In November 2018, the California State Water Resources Control Board amended the Industrial General Permit for Stormwater Discharges, integrating 36 Total Daily Maximum Loads (TMDLs). Since July 2020, this has led to numerous industrial sites in California undergoing the Exceedance Response Action (ERA) process, facing stricter TMDL Numeric Action Levels (TNALs) and Numeric Effluent Limits (NELs). Consequently, these sites are contemplating significant investments in advanced stormwater treatment to meet these new standards and return to baseline status, thereby avoiding mandatory penalties for NEL exceedances. This study by GSI Environmental (GSI) showcases how scientific methods are employed to identify and analyze stormwater pollutants, aiding facilities in developing strategies to achieve compliance and revert from ERA Level 1 or 2 to Baseline status. Additionally, a key aspect of the study involves experimental bench-scale testing. The study highlights the importance of understanding stormwater pollutant characteristics and exploring comprehensive compliance strategies. This involves installing both passive and active treatment systems, adopting adaptive management techniques, and applying scientific approaches to optimize stormwater treatment performance.