Illicit Discharge Detection and Elimination
Cities develop a growing set of tools to track down sewer leaks and illegal connections.
As municipalities across the United States enact programs to detect illicit discharge—many of them to meet one of the six minimum control measures required by Phase II of the National Pollutant Discharge Elimination System (NPDES)—the challenge becomes how to do so most effectively in a cost-efficient manner.
Throughout the US, municipalities have been sleuthing the sources of pollution discharge into storm sewer systems by using a number of methods, including water sampling, dye testing, underground closed-circuit televising, smoke testing, and infrared technology.
Some US programs launched the benchmark testing of methods that are now being employed by others to meet NPDES requirements. Wayne County, MI, and Charlotte-Mecklenburg County, NC, have had long-standing water-quality programs.
Charlotte-Mecklenburg has had a water-quality program in place since 1970. "It's probably one of the oldest local programs in the country," says Rusty Rozelle, water-quality program manager.
So too is that of the Wayne County Department of Environment's Watershed Management Division. The division's Illicit Connection and Discharge Elimination Program (IDEP) has been operative for more than 15 years.
Wayne County
Susan Thompson, an environmental specialist with the Wayne County Department of Environment, points out that the program has enabled the division's staff to develop increasing levels of expertise through its experimentation with a variety of methods in detecting illicit connections and discharges, including dye testing, underground closed-circuit televising, water sampling, and smoke testing. The division attributes its success to experimentation, trial and error, and luck.
The county's success with improvement efforts in Newburgh Lake near the Middle Rouge River provided the inspiration to extend those efforts to an open branch farther downstream. Subsequent water-quality monitoring showed repeatedly high levels of E. coli at a nearby dam.
"That's what started the investigation," Thompson says. "Basically we had the storm sewer maps, and coming in below the dam was a 9-foot outfall, plus all the storm sewers coming into that. We had a lot of surface area to cover, so that's where we started.
"The good news is just this summer on the Newburgh Lake impoundment—which is upstream in the river—some of the fish advisories that were in place have been lifted," she says. "So there are activities there and people who fish routinely."
Overall the Rouge River, a tributary of the Detroit River, has provided many "teaching moments" to those studying the effectiveness of some of the techniques used in the field to determine illicit discharges. Located in southeast Michigan, the river takes in about 467 mi.2 and is a highly urbanized watershed serving 1.5 million residents in 48 municipalities.
It is identified as an area of concern by the International Joint Commission, an independent organization with members appointed by the US and Canada—as well as by local residents—that advises both governments on boundary water issues. Michigan's state government created a series of Remedial Action Plans to address specific pollutants of the state surface waters, such as combined sewer overflows, industrial pollutant discharges, and nonpoint-source pollution.
In 1987, Wayne County initiated a program for reducing pollutant loadings to the Rouge River that would detect and eliminate illicit discharges and improper or illegal connections to Wayne County storm sewers and surface waters.
Between that time and December 2002, Wayne County inspected some 5,420 commercial, retail, and industrial facilities for illicit connections, with field staff discovering 1,433 illicit connections at 370 facilities.
"We were looking at nonpoint-source pollution from stormwater runoff and then [at] illicit discharges that are collected on impervious surfaces," Thompson says. "We look at hot spots in terms of overall investigations. If we're sampling at numerous times and there are repeated events, or if we know of complaints or have some previous water-quality data on an area, that would lead us to fly a hazard flag in certain areas.
"We started trying to isolate different laterals coming off the sewers. You determine if you've got things coming in off of this particular line or not, and you can start working your way up by process of elimination."
This discovery and elimination of the connections prevents Wayne County's surface waters from hosting an annual estimated 200 million gal. of polluted water, 76,000 lb. of biological oxygen demand (a measure of waste concentration), 287,000 lb. of total suspended solids, and 5,000 lb. of total phosphorous.
In beginning an investigation for illicit discharges, Wayne County determines the location of hot spots in the targeted area through outfall surveys, referrals from other departments, known areas of concern, water-quality data reviews, and complaint responses.
Detection Methods
Wayne County relies on several different types of investigative methods:
- Intensive water sampling involves some samples taken at many locations and many samples taken at a single location.
- Dye testing, or the placing of tracing dyes in a sewer system, determines the path of the flow. Wayne County extensively uses dye testing for illicit connection detection. Field staff walk through the facility to determine the location of plumbing fixtures and to observe interior and exterior housekeeping practices. Tracing dye is placed into plumbing fixtures and flushed through the system with running water. A county employee stationed at the sanitary manhole downstream of the tested facility alerts the team member inside the building when the dye is observed in the sanitary sewer. Alternate dye colors are used to test multiple fixtures simultaneously. If dye is not observed in the sanitary sewer, the dye test is repeated until it is confirmed in the sanitary sewer, storm sewer, or surface water body. If the dye from a fixture inside the building is discovered in a location other than a sanitary sewer, it is an illicit connection.
- Underground televising involves placement of a self-propelled camera into a sewer line while an operator observes live footage of the line's condition.
- Smoke testing involves introducing a nontoxic smoke into a storm sewer. An illicit tap is suspected if the smoke is observed in a sewer vent from a building.
- "Walk-in" surveys determine problems with large-diameter pipes. In one instance in Wayne County, a rope with oil-absorbent pads tied at measured intervals was placed into a storm sewer manhole located upstream of a facility where a leaky underground oil storage tank was suspected. The rope was pulled out of the sewer and measured to where oil was present. The distance was walked off on the surface, with investigators standing in front of the suspected facility, whose owner admitted to the problem and repaired the leaky tank.
Dye testing was the starting point for Wayne County, Thompson says. "Then we branched out into different methods. Other communities will use other methods. Some of the communities in Wayne County have their own trucks and TV cameras. You might find that they rarely use dye testing. The point we make is ‘whatever works for you.'"
Charlotte-Mecklenburg‘s Rozelle recommends that any municipality starting a monitoring program "should buy a case of that dye. It's one of the best monitoring methods and one of the cheapest to do. But you've got to be careful because a small amount can color a lot of water."
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| Aerial view of the Rouge River investigation area described in the IDEP case study. |
Rozelle suggests combining the dye testing with field tests because portable field equipment can enable the worker to measure key parameters, such as conductivity, dissolved oxygen, and temperature.
To illustrate that there is no single standard operating procedure for investigating illicit discharges and connections, consider Wayne County's case study of its use of a combination of techniques with respect to a suspected problem.
One of the goals in Wayne County's IDEP is the restoration of a section of the Rouge River to canoeing quality. The sewer drainage area—located in a primarily residential area—is approximately 157 ac., which contains more than 5.5 mi. of enclosed storm sewer that drains into an outfall and more than 350 manholes. The storm sewer has one main line with many connecting branches.
"With costs, we certainly can't sample every manhole in the system," Thompson points out. "Nobody has the time or the money; it's not cost-effective to be able to sample everything. The idea was to narrow down and identify certain areas before tracking back up the pipe to try to eliminate the different laterals coming into a storm sewer."
In a water sampling study, high levels of E. coli were detected below the dam of an impoundment in the river. Samples were collected along the main line at a variety of locations, and a 0.25-mi.-long branch coming into the main line near the outfall had higher E. coli levels than the others. Confirming sampling focused on the high level areas, indicating a significant bacteria source upstream at the suspected branch. Bacterial counts at one manhole were more than 160,000 colony-forming units per 100 ml. The suspicion was that a short section of sewer line was the source of the problem because, in comparison, storm sewers from adjacent branches with similar land use had extremely low levels of E. coli.
Livonia, the city in which the testing had been taking place, agreed to televise the storm sewers. Although the camera dipped below the water at one location, no taps were found. After distributing educational pamphlets throughout the neighborhood, the city dye tested the homes along the sewer line for illicit connections, but none was found.
Subsequent sampling of the sewer line found very low levels of E. coli with repeated sampling up to two years later finding even lower E. coli levels. Government officials theorized that someone in the neighborhood owned a recreational vehicle and had been discharging its holding tank or performing some other inappropriate action into the storm sewer but had stopped doing so upon realizing it created a problem.
Charlotte-Mecklenburg County
While Wayne County has been using a variety of methods to sleuth illicit discharges and connections for years, Charlotte-Mecklenburg has added another tool to the arsenal: infrared technology.
The Charlotte-Mecklenburg County area has seven municipalities and covers 520 mi.2 with a population of 700,000 people. Charlotte is the largest municipality in the county, which cooperates with Charlotte Storm Water Services and manages the city's illicit detection program. The city holds the NPDES permit, and the county hosts several program activities Charlotte.
"All of the towns will be coming under a Phase II stormwater permit, and we're the permit holders for Phase II," Rozelle says. "We have a similar program in the towns as we do for the city. We manage the water-quality program for them. We have a staff of 29 people to cover the 520 square miles. We're involved in implementing the Phase I and Phase II programs in Charlotte-Mecklenburg County."
Rozelle says one such program is water monitoring in the streams on a quarterly basis. Identification of hot spots and the frequency of the monitoring of those spots change depending on the type of pollutants being tracked.
"We collect these samples, and we have locally established action watch levels. Some of them have state standards [while] some of them are, for example, conductivity and other parameters that don't have state standards. We've established an action level, which usually is indicative of a problem in the stream. We'll initiate follow-up activities—additional monitoring, field screening, stream walking, dye testing in storm drains, and other activities as necessary—to find the source. Then we've got the local regulations we enforce to ensure that those sources are quickly eliminated and the pollution problem is taken care of."
Dry-weather flow samplings also are conducted to survey stormwater outfalls on a regular basis. "When we encounter dry-weather flows, we collect samples for certain key parameters to identify any pollution problem. If it does indicate any one of those parameters, we follow it up to find the source and eliminate it using those ordinances," Rozelle says. "We also do stream walking where we will pick sections of streams and walk them and do a monitoring using field equipment, periodically looking for elevated parameters."
Rozelle says Charlotte-Mecklenburg's water-quality testing program employs automated real-time monitoring instruments stationed at various locations in the creeks around the county. The instruments collect data every 15 minutes, 24 hours a day, seven days a week. Testing is done for turbidity, conductivity, dissolved oxygen, temperature, and other factors.
"Those data are downloaded automatically onto a Web site, and if there is an exceeding of an action level that indicates a water-quality problem, our investigators automatically send an e-mail through the computer system, and we can respond to the site immediately and trace back to the source of the discharge," Rozelle explains, mentioning one of the flaws with water monitoring is that a sample collected manually might offer an incomplete picture, "so we've found it really helpful to have a piece of monitoring equipment in there all the time." He concedes, however, that remote sampling is expensive and requires a great deal of technology and thus might be impractical for smaller municipalities.
Citizen requests for service also trigger an investigation. "People see creeks in their backyards that are different colors or are picking up on strange smells and fish kills," Rozelle says. "We respond to those immediately, find the sources, and eliminate them."
In the Charlotte-Mecklenburg area, there are a number of sources for illicit discharges. One of the most prevalent pollutants, according to Rozelle, is bacteria.
"A lot of times, it's from sewer leaks, bathrooms, facilities improperly plumbed to storm drains, or illegal dumping," he says. "Sometimes it is human waste.
eriodically we get other types of discharges from commercial facilities—maybe from a wash bay or from some industrial facilities on occasion—where folks are either illegally plumbing into the storm drain or dumping illegally into a creek."
Charlotte-Mecklenburg has used all of the methods Wayne County has used in doing its own investigations.
"Usually the sampling will get you to the end of the pipe or—if you're lucky—in the general area where the discharge is coming from," Rozelle says. "But you can go just so far. Sometimes you might get elevated levels to the end of the pipe, and then you'd have to get a TV camera to go up into the pipe and try to find a connection; we've found a lot of them that way."
Smoke tests have proven useful to find sewer lines illicitly plumbed into the storm drain. The primary detection method Charlotte-Mecklenburg uses, however, is dye testing.
"It's so simple," Rozelle says. "You just use a biodegradable dye, and if you can find where you think the source is, then you can dye the plumbing, and of course it comes out in the storm drain or creek, and you know you've got it."
Dye testing is frequently used in conjunction with underground televising. "Maybe you'll put the TV camera up in the pipe because you've got a particular connection you're suspicious of, and you see the dye come out, and you know you've got the source," Rozelle says. "Often it's a combination of different things, and it is a lot of detective work."
Rozelle cites another example: "We had some high bacteria counts here in a creek in downtown Charlotte, in an older area of town where we're having some renovation work done. There are some older sewer lines in there, so we suspected that it was a sewer leak from one of the mains."
City utility workers dye tested and smoke tested many lines and repaired some problems they suspected as the source. But the high counts persisted.
"We worked on it for about six months, and we were still working on it when we got a call one day from a lady who was living in this new condominium complex built three months previously. She said every time it rained, the water was sucked out of her toilet," Rozelle says.
Upon investigation, it was discovered that the woman lived upstream of where the high fecal counts were occurring. "What we found out was what we suspected. They had tied her sewer line and the sewer lines of about six or seven different condominium units into the storm drain system. The water was rushing off the roof of the high-rise condominium when it rained and through the storm drain system, and then it was creating a vacuum that was sucking the water out of her toilet.
"When we investigated further, we found out that they had a 6-inch PVC pipe coming off the roof for the stormwater and a 6-inch PVC pipe for their sewer line. The pipes were side by side and the same color. When they tied into the storm drain and the sanitary sewer, they just stuck them out through the concrete, and when the plumber came to finish the plumbing work, he got the two mixed up. That was a situation where the last thing you suspected was a brand-new condominium project in a very ritzy part of town having the plumbing backwards."
Rozelle says such mix-ups have occurred on several occasions, when plumbers have made connections to the wrong pipe.
Testing a New Technology
In February 2002, Charlotte-Mecklenburg Utilities conducted a study to test alternate methods of detection along 27 mi. of stream in the Little Sugar Creek watershed. The study centered around the effectiveness of aerial infrared surveying technology from Stockton Infrared Thermographic Services' AITscan Division to isolate and identify illicit connections to the storm drain system and to point sources of pollution, such as sanitary sewer overflows, dry-weather flow from stormwater outfalls, and failed or failing septic systems and sewer collection systems. Illegal taps into stormwater drainage systems, as well as other factors, can be identified during certain times of the year by their thermal infrared signatures.
The survey pinpointed 62 heat anomalies along Little Sugar and Briar Creeks in the targeted basin. Field investigations revealed that the anomalies existed for several reasons, including a failing 15-in. sewer line and dry-weather flows to the storm drain with elevated fecal coliform bacteria levels. One anomaly was an illegal discharge to the storm drain system from a convenience store. The discharge was removed from the storm drain and tied to the sanitary sewer system.
The use of infrared thermography can help identify the flow of a liquid into another body liquid if there is a temperature difference between the two. For example, liquids flowing into a stream appear warm as compared to the surface water in a creek, a stream, a river, or a lake, particularly during cooler times of the year, because of the relative warmth of the ground a short distance below the surface.
Leaks from nearby lines often come to the surface through lateral transfer to a creek, a stream, a river, or a lakebed, or the leak might follow a slope leading down to the surface of the water. The leak areas and the warm plume of liquid joining and flowing downstream with the body of water are visible in the thermal infrared spectrum.
Key to the success of this method is the selection of the proper aircraft, camera mount, infrared imager, navigational aids, recording medium, workstation computer equipment, pilot, and crew.
"The plane flies low over Charlotte and follows the creek system," Rozelle explains. "The infrared photography is sensitive to about half a degree. They videotape the stream: Warmer water going into the stream, such as an illicit discharge, turns up as a brighter color. We are then able, using [global positioning system] coordinates, to track that down onto the ground."
Usually an image taken with an infrared camera is recorded on videotape or saved digitally to onboard hardware storage and later converted to a digital image file. Highest resolution infrared images usually are found on videotape, with printed thermographs and map data used as a reference within a report.
To find outfalls, the tape is viewed in its entirety, using pause, rewind, and slow-motion capabilities. Many hours of analysis are required for each hour of tape to complete the report. When anomalies are found, they are marked on the topographical map, and infrared thermographs are captured digitally with specially designed hardware and software. Maps and digital images are adjusted and scaled for final editing.
The testing is performed in February, when all of the leaves are off the trees and a good water picture differential can be obtained between the discharge and the creek water, Rozelle says.
With ground verification and analysis, information collected during an aerial infrared survey can accurately identify "true positive" instances of illicit discharges that were remotely identified. Field workers also can identify areas that contain priority clusters or higher concentrations of pollutants and can prepare lists of individual property addresses located within those clusters, thus meeting program requirements by heightening public awareness of illegal stream connections, septic system failures, and general water-quality issues.
The Little Sugar Creek project marks Charlotte-Mecklenburg's second use of low-level infrared photography, Rozelle says. "We have found through this process several different sewer leaks and illicit discharges that we would have never found otherwise. It's a very quick way to find those types of problems."
He says the only drawback is that testers find other matter, too. "For example, a manhole shows up as a bright color, and groundwater seepage into the creek is usually warmer, so sometimes that can show up as a brighter color. Other things can mislead you to think [they are] a discharge. But you just have to go back and follow up to make sure you're tracking down the problem."
Learning What to Look For
Training is a key component of any illicit discharge and elimination program. In 1999, the Wayne County Department of Environment's Watershed Management Division created a training program for local and regional governments responsible for locating and eliminating illicit discharges to surface waters. Not only has the division been helpful in sharing its expertise, but the collaborative efforts also have gone a long way in reducing improper discharges to surface water.
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| Field staff using a portable colorimetric test kit as a tool to screen for illicit discharges |
The training program—consistent with the IDEP requirements of the Michigan Voluntary Storm Water Permit and Phase II stormwater permit regulations—consists of five modules and two specialty training sessions.
The modules include an overview, basic investigations, advanced investigations, construction-related illicit discharges, combined basic/advanced investigations, and two specialty training sessions: "Recognizing and Reporting Illicit Discharges" and "Illicit Discharge Investigation Exercise."
It is estimated that during the first year of the training effort, 82 illicit discharges were eliminated, preventing an estimated 3.5 million gal./yr. of polluted water from entering Michigan surface waters.
Training sessions conducted by Wayne County have attracted 850 participants representing various agencies and communities throughout Michigan and two neighboring states. Wayne County determined that such a program is an effective means of transferring technology to others, sharing its expertise with other local units of government involved in stormwater management, and collaborating efforts to reduce improper discharges.
"Wayne County has been doing this for more than 15 years now, starting the program in 1987," says Thompson, adding that the pre-NPDES program was partly a response to the Rouge River Remedial Action Project, which started in the mid-1980s. "When that remedial action plan was put together, illicit connections were identified as one of the sources of pollutants [entering] the watershed."
Wayne County's training program has extended beyond county lines throughout both southeastern and western Michigan. The training program also has been shared with Minnesota.
Thompson adds that training should be an important piece of all municipalities' illicit discharge and detection programs. "Under Phase II, other communities are going to be in charge of doing these types of investigations, and it certainly helps to have the tools to be able to do the work," she says. "If you have a hot spot or a discharge coming out of an outflow, it's great to at least be able to have an idea of what to do."
Rozelle says one area that cannot be overlooked in detecting illicit discharges is public input. "We've found over the years that no matter what you do, you can't always see everything. But the best source of information is the general public."
The educational component of a water-quality program is key, he emphasizes. "We've always focused on making sure the public knows what to look for, who to call, and what to do to prevent water-quality problems. We've increased our public education budget considerably over the last five or six years, and we've seen about a 50% increase in the number of citizen calls, so we're finding more problems."
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Charlotte-Mecklenburg has about 3,000 mi. of streams and 190 mi. of shoreline. "We've got a lot of shoreline to watch, and we try to get citizens on our side and call us when they see a problem. And we get lots of calls," Rozelle says, adding that during an average year, Charlotte-Mecklenburg eliminates several hundred discharges through various methods.
Thompson says the bottom line is that there is "no cookbook or exact recipe" for illicit discharge and elimination. "It's all process of elimination, trial and error." Her advice to other municipalities is to be persistent in investigations if a problem is suspected. "You just keep looking at all of those different sources and eliminate any other factors, and those that remain must be the truth."
Author's Bio: Carol Brzozowski is a journalist living in Coral Springs, FL.
March-April 2004
Illicit Discharge Detection and Elimination
Cities develop a growing set of tools to track down sewer leaks and illegal connections.
As municipalities across the United States enact programs to detect illicit discharge—many of them to meet one of the six minimum control measures required by Phase II of the National Pollutant Discharge Elimination System (NPDES)—the challenge becomes how to do so most effectively in a cost-efficient manner.Throughout the US, municipalities have been sleuthing the sources of pollution discharge into storm sewer systems by using a number of methods, including water sampling, dye testing, underground closed-circuit televising, smoke testing, and infrared technology.
Some US programs launched the benchmark testing of methods that are now being employed by others to meet NPDES requirements. Wayne County, MI, and Charlotte-Mecklenburg County, NC, have had long-standing water-quality programs.
Charlotte-Mecklenburg has had a water-quality program in place since 1970. "It's probably one of the oldest local programs in the country," says Rusty Rozelle, water-quality program manager.
So too is that of the Wayne County Department of Environment's Watershed Management Division. The division's Illicit Connection and Discharge Elimination Program (IDEP) has been operative for more than 15 years.
Wayne County
Susan Thompson, an environmental specialist with the Wayne County Department of Environment, points out that the program has enabled the division's staff to develop increasing levels of expertise through its experimentation with a variety of methods in detecting illicit connections and discharges, including dye testing, underground closed-circuit televising, water sampling, and smoke testing. The division attributes its success to experimentation, trial and error, and luck.
The county's success with improvement efforts in Newburgh Lake near the Middle Rouge River provided the inspiration to extend those efforts to an open branch farther downstream. Subsequent water-quality monitoring showed repeatedly high levels of E. coli at a nearby dam.
"That's what started the investigation," Thompson says. "Basically we had the storm sewer maps, and coming in below the dam was a 9-foot outfall, plus all the storm sewers coming into that. We had a lot of surface area to cover, so that's where we started.
"The good news is just this summer on the Newburgh Lake impoundment—which is upstream in the river—some of the fish advisories that were in place have been lifted," she says. "So there are activities there and people who fish routinely."
Overall the Rouge River, a tributary of the Detroit River, has provided many "teaching moments" to those studying the effectiveness of some of the techniques used in the field to determine illicit discharges. Located in southeast Michigan, the river takes in about 467 mi.2 and is a highly urbanized watershed serving 1.5 million residents in 48 municipalities.
It is identified as an area of concern by the International Joint Commission, an independent organization with members appointed by the US and Canada—as well as by local residents—that advises both governments on boundary water issues. Michigan's state government created a series of Remedial Action Plans to address specific pollutants of the state surface waters, such as combined sewer overflows, industrial pollutant discharges, and nonpoint-source pollution.
In 1987, Wayne County initiated a program for reducing pollutant loadings to the Rouge River that would detect and eliminate illicit discharges and improper or illegal connections to Wayne County storm sewers and surface waters.
Between that time and December 2002, Wayne County inspected some 5,420 commercial, retail, and industrial facilities for illicit connections, with field staff discovering 1,433 illicit connections at 370 facilities.
"We were looking at nonpoint-source pollution from stormwater runoff and then [at] illicit discharges that are collected on impervious surfaces," Thompson says. "We look at hot spots in terms of overall investigations. If we're sampling at numerous times and there are repeated events, or if we know of complaints or have some previous water-quality data on an area, that would lead us to fly a hazard flag in certain areas.
"We started trying to isolate different laterals coming off the sewers. You determine if you've got things coming in off of this particular line or not, and you can start working your way up by process of elimination."
This discovery and elimination of the connections prevents Wayne County's surface waters from hosting an annual estimated 200 million gal. of polluted water, 76,000 lb. of biological oxygen demand (a measure of waste concentration), 287,000 lb. of total suspended solids, and 5,000 lb. of total phosphorous.
In beginning an investigation for illicit discharges, Wayne County determines the location of hot spots in the targeted area through outfall surveys, referrals from other departments, known areas of concern, water-quality data reviews, and complaint responses.
Detection Methods
Wayne County relies on several different types of investigative methods:
- Intensive water sampling involves some samples taken at many locations and many samples taken at a single location.
- Dye testing, or the placing of tracing dyes in a sewer system, determines the path of the flow. Wayne County extensively uses dye testing for illicit connection detection. Field staff walk through the facility to determine the location of plumbing fixtures and to observe interior and exterior housekeeping practices. Tracing dye is placed into plumbing fixtures and flushed through the system with running water. A county employee stationed at the sanitary manhole downstream of the tested facility alerts the team member inside the building when the dye is observed in the sanitary sewer. Alternate dye colors are used to test multiple fixtures simultaneously. If dye is not observed in the sanitary sewer, the dye test is repeated until it is confirmed in the sanitary sewer, storm sewer, or surface water body. If the dye from a fixture inside the building is discovered in a location other than a sanitary sewer, it is an illicit connection.
- Underground televising involves placement of a self-propelled camera into a sewer line while an operator observes live footage of the line's condition.
- Smoke testing involves introducing a nontoxic smoke into a storm sewer. An illicit tap is suspected if the smoke is observed in a sewer vent from a building.
- "Walk-in" surveys determine problems with large-diameter pipes. In one instance in Wayne County, a rope with oil-absorbent pads tied at measured intervals was placed into a storm sewer manhole located upstream of a facility where a leaky underground oil storage tank was suspected. The rope was pulled out of the sewer and measured to where oil was present. The distance was walked off on the surface, with investigators standing in front of the suspected facility, whose owner admitted to the problem and repaired the leaky tank.
Dye testing was the starting point for Wayne County, Thompson says. "Then we branched out into different methods. Other communities will use other methods. Some of the communities in Wayne County have their own trucks and TV cameras. You might find that they rarely use dye testing. The point we make is ‘whatever works for you.'"
Charlotte-Mecklenburg‘s Rozelle recommends that any municipality starting a monitoring program "should buy a case of that dye. It's one of the best monitoring methods and one of the cheapest to do. But you've got to be careful because a small amount can color a lot of water."
|
| Aerial view of the Rouge River investigation area described in the IDEP case study. |
Rozelle suggests combining the dye testing with field tests because portable field equipment can enable the worker to measure key parameters, such as conductivity, dissolved oxygen, and temperature.
To illustrate that there is no single standard operating procedure for investigating illicit discharges and connections, consider Wayne County's case study of its use of a combination of techniques with respect to a suspected problem.
One of the goals in Wayne County's IDEP is the restoration of a section of the Rouge River to canoeing quality. The sewer drainage area—located in a primarily residential area—is approximately 157 ac., which contains more than 5.5 mi. of enclosed storm sewer that drains into an outfall and more than 350 manholes. The storm sewer has one main line with many connecting branches.
"With costs, we certainly can't sample every manhole in the system," Thompson points out. "Nobody has the time or the money; it's not cost-effective to be able to sample everything. The idea was to narrow down and identify certain areas before tracking back up the pipe to try to eliminate the different laterals coming into a storm sewer."
In a water sampling study, high levels of E. coli were detected below the dam of an impoundment in the river. Samples were collected along the main line at a variety of locations, and a 0.25-mi.-long branch coming into the main line near the outfall had higher E. coli levels than the others. Confirming sampling focused on the high level areas, indicating a significant bacteria source upstream at the suspected branch. Bacterial counts at one manhole were more than 160,000 colony-forming units per 100 ml. The suspicion was that a short section of sewer line was the source of the problem because, in comparison, storm sewers from adjacent branches with similar land use had extremely low levels of E. coli.
Livonia, the city in which the testing had been taking place, agreed to televise the storm sewers. Although the camera dipped below the water at one location, no taps were found. After distributing educational pamphlets throughout the neighborhood, the city dye tested the homes along the sewer line for illicit connections, but none was found.
Subsequent sampling of the sewer line found very low levels of E. coli with repeated sampling up to two years later finding even lower E. coli levels. Government officials theorized that someone in the neighborhood owned a recreational vehicle and had been discharging its holding tank or performing some other inappropriate action into the storm sewer but had stopped doing so upon realizing it created a problem.
Charlotte-Mecklenburg County
While Wayne County has been using a variety of methods to sleuth illicit discharges and connections for years, Charlotte-Mecklenburg has added another tool to the arsenal: infrared technology.
The Charlotte-Mecklenburg County area has seven municipalities and covers 520 mi.2 with a population of 700,000 people. Charlotte is the largest municipality in the county, which cooperates with Charlotte Storm Water Services and manages the city's illicit detection program. The city holds the NPDES permit, and the county hosts several program activities Charlotte.
"All of the towns will be coming under a Phase II stormwater permit, and we're the permit holders for Phase II," Rozelle says. "We have a similar program in the towns as we do for the city. We manage the water-quality program for them. We have a staff of 29 people to cover the 520 square miles. We're involved in implementing the Phase I and Phase II programs in Charlotte-Mecklenburg County."
Rozelle says one such program is water monitoring in the streams on a quarterly basis. Identification of hot spots and the frequency of the monitoring of those spots change depending on the type of pollutants being tracked.
"We collect these samples, and we have locally established action watch levels. Some of them have state standards [while] some of them are, for example, conductivity and other parameters that don't have state standards. We've established an action level, which usually is indicative of a problem in the stream. We'll initiate follow-up activities—additional monitoring, field screening, stream walking, dye testing in storm drains, and other activities as necessary—to find the source. Then we've got the local regulations we enforce to ensure that those sources are quickly eliminated and the pollution problem is taken care of."
Dry-weather flow samplings also are conducted to survey stormwater outfalls on a regular basis. "When we encounter dry-weather flows, we collect samples for certain key parameters to identify any pollution problem. If it does indicate any one of those parameters, we follow it up to find the source and eliminate it using those ordinances," Rozelle says. "We also do stream walking where we will pick sections of streams and walk them and do a monitoring using field equipment, periodically looking for elevated parameters."
Rozelle says Charlotte-Mecklenburg's water-quality testing program employs automated real-time monitoring instruments stationed at various locations in the creeks around the county. The instruments collect data every 15 minutes, 24 hours a day, seven days a week. Testing is done for turbidity, conductivity, dissolved oxygen, temperature, and other factors.
"Those data are downloaded automatically onto a Web site, and if there is an exceeding of an action level that indicates a water-quality problem, our investigators automatically send an e-mail through the computer system, and we can respond to the site immediately and trace back to the source of the discharge," Rozelle explains, mentioning one of the flaws with water monitoring is that a sample collected manually might offer an incomplete picture, "so we've found it really helpful to have a piece of monitoring equipment in there all the time." He concedes, however, that remote sampling is expensive and requires a great deal of technology and thus might be impractical for smaller municipalities.
Citizen requests for service also trigger an investigation. "People see creeks in their backyards that are different colors or are picking up on strange smells and fish kills," Rozelle says. "We respond to those immediately, find the sources, and eliminate them."
In the Charlotte-Mecklenburg area, there are a number of sources for illicit discharges. One of the most prevalent pollutants, according to Rozelle, is bacteria.
"A lot of times, it's from sewer leaks, bathrooms, facilities improperly plumbed to storm drains, or illegal dumping," he says. "Sometimes it is human waste.
eriodically we get other types of discharges from commercial facilities—maybe from a wash bay or from some industrial facilities on occasion—where folks are either illegally plumbing into the storm drain or dumping illegally into a creek."
Charlotte-Mecklenburg has used all of the methods Wayne County has used in doing its own investigations.
"Usually the sampling will get you to the end of the pipe or—if you're lucky—in the general area where the discharge is coming from," Rozelle says. "But you can go just so far. Sometimes you might get elevated levels to the end of the pipe, and then you'd have to get a TV camera to go up into the pipe and try to find a connection; we've found a lot of them that way."
Smoke tests have proven useful to find sewer lines illicitly plumbed into the storm drain. The primary detection method Charlotte-Mecklenburg uses, however, is dye testing.
"It's so simple," Rozelle says. "You just use a biodegradable dye, and if you can find where you think the source is, then you can dye the plumbing, and of course it comes out in the storm drain or creek, and you know you've got it."
Dye testing is frequently used in conjunction with underground televising. "Maybe you'll put the TV camera up in the pipe because you've got a particular connection you're suspicious of, and you see the dye come out, and you know you've got the source," Rozelle says. "Often it's a combination of different things, and it is a lot of detective work."
Rozelle cites another example: "We had some high bacteria counts here in a creek in downtown Charlotte, in an older area of town where we're having some renovation work done. There are some older sewer lines in there, so we suspected that it was a sewer leak from one of the mains."
City utility workers dye tested and smoke tested many lines and repaired some problems they suspected as the source. But the high counts persisted.
"We worked on it for about six months, and we were still working on it when we got a call one day from a lady who was living in this new condominium complex built three months previously. She said every time it rained, the water was sucked out of her toilet," Rozelle says.
Upon investigation, it was discovered that the woman lived upstream of where the high fecal counts were occurring. "What we found out was what we suspected. They had tied her sewer line and the sewer lines of about six or seven different condominium units into the storm drain system. The water was rushing off the roof of the high-rise condominium when it rained and through the storm drain system, and then it was creating a vacuum that was sucking the water out of her toilet.
"When we investigated further, we found out that they had a 6-inch PVC pipe coming off the roof for the stormwater and a 6-inch PVC pipe for their sewer line. The pipes were side by side and the same color. When they tied into the storm drain and the sanitary sewer, they just stuck them out through the concrete, and when the plumber came to finish the plumbing work, he got the two mixed up. That was a situation where the last thing you suspected was a brand-new condominium project in a very ritzy part of town having the plumbing backwards."
Rozelle says such mix-ups have occurred on several occasions, when plumbers have made connections to the wrong pipe.
Testing a New Technology
In February 2002, Charlotte-Mecklenburg Utilities conducted a study to test alternate methods of detection along 27 mi. of stream in the Little Sugar Creek watershed. The study centered around the effectiveness of aerial infrared surveying technology from Stockton Infrared Thermographic Services' AITscan Division to isolate and identify illicit connections to the storm drain system and to point sources of pollution, such as sanitary sewer overflows, dry-weather flow from stormwater outfalls, and failed or failing septic systems and sewer collection systems. Illegal taps into stormwater drainage systems, as well as other factors, can be identified during certain times of the year by their thermal infrared signatures.
The survey pinpointed 62 heat anomalies along Little Sugar and Briar Creeks in the targeted basin. Field investigations revealed that the anomalies existed for several reasons, including a failing 15-in. sewer line and dry-weather flows to the storm drain with elevated fecal coliform bacteria levels. One anomaly was an illegal discharge to the storm drain system from a convenience store. The discharge was removed from the storm drain and tied to the sanitary sewer system.
The use of infrared thermography can help identify the flow of a liquid into another body liquid if there is a temperature difference between the two. For example, liquids flowing into a stream appear warm as compared to the surface water in a creek, a stream, a river, or a lake, particularly during cooler times of the year, because of the relative warmth of the ground a short distance below the surface.
Leaks from nearby lines often come to the surface through lateral transfer to a creek, a stream, a river, or a lakebed, or the leak might follow a slope leading down to the surface of the water. The leak areas and the warm plume of liquid joining and flowing downstream with the body of water are visible in the thermal infrared spectrum.
Key to the success of this method is the selection of the proper aircraft, camera mount, infrared imager, navigational aids, recording medium, workstation computer equipment, pilot, and crew.
"The plane flies low over Charlotte and follows the creek system," Rozelle explains. "The infrared photography is sensitive to about half a degree. They videotape the stream: Warmer water going into the stream, such as an illicit discharge, turns up as a brighter color. We are then able, using [global positioning system] coordinates, to track that down onto the ground."
Usually an image taken with an infrared camera is recorded on videotape or saved digitally to onboard hardware storage and later converted to a digital image file. Highest resolution infrared images usually are found on videotape, with printed thermographs and map data used as a reference within a report.
To find outfalls, the tape is viewed in its entirety, using pause, rewind, and slow-motion capabilities. Many hours of analysis are required for each hour of tape to complete the report. When anomalies are found, they are marked on the topographical map, and infrared thermographs are captured digitally with specially designed hardware and software. Maps and digital images are adjusted and scaled for final editing.
The testing is performed in February, when all of the leaves are off the trees and a good water picture differential can be obtained between the discharge and the creek water, Rozelle says.
With ground verification and analysis, information collected during an aerial infrared survey can accurately identify "true positive" instances of illicit discharges that were remotely identified. Field workers also can identify areas that contain priority clusters or higher concentrations of pollutants and can prepare lists of individual property addresses located within those clusters, thus meeting program requirements by heightening public awareness of illegal stream connections, septic system failures, and general water-quality issues.
The Little Sugar Creek project marks Charlotte-Mecklenburg's second use of low-level infrared photography, Rozelle says. "We have found through this process several different sewer leaks and illicit discharges that we would have never found otherwise. It's a very quick way to find those types of problems."
He says the only drawback is that testers find other matter, too. "For example, a manhole shows up as a bright color, and groundwater seepage into the creek is usually warmer, so sometimes that can show up as a brighter color. Other things can mislead you to think [they are] a discharge. But you just have to go back and follow up to make sure you're tracking down the problem."
Learning What to Look For
Training is a key component of any illicit discharge and elimination program. In 1999, the Wayne County Department of Environment's Watershed Management Division created a training program for local and regional governments responsible for locating and eliminating illicit discharges to surface waters. Not only has the division been helpful in sharing its expertise, but the collaborative efforts also have gone a long way in reducing improper discharges to surface water.
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| Field staff using a portable colorimetric test kit as a tool to screen for illicit discharges |
The training program—consistent with the IDEP requirements of the Michigan Voluntary Storm Water Permit and Phase II stormwater permit regulations—consists of five modules and two specialty training sessions.
The modules include an overview, basic investigations, advanced investigations, construction-related illicit discharges, combined basic/advanced investigations, and two specialty training sessions: "Recognizing and Reporting Illicit Discharges" and "Illicit Discharge Investigation Exercise."
It is estimated that during the first year of the training effort, 82 illicit discharges were eliminated, preventing an estimated 3.5 million gal./yr. of polluted water from entering Michigan surface waters.
Training sessions conducted by Wayne County have attracted 850 participants representing various agencies and communities throughout Michigan and two neighboring states. Wayne County determined that such a program is an effective means of transferring technology to others, sharing its expertise with other local units of government involved in stormwater management, and collaborating efforts to reduce improper discharges.
"Wayne County has been doing this for more than 15 years now, starting the program in 1987," says Thompson, adding that the pre-NPDES program was partly a response to the Rouge River Remedial Action Project, which started in the mid-1980s. "When that remedial action plan was put together, illicit connections were identified as one of the sources of pollutants [entering] the watershed."
Wayne County's training program has extended beyond county lines throughout both southeastern and western Michigan. The training program also has been shared with Minnesota.
Thompson adds that training should be an important piece of all municipalities' illicit discharge and detection programs. "Under Phase II, other communities are going to be in charge of doing these types of investigations, and it certainly helps to have the tools to be able to do the work," she says. "If you have a hot spot or a discharge coming out of an outflow, it's great to at least be able to have an idea of what to do."
Rozelle says one area that cannot be overlooked in detecting illicit discharges is public input. "We've found over the years that no matter what you do, you can't always see everything. But the best source of information is the general public."
The educational component of a water-quality program is key, he emphasizes. "We've always focused on making sure the public knows what to look for, who to call, and what to do to prevent water-quality problems. We've increased our public education budget considerably over the last five or six years, and we've seen about a 50% increase in the number of citizen calls, so we're finding more problems."
Charlotte-Mecklenburg has about 3,000 mi. of streams and 190 mi. of shoreline. "We've got a lot of shoreline to watch, and we try to get citizens on our side and call us when they see a problem. And we get lots of calls," Rozelle says, adding that during an average year, Charlotte-Mecklenburg eliminates several hundred discharges through various methods.
Thompson says the bottom line is that there is "no cookbook or exact recipe" for illicit discharge and elimination. "It's all process of elimination, trial and error." Her advice to other municipalities is to be persistent in investigations if a problem is suspected. "You just keep looking at all of those different sources and eliminate any other factors, and those that remain must be the truth."