Identify sources of illicit discharges
Stormwater infrastructure is designed to either capture or convey surface water runoff through manmade and natural infrastructure. However, illegal contaminants can affect this process and contain potentially harmful substances. You'll use a city's stormwater utility network to investigate an illicit discharge by tracing upstream of where the contaminant was discovered.
Become familiar with the network
First, you'll download a project package with the city's stormwater utility network. You'll familiarize yourself with the network before proceeding and learn how the infrastructure is used to manage stormwater runoff.
- Download the Stormwater_Utility_Network project package.
A file named Stormwater_Utility_Network.ppkx is downloaded to your computer.
Note:
A .ppkx file is an ArcGIS Pro project package and may contain maps, data, and other files that you can open in ArcGIS Pro. Learn more about managing .ppkx files in this guide.
- Locate the downloaded file on your computer and double-click Stormwater_Utility_Network.ppkx to open it in ArcGIS Pro. If prompted, sign in with your ArcGIS account credentials.
Note:
If you don't have access to ArcGIS Pro or an ArcGIS organizational account, see options for software access.
The project contains a map that shows a stormwater utility network in Naperville, Illinois.
The lines on the map are from the Stormwater Networks layer. Each subnetwork is styled in a different color to represent the different catchments in the network. The features are scale dependent, and will disappear when zoomed in, while other layers will become visible and show the network in more detail.
To learn more about the subnetworks, you'll trace them and open their pop-ups.
- On the ribbon, click the Utility Network tab.
- In the Subnetwork group, click Find.
The Find Subnetworks pane appears. It lists the local river basin (DuPage River Basin) and each of the 13 subnetworks.
- Right-click Catchment I and choose Trace Subnetwork.
The utility network traces all of the outfalls for this catchment and selects all features belonging to the catchment on the map. If parts of the subnetwork weren't selected, it indicates they aren't connected to the catchment.
- In the Find Subnetworks pane, right-click Catchment I and choose Pop-up.
A pop-up appears, showing attribute information associated with the network.
The pop-up lists the number of catch basins, outfalls, and other features associated with the subnetwork. It also displays the length of all the subnetwork's pipes and channels.
- Close the pop-up.
Examine outfalls
To continue your exploration of the stormwater utility network, you'll examine its outfalls, or locations where stormwater is discharged into a water body, such as a stream or lake. Outfalls are an essential component of stormwater management, so they must be properly depicted in a stormwater utility network.
- On the ribbon, click the Map tab. In the Navigate group, click Bookmarks and choose Catchment I Outfall.
The map navigates to the location where Catchment I (which is still selected) drains into the DuPage River Basin (the blue line feature). Although the subnetwork is connected to the basin, they don't physically touch.
- On the ribbon, click the Utility Network tab. In the Associations group, click View.
On the map, associations between features are displayed as dashed lines.
Associations indicate nonspatial connectivity between features. In this case, the outfall of Catchment I is connected to an open channel connection point on the DuPage River Basin.
You'll verify that the catchment drains into the river by running an upstream trace, which selects all locations upstream of a specified location.
- On the Utility Network tab, in the Tools group, click the Trace button.
The Trace pane appears. When you point to the map, the pointer becomes the select tool, allowing you to choose the manhole from which you want to trace.
Before you proceed, you'll ensure snapping is turned on. Snapping makes it easier to select features on the map. Without snapping, even missing a feature by a tiny amount will cause the trace tool to not find a starting location.
- On the ribbon, click the Edit tab. In the Snapping group, ensure Snapping is highlighted, indicating it is turned on.
Note:
If the button is not highlighted, you can turn it on by clicking the button.
- On the map, click a location on the DuPage River Basin downstream of the association for Catchment I.
- In the Trace pane, click the Named Configurations tab. Select Upstream Trace.
- At the bottom of the Trace pane, click Run.
All areas upstream of the point you clicked are selected. Catchment I remains selected, indicating it correctly feeds into the DuPage River Basin.
One of the most important benefits of a stormwater utility network is the ability to accurately map the locations of outfalls and channels while enabling upstream and downstream traces. Next, you'll take a closer look at the DuPage River Basin and find the total number of outfalls that drain into it.
- At the bottom of the Trace pane, click the Find Subnetworks tab.
The Find Subnetworks pane becomes active again.
Tip:
If you closed the Find Subnetworks pane, you can reopen it by clicking the Find button in the Subnetwork group on the ribbon.
- Right-click DuPage River Basin and choose Trace Subnetwork.
The river basin is traced, though at the current map extent, you can't see it.
- Right-click DuPage River Basin and choose Zoom To.
The map zooms to the extent of the selected features. The DuPage River Basin winds throughout Naperville. All outfalls draining into the basin are selected as well.
- In the Find Subnetworks pane, right-click DuPage River Basin and choose Pop-up.
The pop-up shows that 95 outfalls drain into the river basin.
Each outfall has a specific permit associated with it. The outfalls must be periodically inspected to ensure compliance with regulations. Though you can examine a feature by clicking it on the map and looking at its attributes in a pop-up, you can also access a feature's attribute information through the Attributes pane.
- Close the pop-up.
- On the ribbon, click the Edit tab. In the Selection group, click Attributes.
The Attributes pane appears. It lists the selected features, divided by what type of feature they are. You'll investigate a pipe outlet to see whether it has a correct outfall ID and permit ID.
- Scroll through the list of features until you reach Stormwater Device : Outlet. Click Pipe Outlet: Otlt-27.
Under the list of features, the attributes for the selected feature are listed. Although the outlet is an outfall, it has no Outfall ID or Permit ID attributes.
These attribute fields can be used to store IDs for the outfall and its permit, which enables cross-departmental sharing of information and helps ensure regulatory requirements are met. If you were to find an outfall in your utility network without a permit ID, it's recommended that you take immediate action to populate that information. For the purpose of this tutorial, you won't make any changes at this time.
Investigate an illicit discharge
Part of maintaining stormwater infrastructure is regularly monitoring the system for issues, such as contaminants.
Next, you'll use the stormwater network to investigate a report of an illicit discharge. Assume that during an annual inspection, an inspector noticed a contaminant in one of the wet basins the city manages. Further investigation determined that there was a small amount of hazardous chemicals present at the site, indicating an illicit discharge.
Because the city maintains a list of all industrial customers who make use of the detected chemical, the source of the discharge was narrowed to a list of several dozen sites across the city. Now, the city wants to place equipment to monitor for illicit discharges. Using the utility network, you'll determine the ideal sites to place this equipment based on the discharge's location and its potential source locations.
- On the ribbon, click the Map tab. In the Navigate group, click Bookmarks and choose Illicit Discharge.
The map depicts a wet basin with four pipe outlets that discharge into the basin. It was in this basin the contaminant was discovered.
- At the bottom of the Attributes pane, click the Trace tab to return to the Trace pane.
Tip:
Alternatively, reopen the Trace pane from the ribbon. Click the Utility Network tab and, in the Tools group, click the Trace button.
Before you perform another trace, you need to clear the starting point you added for your previous trace.
- In the Trace pane, click the Starting Points tab. Next to Open Channel DuPage River Basin, click the delete button.
Next, you'll add starting points at each of the outlets that feed into the basin.
- On the map, click each of the four outlets (Otlt-36, Otlt-37, Otlt-193, and Otlt-194) connected to the basin.
In the Trace pane, all four outlets you clicked are listed.
- In the Trace pane, click the Named Configurations tab. Select Upstream Trace and click Run.
All features upstream of the four outlets are selected.
- On the map, zoom out and pan until you can see all the selected features.
The city's illicit discharge team can use these results to determine which customers in the selected locations use the chemicals that were detected.
For the purposes of this tutorial, assume that it's been identified that the customer at catch basin 2265 uses the detected chemical. You'll investigate this basin further.
- On the ribbon, click the Map tab. In the Navigate group, click Bookmarks and choose Catch Basin 2265.
The map shows the catch basin, which is at the far end of the upstream trace area.
Now that you know this catch basin is the source of an illicit discharge, you'll perform a downstream trace to identify where a discharge originating here may have traveled.
- In the Trace pane, click the Starting Points tab. Delete the four starting points you added previously.
- On the map, click Ctch-Bsn-2265 to add a starting point at its location.
- In the Trace pane, click the Named Configurations tab. Click Downstream Trace.
This type of trace will identify features downstream of the selected location or locations. The true extent of a discharge may vary depending on whether it occurred during dry or wet weather conditions. This model performs pessimistic analysis, meaning it treats every trace as if it occurred during a wet weather event to show the maximum possible extent of the trace.
- Click Run. On the map, zoom out and pan until you see all the selected features.
Materials from this illicit discharge can end up in several BMP sites, which are areas used to manage runoff. The materials could also end up in the river itself depending on how full the system is when the discharge occurs.
One way to monitor the discharges of this customer is to place monitoring equipment at each downstream outfall. Another option is to place monitoring equipment at the nearest storm vault to the customer.
- Return to the Catch Basin 2265 bookmark. Pan south until you see Swr-Strm-Vlt-1623.
Storm Vault 1623 is close to the customer, and because it is selected, it's downstream of them. You can instruct your crews to place monitoring equipment at this vault. Once monitoring is in place, you could then educate the customer about the risks to natural resources and fines associated with illicit discharges, while also monitoring for future incidents.
- Close the Trace, Attributes, and Find Subnetworks panes. Under the map, click the Deselect all currently selected features button.
The selection is cleared.
- On the Quick Access Toolbar, click the Save Project button.
You've used tracing capabilities on the stormwater utility network to narrow down potential sources for illicit discharges based on reports from the field and identify any potential infrastructure that may have been affected by the contaminants.
Edit the network
As new infrastructure is built, it's important to regularly update the corresponding GIS utility network. Recently, Naperville's stormwater network has been extended to include the mains, manholes, and inlets of a newly constructed neighborhood.
You'll use editing tools in ArcGIS Pro and feature templates from ArcGIS Utility Network to edit the network to reflect these additions. This process is known as capturing the as-builts from construction and often involves creating edits based on work sketches, material lists, and field notes captured by the crews that constructed the infrastructure. In this tutorial, you'll base your edits on GPS points that reflect the new constructions.
Create a sediment trap
First, you'll add a gravity pipe, which distributes water through the system, with a sediment trap, which catches sediment carried by stormwater.
- On the ribbon, click the Map tab. In the Navigate group, click Bookmarks and choose Main Extension.
This bookmark shows the location of a neighborhood that was recently built on the edge of the service territory and incorporated into the city's stormwater network.
You need to update your GIS utility network to include the new stormwater infrastructure that was built. The field crew gathered the details of what was constructed and provided them as a collection of GPS points. You'll use these GPS points as reference when editing.
- In the Contents pane, check the box next to the GPS Points layer to turn it on.
At the current zoom extent, one new point appears on the map, on Case Street. There are other points, but for now, you'll focus on this one.
Based on the symbology listed in the Contents pane, there are two types of GPS points: catch basins (another name for sediment traps) and manholes.
The point you can see on the map has the catch basin symbol, meaning the field crews built a catch basin at that location. You'll create a feature within the stormwater network to reflect this construction.
- On the ribbon, click the Edit tab. In the Features group, click Create.
The Create Features pane appears. This pane lists all the editing templates associated with your utility network. You can use them to more quickly create any type of feature you need.
- Scroll down to Stormwater Line: Pipe. Click the Gravity Pipe with Sediment Trap template.
Tip:
Alternatively, you can search for templates using the search box at the top of the pane.
The template contains two types of features you can create, one for gravity pipes and one for sediment traps. By default, the gravity pipe template is selected.
You can adjust the material and diameter of the main before you add it. In this case, the default values match what was installed, so you won't make any changes.
This is a gravity pipe, which uses gravity to distribute water. When editing stormwater features, you should always start your drawing at the upstream feature and draw toward the downstream feature. Doing so will ensure trace tools, like those you used to investigate the illicit discharge, will work properly. In this case, you'll first click the map at the location of the new sediment trap, as represented by the GPS point.
- On the map, click the GPS point on Case Street.
The sketch is started. Next, you'll click the existing manhole that the new sediment trap connects to.
- Click Swr-Strm-Vlt-237, directly east of the new sediment trap.
Note:
Before you click the manhole, ensure Manhole Channel: Point appears over your pointer. If the hover text Stormwater Line - Flow Arrow: Endpoint appears instead, you're not clicking the right place.
- At the bottom of the map, click the Finish button.
Tip:
If you made a mistake (for instance, if you clicked the wrong location), you can instead discard your sketch by clicking the Cancel button next to the Finish button.
The sketch is finished and the feature you created is selected. It contains a sediment trap and a gravity main that connects it to the downstream manhole. Flow arrows in the middle of the new main show the direction water will flow, confirming you drew the feature correctly.
Tip:
If the flow arrow points in the wrong direction, or if you made another mistake, you may want to delete the feature and try again. To do so, on the ribbon, in the Features group, click Delete.
The blue box surrounding the new feature indicates a dirty area, or an area that has not yet been validated. Dirty areas are used to track unvalidated edits and contain pop-up information about the edited feature.
- On the ribbon, click the Map tab. In the Navigate group, click the Explore button.
On the map, the pointer changes. You're able to click features to view their pop-ups.
- On the map, click the blue box that represents a dirty area.
The feature's pop-up appears. At the bottom of the pop-up, the Status Description field shows that the dirty area represents an inserted or updated feature.
To clean up the dirty area in the utility network, you'll need to validate for edits. You'll do that later in the tutorial, so for now you'll hide the dirty areas on the map to reduce visual clutter and make it easier to perform subsequent edits.
- Close the pop-up. In the Contents pane, under Stormwater Utility Network, uncheck the Dirty Areas layer.
The dirty area feature is hidden on the map, although it is still tracking your edits.
Create additional features
You'll continue to add features based on the GPS points.
- On the map, zoom out and pan the map until you can see the GPS points to the west of the sediment trap you added.
There are several more GPS points for you to sketch. Most of them are catch basin (sediment trap) features, but a few are manhole features, including the feature directly west of the feature you created. You'll add this manhole feature using a different feature template.
- In the Create Features pane, under Stormwater Line: Pipe, click Gravity Pipe with Manhole Channel and Vault.
As before, you won't change the default attributes for the feature.
You'll place the next feature at the GPS point at the intersection of Sherman Avenue and Case Street. This feature will allow your utility network to combine the runoff from these two streets with the rest of the system.
- On the map, click the manhole GPS point at the intersection of Sherman Avenue and Case Street.
- Click the sediment trap feature you added. At the bottom of the map, click the Finish button.
You've added the new gravity pipe with manhole channel and vault. Next, you'll add the series of gravity pipe with sediment trap features that extend north along Sherman Avenue.
- In the Create Features pane, click the Gravity Pipe with Sediment Trap template.
- On the map, create a feature that starts at the sediment trap north of the manhole and ends at the manhole. Click Finish.
- On the map, create three more sediment trap features based on the GPS points, each with a flow direction that goes south.
Note:
Make sure to click Finish after creating each feature.
Next, you'll extend the network down Case Street.
- On the map, create a gravity pipe with sediment trap feature that connects the sediment trap GPS point west of the manhole to the manhole GPS point.
The next GPS point is a manhole, so you'll switch to the other feature template.
- In the Create Features pane, click the Gravity Pipe with Manhole Channel and Vault template. On the map, create a feature that flows from the manhole at the intersection of Case Street and Columbia Street to the sediment trap feature you created.
- Switch back to the Gravity Pipe with Sediment Trap template. On the map, create a feature that flows from the farthest west sediment trap to the manhole at the intersection of Case Street and Columbia Street.
- Create a series of four features that connect the first four sediment traps on Columbia Street to the features directly south of them.
There is one more manhole feature, so you'll need to change the template again.
- Switch to the Gravity Pipe with Manhole Channel and Vault template. Create a feature that flows from the last manhole GPS point to the last sediment trap feature you created.
Tip:
If necessary, you can zoom in to help you create the features.
- Switch to the Gravity Pipe with Sediment Trap template. Create a series of three features that connect the last three sediment traps on Columbia Street to the features directly south of them.
The last GPS point to connect is the one on Burlington Avenue, directly east of the manhole on the intersection of Columbia Street and Burlington Avenue.
- Zoom in to Burlington Avenue. Create a feature that flows from the sediment trap on Burlington Avenue to the manhole directly west of it.
You've finished creating all the new features based on the GPS points.
- Close the Create Features pane. Under the map, click the Deselect all currently selected features button.
- In the Contents pane, turn off the GPS Points layer and turn on the Dirty Areas layer. On the map, zoom out until you can see all the new features you added.
You created three new manhole features, which appear at street intersections. The pipes flow in a consistent direction and the new features are tracked by the dirty areas.
Before you validate the edits, you must save them.
- On the ribbon, in the Manage Edits group, click Save.
- In the Save Edits window, click Yes.
Your edits are saved.
- Save the project.
You've edited the network, creating features to reflect new construction. You created pipes with both sediment traps and manholes. Next, you'll perform quality assurance on your edits.
Perform quality assurance
After you edit the utility network to extend your stormwater collection system, how do you confirm that you properly entered the information? Quality assurance is vital for confirming your edits produced an accurate and complete network that meets the requirements of the city. You'll perform quality assurance by validating the topology of your edits, then update the subnetworks to reflect new pipe length statistics.
Validate topology
First, you'll validate the topology of your edits. Your utility network uses network topology to manage and maintain the connectivity between features. Validation checks whether your edits reflect the rules and restrictions that define the network topology.
- In the Contents pane, right-click Dirty Areas and choose Zoom To Layer.
Rather than validating the entire network, you'll only validate the edits you made. You can run validation based on map extent, so zooming to the correct extent before validating is essential. You'll also open the Find Subnetworks pane to ensure the correct catchment is visible.
- On the ribbon, click the Utility Network tab. In the Subnetwork group, click Find.
At this zoom extent, only Catchment I is displayed in the pane. This is the catchment you edited, so the zoom extent is correct. You're ready to validate.
- On the ribbon, in the Network Topology group, click the Validate button.
A message appears, indicating that validation was successful and no errors were found. On the map, all the dirty areas have disappeared, indicating they were validated.
Note:
If you instead received a message that errors were found, any dirty areas with errors will remain on the map and turn red. The most likely error you'll encounter is that there is invalid connectivity. If you do receive an error, you may need to delete the feature you created and create it again with the correct feature template or flow direction.
- In the Find Subnetworks pane, click the Refresh button.
A warning icon appears in the Status column for Catchment I. When you validated your edits, the utility network determined that the contents of Catchment I had been changed.
You'll need to update the subnetwork to finish your quality assurance.
Update a subnetwork
The last step after making edits to the utility network is to update the subnetwork that was changed. At the beginning of this tutorial, you found subnetworks and traced them to better understand the contents of your network. You also looked at pop-ups related to the network to view statistics about the number of catch basins and manholes it had. Updating the subnetwork will ensure these statistics are accurate.
- On the map, click any of your newly constructed gravity pipe features.
In the feature's pop-up, the subnetwork is listed as Unknown.
The feature does not currently belong to a subnetwork. This field will be populated when you update the subnetwork.
- Close the pop-up. In the Find Subnetworks pane, right-click Catchment I and choose Pop-up.
The same pop-up you looked at earlier in the tutorial appears. It displays the same number of catch basins and manholes as before, even though you added several new ones. The new features are not included in the subnetwork's statistics yet.
- Close the pop-up. In the Find Subnetworks pane, right-click Catchment I and choose Trace Subnetwork.
On the map, all the new features you created are selected.
The features being selected during a trace means they were properly connected to the rest of the catchment. When you update the subnetwork, you can expect these features to be reflected in the subnetwork's statistics.
- In the Find Subnetworks pane, right-click Catchment I and choose Update Subnetwork.
Note:
If the Update Subnetwork option is unavailable, you may not have saved your edits. On the ribbon, click the Edit tab and click Save.
The subnetwork is updated. The error icon in the Status column disappears, indicating the subnetwork is now clean. You'll check the pop-ups to confirm that the values you looked at were updated.
- Right-click Catchment I and choose Pop-up.
The values for Catch Basin Count, Manhole Count, and Pipe Subnetwork Length have been updated.
- Close the pop-up. On the map, click any pipe feature you created.
The pop-up now lists Catchment I for Subnetwork Name.
- Close the pop-up and the Find Subnetworks pane. Under the map, click the Deselect all currently selected features button.
- Save the project.
In this tutorial, you learned how the stormwater utility network can be used to analyze your data to assist with tracking illicit discharges. You also learned how to perform edits to expand the network based on new construction in the field. You performed quality assurance on your edits, validating network topology and updating subnetworks.
If you're interested in learning more about utility networks in ArcGIS, try the following resources:
- To learn how to turn your data into a utility network for analysis, try the tutorial Load data into a utility network.
- To learn more about editing a utility network and fixing errors, try the series Editing and Connectivity with ArcGIS Utility Network.
- To learn more about network analysis and how to use subnetworks, try the series Analysis and Tracing with ArcGIS Utility Network.
- To learn more about sewer and stormwater utility networks, try the series Learn ArcGIS Utility Network for Sewer and Stormwater.
You can find more tutorials in the tutorial gallery.