Many industrial and municipal facilities are subject to both stormwater discharge permits and process water quality discharge permits. While both fall under the NPDES program and share the goal of protecting water resources, they differ significantly in permit structure, monitoring approach, sampling triggers, parameters, and reporting requirements. Understanding these differences — and managing both programs effectively — is critical for maintaining compliance. Ecesis provides both water quality software and stormwater compliance software in a single integrated platform.
Side-by-Side Comparison
| Characteristic | Stormwater Monitoring | Water Quality Monitoring |
|---|---|---|
| Permit type | General permit (MSGP, CGP, state GP) | Individual NPDES permit |
| Discharge source | Rainfall runoff from site surfaces | Process wastewater, cooling water, treated effluent |
| Sampling trigger | Qualifying rain event (≥0.1″ after 72-hour dry period) | Fixed schedule (daily, weekly, monthly, quarterly) |
| Limit type | Benchmark values (trigger corrective action) | Effluent limits (legally enforceable) |
| Typical parameters | TSS, pH, oil & grease, COD, sector-specific | BOD, TSS, ammonia, phosphorus, metals, bacteria, pH |
| Reporting | Annual report, benchmark exceedance reports | Monthly or quarterly DMRs |
| Inspections | Routine site inspections, BMP checks | Outfall inspections, sampling events |
| Corrective actions | BMP improvements when benchmarks exceeded | Immediate response, potential NOV |
Stormwater Monitoring Explained
Permit Coverage
Industrial stormwater is typically covered under general permits such as the EPA Multi-Sector General Permit (MSGP) or state equivalents. These permits group facilities by industrial sector and define sector-specific monitoring requirements and benchmark values.
Event-Based Sampling
Unlike process water monitoring with fixed schedules, stormwater sampling is triggered by qualifying storm events. Samples must be collected within the first 30 minutes of discharge from a qualifying rain event, which requires readiness and often grab samples during business hours. Missed qualifying events mean missed compliance obligations.
Benchmark Values vs. Effluent Limits
Stormwater benchmark values are not enforceable discharge limits. However, exceeding benchmarks triggers additional monitoring requirements and corrective action responses. Facilities must document BMP (Best Management Practice) improvements when benchmarks are exceeded across multiple monitoring periods.
Process Water Quality Monitoring Explained
Individual Permit Requirements
Process water quality monitoring operates under facility-specific individual NPDES permits that define exact effluent limits, monitoring frequencies, and reporting deadlines for each outfall. Exceeding an effluent limit constitutes a permit violation that may result in enforcement action.
Scheduled Sampling & DMR Reporting
Sampling follows fixed schedules defined by the permit. Results are compiled into Discharge Monitoring Reports (DMRs) with calculated statistics (monthly averages, daily maximums, loading rates) and submitted electronically on a regular schedule, typically monthly or quarterly.
Where the Programs Overlap
How Ecesis Manages Both Programs
Ecesis provides integrated stormwater and water quality management in one platform:
- Stormwater module — Inspection scheduling, BMP tracking, benchmark monitoring, storm event documentation, annual reporting
- Water quality module — Lab data import, permit limit tracking, data validation, trend analysis, electronic DMR generation
- Shared infrastructure — Same monitoring locations, same users, same corrective action tracking, same compliance dashboard
Related Ecesis Solutions
Water Quality Software
Lab imports, data validation, permit tracking and DMR reporting.
Stormwater Compliance
Stormwater permits, inspections and BMP tracking.
Inspections & Audits
Mobile field inspections with corrective action tracking.
Compliance Obligations
Track all regulatory obligations and recurring deadlines.
Environmental Data
Sensor integration, statistical analysis and trend visualization.
SPCC Software
Spill prevention and oil discharge compliance.
Need to Manage Both Stormwater and Water Quality?
Call (720) 547-5102 or click below to see both modules in a single platform.
