SR-1 San Gregorio Embankment and Drainage Facilities Repair DO (EA 1V510)
Summary
SCH Number
2026090991
Public Agency
California Department of Transportation, District 4
(DOT)
Document Title
SR-1 San Gregorio Embankment and Drainage Facilities Repair DO (EA 1V510)
Document Type
NOE - Notice of Exemption
Received
Posted
9/23/2026
Document Description
Caltrans proposes repairing a storm damaged slopes and drainage facilities at multiple locations on State Route (SR-) 1 in San Mateo County from post mile (PM) 15.9 to 17.9. Between April 10 and April 12, 2026, an intense storm system produced heavy rainfall that generated concentrated stormwater runoff, causing erosion of the roadway embankment, damage to drainage facilities, and slope failures. Additional storms between April 20 and April 22 produced further runoff that enlarged the slope failures and continued to undermine the affected embankments. The storm damage has compromised the stability of the roadway embankment and disrupted the drainage system, allowing uncontrolled runoff to continue eroding the slopes. Active erosion remains ongoing and poses an imminent threat to the roadway prism.
The proposed project will remove loose and failed slope material along both sides of SR-1 between PM 15.9 and 17.9. Eroded slopes will then be reconstructed with rock slope protection (RSP) and RSP fabric. Damaged asphalt concrete dikes and drainage features will be restored. The existing approximately 30-foot asphalt concrete ditch at PM 17.9 will be cleaned out both upstream and downstream and then reconstructed. The storm-damaged down drain at PM 15.9 will be removed and a new drainage inlet and asphalt dike will be installed to restore positive drainage and safely convey stormwater runoff away from the repaired embankment. Where necessary, subdrains will be installed to stabilize the repaired slopes. Disturbed areas will be hydroseeded after construction to prevent future erosion. Traffic control will be required during construction.
Contact Information
Name
Juliane Smith
Agency Name
Caltrans
Job Title
Senior Environmental Scientist (NEPA/CEQA Specialist)
Contact Types
Lead/Public Agency / Project Applicant / Parties Undertaking Project
Address
Phone
Email
Location
Cities
Unincorporated San Mateo County (San Gregorio)
Counties
San Mateo
Regions
Northern California, San Francisco Bay Area
State Highways
1
Other Location Info
The project is located on State Route (SR-) 1 in San Mateo County, near San Gregorio, from post mile (PM) 15.9 to 17.9.
Notice of Exemption
Exempt Status
Categorical Exemption
Type, Section or Code
PRC 21084; 14 CCR 15301 Class 1
Reasons for Exemption
Class 1 Existing Facilities. The project is not anticipated to result in any environmental impacts. The project contains a number of standardized project measures which are employed on most, if not all, Caltrans projects and were not developed in response to any specific environmental impacts resulting from the project.
County Clerk
San Mateo
Attachments
Notice of Exemption
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