ending any time soon.
“We are selling more software than we ever have,” says Rick Masters, senior developer for Beaumont, TX–based CBI Systems Ltd., a provider of software designed to help municipalities, developers, and engineers manage and develop programs to meet their NPDES Phase II requirements.
“I think it’s taken at least four or five years for the people in the stormwater industry to figure out that they must have a database to keep track of all the construction-site inspection and recordkeeping,” Masters says. “It gets cumbersome in a hurry. After two or three years, they start compiling a pretty large list of construction sites and inspection records. They then realize that some sort of electronic centralized record system is needed. That is what is happening now.”
And CBI Systems isn’t the only provider recognizing the willingness of stormwater pros to turn to new software and technology.
“Our clients are getting savvier all the time when it comes to technology,” says Colby Manwaring, president of XP Software in Portland, OR, a company that makes software for urban drainage and stormwater modeling. “Several years ago, people would do their studies by hand. Then it moved to spreadsheet-type models. Now they are using modeling software. People are realizing that it’s not that difficult to use programs like ours. The systems are accessible to non-technical engineers. You can get your hands on these tools and do a very professional job without spending a lot of time or money.
“People are seeing the value in this,” Manwaring adds. “And their clients are starting to expect that level and detail of analysis from them. The numerical modeling segment of this industry will only continue to grow.”
Fortunately, for stormwater pros, the modeling segment is far from the only technology group that is constantly working to create new programs designed to help engineers do their work better and faster.
Green Roofs in Seattle
In Seattle, Magnusson Klemencic Associates are no strangers to stormwater technology. The company’s recent experience with Onset Computer Corporation’s rainfall data loggers only reinforced its commitment to new stormwater technology.
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Photo: @iStockphoto.com/bibikoff |
Working with local contractors, Magnusson Klemencic engineers designed five green roof test plots, each measuring 8 feet by 12 feet, in downtown Seattle. Each plot featured a different thickness of planting media and different species of plants. The goal was to see which roof swallowed the most rainfall before it became stormwater runoff.
The problem was, engineers faced a real challenge when it came time to measure the amount of runoff leaving the test plots.
“Measuring temperature and wind speed—all that is connected to a data logger. Those things are all pretty straightforward. We’ve been measuring those parameters for some time,” Gangnes says. “What we scratched our heads about was how we were going to measure the runoff leaving the different test plots.”
The solution that engineers came up with was elegant in its simplicity. They angled each plot in two directions so that the rainwater would ultimately filter into a corner drain. That drain was then outfitted with two devices: a simple water meter and an orifice restrictor device.
Engineers then used a pressure transducer to measure the depth of water over time. They used that information to determine how much water flowed from the green roofs. Finally, they relied on Onset’s logging software to reduce the data and determine runoff trends from it.
“Using Onset’s programs to do the logging worked very well for us,” Gangnes says. “We built additional routines into their program to help us take the data and use it once it was in the Onset format.”
The pilot program determined that green roofs did a rather remarkable job of mitigating stormwater runoff. The top-performing plot mitigated 94% of the rain that landed on it. Even the least effective of the five test plots prevented 65% of the rain that fell on it from entering Seattle’s stormwater sewer system.
There were some initially surprising results, though. The top-performing green roof was 6 inches deep with plants and planting materials. It was little surprise that this roof performed better than did a 2-inch-deep green roof and a pair of 4-inch-deep roofs.
But the 6-inch-deep roof also mitigated more runoff than did the deepest roof in the test program, one that featured 8 inches of plants and planting material.
Fortunately, the project called for soil moisture probes, too, which allowed engineers to chart the ebb and flow of water in the soil over time. The difference, they saw, was that the 6-inch-deep plot was the only one with a granular drainage course. The rest of the roofs featured cellular drainage boards.
Once rainfall hit the other roofs’ cellular drainage boards, it immediately began running off. The 6-inch-deep roof’s pumice-like drainage board, on the other hand, held the rainwater in place longer.
Engineers also discovered during the test program that the thinner roofs dried out more quickly following heavy rainfalls. The 6-inch-deep plot, then, didn’t hold water deep in its soil as long as did the 8-inch plot.
“We hadn’t thought through the fact that you can get soil that is too thick for optimal stormwater performance,” Gangnes explains.
The green roof experiment wasn’t done just for show. Gangnes hopes that the program’s results help convince local governments to explore adding green roofs to their municipalities’ stormwater collection systems, especially in a decentralized fashion.
“We hope that this project helps policymakers understand the value that green roofs can play in a decentralized stormwater management regime,” Gangnes says. “Rather than looking downstream as we have stormwater problems, and building bigger treatment plants and retention basins, let’s look upstream. Let’s look at low-impact design techniques. Let’s look at things like rain gardens and bioretention, in addition to green roofs. Green roofs aren’t our only tool, of course, but they can be one of them.”
As technology continues to improve, and more engineering firms conduct experiments similar to Seattle’s green roof test program, more building owners might be willing to give concepts such as green roofs a try, Gangnes says.
“If you daisy-chain green roofs with techniques that you can use at the bases of buildings, you can get to a self-mitigating building that can handle its own stormwater management needs without burdening the downstream infrastructure,” he says. “And it has to be better than just a big tank under a building. Cities should be offering incentives to folks for working with these systems. I can imagine the day when a city pays you to put in a green roof. If enough people do that, it can delay the need to build another treatment plant. Then the net burden on the system is dropping. That’s one of our goals.”
Demanding More Technology
Evan Lubofsky of Onset Computer Corporation says that his company is seeing more requests from companies such as Magnusson Klemencic Associates.
Like other software and technology providers, Lubofsky doesn’t see this trend slowing any time soon. And to meet the growing demands of their clients, company engineers are constantly updating existing products and working on new software and technology.
“The stormwater industry is a good portion of our base,” Lubofsky says. “And we are always working to meet their needs. Three years ago we introduced water-level monitoring. It’s a great way for our clients to find out how fast their holding tanks are filling or draining. They appeal to people who are working with and studying urban runoff.”
Other clients use the water-level monitoring technology to study wetlands before and after development. Often, construction crews create new wetlands during development to compensate for wetlands that are eliminated during the building process. Engineers can use the monitoring equipment to make sure that the newly built wetlands is doing as good a job of capturing and retaining water as was the old one.
Thomas Davies, president of Wallingford Software in Fort Worth, TX, says that new technological advances now allow stormwater professionals to track the flow of runoff not only as it enters pipes, but as it moves through them.
That’s what engineers and municipal employees are doing using Wallingford’s InfoWorks SD, hydraulic modeling software designed specifically for the stormwater industry. They can combine this program with Wallingford’s InfoNet, an asset data management system for water networks and sewer and storm water systems.
The city of Forth Worth provides a good example. City officials have adopted InfoWorks SD as their municipality’s standard stormwater modeling package. They are then using InfoNet to collect, manage, and analyze stormwater data.
City officials turned to Wallingford—and its InfoNet data management system, in addition to its stormwater modeling software—after creating a stormwater utility. The utility is now charged with generating revenue, so Fort Worth officials needed accurate data for billing and collection.
“The city of Fort Worth will be using our products to take archived map data and filed GPS data and merge them into one composite, clean, validated piece of data,” Davies notes. “This is not a trivial exercise. It’s a big job. The consultants working on that job will be using InfoNet to validate and clean that data as it happens. It will be used daily, instantaneously, as the data is collected.”
Davies predicts that more municipalities and private developers will be turning to hydraulic modeling software and data management programs in the future. The technology is too powerful, and gives users such great access to system information, for it to be ignored, he says.
“People today no longer want to just model storm drainage systems looking at the pipes,” he says. “They want to look and see what happens to the stormwater when it gets into the pipes.”
Manwaring of XP Software notes that demand is strong for his company’s flagship product, xpswmm, software that provides users with a variety of hydrologic methods to simulate the runoff process.
The company, though, has worked to make its product even more useful for stormwater engineers, adding in the last two years a two-dimensional overland flow engine that allows users to model runoff as it flows not only through the pipe network system but over roads and land.
“If the water goes out of a channel and then travels overland to some other channel, we can track that,” Manwaring explains. “If it goes out of a pipe, down a road, and back into a pipe, we can handle that. This is something that most water modelers want to know. There’s never before been an easy way of tracking that kind of flow. It’s just a more comprehensive system of tracking the water.”
US engineers are still warming up to overland flow modeling, Manwaring says, but are now realizing in greater numbers how important it is to chart runoff even in those times when it leaves a storm system’s network of pipes and channels.
“Outside the United States, this has been the practice for several years now,” he says. “Our initial offering was received very well in Australia, Japan, Korea, Malaysia, and the United Kingdom, where they [have] already been looking to do that sort of thing. Here in the United States, we’ve been a little slower to adopt that level of sophistication. In the last 12 months, especially in the last four to five months, there’s been a real waking up of the industry to the capability of two-dimensional flow models.”
It helps that two-dimensional modeling software has gradually become cheaper in the United States, Manwaring notes. The programs have also become easier to use over the years.
If these two trends continue—less expensive software and easier-to-use interfaces—the demand for hydraulic modeling software, as well as for all stormwater-related technology, should also increase at an even faster rate.
“It used to be that your typical two-dimensional modeling software was really expensive. Well, that’s not what anyone wanted to hear,” he says. “It used to be, ‘you can get good pictures, good answers, and accurate tracking of water, but it will cost you a lot of money.’ That’s not the case now.”
As an example of how xpswmm is used, Manwaring points to the city of Houston. The city is fairly flat. When a major storm hits, the water from it begins to run off and initially goes into the city’s stormwater systems—its inlet grates, pipes, and drainage channels. It’s easy for engineers to model this kind of runoff with a typical xpswmm application.
However, in more severe storms, the storm system backs up. Runoff flows out of grates and down the roads and spreads out over the flat lands of Texas. The water can flow over people’s yards and down city streets, and it can form large puddles. Where do these puddles typically form? How deep do they usually get? These are questions, Manwaring says, that a typical pipe-system modeling program can’t answer.
It’s in such heavy storms that overland modeling software such as xpswmm is useful. The program allows municipalities to track water as it leaves the storm sewer system, and then track actions necessary to prevent flooding and puddling in neighborhoods and business districts.
Rich Thornton, project manager with Fort Collins, CO–based engineering, architectural, and consulting firm, HDR, said his company has used xpswmm for the last 10 years for stormwater and combined sewer system projects.
HDR used the program in 2007 to create a citywide stormwater master plan for Boulder, CO. The company used the program’s two-dimensional analysis to identify the exact amount of flooding suffered by one particular 50-acre problem area.
“By using the software, we were able to efficiently do that analysis,” Thornton says. “Part of our job, of course, was to recommend solutions to the flooding problems. We used the two-dimensional analysis to find a solution for the city.”
That solution consisted of a new pipe system in combination with open-channel improvements. The two-dimensional analysis let HDR optimize the size of these improvements to minimize the area’s flooding problems.
“We could have done it by using other methods,” Thornton says. “But using software was the most efficient way to do it. This is a good example of some of the advancements the industry has seen in software and technology. Being able to tie this two-dimensional software to a one-dimensional pipe system conveyance type model is a neat thing.”
And if software and technology manufacturers have their say, this advancement will be far from the last to hit the stormwater industry.