Autumn is here and California’s rainy season, which typically lasts from November to April, is right around the corner, but this year’s stormwater season may not see many storms. The latest data from the National Oceanic and Atmospheric Administration (NOAA) suggests California could be heading into a La Nina winter for the second year in a row. Despite the lack of rain clouds brewing in the near future, now is a good time to start dusting off your stormwater pollution prevention plans. 

The El Nino Southern Oscillation (ENSO) phenomenon is an important factor in global climate patterns and rainfall. Scientists categorize ENSO as a single ocean-atmospheric phenomenon with three phases: El Nino, La Nina, and neutral. During a La Nina, sea surface temperatures (SST) in the equatorial Pacific drop below normal thresholds and trigger a global cooling effect that often influences local rainfall patterns. The opposite, a rise in ocean temperatures, occurs during an El Nino. In the US, La Nina events tend to push storms further north into Washington and Oregon, leaving much of California with below-average rainfall. 

This year’s back-to-back La Nina conditions is fairly common; out of the last 12 first-year La Nina events with 8 of them followed by a second La Nina. According to NOAA, this pattern can be attributed to the complex interactions between SST anomalies and the winds they generate. ENSO events are reinforcing interactions, where changes in Pacific Ocean temperatures cause changes in trade winds that then reinforce the ocean temperature changes and so on. But the processes that govern El Nino and La Nina events are not equal and opposite. El Nino events are characterized by a strong ocean-atmosphere relationship that eventually results in the event’s demise and sets the stage for subsequent La Nina conditions. By contrast, La Nina events are weaker and prime the ocean to return to a neutral state. As a result, the right weather conditions can easily form another La Nina event--creating back-to-back La Nina winters. 

This seems to be the case for 2021. NOAA currently predicts a 70-80% chance of weak La Nina conditions heading into the winter. Although the agency has only issued a La Nina watch, meaning that no official determination has been made, predictions are fairly accurate this late into the year. That doesn’t bode well for California, which is experiencing moderate to severe drought conditions across the state. Another dry and warm winter could extend the state’s fire season and exacerbate ongoing water supply challenges. 

But another year of La Nina doesn’t mean there won’t be any storm clouds this winter. When the rain finally does arrive, it is important to have up-to-date stormwater pollution prevention plans and permits in hand. 

There have been a few updates to stormwater permits over the last year. Changes that were adopted back in 2018 for Industrial General Permits (IGPs) went into effect last summer. Under the new amendments, permit holders are required to follow the USEPA-approved Use of Sufficiently Sensitive Test Methods and comply with any Total Maximum Daily Loads (TMDL) specific discharge requirements set by regional Basin Plans. The State Water Board (SWB) also included a stormwater compliance option to incentivize on-site regional stormwater capture and use. 

IGPs are not the only permits getting a rework. This summer, the SWB completed another step towards finalizing their long-awaited new Construction General Permit (CGP.) Similar to the current permit, the new GCP will regulate the discharge of pollutants from construction sites disturbing one acre or more of soil. But experts who reviewed the preliminary staff draft (released last year) noted that it outlined some significant changes for the regulated community. Important proposed amendments include:   

• Implementing numeric effluent limitations and numeric action levels for sixty-eight TMDLs, as well as addressing other sediment, metal, and bacteria discharges

• Requiring CGP holders to adhere to Statewide Trash Policy Requirements

• Creating a new set of regulations for the use of passive treatment technologies

• Mandating permit holders with Ocean Plan exceptions who discharge into Areas of Biological Significance comply with additional requirements

The SWB completed their public engagement process over the summer. The final deadline for public comments ended in mid-August. Although the new permit won’t go into effect any time soon, the SWB hopes to adopt it this year. 

La Nina year or not, if you haven’t looked at your stormwater pollution prevention plan (SWPPP) recently or are unsure of the monitoring parameters required under your Standard Industrial Code (SIC) with the new IGP, now is a good time to review your monitoring responsibilities. Monitoring locations are identified in the SWPPP and tests are typically specific to your industry and dictated by your SIC code. It is always advisable to review your SWPPP so that you can make certain your organization stays in compliance with your region’s stormwater program. 

To ensure preparedness, Babcock encourages you to order stormwater sampling kits in advance! To order kits or confirm the types of stormwater testing required of your organization, contact your project manager today.