TO: NAPA COUNTY ZONING ADMINISTRATOR
FROM: Sean Trippi for Brian D. Bordona - Director Planning, Building & Environmental Services
REPORT BY: Hannah Spencer - Planner III
SUBJECT: Marineau-Mes Accessory Structures Viewshed Protection Program P25-00207-VIEW (formerly P25-00121)
RECOMMENDATION
title
MARINEAU-MES ACCESSORY STRUCTURES VIEWSHED PROTECTION PROGRAM / PERMIT NO. P25-00207-VIEW (formerly P25-00121)
CEQA status: Consideration and possible adoption of an Addendum to the previously adopted 2021 Mitigated Negative Declaration prepared for the Marineau-Mes Residence Viewshed (State Clearinghouse Number: 2021020357). Pursuant to CEQA Guidelines Section 15164(b) and Section 15162(a), an addendum to an adopted negative declaration may be prepared if only minor technical changes or additions are necessary or if none of the conditions contained in Section 15162 calling for preparation of a subsequent negative declaration have occurred. This project site is not on any lists of hazardous waste sites enumerated under Government Code Section 65962.5.
Request: Approval of an application under the Viewshed Protection Program, as defined in Chapter 18.106 of the Napa County Code, for the construction of two residential accessory structures within view of Silverado Trail North, a County designated viewshed road. The project consists of a 1,085 square-foot pool house surrounded by a 665 square-foot outdoor patio, a 300 square-foot barn, and a landscape plan that will screen approximately 60% percent of the proposed structures from view from the designated road. The project is located on a 5.67-acre parcel within the Agricultural Watershed (AW) Zoning District and has a General Plan designation of Agriculture, Watershed and Open Space (AWOS). 4000 Silverado Trl N, Angwin, CA 94515. APN: 021-010-079.
Staff Recommendation: Consider the Addendum to the previously adopted 2021 Mitigated Negative Declaration prepared for the Marineau-Mes Residence Viewshed Permit and approve the Marineau-Mes Accessory Structures Viewshed Protection Permit, as conditioned.
Staff Contact: Hannah Spencer, Planner III, 1195 Third St, Suite 210, Napa, CA 94559; (707) 253-4018; Hannah.spencer@countyofnapa.org
Applicant Contact: Jessica Stuenkel with Feldman Architecture Steve & Judith Padis, 1648 Pacific Ave., Suite B San Francisco, CA 94019, (415) 856-9083, or jstuenkel@feldmanarch.com
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EXECUTIVE SUMMARY
PROPOSED ACTIONS:
That the Zoning Administrator:
1. Consider an Addendum to the previously adopted Mitigated Negative Declaration, and adopt the Findings 1-7 in Attachment A.
2. Approve Viewshed Protection Program Application No. P25-00207-VIEW, based on recommended Findings 8-14 in Attachment A, and subject to the recommended Conditions of Approval in Attachment B.
Discussion:
The project consists of a request to approve a Viewshed Protection Program application to construct a 1,085 square-foot pool house and a 300 square-foot barn that sit below a minor ridgeline, on the east side of Silverado Trail. In 2021, the Zoning Administrator approved a viewshed permit for the property’s main residence, accessory dwelling unit, garage, pool and associated improvements under File No. P20-00230. Construction on the existing development is expected to be complete by fall 2025. The proposed pool house and barn are the only structures being considered under File No. P25-00207-VIEW.
The two new accessory structures will be constructed on a hillside visible from Silverado Trail which is identified as a designated public road in the Napa County General Plan and Chapter 18.106 (Viewshed Protection Program) of the Napa County Code (NCC). Therefore, the proposed accessory structures are subject to review for compliance with the Viewshed Protection Program prior to issuance of building permits. Given that the project would result in a combined total of more than 2,500 square feet of accessory structure floor area on the property (1,385 square feet proposed; 2,329 square feet existing), the project does not meet the criteria for administrative review under NCC §18.106.040 and has been scheduled for review by the Zoning Administrator.
As proposed, the project has been designed in substantial conformance with the County’s viewshed protection manual because it would avoid grading on steep slopes and the structures will be substantially screened from view from Silverado Trail primarily by existing and proposed vegetation.
Staff believes all findings can be made in support of the project and recommends approval subject to the recommended conditions of approval.
ENVIRONMENTAL IMPACT
ENVIRONMENTAL DETERMINATION: Consideration and possible adoption of an Addendum to a 2021 adopted Mitigated Negative Declaration (MND). The Addendum concludes the proposed project does not meet any of the requirements in CEQA Guidelines Section 15162 for preparation of a subsequent MND. All previous mitigation measures required for the protection of biological resources and tribal cultural resources have been incorporated into the recommended Conditions of Approval for the project. Additionally, this project is not on any lists of hazardous waste sites enumerated under Government Code Section 65962.5.
BACKGROUND AND DISCUSSION
Owner: Sebastien Marineau-Mes
Applicant: Jessica Stuenkel, Feldman Architecture
Zoning: AW (Agricultural Watershed)
General Plan Designation: AWOS (Agriculture, Watershed, and Open Space)
Application Filed: April 24, 2025
Application Deemed Complete: July 2, 2025
Property Area: 5.67 Acres
Surrounding Uses:
Table 1. Surrounding Land Uses
|
Direction |
Land Uses |
|
North |
Land zoned AW with AWOS General Plan Designation; Residence, Winery, Vineyard, Oak Woodland, Coniferous Forest |
|
East |
Land zoned AW with AWOS General Plan Designation; Residence, Oak Woodland, Coniferous Forest |
|
South |
Land zoned AW with AWOS General Plan Designation; Residence, Vineyard, Coniferous Forest |
|
West |
Land zoned AP with AR General Plan Designation; Vineyards |
Existing Development: The parcel contains a 3,992 square-foot residence, 2,329 square-foot detached garage with an accessory dwelling unit on the second floor, a 120 square-foot pump house and three water tanks, a pool, and landscaping (all currently under construction); a ground mount solar array, one groundwater well, driveway, and approximately 1.84-acres of vineyard (planting in process).
Proposed Structural Development: A 1,085 square-foot pool house with a 665 square-foot outdoor patio and a 300 square-foot barn.
Active Code Compliance Violations: There are no open or pending code violations for the subject property.
Parcel History/Existing Development: In 2020, the project site was heavily impacted by the Glass Fire that damaged vegetation throughout the property and surrounding area. On April 28, 2021, the Zoning Administrator approved the Marineau-Mes Residence Viewshed permit (P20-00230) which requires new and existing vegetation be maintained for visual screening purposes. Specifically, the project included a vegetation retention plan for 12 mature trees consisting of Coast Live Oak, Valley Oak, Black Oak, and Pine; and installation of a variety of shrubs and over 30 new trees, including Coast Live Oak, Southern Magnolia, Oklahoma Redbud, Kousa Dogwood, Arbequina Fruiting Olive.
After a Lot Line Adjustment was processed in 2022, the subject property increased in size from 4.07 acres to 5.67 acres (W21-00497). Later in 2022, the Planning, Building and Environmental Services Department (PBES) began issuing development permits for the Marineau-Mes Residence Viewshed project including the driveway (ENG21-00034), main residence and associated landscaping (BR22-0030), swimming pool (BR24-00207), detached garage with an accessory dwelling unit (BR22-00031), and domestic septic system (E22-00036). In 2024, permits were issued for the pump house (BR24-01818), retaining wall (BR24-01845), and underground domestic propane tank (BR24-01840). Construction on the existing development is expected to be completed by fall 2025. To maintain screening of the residence per the requirements of P20-00230, the landowner is replacing four central screening trees that were lost to delayed environmental impacts of the Glass fire.
The parcel also contains approximately 0.75-acres of vineyard on the valley floor, associated vineyard infrastructure and access, and a groundwater well. Planting for a new 1.09-acre vineyard behind the development area began in spring 2025 and is expected to be completed by fall 2025 (P22-00212-ECP). Approximately 2.34 acres of the property’s fire damaged oak woodland are preserved by deed restriction per condition of approval of P22-00212-ECP.
Currently, one groundwater well serves all water consuming activities on the parcel. The property’s well was constructed in 2012 under E12-00250 and is referred to as the “Upper Well”. Prior to 2022, the property contained a second groundwater well, the “Lower Well”. The Lower Well was decommissioned in May 2022 under E22-00385.
Viewshed Protection Program: According to NCC §18.106.010(A), a primary purpose of the Napa County Viewshed Protection Program is to provide hillside development standards to minimize the impact of man-made structures and grading on views of existing landforms, unique geologic features, existing landscape features and open space as seen from designated public roads within the county. These standards include the protection of “substantial views” where 51 percent or more of the area facing the designated viewshed road can be seen, while NCC §18.106.030(A) states that the Viewshed Protection Program shall apply to all new structures located on slopes of 15% or more. As such, the proposed project is located on slopes exceeding 15%, with 51% or more visibility from certain sections of Silverado Trail, a County designated viewshed road.
To qualify for administrative review under the Viewshed Protection Program per NCC §18.106.040, a project must meet all listed design and siting conditions including a 2,500 square foot limit on combined total accessory structure floor area. Given that the project would add 1,385 square feet of new accessory structure floor area to a property already developed with 2,329 square feet of accessory structures, the project requires Zoning Administrator approval as applied through NCC §18.106.050, with findings for approval that support these requirements found in Attachment A.
Discussion Points: The 5.67-acre property is located on the east side of Silverado Trail, approximately 0.35 miles south of Larkmead Lane and 2.9+/- miles south of the City of Calistoga. General topography of the property consists of relatively flat (0-5%) along Silverado Trail to increasingly steeper slopes (<30%) as you move east toward the mountains. A nearby minor ridgeline located northeast of the site ranges from 768 feet to over 1,700 feet above mean sea level (msl.) Natural vegetative cover in the area includes oak woodland, conifer forest, and non-native grassland. There are no blue-line streams located on the subject property.
The new pool house and barn would be located adjacent to existing structures in a moderately sloped area of the property (12% - 18%) at 320 feet to 324 feet above msl, well below the minor ridgeline. Both structures will meet established zoning setbacks for Silverado Trail and the Agricultural Watershed (AW) zoning district minimum yard requirements, as shown below.
Table 2. Zoning Setbacks
|
Zoning Setback Type |
Required Setback Distance |
Proposed Pool House |
Proposed Barn |
|
Road Setback (Silverado Trail) |
70 feet from road centerline |
> 350 feet |
150 feet |
|
AW Front Yard |
20 feet (beginning at the outer perimeter of the road setback) |
> 370 feet |
> 130 feet |
|
AW Side Yard |
20 feet, or 5 feet per 18.104.140(A) |
> 80 feet |
5 feet |
|
AW Rear Yard |
20 feet, or 5 feet per 18.104.140(A) |
> 200 feet |
> 400 feet |
Due to visibility from Silverado Trail, which is identified as a designated viewshed public road in the Napa County General Plan, as well as average slope exceeding 15%, the project site is subject to Napa County Zoning Ordinance, Chapter 18.106 (Viewshed Protection Ordinance).
As proposed, the project has been designed in substantial conformance with the County’s viewshed protection manual because it would avoid grading on slopes more than 30% and would be located more than 25 feet below the minor ridgeline. As shown in the submitted viewshed analysis, the proposed structures would be visible from Silverado Trail but substantially screened from existing and proposed vegetation. The proposed barn would also benefit from screening provided by existing water tanks and the pump house. Due to relatively small building footprints and use of existing access improvements, the project does not result in substantial changes to the natural landforms and topography. Grading will be limited to the creation of the foundations for the new 1,085 square-foot pool house and surrounding 665 square-foot patio, and the 300 square-foot barn.
Tree/Vegetation Retention and Visual Screening
The project is consistent with the vegetation retention requirements of NCC Section 18.108.020 (Conservation Regulations - General Provisions) in that the project does not propose tree or vegetation canopy removal to accommodate the development. The proposed pool house and barn will be constructed in locations already disturbed by grading and construction activities authorized by prior development approvals.
The project relies on visual screening attained by a combination of existing vegetation, landscaping, and small onsite structures. The landscaping and (three) replacement Coast Live Oak trees associated with the Marineau-Mes Residence Viewshed will provide some screening of the pool house. The pump house and water tanks, as well as vegetation and topography on the adjacent parcel provide partial screening of the barn. To ensure both structures are substantially screened from view from Silverado Trail while maintaining compliance with defensible space requirements, the applicant proposes two additional 48-inch box Coast Live Oak trees installed more than 30-feet from all structures and two 15-gallon Catalina Cherry shrubs installed more than 10-feet from the barn. The hillside vineyard and oak woodland provide a vegetated topographical backdrop for the new structures as viewed from Silverado Trail.
Building Design/Materials
The project consists of a new 22-foot-tall, 1,085 square foot pool house surrounded by a 665 square-foot outdoor patio with trellis, handrails, and a concrete retaining wall and stairs that connect to the existing pool patio. The project also proposes a new 15-foot tall (ridge height), 300 square-foot barn near the vineyard, pump house and water tanks in the southern portion of the property. The architectural design of the two new accessory structures will utilize dark gray cementitious vertical and shingle siding on the main body of the buildings with trim and trellis painted in black, gray concrete and asphalt tile roofing, and low E windows reflecting 10%-15% of visible light. To minimize nighttime light disruption and visual glare, the recommended conditions of approval require all exterior lighting, including landscape lighting, to be shielded and directed downward and away from view of designated public roads. As such, the project would not degrade the existing character of the site and its surroundings, and impacts would be less than significant. The property owner will be required to execute and record in the County Recorder’s office a use restriction, in a form approved by the County Counsel, requiring building exteriors, and existing and proposed screening vegetation be maintained by the owner or the owner’s successors so as to “prevent the project from being viewed from any designated public road” in perpetuity pursuant to NCC §18.106.050(C).
Ephemeral/Intermittent Drainage
Ephemeral drainage courses traverse the project property per Napa County GIS Environmental Maps. However, according to the biological study prepared for the 2021 MND, these non-jurisdictional drainageways do not contain bed-and-bank, ordinary high-water marks, or hydrophytic vegetation and therefore do not meet the definition of an ephemeral stream as defined by NCC 18.108.030. Storm water runoff will be captured in new drainage swales and storm drain inlets to be installed behind the pool house. These new drainage features will tie into the existing drainage system which currently directs runoff away from structures and disperses it through level spreaders in the vineyard in the lower portion of the property.
Water Use
The 2021 MND determined the total projected water demand for the Marineau-Mes Residence viewshed plus the 0.75-acre lower vineyard would result in a modest increase on the demand of groundwater supplies based on Napa County Water Availability Guidance Document, Appendix B. On June 25, 2024, HDVine LLC prepared an updated parcel-specific Water Availability Analysis for the 1.09-acre vineyard project (2024 WAA). The 2024 WAA estimated the property’s total groundwater usage at 1.64 acre-feet per year (AF/yr) and the property’s groundwater recharge to be 2.45 AF/yr, resulting in a net positive water balance of 0.8 AF/yr. Vineyard water demand was estimated at 0.56 AF/yr while the residential uses (main dwelling, accessory dwelling unit, pool, landscaping) were estimated to require 1.08 AF/yr. Conditions of Approval of P22-00212-ECP limit pumping capacity to a maximum of 10 gallons per minute (gpm) to minimize impacts to Dutch Henry Creek, a designated Significant Stream (notated as Biter Creek on some maps), and a neighboring well. Prior to final on the 1.09-acre vineyard, the landowner must install a flow regulation device on the project well.
Considering the property’s 2024 water balance for existing uses is estimated at a net positive of 0.8 AF/yr, and that the proposed new water uses include minor additions to landscaping, a pool house, and no new dwelling units; it can be assumed the project’s increase in water demand will not result in a potentially significant impact to groundwater resources. Even if the proposed water demand matched that of a full-time accessory dwelling unit (0.20 to 0.50 AF/yr based on Appendix B of Napa County Water Availability Guidance Document), the property would still be expected to remain below the annual rate of recharge. Additionally, no increase in water use is assumed for the barn as there are no proposed plumbing fixtures or water lines identified on project plans. Because the existing and proposed estimated groundwater use would be close to 90% of the annual rate of recharge, a condition of approval limiting groundwater use to 2.205 acre-feet per year has been included.
Public Trust
The public trust doctrine requires the state and its legal subdivisions to “consider,” give “due regard,” and “take the public trust into account” when considering actions that may adversely affect a navigable waterway. (Environmental Law Foundation v. State Water Resources Control Bd.; San Francisco Baykeeper, Inc. v. State Lands Com.) There is no “procedural matrix” governing how an agency should consider public trust uses. (Citizens for East Shore Parks v. State Lands Com.) Rather, the level of analysis “begins and ends with whether the challenged activity harms a navigable waterway and thereby violates the public trust.” (Environmental Law Foundation, 26 Cal.App.5th at p. 403.). As demonstrated in the Environmental Law Foundation vs State Water Resources Control Board Third District Appellate Court Case, that arose in the context of a lawsuit over Siskiyou County’s obligation in administering groundwater well permits and management program with respect to Scott River, a navigable waterway (considered a public trust resource), the court affirmed that the public trust doctrine is relevant to extractions of groundwater that adversely impact a navigable waterway and that Counties are obligated to consider the doctrine, irrespective of the enactment of the Sustainable Groundwater Management Act (SGMA).
As noted above, a Water Availability Analysis (WAA) was prepared as part of the vineyard project. The WAA included a review of potential impacts to surface waters due to the proximity of Dutch Henry Creek (notated as Biter Creek on some maps) which is approximately 650 feet west of the project well. The County’s WAA Guidance Document provides well set-back standards and construction criteria in Tables 3, 4 and 5 that if met would be expected to preclude any significant adverse effects on surface waters. Per the WAA Guidance Document, very low flow wells (up to 10 gpm) located 500 feet or more away from a surface water channel would be expected to preclude any significant adverse effects on surface waters. The project well meets this criteria and therefore the County has satisfied its duty to consider impacts to trust resources and no further analysis is required.
Public Comments: On June 5, 2025, staff received a public comment that raises concerns with visual impacts associated with the existing residence, project piecemealing, and future vacation rental use of the property. The commenter requests immediate landscaping and a full review of both viewshed projects (see Attachment H). No other public comments have been received as of the date of this staff report.
Decision Making Options: As noted in the Executive Summary Section above, staff is recommending the Zoning Administrator support the project as summarized in Option 1, below. Decision making options include the following:
Option 1: Approve the Applicant’s Proposal (Staff Recommendation)
Disposition - This action will result in approval of the Viewshed Protection Program Permit for the Marineau-Mes Accessory Structures. Staff recommends this option as, with approval, the request is consistent with all other aspects of the Zoning Ordinance including allowable use, development standards and required setbacks, as well as applicable General Plan policies and other County regulations. Furthermore, there will be no significant environmental impacts resulting from the addition of the two accessory structures, as discussed in the Addendum to the previously adopted Mitigated Negative Declaration as presented in the Recommended Findings (Attachment A).
Action Required - Follow the proposed action listed in the Executive Summary.
Option 2: Modify the Applicant’s Proposal
Disposition - This option will result in the modification of the applicant’s proposal and/or conditions of approval.
Action Required - Make recommendations for an amended scope and or applicable conditions of approval. The item will need to be continued to a future date if significant revisions to the project scope and recommended conditions of approval are desired.
Option 3: Deny the Applicant’s Proposal
Disposition - This option will result in the denial of Viewshed Protection Program Application No. P25-00121-VIEW because it cannot satisfy one or more of the required findings.
Action Required - Zoning Administrator will take tentative action to deny the project, articulating the reasons and grounds for the denial, and remand the matter to staff for preparation of required findings to return to the Zoning Administrator on a specific date.
SUPPORTING DOCUMENTS
A. Recommended Findings
B. Recommended Conditions of Approval
C. CEQA Memo (MND Addendum)
D. 2021 Adopted MND - P20-00230
E. Public Comments
F. Viewshed Application
G. Viewshed Application - Project Plans
H. Graphics
I. 2024 Water Availability Analysis - P22-00212-ECP (includes original 2022 WAA)