November 23, 2022

What you need to know about the 2022 Construction General Permit (CGP)

In September 2022, the California State Water Resources Control Board adopted the 2022 Construction General Permit (CGP). The newly adopted permit becomes effective September 1, 2023 and includes several major changes from the existing 2009 CGP. These changes include:

  • Total Maximum Daily Load (TMDL) Implementation Requirements;
  • Construction Dewatering and Discharge Requirements; and
  • Revised Storm-Related Monitoring Requirements

Existing and new projects that are issued an active WDID number prior to September 1, 2023, are provided a 2-year regulatory transition period. During this transition period, permittees will have the option to continue coverage under the existing 2009 CGP requirements, or enroll for coverage under the new 2022 CGP requirements. After August 31, 2025, projects with an active WDID number under the 2009 CGP will need to enroll for coverage under the 2022 CGP.

New projects that apply for CGP coverage on or after September 1, 2023, must do so under the 2022 CGP.

TMDL Implementation

TMDLs are regulatory tools providing the maximum amount of a pollutant from potential sources in the watershed that a water body can receive while attaining water quality standards. The 2022 CGP adds TMDL monitoring and reporting requirements. TMDL implementation requirements apply to projects that 1) discharge to a water body or watershed with an EPA-established TMDL and 2) have on-site sources of the TMDL pollutant, as determined by the pollutant source assessment. Sampling for TMDL pollutants is triggered when the pollutants may be discharged due to failure to implement BMPs, a container spill or leak, or a BMP breach, failure, or malfunction. Additional information regarding TMDL requirements is included in Attachment H of the 2022 CGP.

Construction Dewatering and Discharge

Another major change to the 2022 CGP is monitoring and reporting requirements for construction dewatering and discharge. Unless the dewatering discharge activities are subject to a separate NPDES permit, the 2022 CGP requires sampling within the first hour of discharge, and daily sampling thereafter for continuous dewatering discharges. Similar to the existing CGP, the samples are tested for pH and turbidity and the results compared with the numeric action levels. Additional information regarding dewatering requirements is included in Attachment J of the 2022 CGP.

 Storm-Related Monitoring

The 2022 CGP introduces a newly defined term called the Qualifying Precipitation Event (QPE), which is defined as a forecast of 50 percent or greater probability of precipitation and a quantitative precipitation forecast of 0.5 inches or more within a 24-hour period. The 2022 CGP eliminates the requirement for the preparation of REAPs prior to predicted storm events, but keeps pre-, during-, and post-qualifying precipitation event inspections. Stormwater sampling requirements and the determination of Numeric Action Level (NAL) exceedances were also revised. The 2022 CGP removes daily averaging of sampling results for the determination of NAL exceedances. Instead, each sample result must be compared with the pH and turbidity NALs. NAL exceedances will prompt a mandatory site inspection by the project QSD and project QSP within 14 days of the exceedance.

ENGEO Support

ENGEO is committed to helping you understand and navigate the 2022 CGP. Please contact Victoria Drake,, if you have any questions about the 2022 CGP, or the regulatory transition period. We would be happy to facilitate a lunch-and-learn for your team to discuss the CGP reissuance, or any specific topics of interest.

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