ARJOU RESERVOIR DAM AND SPILLWAY REPAIR PROJECT
Summary
SCH Number
2025061409
Public Agency
Napa County
Document Title
ARJOU RESERVOIR DAM AND SPILLWAY REPAIR PROJECT
Document Type
NOE - Notice of Exemption
Received
Posted
6/30/2025
Document Description
The Araujo Reservoir 1 dam requires several improvements to bring the facility into compliance with Division of Safety of Dams (DSOD) requirements. The improvements generally includes the following: (i) measures to enhance the stability of the dam and (ii) construction or improvement of the spillway structures, and (iii) installation or modifications to the emergency outlet conduit facilities. The repair plans include the excavation and removal of the downstream portion of the existing dam embankment; establishment of a seepage barrier (cutoff trench) within the embankment to limit subsequent seepage; installation of internal drainage features to collect and convey seepage through and away from the dam; and reconstruction of the dam embankment with additional height to provide adequate freeboard. Borrow material for the added embankment volume is proposed to be developed from borrow sites adjacent to the dam. The existing spillway structure will be removed and replaced with a new concrete drop inlet type spillway structure with adequate capacity to pass the design stormflow. Below/downstream of the dam embankment, the spillway discharge conduit will be connected to the existing spillway pipe that conveys and discharges stormflows from the reservoir to the primary stream channel below the dam. The control section of the spillway will be constructed to the original spillway elevation (pre-DSOD-required emergency repairs) to restore the original storage capacity of the reservoir. The existing outlet will be removed and replaced with a new outlet conduit that will meet DSOD requirements.
Contact Information
Name
Dana Morrison
Agency Name
County of Napa
Job Title
Supervising Planner
Contact Types
Lead/Public Agency
Address
Phone
Name
David Lounsbury
Agency Name
Wagner & Bonsignore
Job Title
Consulting Civil Engineers
Contact Types
Project Applicant
Phone
Email
Location
Coordinates
Cities
Calistoga
Counties
Napa
Regions
Unincorporated
Cross Streets
Pickett Rd & Rosedale Rd
Zip
94515
Total Acres
162.23
Jobs
1
Parcel #
020-340-030
State Highways
HWY 29, HWY 128
Railways
None
Airports
None
Schools
Calistoga Junior/Senior High, Palisades High, Calistoga Element.
Waterways
Creeks:Simmons,OatHill,Cyrus,DiamondMount,KelletMine,Nash,Selby,Biter,DutchHenry;River:Napa
Township
09N
Range
06W
Section
32
Base
MDM
Notice of Exemption
Exempt Status
Categorical Exemption
Type, Section or Code
Class: Existing Facilities Class 1 Section#: 15301; Class: Replacement & Reconstruction Class 2 Section #: 15302
Reasons for Exemption
The project has been reviewed for compliance with the California Environmental
Quality Act (CEQA). Based on this review it has been determined that this project belongs to the following classes of
categorically exempt projects, which are recognized as having no potential to have a significant effect on the environment,
and therefore is exempt from further environmental review (State CEQA Guidelines, 2015):
-Section 15301, Existing Facilities, Class 1 (d and m): The repair, maintenance, and minor alteration of an existing
facility and mechanical equipment, involving negligible or no expansion of existing or former use including
rehabilitation of deteriorated or damaged structures, facilities, or mechanical equipment to meet current standards
of public health and safety, and repairs and alterations to existing dams and appurtenant structures under the
supervision of the Department of Water Resources. The project is proposing to repair an existing dam and
spillway under the direction of DSOD.
-Section 15302, Replacement and Reconstruction, Class 2(c): The replacement or reconstruction of existing
structures and facilities where the new structure will be located on the same site as the structure replaced, having
substantially the same purpose and capacity as the structure replaced, including the replacement or
reconstruction of existing utility systems and/or facilities involving negligible or no expansion of capacity.
The project site is not listed on any hazardous waste sites enumerated under Government Code Section 65962.5.
County Clerk
Napa
Attachments
Notice of Exemption
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