A geographic information system (GIS) is an organized collection of hardware, software, and geographic data that allows users to efficiently capture, update, manipulate, analyze, and display a variety of information regarding a specific location.
The American Society of Civil Engineers (ASCE) has described GIS as one of the most exciting and beneficial technologies available to stormwater managers. The ASCE identified the primary GIS applications relevant to water management as the “four Ms”: mapping, monitoring, modeling, and maintenance. A variety of software applications, many modeled on the US EPA’s Storm Water Management Model (SWMM) engine, are available to assist municipalities in their stormwater work.
Lots of Bells and Whistles
XPSWMM, from XP Software, is a software package for modeling stormwater and wastewater flows. Steve Godfrey, a senior associate in the infrastructure management division of Woolpert Inc., says, “It’s basically a link-node diagram to simulate open-channel and closed conduit flooding, and you can also add a two-dimensional element for surface flooding. It is able to simulate both belowground and aboveground flooding, and I use it for stormwater purposes. I use it to analyze big drainage systems, and sometimes to design a small site development, where you’re modeling some pipes in the development and having to size and model a pond, to see what kind of performance it gets.”
Godfrey has developed stormwater models in a number of locations around the country, some covering areas as large as 150 square miles, although much of his work involves smaller projects in the 1- to 10-square-mile range.
He has been using XPSWMM software for about 15 years. “It’s got a good GIS background. You’re able to pull in GIS layers, aerial backgrounds, and pictures,” he says. “You can build most of your stuff within the interface. Sometimes we’ll have GIS data, and we’ll be able to manipulate our databases and GIS. We’ll import that data into SWMM, and then have to do a little more cleanup, making it more model-friendly because you have to simulate the real world and fill in the little gaps. Then you’ll export that data back into GIS to do all your maps, and to do other analysis. But XPSWMM will handle both open- and closed-channel systems, pumps, and a lot of special stuff, where some other software is just open-channel or just pipes.”
Godfrey has worked with a series of updated versions of the software. “Most of the versions look very similar, but they’ve added new features,” he notes. “They’re always trying to maintain backwards compatibility with older versions, so there are a lot of configuration keys that say ‘use this option that was available in 1997’, or ‘turn this option off’ because we now do it in a different way.”
Regarding software support, “When you’re purchasing the software, you’re signing up for an annual maintenance,” says Godfrey, “and that includes support.” He notes that the company has a Web site where users can submit questions, and it responds on the site or by phone.
He finds that reliability of the modeling system has been good, but users must be ready to deal with a number of variables. “There are so many ways you can set the model up, but if you’re using sound engineering parameters and judgment, you should get a pretty reliable answer. There are a lot of assumptions—you’re trying to simulate what happens in the real world, and the link node diagram is one-dimensional and quasi-2D [two-dimensional], but there are a lot of factors that take place with water runoff and the level of detail. Are you modeling every single inlet in a parking lot, or are you modeling just the trunk line? Do you model every single BMP [best management practice] in a watershed, or are you modeling only the big BMPs, the big lakes, and ponds?”
Fortunately, most of these specifications are determined at the start of a project, but Godfrey notes that data can be modified even after the model has been built. “There are some models, some software packages out there, where you can import data only at the very beginning. You can’t import and add to it, whereas this software package allows you to do that. I think, generally, XPSWMM does a good job of being able to do all the bells and whistles and computations and still have a pretty good user interface.”
New Jersey Motorsports Park
The initial phase of the 700-acre New Jersey Motorsports Park, in Millville, NJ, opened in the summer of 2008. Stormwater management of the facility has involved the movement of approximately 400,000 cubic yards of material as part of the creation of six infiltration basins. In addition to the basins, the project employs low-impact development techniques for pretreatment of stormwater runoff prior to reaching the basins.
Because of the property’s proximity to Millville Airport, the project required Federal Aviation Administration (FAA) approval. FAA regulations require that all stormwater management basins be designed in such a manner that they do not attract waterfowl, and they must drain completely within 48 hours.
One of the challenges was to determine the proper sizing of the six infiltration basins without impacting the property’s racetrack. In addition, it was necessary to pipe a large drainage ditch that traverses nearly the entire width of the property. The drainage ditch conveys 108 acres of runoff from the airport and needed 1,760 linear feet of 84-inch culvert.
To assist in the design of the project, a variety of Bentley software products were used. StormCAD was used to size approximately 16,000 linear feet of storm pipe, HEC-RAS and FlowMaster were utilized to design the 84-inch culvert, and PondPack helped in the design of the six infiltration basins.
An interesting challenge is that the project was required to meet conflicting requirements of both the New Jersey Department of Environmental Protection (NJDEP) and the FAA. On the one hand, to meet the groundwater recharge requirements of NJDEP, stormwater needs to remain onsite and slowly percolate into the ground. On the other, as noted above, the FAA requires that stormwater basins completely drain within 48 hours to deter waterfowl from congregating. Detailed infiltration calculations were required to demonstrate that the requirements of both regulatory agencies were met. This was accomplished via the PondPack program.
“What If” Scenarios
InfoSWMM is a comprehensive simulation model used for the management of urban stormwater and wastewater collection systems. It can be used to model rainfall runoff for single events or as a continuous long-term simulation of runoff.
Adam Simonsen of MWH Soft, producer of the InfoSWMM package, says that with this software, “You can build a very detailed network of your stormwater system. It includes a hydraulic component, in terms of being able to calculate your amount of flow, velocity, and depth of water through the pipes in the system, as well as a hydrologic component, in terms of being able to take the rainfall and being able to load that into the system.
“What they allow a stormwater management agency to do is to model a whole series of ‘what if’ scenarios,” he continues. “For example, based on different types of rainfall events, how is the system going to react? Where might I have flooding in the system? Where will I have pipes that are flowing full? It will model all those scenarios and will potentially allow you to find ways to optimize both the operation and the design of your system.”
Simonsen notes the level of support offered to users of the software. “Our technical support staff is actually almost 100% staffed by engineers that have done this kind of work, in one fashion or another. They’ve either worked as a consulting engineer or directly for a utility. So we’re able to teach people the basics on how to use the software, and we can also give them a little higher level expertise in terms of how they might approach different modeling techniques.” InfoSWMM is based, again, on the EPA SWMM engine with added tools.
Simonsen described a typical scenario in which stormwater managers might utilize the program to obtain some budget efficiencies. “If you’re faced with a system where you have flooding and you’re not able to manage the amount of rainfall that you’re getting, you need to have a way to effect improvements in that system. There can literally be dozens of different ways you might improve the system. The software allows you to design and model a lot of those and look at all of those alternatives, then judge which is going to be the most cost-effective, or the most viable solution that you can actually implement.
“Solutions might include adding an additional outfall somewhere in the system, or maybe upsizing pipe or designing retention basins to be able to handle particularly large events,” he adds.
Falmouth Management Plan
Falmouth, ME, (population 11,000) covers approximately 32 miles and stretches from the coastline to inland rural areas. The town has prepared a five-year stormwater management plan, and the state Department of Environmental Protection requires regular updates on the community’s implementation of stormwater improvements. Falmouth is regulated under the Phase II National Pollutant Discharge Elimination System (NPDES) program.
Jay Reynolds, public works director for Falmouth, has identified a number of goals for the stormwater system. “We are looking to perform better asset management,” he says, “as well as identifying potential failures, establishing a proactive maintenance and repair program, tracking each asset’s repairs, establishing lifecycle and replacement schedules, and updating attributes with in-house town staff.”
To assist in the process, Falmouth has been using VUEWorks software since April 2009. It replaced a database that was used for work orders, and it augments the city’s existing GIS software. “We are in the early stages of using VUEWorks in the asset management of our stormwater system,” says Reynolds. “It has already improved our decision-making with regard to workflow and prioritization.”
According to Reynolds, “Falmouth will be using the software to assist in our road construction and paving programs. We are currently acquiring pavement condition indexing data, which will then be used in the ‘condition’ module. This module will assist in identifying and prioritizing pavement overlays, road rebuilds, and reconstruction projects. It will also help with establishing budget needs.”
As a relatively new user of the software, Reynolds was pleased with its ease of implementation. “The software is very easy to use. Because staff is trained in the GIS/map environment, and because VUEWorks is map-driven, it was an easy transition.”
Critical Real-Time Data
As a major rainstorm was blanketing southern California, the Los Angeles County Department of Public Works (LACDPW) lost the use of its primary ALERT repeater atop Mount Wilson. As a result, it had almost no access to critical real-time data for flood control operations.
Following this episode, LACDPW resolved to increase redundancy and installed a series of satellite concentrators at its transmission sites. The concentrators, supplied by OneRain, were set up at each of the five ALERT repeater sites in the region. The work paid off quickly—within weeks of the installation, another storm disabled one of the other ALERT repeaters, but the satellite data was unaffected, and no data was lost.
As part of the backup system, LACDPW also uses OneRain’s Contrail Web program. This software allows authorized users to access real-time data from any computer with Internet access, and comes equipped with a sophisticated alarm and notification system.
Users of the program can create custom rules to determine when an alarm is triggered, based on input from sensors throughout the network. When the alarm is triggered, one or more people will be notified by e-mail or text message.
Contrail also offers multiple reports that allow users to monitor the performance of their sensors. This permits the identification of failing sensors at an early stage.
Pittsburgh-Area Stormwater Management
In 1997, the US EPA and the US Department of Justice threatened enormous penalties against dozens of communities comprising the Allegheny County (PA) Sanitary Authority (ALCOSAN) service area because of sewer-related violations of the federal Clean Water Act.
In response, ALCOSAN and the Allegheny County Health Department joined forces to create the 3 Rivers Wet Weather Demonstration Program (3RWW). According to 3RWW, “The organization’s ultimate goal is to improve Allegheny County’s water resources by helping municipalities find a long-term, cost-effective sustainable solution to the region’s problem. In turn, 3RWW plans to share its model to benefit municipalities throughout the United States facing the same challenges in overcoming wet weather overflows.”
In 2001, 3RWW created a calibrated radar rainfall system to assist communities in the ALCOSAN service area in designing cost-effective sewer rehabilitation projects and long-term maintenance plans. The following year, 3RWW expanded the system to cover each of the 130 Allegheny County municipalities and to provide real-time rainfall data.
John Schombert, executive director of 3RWW, explains that RainVieux software is coupled with NEXRAD radar and strategically placed rain gauges throughout the county to yield critical data. “We run the rain gauge network itself, the on-the-ground field data collection system. We have 33 rain gauges covering about 700 square miles. Each of the gauges is telemetered with the same radio bands as the weather service. The data is telemetered here in the office and by Internet sent to Vieux for processing.
“With those 33 gauges,” he continues, “we can create the equivalent of a little over 2,200 one-square-kilometer pixel virtual rain gauges across the county. It’s terrific for the engineers and the modelers, the stormwater planners, because it really shows the variation of rainfall across the region. We’re at the beginning of a lot of stormwater modeling, or rainfall modeling, to model storm systems and the sanitary and combined sewer system.”
Schombert adds, “It has turned out to be a very valuable tool in validating flow data and creating much more precise computer models of the solutions. We can put more data into the system and try different alternatives for each sewer system to see what works and where we get the most bang for the buck. That kind of value wouldn’t be here if we didn’t have the sophistication of this calibrated radar rainfall system.”
Before turning to the Vieux software, 3RWW had a less reliable system in place. “We started out with another company, with a much cruder application,” says Schombert. “We had telephone modems at each of the gauges, and they would call up every 15 minutes, and basically download all of their information, whether it was raining or not. About four years ago, we got a grant from the National Weather Service to upgrade our system into their radio network, to improve the online performance of the system by about 100%. We just had a lot of downtime with the telephone issues.”
Radio communications have eliminated the downtime problems, he says. “And we can see very quickly with radios, too, that we are having a problem with a particular gauge here or there, and have the maintenance done as soon as possible.”
Schombert notes that operating and maintaining this system is a time- and labor-intensive process. “The reliability is very high, but there is a lot of maintenance involved, whether it is seasonal because of leaves and so on, or potential wind problems. We’ve even had some vandalism with the equipment—people climbing up on these things and beating the heck out of them, for no reason at all.”
A process is in place, however, for routine maintenance. “There is a level of calibration that we have to do at least annually; we try to do it twice a year. These are remote locations, so what we do now is we exchange. We put a new unit out and bring a unit back so we can calibrate it. Therefore, we don’t have to do field calibrations, which would be too difficult.”
One of the goals that Schombert has for 3RWW and the ALCOSAN service area is to consolidate management of the system. “This is a system serving almost a million people, from 83 separate municipalities,” he says. “Every town owns a pipe in this community. We are heavily pushing to consolidate the systems into regional systems. I don’t expect it to be just one, but it sure can’t be 83 any more. That’s just not a sustainable governance mechanism for the water.”
He adds, “We’re lucky that we have a lot of pipe condition information, because the consent order requires closed-circuit television inspection of all the systems. Those are pretty well done. We’ve done a huge flow-monitoring program here, during 2008 to 2009, so we’ve got pretty recent flow data that we can calibrate now with the rain gauge network. This starts to paint a picture of some pretty nasty flows coming out of some of these communities. Even those that are supposed to have separate storm and sanitary systems are very wet when it rains here. I think, as we start to sit down and look at solutions for the communities, we also have to be prepared to talk about how they’re going to capitalize and pay for this, and about operation and maintenance responsibilities.”
The RainVieux software is also helping 3RWW make recommendations for future capital improvements. Schombert explains, “Using SWMM5, the latest update of the stormwater management software the EPA put out, works really well with our data, because of the density of the data we have. Most of the time when you’re doing that kind of work, you have a rain gauge five or 10 miles away, and you’re making judgments, creating a model, and it just doesn’t work very well.
“Here, we have real-time data that is accurate with both the time and the distribution of the rainfall across the watershed, making the models work much, much better. It means you don’t have to throw out as much data. We get a lot of microbursts here in Allegheny County in the summertime. We’ll get a thunderstorm that might hit a 10- or 12-square-mile area with very little impact on surrounding communities. These are the kind of things we can see and build into the models, and you wouldn’t be able to do it if you had to depend on a rain gauge 10 miles away. A lot of data used to come from one gauge at the Pittsburgh airport, and creating models for all of Allegheny County—that just doesn’t work well.”
Schombert adds that the 3RWW Web site, www.3riverswetweather.org, makes data available to any user quite easily. “We’ve created more user-friendly ways of downloading information so that the engineers and hydrologists that use the data can see it. We put out both real-time data as it’s raining, and the system records and reports that data, and we also put out what we call first-processed data. That’s where these algorithms really come in handy in cleaning up the data. The National Weather Service radar doesn’t know the difference between a rain cloud and a big, tall water tank; it’s just a reflection. So those kinds of things have to get sorted out. It wasn’t a burden on them, and not on us. It was up to Vieux to get the system to recognize things like that.”