Table of Contents
Section1 ONE Introduction 1-1
Section2 TWO Purpose of and Need for Action 2-1
Section3 THREE Alternatives 3-1
3.1 Alternatives Not Carried Forward 3-1
3.1.1 Acquisition and Relocation of the Mobile Home Parks 3-1
3.1.2 Partial Acquisition of Mobile Homes 3-1
3.2 Alternative 1: No Action 3-2
3.3 Proposed Action Alternative: Construction of a Floodwall 3-2
3.3.1 Floodwall 3-2
3.3.2 Entrance Closure Structures 3-3
3.3.3 Interior Storm Drainage Facilities 3-4
3.3.4 Sewer Rehabilitation 3-4
3.3.5 Construction Access and Staging 3-4
3.4 Alternative 3: Mobile Home Elevations 3-5
3.5 Summary of Alternatives, Impacts, and Mitigations 3-6
Section4 FOUR Affected Environment, Impacts, and Mitigation 4-1
4.1 Biological Resources 4-1
4.1.1 Vegetation and Wildlife 4-1
4.1.2 Special Status Species 4-2
4.1.3 Alternative 1: No Action 4-23
4.1.4 Proposed Action Alternative: Construction of a Floodwall 4-24
4.1.5 Alternative 3: Mobile Home Elevations 4-25
4.2 Geology and Soils 4-25
4.2.1 Alternative 1: No Action 4-26
4.2.2 Proposed Action Alternative: Construction of a Floodwall 4-26
4.2.3 Alternative 3: Mobile Home Elevations 4-26
4.3 Water Resources 4-26
4.3.1 Alternative 1: No Action 4-27
4.3.2 Proposed Action Alternative: Construction of a Floodwall 4-27
4.3.3 Alternative 3: Mobile Home Elevations 4-29
4.3.4 Executive Order 11988: Floodplain Management 4-29
4.3.5 Executive Order 11990: Protection of Wetlands 4-30
4.4 Cultural Resources 4-31
4.4.1 Alternative 1: No Action 4-31
4.4.2 Proposed Action Alternative: Construction of a Floodwall 4-31
4.4.3 Alternative 3: Mobile Home Elevations 4-32
4.5 Socioeconomics and Safety 4-32
4.5.1 Alternative 1: No Action 4-33
4.5.2 Proposed Action Alternative: Construction of a Floodwall 4-33
4.5.3 Alternative 3: Mobile Home Elevations 4-33
4.5.4 Executive Order 12699: Seismic Safety 4-34
4.5.5 Executive Order 12898: Environmental Justice 4-34
4.6 Land Use and Zoning 4-35
4.6.1 Alternative 1: No Action 4-36
4.6.2 Proposed Action Alternative: Construction of a Floodwall 4-36
4.6.3 Alternative 3: Mobile Home Elevations 4-37
4.7 Public Services and Utilities 4-37
4.7.1 Alternative 1: No Action 4-37
4.7.2 Proposed Action Alternative: Construction of a Floodwall 4-37
4.7.3 Alternative 3: Mobile Home Elevations 4-38
4.8 Air Quality 4-38
4.8.1 Alternative 1: No Action 4-38
4.8.2 Proposed Action Alternative: Construction of a Floodwall 4-38
4.8.3 Alternative 3: Mobile Home Elevations 4-39
4.9 Noise 4-39
4.9.1 Alternative 1: No Action 4-39
4.9.2 Proposed Action Alternative: Construction of a Floodwall 4-39
4.9.3 Alternative 3: Mobile Home Elevations 4-40
4.10 Transportation 4-41
4.10.1 Alternative 1: No Action 4-41
4.10.2 Proposed Action Alternative: Construction of a Floodwall 4-41
4.10.3 Alternative 3: Mobile Home Elevations 4-41
4.11 Visual Resources 4-42
4.11.1 Alternative 1: No Action 4-42
4.11.2 Proposed Action Alternative: Construction of a Floodwall 4-42
4.11.3 Alternative 3: Mobile Home Elevations 4-42
4.12 Cumulative Impacts 4-42
Section5 FIVE Consultation and Permit Requirements 5-1
Section6 SIX References 6-1
Section7 SEVEN List of Preparers 7-1
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List of Tables, Figures, and Appendices
List of Tables
1 Summary of Impacts and Mitigations
2 Special Status Species That Potentially Occur in the Project Vicinity
3 Comparison of Environmental Justice Indicators
List of Figures
1 Project Vicinity
2 Project Area
3 100-Year Floodplain Area: Rancho de Napa and Gateway Mobile Home Parks
4 Proposed Action Alternative: Floodwall Site Plan
5 Alternative 3: Mobile Home Elevations
6 Photographs of Proposed Floodwall Alignment (South and West)
7 Photographs of Proposed Floodwall Alignment (North and East)
8 Photographs of Mobile Home Parks Entrances
List of Appendices
A U.S. Fish and Wildlife Service Tier 1 Concurrence Letter
B National Marine Fisheries Service Letter
C Federal Emergency Management Agency CLOMR Letter
D U.S. Army Corps of Engineers Letter
E State Historic Preservation Officer Letter
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List of Acronyms
List of Acronyms
APE / Area of Potential EffectBAAQMD / Bay Area Air Quality Management District
CCC / Central California Coast (steelhead)
CFR / Code of Federal Regulations
cfs / cubic feet per second
CLOMR / Conditional Letter of Map Revision
CMU / cellular masonry unit
dBA / decibels A-weighted
EA / Environmental Assessment
EO / Executive Order
ESU / Evolutionarily Significant Unit
FEMA / Federal Emergency Management Agency
FIRM / Flood Insurance Rate Map
HMGP / Hazard Mitigation Grant Program
NAHC / Native American Heritage Commission
NEPA / National Environmental Policy Act of 1969
NFIP / National Flood Insurance Program
NHPA / National Historic Preservation Act
NMFS / National Marine Fisheries Service
NRHP / National Register of Historic Places
NWIC / Northwest Information Center
OES / California Governor’s Office of Emergency Services
PM-10 / particulate matter with an aerodynamic diameter of 10 microns or less
SHPO / State Historic Preservation Officer
SR 29 / State Route 29
URS / URS Corporation
USACE / U.S. Army Corps of Engineers
USFWS / U.S. Fish and Wildlife Service
USGS / U.S. Geological Survey
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SECTIONFOUR Affected Environment, Impacts, and Mitigation
1. Section1 ONE Introduction
The Town of Yountville, California, has applied, through the California Governor’s Office of Emergency Services (OES), to the Federal Emergency Management Agency (FEMA) for assistance with the construction of a flood barrier to protect two mobile home parks from periodic flooding. FEMA is proposing to provide assistance for this project through the Hazard Mitigation Grant Program (HMGP) under Presidential Disaster Declaration FEMA-DR-1044-CA. This Environmental Assessment (EA) has been prepared according to the requirements of the National Environmental Policy Act of 1969 (NEPA), the Council on Environmental Quality’s regulations for implementing NEPA (Title 40 of the Code of Federal Regulations [CFR] Parts 1500-1508), and FEMA’s implementing regulations (Title 44 CFR Part 10).
The Yountville Mobile Home Park Flood Barrier Project (Project) would surround the Rancho de Napa and Gateway Mobile Home Parks in the southeast corner of the town of Yountville, California (Figures 1 and 2). The Town of Yountville is approximately 9 miles north of the city of Napa along State Route 29 (SR 29). The mobile home parks are located within the 100-year floodplain of the Napa River. The elevations of the mobile home parks range from 80 feet in the southeast corner of the Gateway Mobile Home Park to 86 feet in the northwest corner of the Rancho de Napa Mobile Home Park. They are bordered on the west by Hopper Creek and on the east by Beard Ditch (Figure 3). To the north and south are local drainage ditches that carry surface runoff from the mobile home parks and adjacent properties to Beard Ditch.
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SECTIONFOUR Affected Environment, Impacts, and Mitigation
2. Section2 TWO Purpose of and Need for Action
The objective of FEMA’s HMGP is to reduce the loss of life and property due to natural disasters and to enable long-term hazard mitigation measures to be implemented during the immediate recovery from a disaster. Through this program, FEMA provides grants to states, local governments, tribal governments, and U.S. territories to implement hazard mitigation projects after the declaration of a major disaster. The purpose of this project is to provide funding to the Town of Yountville to implement a cost-effective hazard mitigation project.
Since the mid-1960s, the Rancho de Napa and Gateway Mobile Home Parks have sustained damage from floods on a regular basis, necessitating the evacuation of residents. Recent evacuations include two in 1995 and one in 1997. Anticipated flood events over the next 20years would continue to cause damage to the mobile home parks, their structures and contents, vehicles, and infrastructure at an estimated cost of almost $6 million. After including the costs of disruption to the local economy, rescue services, and other expenses, the total cost of anticipated flood damages could be over $8 million. The Town of Yountville has identified the need to protect the mobile home parks’ residents and their 317 mobile homes from damages due to the periodic flooding of the Napa River.
Action is needed to:
- Protect the Rancho de Napa and Gateway Mobile Home Parks from future flooding events and remove the two mobile home parks from the 100-year floodplain of the Napa River.
- Provide adequate interior drainage facilities to keep the residual interior floodplain in the parks below a 1-foot depth.
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SECTIONFOUR Affected Environment, Impacts, and Mitigation
3. Section3 THREE Alternatives
3.1 Alternatives Not Carried Forward
3.1.1 Acquisition and Relocation of the Mobile Home Parks
This alternative would consist of the voluntary property acquisition and voluntary relocation of 317 mobile homes located in the Gateway and Rancho de Napa Mobile Home Parks. This alternative would also involve relocation of community facilities currently present in the parks, replacement of associated infrastructure, and restoration of the mobile home parks’ site to an undeveloped state. Mobile homes would be relocated where feasible, or existing structures would be demolished and replaced with new homes on another site. Property acquisition of both mobile home parks would require acquisition and subsequent relocation on an approximately 40-acre site.
There is no available site within the Town of Yountville of sufficient size, development opportunity, or cost that would allow for the wholesale relocation of the two mobile home parks. There are also no opportunities for the Town to annex additional lands for the purpose of development due to a Napa County ordinance requiring the preservation of all agricultural lands outside of the Town’s corporate limits. Existing mobile home parks within Napa County cannot accommodate relocation of approximately 317 residents, either in whole or in part. Given that these mobile home parks have been an established part of the Yountville community since the mid 1960s, and represent one-third of the Town’s overall housing stock (and a significant portion of the Town’s affordable housing), relocation of such a substantial portion of the Town’s residents out of an established and cohesive community is not feasible.
Additionally, both park owners would not agree to voluntary sale. Therefore, the Town would be required to condemn the property and use its powers of eminent domain to acquire the mobile home parks. This action would not conform to FEMA funding criteria and would render this alternative ineligible for federal funds.
From the information outlined in the Town’s initial application for FEMA HMGP funding in 1995, it was assumed that the cost of acquiring the mobile home parks would be $50,000 per space or more than $15.8 million for the two parks. That per unit cost factor included the cost of the land, the mobile homes, the removal of existing structures and infrastructure, site restoration and ongoing maintenance, and liability. Additional costs would be incurred, including relocation of the park residents ($15,000 to $20,000 per unit) and potential costs of condemnation. Given current real estate values, the initial cost estimate would most likely triple in value, making the cost of this alternative approximately $50 million dollars, assuming that a site is available. These financial issues, including ineligibility for FEMA funding, render this alternative infeasible.
3.1.2 Partial Acquisition of Mobile Homes
This alternative is a variation on the preceding alternative. It considers the potential issues and costs associated with acquiring only those portions of the two mobile home parks that are most susceptible to flood and associated damage. It is estimated that there are 40 to 50 mobile home spaces in the two parks that are most prone to severe flood damages.
To the extent that unoccupied spaces are available within the parks at the time of relocation, the disruption to the community under this alternative could be minimized. However, there are insufficient spaces available to accommodate relocation of 40 to 50 homes within the parks at one time. Acquisition costs were originally estimated at over $3 million plus relocation costs estimated at $750,000. As in the preceding alternative, these costs would be significantly higher under current real estate market conditions (over $6 million). Property owners indicated that they would not support even a partial acquisition, thus requiring condemnation proceedings that would also make this alternative infeasible.
It was estimated that approximately 5 to 7 acres of land would be required to relocate 40 to 50 mobile home spaces. No site is available in Yountville without changes to the general plan and current zoning. There are no known available sites in other Napa County cities with appropriate zoning or political support that would enable the Town to relocate 40 to 50 mobile home units. This alternative would also result in significant disruption to the community and would substantially reduce Yountville’s limited affordable housing opportunities.
3.2 Alternative 1: No Action
Under the No Action Alternative, FEMA would not provide funding to the Town of Yountville for flood hazard mitigation at the Rancho de Napa and Gateway Mobile Home Parks. No structural improvements would be implemented to protect the parks from flood hazards, and they would remain within the 100-year floodplain. Mobile home elevations would continue to be required to meet the Town of Yountville’s Flood Ordinance and federal requirements. The Town of Yountville would implement Town-wide drainage improvements, including creek maintenance at the west end of the parks, but this would not protect the parks from the projected periodic flooding damage, especially from the Napa River. The anticipated damages due to flooding would not be mitigated.
3.3 Proposed Action Alternative: Construction of a Floodwall
The Proposed Action consists of three primary parts: (1) construction of a masonry floodwall around most of the mobile home parks that closely matches the alignment of the existing perimeter fence, (2) construction of closure structures at the parks’ two entrances to provide flood protection at these locations, and (3) installation of interior storm drainage facilities consisting of storm drain lines, a drainage collection basin, and a pump station to handle storm water that falls within the parks. Improvements to the existing sewer mains are also proposed to prevent sewage backup. These project elements are presented in Figure 4.
3.3.1 Floodwall
A 10-inch-wide floodwall would be constructed of earth-colored blocks known as cellular masonry units (CMUs). These hollow blocks would be filled with concrete and reinforcement. A combination of flat-face and split-face blocks would be arranged in an aesthetically pleasing visual pattern. Based on hydraulic calculations, the height of the wall would vary from 9 feet to 2feet depending on the ground surface elevation and location within the floodplain. The height of the wall includes 3 feet of “freeboard” above the base flood elevation, as required by FEMA. A Sectionof the northwestern corner of Rancho de Napa is located outside of the floodplain limits and does not require a wall. However, a smaller 2-foot wall would be provided in this area for protection against floods that exceed the level of the 100-year event. The 2-foot wall would also protect against any out of bank flows from Hopper Creek that might occur if the Mission Drive or Champagne Drive culverts clog.