Permit Limit Sets and Limits

Limits specify permit wastewater discharge monitoring requirements and effluent limits. Before limits can be added to a permit, a feature must be added to the permit. Limit sets and limits are then added to the permitted features. Limit sets and limits drive the generation of Discharge Monitoring Reports (DMRs) that a permittee is required to submit as a condition of their permit.

Limit sets and limits can only be modified while a permit is in In Process status. When a permit status is updated to Issued/In Effect, the expected DMRs are generated based on the limit sets and limits that have been entered. Limits are no longer changeable at that point.

If you do not see the Limits tab on the permit, this is configured in the Permit Categories lookup, under Permit Feature Display Mode.

Limit Sets


Limit sets define the period of time covered by Discharge Monitoring Reports (DMR) and the date on which DMRs begin for a permit. A limit set can relate to multiple permitted features, which can be helpful when defining limits for permits that contain a large number of outfalls. Limit sets contain one or more monitoring requirements or effluent limits. For example, a limit set may indicate that a permittee must submit a monthly report containing sampling data for outfall number 001.

Limit sets are typically used to group sampling requirements based on monitoring frequency at an outfall (e.g., monthly, bi-monthly, quarterly, annually, etc.), but also can be used to group limits that must be reported under different operating conditions. For example, a facility may have two different sets of effluent limits at an outfall based on data that may vary from month to month, such as factory production output or receiving stream flow. In a case like this, typically called tiered limits, a limit set can be set up to represent each condition. The permittee would fill out the DMR for the limit set that applied for that period and would report No Discharge for the limit set that did not apply.

Adding and Editing Limit Sets

Limit Sets and Limits can only be added, modified, or deleted if the permit is in ‘In Process’ status and the current user has rights to edit the permit. Limit sets may also be deleted if the set is associated with a prior permit version.

On the Limits tab of the Permit Details screen, one of the following actions may be taken:

Fixing Initial Monitoring Dates

A Fix Initial Monitoring Dates button appears if one or more limit sets meet the following conditions:

  1. Limit set is missing an Initial Monitoring Date.

  2. Limit set Initial Monitoring Date would create DMRs for monitoring periods before the current permit version’s effective date.

  3. Limit set’s reporting period is non-monthly (e.g., quarterly, semi-annual, or annual) and does not begin in the expected calendar month. This check is only performed if nVIRO is configured to enable this check.

Click this button to automatically calculate a valid limit set initial monitoring dates. Since situations can vary, make sure to verify that the calculated dates are correct for the given permit.


When adding or editing a limit set, the following fields are displayed:



Limit Set Name

A short text description of the limit set. This is displayed on the top of a DMR form to help identify the limit set.

Limit Set Description

A long text description of the limit set. Displayed on the internal Limit Set list page for internal staff to better understand the purpose of a limit set.

ICIS Limit Set Designator

A one- or two-character identifier is used to uniquely identify the limit set on the permitted feature. This value is suffixed onto the Permit Feature Identifier for display in lists and on the DMR data entry pages. For example, designator “A” on permitted feature “001” would display as limit set “001A”.

Limit Set Status

Allows for a limit set to transition from Pending to Active and finally, Closed. Limit Sets default to Active status when first created, and the Status Date is synchronized with the Initial Monitoring Date.

If a limit set is initially set to Pending status, DMRs will not be created for this limit set when the permit is issued.

If the Limit Set Status needs to change after a permit is put into effect, the permit will need to be set back to "In Process" status, after which new statuses can be added. Existing statuses cannot be edited once they have been flowed to ICIS-NPDES.

Wastewater Types

A list of one or more wastewater types. This list is filtered to only allow selection of the wastewater types assigned to the permitted feature to which the limit set is assigned.

This drop-down will not display if no wastewater types have been configured in the system.

These values can be configured to be sent to ICIS-NPDES as Permitted Feature Characteristics.

This field has no bearing on the creation of DMRs.

Design Flow or Authorized Flow / Unit

The amount of flow that the wastewater system is designed to process or that is authorized for this limit set.

This field has no bearing on the creation of DMRs.


Text field for describing how the wastewater is conveyed to the receiving stream (e.g., “unnamed ditch”). This field is intended for use in permit document templates to construct a sentence describing how the wastewater reaches a receiving stream.

Generate DMRs

Checkbox that indicates whether to generate DMRs for this limit set. If the facility is allowed to perform retained self-monitoring (RSM), then uncheck this box. If unchecked, the limit set and associated limits will not flow to ICIS-NPDES.


Checkbox that indicates whether the DMR is scheduled or unscheduled. Most limit sets are scheduled, indicating that DMRs should be generated at a regular, predictable frequency.

Unscheduled limit sets are for event-based DMR reporting that occurs unpredictably. An example would be a bypass caused by a rain event. If one or more unscheduled limit sets exist on a permit, users will have the option to submit an unscheduled DMR on the DMR List page. When selected, the user will be prompted to select from a list of available unscheduled limit sets.

Monitoring Period

Indicates the period of time covered on each generated DMR form. 

Reporting Period

Indicates how often DMRs must be submitted. The selected frequency must be less than or equal to the monitoring period and must be equally divisible by the monitoring period.

It is recommended that the reporting period be set to be the same as the monitoring period. Varying reporting periods was a feature that was useful when DMR reporting was performed on paper because it simplified the mailing requirements for the permittee, but with electronic reporting, this option is less useful since all data is collected online.

First DMR Begin Date

The begin date of the first (earliest) DMR in the limit set.

For non-monthly limit sets (quarterly, semi-annual, etc.), this date selects the cadence for all future DMR periods. For example, if the first DMR Begin Date of a limit set with quarterly monitoring frequency is in February, the generated DMRs will be in February, May, August, and November each year. For this reason, it is very important to ensure that the initial monitoring date is set correctly. If the intent is for quarterly DMRs to fall on regular calendar quarters, the First DMR Begin Date must begin in January, April, July, or October. This is true even if the limits in the limit set do not start in one of these months.

Days from Report End Date When Due

Indicates the grace period between the end of a DMR monitoring period and when the DMR is due. For example, if the DMR is due 15 days after the end of each monitoring period, then the value 15 should be entered. Note that DMRs will show as late when the due date comes to pass.

NOTE: nVIRO can be set up to not calculate late DMR violations until some period after the due date. For agencies that still receive paper, this can provide a buffer for the agency to finish data entry before late violations are generated.

Applicable Months

Indicates the months that limits within the limit set apply. The selected months serve as the default selected months when adding new limits to the limit set. This is provided as a time-saving convenience feature. Limit months can always be manually changed on each limit.

Special Instructions

Instructions displayed on the DMR Data Entry form. This should be used to describe any limits where a “See Comments” monitoring location has been added or any other time when instructions should be provided to the external user about how to fill out the DMR.



Limits include monitoring requirements and effluent limits. Limits are added to a Limit Set and define the parameters that display on DMR forms. Each limit consists of a parameter (substance or condition to be measured), a monitoring location (indicating where the sample should be taken, or other special condition), and one or more limit values.

The standard EPA DMR Summary form defines up to five different limits for a given parameter, grouped by quantity and concentration. The five-column format provides a compact way of presenting a data entry interface for either paper or page. A parameter needs only one limit to be entered in one of the five available columns in order to be saved.

Adding and Editing Limits

On the Limits tab, one of the following actions may be taken:

  • Click the Add Limit button to add a new limit.

  • Click the Open button for an existing limit to edit the limit.

  • Click the Copy button for an existing limit to copy it as a new limit.

Add/Edit Limit Screen Controls



Limit Set

The limit set to which the limit relates.


The substance or condition to be measured.

Monitoring Location (Stage)

The monitoring location where the sample should be taken (e.g., final effluent, influent, upstream, downstream). The monitoring location can also be used to segment different conditions when different limits apply to the same parameter. For example, any of the “See Comments” options can be used in this scenario.

Zero values allowed on DMR entry

Read-only label indicating whether zero values are allowed to be entered in a DMR for the selected parameter. This value can be changed by an administrator on the nVIRO parameter lookup maintenance page.

Modification Number

Read-only field is only used for migrated data where limit modifications were performed. nVIRO does not support limit modifications. A new permit version must be created if monitoring requirements or limits need to change.

Start Date

The date on which sampling for the parameters is to begin. Leave the “Use Permit Effective Date” box checked if monitoring is to begin when the permit becomes effective.

End Date

The date on which the parameter sampling will be completed. Leave this field blank if monitoring is to continue for the life of the permit, even if the permit expires or is administratively continued. If the End Date is entered and matches the permit expiration date, it will also continue after the permit expiration as long as the permit version is active.

Applicable Months

The months in which the parameter applies. For example, if a limit for a parameter varies seasonally, then two limits can be entered, one for the summer months and one for the winter months.

Care should be taken to ensure that multiple seasonal limits are not in effect for the same limit set period. This is only of concern for non-monthly limit sets. For example, if a temperature limit for summer is May-August, a winter limit exists for all other months, and a quarterly DMR exists for August-October, then the limit will appear twice on the DMR, each with a different Season Number. The permittee may need a special explanation or instructions on how to report this condition when it occurs.

Quantity/Loading Area

Defines monitoring requirements and effluent limits for mass (e.g., measurements in pounds).


Add/Edit Limit Screen - Limits and Monitoring Requirements Controls

The Limits and Monitoring Requirements area displays the quantity and concentration monitoring requirements and effluent limits. The data entry controls are arranged in a five-column grid consisting of up to two quantities and three concentrations.

The example below shows a typical limit for pH where the DMR reported value must be greater than 6 and less than 9 Standard Units (SU).



Limit Type

Indicates whether the limit is Optional, Required, or Limited:

Optional Monitoring: Allows for optional reporting of measurements if taken. A violation is not created if left blank on a DMR.

Required Monitoring: Requires that a value be reported; however, no minimum or maximum threshold is specified. A violation is created if not reported on a DMR.

Limit: A minimum or maximum threshold is enforced. Data entry is required on the DMR, and a violation is created if the threshold is exceeded.

Limit Value Qualifier
Limit Value

This field is displayed when the Limit Type is “Limit”.

Indicates the minimum or maximum allowed threshold for the calculation of violations.

When the Value Qualifier is left blank, DMR value exceedance calculations are based on the selected Statistical Base code:

  • For statistical base codes of Average or Maximum, a valid (non-violation) DMR value must be less than the limit value.

  • For statistical base codes of Minimum, a valid (non-violation) DMR value must be greater than the limit value.

Value qualifiers, if specified, should match the greater than/less than evaluation criteria of the specified Statistical Base described above. For example, Average/Maximum statistical bases should be used with < or <= whereas Minimum statistical bases should only be used with > or >=. In other words, the qualifier used defines the non-violation state of a reported DMR value.

Statistical Base

For DMR Summary reporting, it indicates what type of aggregation formula to use when reporting minimums, averages, and maximums for the limit over a DMR reporting period.


The basis for the limit. Not required. Selection has no bearing on DMR generation or calculation logic.


Displayed as a button with an ellipsis (…). Allows for the optional entry of comments related to the limit. Comments are not displayed on a DMR.

Quantity Unit

The unit of measure for the quantity/loading limits. The available choices are only the quantity units that apply to the selected parameter.

Quality/Concentration Area

Defines monitoring requirements and effluent limits for concentrations (e.g., measurements in milligrams per liter).

Concentration Unit

The unit of measure for the quality/concentration limits.

Sample Frequency

The frequency at which the samples are to be taken. Displayed on the DMR form.

Sample Type

The type of sample to be taken. Displayed on the DMR form. The available choices are only the concentration units that apply to the selected parameter.

Bulk Update Limit Details

Parameter limits can be updated in bulk on a draft permit. To upload multiple limits at once

  1. Select one or more limits from the list of limit parameters,

  2. Click the Bulk Update button. The bulk update modal will appear.

  3. Select the desired fields to bulk update and update the fields accordingly.

  4. Click the Save button.

The limits are updated to reflect the changes.

The following fields are available to be updated across the selected limits:

  • Monitoring Location

  • Limit Start Date

  • Use Permit Effective Date

  • Limit End Date

  • Sample Frequency

  • Sample Type

  • Months

  • Is Enforceable

Note that limit values cannot be bulk updated.

Limit Summary and Detail View Modes

The base limit list view is a 'Summary' mode listing information such as limit set, parameters, monitoring location/stage, and months (season). To facilitate online review of permit limits, the list may also be viewed in "Detail" mode, which adds additional details such as frequency, statistical base, DMR col (quantity/concentration) value, and units.

To toggle between Summary and Detail modes, click the View As: Summary | Detail button at the top of the limit list.

DMR Creation upon Permit Issuance

DMRs are created when a permit's status changes to "In Effect." This can happen either when a user updates the status of an In Process permit to "Issued/In Effect" and the permit effective date is on or before today, or as part of a nightly process that updates the status of a permit from "Issued (Not in Effect)" to "In Effect" when the permit effective date comes to pass.

When updating the status of an In Process permit to "Issued/In Effect," a series of validation messages will appear, verifying that the Limit Set and Limit data have been entered correctly.

Once a permit with limits is In Effect, a View DMRs button will appear in the Other Actions area of the right sidebar on the Permit Details page. This will navigate the user to the DMR List page, which is the same page that external users will use when filling out DMRs.

The Audit History button on the Permit Details page will list how many DMRs were created at the time of the permit issuance. If the permit version is a modification of an existing permit, existing unsubmitted and draft DMRs on the superseded permit version will be removed and recreated using the updated Limit Set and Limit definitions. If DMRs were replaced, this information is also visible in the permit's Audit History. In some cases, this can leave what appear to be duplicate DMRs for the same reporting period, each with data from the previous and current permit versions. This can occur in two scenarios:

  1. A DMR has already been submitted for a period that has been overwritten with updated limits on the latest permit version, or

  2. The permit has DMRs that cover a period greater than monthly (quarterly, semi-annual, etc.), but the permit was issued in the middle of a reporting period. This means that the old and new limits were applicable during the same period.

DMRs will be created through the permit's expiration date. Once a permit's expiration date comes to pass, it will either become Extended or Expired. As part of a nightly process, the system will create future DMRs for periods beyond the permit expiration date. The period of time into the future for which DMRs will be created is configurable by an administrator but defaults to 6 months. Each night, the system will check to see if new DMRs are needed for future periods and create them as needed.