Submitting NPDES Discharge Monitoring Reports is one of the most deadline-sensitive tasks in environmental compliance consulting. DMRs are typically due by the 15th of the month following the monitoring period—miss that date and your client has a reporting violation before anyone even looks at the data. If you are an environmental consultant submitting NPDES discharge monitoring reports on behalf of clients through NetDMR, the process involves more than just data entry. The gap between receiving lab results and clicking “submit” is where most problems occur.

This guide covers the full consultant workflow: from lab data preparation through NetDMR submission, with the common DMR rejection errors that waste hours of rework.

How NPDES DMR Submission Works: The Consultant Workflow

The DMR submission process has two distinct phases that consultants tend to conflate: data preparation (your responsibility) and electronic submission (NetDMR’s process). Understanding where each phase can fail saves significant time.

Phase 1: Data Preparation (Before You Touch NetDMR)

This is where consultants spend 80% of their DMR time and where most errors originate:

Receive and verify lab results. Your lab delivers an EDD or PDF report with analytical results for the monitoring period. Check that all permit-required parameters are present, holding times were met, and data qualifiers (J, U, R flags) are documented. A missing parameter means the DMR cannot be completed—and requesting a reanalysis from the lab may push you past the deadline.
Match results to permit requirements. Each NPDES permit specifies which parameters must be reported, at which outfalls, with what frequency (daily, weekly, monthly), and using what statistical basis (daily maximum, monthly average, instantaneous maximum). Pull the permit’s monitoring table and verify every required parameter has corresponding lab data.
Calculate DMR values. Lab results are individual measurements. DMR fields require calculated values:
- Monthly average: Arithmetic mean of all sample results for the parameter during the monitoring period. For parameters reported in concentration units (mg/L), average the concentrations. For mass-based limits (lbs/day), calculate: concentration (mg/L) × flow (MGD) × 8.34.
- Daily maximum: The highest single-day result during the period.
- Minimum: The lowest result (common for pH and dissolved oxygen).
- 7-day average / 30-day average: Rolling averages as specified in the permit.
Handle non-detects. When a parameter is reported as non-detect (U-flagged, below the reporting limit), DMR reporting conventions vary by state and EPA guidance. Common approaches: report as zero, report as the detection limit, or report as half the detection limit. Check your permit’s special conditions—some permits specify the convention explicitly. Using the wrong convention is a common rejection cause.
Verify units match the permit. Lab results might report in ug/L (micrograms per liter) while the permit limit is in mg/L (milligrams per liter). A unit mismatch that goes unnoticed can make a compliant result look like an exceedance or vice versa. Convert before entering: 1 mg/L = 1,000 ug/L.

Phase 2: NetDMR Entry and Submission

Log in through CDX. EPA’s Central Data Exchange (CDX) is the authentication gateway for NetDMR. If you submit DMRs for multiple clients, you need access to each permit in NetDMR. Access requests require a signed subscriber agreement—your client must authorize you as a data provider for their permit.
Locate the DMR form. In NetDMR, navigate to “All DMRs & CORs” and search by permit number and monitoring period. The system pre-populates the form based on the permit’s monitoring requirements—you see the required parameters, limits, and reporting frequencies already structured.
Enter calculated values. For each parameter row, enter your calculated DMR values (monthly average, daily maximum, etc.) in the appropriate fields. NetDMR validates entries against permit limits in real time—if a value exceeds a limit, it flags the exceedance. You must still submit the DMR with the exceedance, but the system records it.
Enter No Discharge (NODI) codes if applicable. If no discharge occurred during the monitoring period, use the appropriate NODI code instead of entering zeros. Common codes: C (no discharge), B (below detection), and 9 (conditional monitoring not triggered). Entering zero when you should enter a NODI code is a data quality issue that regulators flag.
Review and sign. NetDMR requires an authorized signatory to electronically sign the DMR before submission. For consultants submitting on behalf of clients, the client’s authorized representative must sign—or must have formally delegated signature authority to the consultant. The sign-and-submit button appears at the top and bottom of the DMR form.
Confirm submission. After signing and submitting, you receive a confirmation number and email. Save both. If the submission fails (system error, validation failure), you will not receive a confirmation—check the DMR status in NetDMR to verify it moved to “Submitted” status.

Common DMR Rejection Errors and How to Avoid Them

These are the rejection and rework triggers that consultants encounter most frequently:

Error 1: Parameter Code Mismatch

NetDMR uses specific EPA parameter codes (five-digit numeric codes) for each analyte. If your lab reports “Total Suspended Solids” but you enter the value under the wrong parameter code (e.g., using the code for “Suspended Solids, Total Filterable” instead of “Solids, Total Suspended”), the DMR entry lands in the wrong field. This is especially common for nitrogen species (ammonia nitrogen vs. total nitrogen vs. TKN) and metals (total vs. dissolved).

Error 2: Statistical Basis Mismatch

Entering a monthly average value in the daily maximum field (or vice versa) is more common than anyone admits. Double-check which statistical basis each column requires. The permit monitoring table is your reference—not the NetDMR form layout, which can vary.

Error 3: Non-Detect Reporting Inconsistency

Different permits handle non-detects differently. Some require reporting the detection limit value with a “<” qualifier. Some require zero. Some require half the detection limit. Applying one permit’s convention to another permit’s DMR will trigger reviewer questions. Document your convention in each project file.

Error 4: Missing Monitoring Periods

If your client’s permit requires monthly monitoring but no samples were collected in a given month (perhaps due to a facility shutdown), you still must submit a DMR with appropriate NODI codes. A missing DMR is a violation—even if there was no discharge to report.

Error 5: Signature Authority Gaps

NetDMR requires that the person who signs the DMR have legal authority under 40 CFR 122.22. For corporate permittees, this means a “responsible corporate officer” or a person with delegated authority. Consultants cannot sign DMRs on behalf of clients unless the client has filed a formal delegation letter with the permitting authority. If your client’s authorized signatory leaves the company, DMR submission stalls until a new signatory is designated.

Managing DMRs Across Multiple Permits

Consultants managing 10–20+ client permits need a system beyond memory and calendar reminders:

Build a permit deadline matrix: List every active permit, its monitoring frequency, DMR due dates, and the lab turnaround time needed to meet each deadline. Work backward from the due date: if DMRs are due the 15th, your lab needs results by the 8th (one week for data preparation), which means samples must ship by the 1st (assuming a 7-day TAT).
Standardize your data preparation template: Use a consistent worksheet structure for every permit’s DMR calculations. This reduces errors when different staff handle different permits and makes QA review faster.
Track submissions and confirmations: Maintain a log of every DMR submission: permit number, monitoring period, submission date, confirmation number, and any noted exceedances. This is your audit trail when a regulator questions a submission.

Environmental data management tools that support NPDES workflows can automate much of the data preparation phase—importing lab EDDs, matching results to permit parameters, calculating statistical bases, and flagging exceedances before you open NetDMR. If your firm is evaluating tools that handle this workflow, our overview of environmental data management software options covers the landscape from lightweight SaaS to enterprise EDMS.

Key Deadlines and Compliance Context

DMR deadlines are not suggestions. Under the Clean Water Act and the NPDES Electronic Reporting Rule, late or missing DMR submissions are independently citable violations—separate from any effluent limit exceedances the data might contain. Your client can be in full compliance with all discharge limits and still receive a notice of violation for a late DMR.

Most permits require DMR submission by the 15th or 28th of the month following the monitoring period. Some permits have quarterly or semi-annual reporting. Know your specific permit schedule—do not assume all permits follow the same calendar.

For technical support with NetDMR, contact EPA’s helpdesk at 877-227-8965 or your state’s NetDMR lead. For questions about your specific permit requirements, contact your permitting authority directly—they are the definitive source for how your permit’s monitoring conditions should be interpreted.

How to Submit NPDES Discharge Monitoring Reports: NetDMR Workflow and Common Rejection Errors