Napa City Council
September 2, 2025

NAPA HIDDEN GLEN REMEDIATION PROJECT
Draft Initial Study/Mitigated Negative Declaration
July 2025
Prepared for:

City of Napa
Utilities Department
P.O. Box 660
Napa, CA 94559
Prepared by:

RCH Group, Inc.

PO Box 516
Rancho Murieta, CA 95683
916.782.4427
RCHGR:::zup planning & environmental consulting
CITY 01=
NAPA

Napa Hidden Glen Remediation Project i RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

TABLE OF CONTENTS

NAPA HIDDEN GLEN REMEDIATION PROJECT

DRAFT INITIAL STUDY/MITIGATED NEGATIVE DECLARATION
Page
ENVIRONMENTAL CHECKLIST ............................................................................................. 1 Aesthetics ................................................................................................................................ 14 Agricultural and Forest Resources .......................................................................................... 15 Air Quality .............................................................................................................................. 16 Biological Resources .............................................................................................................. 25 Cultural Resources .................................................................................................................. 31 Energy ..................................................................................................................................... 33 Geology and Soils ................................................................................................................... 35 Greenhouse Gas Emissions ..................................................................................................... 42 Hazards and Hazardous Materials .......................................................................................... 51 Hydrology and Water Quality ................................................................................................. 56 Land Use and Land Use Planning ........................................................................................... 64 Mineral Resources .................................................................................................................. 64 Noise ....................................................................................................................................... 65 Population and Housing .......................................................................................................... 72 Public Services ........................................................................................................................ 73 Recreation ............................................................................................................................... 74 Transportation ......................................................................................................................... 75 Tribal Cultural Resources ....................................................................................................... 79 Utilities and Service Systems .................................................................................................. 81 Wildfire ................................................................................................................................... 82 Mandatory Findings of Significance ....................................................................................... 84

APPENDICES
A. Site Photos
B. Remedial Action Plan (RAP)
C. Air Quality, Greenhouse Gas Emissions, & Energy Supporting Information D. Biological Resources Assessment
E. Mitigation Monitoring and Reporting Program (MMRP)

TABLE OF CONTENTS
Page
Napa Hidden Glen Remediation Project ii RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

LIST OF FIGURES
Figure 1. Site Location ......................................................................................................... 4 Figure 2. Site Plan ................................................................................................................. 5 Figure 3. Waste Excavation Plan .......................................................................................... 6 Figure 4. Grading Plan .......................................................................................................... 7 Figure 5. Grading Sections ................................................................................................... 8 Figure 6. Site Access Location ............................................................................................10 Figure 7. Noise Measurement Locations ............................................................................ 68

LIST OF TABLES
Table 1 Summary Of Annual ambient air quality Monitoring Data ................................. 19 Table 2 Estimated Project Average Daily Construction Emissions ................................. 22 Table 3 Special-Status Animals With Potential To Occur Within The Project Site ........ 27 Table 4 Typical Noise Levels ........................................................................................... 66 Table 5 Existing Noise Levels .......................................................................................... 67 Table 6 Typical Construction Equipment Noise Levels (Lmax) ...................................... 70

Napa Hidden Glen Remediation Project 1 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

ENVIRONMENTAL CHECKLIST

ADMINISTRATIVE DRAFT INITIAL STUDY

1. Project Title: Napa Hidden Glen Remediation Project

2. Lead Agency Name and Address: City of Napa
Utilities Department
P.O. Box 660
Napa, CA 94559

3. Contact Person and Phone Number: Chris Jones
Senior Engineer
(707) 257-9460

4. Project Location: APN #045-411-022-000

2.18-acre area
Pascale Place
Napa, CA 94558

5. Project Sponsor: Chris Jones
Senior Engineer
(707) 257-9460

6. General Plan Designation: Open Space & Parks

7. Zoning: RS 10 – Single Family Residential (Minimum Lot Size 10,000 Square Feet)

8. Description of Project:

Project Overview
The City of Napa (the Project Sponsor and Lead Agency) is proposing to conduct remedial action activities on City-owned property (the “Project”) to meet State Minimum Standards and comply with Title 27 of the California Code of Regulations (CCR). The City-owned property is 2.18- acres which includes the former Hidden Glen Dump (approximately 1.06 acres) listed in the CalRecycle Solid Waste Information System (SWIS) database and assigned SWIS NO. 28-AA0028 (the “Project site”). The Project site (APN #045-411-022-000) is near the intersection of Pascale Place and Glory Court in Napa, CA. The parcel is zoned RS 10 (Single Family Residential – Minimum Lot Size 10,000 Square Feet [Sq Ft]) and is designated Open Space & Parks in the City of Napa 2040 General Plan.

The Project site contains waste-impacted soil and debris in shallow soils from when it was operating as the former Hidden Glen Dump and requires remedial action. On November 26, 2019, the County of Napa Environmental Health, Solid Waste Local Enforcement Agency (LEA) issued a letter to the City of Napa requiring submittal of a workplan to ensure that State Minimum

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 2 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Standards are addressed at the City-owned parcel and in compliance with Title 27 of the CCR. To comply with State Minimum Standards, the letter requires the City to remove and/or cover wasteimpacted soil along the flag section and the buffer zone.

A Remedial Action Plan (RAP) was prepared by Ninyo & Moore in October 2024 (Appendix B) and approved by the LEA on December 20, 2024. Under the RAP (and the Project), wasteimpacted soil around the perimeter of the landfill cap (buffer zone and flag section – See Figure 2 – Site Plan) would be excavated to bedrock where feasible, to depths of approximately 10 to 20 inches (See Figure 3 – Waste Excavation Plan). The “buffer zone” is the area between the capped area and the adjacent properties and was created as part of a 2001 project to install a landfill cap over the former dump site. The depth of excavation would be reduced if bedrock is encountered at shallower depths. Conversely, the depth of excavation may extend beyond 20 inches if wastes are deeper to reach bedrock or the excavation may terminate in wastes in which case the wastes would be covered with 2 feet of clean imported soil. The waste-impacted soil to be removed would be reconsolidated onsite and covered with a minimum of two feet of clean fill essentially capping it. Alternatively, the waste-impacted soil may be hauled offsite to an appropriate landfill for disposal.

The planned remedial action activities would be conducted on City-owned property. However, the City is in negotiations to accept waste-impacted soil from the adjacent residential properties and the RAP (and the Project) includes the possibility of accepting waste-impacted soil from adjacent properties. The adjacent include Lots 6 through 10, as shown on Figure 2 – see Construction Phasing and Schedule, below).

Project Site and Objectives
The Project site was initially an excavated quarry that operated into the 1940’s. After quarry operations were abandoned, the Project site was used as a general garbage dump by a private operator until it was abandoned in the 1960’s. In 2001, a landfill cap was installed at the dump site. In 2020, three (3) methane monitoring wells were installed by the City to monitor landfill gases (LFG) based on directive from the LEA (See Appendix B for more details). These wells would remain in place under the Project.

The Project site is a vacant City-owned property and consists of a capped portion of the Hidden Glen Dump and the area between the capped area and the adjacent properties that extends beyond the area that was capped, referred to as the “buffer zone” (see Figure 2). Waste-impacted soils were identified in the buffer zone and flag section that contain elevated lead concentrations and require remediation by the LEA (See Appendix B). Hand digging tools and methods would be used for remediation in the buffer zone, when necessary, to minimize heavy equipment use nearby trees and residences. Remediation of the Project site would be protective to human health and the environment and would aim to meet the applicable State Minimum Standards with respect to waste disposal sites by removing or covering waste-impacted soil exceeding Class I non-RCRA State of California Hazardous Waste Criteria and Residential Environmental Screening Limits for Lead.

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 3 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Figure 1 shows the Site Location and Figure 2 shows the Site Plan. Appendix A contains several photographs of the Project site (i.e., aerials and views of surrounding properties). Figure 3 shows the Waste Excavation Plan, Figure 4 shows the Grading Plan, and Figure 5 shows the Grading Sections.

Surrounding Land Uses and Setting
The 2.18-acre Project site is in a residential setting with adjacent residential properties to the north, east, and south (See Figure 2). The adjacent residential properties are not separated by a road or other features (other than fencing on Lot 5 and portions of fencing on Lots 6, 7, 8 and 9). There are 8 residential structures abutting the City-owned property and the distances between them and the City-owned property line is shown below:

1. 22 Glory Court (Lot 5) – 15 feet (backyard patio is at property line)

2. 18 Glory Court (Lot 6) – 9 feet (deck is at property line)

3. 12 Pascale Place (Lot 9) – 11 feet (backyard patio is essentially at property line)

4. 20 Pascale Place (Lot 11) – 31 feet

5. 10 Pascale Court (Lot 13) – 17 feet (pool and patio is essentially at property line)

6. 29 El Monte Way – 132 feet

7. 33 El Monte Way – 37 feet.

8. 57 El Monte Way – 127 feet (detached garage is 15 feet from property line)

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LOT 5
LOT 9
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LOT 11
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LOT 13

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PARCEL BOUNDARYAPPROXIMATE LIMIT OF CAP
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LOT 8
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4 4.1
REMOVAL 4122 SF,
153 CY
REMOVAL 213 SF

2.8 CY
REMOVAL 2,923 SF
108 CY
REMOVAL 137 SF

1.7 CY
REMOVAL 2316 SF,
57 CY
REMOVAL 101 SF, 1.25 CY
REMOVAL 87 SF,

1.1 CY
REMOVAL 982 SF, 37 CY
REMOVAL 1,090 SF, 33.7 CY
REMOVAL 154 SF
2 CY
REMOVAL 563 SF

17.4 CY

REMOVAL
746 SF
26 CY
REMOVAL 549 SF

20.3 CY
REMOVAL 2,236 SF
14 CY
REMOVAL 1,360 SF
42 CY
REMOVAL 327 SF

11.2 CY
HORIZONTAL AND VERTICAL CONTROL: MAG

NAIL SET IN CURB ON PASCALE PLACE AT
NORTHING 1870374.71 AND EASTING 6484988.00
AT ELEVATION 104.76

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FL MATCH (E)
105.25
TC 105.70
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REMOVAL 79 SF,
1 CY
REMOVAL 1126 SF,
13 CY
REMOVAL 458 SF,
32 CY
REMOVAL 1190 SF

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OF
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APRIL 11, 2025
4/11/25
4/11/25
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SOIL WITH WASTE REMOVAL (10"-20")
SOIL WITH WASTE REMOVAL (21"-30")
RELOCATED SOIL WITH WASTE:

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PROPOSED CONTOUR FOR SOIL WITH WASTE MOUND: 1'-0" INTERVAL TYP.

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REVISIONS

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LOT 12
130'
140'
135'
145'
125'
150'
155'
120'
115'
-230' -225' -220' -215' -210' -205' -200' -195' -190' -185' -180' -175' -170' -165' -160' -155' -150' -145' -140' -135' -130' -125' -120' -115' -110' -105' -100' -95' -85'-90' -80' -75' -65'-70' -60' -55' -45'-50' -40' -35' -25'-30' -20' -15' -10' -5' 0' 5'

APPROXIMATE LIMIT OF LANDFILL CAP PROPERTY LINE
EX. GEOCOMPOSITE DRAINAGE NET &

POLYETHYLENE MEMBRANE
EX. GRADE
EX. TOP SOIL
EX. WASTE
EX. FOUNDATION FILL (18" MIN.) SOIL WITH WASTE FILL, SEE

WASTE EXCAVATION PLAN
135'
145'
140'
150'
130'
155'
LOT 6
125'
120'
0' 5' 10' 15' 20' 25' 30' 40'35' 45' 50' 55' 65'60' 70' 85'80' 90' 95' 105'100' 110' 115' 125'120' 130' 135' 145'140' 150' 155' 165'160' 170' 175' 180' 185' 190' 195' 205'200' 210' 215' 225'220' 230' 235' 240' 245' 250' 255' 260' 265' 270' 275' 280' 290' 295' 285' 300' 305' 310' 315' 320'

LIMIT OF WORK
325'

APPROXIMATE LIMIT

OF LANDFILL CAP PROPERTY LINE
EX. FENCE EX. BEDROCK
2% MIN SLOPE EX. GEOCOMPOSITE DRAINAGE

NET & POLYETHYLENE MEMBRANE

SOIL WITH WASTE FILL, SEE

WASTE EXCAVATION PLAN
2'-0" MIN. OF SOIL CAP 2% MIN SLOPE
EX. GRADE
EX. TOP SOIL
EX. FOUNDATION FILL
(18" MIN.)
EX. WASTE

APPROXIMATE LIMIT OF

LANDFILL CAP
330'
130'
140'
135'
145'
125'
150'
120'
115
-5' 0' 5' 10' 15' 20' 25' 30' 40'35' 45' 50' 55' 70'65'60' 75' 85'80' 90' 95' 105'100' 110' 115' 125'120' 130' 135' 145'140' 75'

LIMIT OF WORK

APPROXIMATE LIMIT OF

LANDFILL CAP
EX. BEDROCK
2% MIN SLOPE
2% MIN SLOPE
2'-0" MIN. OF SOIL CAP

SOIL WITH WASTE FILL, SEE

WASTE EXCAVATION PLAN
EX. GEOCOMPOSITE DRAINAGE

NET & POLYETHYLENE MEMBRANE
EX. WASTE
EX. FOUNDATION FILL (18" MIN.)
EX. TOP SOIL
EX. GRADE

APPROXIMATE LIMIT OF

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EX. FENCE
EX. BEDROCK
EX. BEDROCK
160'
135'
145'
140'
150'
130'
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LOT 6
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120'
160'
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1'-0"
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2'-0"
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1'-0" MIN.
2'-0" MIN. OF SOIL CAP

SOIL WITH WASTE FILL, SEE

WASTE EXCAVATION PLAN
2'-0" MIN. OF SOIL CAP
1'-0" MIN.
11 T:\Projects\2017 Projects\17058_HiddenGlenPark\3_ConstructionDocuments\CutFill\A17058_GD_Accept all Debris_250404.dwg NO.

REVISIONS

DESCRIPTION
DESCRIPTION:

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DATE BY
HORIZ.

SCALE
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DATE
DATE
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VERT.

RH/OP 4/11/25
APRIL 11, 2025
4/11/25
4/11/25

5.1 A17058_GD_Accept all
Debris_250404.dwg
GRADING SECTIONS: ALL WASTE
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-
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ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 9 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Site Access
Access to the site is limited due to the absence of access roads, presence of private properties generally surrounding the site and presence of steep slopes/near vertical quarry walls. The Project site would be accessed through three potential options:

Private Driveway off El Monte Way
An alternative access road would be constructed between the project site and El Monte Way on a private property. This is the City’s preferred option and is shown in Figure 6.

Pascale Place
The site is only accessible via Pascale Place by traversing the western portion of the City of Napa owned Lot A. A temporary road would be constructed up the hillside from Pascale Place to allow access for construction equipment. Portions of the temporary road may be constructed on the adjacent parcel (Lot 8). This is the City’s second option and has not been designed.

No Access Road
In the event the City is unable to secure easements for a temporary access road or if it is infeasible to construct one, the City would need to transfer soil on and off the property at Pascale Place (the only location the City-owned property abuts a public road). This transfer operation would use a portion of the Pascale Place street right of way (traffic access would be maintained with at least one lane with flagger controls) and the flag section of the City-owned property. Soil (clean fill or waste-impacted soil [in the event it is hauled offsite]) would be transferred up and down the slope with an excavator, conveyor belt, or other mechanical equipment.

TEMPORARY CONSTRUCTION ACCESS
EXISTING CONTOUR: 1'-0" INTERVAL TYP.

PROPOSED CONTOUR: 1'-0" INTERVAL TYP.

FIBER ROLL

TEMPORARY FENCE

TREE REMOVAL

1. GRADING: ALL PROPOSED PAVING, CURBS, WALLS, AND PLANTING AREAS SHALL SMOOTHLY CONFORM TO EXISTING ADJACENT FEATURES TO REMAIN.

2. GRADING: CONTRACTOR SHALL PERFORM ALL EARTHWORK AND GRADING PER GEOTECHNICAL ENGINEER'S RECOMMENDATIONS.

3. LANDFILL CAP PROTECTION: REFER TO SPECIAL PROVISIONS SECTION 00 72 00 GENERAL REQUIREMENTS, SECTION 1.3.C FOR LANDFILL CAP PROTECTION REQUIREMENTS.

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HAULING ACCESS T:\Projects\2017 Projects\17058_HiddenGlenPark\3_ConstructionDocuments\CutFill\A17058_GD_Accept all Debris_250404.dwg NO.

REVISIONS

DESCRIPTION
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APRIL 11, 2025
4/11/25
4/11/25
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NOTES

CONSTRUCTION ROUTE

HIDDEN GLEN LOT

LIMIT OF WORK

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 11 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Construction Phasing and Schedule
Construction of the Project is planned over approximately three months from August 2025 through October 2025 but may be delayed to 2026. Construction activities would typically take place Monday through Friday, 8 a.m. to 5 p.m. Approximately 10 workers would be onsite each day during remediation activities.

The Project may also be phased wherein waste-impacted soil from adjacent residential properties is stockpiled on the City-owned property and covered onsite in August 2025 through October 2025 and then site excavation, grading, and capping activities completed in 2026. The RAP (Appendix B) includes provisions and requirements for stockpiling of waste-impacted soil prior to reconsolidation or offsite disposal.

Site grading and excavation equipment would be used during all phases and include a large excavator, mini excavator, backhoe, loader, dozer, compactor, and dump trucks. Hand digging tools and methods would be used for remediation in the buffer zone, when necessary, to minimize heavy equipment use nearby residences.

A maximum of 3,500 cubic yards of waste-impacted soil could be excavated from the Cityowned property and accepted from adjacent residential properties under the Project, which would be consolidated onsite and capped with clean fill or hauled offsite. If hauled offsite, wasteimpacted soil would be transported to Kettleman Hills Class I non-RCRA hazardous waste landfill and Altamont Class II non-hazardous waste landfill. A maximum of 6,050 cubic yards of clean soil fill would be imported to the site under the Project.

Health and Safety Plans
Site Health and Safety Plan
The Project includes a Site Health and Safety Plan (SHSP) that provides policies, information, requirements, and guidelines regarding procedures to be followed by field personnel, subcontractors, and other staff during implementation of the Project. The SHSP is prepared in general accordance with the Federal Occupational Safety and Health (OSHA) Administration Hazardous Waste Operations and Emergency Response Plans, as well as applicable California CCR requirements. See Appendix B (Appendix D of the RAP) for the Project SHSP.

Community Health and Safety Plan
The Project includes a Community Health and Safety Plan (CHSP) that provides measures to protect the public and surrounding land uses from the potential health hazards during future onsite construction activities. See Appendix B (Appendix E of the RAP) for the Project CHSP.

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 12 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

9. Required Agency Approvals:

The Project requires City of Napa’s discretionary approval of the award of a contract to complete the construction of the Project.

10. Tribal Consultation:

The City of Napa notified the following tribes requesting Assembly Bill (AB) 52 notification for projects subject to CEQA:

1. Confederated Villages of Lisjan Nation

2. Yocha Dehe Wintun Nation
The City sent project notification letters via certified mail to both tribes and neither tribe requested formal consultation within 30 days of receipt of the notification letter. ___________________

ATTACHMENT 4

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 14 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

AESTHETICS
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

1. AESTHETICS — Except as provided in Public
Resources Code Section 21099, would the proposed
project:

a) Have a substantial adverse effect on a scenic vista? ☐ ☐ ☒ ☐ b) Substantially damage scenic resources, including, but not limited to, trees, rock outcroppings, and historic
buildings within a state scenic highway?
☐ ☐ ☐ ☒
c) In non-urbanized areas, substantially degrade the
existing visual character or quality of public views of the site and its surroundings? (Public views are those
that are experienced from publicly accessible vantage
point. If the project is in an urbanized area, would the project conflict with applicable zoning and other
regulations governing scenic quality?
☐ ☐ ☒ ☐
d) Create a new source of substantial light or glare
which would adversely affect daytime or nighttime
views in the area?
☐ ☐ ☐ ☒
Discussion
a, c) Less-than-Significant Impact. Visual resources can be valued both objectively and subjectively based on their uniqueness, prominence, quality, relationship to community identity, and economic contributions, such as to land values and tourism. Visual resources are important from an aesthetic perspective when, based on the characteristics listed above, they are identified as containing significant scenic value. Within this understanding, a scenic vista can be defined as the public view of an area that is visually or aesthetically unique, such as a valley or a mountain range.

The Project site is private City-owned property that is currently vacant and covered with perennial grasses that are periodically mowed down. Surrounding views at the Project site include views of the adjacent residential properties and quarry walls/cliffs (see Appendix A for photographs of the surrounding views). The existing views of the Project site do not constitute an identifiable scenic vista or scenic viewshed.

Once operational, the waste-impacted soil would be reconsolidated onsite and covered with 2 feet of clean fill essentially capping it or hauled offsite to an appropriate landfill for disposal. If the waste-impacted soil is kept onsite, the grade of the vacant lot would be raised by several feet. Furthermore, waste-impacted soil from adjacent properties could be stockpiled on the Project site and covered with plastic sheeting (pursuant to RAP requirements) for up to one year. However, since there are no identifiable scenic vistas at the Project site, the increase in grade and/or temporary covered waste-impacted soil stockpile would not block any views of nearby scenic vistas. Thus, development of the Project would not result in substantial adverse effects to scenic vistas. Furthermore, raising the grade of the lot by several feet would not degrade the existing visual character

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 15 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 of the site or quality of views of the quarry walls, and the temporary covered wasteimpacted soil stockpile (if necessary) would not result in permanent changes to the visual character or quality of views of the site. The Project would not conflict with applicable zoning and other regulations governing scenic quality. Therefore, the Project would result in a less-than-significant impact.
b) No Impact. The Project site is not within or near a designated state scenic highway.

There are no identifiable scenic resources within the Project site, such as historic buildings or rock outcroppings. The Project would not substantially damage scenic resources within a state scenic highway. Therefore, the Project would result in no impact. d) No Impact. There is currently no lighting at the Project site. The Project would not introduce new lighting that would affect daytime or nighttime views of the area.

Therefore, the Project would result in no impact.
_________________________

AGRICULTURAL AND FOREST RESOURCES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

2. AGRICULTURAL AND FOREST RESOURCES —
In determining whether impacts to agricultural resources are significant environmental effects, lead agencies may refer to the California Agricultural Land Evaluation and Site Assessment Model (1997) prepared by the California Dept. of Conservation as an optional model to use in assessing impacts on agriculture and farmland. In determining whether impacts to forest resources, including timberland, are significant environmental effects, lead agencies may refer to information compiled by the California Department of Forestry and Fire Protection regarding the state’s inventory of forest land, including the Forest and Range Assessment Project and the Forest Legacy Assessment project; and forest carbon measurement methodology provided in Forest Protocols adopted by the California Air Resources Board.

Would the proposed project:
a) Convert Prime Farmland, Unique Farmland, or Farmland of Statewide Importance (Farmland), as shown on
the maps prepared pursuant to the Farmland Mapping
and Monitoring Program of the California Resources
Agency, to non-agricultural use?
☐ ☐ ☐ ☒
b) Conflict with existing zoning for agricultural use, or a Williamson Act contract? ☐ ☐ ☐ ☒
c) Conflict with existing zoning for, or cause rezoning of, forest land (as defined in Public Resources Code
section 12220(g)), timberland (as defined by Public
Resources Code section 4526), or timberland zoned
Timberland Production (as defined by Government
Code section 51104(g))?
☐ ☐ ☐ ☒
d) Result in the loss of forest land or conversion of
forest land to non-forest use? ☐ ☐ ☐ ☒
e) Involve other changes in the existing environment
which, due to their location or nature, could result in conversion of Farmland to non-agricultural use or
conversion of forest land to non-forest use?
☐ ☐ ☐ ☒

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 16 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Introduction
The Project site is zoned Open Space & Parks in the City’s 2040 General Plan. The Project site includes no forest land, timberland, or agricultural use, and is not under a Williamson Act contract.

Discussion
a) No Impact. The Project site does not contain any areas of Farmland of Statewide Importance. The Project site would not convert any farmland or agricultural uses to nonagricultural uses. Therefore, the Project would result in no impact. b) No Impact. The Project site has not been used for agriculture and is not under a Williamson Act contract. Therefore, the Project would result in no impact. c, d) No Impact. There are no areas classified as forest land, timberland, or farmland within the vicinity of the Project that may be affected by the development of the Project.

Therefore, the Project would result in no impact.
e) No Impact. The Project would not result in loss of farmland or forest land. Therefore, the Project would result in no impact.
_________________________

AIR QUALITY
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

3. AIR QUALITY —
Where available, the significance criteria established by the applicable air quality management district or air pollution control district may be relied upon to make the following determinations.

Would the proposed project:
a) Conflict with or obstruct implementation of the
applicable air quality plan? ☐ ☐ ☒ ☐
b) Result in a cumulatively considerable net increase of any criteria pollutant for which the project region is
non-attainment under an applicable federal or state
ambient air quality standard?
☐ ☒ ☐ ☐
c) Expose sensitive receptors to substantial pollutant
concentrations? ☐ ☐ ☒ ☐
d) Result in other emissions (such as those leading to
odors) adversely affecting a substantial number of
people?
☐ ☐ ☒ ☐
Introduction
This section describes construction air quality impacts associated with the Project and is consistent with the methods described in the Bay Area Air Quality Management District

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 17 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 (BAAQMD) CEQA Air Quality Guidelines (BAAQMD, 2023). Detailed modeling assumptions and results are provided in Appendix C.

Setting
The Project site is located within the San Francisco Bay Area Air Basin (Air Basin), which encompasses Alameda, Contra Costa, Santa Clara, San Francisco, San Mateo, Marin, and Napa Counties, and the southern portions of Solano and Sonoma Counties.

Climate, Meteorology, and Topography
Air quality is affected by the rate, amount, and location of pollutant emissions and the associated meteorological conditions that influence pollutant movement and dispersal. Atmospheric conditions, including wind speed, wind direction, stability, and air temperature, in combination with local surface topography (i.e., geographic features such as mountains, valleys, and San Francisco Bay), determine the effect of air pollutant emissions on local air quality.

The climate of the Air Basin, including Napa, is a Mediterranean-type climate characterized by warm, dry summers and mild, wet winters. During summer and fall, conditions are favorable to the formation of photochemical pollutants, such as ozone and secondary particulates, such as sulfates and nitrates.

Criteria Air Pollutants
Concentrations of “criteria” air pollutants (“criteria” air pollutants are state and/or federally regulated) are used to indicate the quality of the air. These include ozone, carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter less than 10 micrometers (coarse or PM10), particulate matter less than 2.5 micrometers (fine or PM2.5), and lead. Regulation of air pollutants is achieved through both national and state ambient air quality standards (AAQS), and emissions limits for individual sources. Regulations implementing the federal Clean Air Act established national ambient air quality standards (NAAQS) for the six criteria pollutants.

California has adopted more stringent California ambient air quality standards (CAAQS) for most of the criteria air pollutants. In addition, California has established CAAQS for sulfates, hydrogen sulfide, vinyl chloride, and visibility-reducing particles. There are considerable differences between state and federal standards in California.

The AAQS are intended to protect the public health and welfare, with an adequate margin of safety. They are designed to protect those segments of the public most susceptible to respiratory distress, known as sensitive receptors, including asthmatics, the very young, elderly, people weak from other illness or disease, or persons engaged in strenuous work or exercise. Healthy adults can tolerate occasional exposure to air pollution levels somewhat above the ambient air quality standards before adverse health effects are observed.

Under amendments to the federal Clean Air Act, United States Environmental Protection Agency (U.S. EPA) has classified air basins or portions thereof, as either in “attainment” or “nonattainment” for each criteria air pollutant, based on whether or not the NAAQS have been achieved. The California Clean Air Act, which is patterned after the federal Clean Air Act, also

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 18 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 requires areas to be designated as in “attainment” or “non-attainment” for the CAAQS. Thus, areas in California have one set of attainment / non-attainment designation with respect to the NAAQS and another set with respect to the CAAQS.

The Bay Area is currently designated “non-attainment” for 1-hour and 8-hour ozone CAAQS, the 8-hour ozone NAAQS, the PM10 CAAQS (annual and 24-hour), and the PM2.5 CAAQS (annual) and NAAQS (24-hour). The Bay Area is “attainment” or “unclassified” with respect to the other ambient air quality standards. Based upon the Bay Area’s attainment status, pollutants of greatest concern include criteria pollutant emissions such as nitrogen oxides (NOx) 1 , volatile
organic compounds (VOC) as reactive organic gases (ROG)2 , PM10, and PM2.5.3
Toxic Air Contaminants
Toxic air contaminants (TACs) are regulated under both state and federal laws. Federal laws use the term “Hazardous Air Pollutants” (HAPs) to refer to the same types of compounds that are referred to as TACs under state law. Both terms encompass essentially the same contaminants.

Under the 1990 Federal Clean Air Act Amendments, 189 substances are regulated as HAPs.

With respect to state law, in 1983 the California legislature adopted Assembly Bill 1807 (AB 1807), which establishes a process for identifying TACs and provides the authority for developing retrofit air toxics control measures on a statewide basis. Air toxics in California may also be regulated by the Air Toxics “Hot Spots” Information and Assessment Act of 1987 (Assembly Bill [AB] 2588). Under AB 2588, TACs from individual facilities must be quantified and reported to the local air pollution control agency. The facilities are then prioritized by the local agencies based on the quantity and toxicity of these emissions, and on their proximity to areas where the public may be exposed. In establishing priorities, the air districts are required to consider the potency, toxicity, quantity, and volume of hazardous materials released from the facility, the proximity of the facility to potential receptors, and any other factors that the air district determines may indicate that the facility may pose a significant risk. High-priority facilities are required to perform a Health Risk Screening Assessment (HRSA), and if specific risk thresholds are exceeded, they are required to communicate the results to the public in the form of notices and public meetings. Depending on the health risk levels, emitting facilities can be required to implement varying levels of risk reduction measures. California Air Resources Board (CARB) identified approximately 200 TACs, including the 189 federal HAPs, under AB 2588.
1 When combustion temperatures are extremely high, as in aircraft, truck and automobile engines, atmospheric nitrogen combines with oxygen to form various oxides of nitrogen (NOX). Nitric oxide (NO) and NO2 are the most significant air pollutants generally referred to as NOX. Nitric oxide is a colorless and odorless gas that is relatively harmless to humans, quickly converts to NO2 and can be measured. Nitrogen dioxide has been found to be a lung irritant capable of producing pulmonary edema. 2 VOC means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions and thus, a precursor of ozone formation.

ROG are any reactive compounds of carbon, excluding methane, CO, carbon dioxide, carbonic acid, metallic carbides or carbonates, ammonium carbonate, and other exempt compounds. The terms VOC and ROG are often used interchangeably. 3 PM10 and PM2.5 consists of airborne particles that measure 10 micrometers or less in diameter and 2.5 micrometers or less in diameter, respectively. PM10 and PM2.5 represent fractions of particulate matter that can be inhaled into the air passages and the lungs, causing adverse health effects.

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 19 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Local Air Quality
The BAAQMD maintains a network of monitoring stations within the Air Basin that monitor air quality and compliance with applicable ambient standards. The monitoring station closest to the Project site is the Vallejo-Fairfield Monitoring Station at 304 Tuolumne Street, approximately eight miles south of the Project site. The Vallejo-Fairfield Monitoring Station measures levels of CO, ozone, PM2.5, SO2, and NO2. The Vacaville Monitoring Station measures levels of PM10 at Merchant Street, approximately 17 miles to the northeast of the Project site.

Table 1 summarizes the most recent three years of data (2022 through 2024) from BAAQMD’s Vallejo-Fairfield and Vacaville Monitoring Stations. The ozone and PM10 standards were not exceeded. The PM2.5 standard was exceeded in 2022, 2023, and 2024. No other standards were exceeded during the three-year period.

TABLE 1 SUMMARY OF ANNUAL AMBIENT AIR QUALITY MONITORING DATA Pollutant Standarda 2022 2023 2024
Carbon Monoxide
Highest 1-Hour Average (ppm)b 20 11.5 2.1 4.9
Highest 8-Hour Average (ppm)b 9 1.8 1.6 4.9
Ozone
Highest 1-Hour Average (ppm)b 0.090 0.058 0.053 0.043
Highest 8-Hour Average (ppm)b 0.070 0.066 0.071 0.046
Coarse Particulate Matter (PM10)
c
Highest 24-Hour Average (g/m3)
b 50 31 37 14.2
State Annual Average (g/m3)b 20 8.12 6.46 4.99
Fine Particulate Matter (PM2.5)
Highest 24-Hour Average (g/m3)
b
35 35 38 26
State Annual Average (g/m3)
b
12/9 12.0 12.3 11.2
Nitrogen Dioxide (NO2)
Highest 1-Hour Average (ppm)b 0.180/0.100 0.044 0.044 0.069 Annual Average (ppm) b 0.030/0.053 0.007 0.006 0.010
NOTES: Values in bold are in excess of at least one applicable standard. a. Generally, state standards and national standards are not to be exceeded more than once per year. b. ppm = parts per million; g/m3 = micrograms per cubic meter. c. PM10 is not measured every day of the year. Number of estimated days over the standard is based on 365 days per year.

Source: United States Environmental Protection Agency, AirData, https://www.epa.gov/outdoor-air-quality-data/interactive-mapair-quality-monitors Regional Air Quality Plans
The 1977 Clean Air Act amendments require that regional planning and air pollution control agencies prepare a regional Air Quality Plan to outline the measures by which both stationary and mobile sources of pollutants can be controlled in order to achieve all standards specified in the Clean Air Act. The 1988 California Clean Air Act also requires development of air quality plans and strategies to meet state air quality standards in areas designated as non-attainment (with the exception of areas designated as non-attainment for the state PM standards). Maintenance plans are required for attainment areas that had previously been designated non-attainment in order to I I
I I
I I
I I

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Draft Initial Study/Mitigated Negative Declaration July 2025 ensure continued attainment of the standards. Air quality plans developed to meet federal requirements are referred to as State Implementation Plans.

Bay Area ozone levels have been greatly reduced in recent years, but the region still does not fully attain the CAAQS and NAAQS. The California Clean Air Act, as codified in the California Health and Safety Code, requires air districts that do not attain state ozone standards to prepare ozone plans. To that end, BAAQMD’s 2017 Clean Air Plan serves to update the most recent Bay Area ozone plan, the 2010 Clean Air Plan. The Health and Safety Code requires that ozone plans propose a control strategy to reduce emissions of ozone precursors—ROG and NOx—and reduce transport of ozone and its precursors to neighboring air basins. The control strategy must either reduce emissions five percent or more per year or include “all feasible control measures.” Because reducing emissions of ozone precursors by five percent per year is not achievable, the control strategy for the 2017 Clean Air Plan is based on the “all feasible measures” approach.

Sensitive Receptors
Land uses such as schools, children’s daycare centers, hospitals, and convalescent homes are considered to be more sensitive than the general public to poor air quality because the population groups associated with these uses have increased susceptibility to respiratory distress. Persons engaged in strenuous work or exercise also have increased sensitivity to poor air quality. The CARB has identified children less than 14 years of age, the elderly over 65 years of age, athletes, and those with cardiovascular and chronic respiratory diseases as most likely to be affected by air pollution. These groups are classified as sensitive population groups.

Residential areas are considered more sensitive to air quality conditions than commercial and industrial areas, because people generally spend longer periods of time at their residences, resulting in greater exposure to ambient air quality conditions. Recreational uses are also considered sensitive, due to the greater exposure to ambient air quality conditions and because the presence of pollution detracts from the recreational experience. According to the BAAQMD, workers are not considered sensitive receptors because all employers must follow regulations set forth by the Occupation Safety and Health Administration to ensure the health and well-being of their employees.

BAAQMD considers the relevant zone of influence for an assessment of air quality health impacts to be within 1,000 feet of a project site. There are eight adjacent residential receptors4 on
properties that share a property line with the Project site and many more within 1,000 feet as you move away from the site to the north, east, south, and southwest. Silverado Middle School is approximately ¼ mile east of the Project site.

Significance Criteria
As stated in Appendix G of the CEQA Guidelines, the significance criteria established by the applicable air quality district may be relied upon to make the determinations. Thus, according to 4 See Project Description for the distances of the nearest residential structures to the Project property line.

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Draft Initial Study/Mitigated Negative Declaration July 2025 BAAQMD’s CEQA Guidelines, the Project would result in a significant impact to air quality if it would result in the following:
 Average daily construction exhaust emissions of 54 pounds per day of ROG, NOx, or PM2.5 or 82 pounds per day of PM10;
 Average daily operation emissions of 54 pounds per day of ROG, NOx, or PM2.5 or 82 pounds per day of PM10; or result in maximum annual emissions of 10 tons per year of ROG, NOx, or PM2.5 or 15 tons per year of PM10;
 Exposure of sensitive receptors to substantial levels of TAC resulting in (a) a cancer risk level greater than 10 in one million, (b) a noncancerous risk (chronic or acute) hazard index greater than 1.0, or (c) an increase of annual average PM2.5 of greater than 0.3 micrograms per cubic meter (µg/m3
).
 Frequently and for a substantial duration, create or expose sensitive receptors to substantial objectionable odors affecting a substantial number of people.

Discussion
a) Less-than-Significant Impact. BAAQMD’s 2017 Clean Air Plan provides a roadmap for BAAQMD’s efforts to reduce air pollution and protect public health and the global climate. Determination of whether a project supports the goals in the 2017 Clean Air Plan is achieved by a comparison of project-estimated emissions with BAAQMD thresholds of significance. If project emissions would not exceed the thresholds of significance after the application of all feasible mitigation measures, the project is consistent with the goals of the 2017 Clean Air Plan. As presented in the subsequent impact discussions, the Project would not exceed the BAAQMD significance thresholds; therefore, it would not conflict with the goals of the 2017 Clean Air Plan and would not hinder implementation of any of the control measures. Therefore, the Project would result in a less-thansignificant impact. b) Less-than-Significant Impact with Mitigation. The Project would generate air pollutant emissions during temporary construction activities. Construction-related activities would generate air pollutant emissions from off-road equipment, on-road trucks, and worker automobiles. Fugitive dust emissions would also be generated by ground disturbance and would vary as a function of soil silt content, soil moisture, wind speed, and acreage of disturbance. Construction emissions were estimated using the California Emissions Estimator Model (CalEEMod) Version 2022.1.1.29 (CAPCOA, 2022) and are summarized in Table 2. Detailed modeling assumptions and results are provided in Appendix C.

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Draft Initial Study/Mitigated Negative Declaration July 2025 TABLE 2 ESTIMATED PROJECT AVERAGE DAILY CONSTRUCTION EMISSIONS Condition
ROG
lbs/day
NOx
lbs/day
PM10 1
lbs/day
PM2.5 1
lbs/day
Construction 1.59 16.3 0.65 0.59
BAAQMD Thresholds of Significance 54 54 82 54
Potentially Significant? No No No No
NOTES:
1 PM10 and PM2.5 construction thresholds of significance apply to exhaust emission only. Fugitive PM10 and PM2.5 (fugitive dust) are less than significant assuming required best management practices are implemented.

SOURCE: CAPCOA, 2022.

BAAQMD’s CEQA Air Quality Guidelines require that projects implement all the BAAQMD’s basic best management practices (BMPs) for a project to have a less than significant construction-related fugitive dust emissions impact. Therefore, the Project would implement the required BMPs through Mitigation Measure AQ-1 and construction would result in a less-than-significant impact with mitigation.

Mitigation Measure AQ-1: The applicant shall implement the following during construction of the Project:
 All exposed surfaces (e.g., parking areas, staging areas, soil piles, graded areas, and unpaved access roads) shall be watered two times per day.  All haul trucks transporting soil, sand, or other loose material off site shall be covered.
 All visible mud or dirt track-out onto adjacent public roads shall be removed using wet power vacuum street sweepers at least once per day. The use of dry power sweeping is prohibited.
 All vehicle speeds on unpaved roads shall be limited to 15 miles per hour.  All roadways, driveways, and sidewalks to be paved shall be completed as soon as possible. Building pads shall be laid as soon as possible after grading unless seeding or soil binders are used.
 All excavation, grading, and/or demolition activities shall be suspended when average wind speeds exceed 20 mph.
 All trucks and equipment, including their tires, shall be washed off prior to leaving the site.
 Unpaved roads providing access to sites located 100 feet or further from a paved road shall be treated with a 6- to 12-inch layer of compacted wood chips, mulch, or gravel.

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Draft Initial Study/Mitigated Negative Declaration July 2025  A publicly visible sign shall be posted with the telephone number and the person to contact the City regarding dust complaints. This person shall respond and take corrective action within 48 hours. The BAAQMD’s phone number shall also be visible to ensure compliance with applicable regulations.

The BAAQMD CEQA Air Quality Guidelines recommend that cumulative air quality effects from criteria air pollutants also be addressed by comparison to the mass daily and annual thresholds. These thresholds were developed to identify a cumulatively considerable contribution to a significant regional air quality impact. As described, the Project-related construction emissions would be below the significance thresholds.

Therefore, the Project would not be cumulatively considerable, and cumulative impacts would be less-than-significant.
c) Less-than-Significant Impact. Health effects are generally evaluated based on a longterm (30 years) of exposure. According to the BAAQMD, the project type is not one that would require a health risk assessment for CEQA purposes because it is short-term (approximately two to three months) and would not generate substantial TAC pollutant concentrations. As shown, in Table 2, PM2.5 emissions from exhaust (diesel particulate matter), would be roughly one percent of the threshold and any TACs in waste-impacted soils disturbed by the Project would be controlled through BMPs in Mitigation Measure AQ-1 and the CHSP (see Appendix B). The CHSP provides measures to protect the public and surrounding land uses from the potential health hazards during future on-site construction activities. Furthermore, remediation of the Project site would be protective to human health and the environment through the removal or covering of waste-impacted soil, exceeding Class I non-RCRA State of California Hazardous Waste Criteria and Residential Environmental Screening Limits for Lead. Thus, impacts during construction would not expose sensitive receptors to substantial pollutant concentrations. Therefore, the Project would have a less-than-significant impact.
d) Less-than-Significant Impact. With respect to the Project, diesel-fueled construction equipment and haul truck exhaust would generate some odors. However, these emissions typically dissipate quickly and would be unlikely to affect a substantial number of people.

Therefore, the Project would result in a less-than-significant impact.

References
Bay Area Air Quality Management District, Bay Area Climatology, October 4, 2010. http://www.baaqmd.gov/Divisions/Communications-and-Outreach/Air-Quality-in-the-BayArea/Bay-Area-Climatology.aspx Bay Area Air Quality Management District, 2017 Clean Air Plan, April 20, 2017, http://www.baaqmd.gov/~/media/files/planning-and-research/plans/2017-clean-airplan/attachment-a_-proposed-final-cap-vol-1-pdf.pdf?la=en

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Draft Initial Study/Mitigated Negative Declaration July 2025 Bay Area Air Quality Management District, Air District, About the Air District, In Your Community, Napa County. April 21, 2017, https://www.baaqmd.gov/en/about-the-airdistrict/in-your-community/napa-county Bay Area Air Quality Management District, California Environmental Quality Act Air Quality Guidelines, April 20, 2023, https://www.baaqmd.gov/plans-and-climate/californiaenvironmental-quality-act-ceqa/updated-ceqa-guidelines California Air Pollution Officers Association, California Emissions Estimator Model User Guide Version 2022.1, April 2022, http://www.caleemod.com/
United States Environmental Protection Agency, AirData, https://www.epa.gov/outdoor-airquality-data/interactive-map-air-quality-monitors _________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

BIOLOGICAL RESOURCES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

4. BIOLOGICAL RESOURCES — Would the proposed
project:

a) Have a substantial adverse effect, either directly or through habitat modifications, on any species identified as a candidate, sensitive, or special-status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Game or
U.S. Fish and Wildlife Service?
☐ ☒ ☐ ☐
b) Have a substantial adverse effect on any riparian
habitat or other sensitive natural community identified in local or regional plans, policies, regulations or by the California Department of Fish and Game or
U.S. Fish and Wildlife Service?
☐ ☐ ☐ ☒
c) Have a substantial adverse effect on state or federally protected wetlands (including, but not limited to,
marsh, vernal pool, coastal, etc.) through direct
removal, filling, hydrological interruption, or other
means?
☐ ☐ ☐ ☒
d) Interfere substantially with the movement of any
native resident or migratory fish or wildlife species or with established native resident or migratory wildlife
corridors, or impede the use of native wildlife nursery sites?
☐ ☐ ☐ ☒
e) Conflict with any local policies or ordinances
protecting biological resources, such as a tree
preservation policy or ordinance?
☐ ☒ ☐ ☐
f) Conflict with the provisions of an adopted Habitat
Conservation Plan, Natural Community Conservation
Plan, or other approved local, regional, or state
habitat conservation plan?
☐ ☐ ☒ ☐
Introduction
This section is based on a Biological Resources Assessment (BRA) conducted by Swift Biological Consulting, LLC (Swift Biological) in April 2025. The BRA is provided in Appendix D. The BRA includes a literature review as well as field surveys conducted on March 19, 2025, and April 8, 2025. The field surveys were conducted to document existing site conditions and the potential presence of special-status biological resources (i.e., federal- and state-listed plant and wildlife species, sensitive natural communities, jurisdictional waters and wetlands, habitat for nesting birds, and wildlife migration areas). The findings of the BRA are utilized in this section to evaluate the Project’s potential impacts to biological resources.

Discussion
a) Less than Significant Impact with Mitigation. Based on background review, a list of special-status plants and animals with the potential to occur within the Project site was generated. Only the special-status species that are present onsite or have the potential to occur onsite are discussed in this analysis.

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Draft Initial Study/Mitigated Negative Declaration July 2025 Plant and animal species with no potential to occur onsite or that are not expected to occur onsite are not addressed further in this analysis. For a full list of plant and animal species that are not expected to occur onsite, see the BRA provided in Appendix D.

No special-status plants were observed during the field surveys. Native soils and intact native plant communities are absent from the Project site due to the long history of disturbance from when the Project site operated as a rock quarry and then as a dump site. The Project area is highly disturbed, making it unsuitable for specialstatus plants to occur. In addition, the Project site lacks the hydrological and topographical conditions to support special-status plant species. Thus, the Project would not impact special-status plants (Appendix D).

During the field surveys, two special-status animal species were observed onsite.

These include the Oak titmouse (Baeolophus inornatus) and Nuttall’s woodpecker (Dryobates nuttallii). Both are United State Fish and Wildlife Service (USFWS) Birds of Conservation Concern (BCC) and common birds of oak woodlands and wooded suburban areas in Napa County (Appendix D). The Project site includes areas that support habitat for these protected nesting birds. Due to the Project’s native trees and understory vegetation, roosting bats have a moderate potential to occur onsite. See Table 3 for special-status animals that occur or have the potential to occur within the Project site.

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Draft Initial Study/Mitigated Negative Declaration July 2025 TABLE 3 SPECIAL-STATUS ANIMALS WITH POTENTIAL TO OCCUR WITHIN THE

PROJECT SITE
Common
Name
Scientific
Name
Listing
Status1 Habitat Requirements
Local Observations and
Potential for Occurrence
within the Project Site
Oak
Titmouse
Baeolophus
inornatus
BCC Small, brown-tinged gray bird with small crest.

Occurs in oak woodlands and open pine or mixed
oak-pine forests. Feeds among the branches and
larger twigs of trees for insects among the foliage
and bark. Feeds primarily on insects, nuts, and
seeds. Pairs mate for life and defend territories yearround. Nest in cavities of trees or nest boxes. A yearround resident in Napa County.

Present. Species observed
within the Project site. Suitable
foraging and
nesting habitat is present in the
oak trees onsite.

Nuttall’s
Woodpecker
Dryobates
nuttallii
BCC Small woodpecker of oak woodland habitats. Feeds
primarily on insect larvae by tapping and probing
into the crevices of oak trees. This species is found
year-round in oak woodlands, wooded suburban
areas, and near streams. This species is nonmigratory. It occurs throughout California’s oak woodland communities but extends into Baja,
Mexico. A cavity nesting species. Males excavate
out a cavity in a dead tree. They form monogamous
pairs and will defend their territories year-round. A
permanent resident in Napa County oak woodlands.

Present. Species observed
within the Project site. Suitable
foraging and nesting habitat is
present in the oak trees onsite.

Pallid Bat
Antrozous
pallidus
SSC Grassland, shrubland, forest, and woodland habitats from sea level up through mixed coniferous forests.

Found from south-central British Colombia to
central Mexico and Cuba. Most common in open,
dry habitats with rocky areas for roosting. A social
species forming small colonies. Roosting sites
include caves, mines, crevices, buildings, and
hollow trees during the day, and more open sites are
used at night. Feed on a variety of insects and
arachnids; most prey are taken on the ground. The
mating season ranges from October to February. One
to three (typically twins) pups are born from April to
July. A yearlong resident throughout most of its
range.

Moderate potential. The Pallid
Bat is reported from multiple
sightings within 5 miles of the
Project site. Bats may forage
over the Project site. Some of
the larger trees may provide
limited roosting habitat.

NOTES:
1 Animal Listing Status Codes: BCC-USFWS Bird of Conservation Concern; SSC-California Department of Fish and Wildlife (CDFW) Species of Special Concern.

SOURCE: Swift Biological, 2025. (Appendix D)
As shown in Table 3, two special-status animal species were observed onsite, and another special-status species has moderate potential to occur onsite. Due to the construction needed for remediation activities (i.e., daytime construction, vegetation removal, grading, and other ground-disturbing activities), the Project could directly impact special-status nesting birds and bats. Mitigation Measures BIO-1 and BIO-2 would reduce this potentially significant impact to a less than significant level.

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Draft Initial Study/Mitigated Negative Declaration July 2025 Mitigation Measure BIO-1: To avoid potential impacts on nesting birds, the following protection measures shall be implemented:
 Preconstruction nesting bird surveys shall be completed from February 1- August

31. A survey shall be completed within 7 days before the beginning of Projectrelated activities. The survey area shall include the Project site and an appropriate buffer around the site to identify any nesting that could be impacted directly or indirectly by the Project-related activities. The survey shall follow established nesting search protocols described in Martin and Geupel (1993) and CDFW and USFWS protocols, where appropriate. If the qualified biologist finds no active nests or breeding activity indicating nests are present, then work can proceed without restrictions. If there is a lapse in Project-related activities for 7 days or more, then a follow-up survey may be required per the recommendations of the qualified biologist.
 If active nests are identified during the survey and the nests are within the Project site or the buffer area and nesting would be adversely affected, a “No Work Zone” buffer area shall be demarcated around each nest site by the qualified biologist. Buffer distances for each bird nest shall be site-specific and established to protect the bird’s normal behavior to prevent nesting failure or abandonment.

The buffer distance shall vary by species, nest location, existing visual and topographical buffers, and intensity and extent of the construction-related disturbance. The buffer area may be as small as 25-50 feet for common, disturbance-adapted species or much larger (e.g., 100-250 feet) for sensitive species like raptors and owls. The “No Work Zone” shall be established in the field with flagging, fencing, or other appropriate material and shall remain in place until all young in the nest have fledged or the nest otherwise becomes inactive due to predation or other natural causes as determined by the qualified biologist. The qualified biologist shall continue to monitor the behavior of the birds at the nest site during construction activities to ensure that they are not disturbed by the project work. Nest monitoring shall continue until the nesting attempt is complete. If state and/or federally-listed birds are found breeding within the area, consultation with the CDFW and USFWS may be required.  If initial ground-disturbing activities occur outside of the nesting season (September 1 through January 31), then a preconstruction survey would not be required, and construction could begin unimpeded.

Mitigation Measure BIO-2: To avoid potential impacts on roosting bats, the following protection measures shall be implemented:
 Before tree removal/trimming (branches over 12” Diameter at Breast Height [DBH]), a qualified biologist shall survey for potential bat roosts and occupied habitats. If active bat roosts are identified within the trees to be removed, the disturbance shall not be allowed until the roost is abandoned or unoccupied.  If tree trimming/removal is postponed or interrupted for more than two weeks from the date of the initial bat survey, the biologist shall repeat the preconstruction survey.  Tree removal or trimming is recommended from September 1 to October 15 or March 1 to April 15 to avoid the bat maternity roost and winter hibernation season.

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Draft Initial Study/Mitigated Negative Declaration July 2025  To the extent feasible, tree work should be avoided between April 15 and September 1 during the maternity roost season [bats are especially vulnerable during this period when females are nursing pups, and the pups are non-volant (not capable of true flight)].
b) No Impact. The Project site does not contain riparian habitat and thus would have no impact on any riparian habitat (Appendix D). Therefore, the Project would result in no impact.
c) No Impact. The Project site does not contain any wetlands or other natural aquatic habitat features, such as stream channels or drainages. No evidence of hydrophytic vegetation, hydric soils, and stream or wetland hydrology was observed during biological surveys of the site (Appendix D). All the plant communities present onsite are dominated by upland grasses, forbs, and woody vegetation. Thus, the Project would not impact any federal protected wetlands. Therefore, the Project would result in no impact.
d) No Impact. There is no habitat for candidate, sensitive, or special-status species of fish. The Project site does not contain any wetlands or other natural aquatic habitat.

The Project would not interfere with the movement of migratory wildlife species or use of nursery site. Therefore, the Project would result in no impact. e) Less than Significant Impact with Mitigation. The Project would require the removal of several native coast live oak trees along Pascale Place and/or near the proposed access road. Along Pascale Place, there are two smaller oaks, 3- and 4-inch DBH on the lower slope, and a cluster of three trees on the upper slope measuring 15- , 17-, and 20-inch DBH. Near the proposed access road at the southwest corner, there is a multi-trunk coast live oak tree that would need to be removed along with some trimming of larger branches of nearby trees. The remaining trees onsite would be protected.

The trees proposed for removal are considered protective native trees by the City of Napa and would require tree replacement mitigation in accordance with City policies.

Mitigation Measures BIO-3 would reduce this potentially significant impact associated with a potential conflict with local tree preservation policies to a less than significant level.

Mitigation Measure BIO-3: To avoid the potential impact associated with a potential conflict with City tree preservation policies, the following shall be implemented:
 Prior to tree removal, the DBH of protected trees proposed for removal shall be confirmed and documented. For every 6 inches of DBH or fraction thereof removed, two trees of the same species shall be planted on or offsite within the City. Tree planting shall be completed by the City within one year of tree removal in a location to be determined and at the City’s discretion.

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Draft Initial Study/Mitigated Negative Declaration July 2025 f) Less than Significant Impact. There are no habitat conservation plans or natural community conservation plans in effect that apply to the Project area, therefore, the Project would not conflict with any habitat conservation plans, natural community conservation plan, or other approved local, regional, or state habitat conservation plan. Therefore, the Project would result in a less-than-significant impact.

References
Swift Biological Consulting, LLC, 2025. Biological Resources Assessment for the Hidden Glen Remediation Project, City of Napa. April 2025.
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Draft Initial Study/Mitigated Negative Declaration July 2025

CULTURAL RESOURCES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

5. CULTURAL RESOURCES — Would the proposed
project:

a) Cause a substantial adverse change in the significance of a historical resource pursuant to in §15064.5? ☐ ☐ ☐ ☒ b) Cause a substantial adverse change in the significance of an archaeological resource pursuant to §15064.5? ☐ ☒ ☐ ☐ c) Disturb any human remains, including those interred
outside of formal cemeteries? ☐ ☒ ☐ ☐
Introduction
This section is based on a Cultural Resources Investigation conducted by Natural Investigations Company (NIC) in March 2025. NIC completed a cultural and paleontological resources investigation of the Project site. The investigation included a records search with the Northwestern Information Center (NWIC) of the California Historical Resources Information System (CHRIS), Sacred Lands File (SLF) search with the Native American Heritage Commission (NAHC), a paleontological records search from the University of California Museum of Paleontology (UCMP), additional archival research focused on historical mapping and land transfer records, and field survey on March 3, 2025. The Cultural Resources Investigation is on file with the City and is confidential due to the potential for releasing potentially sensitive cultural information.

The records search results indicated that no cultural resources have been previously recorded within the Project site. However, four previous surveys were conducted within .25-mile of the site. None of these surveys identified any cultural or ethnographic resources (NIC, 2025). The SLF search identified sacred sites associated with the Mishewal-Wappo Tribe of Alexander. NIC submitted consultation letters to the Guidiville Rancheria of California, Mishewal-Wappo Tribe of Alexander Valley, Pinoleville Pomo Nation, and the Yocha Dehe Wintun Nation. No Tribal concerns were identified (NIC, 2025). UCMP records indicate that 143 fossils are known within Napa County. Most of the reported specimens are invertebrates and were found in contexts related to the Chico, Tehama, Knoxville, Markley, and Paskenta formations, which do not occur in the Project area (NIC, 2025).

No new precontact sites, historic sites, features, cultural materials, or ethnographic sites were observed or recorded during the pedestrian survey (NIC, 2025). No paleontological resources and no unique geologic features or outcrops were identified during the pedestrian survey (NIC, 2025).

Discussion
a) No Impact. Archival research and an intensive field survey did not identify any prehistoric cultural resources within the Project area (NIC, 2025). No buildings or structures appear to have been built within the Project area. Consequently, there is very little chance that any intact and potentially significant historic-era resources pre-dating

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Draft Initial Study/Mitigated Negative Declaration July 2025 the early 20th century could be present within the Project area. The survey noted that the Project would not significantly impact any resource that would qualify for listing as eligible on the California Register of Historic Resources (CRHR). Therefore, the Project would result in no impact.
b,c) Less-than-Significant Impact with Mitigation. Archival research and an intensive field survey did not identify any significant archaeological or cultural resources within the Project area (NIC, 2025). The survey noted that due to the burning of waste products, earth moving, introduction of outside soils, use of heavy machinery, and contamination of the Project area, the likelihood of finding buried cultural resources, archaeological resources, or human remains is low. However, there always exists a potential to encounter previously unreported subsurface archaeological resources (including human remains). In the unlikely event that cultural resources, archaeological resources, or human remains are inadvertently discovered, Mitigation Measures CUL-1 through CUL-2 would reduce this potentially significant impact to a less than significant level.

Mitigation Measure CUL-1: In the event that cultural resources are discovered, regardless of significance, all work shall be halted within a 50-foot radius of the discovery and a qualified archaeologist shall be immediately notified. Any soil or cultural or tribal cultural resources that have been removed shall be retained in as close to the original context as possible until reviewed by a qualified archaeologist and applicable tribal representative. Work shall continue outside of the 50-foot buffer around the discovery. If the find is deemed not significant by the qualified archaeologist and applicable tribal representative, work shall resume within the 50- foot buffer. If the find is deemed significant by the qualified archaeologist, additional work, such as shovel testing or data recovery, shall be required and shall be determined through consultation with the City, State Historic Preservation Office, regulatory agencies, affiliated Tribal governments, or other stakeholders, as appropriate.

Mitigation Measure CUL-2: In the event of discovery or recognition of any human remains, the stipulations of State of California Health and Safety Code Section 7050.5 shall be followed to treat the discovery. The Napa County Coroner shall be notified immediately of the discovery of human remains and no further disturbance shall occur in the area of the discovery until the Napa County Coroner has made a determination of origin and disposition of the remains pursuant to PRC Section 5097.98. If the human remains are determined to be of Native American origin, the Coroner shall notify the NAHC, who will determine and notify a Most Likely Descendent (MLD). Treatment of the remains should be determined in consultation with the MLD and appropriate regulatory agencies.

References
Natural Investigations Company (NIC), 2025. Cultural Resources Investigation for the Napa Hidden Glen Dump Remediation, Napa County. March 2025.
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Draft Initial Study/Mitigated Negative Declaration July 2025 ENERGY
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

6. ENERGY — Would the proposed project:
a) Result in potentially significant environmental impact due to wasteful, inefficient, or unnecessary
consumption of energy resources, during project
construction or operation?
☐ ☐ ☒ ☐
b) Conflict with or obstruct a state or local plan for
renewable energy or energy efficiency? ☐ ☐ ☐ ☒
Introduction
Energy resources required for the Project would include diesel and gasoline. These energy resources would be required for offroad equipment, haul trucks, and vehicles supporting the Project.

Setting
The following presents setting information applicable to the Project. Since no buildings would be constructed with the Project, the California Building Energy Efficiency Standards (Title 24, Part 6) and California Green Building Standards Code (Title 24, Part 11) are not discussed.

Petroleum Fuels
The Project would consume petroleum-based fuels during construction for onsite heavy equipment and vehicles (worker automobiles and haul trucks). In 2023, at fueling stations within the state, California gasoline sales were approximately 11,685 million gallons, diesel fuel sales were approximately 2,016 million gallons, and natural gas sales were approximately 85.65 million gallons (CEC, 2024).

Discussion
a) Less-than-Significant Impact. The Project would consume energy resources during construction activities. Construction activities are a temporary and one-time direct source of energy consumption. Construction activities would consume petroleum fuels (primarily diesel and gasoline) through the operation of heavy off-road equipment, haul trucks, and worker automobiles.

Based on California Air Pollution Officers Association (CAPCOA) CalEEMod (California Emissions Estimator Model Version 2022.1) results (Appendix C) for Project construction and standard fuel consumption conversion factors, construction would require approximately 13,888 gallons of diesel and 516 gallons of gasoline. The CalEEMod model inputs are provided in Appendix C along with the detailed emissions results. The CalEEMod modeling assumed a three-month construction period, with three to five pieces of heavy construction equipment operating onsite each day depending on

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Draft Initial Study/Mitigated Negative Declaration July 2025 the given phase, heavy trucks exporting waste-impacted soil and importing clean fill, and worker automobiles traveling to and from the site each day.

Construction of the Project would occur intermittently over approximately two to three months. Project construction would utilize fuel efficient equipment and trucks consistent with state regulations and would be consistent with state regulations intended to reduce the inefficient, wasteful, or unnecessary consumption of energy, such as anti-idling and emissions regulations. Furthermore, construction contractors are economically incentivized to employ energy efficient techniques and practices to reduce fuel use to lower overall construction costs.

In light of these statutory and regulatory requirements, the consumption of energy resources during Project construction would not result in a wasteful, inefficient, or unnecessary consumption of energy resources. Therefore, Project construction would result in a less-than-significant impact.
b) No Impact. The Project would not conflict with or obstruct a state or local plan for renewable energy or energy efficiency. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, there are no renewable energy or energy efficiency plans applicable to the Project. Therefore, the Project would result in no impact.

References
California Energy Commission, Final 2019 Integrated Energy Policy Report, November 08, 2019, https://www.energy.ca.gov/publications/2019/2019-integrated-energy-policy-report California Energy Commission, California Retail Fuel Outlet Annual Reporting Results, 2024, https://www.energy.ca.gov/data-reports/energy-almanac/transportation-energy/californiaretail-fuel-outlet-annual-reporting California Air Resources Board, Final 2022 Scoping Plan Update, November 16, 2022, https://ww2.arb.ca.gov/our-work/programs/ab-32-climate-change-scopingplan#:~:text=The%20Draft%202022%20Scoping%20Plan,neutrality%20no%20later%20than% 202045
U.S. Energy Information Administration, Carbon Dioxide Emissions Coefficients, September 18, 2024, https://www.eia.gov/environment/emissions/co2_vol_mass.php _________________________

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GEOLOGY AND SOILS
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

7. GEOLOGY AND SOILS — Would the proposed
project:

a) Directly or indirectly cause potential substantial
adverse effects, including the risk of loss, injury, or death involving:

i) Rupture of a known earthquake fault, as
delineated on the most recent Alquist-Priolo
Earthquake Fault Zoning Map issued by the State
Geologist for the area or based on other
substantial evidence of a known fault? (Refer to
Division of Mines and Geology Special
Publication 42.)
☐ ☐ ☐ ☒
ii) Strong seismic ground shaking? ☐ ☐ ☒ ☐
iii) Seismic-related ground failure, including
liquefaction? ☐ ☐ ☒ ☐
iv) Landslides? ☐ ☐ ☒ ☐
b) Result in substantial soil erosion or the loss of
topsoil? ☐ ☐ ☒ ☐
c) Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the
project, and potentially result in on- or off-site
landslide, lateral spreading, subsidence, liquefaction, or collapse?
☐ ☐ ☒ ☐
d) Be located on expansive soil, as defined in
Table 18-1-B of the Uniform Building Code (1994),
creating substantial direct or indirect risks to life or property?
☐ ☐ ☒ ☐
e) Have soils incapable of adequately supporting the use of septic tanks or alternative wastewater disposal
systems where sewers are not available for the
disposal of wastewater?
☐ ☐ ☐ ☒
f) Directly or indirectly destroy a unique paleontological resource or site or unique geologic feature? ☐ ☐ ☒ ☐
Introduction
Geologic Setting
The eastern side of the city of Napa and the Project site are underlain by Pliocene age5 Sonoma Volcanics. The Sonoma Volcanics are a complex collection of rocks originating from volcanic activity. The composition of these rocks is highly variable and represents an accumulation of material erupted from numerous volcanic source vents. These types of volcanic rocks, namely 5 The Pliocene Epoch spanned from about 11 to 3 million years ago.

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Draft Initial Study/Mitigated Negative Declaration July 2025 rhyolite 6, ashflow tuff 7, and breccia8 were observed at the surface of the Project site or during exploration drilling. The original quarry was excavated through these volcanic rocks to a depth of about 80 feet and then over its years as a municipal dump, it was backfilled with waste materials.

These waste materials are currently covered under an engineered cap consisting of topsoils, a geo-composite drainage net, and polyethylene membrane and foundation fills. The buffer areas surrounding the capped portion contain soil-waste mixtures up to 20-inches thick (Ninyo and Moore, 2024).

The depth of groundwater beneath the Project site appears variable due to the presence of complex native bedrock and the soil-waste materials beneath the cap. Groundwater flow through bedrock has a low hydraulic conductivity 9
because it is controlled by a combination of the dense
bedrock matrix, non-interconnected fractures, and/or by the variability of contact zones between different volcanic units (Ninyo and Moore, 2024). Reportedly, the quarry was abandoned due to the presence of groundwater at a depth of about 80 feet below ground surface, which suggests a deeper, and possibly more connected, water bearing zone. However, groundwater was encountered in the three existing landfill gas (LFG) wells (MW-1, 2, and 3; see section 9, Hazards and Hazardous Materials) at depths ranging between 8 and 22 feet. The variability of groundwater levels measured in these wells suggests the intrusion of locally present subsurface water into the screened intervals of the wells, rather than the presence of a stable, shallow groundwater table in a continuous water bearing zone.

Napa County is within the seismically active San Francisco Bay Area and will therefore experience the effects of future earthquakes.10 There are numerous active faults in the San Francisco Bay area region and many earthquakes have occurred here throughout history. The Project site is situated between the active West Napa Fault Zone, located about 2.5 miles to the west and the active Green Valley fault located 5 miles to east (CGS, 2023a). The West Napa fault was the source for the magnitude 6.0 South Napa earthquake that occurred in Napa County on August 24, 2014 and the magnitude 5.2 Yountville earthquake, which occurred on September 3, 2000.

The intensity of earthquake ground shaking will be dependent on several factors including distance from the site to the earthquake epicenter, depth of the earthquake, earthquake magnitude, and the response of the underlying soils. The city of Napa could experience strong to violent ground shaking in the event of a local or regional earthquake from any one of the active faults in northern California. The Project site is underlain by native bedrock but also about 80 feet of waste material under the capped portion of the former landfill. Bedrock attenuates groundshaking 6 Rhyolite is a pale fine-grained volcanic rock of granitic composition, 7 Tuff is a type of igneous rock formed from consolidated or welded deposits of volcanic ash, tephra, and other volcanic debris, typically resulting from explosive volcanic eruptions.
8 Breccia is a clastic sedimentary rock composed of angular, broken fragments of rocks or minerals cemented together by a finegrained matrix. 9 Hydraulic conductivity is a measure of the capacity of a soil or rock to transmit water. 10 The 2014 Working Group on California Earthquake Probabilities concluded from its updated 30-year earthquake forecast for California that there is a 72-percent probability of at least one earthquake of magnitude 6.7 or greater occurring somewhere in the San Francisco Bay region before 2043 (USGS, 2016).

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Draft Initial Study/Mitigated Negative Declaration July 2025 but the presence of waste materials could amplify seismic waves, increasing ground shaking on the Project site.

The Project site is not within an area zoned under California’s Seismic Hazards Mapping Act (SHMA), which identifies areas susceptible to strong ground shaking, liquefaction, landslides, and other ground failures caused by seismic events. As the closest active fault is over 2 miles away, the Project site is not within an earthquake faults zone delineated under the Alquist-Priolo Earthquake Fault Zoning Act (CGS, 2023a).

Discussion
ai) No Impact. The Project site is not located within an Alquist-Priolo Earthquake Fault Zone and is approximately 2.5 miles from the nearest fault (the West Napa fault) capable of causing surface rupture (CGS, 2023a). There are no mapped traces of older faults extending through the Project site (CGS, 2023b). Therefore, there is no potential for the Project site to experience surface fault rupture from a known mapped earthquake fault.

Therefore, the Project would result in no impact.
aii) Less-than-Significant Impact. Major factors that affect the severity (intensity) of ground shaking include the size (magnitude) of the earthquake, the distance to the fault that generated the earthquake, and the underlying geologic materials. Seismic ground shaking from regional fault zones, including those along the Green Valley, Concord, or Clayton faults, as well as other major faults in the San Francisco Bay Area (namely, the San Andreas fault and the Hayward-Rodgers Creek fault) could affect the Project site.

The Project involves excavating waste-impacted soil and reconsolidating elsewhere on the parcel or hauling it offsite. No structures are proposed. Final grading and site restoration would improve soils stability through reconsolidation of fills, contouring, and vegetation. Compared to current site conditions, the proposed remedial actions would not increase the potential for, or exacerbate, the ground shaking hazards during a moderate or major earthquake at the Project site. Therefore, the Project would result in a less-thansignificant impact. aiii) Less-than-Significant Impact. Liquefaction occurs when saturated sandy or gravelly materials become liquified due to earthquake ground shaking. Liquefaction causes a material to lose bearing strength and can result in differential settlement and consolidation, which, in turn, can damage structures and utilities. Lateral spreading occurs when liquified soil materials move downslope during an earthquake. Under current conditions, the Project site is underlain by bedrock under a shallow cover of soilwaste mixtures (buffer areas and adjacent properties) and a zone beneath an engineered cap consisting of heterogenous fill and landfill waste materials. The engineered cap materials are not prone to liquefaction. Subsurface water underlying the Project site appears variable and is not representative of a shallow groundwater table. However, a water bearing zone within the bedrock that may constitute a deep-water table is present approximately 80 feet beneath the site. Given the heterogeneous nature of the soil-waste mixtures beneath the cap and the apparent lack of a shallow groundwater bearing zone, the potential for these materials to liquefy during an earthquake is low. The Project would

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Draft Initial Study/Mitigated Negative Declaration July 2025 relocate waste-impacted soils, reconsolidate them on the existing cap, and cover them with imported clean fills or haul them offsite. As required in the RAP, clean imported fills would be required to meet acceptability criteria as determined by a professional geotechnical engineer who would ensure that they do not have characteristics of liquefiable soils. This would be verified through soil sampling and analysis as noted in the RAP (Appendix B). Site restoration includes recontouring for positive drainage and a vegetative surface, which would avoid ponding water, localized infiltration, and soil saturation. The potential for liquefaction and lateral spreading under existing site conditions is low and the proposed remedial actions would not increase that potential.

Therefore, the Project would result in a less-than-significant impact. aiv) Less than significant. The current topography of the Project site is characterized by low relief and a gradual slope, resulting in a low potential for landslides under static or pseudo-static 11 conditions. Remedial actions proposed on the Project site are not expected to increase this potential. The excavation of waste-impacted soil from the buffer areas would remove waste mixtures down to bedrock in most locations and backfill with imported fill. These fills would be placed at gradual slopes to minimize areas with locally over-steepened fill slopes. The reconsolidation of waste-impacted soil on the existing cap would be graded and covered to match existing contours without creating an over steepened slope (See Figure 4 – Grading Plan and Figure 5 – Grading Sections). As shown on Figure 4 and Figure 5, the steeper slopes are placed against the near vertical walls of the old quarry on the north and east side of the Project site where surrounding residential properties are at a higher elevation and not susceptible to landslides.

Furthermore, final site restoration and grading to achieve positive drainage and vegetation (native grasses) on the final cover would minimize ponding and soil saturation that could lead weak soil susceptible to movement. The Project would not increase the potential for landsliding compared to existing conditions because the placement, reconsolidation, compaction, and grading would be overseen by licensed geologists, engineers, and/or landscape architects and the construction plans would be reviewed and stamped by such individuals prior commencement of the Project. Considering the overall gradual slope of the Project site and the proposed fill placement and grading plan, the Project would not increase the potential for landsliding compared to existing conditions.

Therefore, the Project would result in a less-than-significant impact. b) Less-than-Significant Impact. Short-term erosion of surface soils or temporary soil stockpiles is possible during the excavation phase of the Project when soils are disturbed and exposed to precipitation. However, under the Construction General Permit (CGP) (discussed in further detail in the Hydrology and Water Quality section), the permit applicant or their contractor(s) would implement stormwater controls [(aka Best Management Practices (BMPs)], as set forth in a detailed Stormwater Pollution Prevention Plan (SWPPP). SWPPPs must describe the specific erosion control and stormwater quality BMPs needed to reduce erosion and minimize pollutants in stormwater runoff with adequate details of their placement and proper installation. Under 11 Static refers to non-earthquake conditions and pseudo-static refers to applied forces during an earthquake.

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Draft Initial Study/Mitigated Negative Declaration July 2025 the CGP, there is a low potential that the Project site would be impacted by a substantial degree of erosion during construction. Additionally, consistent with CGP SWPPP requirements, an Erosion Control Plan (See Appendix B of the RAP [Appendix B of this Initial Study) has been prepared for the Project that details BMPs to be implemented as part of the Project, including protecting temporary stockpiles from erosion and stormwater run-on and runoff, erosion control type and placement, stormwater drainage control, secondary containment, fugitive emission control of dust, and spill prevention.

After the Project is complete and the site is restored, positive drainage to minimize ponding and planted vegetation to stabilize the surface soils would substantially reduce the potential for concentrated runoff to erode the landfill cap or remove topsoil.

Additionally, the Project’s stormwater entering the City’s municipal stormwater system would be subject to compliance with the City’s MS4 General Permit. Adherence to the requirements of the MS4 General Permit, in combination with Project design features (such as site grading, clean soil cover, rehabilitated drainage structures, riprap placement in swales, soil revegetation, and pollutant source controls) would ensure erosion, siltation, and polluted runoff are avoided and/or minimized as compared to existing conditions. Considering the short-term runoff controls employed during construction and the final site grading and site restoration, the potential for excessive erosion is low.

Therefore, the Project would result in a less-than-significant impact. c) Less-than-Significant Impact. The Project site is a capped landfill containing about 80 feet of waste material and surrounded by shallow bedrock. Under current conditions, the landfill material and the engineered cap overlying the landfill is stable. The Project would remove waste-impacted soil from the edges of the landfill and adjacent properties and place them on the existing cap. These waste-impacted soils would then be spread, reconsolidated and covered with clean imported fill. The final site restoration would grade and vegetate the landfill area to achieve positive drainage and slope stability. The placement and reconsolidation of waste-impacted soil and importation, placement, and compaction of clean fills would be completed under the direction and recommendations of California registered geologists and engineers who would ensure the final competency and stability of soils placed during the remediation operation. As explained previously, the remedial actions proposed by the Project would not cause landsliding (see Impact aiv discussion) or liquefaction and lateral spreading (see Impact aiii discussion).

Subsidence can occur when underground cavities cause the surface soils to subside or when groundwater is extracted causing a depression response at the surface; these conditions do not exist at the Project site. Soil collapse can occur when the soil is weak or unsupported. The importation, placement, and reconsolidation of the fill soils would be monitored onsite during remediation activities by California certified engineers and geologists consistent with recommendations of the project geotechnical engineer and thus, the potential for conditions promoting soil collapse would be low. As explained previously, the Project site is currently stable (see Impact aiii and aiv discussions), and the proposed remedial actions would not reduce the stability of the landfill cap, buffer

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Draft Initial Study/Mitigated Negative Declaration July 2025 areas or adjacent properties. Therefore, the Project would result in a less-than-significant impact.
d) Less-than-Significant Impact. The Project would excavate waste-impacted soil from the buffer area and adjacent properties, relocate them onto the landfill cap, and then reconsolidate and cover them with clean imported fill or haul them offsite. Replacing waste-impacted soil with clean imported fill would substantially reduce the potential for soils with expansive characteristics to be exposed as final cover, because the placement, reconsolidation, compaction, and grading would be overseen by licensed geologists, engineers, and/or landscape architects and clean imported fill characteristics would be verified through soil sampling and analysis as noted in the RAP (Appendix B). All imported fill soils placed over the reconsolidated waste material would meet acceptability criteria as prescribed by a certified geotechnical engineer, and soils with high expansivity potential could require conditioning prior to placement, if deemed necessary. Expansive soils typically cause most damage to structural foundations and because there are no structures proposed as part of the Project, there is a low potential that expansive soils would create substantial direct or indirect risks to life or property. Therefore, the Project would result in a less-than-significant impact.
e) No Impact. An Onsite Wastewater Treatment System (OWTS) does not currently exist on the site and the Project does not propose installing an OWTS. Therefore, the Project would result in no impact.
f) Less-than-Significant Impact. The Project site is underlain by Pliocene-age Sonoma Volcanics and soil-waste mixtures. The lavas of the Sonoma Volcanics are not paleontologically sensitive, but the sedimentary strata within this formation are highly sensitive due to recorded plant and animal fossils (PaleoResource Consultants, 2015).

The soil overlying the buffer areas and adjacent properties are heterogeneous mixtures of reworked topsoil and waste and are not considered paleontologically sensitive due to their young age and disturbed condition. Proposed excavations to remove and relocate the soilwaste mixtures would extend to the surface of the Sonoma Volcanics (a maximum depth of 20 inches) but would not excavate into the bedrock. However, additional shallow excavation into the bedrock may be necessary for the construction of the proposed access road from Pascale Place. These excavations would contact rhyolite, tuff, and breccias, which are not considered paleontologically sensitive strata of the Sonoma Volcanics. The proposed excavation would not disturb paleontologically sensitive geologic materials, so the potential of encountering fossil remains is low. Therefore, the Project would result in a less-than-significant impact.

References
California Geological Survey (CGS), 2023a. EQZapp – California Earthquake Hazard Zone Application https://maps.conservation.ca.gov/cgs/EQZApp/app/ Accessed March-April 2025.

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Draft Initial Study/Mitigated Negative Declaration July 2025 California Geological Survey (CGS) 2023b. Fault Activity Map of California. ArcGIS Web Application. https://maps.conservation.ca.gov/cgs/fam/app/ Accessed July 2024.

Ninyo and Moore, 2024. Remedial Action Plan, Hidden Glen Dump, Coombsville Road, Napa, California. SWIS No. 28-AA-0028. Prepared for the Napa County Local Enforcement Agency. Ninyo and Moore Project No. 09558001, October 16, 2024.

PaleoResource Consultants and F&F GeoResource Associates, Inc. 2015. “Paleontological Evaluation Report for the Fulton-Fitch Mountain Reconductoring Project in Sonoma County, California.” September 24.

USGS, 2016. Earthquake Outlook for the San Francisco Bay Region 2014-2041. Fact Sheet 2016-3020, Revised August 2016 (version 1.1). Accessible at:
https://pubs.er.usgs.gov/publication/fs20163020 Accessed July, 2023. _________________________

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GREENHOUSE GAS EMISSIONS
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

8. GREENHOUSE GAS EMISSIONS — Would the
proposed project:

a) Generate greenhouse gas emissions, either directly or indirectly, that may have a significant impact on the
environment?
☐ ☐ ☒ ☐
b) Conflict with an applicable plan, policy or regulation adopted for the purpose of reducing the emissions of
greenhouse gases?
☐ ☐ ☒ ☐
Introduction
Greenhouse gas emissions (GHG) emissions would be temporarily generated by onsite equipment, haul trucks, and vehicles required for construction of the Project.

Setting
Global Climate Change and GHG Emissions
Over the last 10,000 years, the rate of temperature change has typically been incremental, with warming and cooling occurring over the course of thousands of years. However, scientists have observed an unprecedented increase in the rate of warming over the past 150 years, roughly coinciding with the global industrial revolution, which has resulted in substantial increases in GHG emissions into the atmosphere. The anticipated impacts of climate change in California range from water shortages to inundation from sea level rise. Transportation systems contribute to climate change primarily through the emissions of certain GHGs (CO2, methane (CH4), and nitrous oxide (N2O)) from nonrenewable energy (primarily gasoline and diesel fuels) used to operate passenger, commercial and transit vehicles. Land use changes contribute to climate change through construction and operational use of electricity and natural gas, and waste production.

The Intergovernmental Panel on Climate Change (IPCC) has reached consensus that humancaused emissions of GHGs in excess of natural ambient concentrations are responsible for intensifying the greenhouse effect and leading to a trend of unnatural warming of the earth’s climate, known as global climate change or global warming. It is “extremely likely” that more than half of the observed increases in global average surface temperature from 1951 to 2010 were caused by the anthropogenic increase in GHG concentrations and other anthropogenic forces together. The IPCC predicts that the global mean surface temperature increase by the end of the 21st century (2081– 2100) relative to 1986–2005, could range from 0.5 to 8.7 degrees Fahrenheit. Additionally, the IPCC projects that global mean sea level rise will continue during the 21st century, very likely at a faster rate than observed from 1971 to 2010. For the period 2081–2100 relative to 1986–2005, the rise will likely range from 10 to 32 inches (IPCC, 2013).

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Draft Initial Study/Mitigated Negative Declaration July 2025 Greenhouse Gases
Gases that trap heat in the atmosphere are referred to as GHGs because they capture heat radiated from the sun as it is reflected back into the atmosphere, much like a greenhouse does. The accumulation of GHGs has been implicated as the driving force for global climate change. The six primary GHGs are:
 carbon dioxide (CO2), emitted when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned;
 methane (CH4), produced through the anaerobic decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, incomplete fossil fuel combustion, and water and wastewater treatment;
 nitrous oxide (N2O), typically generated as a result of soil cultivation practices, particularly the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning;
 hydrofluorocarbons (HFCs), primarily used as refrigerants;  perfluorocarbons (PFCs), originally introduced as alternatives to ozone depleting substances and typically emitted as by-products of industrial and manufacturing processes; and  sulfur hexafluoride (SF6), primarily used in electrical transmission and distribution.

Although there are other contributors to global climate change, these six GHGs are identified by the U.S. EPA as threatening the public health and welfare of current and future generations.

GHGs have varying potential to trap heat in the atmosphere, known as global warming potential (GWP), and atmospheric lifetimes. GWP reflects how long GHGs remain in the atmosphere, on average, and how intensely they absorb energy. Gases with a higher GWP absorb more energy per pound than gases with a lower GWP and thus contribute more to warming Earth. For example, one ton of CH4 has the same contribution to the greenhouse effect as approximately 28 tons of CO2; hence, CH4 has a 100-year GWP of 28 while CO2 has a GWP of 1. GWP ranges from 1 (for CO2) to 23,500 (for SF6).

In emissions inventories, GHG emissions are typically reported in terms metric tons of CO2 equivalents (CO2e). CO2e are calculated as the product of the mass emitted of a given GHG and its specific GWP. While CH4 and N2O have much higher GWP than CO2, CO2 is emitted in such vastly higher quantities that it accounts for the majority of GHG emissions in CO2e.

Regional GHG Emissions Estimates
In 2022, the United States emitted about 6,343 million metric tons of CO2e or 5,489 million metric tons of CO2e after accounting for sequestration from the land sector. Emissions increased in 2022 by 1 percent. The increase in total GHG emissions was driven largely by an increase in CO2 emissions from fossil fuel combustion. This increase in fossil fuel consumption emissions

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Draft Initial Study/Mitigated Negative Declaration July 2025 was due in part to the continued rebound in economic activity after the height of the COVID-19 pandemic (U.S. EPA, 2024).

According to U.S. EPA, net emissions were 17 percent below 2005 levels. The recent decline is mostly due to a shift to less CO2-intensive natural gas for generating electricity and a rapid increase in the use of renewable energy in the electric power sector. Transportation activities accounted for 28 percent of total GHGs emissions in 2022. Emissions from electric power accounted for the second largest portion (25 percent), while emissions from industry accounted for the third largest portion (23 percent) of total GHG in 2022 (U.S. EPA, 2024).

In 2022, California emitted approximately 371 million metric tons of CO2e, 9.3 million metric tons of CO2e lower than 2021 levels and 60 million metric tons of CO2e below the 2020 GHG limit of 431 million metric tons of CO2e. The transportation sector represents 39 percent of the total GHG emissions. The industrial sector represents 23 percent of the total GHG emissions, followed by electricity (11 percent), and residential, agricultural, and commercial (8, 8, and 6 percent, respectively) (CARB, 2024).

Executive Order S-3-05
Governor Schwarzenegger established Executive Order S-3-05 in 2005, in recognition of California’s vulnerability to the effects of climate change. Executive Order S-3-05 set forth a series of target dates by which statewide emissions of GHG would be progressively reduced, as follows:
 By 2010, reduce GHG emissions to 2000 levels;
 By 2020, reduce GHG emissions to 1990 levels; and
 By 2050, reduce GHG emissions to 80 percent below 1990 levels.

The executive order directed the Secretary of CalEPA to coordinate a multi-agency effort to reduce GHG emissions to the target levels. The Secretary will also submit biannual reports to the governor and California Legislature describing the progress made toward the emissions targets, the impacts of global climate change on California’s resources, and mitigation and adaptation plans to combat these impacts. To comply with the executive order, the secretary of CalEPA created the California Climate Action Team, made up of members from various state agencies and commissions. The report proposed to achieve the targets by building on the voluntary actions of California businesses, local governments, and communities and through state incentive and regulatory programs.

Assembly Bill 32 (California Global Warming Solutions Act of 2006) California passed the California Global Warming Solutions Act of 2006 (AB 32; California Health and Safety Code Division 25.5, Sections 38500 - 38599). AB 32 established regulatory, reporting, and market mechanisms to achieve quantifiable reductions in GHG emissions and establishes a cap on statewide GHG emissions. AB 32 required that statewide GHG emissions be reduced to 1990 levels by 2020. This reduction was to be accomplished by enforcing a statewide

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Draft Initial Study/Mitigated Negative Declaration July 2025 cap on GHG emissions that were to be phased in starting in 2012. To effectively implement the cap, AB 32 directed CARB to develop and implement regulations to reduce statewide GHG emissions from stationary sources. AB 32 specified that regulations adopted in response to AB 1493 were used to address GHG emissions from vehicles. However, AB 32 also included language stating that if the AB 1493 regulations cannot be implemented, then CARB was to develop new regulations to control vehicle GHG emissions under the authorization of AB 32.

AB 32 required CARB to adopt a quantified cap on GHG emissions representing 1990 emissions levels and disclose how it arrived at the cap; institute a schedule to meet the emissions cap; and develop tracking, reporting, and enforcement mechanisms to ensure that the state reduces GHG emissions enough to meet the cap. AB 32 also includes guidance on instituting emissions reductions in an economically efficient manner, along with conditions to ensure that businesses and consumers are not unfairly affected by the reductions. Pursuant to AB 32, CARB identified 427 million MT CO2e as the total Statewide aggregated 1990 GHG emissions level, which serves as the 2020 emissions limit. Using these criteria to reduce statewide GHG emissions to 1990 levels by 2020 represented an approximate 25 to 30 percent reduction in current emissions levels.

However, CARB also had discretionary authority to seek greater reductions in more significant and growing GHG sectors, such as transportation, as compared to other sectors that are not anticipated to significantly increase emissions. The goals of AB 32 were achieved within the 2002 timeline.

Climate Change Scoping Plan
AB 32 also required CARB to develop a Scoping Plan that describes the approach California will take to reduce GHG to achieve the goal of reducing emissions to 1990 levels by 2020. The Scoping Plan was first approved by CARB in 2008 and must be updated every five years. The initial AB 32 Scoping Plan contains the main strategies California will use to reduce the GHG that cause climate change. The initial Scoping Plan has a range of GHG reduction actions which include direct regulations, alternative compliance mechanisms, monetary and non-monetary incentives, voluntary actions, market-based mechanisms such as a cap-and-trade system, and an AB 32 program implementation fee regulation to fund the program. In August 2011, the initial Scoping Plan was approved by CARB.

In 2022, CARB approved the Third Update to the Climate Change Scoping Plan (2022 Scoping Plan), which lays out a path to achieve targets for carbon neutrality and reduce anthropogenic GHG emissions by 85 percent below 1990 levels no later than 2045, as directed by Assembly Bill 1279 (CARB, 2022). The 2022 Scoping Plan:
 Identifies a path to keep California on track to meet its SB 32 GHG reduction target of at least 40 percent below 1990 emissions by 2030.
 Identifies a technologically feasible, cost-effective path to achieve carbon neutrality by 2045 and a reduction in anthropogenic emissions by 85 percent below 1990 levels.

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Draft Initial Study/Mitigated Negative Declaration July 2025  Focuses on strategies for reducing California’s dependency on petroleum to provide consumers with clean energy options that address climate change, improve air quality, and support economic growth and clean sector jobs.
 Integrates equity and protecting California’s most impacted communities as driving principles throughout the document.
 Incorporates the contribution of natural and working lands to the state’s GHG emissions, as well as their role in achieving carbon neutrality.
 Relies on the most up-to-date science, including the need to deploy all viable tools to address the existential threat that climate change presents, including carbon capture and sequestration, as well as direct air capture.
 Evaluates the substantial health and economic benefits of taking action.  Identifies key implementation actions to ensure success.

The recommended measures in the 2022 Scoping Plan and previous Scoping Plans are broad policy and regulatory initiatives that will be implemented at the State level and do not relate to the construction and operation of individual projects.

Low Carbon Fuel Standard
Under the Climate Change Scoping Plan, the CARB identified the low carbon fuel standard (LCFS) as one of the nine discrete early action measures to reduce California’s GHG emissions.

The LCFS is designed to decrease the carbon intensity of California's transportation fuel pool and provide an increasing range of low-carbon and renewable alternatives, which reduce petroleum dependency and achieve air quality benefits.

In 2018, the CARB approved amendments to the regulation, which included strengthening and smoothing the carbon intensity benchmarks through 2030 in-line with California's 2030 GHG emission reduction target enacted through SB 32, adding new crediting opportunities to promote zero emission vehicle adoption, alternative jet fuel, carbon capture and sequestration, and advanced technologies to achieve deep decarbonization in the transportation sector.

The LCFS standards are expressed in terms of the "carbon intensity" (CI) of gasoline and diesel fuel and their respective substitutes. The program is based on the principle that each fuel has "life cycle" GHG emissions and the life cycle assessment examines the GHG emissions associated with the production, transportation, and use of a given fuel. The life cycle assessment includes direct emissions associated with producing, transporting, and using the fuels, as well as significant indirect effects on GHG emissions, such as changes in land use for some biofuels. The carbon intensity scores assessed for each fuel are compared to a declining CI benchmark for each year.

Low carbon fuels below the benchmark generate credits, while fuels above the CI benchmark generate deficits. Credits and deficits are denominated in metric tons of GHG emissions. Providers of transportation fuels must demonstrate that the mix of fuels they supply for use in California

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Napa Hidden Glenn Remediation Project 47 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 meets the LCFS carbon intensity standards, or benchmarks, for each annual compliance period. A deficit generator meets its compliance obligation by ensuring that the credits it earns or otherwise acquires from another party is equal to, or greater than, the deficits it has incurred.

Executive Order No. B-30-15
On April 29, 2015, Executive Order No. B-30-15 was issued to establish a California GHG reduction target of 40 percent below 1990 levels by 2030. Executive Order No. B-30-15 sets a new, interim, 2030 reduction goal intended to provide a smooth transition to the existing ultimate 2050 reduction goal set by Executive Order No. S-3-05 (signed by Governor Schwarzenegger in June 2005). It is designed so State agencies do not fall behind the pace of reductions necessary to reach the existing 2050 reduction goal. Executive Order No. B-30-15 orders “All State agencies with jurisdiction over sources of GHG emissions shall implement measures, pursuant to statutory authority, to achieve reductions of GHG emissions to meet the 2030 and 2050 targets.” The Executive Order also states that “CARB shall update the Climate Change Scoping Plan to express the 2030 target in terms of million metric tons of carbon dioxide equivalent.” The CARB is currently moving forward with a second update to the Climate Change Scoping Plan to reflect the 2030 reduction target. The updated Scoping Plan will provide a framework for achieving the 2030 target. In September of 2016, the AB 32 was extended to achieve reductions in GHG of 40 percent below 1990 levels by 2030. The new plan, outlined in SB 32, involves increasing renewable energy use, putting more electric cars on the road, improving energy efficiency, and curbing emissions from key industries.

Executive Order No. B-55-18/Assembly Bill 1279
Executive Order B-55-18 was signed by Governor Brown on September 10, 2018. The order establishes an additional statewide policy to achieve carbon neutrality by 2045 and maintain net negative emissions thereafter. As per Executive Order B-55-18, CARB is directed to work with relevant state agencies to develop a framework for implementation and accounting that tracks progress toward this goal and to ensure future Climate Change Scoping Plans identify and recommend measures to achieve the carbon neutrality goal.

Executive Order B-55-18 establishes a statewide policy for California to achieve carbon neutrality as soon as possible, and no later than 2045, and achieve and maintain net-negative emissions thereafter. The goal is an addition to the existing statewide targets of reducing the State’s GHG emissions. CARB intends to work with relevant State agencies to ensure that future scoping plan updates identify and recommend measures to achieve the carbon neutrality goal. On September 16, 2022, AB 1279, also known as the California Climate Crisis Act, codified the carbon neutrality goal established by EO B-55-18.

Significance Criteria
CEQA Guidelines Section 15064 and Appendix G recommend that a lead agency consider a project’s consistency with relevant, adopted plans, and discuss any inconsistencies with applicable regional plans, including plans to reduce GHG emissions. Consistent with Appendix G of the CEQA Guidelines, GHG emissions generated by the Project could have a cumulatively considerable contribution to global climate change if the Project would:

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 48 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025  Generate GHG emissions, either directly or indirectly, that may have a significant impact on the environment; or
 Conflict with an applicable plan, policy or regulation adopted for the purpose of reducing the emissions of GHG.

CEQA Guidelines Section 15064.4 provides guidance to lead agencies for determining the significance of environmental impacts pertaining to GHG emissions. Section 15064.4(a) states that a lead agency should make a good-faith effort that is based, to the extent possible, on scientific and factual data to describe, calculate, or estimate the amount of GHG emissions that would result from implementation of a project. CEQA Guidelines Section 15064.4(b) also states that, when assessing the significance of impacts from GHG emissions, a lead agency should consider (1) the extent to which the project may increase or reduce GHG emissions compared with existing conditions, (2) whether the project’s GHG emissions would exceed a threshold of significance that the lead agency has determined to be applicable to the project, and (3) the extent to which the project would comply with regulations or requirements adopted to implement a statewide, regional, or local plan for the reduction or mitigation of GHG emissions.

BAAQMD’s thresholds of significance consist of three options for project-level impacts:
a. Land use project design elements that must be included in a project, b. Consistency with a local GHG reduction strategy, or
c. A stationary source threshold of 10,000 metric tons of CO2e per year.

BAAQMD’s CEQA Air Quality Guidelines, Appendix B: CEQA Thresholds for Evaluating the Significance of Climate Impacts from Land Use Projects and Plans, state the following in reference to the newly adopted land use project design elements significance thresholds:
“The Air District has developed these thresholds of significance based on typical residential and commercial land use projects and typical long-term communitywide planning documents such as general plans and similar long-range development plans. As such, these thresholds may not be appropriate for other types of projects that do not fit into the mold of a typical residential or commercial project or general plan update. Lead agencies should keep this point in mind when evaluating other types of projects. A lead agency does not necessarily need to use a threshold of significance if the analysis and justifications that were used to develop the threshold do not reflect the particular circumstances of the project under review. Accordingly, a lead agency should not use these thresholds if it is faced with a unique or unusual project for which the analyses supporting the thresholds as described in this report do not squarely apply. In such cases, the lead agency should develop an alternative approach that would be more appropriate for the particular project before it, considering all of the facts and circumstances of the project on a case-by-case basis.”

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Napa Hidden Glenn Remediation Project 49 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 The Project is not a typical land residential or commercial land use project, as it is a temporary construction activity.

Discussion
a) Less-than-Significant Impact. The Project would generate GHG emissions during construction activities. Construction activities are a temporary and one-time direct source of GHG emissions. Construction activities would generate GHG emissions through the operation of heavy off-road equipment, haul trucks, and worker automobiles.

Construction of the Project would utilize fuel efficient equipment and trucks consistent with state regulations and would be consistent with state regulations intended to reduce the inefficient, wasteful, or unnecessary consumption of energy, such as anti-idling and emissions regulations.

Construction GHG emissions were estimated using CalEEMod (CAPCOA, 2022).

Detailed modeling assumptions and results are provided in Appendix C. The CalEEMod model inputs are provided in Appendix C along with the detailed emissions results. The CalEEMod modeling assumed a three-month construction period, with three to five pieces of heavy construction equipment operating onsite each day depending on the given phase, heavy trucks exporting waste-impacted soil and importing clean fill, and worker automobiles traveling to and from the site each day. Project construction was estimated to generate approximately 146 metric tons of CO2e. This is lower than any commonly used numerical throughout the State for CEQA purposes and is much lower than BAAQMD’s only numerical threshold of 10,000 metric tons of CO2e per year.

BAAQMD has not adopted GHG emissions thresholds of significance for construction.

As noted in BAAQMD’s CEQA Air Quality Guidelines, Appendix B, GHG emissions from construction represent a very small portion of a project’s lifetime GHG emissions and operational emissions represent the vast majority of project GHG emissions. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not generate long-term emissions and the construction emissions would not result in a significant impact on the environment. Therefore, Project construction would result in a less-than-significant impact.
b) Less-than-Significant Impact. As noted in impact a), the Project would be below BAAQMD’s adopted GHG significance thresholds. The Project would not conflict with applicable plans, policies or regulations adopted for the purpose of reducing GHG emissions. Therefore, the Project would result in a less-than-significant impact.

References
Bay Area Air Quality Management District, 2017 Clean Air Plan, April 20, 2017, http://www.baaqmd.gov/~/media/files/planning-and-research/plans/2017-clean-airplan/attachment-a_-proposed-final-cap-vol-1-pdf.pdf?la=en

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 50 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Bay Area Air Quality Management District, California Environmental Quality Act Air Quality Guidelines, April 20, 2023, https://www.baaqmd.gov/plans-and-climate/californiaenvironmental-quality-act-ceqa/updated-ceqa-guidelines California Air Pollution Officers Association, California Emissions Estimator Model User Guide Version 2022.1, April 2022, http://www.caleemod.com/
California Air Resources Board, Emissions Trends Report 2000-2022 (2024 Edition), September 2024, https://ww2.arb.ca.gov/ghg-inventory-data
California Air Resources Board, Final 2022 Scoping Plan Update, November 16, 2022, https://ww2.arb.ca.gov/our-work/programs/ab-32-climate-change-scopingplan#:~:text=The%20Draft%202022%20Scoping%20Plan,neutrality%20no%20later%20than% 202045
International Panel on Climate Change, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, https://www.ipcc.ch/site/assets/uploads/2018/05/SYR_AR5_FINAL_full_wcover.pdf United States Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990 - 2022, April 2024, https://www.epa.gov/ghgemissions/inventory-usgreenhouse-gas-emissions-and-sinks _________________________

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 51 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

HAZARDS AND HAZARDOUS MATERIALS
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

9. HAZARDS AND HAZARDOUS MATERIALS —
Would the proposed project:

a) Create a significant hazard to the public or the
environment through the routine transport, use, or
disposal of hazardous materials?
☐ ☐ ☒ ☐
b) Create a significant hazard to the public or the
environment through reasonably foreseeable upset
and accident conditions involving the release of
hazardous materials into the environment?
☐ ☐ ☒ ☐
c) Emit hazardous emissions or handle hazardous or
acutely hazardous materials, substances, or waste
within one-quarter mile of an existing or proposed
school?
☐ ☐ ☒ ☐
d) Be located on a site which is included on a list of
hazardous materials sites compiled pursuant to
Government Code Section 65962.5 and, as a result,
would it create a significant hazard to the public or
the environment?
☐ ☐ ☒ ☐
e) For a project located within an airport land use plan or, where such a plan has not been adopted, within
two miles of a public airport or public use airport,
would the project result in a safety hazard or
excessive noise for people residing or working in the
project area?
☐ ☐ ☐ ☒
f) Impair implementation of or physically interfere with an adopted emergency response plan or emergency
evacuation plan?
☐ ☐ ☒ ☐
g) Expose people or structures, either directly or
indirectly, to a significant risk of loss, injury or death involving wildland fires?
☐ ☐ ☒ ☐
Introduction
Previous investigation at the Project site encountered waste materials within the closed landfill including old automobiles, general garbage, vegetation material, brush, asphalt, concrete wastes, metal slag, rusted metal, wood fragments, brick or pottery fragments, glass (including melted glass), gravel debris, and small fragments of charcoal (Ninyo and Moore, 2024).

The former dump is now listed as an unpermitted, closed solid waste disposal site in the CalRecycle Solid Waste Information System (SWIS) database (SWIS No. 28-AA-0028) (CalRecycle, 2025). The SWIS database contains up-to-date information pertaining to the Project site including inspections reports, regulatory correspondence, and the current RAP (Appendix B of this Initial Study), which describes the proposed actions under the Project. The County of Napa Environmental Health, Solid Waste Local Enforcement Agency (LEA) inspects the landfill quarterly. The latest inspection was in April 2024 and reported no violations or concerns, except for illegal soil and debris disposal from a neighboring property (Ninyo and Moore, 2024).

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Napa Hidden Glen Remediation Project 52 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 The Project site has three landfill gas (LFG) monitoring wells, identified as MW-1 through MW3. The wells were constructed in December 2020. MW-1 and MW-2 have three screened intake intervals to a depth of 35 feet and MW-3 has two intervals to depth of 20 feet. Methane gas has been monitored on a quarterly basis since December 2020 and will continue to be monitored.

Methane monitoring results have been below regulatory limits during all monitoring events.

Methane is odorless and non-toxic but can present an explosive hazard in high concentrations. It can also act as a simple asphyxiant (displaces oxygen) in low-lying areas or confined spaces and may be an indicator of other potentially hazardous landfill gases.

Elevated lead and total petroleum hydrocarbons (TPH) have been detected in the shallow surface soils within the buffer area surrounding the landfill cap and on adjacent properties. These constituents are contained in shallow (up to 20-inches), heterogeneous soil-waste mixtures. Other constituents of potential concern include landfill gas, metals, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and volatile and semi-volatile organic compounds (VOCs and SVOCs, respectively). PCBs, OCPs, VOCs and SVOCs were found on the Project site in samples from the soil-waste mixtures at concentrations below their respective State Water Resources Control Board (Water Board) Environmental Screening Levels. Laboratory results from the methane gas wells have been below regulatory limits during all monitoring events.

The Project consists of remedial actions intended to reduce the risk of public exposure to metals and other contaminants in the existing buffer areas surrounding the existing landfill cap and from adjacent properties. The LEA would be the lead oversight agency for the Project and would be responsible for overseeing compliance with State and county regulations regarding hazardous materials and other hazards. California Code of Regulations (CCR) Title 27, Division 2 contain the principal State regulations pertaining to waste disposal on land. In California, agencies involved with the regulation and enforcement involving worker exposure to hazards, hazardous materials, and contaminated waste materials include the CalRecycle12, the California Department of Toxic Substance Control (DTSC)13, California Division of Occupational Safety and Health (DOSH or Cal/OSHA)14, and the Water Board)15.

The RAP outlines the grading plans, phasing, and procedures required for the remediation of the onsite soil-waste mixtures. The RAP includes a project-specific worker Site Health and Safety Plan (SHSP) and a Community Health and Safety Plan (CHSP) (Ninyo and Moore, 2024). The SHSP was prepared under the direction of and approved by a certified industrial hygienist (CIH) and covers demolition, excavation, and grading during the onsite remediation activities. In compliance with OSHA requirements, the plan outlines the specific training and monitoring needed to protect workers and identifies potential chemical and physical hazards during field activities. The SHSP covers field procedures, personal protective equipment, expected 12 CalRecycle and local enforcement agencies regulate the operation of solid waste facilities. CalRecycle manages and mitigates impacts of solid waste on public health and safety and the environment by enforcing compliance with regulations under CCR Title 27, Division 2 and State minimum standards through integrated and consistent permitting, inspection, and enforcement efforts. 13 The DTSC regulates toxic substances by overseeing contaminated water and soil cleanup, enforcing hazardous waste laws, reducing hazardous waste generation, and promoting safer, non-hazardous products. 14 CalOSHA is responsible for enforcing worker safety regulations, developing workplace safety standards, and providing public outreach, education and assistance.
15 The SWRCB and the nine Regional Water Quality Control Boards (Regional Water Boards), referred to collectively as the Water Board, have regulatory responsibility to protect surface and groundwater quality under the federal Clean Water Act (CWA) and the State Porter-Cologne Water Quality Control Act.

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Napa Hidden Glenn Remediation Project 53 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 contaminants, exposure action levels, and emergency contingency plans. The SHSP comprehensively addresses potential chemical and explosive hazard exposure associated with unknown types of wastes and contaminant transmission from dust, methane gas, or through waterborne sources during construction actions. Additionally, the SHSP considers and provides guidance regarding physical hazards (e.g. slip and fall, noise, vehicle and heavy equipment operation), waste disposal site excavation hazards (e.g., buried objects, trenching hazards, oxygen deficiency), biological hazards (e.g., spiders, snakes) and radiological hazards. The CHSP is comparable to the SHSP and outlines procedures to ensure public safety and health by minimizing exposure to hazards during site closure activities. It aims to protect the community and surrounding properties from health and environmental risks. The plan covers field procedures, potential contaminants, exposure action levels, hazard monitoring and equipment, site control methods, emergency planning, and emergency contingency plans.

Discussion
a) Less-than-Significant Impact. The Project involves the remediation of waste-impacted soil that contain lead and other contaminants by way of onsite excavation, burial, and capping. The remediation actions would excavate waste-impacted soils and place them over the existing cap under clean imported soils. The operation would be temporary and once completed, the potential for public exposure to lead and other contaminants would be substantially reduced or eliminated. Waste-impacted soil may be temporarily stockpiled but as required by the project RAP, the stockpiles would be covered to avoid dust generation and best management practices (BMPs) would be employed to prevent soil erosion and runoff. BMPs would include fiber roll barriers, silt fences, straw mulch, erosion control blankets, and other controls that are standard practice for ensuring soil erosion and runoff (these are detailed further in the RAP – Appendix B). The remedial actions are proposed to occur within the boundaries of the Project site. Waste-impacted soil that requires offsite disposal would be removed by truck in compliance with state and federal hazardous waste transportation regulations enforced by the DTSC and California State Highway Patrol under supervision of the LEA. The origin, classification, and analysis of imported clean soil for final cover material must be submitted to the LEA for approval before use onsite. Import fill soil sampling methodology and analysis would follow the guidelines published in the DTSC’s 2001 Information Advisory regarding clean imported fill guidelines (DTSC, 2001). Following the completion of operations, the clean imported fill soil covering the disturbed area would be graded for positive drainage and seeded with native grasses.

The Project would temporarily expose soils containing varying concentrations of lead and possibly other chemicals. However, strict controls required in the SHSP (see Appendix B)16, which include hazard monitoring, worker training, personal protective equipment, and oversight by a CIH, would protect workers and reduce their exposure to chemical and physical hazards. The comparable CHSP17 considers potential hazard exposure beyond 16 SHSP is in Appendix D of the RAP which is found in Appendix B of this Initial Study. 17 CHSP is in Appendix E of the RAP which is found in Appendix B of this Initial Study.

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Napa Hidden Glen Remediation Project 54 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 the Project site and provides guidance to reduce public exposure to hazards associated with the remediation activities.

Considering that the Project involves the remediation of waste-impacted soil from areas surrounding the existing capped landfill and adjacent properties, and that comprehensive hazard minimization controls would be employed through the RAP, SHSP and CHSP (see Appendix B), the potential for the Project to create a significant hazard to the public or the environment is low. Therefore, the Project would result in a less-than-significant impact.
b) Less-than-Significant Impact. Remediation activities, as outlined in the RAP, would be completed under strict controls to reduce hazards to site workers and the community. The controls, which are outlined in the SHSP and CHSP and approved by a CIH, comply with state and federal regulations for handling hazardous waste. In addition, the remedial actions would be managed by qualified site supervisors with regulatory oversight by the LEA. Given that the Project is a remediation operation conducted under regulatory oversight with the intended purpose to minimize worker and community exposure to contaminated soils, the potential for the Project to create a significant hazard to the public or the environment involving the release of hazardous materials is low. Therefore, the Project would result in a less-than-significant impact. c) Less than Significant. The closest school to the Project site is the Silverado Middle School, located about one-quarter of a mile to the southeast. The Project involves onsite remediation of soil-waste mixtures containing lead and other contaminants. The onsite construction activities are temporary and there would be strict and comprehensive controls in place to minimize worker and community exposure, as prescribed in the SHSP and CHSP. These controls include air monitoring and soil sampling to ensure vapors and gases emanating from the Project site are managed and contained. Waste-impacted soil that requires offsite disposal would be removed by truck in compliance with state and federal hazardous waste transportation regulations enforced by the DTSC and California State Highway Patrol under supervision of the LEA. Therefore, the potential for the Project to generate hazardous emissions that extend beyond the Project site boundary is very low. Therefore, the Project would result in a less-than-significant impact. d) Less than Significant Impact. The “Cortese List” refers to a collection of databases maintained by select California agencies and Boards that include properties involved in hazardous materials use, hazardous waste, or sites with confirmed soil and groundwater contamination. These databases include the Water Board’s Geotracker data management system, the DTSC’s Envirostor database, and the Water Board’s list of select solid waste disposal sites.18 The Project site is currently included on the Water Board’s Geotracker database (SWRCB, 2025). As discussed above in the setting, it is also included on CalRecycle’s SWIS database. The SWIS database includes the most recent information on the Project site while the Geotracker database indicates that information has not been 18 The Water Board’s list of select solid waste disposal sites are those that contain waste constituents above hazardous waste levels that are outside the waste management unit.

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 55 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 updated since 2016. The Project site is included on the Cortese List, but as described in the items above, it has a very low potential to create a significant hazard to the public or the environment. Therefore, the Project would result in a less-than-significant impact. e) No Impact. The Project site is not located within an Airport Land Use Compatibility Plan and is not within two miles of a public airport. The nearest airport to the Project site is the Napa County Airport located 5.8 miles to the south. Therefore, the Project would result in no impact.
f) Less than Significant. The Project involves temporary remediation activities that would result in waste-impacted soils being relocated and buried onsite or hauled offsite.

Excavation and grading operations would be contained on the Project site and, other than using public streets for occasional equipment onloading/offloading and delivery of imported soil or offsite transport of waste-impacted soil, the Project would not result in reduced public access or require road closures within the adjacent neighborhood streets or on Coombsville Road. In addition, the Project would be conducted under a strict SHSP and CHSP, which provide site worker and community emergency planning and notification procedures. The Project would not impede or require diversion of rescue vehicles or evacuation traffic in the event of a life-threatening emergency. Therefore, the Project would result in a less-than-significant impact. g) Less-than-Significant Impact. The Project site is mapped in a moderate Fire Hazard Severity Zone in a Local Responsibility Area (LRA) (CalFire, 2025). Following the proposed remediation activities, the Project site would be restored as open space. While there are trees on adjacent parcels, the capped former landfill does not contain trees and would be vegetated with native grasses. The Project would not exacerbate regional wildland fire risk. Therefore, the Project would result in a less-than-significant impact.

References
Cal Recycle, 2025. Solid Waste Information System (SWIS), SWIS Facility Site Search tool.

Accessed online March 31, 2025, at
https://www2.calrecycle.ca.gov/SolidWaste/Site/Search
California State Water Resources Control Board (SWRCB), 2024. GeoTracker. Accessed online March 28, 2025, at: https://geotracker.waterboards.ca.gov/ California Department of Forestry and Fire Protection (CalFire), 2025. Fire Hazard Severity Zone Maps, Fire Hazard Severity Zone Viewer Napa County. Accessed online April 1, 2025 at:
https://experience.arcgis.com/experience/6a9cb66bb1824cd98756812af41292a0.

California Department of Toxic Substance Control (DTSC). 2001) Information Advisory – Clean Imported Fill Material. Fact Sheet. California Environmental Protection Agency. October 2001.

Ninyo and Moore, 2024. Remedial Action Plan, Hidden Glen Dump, Coombsville Road, Napa, California. SWIS No. 28-AA-0028. Prepared for the Napa County Local Enforcement Agency. Ninyo and Moore Project No. 09558001, October 16, 2024.

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Napa Hidden Glen Remediation Project 56 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 _______________________

HYDROLOGY AND WATER QUALITY
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

10. HYDROLOGY AND WATER QUALITY – Would the
proposed project:

a) Violate any water quality standards or waste
discharge requirements or otherwise substantially
degrade surface or ground water quality?
☐ ☐ ☒ ☐
b) Substantially decrease groundwater supplies or
interfere substantially with groundwater recharge
such that the project may impede sustainable
groundwater management of the basin?
☐ ☐ ☒ ☐
c) Substantially alter the existing drainage pattern of the site or area, including through the alteration of
the course of a stream or river or through the
addition of impervious surfaces, in a manner which
would:
☐ ☐ ☒ ☐
i) result in substantial erosion of siltation on- or
off- site; ☐ ☐ ☒ ☐
ii) substantially increase the rate or amount of
surface runoff in a manner which would result
in flooding on- or offsite;
☐ ☐ ☒ ☐
iii) create or contribute runoff water which would
exceed the capacity of existing or planned
stormwater drainage systems or provide
substantial additional sources of polluted
runoff; or
☐ ☐ ☒ ☐
iv) impede or redirect flood flows? ☐ ☐ ☒ ☐
d) In flood hazard, tsunami, or seiche zones, risk
release of pollutants due to project inundation? ☐ ☐ ☒ ☐ e) Conflict with or obstruct implementation of a water
quality control plan or sustainable groundwater
management plan?
☐ ☐ ☒ ☐
Introduction
The Project site is in the lower 426-square-mile Napa River watershed. The Napa River, which drains much of the City, extends 55 miles from the Mayacamas Mountains before discharging into San Pablo Bay near the mouth of the Sacramento-San Joaquin estuary. The Project site is approximately 0.7-miles east of the tidally influenced lower portion of the of the Napa River.

Tulucay Creek is located approximately 0.5 miles south of the Project site and Sarco Creek is 2 miles to the north. The Project area receives 24.6 inches of rain annually with the majority occurring from November to March. The Project site is not located within a 100-year or 500-year flood hazard area (FEMA, 2025). Groundwater at the Project site has been documented to occur at depths greater than 8 feet below the ground surface (bgs) (Ninyo and Moore, 2024).

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Napa Hidden Glenn Remediation Project 57 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 There are no surface water features on the Project site. The capped waste disposal area and buffer zone is relatively flat, with surface elevations ranging from approximately 120 to 130 feet mean sea-level (MSL) (Ninyo and Moore, 2024). The northwest, north, and east sides of the Project site are near vertical quarry walls. In general, the surface between the capped waste disposal area and Pascale Place to the west and Glory Court to the south slope downward to approximately 105 feet MSL. Under existing conditions, stormwater runoff that does not infiltrate into the onsite soils flows from the northeastern corner towards a drainage structure comprised of a riprap armored swale and storm drain inlet located on the hillside adjacent to Pascale Place (Ninyo and Moore, 2024). A portion of the Project site’s stormwater also drains southeast toward Lot 5 and into a similar drainage structure in the southeastern corner of the site. Stormwater from the site is conveyed via the onsite drainage structures to the City’s municipal stormwater system.

All stormwater discharged from the Project site is ultimately discharged to the Napa River in accordance with the City’s National Pollutant Discharge Elimination System (NPDES) Phase II Small MS4 General Permit (MS4 General Permit), adopted in 2013 (Water Quality Order 2013- 0001-DWQ). The tidal lower portion of the Napa River is listed on the 2020/2022 303(d) list of impaired waters for nutrients and pathogens (RWQCB, 2025). A Total Maximum Daily Load19 (TMDL) has been approved for pathogens and was adopted in 2007; the Water Quality Control Plan for the San Francisco Bay Basin (Basin Plan) was amended to incorporate the TMDL (RWQCB, 2019).

Discussion
a) Less-than-Significant Impact. Project construction would mainly involve grading for topographic contouring related to the proposed cover and shallow (up to approximately 2- foot bgs) subsurface excavation to remove and reconsolidate waste-impacted soils onsite.

The waste-impacted soil around the perimeter of the landfill cap would be excavated up to a depth of two feet and replaced with clean fill. The waste-impacted soil to be removed would be reconsolidated onsite at the northern portion of the capped dump and covered with a minimum of two feet of clean fill, essentially capping it, or hauled offsite to an appropriate landfill for disposal. Waste-impacted soil would be excavated to bedrock where feasible (to depths of approximately 10 to 20 inches). The depth of excavation would be reduced if bedrock is encountered at shallower depths. Conversely, the depth of excavation may extend beyond 20 inches if wastes are deeper in order to reach bedrock or, alternatively, the excavation may terminate in wastes in which case the wastes would be covered with 2 feet of clean imported soil. Where waste removal may not be possible due to access, stability and/or other restrictions, wastes remaining in place would be covered with two 2 feet of clean imported soil to meet state minimum standards.

Soil/waste from the frontage along Pascale Place would be removed down to bedrock. In addition, one foot of clean imported soil would be placed on top of the existing cap area.

Following the completion of waste removal and backfilling with clean import soil, final grading would be completed to provide positive drainage towards the existing stormwater drainage facilities on site, consistent with existing conditions. The grading and drainage 19 TMDLs are action plans to ensure that beneficial uses are restored and that water quality objectives are achieved by defining how much of a pollutant a water body can tolerate and meet water quality standards.

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Napa Hidden Glen Remediation Project 58 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 plan has been designed such that ponding of stormwater runoff would not occur on site.

Following the completion of grading work, the Project site would be restored as open space and seeded with native grasses to facilitate revegetation and soil stabilization (Appendix B, RAP).

During construction activities, stormwater runoff from disturbed soils is a common source of pollutants (mainly sediment) to receiving waters. Earthwork activities can render soils and sediments more susceptible to erosion from stormwater runoff and result in the migration of soil and sediment in stormwater runoff to storm drains and downgradient water bodies. Further, the onsite soil within the buffer zone proposed for excavation and reconsolidation in the northern part of the Project site is documented as having high lead concentrations. Excessive and improperly managed grading can lead to increased erosion of exposed earth and sedimentation of watercourses during rainy periods. In addition, construction would likely involve the use of various materials typically associated with construction activities such as oil, grease, and petroleum hydrocarbons. If improperly handled, these materials could be transported offsite by stormwater runoff (nonpoint source pollution) and degrade receiving water quality.

The Clean Water Act effectively prohibits discharges of stormwater from construction projects unless the discharge complies with National Pollutant Discharge Elimination System (NPDES) regulations. Because the Project site exceeds one acre in size, construction activities would be required to obtain coverage under the State Construction General Permit (CGP)20. Under the requirements of the CGP, the permit applicant or their contractor(s) would implement stormwater controls, referred to as construction Best Management Practices (BMPs), as set forth in a detailed Stormwater Pollution Prevention Plan (SWPPP). SWPPPs are a required component of the CGP and must be prepared by a California-certified Qualified SWPPP Developer (QSD) and implemented by a California-certified Qualified SWPPP Practitioner (QSP). The SWPPP and BMPs within are a regulatory requirement.

SWPPPs must describe the specific erosion control and stormwater quality BMPs that would be implemented to minimize pollutants in stormwater runoff and detail their placement and proper installation. The BMPs are designed to prevent pollutants from contacting stormwater and to keep all products of erosion (i.e., sediment) and stormwater pollutants from migrating offsite into storm drains and receiving waters. Typical BMPs implemented at construction sites include placement of sediment barriers around storm drains, the use of fiber rolls or gravel barriers to detain sediment from disturbed areas, and temporary or permanent stockpile covers to prevent rainfall from contacting the stockpiled material. In addition to erosion control BMPs, SWPPPs also include BMPs for preventing the discharge of other pollutants such as petroleum products to downstream waters. BMPs for these pollutants also include routine leak inspections of equipment, maintaining labelling and inspecting integrity of containers, and ensuring that 20 NPDES General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities – Order no.

WQ 2022-0057-DWQ which becomes effective on September 1, 2023 and which supersedes Order 2009-0009-DWQ as amended by Order 2010-0014-DWQ and 2012-0006-DWQ.

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Napa Hidden Glenn Remediation Project 59 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 construction materials are disposed of in accordance with manufacture’s recommended disposal practices and applicable hazardous waste regulations. Consistent with CGP SWPPP requirements, an Erosion Control Plan (Callander Associates Landscape Architects, 2024)21 has been prepared for the Project which details BMPs to be implemented as part of the Project, including protecting temporary stockpiles from erosion and stormwater run-on and runoff, erosion control type and placement, stormwater drainage control, secondary containment, fugitive emission control of dust, and spill prevention.

Under the provisions of the CGP, the QSD is responsible for assessing the risk level of a site based on both sediment transport and receiving water risk and developing and implementing the SWPPP. Projects can be characterized as Risk Level 1, 2, or 3, and these risk levels determine the minimum BMPs and monitoring that must be implemented during construction. Under the direction of the QSD, the QSP is required to conduct routine inspections of all BMPs, conduct surface water sampling, when necessary, and report site conditions to the State Water Resources Control Board (SWRCB) using the Stormwater Multi-Application Reporting and Tracking System (SMARTS). Compliance with the CGP is required by law and has proven effective in protecting water quality at construction sites.

Following the completion of construction (post-construction), the Project’s stormwater entering the municipal stormwater conveyance and discharge system would be subject to compliance with the City’s MS4 General Permit, which is administered locally under the Napa Countywide Stormwater Pollution Prevention Program (NCSPPP), a joint effort of Napa’s cities, towns and unincorporated areas22 to comply with State and Federal regulations, preserve beneficial uses of local waterways, prevent stormwater pollution, and protect and enhance water quality in creeks and wetlands (City of Napa Website, Stormwater Quality page, 2025). The City’s MS4 General Permit is designed to protect water quality by controlling stormwater discharges and implementing pollution-reducing practices throughout the City. Specifically, the MS4 General Permit establishes stormwater quality requirements aimed at reducing the discharge of pollutants into the city's stormwater system and, ultimately, local water bodies, such as the Napa River.

These requirements focus on managing the quantity and quality of stormwater runoff to prevent water pollution. Key provisions of the permit include:

Stormwater Management Plans (SWMPs): The City is required to develop and implement SWMPs that outline best management practices (BMPs) to control pollutants in stormwater runoff from both new and existing developments. As noted above, the City’s MS4 General Permit is administered locally by the NCSPPP, and the City requires all future developments to comply with the requirements of the NCSPPP. 21 Erosion Control Plan is in Appendix B of the RAP which is found in Appendix B of this Initial Study. 22 Though the County and each of the five cities and towns carry out their own individual stormwater pollution prevention programs, NCSPPP provides for the coordination and consistency of approaches between the individual participants and documents their efforts in annual reports. NCSPPP is funded by the member agencies and is administered by the Napa County Flood Control and Water Conservation District.

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Napa Hidden Glen Remediation Project 60 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Pollutant Reduction: The permit mandates the reduction of pollutants such as sediment, nutrients, heavy metals, and pathogens, which may be carried by stormwater.

Monitoring and Reporting: The City must monitor stormwater discharges and assess the effectiveness of its stormwater management practices. This includes reporting on water quality improvements and any identified impairments in receiving water bodies.

Best Management Practices (BMPs): The City must implement BMPs for controlling runoff during construction, development, and operation of projects. This includes erosion control, sediment management, and post-construction stormwater treatment to minimize pollution.

Required compliance with the prescriptions set forth by the CGP, including implementation of a SWPPP for construction activities, and the City’s MS4 General Permit, in combination with the Projects design features (such as the drainage structures, riprap armoring of swales, and soil revegetation), pollutant source controls, and implementation of the Project’s Erosion Control Plan would prevent the discharge of pollutants to surface waters or groundwater and minimize or eliminate the potential for degradation of surface water or groundwater quality that could result from implementation of the Project. Further, implementation of the Project would reduce the potential for stormwater to contact onsite legacy wastes and lead contaminated soil, reducing the potential for pollutants and contaminants to be transported offsite by stormwater as compared to existing conditions. Therefore, the Project would result in a less-than-significant impact.
b) Less-Than-Significant Impact. No groundwater wells are proposed as part of the Project and the Project would not involve groundwater extraction. Under the Project, the addition of impervious surfaces is not proposed and there would not be a substantial increase in impervious surfaces such that groundwater recharge is impeded as compared to baseline. Project construction would involve only shallow subsurface excavation and would not intersect groundwater such that construction dewatering is required.

Subsurface water underlying the Project site appears variable and is not representative of a shallow groundwater table. However, a water bearing zone within the bedrock that may constitute a deep-water table is present approximately 80 feet beneath the site. If implemented, the Project would not lower the groundwater table due to groundwater extraction or a reduction in groundwater recharge. Thus, the Project would not interfere with groundwater recharge or substantially decrease groundwater supplies. Therefore, the Project would result in a less-than-significant impact. c) Less-Than-Significant Impact. Implementation of the Project would not involve the direct alteration of a stream or river and would not substantially alter the existing drainage pattern of the Project site or substantially increase impervious surface area as compared to existing conditions. Stormwater runoff during construction and following completion of the Project would not be increased in volume or in regard to peak runoff rates. Stormwater would continue to be collected and conveyed via the existing

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 61 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 stormwater drainage structures adjacent to Pascale Place and in the southeastern corner of the site to the City’s municipal stormwater system, as occurs under existing conditions.

As described under a), above, during construction of the Project, the applicant would be required to comply with the NPDES regulations and apply for coverage under the CGP because ground disturbance at the Project site would exceed one acre. Under the CGP, the Project applicant or their contractor(s) would be required to prepare and implement a SWPPP. The SWPPP must include site-specific erosion and sedimentation control practices and would limit the amount of runoff that may be directed offsite during construction. Additionally, consistent with CGP SWPPP requirements, an Erosion Control Plan (Callander Associates Landscape Architects, 2024)23 has been prepared for the Project that details BMPs to be implemented as part of the Project, including protecting temporary stockpiles from erosion and stormwater run-on and runoff, erosion control type and placement, stormwater drainage control, secondary containment, fugitive emission control of dust, and spill prevention.

Following the completion of construction (post-construction), the Project’s stormwater entering the City’s municipal stormwater system would be subject to compliance with the City’s MS4 General Permit. Adherence to the requirements of the MS4 General Permit, in combination with Project design features (such as site grading, clean soil cover, rehabilitated drainage structures, riprap placement in swales, and soil revegetation, and pollutant source controls) would ensure erosion, siltation, and polluted runoff are avoided and/or minimized as compared to existing conditions. Further, as described under a), above, implementation of the proposed Project would reduce the potential for stormwater to contact onsite legacy wastes and lead contaminated soil, reducing the potential for pollutants and contaminants to be transported off-site by stormwater as compared to existing conditions.

Compliance with NPDES requirements and the implementation of required BMPs would prevent erosion and sediment transport both on- and off-site during construction and the Project design would ensure post-construction stormwater discharges would not be increased and that pollutants, including sediment, would not be transported offsite in a manner that would degrade the water quality of receiving waters (i.e., the Napa River).

Therefore, impacts related to erosion, siltation, or creating additional sources of polluted runoff would be less than significant.

The Project site is not located within a 100-year24 flood hazard zone designated by the Federal Emergency Management Agency (FEMA). Implementation of the Project would not result in the installation of any facilities within a 100-year or 500-year flood zone; implementation of the Project would not impede or redirect floodwaters on- or offsite.

The Project would not result in substantially altered on-site drainage patterns of the site or area or increased peak stormwater discharge rates or volumes, including through the addition of impervious surfaces, as compared to existing conditions. Therefore, peak 23 Erosion Control Plan is in Appendix B of the RAP which is found in Appendix B of this Initial Study. 24 Areas subject to inundation by the 1-percent-annual-chance flood event

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Napa Hidden Glen Remediation Project 62 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 stormwater discharge rates and volumes from the Project site would not be substantially altered as compared to those occurring under existing conditions. The stormwater collected from the site would continue to be conveyed to the City’s municipal stormwater system via the drainage structures comprised of riprap armored swales and storm drain inlets located adjacent to Pascale Place and in the southeastern corner of the site. Further, the stormwater drainage structures that are proposed to be improved as part of the Project have been designed with sizing, stability, and capacity to safely convey storm flows consistent with those currently installed under existing conditions. Additionally, implementing the Project would reduce, minimize, and avoid stormwater contacting legacy waste-impacted soils (such as those with elevated lead concentrations), reducing the potential for stormwater runoff to transport contaminants off-site to downgradient receiving waters as compared to existing conditions. Therefore, the Project would result in a less-than-significant impact.
d) Less-Than-Significant Impact. A seiche is caused by oscillation of the surface of a large enclosed or semi-enclosed body of water due to an earthquake or large wind event. The Project site is not located near a large enclosed or semi-enclosed body of water. The Project site is not in a tsunami hazard inundation zone (CGS, 2025). As described under c), above, the Project site is not located within a 100-year flood hazard zone designated by FEMA. Therefore, the Project would result in a less-than-significant impact. e) Less-Than-Significant Impact. The RWQCB’s Basin Plan (RWQCB, 2019) is the principal water quality planning document for the region. The Basin Plan water quality objectives are designed to preserve and enhance water quality and protect the beneficial uses of all regional terrestrial surface water bodies (e.g., creeks, rivers, streams, and lakes) and groundwaters within the RWQCB’s jurisdictional area. As discussed above under a), c), and d), the Project would not cause any significant impact related to surface or groundwater quality degradation. The Basin Plan water quality objectives are designed to preserve and enhance water quality and protect the beneficial uses25 of all regional terrestrial surface water bodies (e.g., creeks, rivers, streams, and lakes) and groundwaters within the RWQCB’s jurisdictional area. The Project would comply with the requirements of the NPDES Permit program during and following completion of construction, including implementation of BMPs and other requirements of a SWPPP, which are designed to ensure stormwater discharges associated with construction and long-term use of the Project site comply with the Basin Plan water quality standards. The Project would not require substantial groundwater withdrawals or reduce groundwater recharge, as discussed under b), and therefore would not conflict with or obstruct implementation of a sustainable groundwater management plan. Therefore, the Project would result in a less-than-significant impact.
25 Aquatic resources provide many different benefits. Beneficial uses are those resources, services, and/or qualities of aquatic systems that are to be maintained and are the ultimate goals for protecting and achieving high water quality.

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Napa Hidden Glenn Remediation Project 63 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 References
Callander Associates Landscape Architects, 2024. Hidden Glen Dump Remediation, Erosion Control Plan. CALA Project No. 17058A. October, 2024.

California Department of Conservation, California Geological Survey (CGS), 2025. Tsunami Hazard Area Map, City of Napa; produced by the California Geological Survey. Accessed online on March 26, 2025 at: https://maps.conservation.ca.gov/cgs/informationwarehouse/ts_evacuation/ City of Napa, 2025. Stormwater Quality. Accessed online March 28, 2025 at:
https://www.cityofnapa.org/574/Stormwater-Quality
Federal Emergency Management Agency (FEMA), 2025. National Flood Hazard Layer FIRMette.

Ninyo and Moore, 2024. Remedial Action Plan, Hidden Glen Dump, Coombsville Road, Napa, California. SWIS No. 28-AA-0028. Prepared for Napa County Local Enforcement Agency.

Project No. 109558001, October, 2024.

Regional Water Quality Control Board San Francisco Bay Region (RWQCB), 2019. San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan). Incorporating all amendments approved by the Office of Administrative Law as of November 5, 2019. Accessed online on March 28, 2025 at:
https://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/planningtmdls/basinplan /web/bp_ch1-7_print.html
RWQCB, 2025. Final California 2020 Integrated Report (303(d) List/305(b) Report). Accessed online on March 28, 2025 at:
https://www.waterboards.ca.gov/water_issues/programs/tmdl/2023_2024state_ir_reports/apx-bfactsheets/03334.shtml _________________________

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 64 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025

LAND USE AND LAND USE PLANNING
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

11. LAND USE AND LAND USE PLANNING — Would the
proposed project:

a) Physically divide an established community? ☐ ☐ ☐ ☒
b) Cause a significant environmental impact due to a
conflict with any land use plan, policy, or regulation
adopted for the purpose of avoiding or mitigating an
environmental effect?
☐ ☐ ☐ ☒
Discussion
a, b) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. The Project would not divide an established community as the site would remain vacant and would not be developed. Because the Project does not propose development or a change in activities on the Project site, the Project would not conflict with any land use plans, policies, or regulations. Therefore, the Project would result in no impact. _________________________

MINERAL RESOURCES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

12. MINERAL RESOURCES — Would the proposed
project:

a) Result in the loss of availability of a known mineral resource that would be of value to the region and the
residents of the state?
☐ ☐ ☐ ☒
b) Result in the loss of availability of a locally important mineral resource recovery site delineated on a local
general plan, specific plan or other land use plan?
☐ ☐ ☐ ☒
Discussion
a, b) No Impact. The California Department of Conservation Mines Online tool does not identify any documented mines on or nearby the Project site (California Department of Conservation, 2025). Thus, the Project would not affect any known mineral deposits or active mining operations in the City. In addition, the Project site does not contain a locally important mineral resource. Therefore, the Project would result in no impact.

References
Department of Conservation, Division of Mine Reclamation, Mines Online. https://maps.conservation.ca.gov/mol/index.html. Accessed March 4, 2025.

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Napa Hidden Glenn Remediation Project 65 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 _________________________
NOISE
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

13. NOISE — Would the proposed project result in:
a) Generation of a substantial temporary or permanent
increase in ambient noise levels in the vicinity of the project in excess of standards established in the local general plan or noise ordinance, or applicable
standards of other agencies?
☐ ☐ ☒ ☐
b) Generation of excessive groundborne vibration or
groundborne noise levels? ☐ ☐ ☒ ☐
c) For a project located within the vicinity of a private airstrip or an airport land use plan or, where such a
plan has not been adopted, within two miles of a
public airport or public use airport, would the project expose people residing or working in the project area
to excessive noise levels?
☐ ☐ ☐ ☒
Introduction
RCH conducted several short-term noise measurements at the Project site on February 26, 2025.

The results and locations of the short-term noise measurements are provided in the discussion below.

Sound is mechanical energy transmitted by pressure waves through a medium such as air. Noise is defined as unwanted sound. Sound pressure level has become the most common descriptor used to characterize the “loudness” of an ambient sound level. Sound pressure level is measured in decibels (dB), with zero dB corresponding roughly to the threshold of human hearing, and 120 to 140 dB corresponding to the threshold of pain. Decibels are measured using different scales, and it has been found that A-weighting of sound levels best reflects the human ear’s reduced sensitivity to low frequencies, and correlates well with human perceptions of the annoying aspects of noise. The A-weighted decibel scale (dBA)is cited in most noise criteria. All references to decibels (dB) in this report will be A-weighted unless noted otherwise.

Several time-averaged scales represent noise environments and consequences of human activities.

The most commonly used noise descriptors are the equivalent A–weighted sound level over a given time period (Leq)26; average day–night 24-hour average sound level (Ldn)27 with a nighttime increase of 10 dB to account for sensitivity to noise during the nighttime; and community noise equivalent level (CNEL)28, also a 24-hour average that includes both an evening and a nighttime sensitivity weighting. Table 4 identifies decibel levels for common sounds heard 26 The Equivalent Sound Level (Leq) is a single value of a constant sound level for the same measurement period duration, which has sound energy equal to the time–varying sound energy in the measurement period. 27 Ldn is the day–night average sound level that is equal to the 24-hour A-weighted equivalent sound level with a 10-decibel penalty applied to night between 10:00 p.m. and 7:00 a.m.
28 CNEL is the average A-weighted noise level during a 24-hour day, obtained by addition of 5 decibels in the evening from 7:00 to 10:00 p.m., and an addition of a 10–decibel penalty in the night between 10:00 p.m. and 7:00 a.m.

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Napa Hidden Glen Remediation Project 66 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 in the environment. With regard to increases in A-weighted noise level, the following relationships occur (Caltrans, 1998a):
 Under controlled conditions in an acoustics laboratory, the trained healthy human ear is able to discern changes in sound levels of 1 dB;
 Outside of such controlled conditions, the trained ear can detect changes of 2 dB in normal environmental noise;
 It is widely accepted that the average healthy ear, however, can barely perceive noise levels changes of 3 dB;
 A change in level of 5 dB is a readily perceptible increase in noise level; and  A 10-dB change is recognized as twice as loud as the original source.

TABLE 4 TYPICAL NOISE LEVELS
Noise Level (dB) Outdoor Activity Indoor Activity
90+ Gas lawn mower at 3 feet, jet flyover at
1,000 feet Rock Band
80-90 Diesel truck at 50 feet Loud television at 3 feet 70-80 Gas lawn mower at 100 feet, noisy urban
area
Garbage disposal at 3 feet, vacuum cleaner at
10 feet
60-70 Commercial area
40-60 Quiet urban daytime, traffic at 300 feet Large business office, dishwasher next room 20-40 Quiet rural, suburban nighttime Concert hall (background), library, bedroom at night
10-20 Broadcast / recording studio
0 Lowest threshold of human hearing Lowest threshold of human hearing SOURCE: (modified from Caltrans Technical Noise Supplement, 1998) Noise Attenuation
Stationary point sources of noise, including construction equipment, attenuate (lessen) at a rate of 6 to 7.5 dB per doubling of distance from the source, depending on ground absorption. Soft sites attenuate at 7.5 dB per doubling because they have an absorptive ground surface such as soft dirt, grass, or scattered bushes and trees. Hard sites have reflective surfaces (e.g., parking lots or smooth bodies of water) and therefore have less attenuation (6.0 dB per doubling). A street or roadway with moving vehicles (known as a “line” source), would typically attenuate at a lower rate, approximately 3 to 4.5 dB each time the distance doubles from the source, that also depends on ground absorption (Caltrans, 1998b). Physical barriers located between a noise source and the noise receptor, such as berms or sound walls, would increase the attenuation that occurs by distance alone.

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 67 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Sensitive Receptors
Some land uses are considered more sensitive to ambient noise levels than others due to the amount of noise exposure, in terms of both duration and insulation from noise, and the types of activities typically involved. Residences, hospitals, schools, and nursing homes are generally more sensitive to noise than commercial and industrial land uses. The City of Napa General Plan identifies noisesensitive land uses as residences, religious facilities, schools, childcare centers, hospitals, long-term health care facilities, convalescent centers, and retirement homes (City of Napa, 2022). The Project site is in a residential setting with adjacent residential properties to the north, east, and south (See the Project Description for the distances between the nearest residential structures and the Project property line). Silverado Middle School is approximately ¼ mile east of the Project site.

Existing Noise Sources
To quantify existing ambient noise levels, RCH Group conducted four short-term (10-minute) noise measurements on and nearby the Project site. Short-term measurements were made using a Larson Davis SoundTrack LxT Sound Level Meter calibrated before and after measurements.

Table 5 summarizes the locations and results of the noise measurements. Figure 7 shows the locations of the noise measurements. The main source of noise in and around the Project vicinity is traffic noise on Coombsville Road and Pascale Place. Other minor noise sources included birds, dogs barking, and wind.

TABLE 5 EXISTING NOISE LEVELS
Location Time Period Noise Levels (dB) Noise Sources
Site 1: Northwest area of
the Project site, nearby
private residence (Lot 9).

Tuesday February 26, 2025
2:06 p.m. to 2:16 p.m.
5-minute Leq’s:
47, 43
Birds were 45-56 dB. Distant
traffic on Coombsville Road
was 40-45 dB. Wind was 37-
39 dB.

Site 2: Southern area of the
Project site, nearby private
residence (Lot 6).

Tuesday February 26, 2025
2:17 p.m. to 2:27 p.m.
5-minute Leq’s:
40, 38
Distant traffic on Coombsville
Road was 40-42 dB. Dog
barking in the distance was 40
dB.

Site 3: East of the Project
site, along Pascale Place.

Tuesday February 26, 2025
2:30 p.m. to 2:40 p.m.
5-minute Leq’s:
47, 49
Cars passing on Pascale Place
was 60-65 dB. Distant traffic
on Coombsville Road was 40-
43 dB.

Site 4: 100 feet north of
intersection of Coombsville
Road and El Monte Way.

Tuesday February 26, 2025
2:44 p.m. to 2:54 p.m.
5-minute Leq’s:
59, 63
Constant traffic on
Coombsville Road was 60-70
dB.

SOURCE: RCH GROUP, 2025

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 68 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Figure 7 Noise Measurement Locations

Legend
= noise measurement location
= approximate project site location
Base Map Source: Google Earth, 2025.
®
D
RCHGR:)UP pbining &~-ltros

ENVIRONMENTAL CHECKLIST
Napa Hidden Glenn Remediation Project 69 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 Regulatory Context
Federal and State
There are no federal or state noise standards that regulate noise issues related to the Project.

Local
City of Napa
City of Napa 2040 General Plan
The City of Napa 2040 General Plan Safety and Noise Element provides a framework to minimizing risks posed by excessive noise. The City of Napa General Plan identifies vehicle traffic on highways and streets, trains, aircraft, car washes, construction, agricultural activities, landscaping, and HVAC equipment as the major sources of noise in the City (City of Napa, 2022).

City of Napa Municipal Code
The City of Napa Municipal Code provides allowable construction hours. The following regulation is relevant to the Project.

Per Section 8.08.025, Any person engaged in construction activity, other than construction activity on an existing residential unit which such a person owns or rents, pursuant to any provision of this code, shall limit said construction activity as follows: (A) Construction activities throughout the entire duration of the project shall be limited to the hours of 7:00 a.m. to 7:00 p.m., Monday through Friday. There will be no start up of machines nor equipment prior to 8:00 a.m., Monday through Friday; no delivery of materials nor equipment prior to 7:30 a.m. nor past 5:00 p.m., Monday through Friday; no cleaning of machines nor equipment past 6:00 p.m., Monday through Friday; no servicing of equipment past 6:45 p.m., Monday through Friday; and construction on weekends or legal holidays shall be limited to the hours of 8:00 a.m. to 4:00 p.m., unless a permit shall first have been secured from the City Manager, or designee, pursuant to Section 8.08.050 of this code. The City Manager, or designee, shall grant such permit: (1) For emergency work; (2) Other work, if work and equipment will not create noise that may be unreasonably offensive to neighbors as to constitute a nuisance; or (3) If necessary to protect public health, safety, and welfare. (B) All muffler systems on construction equipment shall be properly maintained. (C) All construction equipment shall not be placed adjacent to developed areas unless said equipment is provided with acoustical shielding. (D) All construction and grading equipment shall be shut down when not actively in use. (E) Construction activity by or on behalf of a public agency, which is necessary to avoid a disruption of a public project or to protect the public health, safety, and welfare, shall be exempt from the time limitations of this section.

Discussion
a) Less-than-Significant Impact. Construction would result in a temporary increase in ambient noise levels in the vicinity of the Project. Construction activities would require the use of numerous pieces of noise-generating equipment, such as excavating machinery. The noise levels generated by construction equipment would vary greatly

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 70 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 depending upon factors such as the type and specific model of the equipment, the operation being performed, the condition of the equipment, and the prevailing wind direction. Construction equipment would not all operate at the same time or location.

Furthermore, construction equipment would not be in constant use during the 8-hour operating day. Table 6 provides the noise levels at 25 and 50 feet from expected construction equipment.

TABLE 6 TYPICAL CONSTRUCTION EQUIPMENT NOISE LEVELS (LMAX) Construction
Equipment
Noise Level (dB, Lmax at 50
feet)
Noise Level (dB, Lmax at 25
feet)
Backhoe 78 84
Compactor 83 89
Dump Truck 76 82
Dozer 82 88
Excavator 81 87
SOURCE: FHWA Roadway Construction Noise Model User’s Guide, 2006 As discussed above, the Project site is in a residential setting with adjacent residential properties to the north, east, and south (with structures as close as 9 feet to the Project boundary). Due to the proximity of nearby noise sensitive receptors, construction noise would temporarily elevate the existing ambient noise levels (See Table 5, for existing noise levels at Sites 1-2 [i.e., the ambient noise levels nearby the private residences are quiet]). These noise levels would not exceed the noise ordinance as it does not contain sound level limitations and only restricts construction hours of operation and requires muffler systems to be maintained, acoustic shielding, and idling restrictions. Construction activities would be short-term (approximately three months), intermittent, and limited to the allowable hours (daytime) outlined in City of Napa Municipal Code Section 8.08.025, described above. Aside from the allowable hours in the City of Napa Municipal Code, no other standards have been established in the General Plan, Municipal Code, or by other agencies that are applicable to the Project construction activities. Therefore, Project construction would result in a less-than-significant impact. b) Less-than-Significant Impact. Construction activities have the potential to result in varying degrees of temporary ground vibration, depending on the specific construction equipment used and operations involved. In most cases, vibration induced by typical construction equipment does not result in adverse effects on people or structures (Caltrans, 2013). At the highest levels of vibration, damage to structures is primarily architectural (e.g., loosening and cracking of plaster or stucco coatings) and rarely results in structural damage. Vibratory motion is commonly described by identifying the peak particle velocity (PPV).

For vibration, a PPV threshold of 0.5 inches per second or greater can cause architectural damage and minor structural damage. The FTA recommends a threshold of 0.5 PPV for residential and commercial structures (FTA, 2006). Vibrational effects from typical

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Draft Initial Study/Mitigated Negative Declaration July 2025 construction activities are only a concern within 25 feet of existing structures (Caltrans, 2002b). Although nearby off-site structures would be as close as 25 feet of the Project site, heavy vibration-inducing equipment would not be used in close proximities to off-site structures. Instead, smaller equipment (such as skid-steers) and hand-digging tools would be used along the Project boundaries and adjacent to nearby residences. These methods would not generate significant vibration that could exceed 0.5 PPV. Therefore, the Project would result in a less-than-significant impact.
c) No Impact. The Project site is not within the vicinity of a private airstrip or an airport land use plan, or within two miles of a public use airport. The nearest airport is the Napa County Airport (the nearest runway of which is approximately 5 miles south of the Project site). Therefore, the Project would result in no impact.

References
California Department of Transportation (Caltrans). 1998a. Technical Noise Supplement. https://rosap.ntl.bts.gov/view/dot/27590
California Department of Transportation (Caltrans). 1998b. Traffic Noise Analysis Protocol for New Highway Construction and Reconstruction Projects. https://dot.ca.gov/-/media/dotmedia/programs/environmental-analysis/documents/env/f0008617-traffic-noise-protocoloct1998-a11y.pdf City of Napa. 2022. City of Napa 2040 General Plan. https://www.cityofnapa.org/259/GeneralPlan Federal Highway Administration (FHWA). 2006. Roadway Construction Noise Model User’s Guide. https://www.fhwa.dot.gov/environment/noise/construction_noise/handbook/ _________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

POPULATION AND HOUSING
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

14. POPULATION AND HOUSING — Would the proposed
project:

a) Induce substantial unplanned population growth in
an area, either directly (for example, by proposing
new homes and businesses) or indirectly (for
example, through extension of roads or other
infrastructure)?
☐ ☐ ☐ ☒
b) Displace substantial numbers of existing people or
housing units, necessitating the construction of
replacement housing elsewhere?
☐ ☐ ☐ ☒
Discussion
a) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not directly or indirectly induce substantial unplanned population growth in the area. Therefore, the Project would result in no impact. b) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not displace existing people or housing units and would not require the construction of replacement housing. Therefore, the Project would result in no impact. _________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

PUBLIC SERVICES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

15. PUBLIC SERVICES — Would the proposed project:
a) Result in substantial adverse physical impacts associated with the provision of, or the need for, new or
physically altered governmental facilities, the
construction of which could cause significant
environmental impacts, in order to maintain
acceptable service ratios, response times, or other
performance objectives for any of the following
public services:

i) Fire protection? ☐ ☐ ☒ ☐
ii) Police protection? ☐ ☐ ☒ ☐
iii) Schools? ☐ ☐ ☐ ☒
iv) Parks? ☐ ☐ ☐ ☒
v) Other public facilities? ☐ ☐ ☐ ☒
Introduction
Fire Protection
The City of Napa Fire Department provides fire protection services to the City of Napa. The City of Napa Fire Department operates five stations throughout the City (City of Napa, 2022). The nearest fire station to the site is the Napa Fire Department Station 1, located approximately 1.3 miles west of the Project site.

Police Protection
The City of Napa Police Department provides law enforcement services to the City. The City of Napa Police Department has 76 sworn personnel and 71 professional staff.29 The City of Napa Police Department is located approximately 1.3 miles west of the Project site.

Discussion
a.i) Less-than-Significant Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not result in an increase in calls for fire and emergency protection services that would warrant changes to fire protection service ratios and/or response times. Therefore, the Project would result in a less-than-significant impact. a.ii) Less-than-Significant Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not result in an increase in calls for police protection or 29 https://www.cityofnapa.org/323/Police-Department

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Draft Initial Study/Mitigated Negative Declaration July 2025 result in any changes in crime that would warrant changes to police protection service ratios and/or response times. Therefore, the Project would result in a less-than-significant impact.
a.iii-v) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not result in an increase in employment. Therefore, the Project would not warrant a need for new schools, parks, or other public facilities, and would result in no impact.
_________________________

RECREATION
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

16. RECREATION — Would the proposed project:
a) Increase the use of existing neighborhood and regional parks or other recreational facilities such that
substantial physical deterioration of the facilities would occur or be accelerated?
☐ ☐ ☐ ☒
b) Include recreational facilities or require the
construction or expansion of recreational facilities
that might have an adverse physical effect on the
environment?
☐ ☐ ☐ ☒
Discussion
a, b) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Because the Project does not propose development or a change in activities on the Project site, the Project would not increase the use of existing recreational facilities such that physical deterioration of existing facilities would occur or be accelerated, and would not warrant new or expanded recreational facilities. Therefore, the Project would result in no impact. _________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

TRANSPORTATION
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

17. TRANSPORTATION — Would the proposed project:
a) Conflict with a program plan, ordinance or policy
addressing the circulation system, including transit,
roadway, bicycle and pedestrian facilities?
☐ ☐ ☒ ☐
b) Would the project conflict or be inconsistent with CEQA Guidelines section 15064.3, subdivision (b)? ☐ ☐ ☒ ☐
c) Substantially increase hazards due to a geometric
design feature (e.g., sharp curves or dangerous
intersections) or incompatible uses (e.g., farm
equipment)?
☐ ☐ ☒ ☐
d) Result in inadequate emergency access? ☐ ☐ ☒ ☐
Introduction
Senate Bill 743
Senate Bill 743 (SB 743; Steinberg, 2013) governs the application of new State CEQA Guidelines for addressing transportation impacts based on Vehicle Miles Traveled (VMT). It was codified in Public Resources Code §21099, required changes to the guidelines implementing CEQA (State CEQA Guidelines) (Cal. Code Regs., Title 14, Div. 6, Ch. 3, § 15000 et seq.) regarding the analysis of transportation impacts. The Governor’s Office of Planning and Research (OPR) has proposed, and the California Natural Resources Agency (Agency) has certified and adopted, changes to the State CEQA Guidelines that identify VMT as the most appropriate metric to evaluate a project’s transportation impacts. With the Agency’s certification and adoption of the changes to the State CEQA Guidelines, automobile delay, as measured by “level of service” and other similar metrics, generally no longer constitutes a significant environmental effect under CEQA. (Pub. Resources Code, § 21099, subd. (b)(3).)”
The OPR’s Technical Advisory on Evaluating Transportation Impacts in CEQA (OPR, 2018) provides general direction regarding the methods to be employed and significance criteria to evaluate VMT impacts, absent policies adopted by local agencies.

Project Trip Generation
As noted in the Project Description, the Project site would be accessed via Pascale Place where construction crews would park, and equipment can be staged and transported to the Project site or by an alternative access road that would be constructed between the Project site and El Monte Way. Project operations would not result in any new vehicle trips.

Discussion
a) Less-than-Significant Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Typical of any construction project, the Project could result intermittent

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Draft Initial Study/Mitigated Negative Declaration July 2025 stoppages of vehicles, bicycles, or pedestrians for heavy equipment and haul trucks to safely enter and exit the site. The Project would not substantially change the pedestrian or bicycle traffic in the area and would not significantly impact or require changes to the design of any existing or planned bicycle or pedestrian facilities. Because the Project does not propose development or a change in activities on the Project site, the Project would not generate new trips during operations and therefore would not conflict with any program, plan, or policy addressing the circulation system in the City. Therefore, the Project would result in a less-than-significant impact. b) Less-than-Significant Impact. VMT refers to the amount and distance of vehicle travel attributable to a project. VMT generally represents the number of vehicle trips generated by a project multiplied by the average trip length for those trips. For CEQA transportation impact assessment, VMT is calculated using the origin-destination VMT method, which accounts for the full distance of vehicle trips to and from the Project site.

The OPR’s Technical Advisory on Evaluating Transportation Impacts in CEQA provides general direction regarding the methods to be employed and significance criteria to evaluate VMT impacts, absent policies adopted by local agencies. The directive addresses several aspects of VMT impact analysis, and is organized as follows:
 Screening Criteria: Screening criteria are intended to quickly identify when a project should be expected to cause a less-than-significant VMT impact without conducting a detailed study.
 Significance Thresholds: Significance thresholds define what constitutes an acceptable level of VMT and what could be considered a significant level of VMT requiring mitigation.
 Analysis Methodology: These are the potential procedures and tools for producing VMT forecasts to use in the VMT impact assessment.
 Mitigation: Projects that are found to have a significant VMT impact based on the County’s significance thresholds are required to implement mitigation measures to reduce impacts to a less-than-significant level (or to the extent feasible).

Screening Criteria
Screening criteria can be used to quickly identify whether sufficient evidence exists to presume a project would have a less-than-significant VMT impact without conducting a detailed study. However, each project should be evaluated against the evidence supporting that screening criteria to determine if it applies. Projects meeting at least one of the criteria below can be presumed to have a less than significant VMT impact, absent substantial evidence that the project will lead to a significant impact.

The extent to which the Project qualifies under each criterion is noted below.  Regional Truck Traffic: The OPR directive specially focuses on the need to evaluate residential and employment-based travel, either from the standpoint of

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Draft Initial Study/Mitigated Negative Declaration July 2025 home-based trips or through evaluation of commute trips associated with employment centers. Consistent with Section 15064.3 of the State CEQA Guidelines, impacts from regional truck traffic are not included in the VMT estimates, but are considered from an operational standpoint as they relate to safety.  Small Projects: Defined as a project that generates 110 or fewer average daily vehicle trips.
 Affordable Housing: Defined as a project consisting of deed-restricted affordable housing.
 Local-Serving Non-Residential Development: The directive notes that local serving retail uses can reduce travel by offering customers more choices in closer proximity.

Local serving retail uses of 50,000 square feet or less can be presumed to have a lessthan-significant impact.  Projects in Low VMT-Generating Area: Defined as a residential or office project that is in a VMT efficient area based on an available VMT Estimation Tool. The project must be consistent in size and land use type (i.e., density, mix of uses, transit accessibility) as the surrounding built environment.
 Proximity to High Quality Transit: The directive notes that employment and residential development located within a half mile of a high-quality transit corridor can be presumed to have a less-than-significant impact.

Impact Conclusion
The extent to which the Project’s VMT impacts can be presumed to be less than significant has been determined based on review of the OPR’s screening criteria and general guidance. The OPR’s Small Project criteria is applicable to the Project. The Project would not generate long term automobile trips. Project construction would require an average of 10 workers per day resulting in approximately 20 automobile trips per day.

The Project would also generate between approximately 14 to 24 haul truck trips per day depending upon the given phase (for waste-impacted soil export or clean fill import).

Consistent with Section 15604.3 of the State CEQA Guidelines, impacts from regional truck traffic are not included in the VMT estimates. As the 110 average daily trips threshold would not be exceeded, the Project’s VMT impacts can be presumed to be less than significant. Therefore, the Project would result in a less-than-significant impact. c) Less-than-Significant Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. The temporary access road for the Project would not be accessible to the public and the Project would not result in permanent changes to the existing roadways. The Project would not involve any new hazardous design or feature. The Project would not result in permanent changes to roadways and would not create any significant impacts to pedestrians, bicyclists, or traffic operations. Therefore, the Project would result in a lessthan-significant impact.

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Draft Initial Study/Mitigated Negative Declaration July 2025 d) Less-than-Significant Impact. The Project would not substantially increase hazards to vehicle safety due to increased traffic, which could result in inadequate emergency access.

The Project site is vacant, and no emergency vehicle access is required. In addition, the addition of traffic from Project construction traffic would not result in any significant changes to emergency vehicle response times in the area. Therefore, the Project would result in a less-than-significant impact.

References
California Governor’s Office of Planning and Research (OPR). 2018. Technical Advisory on Evaluating Transportation Impacts in CEQA, April 2018.
_________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

TRIBAL CULTURAL RESOURCES
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

18. TRIBAL CULTURAL RESOURCES —
Would the proposed project cause a substantial adverse change in the significance of a tribal cultural resource, defined in Public Resources Code section 21074 as either a site, feature, place, cultural landscape that is geographically defined in terms of the size and scope of the landscape, sacred place, or object with cultural value to a California Native American tribe, and that is:
a) Listed or eligible for listing in the California Register of Historical Resources, or in a local register of historical resources as defined in Public Resources Code section
5020.1(k), or
☐ ☐ ☒ ☐
b) A resource determined by the lead agency, in its
discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in subdivision (c) of Public Resources Code Section 5024.1. In applying
the criteria set forth in subdivision (c) of Public
Resources Code Section 5024.1, the lead agency shall
consider the significance of the resource to a California Native American Tribe.
☐ ☒ ☐ ☐
Introduction
Tribal Cultural Resources (TCR’s) include sites, features, places, cultural landscapes, and sacred places or objects that have cultural value or significance to a Tribe. To qualify as a TCR, the resource must either: 1) be listed on, or be eligible for, listing on the California Register of Historical Resources (CRHR) or other local historic register; or 2) constitute a resource that the lead agency, at its discretion and supported by substantial evidence, determines should be treated as a TCR (PRC §21074). Under Assembly Bill 52 (AB 52) tribal representatives are considered experts appropriate for providing substantial evidence regarding the locations, types, and significance of TCRs within their traditional and cultural affiliated geographic area, and therefore, the identification and analysis of TCRs should involve government-to-government tribal consultation between the CEQA lead agency and interested tribal groups and/or tribal persons. (PRC §21080.3.1(a)).

The City of Napa notified the following tribes requesting Assembly Bill (AB) 52 notification for projects subject to CEQA.

1. Confederated Villages of Lisjan Nation

2. Yocha Dehe Wintun Nation
The City sent project notification letters via certified mail to both tribes and neither tribe requested formal consultation within 30 days of receipt of the notification letter. No TCRs were discovered during the cultural resources investigation of the Project site (NIC, 2025).

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Draft Initial Study/Mitigated Negative Declaration July 2025 Discussion
a) Less-than-Significant Impact. No cultural resources either listed or eligible for listing by the State or local listing were identified on the Project site as a result of the records search and AB 52 consultation. Therefore, the Project would result in a less-thansignificant impact. b) Less-than-Significant Impact with Mitigation. Archival research and an intensive field survey did not identify any significant archaeological or cultural resources within the Project area (NIC, 2025). The survey noted that due to the burning of waste products, earth moving, introduction of outside soils, use of heavy machinery, and contamination of the Project area, the likelihood of finding buried cultural resources, archaeological resources, or human remains is low. Furthermore, Mitigation Measures CUL-1 through CUL-2 require procedures for the inadvertent discovery of cultural resources and tribal cultural resources and human remains. Therefore, the Project would result in a less-thansignificant impact.

References
Natural Investigations Company (NIC), 2025. Cultural Resources Investigation for the Napa Hidden Glen Dump Remediation, Napa County. March 2025.
_________________________

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Draft Initial Study/Mitigated Negative Declaration July 2025

UTILITIES AND SERVICE SYSTEMS
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

19. UTILITIES AND SERVICE SYSTEMS — Would the
proposed project:

a) Require or result in the relocation or construction of new or expanded water, wastewater treatment or
storm water drainage, electric power, natural gas, or
telecommunications facilities, the construction or
relocation of which could cause significant
environmental effects?
☐ ☐ ☐ ☒
b) Have sufficient water supplies available to serve the project and reasonably foreseeable future
development during normal, dry and multiple dry
years?
☐ ☐ ☐ ☒
c) Result in a determination by the wastewater treatment provider that would serve the project that it has
adequate capacity to serve the project’s projected
demand in addition to the provider’s existing
commitments?
☐ ☐ ☐ ☒
d) Generate solid waste in excess of State or local
standards, or in excess of the capacity of local
infrastructure, or otherwise impair the attainment of
solid waste reduction goals?
☐ ☐ ☒ ☐
e) Comply with federal, state, and local management and reduction statutes and regulations related to solid
waste?
☐ ☐ ☒ ☐
Discussion
a) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. The Project site would not require new utilities related to water and wastewater treatment, stormwater, telecommunication, natural gas or electric power services. Therefore, the Project would result in no impact.
b) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. The Project would have no long-term water demand and would not adversely affect the water supply.

Therefore, the Project would result in no impact.
c) No Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. The Project would not generate any wastewater and would not require additional capacity beyond the wastewater treatment. Therefore, the Project would result in no impact. d, e) Less-than-Significant Impact. The Project consists of short-term remediation activities and would not result in development or a change from existing operations at the vacant property. Construction of the Project would not generate a significant amount of solid

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Draft Initial Study/Mitigated Negative Declaration July 2025 waste as only soil would be removed from the site. Waste-impacted soil that is hauled offsite would be hauled to an appropriate landfill for disposal and would not exceed the capacity of local landfills. The Project would comply with all federal, state, and local statutes and regulations related to solid waste. Therefore, the Project would result in a less-than-significant impact.
_________________________

WILDFIRE
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

20. WILDFIRE —
If located in or near state responsibility areas or lands classified as very high hazard severity zones, would the proposed project:
a) Substantially impair an adopted emergency response
plan or emergency evacuation plan? ☐ ☐ ☐ ☒
b) Due to slope, prevailing winds, and other factors,
exacerbate wildfire risks, and thereby expose project
occupants to, pollutant concentrations from a wildfire
or the uncontrolled spread of a wildfire?
☐ ☐ ☐ ☒
c) Require the installation or maintenance of associated infrastructure (such as roads, fuel breaks, emergency
water sources, power lines or other utilities) that may exacerbate fire risk or that may result in temporary or ongoing impacts to the environment?
☐ ☐ ☐ ☒
d) Expose people or structures to significant risks,
including downslope or downstream flooding or
landslides, as a result of runoff, post-fire slope
instability, or drainage changes?
☐ ☐ ☐ ☒
Introduction
Areas where the state has financial responsibility for wildland fire protection are known as state responsibility areas (SRA). The Department of Forestry and Fire Protection (CALFIRE) is responsible for fire prevention and suppression in SRA. Areas where local governments have financial responsibility for wildland fire protection are known as local responsibility areas (LRA).

The Project site is not located in a SRA or a very high fire hazard severity zone (VHFHSZ). The Project is located in an LRA and is within a Moderate severity zone. The City of Napa Fire Department provides fire protection services to the City of Napa. The City of Napa Fire Department operates five stations throughout the City (City of Napa, 2022). The nearest fire station to the site is the Napa Fire Department Station 1, located approximately 1.3 miles west of the Project site.

Discussion
a) No Impact. The Project would not involve the closure or alteration of any existing evacuation route that would be important in the event of a wildfire. The Project would not

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Draft Initial Study/Mitigated Negative Declaration July 2025 impede or require diversion of rescue vehicles or evacuation traffic in the event of a wildfire. Therefore, the Project would result in no impact. b) No Impact. There are no elements of the Project that would exacerbate wildland fire risk in the Project area due to slope, prevailing winds, and other factors. Therefore, the Project would result in no impact.
c) No Impact. There are no elements of the Project that would exacerbate wildland fire risk in the Project area, which is a regularly mowed vacant lot. Therefore, the Project would result in no impact.
d) No Impact. There are no elements of the Project that would expose people or structures to flooding or landslides by runoff flow, post-fire instability, or drainage changes.

Therefore, the Project would result in no impact.

References
CALFIRE. 2025. Fire Hazard Severity Zones in State Responsibility Area, https://osfm.fire.ca.gov/what-we-do/community-wildfire-preparedness-and-mitigation/firehazard-severity-zones, accessed April 9, 2025 _________________________

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MANDATORY FINDINGS OF SIGNIFICANCE
Issues (and Supporting Information Sources):

Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Incorporation
Less Than
Significant
Impact No Impact

21. MANDATORY FINDINGS OF SIGNIFICANCE —
Would the proposed project:

a) Have the potential to substantially degrade the
quality of the environment, substantially reduce the
habitat of a fish or wildlife species, cause a fish or
wildlife population to drop below self-sustaining
levels, threaten to eliminate a plant or animal
community, substantially reduce the number or
restrict the range of a rare or endangered plant or
animal, or eliminate important examples of the major
periods of California history or prehistory?
☐ ☒ ☐ ☐
b) Have impacts that are individually limited, but
cumulatively considerable? (“Cumulatively
considerable” means that the incremental effects of a
project are considerable when viewed in connection
with the effects of past projects, the effects of other current projects, and the effects of probable future
projects)?
☐ ☒ ☐ ☐
c) Have environmental effects that would cause
substantial adverse effects on human beings, either
directly or indirectly?
☐ ☐ ☒ ☐
Discussion
a) Less-than-Significant Impact with Mitigation. The Project would not substantially degrade the quality of the environment, reduce fish or wildlife populations, or eliminate important examples of major periods of California history or pre-history. As noted in the Cultural Resources section, there are no features onsite of prehistoric or historic significance. Thus, the Project would not eliminate important examples of the major periods of California history or prehistory and would not significantly impact any resource that would qualify for listing as eligible on the CRHR. As noted in the Biological Resources section, implementation of Mitigation Measures BIO-1 and BIO2 would reduce impacts to special status animal species. Therefore, the Project would result in a less-than-significant impact with mitigation. b) Less-than-Significant Impact with Mitigation. According to the City of Napa, there is one proposed roadwork project within one mile of the project site. This includes the Coombsville Road Roadway Rehabilitation Project (Pascale Place to City Limits, located approximately 0.4 miles to the east of the Project site). The Project is proposed to include pavement and striping work, and possible concrete and storm drain improvements.

As described in the preceding sections of this Initial Study, the Project would result in no impacts to agricultural and forest resources, land use and land use planning, mineral resources, population and housing, recreation, or wildfire. Because the Project would have no impact for these topic areas, there is no potential for the Project to have cumulatively considerable impacts.

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Draft Initial Study/Mitigated Negative Declaration July 2025 As described in the preceding sections of this Initial Study, the Project would result in less than significant impacts to aesthetics, energy, geology and soils, GHG emissions, hazards and hazardous materials, hydrology and water quality, noise, public services, transportation, and utility and service systems. The Project is consistent with the land use and zoning designations for the parcel and would not conflict with applicable land use policies or regulations.

As noted in the Air Quality section, the BAAQMD CEQA Air Quality Guidelines recommend that cumulative air quality effects from criteria air pollutants also be addressed by comparison to project-level significance thresholds. These thresholds were developed to identify a cumulatively considerable contribution to a significant regional air quality impact. As disclosed in the Air Quality section, the Project-related construction emissions would be below BAAQMD’s average daily significance thresholds. The incorporation of mitigation measures for fugitive dust during construction of the Project would ensure air quality impacts would be less than significant with mitigation. Therefore, the Project would not result in a cumulatively considerable net increase of emissions of criteria air pollutants and precursors and there is no potential for the Project to have cumulatively considerable air quality impacts.

As noted in the Biological Resources section, the Project site is highly disturbed, making it unsuitable for special-status plants to occur. In addition, the Project site lacks the hydrological and topographical conditions to support special-status plant species. The Project site does not contain any wetlands or other natural aquatic habitat features, such as stream channels or drainages. Mitigation measures for special status animal species (preconstruction surveys for nesting birds and bats) would reduce impacts to a less than significant level. Therefore, there is no potential for the Project to have cumulatively considerable biological resource impacts.

As noted in the Cultural Resources and Tribal Cultural Resources sections, no historical resources exist on the Project site and the Project area exhibits a low level of sensitivity for cultural resources, paleontological resources, or traces of early Native American activity. Due to a lack of identified cultural resources, the Project would result in a lessthan-significant impact with mitigation. Therefore, there is no potential for the Project to have cumulatively considerable cultural or tribal cultural resource impacts.

Considering the factors addressed above, the Project would not have a cumulatively considerable impact on any of the environmental factors evaluated in this Initial Study with mitigation incorporated. Therefore, cumulative impacts would be less than significant with mitigation incorporated and the Project would not result in cumulatively considerable impacts when viewed in connection with the effects of past projects, the effects of other current projects, and the effects of probable future projects. c) Less-than-Significant Impact. As described in the preceding sections of this Initial Study, the Project would not result in impacts that would result in substantial adverse

ENVIRONMENTAL CHECKLIST
Napa Hidden Glen Remediation Project 86 RCH Group
Draft Initial Study/Mitigated Negative Declaration July 2025 effects on human beings, either directly or indirectly. Therefore, the Project would result in a less-than-significant impact with mitigation.
_________________________

APPENDIX A

SITE PHOTOS

City of Napa
Hidden Glen Remediation
Site Photos
Prepared by:

City of Napa Utilities Department
for
CalRecycle Legacy Disposal Abatement
Partial Grant Program Application
October 16, 2024
CITY 01=
NAPA

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 1 – Aerial View of Project Site (north is top of photo)

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 2 – Project Site (looking north towards house on Lot 13) Photo 3 – Project Site (looking east towards quarry cliffs)

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 4 – Project Site (looking south towards house on Lot 6) Photo 5 – Project Site (looking south-west towards Lots 7 & 8)

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 6 – Project Site (looking west with house on Lot 6 to the left) Photo 7 – Project Site (looking west with house on Lot 9 to the right)

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 8 – Project Site (looking north-west towards Lots 9 & 10) Photo 9 – Methane Gas Monitoring Well #2 Along Fence with Lot 7 (looking south-west)

City Hall: 955 School Street, Napa CA 94559  Mailing Address: P.O. Box 660, Napa CA 94559  (707) 257-9500  www.cityofnapa.org Photo 10 – Project Site (looking south-west towards Lot 8 w/ Pascal Place in upper right)
Photo 11 – Project Site Along Pascal Place (looking south)

APPENDIX B

REMEDIAL ACTION PLAN (RAP)

Remedial Action Plan
Hidden Glen Dump
Coombsville Road
Napa, California
SWIS No. 28-AA-0028
Napa County Local Enforcement Agency
1195 Third Street, Suite 210 I Napa, California 94559
October 16, 2024 | Project No. 109558001
Geotechnical | Environmental | Construction Inspection & Testing | Forensic Engineering & Expert Witness Geophysics | Engineering Geology | Laboratory Testing | Industrial Hygiene | Occupational Safety | Air Quality | GIS Geotechnlcal & Environmental Sciences Consultants
, .. I

5710 Ruffin Road | San Diego, California 92123 | p. 858.576.1000 | www.ninyoandmoore.com Remedial Action Plan
Hidden Glen Dump
Coombsville Road
Napa, California
SWIS No. 28-AA-0028
Mr. Peter Ex, REHS
Napa County Local Enforcement Agency
1195 Third Street, Suite 210 I Napa, California 94559
October 16, 2024 | Project No. 109558001
Nathan Diem
Senior Geologist
Beth Abramson-Beck, PG
Project Engineer
NDD/BAB/mp
J(ln90&/(I.Oore
G8ollcllnlCII & Envlronmllltal Sclt11Ct1 Con1ulllntl

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 i

CONTENTS
1 INTRODUCTION 1
2 BACKGROUND 2
3 SITE DESCRIPTION 4
4 OWNERSHIP 4
5 PHYSICAL SETTING 4

5.1 Topography 5

5.2 Regional and Site Geology 5

5.3 Groundwater 6
6 REMEDIAL ACTION 8

6.1 Remedial Action Objectives 8

6.2 Pre-Remedial Action Site Preparation and Notifications 9

6.3 Site Health and Safety Plan (SHSP) 9

6.4 Community Health and Safety Plan 9

6.5 Utility Clearance 10

6.6 Site Access 10

6.7 Waste Excavation 10

6.8 Waste Disposition – Reconsolidation 11

6.9 Waste Disposition – Neighboring Property
Waste Reconsolidation Option 11

6.10 Waste Disposition – Offsite Disposal 12

6.11 Temporary Stockpiling and Management 12

6.11.1 Stockpile Sampling and Characterization for Offsite Disposal 12

6.12 Imported Fill Soil 13

6.13 Best Management Practices

6.14 Excavation Sampling

6.15 Field Documentation

6.16 Dust Control and Air Monitoring Plan

6.17 Site Restoration
14 14
14 14
15

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 ii 7 LIMITATIONS 15
8 REFERENCES 17

FIGURES
Figure 1 – Site Location
Figure 2 – Site Plan
Figure 3 - Planned Remedial Action
Figure 4 - Planned Remedial Action – Neighboring Waste Grading Alternative

APPENDICES
A – Closed Disposal Site Inspection Report Hidden Glen Dump 4/23/24 B – Architect Grading Design Plans
C – 2018 Langan Soil Sample Results
D - Site Specific Health and Safety Plan
E - Community Health and Safety Plan
F – Alternative Acceptance of Neighboring Property Waste Soil Grading Plans G – DTSC Information Advisory – Clean Imported Fill

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 1 1 INTRODUCTION
Ninyo & Moore is pleased to submit this Remedial Action Plan (RAP) for a portion of the Hidden Glen Dump, (dump) located near the intersection of Pascale Place and Glory Court in Napa, California (Figure 1). The waste disposal site (WDS) is listed as “Hidden Glen Dump” in the CalRecycle Solid Waste Information System (SWIS) database and assigned SWIS No. 28-AA0028. According to the database, the dump is listed as an unpermitted, closed, solid waste disposal site (WDS). The City-owned property referred to as “Parcel A” corresponds to a 2.18-acre area and is assigned Napa County Assessor Parcel Number (APN) 045-411-022-000 (Figure 2).

According to the SWIS database, the waste type is indicated as “There are no Waste Types” (likely undocumented/unknown). Information pertaining to “closure type, volume Unit Type, Remaining Capacity, Total Acreage, Disposal Acreage, permitted depth and elevation and depth are not available. The WDS is inspected quarterly by the County of Napa Environmental Health, Solid Waste Local Enforcement Agency (LEA). The latest inspection report, dated April 23, 2024, states “There are no Violations and No Areas of Concern (Appendix A). The April inspection report noted soil and debris was illegally disposed of on the west side of the property from an adjacent property, Lot 9.

On November 26, 2019 the LEA issued a Notice of Comply to the City which required submittal of a Work Plan to ensure that State Minimum Standards are addressed at the City owned property and in compliance with Title 27 of the --- Code of regulations. This RAP is being submitted to comply with the notice.

This RAP pertains to the portion of the dump that is owned by the City of Napa (City) and includes conducting the proposed remedial action activities on City-owned property. The planned remedial action for the City-owned property consists of waste excavation at locations and to depths to meet state minimal standards for waste disposal sites and be protective of human health, and on-site reconsolidation of the removed wastes as generally shown on Figure 3. Detailed remediation plans are included in Appendix B. The planned remedial activities will be conducted on City-owned property; however, the City may additionally remove some wastes in the areas of adjacent residential properties to provide a sloped transition of the soil cover across property lines referred to as “feathering”. This RAP also includes the possibility of accepting waste soil from adjacent properties and reconsolidating and covering on City property as shown in Appendix F.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 2 2 BACKGROUND
The background information contained in this section focuses on the previous Closure Plans for the dump, reports documenting closure activities and related regulatory agency correspondence, and subsurface investigations at adjacent residences. The background information was obtained from publicly available documents in the CalRecycle SWIS database and pertains to wastes located outlying the capped portion of the dump that are specifically relevant to this RAP.

Initially the dump was an excavated quarry that operated into the 1940s. Reportedly, groundwater was encountered when the quarrying operations were at a depth of about 70 to 80 feet (below ground surface (bgs). Reportedly, the quarry was abandoned due to the presence of groundwater.

Sometime after quarry operations ended, the excavation was used as a general garbage dump by a private operator. Reportedly, “garbage” was dumped and then burned “and spread as a landfill.” It was stated that it was possible that “old” automobiles from a local demolition derby were also abandoned at the dump. In the early l960's, the dump reportedly was abandoned when the South County landfill became operational. The City reportedly began using the Hidden Glen Dump to dispose tree prunings and brush, along with asphalt and concrete wastes. The brush and prunings were reportedly burned “and spread.”
Several closure plans (aka remedial action plans) were previously prepared for the dump and remedial action activities were conducted to close the site. ENGEO (1988) prepared a closure plan consisting of capping the waste disposal site “in place.” In 1990, Harding Lawson Associates (HLA) (1990) prepared an addendum to the closure plan that maintained the planned “in-place capping” of the dump. In April 2000 McClaren-Hart prepared a Closure Plan for the Hidden Glen Dump (McClaren-Hart, Inc, 2000) that was generally consistent with the previous 1988 ENGEO and 1990 HLA closure plans and similarly proposing capping the waste disposal site “…in place and dedicating the site as open space as part of a planned residential development of the surrounding site.” The closure plan proposed to cap in place the dump and reportedly “…gain agency concurrence for closure, which is sought by the land owner to allow him to proceed with planned residential development of the overall 14-acre site.” Reportedly the 1990 McClaren-Hart Closure Plan report was prepared as an addendum to the 1988 Closure Plan.

In general, the McClarren-Hart Closure Plan described methods proposed to cap in place the dump and obtain regulatory agency concurrence for closure which was being sought by the land owner to allow them to proceed with the planned residential development of the overall 14-acre site, a portion of which included the dump. Post closure activities were indicated as consisting of a 5-year cap and methane monitoring program even though methane was not expected to be encountered at levels of environmental concern.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 3 In January 2002, Geotrans submitted a documentation report of the waste cap construction on behalf of the Napa Garbage Service that included as-built drawings, liner test results, compaction test results, site photographs, and a description of the work performed. It was stated that the “landfill” cap was constructed in accordance with the design specifications and closure plan requirements.

Geotrans stated that the closure was performed with oversight and direction from the Water Board, CIWMB and the LEA and in general accordance with the April 6, 2000 closure plan prepared by McLaren/Hart, Inc. titled, “Closure Plan, Hidden Glen Landfill, Napa, California” as amended by the December 6, 2000 letter prepared by Geotrans titled, “Addendum to April 6, 2000 Hidden Glenn Landfill Closure Plan, Napa, California.” GeoTrans stated that the construction documentation report indicated that “landfill closure” included importing and stockpiling clean fill material for use as foundation fill and protective soil cover; clearing and grubbing the waste area surface; placing and grading foundation fill soils over the waste materials; installing a cap system consisting of a geosynthetic clay liner (GCL), 80-mil high density polyethylene (HDPE ) layer, and geocomposite drainage layer; placing protective soils and top soil over the cap; placing a hydroseed mixture on the topsoil; and installing surface water drainage and erosion control features.

Beginning in September 2018, Langan conducted subsurface site investigations (drilling and sampling) of residential properties at Lots 6, 7, 8, 9 and 10, outlying the capped portion of the Hidden Glen Dump and on the flag section of the City owned property. Langan indicated that the purpose of their investigations was to collect “subsurface information” to develop a plan for remedial action “to address debris impacts in shallow soil on the five lots and, if needed, on adjacent areas between the lots and the landfill footprint.” The results of their investigations indicate that the lateral extent of the waste disposal site extends beyond the area that was capped and relatively shallow wastes extended within the buffer zone onto the residential properties. In addition, waste was observed within the flag ship area (frontage along Pascale Place, Figure 2).

These wastes contain elevated lead concentrations at some locations. Soil sample results and figures are included in Appendix C (Langan, 2019a,b,c,d,e).

The Langan reports were provided to the LEA and in response the LEA issued a Notice to Comply letter to the City on November 26, 2019. The Notice to Comply letter required submittal of a Work Plan to ensure that State Minimum Standards are addressed at the City owned property and in compliance with Title 27 of the --- Code of regulations. This RAP is being submitted to comply with the notice.

On June 29, 2020, the LEA issued a letter to the City of Napa requiring submittal of a workplan to ensure that State Minimum Standards are addressed at the City-owned parcel and in compliance with Title 27 of the California Code of Regulations. To comply with State Minimal Standards, the

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 4 letter requires the City to remove and/or cover spillover waste along the flag section and the buffer zone (Figure 2). The LEA describes two options to address waste in the flag section and the buffer zone; option 1 full waste removal and option 2 leaving the waste in-place and capping. This RAP proposes to excavate, reconsolidate waste on site, and cap waste with a minimum of two feet of clean soil.
3 SITE DESCRIPTION
The site as it pertains to the RAP is the City-owned Parcel A consisting of the capped portion of the dump and the area between the capped area and the adjacent properties referred to as the buffer zone (Figure 2). The dump is located in a residential setting with wastes occurring at the previously capped portion of the dump, buffer zone and at adjacent residential properties downslope to the north, west, and south. Nearly vertical quarry walls along the east perimeter of the cap section contain the waste to the east. Adjacent residential properties are not separated by a road or other features. A cemetery is located across Pascale Place to the west.

The dump has three relatively recently constructed Landfill Gas (LFG) monitoring wells referred to as MW-1 through MW-3 (Figure 2). The wells were constructed in December 2020 and are monitored quarterly. The wells are dual and triple completions; MW-1 and MW-2 are constructed with screened intervals at 5 to 10 feet, 15 to 20 feet and 25 to 35 feet and MW-3 is constructed with two screened intervals at 5 to 10 feet and 15 to 20 feet. 4 OWNERSHIP
The following information for the Hidden Glen Dump was obtained from the SWIS database:

Site: Hidden Glen Dump
Coombsville Road
Napa, California
(SWIS No. 28-AA-0028)
GIS Coordinates Latitude: 38.2977 Longitude: -122.2679
Land Owner(s) City of Napa
955 School Street
Napa, California 94559
5 PHYSICAL SETTING
The following summarizes topographic, geologic, and hydrogeologic information for the site and/or vicinity, based upon documents reviewed, as referenced and/or our visual reconnaissance of the site.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 5

5.1 Topography
The capped waste disposal area and buffer zone was observed to be relatively flat, with surface elevations reportedly ranging from approximately 120 to 130 feet MSL). On the northwest, north, and east sides are near vertical quarry walls (SCS Engineers, 2020). In general, the surface between the capped waste disposal area and Pascale Place to the west and Glory Court to the south slope downward to approximately 105 feet MSL.

5.2 Regional and Site Geology
The following is a description of the regional geology and site geology, based on early investigations, from the Closure Plan Addendum prepared by HLA.

The hills bordering the east side of Napa Valley are underlain, as is the site, by Pliocene age Sonoma Volcanics. The Sonoma Volcanics are a complex assemblage of volcanic, pyroclastic, and volcaniclastic rocks. The composition of these volcanics is highly variable and represents an accumulation of material erupted from numerous source vents. In addition, these deposits were typically deposited on irregular topographic surfaces and locally-on moderately steep slopes. As a result, the Sonoma Volcanics are commonly composed of highly lenticular or interfingered volcanic rocks of variable composition.

As observed at the site during previous investigations, several different lithologic rock types crop out on the surface, or were encountered during drilling, including: l) flow banded and brecciated rhyolite, 2) vitric tuff with lenses of perlitic rhyolite, a pyroclastic breccia and pumaceous ash flow tuff, and 3) poorly sorted lithic tuff breccia. These rocks exhibit rapid lateral variation and are gradational, such that they should be considered texturally and lithologically distinct zones within a single mappable unit.

Red-brown rhyolite crops out in the north portion of the site and occurs as blocks and small lenses (less than 10 feet thick) within dense vitric tuff in the southern portion of the site. The rhyolite is typically flow banded, although massive, flow breccia and explosion breccia textures were also observed. The matrix of the breccia consists of dense rhyolite. Overall, these rhyolite rocks are very hard, strong, and little weathered, with very little fracturing. Fractures that occur are related to cooling and are therefore random and discontinuous. The rhyolite is associated with some moderately consolidated tuff beds that typically occur near the base of the flow sequence.

A vitric tuff /pyroclastic breccia also crops out at the site and is light gray to green and generally hard and strong. This material is exposed on the west and south sides of the main quarry pit, and underlies the central portion of the pit as indicated from core samples during previous drilling

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 6 (Engeo, 1988). Texturally, it ranges from dense vitric tuff to coarse pyroclastic breccia containing pumice and volcanic blocks and bombs accumulated near vents. In the quarry pit wall, this rock contains occasional hairline fractures (less than 1/16-inch) that are locally iron stained. Fractures observed in outcrop appear to be random. In addition, fractures are very infrequent in outcrops examined outside the quarry site, suggesting that some of the fractures observed in the pit wall may be due to prior quarry activities.

Brown, poorly sorted, lithic tuff breccia is exposed on the east wall of the main quarry area. This tuff contains abundant, angular, 2 to 3 foot blocks of rhyolite and less common, non-volcanic lithic fragments set in a dense brown ash matrix. Overall, the rock is hard, strong and infrequently fractured.

Most of the rocks observed in the cores or cuttings from the borings were similar to rocks observed in outcrop. However, in one boring (MW-F) (Figure 2), a dark red-brown silty clay mudstone-like material was encountered from 31 to 37 feet and is interpreted as a possible paleosol that formed between silicic eruptions. At 179 feet, a gray, fine- grained (aphanitic) basalt was penetrated. Immediately below the basalt, at 188 feet, ground water associated with cuttings of rounded volcanic gravels, sand, silt, and clay was found. The rounded gravels suggest that the cuttings were derived from a conglomerate or partially lithified river channel deposit that disaggregated during drilling. Lenses of volcaniclastic sediments and river deposits are not uncommon in the Sonoma Volcanics (Kunkel and Upson. 1960).

5.3 Groundwater
The following is a description of hydrogeologic and groundwater conditions at the site and surrounding area based on the compilation of assessment data by HLA for the Solid Waste Assessment Test (SWAT) (HLA, 1990). Groundwater data is from the groundwater and leachate monitoring wells installed to evaluate the site conditions to prepare a site closure plan in 1988 Based on the evaluation by HLA, “…ground-water flow through these volcanic rocks could be controlled by one or a combination of hydraulic conductivity of the bedrock matrix; hydraulic conductivity of through going discrete, or interconnected fracture sets; or hydraulic conductivity of contact zones between different volcanic units.”
Flow through the matrix of rocks is controlled by the abundance and interconnection of primary pores. The rocks examined on site are generally very hard and dense, and pores that exist, such as vesicles, are not interconnected. Thus, the hydraulic conductivity of the rock matrix of these rocks is very low.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 7 Groundwater flow through hard rock could be controlled by either discrete throughgoing fractures or a network of interconnected fractures. Most fractures observed on site appear to be related to shrinkage during cooling of the volcanic rock. This type of fracture is random and restricted to individual cooling units. For example, a rhyolite flow may contain random cooling fractures that are either discontinuous within the flow or terminate at the adjacent unit that may or may not have its own set of cooling fractures. Considering the geologic setting and the field observations, the potential for either discrete, throughgoing fractures or a network of interconnected fractures appears to be low. Thus, the potential for groundwater flowing from the landfill into the bedrock and traveling into groundwater aquifers is considered low (HLA, 1990).

The volcanic rock beneath the site is extremely complex and highly variable. The irregular contact zones between different volcanic materials in the complex could conceivably be pathways for groundwater flow, particularly the top and bottom of a lava flow, which are often rubble zones developed by progressive movement during emplacement, a process referred to as auto brecciation. If the voids in the rubble are not filled during emplacement or by secondary alteration products, these zones can be permeable. In addition, some thin (less than 5 feet) interbedded lenses or beds of moderately consolidated pumaceous tuff occur locally in the pyroclastic sequence. These tuff beds appear moderately permeable and depending on the location, could behave as pathways for groundwater movement. Once groundwater gets into these zones, movement is controlled by the bedrock structure or the general strike and dip of the volcanic rocks. Some bedding plane contacts are essentially impermeable and behave as groundwater barriers. Fractures could conceivably be important locally in transmitting water from a flow or tuff unit to a permeable zone, if present (HLA, 1990).

Based on the HLA evaluation, water levels in bedrock monitoring wells associated with the site are highly variable. At the time, MW-C and MW-D are both dry (Figure 2). The water level in MW-A is at 76 feet above msl, whereas the water level in MW-F, located 400 feet northeast of MW-A, is at approximately 19 feet above msl. This variability in water levels suggests that the water-bearing zones encountered are not hydraulically connected. If these zones were in hydraulic connection, the wells on site would respond to a consistent and predictable gradient. The erratic water levels in adjacent wells further substantiates that ground-water flow beneath the site is not controlled by porous media type flow or by interconnected sets of fractures.

More recent monitoring of the three landfill gas wells at the site (MW-1 through MW-3, Figure 3) indicates that when last monitored in May 2024, groundwater was present in the shallow probe in MW-1 (total depth 10 feet bgs) at an approximate depth of 8 feet bgs. Groundwater was measured

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 8 in the 30-foot LFG probe in MW-2 at a depth of 22 feet bgs and in the 20-foot LFG probe at a depth of 16 feet bgs.

Water was reportedly encountered in boring B-2 located within wastes (Figure 2). Water reportedly was not encountered in boring of B-1; however, this boring appears to be located on a high spot on the quarry floor. The core material of Boring B-1 was moist (HLA, 1990).

More recent monitoring of the three landfill gas wells at the site (MW-1 through MW-3, Figure 2 and Figure 3) indicates that when last monitored in May of 2024, groundwater was present in the shallow probe in MW-1 (total depth 10 feet bgs) at an approximate depth of 8 feet bgs.

Groundwater was measured in the 30-foot LFG probe in MW-2 at a depth of 22 feet bgs and in the 20-foot LFG probe at a depth of 16 feet bgs.
6 REMEDIAL ACTION
The planned remedial actions for the city-owned portion of the dump are consistent with restoration as an open-space (e.g., absence of buildings, playing fields, parking areas, equipment, etc.). The execution of the remedial action activities will be conducted in accordance with this LEA approved RAP. The remedial action will be performed by California-licensed contractors and a California licensed professional geologist, certified engineering geologist, or registered engineer or equivalent or under their direction. The following sections present the planned remedial action implementation. Remedial activities will be conducted in accordance with applicable rules and regulations imposed by the LEA, CalRecycle and the City of Napa.

6.1 Remedial Action Objectives
Remedial action objectives (RAOs) have been established for the dump to ensure the planned remedial actions:
1) are protective to human health and the environment,
2) meet applicable state minimum standards with respect to waste disposal sites (e.g., no exposed wastes, wastes where present will be adequately covered, etc.), 3) takes into account the types and locations of disposed wastes and future use of the site as open space,
4) is satisfactory to the LEA, CalRecycle and the City of Napa.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 9

6.2 Pre-Remedial Action Site Preparation and Notifications Site preparation prior to implementing remedial action will include but not be limited to the following:
• Notify the LEA and CalRecycle of the proposed remedial action once a schedule has been established.
• The City will notify the adjacent property owners and their representatives of the planned remedial action.
• Delineate the work area boundaries including the “buffer zone” boundaries and the adjacent property lines.
• Install erosion control and Best Management Practices (BMPs) in accordance with the project Stormwater Pollution Prevention Plan (SWPPP).
• Identify and prepare site ingress and egress.

6.3 Site Health and Safety Plan (SHSP)
A site-specific worker health and safety plan (SHSP) was prepared by Ninyo & Moore under the direction of, and approved by a Certified Industrial Hygienist (CIH) (Appendix D). The SHSP will be used during the RAP implementation. The plan describes the required specific training and monitoring requirements to ensure workers are adequately protected, identified the potential chemical and physical hazards that may be encountered during the field activities and will be prepared in general compliance with Occupational Safety and Health Administration (OSHA) requirements. The plan addresses field procedures, personal protective equipment, anticipated contaminants, and established action levels for exposure to contaminants and contingency plans for emergencies that may arise during the fieldwork.

6.4 Community Health and Safety Plan
Due to the presence of an adjacent residential community, a CHSP was prepared for the remedial action under the direction of, and signed by a CIH (Appendix E). The primary purpose of the CHSP is to promote a safe and healthy environment for the public by reducing community exposures to potential hazards and nuisances from site/clean closure activities, and promoting community awareness of the planned site closure activities. The plan is intended to protect the public and surrounding properties from potential health and environmental hazards during the planned remedial activities. The CHSP addresses field procedures, anticipated contaminants, established action levels for exposure to contaminants, and contingency plans for emergencies that may arise during the fieldwork.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 10

6.5 Utility Clearance
Subsurface utilities are not expected to be present in the remedial excavation areas based on the current open space use of the site. However, prior to commencing excavation activities, public utility locator Underground Service Alert (USA) will be notified of the planned project a minimum of 48 hours before field activities start so that they can contact representatives of utility companies in the area. The planned project area will be clearly marked with white paint or surveyors flagging as required by USA.

6.6 Site Access
Access to the site is limited due to the absence of access roads, presence of private properties generally surrounding the site and presence of steep slopes/near vertical quarry walls. The site is only accessible via Pascale Place by traversing the western portion of the City of Napa-owned Lot A (Figure 3). Temporary construction fencing will be placed at the site entrance along Pascale Place (Appendix B) and access to the site will be arranged in advance by the City of Napa.

6.7 Waste Excavation
The remedial action for the site generally consists of excavating and removing wastes in the buffer zone (Figures 2 and 3) (e.g., areas between the capped portion of the dump and the adjacent residential properties/lots) and reconsolidating these wastes onsite at the northern portion of the capped dump (Figure 3). As shown in the grading plans in Appendix B, and on Figure 3, wastes will be excavated to bedrock where feasible, to depths of approximately 10 to 20 inches. The depth of excavation will be reduced if bedrock is encountered at shallower depths. Conversely, the depth of excavation may extend beyond 20 inches if wastes are deeper to reach bedrock or the excavation may terminate in wastes in which case the wastes will be covered with 2 feet of clean imported soil. Where waste removal may not be possible due to access, stability and/or other restrictions, wastes remaining in place will be covered with two 2 feet of clean imported soil to meet state minimum standards. Soil/waste from the flag section of Parcel A (frontage along Pascale Place, Figure 3) will be removed down to bedrock.

The lateral extent of the waste removal will be based on agreements with the adjacent property owners. At a minimum, waste will be removed within the buffer zone and extend to the adjacent property boundaries. Under this option, no waste will be removed from the adjacent properties and a small amount of waste may remain at the property line due to soil sloughing. However, if an adjacent property owner agrees, waste removal will “feather” from the buffer zone across the property line. In accordance with the grading plans, (Appendix B), wastes will be removed and “feathered” across the property lines of Lots 6, 7, 8, 9, and 10 a distance of approximately 1 to

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 11 5 feet beyond the property lines. In addition, soil and waste that was illegally dumped adjacent to Lot 9 will be removed to bedrock, as possible (Appendix B, Section Cut 6/4.2). Following the completion of waste removal, final grading will consist of backfilling with clean import soil to provide positive drainage. In addition, one foot of clean imported soil will be placed on top of the existing cap area (Figure 3, Appendix B). Final grading plans and drainage details are provided in Appendix B.

6.8 Waste Disposition – Reconsolidation
Based on the grading plans in Appendix B, approximately 670 cubic yards (cy) of waste including soil, waste, and grass and roots from grading operations will be excavated and reconsolidated on site. The proposed reconsolidation area on Parcel A is shown on Figure 3 and reconsolidation grading and cover plans are provided on the plans in Appendix B. The excavated waste will be moved to the approved reconsolidation location by the excavation contractor and will be transported in such a manner as to minimize the potential of spillage and creation of dust during transportation. Excavated waste may be first placed in temporary stockpiles near the excavation areas prior to being placed in the reconsolidation area. Temporary stockpiles will be managed in accordance with Section 6.11. Reconsolidated waste will be placed directly on top of the existing waste cap in the reconsolidation area, thereby not intruding into, or disturbing the existing cap, and covered daily with Visqueen plastic or equivalent. The final cover of the reconsolidated waste will consist of at least 2 feet of imported clean soils. Previous dump closure plans and State Regulations do not preclude onsite reconsolidation on top of the current cap.

6.9 Waste Disposition – Neighboring Property Waste Reconsolidation Option
The City is in discussions with the neighboring property owners regarding waste removal from their properties and reconsolidation of the waste on the City property. If this remedial action is agreed upon by the city and property owner(s), waste from the neighboring properties will be placed in temporary stockpiles in designated areas on the City property by the neighboring property owner’s contractor. The property owner contractor(s) will need to meet the requirements specified in this plan including, but not limited to appropriate licensing to handle wastes, adhering to the site and community health and safety plans, etc. Temporary stockpiles will be managed in accordance with Section 6.11 of this plan. The stockpiles will be moved to the site reconsolidation area shown in Figure 4 by the City’s contractor and graded in accordance with the grading plans in Appendix F. Based on the grading plans, if property owners of Lots 6 through 8 and Lot 10 were to select this option, then as estimated by others, approximately 2,753 cy of waste may be

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 12 reconsolidated from the neighboring residences and from the City owned property. Similar to waste reconsolidation from the City’s property described in Section 6.8, reconsolidated waste from the neighboring properties will be placed directly on top of the existing waste cap in the reconsolidation area and covered with a minimum of two feet of clean imported soil.

6.10 Waste Disposition – Offsite Disposal
As an alternative and at the discretion of the City, excavated waste may be temporally stockpiled, sampled for waste characterization, and transported to an offsite waste facility as described in sections below. The grading plan for this alternative is shown on drawing 5.3 in Appendix B.

6.11 Temporary Stockpiling and Management
Waste may be temporarily stockpiled prior placing waste in the reconsolidation area and/or for offsite waste disposal. As applicable, a staging area and temporary stockpiles will be managed by the Contractor in accordance with this document, construction specifications, and the project SWPPP. Temporary stockpiled waste at the site be managed as follows:
• Place the excavated/stockpiled waste onto 10-millimeter (mil) or thicker visqueen plastic sheeting.
• Temporary stockpiles will be sprayed or misted with water to minimize dust emissions during stockpiling, if necessary.
• Temporary stockpiles will be securely covered daily with a 6-mil or thicker visqueen plastic sheeting to minimize runoff from rain.
• Temporary stockpiles will be configured in such a manner that surface water runoff, if present, from the stockpile does not carry stockpiled materials beyond the stockpile area.

6.11.1 Stockpile Sampling and Characterization for Offsite Disposal Stockpiles intended for offsite disposal will be sampled by running a random number generator to obtain sample locations and depths. If the sampling depth is relatively shallow, the sample will be collected by coring the laboratory-supplied container directly into the material to be sampled. If the sample depth is greater, and depending on the actual volume of the stockpile, excavation equipment and/or hand auger equipment will be used to obtain samples. If excavation equipment is used, the sample will be similarly collected by coring the sample jar directly into the material to be sampled. If hand auger equipment is used then the sample in the auger will be transferred to a laboratory-supplied jar. Analytical testing for wastes to be disposed of offsite will be based on the accepting disposal facility(s)

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 13 requirements. The contractor should assume the wastes may be tested for chemicals of concern including the following:
• California Title 22 metals; samples containing one or more metal concentrations less than the California Total Threshold Limit Concentrations (TTLCs) but greater than 10-times the California Soluble Threshold Limit Concentrations (STLCs) will be additionally analyzed for soluble metal concentrations by the California Waste Extraction Test (WET) method to profile the waste as either California Class I hazardous or California Class II non-hazardous. Samples containing one or more metal concentrations exceeding 20-times the Federal Toxicity Characteristics Leaching Procedure (TCLP) will be additionally analyzed for soluble metal concentrations by the Federal TCLP to classify the waste as either RCRA or non-RCRA hazardous waste.
• Total Petroleum Hydrocarbon compounds (e.g. TPHgas, TPHdiesesl and TPHmotor oil).

Additional analysis may be required by the disposal facility. In general, the number of discrete samples required is listed below. The actual number of samples to be collected and analyzed will depend on the receiving facilities requirements.
• Stockpiles 100 cy or less -a minimum of four discrete samples will be collected, one from each quarter of the stockpile.
• Stockpile from 101-500 cy - a minimum of one sample from each 25 cy, or portion thereof, will be collected (e.g., a 130-cy stockpile would require six samples). • Stockpile over 500 cy - sample as per a 500 cy stockpile and collect an additional sample for each additional 500 cy, or portion thereof.

6.12 Imported Fill Soil
Clean imported fill soil to be used to cover/cap waste will be sampled and the analytical data, soil classification, and the origin/location of the import soil will be provided to the LEA for approval prior to use onsite. Import fill soil sampling methodology and analysis will follow the California Department of Toxic Substance Control (DTSC) 2001 Information Advisory (for) Clean Imported Fill guidelines (Appendix E). According to DTSC’s guidelines, the number of soil samples is based on the volume of imported fill and summarized below.
• One sample per every 250 cy for up to 1,000 cy.
• Four samples for the first 1,000 cy plus one extra sample per each additional 500 cy. • For a volume of soil greater than 5,000 cy, 12 samples collected for the first 5,000 cy, and one extra sample for every additional 1,000 cy.

The City of Napa estimated that approximately 4,400 cy of soil will be imported which would require approximately nine discrete soil samples for analysis prior to importing to the site. Only

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 14 discrete samples will be collected because of the potential dilution of contaminants. The samples will be analyzed for Constituents of Potential Concern (COPC) based on the source of the import soil in accordance with the DTSC’s guidelines. The sample results will be compared to DTSC Screening Levels and United States Environmental Protection Agency (EPA) Regional Screening Levels for comparison to human health protection evaluation.

6.13 Best Management Practices
The Contractor shall implement BMPs associated with the site SWPPP to protect the temporary stockpiles from erosion and storm water run-on and runoff. The BMPs include, but are not limited to, the following:
• Erosion control
• Storm water drainage control
• Secondary containment (as applicable)
• Fugitive emission control of dust and/or vapors
• Spill prevention
• Additional BMPs specified in the project SWPPP

6.14 Excavation Sampling
Excavation confirmation sampling is not included in this RAP. The purpose of the excavation is to remove waste within the buffer zone to bedrock and/or cap waste with two feet of clean imported soil so that no waste is exposed at the site. The City of Napa is not proposing clean closure of the dump; therefore, excavation confirmation sampling is not required.

6.15 Field Documentation
Field logs will be kept to document the field activities. Photographs will be taken to document the remedial action activities at active waste removal locations, to verify adequacy of reconsolidated material, placement of cap, temporary “waste” stockpiles and disposed waste removal (as applicable), and to generally document the remedial activities. The photographs will serve to complement information entered in the field activity logs.

6.16 Dust Control and Air Monitoring Plan
Air monitoring and dust control onsite will comply with the SHSP and CHSP (Appendix D and E).

Dust control will include dust suppression activities, such as lightly spraying or misting at active

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 15 backhoe/track hoe excavation areas and reducing vehicle speed onsite. If waste is temporarily stockpiled for offsite disposal, dust suppression activities will include light spraying or misting the stockpiled materials, covering stockpiles, and minimizing the waste drop height from the excavator’s bucket onto the stockpile or into the transport trucks. Prior to conducting the removal activities, the prevailing wind direction will be determined by obtaining prevailing wind direction information prior to and during field activities.

Per the CHSP, perimeter dust monitoring will be conducted using Thermo DataRAM particulate monitors (pDRs) (or equivalent) to monitor the upwind and downwind particulate levels of the site.

The particulate monitors continuously monitor and record the real-time concentration and median particle size of airborne dust, smoke, mist, and fumes. Personnel will monitor dust during excavation activities. Air monitoring details and action levels are provided in Section 8 of the SHSP (Appendix D) and Section 6 in the CHSP (Appendix E).

6.17 Site Restoration
Site restoration as an open space area will be consistent with the grading plans included in Appendix B. The disturbed soil within capped area with be covered with an additional one foot of clean imported soil and seeded with native grasses. Final restoration will provide positive drainage for the site.
7 LIMITATIONS
The environmental services described in this report have been conducted in general accordance with current regulatory guidelines and the standard-of-care exercised by environmental consultants performing similar work in the project area. No warranty, expressed or implied, is made regarding the professional opinions presented in this report. Variations in Site conditions may exist and conditions not observed or described in this report may be encountered during subsequent activities. Please also note that this study did not include an evaluation of geotechnical conditions or potential geologic hazards.

Ninyo & Moore's opinions and recommendations regarding environmental conditions, as presented in this report, are based on limited subsurface assessment and chemical analysis.

Further assessment of potential adverse environmental impacts from past on-site and/or nearby use of hazardous materials may be accomplished by a more comprehensive assessment. The samples collected and used for testing, and the observations made, are believed to be representative of the area(s) evaluated; however, conditions can vary significantly between

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 16 sampling locations. Variations in soil and/or groundwater conditions will exist beyond the points explored in this evaluation.

The environmental interpretations and opinions contained in this report are based on the results of laboratory tests and analyses intended to detect the presence and concentration of specific chemical or physical constituents in samples collected from the subject site. The testing and analyses have been conducted by an independent laboratory which is certified by the State of California to conduct such tests. Ninyo & Moore has no involvement in, or control over, such testing and analysis. Ninyo & Moore, therefore, disclaims responsibility for any inaccuracy in such laboratory results.

Our conclusions, recommendations, and opinions are based on an analysis of the observed Site conditions. It should be understood that the conditions of a site could change with time as a result of natural processes or human activities at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires any additional information, or has questions regarding content, interpretations presented, or completeness of this document.

This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

Ninyo & Moore | Hidden Glen Dump, Coombsville Road, Napa, California | 109558001 | October 16, 2024 17 8 REFERENCES
Engeo, 1988, Geotechnical Exploration, Hidden Glenn – Fennell Property, Napa, California: dated March 2.

Kunkel, F., and Upson, 1960, Geology and Groundwater in the Napa and Sonoma Valley areas.

U.S.G.S. Water Supply Paper 1495.

Langan, 2019a, Field Investigation – Former Hidden Glen Landfill, Lot-6 Glory Court, Napa, California: dated April 29.

Langan, 2019b, Field Investigation – Former Hidden Glen Landfill, Lot-9-Pascal Place, Napa, California: dated April 29.

Langan, 2019c, Field Investigation – Former Hidden Glen Landfill, Lot 7 and 8- Glory Court and Pascal Place, Napa, California: dated April 29.

Langan, 2019d, Field Investigation – Former Hidden Glen Landfill, Lot 10-Pascal Place, Napa, California: dated April 29.

Langan, 2019e, Field Investigation – Former Hidden Glen Landfill, Lot A-Pascal Place, Napa, California: dated April 29.

McClaren-Hart, Inc, 2000, Closure Plan Hidden Glen Landfill, Napa, California: dated April 6.

SCS Engineers, 2020, Property Management Plan for City-Owned Parcel (APN 045-411-022- 000), Investigation and Clean-Up of Closed Hidden Glen Landfill, Napa, California: dated March 2.