Hexavalent Chromium MCL (SWRCB-DDW-21-003)

Hexavalent Chromium MCL Information

Status of Proposal

This rulemaking is in progress.

  • This rulemaking began on June 16, 2023
  • A hearing was held on August 2, 2023
  • Written comments were due August 18, 2023 (for the 45-day comment period)
  • Written comments were due December 15, 2023 (for the 15-day comment period)
  • Written comments due March 4, 2024 (for the 2nd 15-day comment period)

Proposed MCL: 10 ppb (0.010 mg/L)

Proposed DLR: 0.1 ppb (0.0001 mg/L)

This MCL includes a compliance schedule based on water system size and requirements to submit compliance plans and operations plans under certain conditions. See the rulemaking documentation below for details.

Inquiries regarding the contents of this regulation may be directed to Bethany Robinson (Bethany.Robinson@waterboards.ca.gov) and Melissa Hall (Melissa.Hall@waterboards.ca.gov).

Rulemaking Documentation

Revised Second 15-day Comment Period Documents

  • Notice of Public Availability of Additional Documents Relied Upon

Second 15-Day Comment Period Documents

15-Day Comment Period Documents

CEQA Documentation

Peer Review Documents

Complete Rulemaking File (in Progress)

Item Date

Notice of Proposed Rulemaking:

Notice of Proposed Rulemaking, Public Hearing, and 45-day Notice Period to Consider Proposed Hexavalent Chromium MCL Regulation


Initial Statement of Reasons (ISOR) - ISOR Errata


Text of Originally Proposed Regulations


Notice of Public Availability of Changes to Proposed Regulation:

Notice of Public Availability of Changes to Proposed Regulations (15-day comment period)


Revised Text of Proposed Regulations


Addendum to Initial Statement of Reasons (ISOR)


Office of Administrative Law (OAL) Notices:

Notice Register Index, OAL Notice No. Z2017-1003-07


California Regulatory Notice Register 2017, Volume No. 41-Z, pp. 1550-1556


List of Materials and Documents Relied Upon:

An Excel List of Materials and Documents Relied Upon is available. However, not all documents are available online. To request a document, email Bethany.Robinson@waterboards.ca.gov.


Summary of Rulemaking Proceedings

  • Sections Affected: California Code of Regulations, Title 22, sections 64415, 64431, 64432, 64447.2, 64463.4, 64465, and 64481
  • Standardized Regulatory Impact Assessment (SRIA) Submitted to Department of Finance: 13 December 2022
    • SRIA (an updated version of this document is included in the formal rulemaking as ISOR Attachment #2)
    • DF-131
  • Notice of Proposed Rulemaking Published: 16 June 2023
  • Close of 45-Day Public Comment Period: 04 August 2023
  • Date of Public Hearing: 02 August 2023
  • Notice of Public Availability of Changes to Proposed Rulemaking Published: 22 November 2023
  • Close of 15-Day Public Comment Period: 15 December 2023
  • Board Adoption Hearing: TBD
  • Date Filed with Office of Administrative Law: TBD
  • Approved by Office of Administrative Law: TBD
  • Filed with the Secretary of State: TBD
  • Effective Date: TBD