El Niño forecasts are raising expectations for a wetter-than-normal season across California, making now the ideal time for industrial facilities to prepare for the first significant storm event. After months of dry weather, pollutants such as dirt, oils, and industrial residues can accumulate throughout a facility. When rainfall finally arrives, those pollutants can be carried offsite through stormwater runoff, making the first storms of the season some of the most critical from both an environmental and compliance perspective.
For facilities covered under California’s Stormwater Industrial General Permit (IGP), rainy season preparation should begin well before the first storm appears in the forecast. From BMP implementation and sampling readiness to SWPPP updates and employee training, now is the time to confirm that your stormwater program is prepared for the months ahead. A strong El Niño can enhance precipitation in the San Joaquin Valley as early as November, and there is already consensus among the weather models and modelers that there is at least a 75% of a record-breaking El Niño in 2026-2027.
Before the Rain Arrives: Walk Your Facility
Before reviewing your Storm Water Pollution Prevention Plan (SWPPP), monitoring requirements, or sampling procedures, take time to walk the facility. A site walkthrough is one of the most effective ways to identify potential stormwater concerns before the rainy season begins.
Inspect industrial activity areas, material storage locations, drainage pathways, storm drain inlets, outfalls, and any areas where stormwater may come into contact with pollutants. Look for accumulated sediment, exposed materials, leaking equipment, damaged containment systems, and other housekeeping issues that could affect stormwater quality once rainfall begins.
Facility inspections should not be limited to required monthly visual observations or the Annual Comprehensive Facility Compliance Evaluation (Annual Evaluation). Routine site walkthroughs throughout the year can help identify changing site conditions, housekeeping concerns, damaged BMPs, exposed materials, and other potential stormwater issues before they affect water quality or compliance.
At the same time, facilities should verify that required inspections are being completed and documented. Monthly visual observations provide an opportunity to identify potential pollutant sources, evaluate whether BMPs are functioning as intended, and implement corrective actions before they become compliance concerns. This is also a good time to review observation records and ensure any identified issues have been addressed and documented appropriately. Given the predicted strength of the El Niño, also look for conditions where unusually large amounts of rain or higher than normal water levels could make a difference compared to a typical year. In other words, can your BMPs handle excessive rainfall?
The start of the rainy season is also an ideal time to confirm that routine BMPs are being implemented consistently. Sweeping paved surfaces, cleaning industrial areas, maintaining secondary containment, removing debris, and addressing spill-prone areas before rainfall occurs can significantly reduce pollutant loading in stormwater discharges.
Because pollutant buildup is often greatest after extended dry periods, the “first flush” of the season can have a substantial effect on monitoring results. Facilities that proactively address housekeeping deficiencies, maintain BMPs, and document their inspection activities before the first storm are often better positioned when Qualifying Storm Event (QSE) sampling begins.
Is Your Sampling Program Ready?
Many facilities discover issues with their sampling program only after a storm is in the forecast. Unfortunately, by then it can be difficult to obtain replacement supplies, update documentation, or coordinate with laboratories. Before the rainy season begins, facilities should inspect and take inventory of all sampling supplies, including:
- Sample bottles and preservatives
- Coolers and ice packs
- Personal protective equipment
- Field documentation forms
- Chain of custody forms
- pH testing supplies
- Labels and shipping materials
Particular attention should be given to pH paper and other field measurement supplies. Expired pH strips, or strips that were stored at high temperatures, may provide inaccurate results and can create questions regarding data quality and compliance. Facilities should review expiration dates and replace any expired sampling bottles or questionable sampling materials before monitoring season begins. Consider also the physical means of sampling collection. Is this the year that high water will make you wish you had gotten better boots for sample collection?
This is also a good opportunity to coordinate with your laboratory. Confirm that laboratory contacts remain current, sampling parameters are accurate, chain of custody forms have been updated, and any facility-specific monitoring requirements are correctly identified.
A few hours of preparation before the rainy season can prevent significant stress when a QSE suddenly develops.
Review Your SWPPP Before Regulators Do
While field activities are often the focus of stormwater compliance, many compliance issues originate in outdated planning documents. The SWPPP serves as the foundation of a facility’s stormwater program. As operations change over time, the SWPPP can quickly become outdated.
Prior to the rainy season, facilities should review their SWPPP and verify that:
- Facility maps accurately reflect current conditions
- Industrial activities are properly described
- Drainage patterns remain accurate
- Sampling locations are correctly identified
- BMP descriptions reflect current practices
- Potential pollutant sources are properly documented
Facilities should also confirm that the SWPPP team identified in the document remains current. Personnel changes, new management responsibilities, and staffing adjustments often occur throughout the year, and stormwater documents do not always keep pace.
An updated SWPPP not only supports compliance but also provides facility personnel with a clear roadmap when storms occur and important decisions need to be made quickly.
Don’t Forget Training and Documentation
Before the rainy season begins, facilities should verify that required stormwater training has been completed and documented. Personnel involved with visual observations, BMP implementation, sampling, inspections, and reporting responsibilities should understand their roles and know what actions are expected when storm events occur.
For Level 1 and Level 2 facilities, additional requirements may apply. These facilities should confirm that any required Qualified Industrial Storm Water Practitioner (QISP) involvement has been completed and documented in accordance with permit requirements.
Training records should identify:
- Training dates
- Training topics
- Personnel in attendance
- Instructor information
Documentation extends beyond training records. Facilities should also maintain BMP implementation records, spill response and cleanup documentation, visual observation records, monitoring information, laboratory reports, and annual report support documentation.
The IGP requires facilities to retain stormwater monitoring information, records, data, and reports for a minimum of five years. Before the rainy season begins, it is worth taking the time to ensure records are complete, organized, and readily accessible if requested during an inspection.
Join Trinity for a Complimentary Industrial General Permit Refresher
To help facilities prepare for the upcoming rainy season, Trinity Consultants’ Bakersfield office will be hosting a Complimentary Seminar: Navigating Stormwater Compliance in California’s Central Valley | Trinity Consultants.
This practical refresher is designed for facility owners, operators, environmental professionals, and compliance personnel who want to better understand their stormwater obligations and prepare for the challenges of the upcoming wet season.
Topics will include:
- IGP Applicability
- Program Overview
- Compliance Expectations and Common Challenges
- Sampling Best Practices
- Monitoring Requirements and Documentation
Whether you are new to stormwater compliance or simply looking for a refresher before the next rainy season, this session will provide practical information, regulatory insights, and an opportunity to connect with local professionals experienced in California stormwater compliance.
