INITIAL STUDY ASSESSMENT GUIDELINES (ISAGs)
COMPREHENSIVE UPDATE
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The Updated CEQA Implementation Manual and Initial Study Assessment Guidelines was Adopted by the Board on September 30, 2025
Project Overview
Background
The California Environmental Quality Act, or CEQA, is the state law that requires public agencies, including the County of Ventura, to study and disclose potential environmental impacts of projects and adopt any feasible measures to reduce or eliminate those impacts before a project is approved.
One of the main goals of CEQA is to inform decision-makers and the public about potential environmental impacts of proposed projects. The County of Ventura carries out environmental review through local CEQA guidelines that are included in two documents: the Ventura County CEQA Implementation Manual (Implementation Manual) and the Ventura County Initial Study Assessment Guidelines (ISAGs).
The Implementation Manual and the ISAGs ensure that the County uses consistent procedures and evaluation criteria when examining the physical impacts of a public or private project on the environment. The ISAGs allow for a streamlined and transparent process for the public, project applicants, consultants, County staff, and decision-makers to review the environmental effects of a project.
The Project
The Implementation Manual was last updated in 2010 and the ISAGs were last updated in 2011. The documents needed a comprehensive update to align these documents with current County policies, CEQA requirements, and other state and federal regulations.
Public participation is a key element of the CEQA process. A public open house was held on May 7, 2025 and a public review period was open from April 24 – May 24, 2025. Revisions to the updates were made in response to public comments received.
See below to learn more about the revisions.
Click here to learn more about the project (PDF).
Project Adoption
On September 30, 2025, the Board of Supervisors approved (1) the proposed updates to the ISAGs, Noise and Vibration Assessment Guidelines, and Implementation Manual, (2) a related General Plan amendment, and (3) Addendum No. 3 to the General Plan Environmental Impact Report (SCH No. 2019011026). To ensure that project environmental reviews that are currently in progress are unaffected, development project applications already deemed complete or will be deemed complete by December 31, 2025 will be subject to the 2011 ISAGs and 2010 Implementation Manual. Development project applications deemed complete on or after January 1, 2026 will be subject to the 2025 ISAGs and 2025 Implementation Manual.
Updated Initial Study Assessment Guidelines
The ISAGs inform the public, project applicants, consultants, and County staff on environmental impact thresholds and ways to determine whether a project has the potential to cause a significant negative effect on the environment. The ISAGs cover a wide range of topic areas, including air quality, transportation, water quality, biological resources, and many others listed below. Click here for an overview of the topic areas. Click here for a summary of the overall updates.
The ISAGs were updated in 2025, which include consolidation of sections of similar topics and removing certain sections, alignment with Appendix G in the State CEQA Guidelines, updated thresholds and methods for analyzing potential project impacts (including the Noise and Vibration Assessment Guidelines), and incorporation of certain General Plan programs and policies.
- 2025 ISAGs (Applies to projects deemed complete on January 1, 2026 or later)
- 2011 ISAGs (Applies to projects deemed complete on December 31, 2025 or earlier)
Updated CEQA Implementation Manual
The Implementation Manual was formerly titled the “Administrative Supplement to the State CEQA Guidelines.” The Implementation Manual includes procedures to comply with CEQA, such as filing public notices of proposed projects. The Implementation Manual was updated in 2025, which includes updated CEQA requirements, procedures to amend the document in the future, and County agency responsibilities.
2025 CEQA Implementation Manual (Applies to projects deemed complete on January1, 2026 or later)
Administrative Supplement to the State CEQA Guidelines (Applies to projects deemed complete on December 31, 2025 or earlier)
Contact Us
Inquiries may be directed to Case Planner, Jessica Nguyen, at (805) 654-5037 or by e-mail to JessicaT.Nguyen@venturacounty.gov