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This chapter provides policy for those issues which address specific resource values or public safety hazards but do not constitute principal uses of the land. These issues include natural hazards such as geologic, flood, and fire, and man-induced hazards such as noise, air quality, and industrial hazards. Also included are natural resource values such as important wildlife areas and habitats critical to the continued viability of certain species, and cultural resources such as historical buildings or archaeological sites.
Background
Land development in the unincorporated areas is subject to a number of hazards to life and property, including seismic and non-seismic conditions of land instability, flooding from several causes, fire, and dangers from airport operations.
The degree of risk associated with these hazards can only be measured in relative terms. What constitutes "acceptable risk" varies with the type of development involved. For instance, a hospital should meet very strict earthquake standards in order to ensure that it is able to function in the event of a serious earthquake. A warehouse, on the other hand, would not need to be designed to the same rigorous standards because its functions during an earthquake would not be critical to the community's response to the emergency, not would it pose serious risk to large numbers of people should it fail.
Many of the hazards discussed in this chapter are avoidable; they only pose a risk to life and property when people decide to use the land in ways which are unsuitable for the conditions in the area. This is clearly the case when people choose to build homes or roads in landslide areas or in flood plains. Other hazards are inherent to life in the County, such as earthquakes, and must be addressed through actions which mitigate but cannot eliminate their risks. Most of the actions available to the County to avoid or minimize risks impose a degree of control and restriction on private property. In establishing these restrictions, the General Plan is attempting to protect the public health, safety, and welfare within the following framework of values:
No individual involved in the subdivision, construction, or subsequent purchase of developed land in hazardous areas should be placed in jeopardy through failure to adequately assess the risks of a development proposal.
Private development in hazardous areas should not be allowed to impose a fiscal burden on the general taxpayer through actions which are likely to have unusually high service and maintenance costs.
Humboldt County is a relatively hazardous area in terms of ground shaking
and fault rupture, landsliding, and soil erosion. The following sections
briefly describe the seismic setting, bedrock geology, and soils of the
County.
3211 Seismic
The County is in the two highest seismic risk zones of the Uniform Building Code, and offshore Cape Mendocino has the highest concentration of earthquake events anywhere in the continental United States. The area near Cape Mendocino is a complex, seismically active region, influenced by the subducting Gorda Plate. The majority of earthquakes have focal depths between 15 and 35 km (10 to 20 miles); shallower earthquakes can also be expected both onshore and offshore in this area.
It is the subducting Gorda Plate that give rise to the "deep seismic zone" which generates much of the earthquake activity of the region. The effects of the rather large earthquakes triggered in this zone are somewhat dampened by the depths at which they occur (12-21 miles). The two other major sources of earthquake activity are the San Andreas fault and the Mad River fault zone (including the Falor and Korbel faults).
The above described seismic setting has the potential to cause significant ground shaking, leading to: (1) a serious liquefaction hazard, particularly around the muds and sands of Humboldt Bay; (2) a significant landslide hazard countywide; and, (3) a surface fault rupture along the San Andreas, and possibly along the Little Salmon fault zone, and other active or potentially active faults in the County.
The bedrock geology of the County is divided generally into two provinces: the Klamath Mountains province in the northeast, and the Coast ranges province in the central and southwest portion of the County. The dividing line between the two provinces is the South Fork Mountain Ridge, which separates the Trinity River basin from the Mad River and Redwood Creek drainages.
The Klamath Mountains province is an area of high alpine peaks, some attaining elevations of 8,000 feet and more, east of the Humboldt County line. The province is drained by the Klamath and Trinity Rivers, and farther north, by the Smith River. Rocks in the Klamath Mountains province are generally older than those in the Coast Ranges. Rocks of sedimentary origin such as sandstone, chert, slate and schist occur abundantly, with occasional granite intrusions.
The Coast Ranges province is the dominant geologic province in the County, trending northwest and drained by the Mad, Eel, and Mattole River drainages. The Franciscan and Yager complexes dominate inland, with sand and other alluvial deposits dominating in the lower reaches of the river basins and the area surrounding Humboldt Bay.
The Franciscan complex can be divided into two distinct units. Franciscan sandstone consists mainly of sandstone and siltstone. Although this sandstone unit is frequently sheared, there is little evidence of massive rock deformation. Slopes are fairly stable, but subject to debris sliding along steep river banks and in steep headwater drainages.
Franciscan melange consists of a rubble of sheared sandstone and siltstone in which occur more competent blocks of volcanic rock, chert, and schist. Melange terrain is generally unstable and characterized by rolling hummocky slopes which are highly susceptible to mass movement.
The Yager formation is predominantly shale and sandstone. Local shearing occurs, but in general the formation is much less deformed and more stable than the Franciscan. However, it is subject to debris slides on steep slopes and river banks.
In the lower reaches of the river basins and in the area surrounding Humboldt Bay, alluvial sediments dominate. These unconsolidated to partially consolidated sediments have been mildly folded and faulted, but when forested or gently sloped, are generally stable.
The bedrock geology is poorly mapped in much of the County, particularly
the inland areas. Lack of detailed mapping in most cases precludes determining
specific site stability without a site investigation. However, it may be
valid to conclude varying degrees of relative risk based on general mapping
of rock units when averaged over time.
3213 Soils
There are many varied soils in Humboldt County. Some of the more abundant agricultural and lowland soils found in the County are the Ferndale series, a deep, well drained soil formed on recent flood plains; the Bayside and the Loleta series, both deep, poorly drained soils found in depressed areas or on nearly level alluvial fans; and the Rohnerville, Carlotta and Hookton soils series, all moderately well-drained soils.
Rohnerville soils are found on relatively flat, high marine terraces. The Hookton soils are on sloping, dissected marine terraces and the Carlotta soils are found on flat, low-lying terraces. Most of these agricultural soils are rated 80-100 in the Storie Index of agricultural productivity (good to excellent productivity), except the Bayside soils where drainage problems may reduce agricultural potential.
1. Forest Soils
The forest soils of the County are, in general, medium textured, acid in reaction, and generally increasing in acidity with depth. They are permeable and well drained.
In the lowlands they are formed on alluvial flood plains or low-lying terraces. Here they are either unclassified or of the Carlotta and Ferndale groups. The most superlative old growth redwood groves are found on these soils.
2. Grassland Soils
The general characteristics of grassland soils vary widely. They range from shallow loamy soils to deep clay soils. Their permeability ranges from moderate to slow. The general nutrient level of these grassland soils is higher than that of the adjacent forest soils. The major portion of these soils is intermingled with other soils in the Douglas fir zone beyond the fog belt. Some of these soils are formed on Franciscan parent material. Many of these are found in the shear zone or fault gouge material or on the melange material of the Franciscan. This parent material weathers rapidly, forming a grey-blue clay subsoil (commonly called "blue goo") that tends to slip when wet. Thus, because of the parent material, these soils are found in landslide topography.
3. Woodland Soils
Most of the woodland soils are inland beyond the cool, foggy belt. They are intermingled with the conifer forest soils of the Douglas fir belt and the adjacent grassland soils. These are shallow soils, usually well drained, but permeability may be slow in some locations. The natural nutrient level of these soils tends to be somewhat higher than for the neighboring forest soils. Because the parent material is predominantly Franciscan melange, one should expect these soils to be relatively unstable.
In contrast to the information on the County's bedrock geology, the available soils information is quite detailed. Soil-Vegetation maps prepared by the California State Cooperative Soil-Vegetation Survey are available for the County at the 7-1/2 minute scale. These maps describe vegetation and soils, including information of parent rock materials, soil depth, erosion, and slope.
Slope stability refers to the landslide susceptibility of slope-forming materials composed of natural rock, soils, artificial fill, or combinations thereof. Landslides move along surfaces of separation by falling, sliding, and flowing, giving rise to many characteristic features. The features range in appearance from being clearly discernible, largely unweathered and uneroded, to highly weathered and eroded, recognized only by topographic configurations.
Landslides are characteristically abundant in areas of high seismicity, steep slope, and high rainfall, but may be triggered by any or a mixture of the following: (1) type and structure of earth materials, (2) steepness of slope, (3) water, (4) vegetation, (5) erosion, and (6) earthquake-generated groundshaking.
The factors listed above are just some of the many complex factors contributing to the formation of landslides. The prediction of slope failure at a specific site, therefore, requires an analysis of all possible factors. As part of the County General Plan, relative slope stability maps have been prepared to provide general delineation of areas susceptible to sliding. Still, these maps must be used with caution, since it is possible that areas not presently known to be unstable are designated as stable and the inverse may also be true.
Flood hazards in Humboldt County can be attributed to three sources: rivers, dam failure, and coastal high water hazards (tsunamis and flood tides). River flooding is by far the most prevalent flood hazard, with flood alert occurring most every year during the rainy season (October to April).
The 1955 and 1964 floods caused extensive damage along the Eel, Mad, and Trinity Rivers. Damages in the County from the 1964 flood totaled $100 million. The flood prone areas have recently been remapped by the Federal Emergency Management Agency (FEMA). The maps provide the basis for regulating flood plains in conformance with the National Flood Insurance Program. The County has recently revised its flood plain regulations in order to continue participation in the federal program.
While providing some degree of flood control, dams also present a possible hazard in the event of failure. Trinity Dam and Ruth Dam pose the most substantial risk, with large volumes and short warning times.
Hazards from dam failure are those associated with the downstream inundation that would occur given a major structural failure of a nearby impoundment. Such failures would most likely be caused by geologic phenomena including seismic events and slope stability problems.
There are no dams within the County of a size such as to be within the above requirements. However, five dams are located in adjacent counties on rivers that drain into Humboldt County, and the failure of any one of these structures could significantly impact this County.
The County maintains emergency response plans for the Trinity, Ruth (Matthews), Scott, Copco and Iron Gate dams.
3223 Coastal High Water Hazards
Tsunamis and flood tides are coastal flooding concerns that are given policy treatment in the local coastal programs. The County maintains a Tsunami Contingency Response Plan for emergency response.
Humboldt County exhibits extreme diversity in it potential for destructive fire, from nil to extreme in severity classification. The wildfire hazard in the County has been analyzed using the methodology of the California Department of Forestry Report to the Governor's Office of Planning and Research (1973), modified to account for conditions not included in their procedure. This method takes into account climate, the fuel potential of the vegetation and topography.
CDF's fire hazard methodology as applied to Humboldt County and the distribution of zones is shown on the Wildfire and Flood Hazard Map. This distribution generally reflects a moderate to high rating on the western portions of the County where the fuel potential is high but the climate is damp. The extreme ratings are generally in the drier eastern portions of the County or in very steep terrain.
Policy application of the fire ratings is by referring to the map of Wildland Fire and Flood. The Planning Department determines which applications should be reviewed by the appropriate fire protection agency, and considers their response in the approval and requirements for development application. This method reduces the risk to structures and their occupants, as well as the threat to surrounding wildland vegetation. This risk which wildland occupants cause others is also reduced by the requirement of fire safety measures.
The standards that are used as guidelines for development reviewed by the Planning Department to reduce the hazard of fire are the CDF "Fire Safe Guides" (CDF, 1980). Other County standards are listed in Title III, Division 2 Subdivision Regulations, and the newest edition of the Uniform Building Code. The Fire Safe Guides are applied with some discretion due to competing policy concerns such as adequate road width for emergency vehicles versus increased erosion from wider road widths.
The principal sources of noise in Humboldt County are highways, airports, rail, on-site construction, and industrial activities.
The Environmental Protection Agency identifies 45 Ldn indoors and 55 Ldn outdoors as the maximum level below which no effects on public health and welfare occur. Ldn is the Day-Night Noise Level. Ldn is the average sound level in decibels, excluding frequencies beyond the range of the human ear, during a 24-hour period with a 10dB weighting applied to nighttime sound levels.
A standard construction wood frame house reduces noise transmission by 15dB. Since interior noise levels for residences are not to exceed 45dB, the maximum acceptable exterior noise level for residences is 60dB without any additional insulation being required. Of course, this would vary depending on the land use designation, adjacent uses, distance to noise source, and intervening topography, vegetation, and other buffers.
The General Plan appendix contains noise level contours for state highways, elected county roads, and county airports. These noises contours and other available noise information are used with the noise compatibility matrix (see Figure 3-2) to establish requirements for project approval to ensure that new development is consistent with the General Plan. Fences, landscaping, and noise insulation can be used to mitigate the hazards of excessive noise levels.
Noise insulation standards have been developed by the State for application to all new multi-family residential construction.
Most of the County's noise hazards are found within incorporated cities. Figure 3-3 lists prominent noise sources for each community.
The Public Works Department operates nine county airports. The Department
has prepared an Airports Master Plan which establishes airport land use
compatibility policies, and maps the application of these policies for
the Arcata-Eureka (McKinleyville) Airport, Murray Field, and Rohnerville
Airport. These policies are incorporated into the General Plan. The General
Plan applies these compatibility policies to the County's six other airports.
LAND USE/NOISE COMPATIBILITY STANDARDS
| CLEARLY
ACCEPTABLE |
NORMALLY
ACCEPTABLE |
NORMALLY
UNACCEPTABLE |
CLEARLY
UNACCEPTABLE |
|
LAND USE INTERPRETATION |
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| LAND USE CATEGORY |
Maximum |
55 | 65 | 75 | 85 | ||||||
| Residential-Single Family, Duplex, Mobile Homes | 45 | ||||||||||
| Residential-Multiple Family, Dormitories, etc. | 45 | ||||||||||
| Transient Lodging | 45 | ||||||||||
| School Classrooms, Libraries, Churches | 45 | ||||||||||
| Hospitals, Nursing Homes | 45 | ||||||||||
| Auditoriums, Concert Halls, Music Shells | 35 | ||||||||||
| Sports Arenas, Outdoor Spectator Sports | |||||||||||
| Playgrounds, Neighborhood Parks | |||||||||||
| Golf Courses, Riding Stables, Water Rec., Cemeteries | |||||||||||
| Office Buildings, Personal, Business and Professional | 50 | ||||||||||
| Commercial-Retail, Movie Theaters, Restaurants | 50 | ||||||||||
| Commercial-Wholesale, Some Retail, Ind., Mfg., Util. | |||||||||||
| Manufacturing, Communications (Noise Sensitive) | |||||||||||
| Livestock Farming, Animal Breeding | |||||||||||
| Agriculture (except Livestock), Mining, Fishing | |||||||||||
| Public Right-of-Way | |||||||||||
| Extensive Natural Recreation Areas | |||||||||||
(Source: Bolt, Beranek, and Newman, Inc., 1974)
| COMMUNITY |
SOURCE OF NOISE |
||||
| ROADS | AIRPORTS | RAILROAD | STATIONARY SOURCES | ||
| ARCATA | U.S. 101, State Highways 299 & 255 | NONE | NorthwesternPacific Railroad & Arcata/ Mad River |
NONE | |
| BLUE LAKE | State Highway 299 | NONE | Arcata/Mad River | NONE | |
| CARLOTTA | State Highway 36 | NONE | NONE | NONE | |
| EUREKA | U.S. 101, Myrtle Avenue, Harris, Henderson & "H" Streets | Murray Field | Northwestern Pacific Railroad | Redwood Acres | |
| FAIRHAVEN | New Navy Base Road | NONE | NONE | Mill | |
| FERNDALE | State Highway 1 | NONE | NONE | NONE | |
| FIELDBROOK | NONE | NONE | NONE | NONE | |
| FORTUNA | U.S. 101, Main Street | Rohnerville | Northwestern Pacific | NONE | |
| GARBERVILLE | U.S. 101 | NONE | NONE | NONE | |
| HOOPA | State Highway 96 | NONE | NONE | NONE | |
| HYDESVILLE | State Highway 36,
Rohnerville Road |
NONE | NONE | NONE | |
| LOLETA | NONE | NONE | Northwestern Pacific | NONE | |
| MANILA | State Highway 255 (Navy Base Road) | NONE | NONE | NONE | |
| McKINLEYVILLE | U.S. 101, Central Avenue | Eureka/Arcata | NONE | NONE | |
| MOONSTONE/
WESTHAVEN |
U.S. 101 | NONE | NONE | NONE | |
| ORICK | U.S.101 | NONE | NONE | NONE | |
| REDWAY | Redwood Drive | NONE | NONE | NONE | |
| RIO DELL | U.S. 101,
Wildwood Avenue |
NONE | Northwestern Pacific
Railroad |
NONE | |
| ROHNERVILLE
(See Fortuna) |
|||||
| SAMOA | New Navy Base Road | NONE | NONE | Mill | |
| SCOTIA | U.S. 101 | NONE | Northwestern Pacific
Railroad |
Mill | |
| TRINIDAD | U.S. 101 | NONE | NONE | NONE | |
| WEOTT | U.S. 101 | NONE | NONE | NONE | |
| WILLOW CREEK | State Highways 299 & 96 | Willow Creek | NONE | NONE | |
The Airport Land Use Commission (presently embodied as the Board of Supervisors) coordinates with applicable agencies in ensuring compatible land uses for areas surrounding county airports.
The principal airport/land use compatibility issues at most airports are:
Airspace: The height of structures, trees, and other objects in the vicinity of an airport greatly affects the use of that airport.
Safety: Controls on land uses near airports can reduce potential risks both to people on the ground and to the occupants of aircraft.
The reader is referred to Chapters 9 and 10 of the Airports Master Plan, attached as Appendix H to Hazards Policy Background Study, for a more detailed discussion of off airport land use issues and policies.
Close coordination is needed between the Planning and Public Works Departments of the County in making land use and zoning decisions around the airports. Specific attention to this issue will be given in the Community Plans, most importantly the McKinleyville Community Plan.
Air quality policy and regulation is implemented by the North Coast Unified Air Quality Management District (UAQMD). The District is part of the North Coast Air Basin and shares responsibility for implementation of the Basin Air Pollution Control Plan with the other north coast counties in the basin.
The primary responsibility of the County UAQMD is to control air emission from stationary sources, while for transportation related sources, state and federal authority dominates.
The County UAQMD permit authority gives it the primary role in achieving air quality goals, thus the policy suggested for inclusion in the General Plan is limited to ensuring coordination between the goals of the District and the General Plan.
Whereas in major metropolitan areas of San Francisco and Los Angeles, air quality concerns are tied closely to future patterns and levels of urbanization, the issues of major concern to the north coast are less directly related to urbanization, but more specifically related to industrial point sources. Because the forest products industry is the chief industry in the County, particulate emissions related to timber processing are a primary focus of the Basin Plan. To quote the Plan:
"The main thrust of the air pollution control plan for the North Coast Air Basin will continue to be directed toward the reduction of particulate emissions and the minimization of the unique odor problems by the Kraft pulp mills..." (Air Pollution Control Plan for the California North Coast Air Basin, 1977, page 17).
One air quality issue relating to residential development that may present itself in the near future arises from the increased use of wood as a home heating fuel. Several mountain communities in Colorado, for instance, have found it necessary to regulate home wood burning to protect the sensitive mountain valley airsheds. The approach there generally has been to limit the number of open fireplaces in new construction and encourage the use of cleaner and more efficient air tight woodstoves.
The valleys of Jacoby Creek and Elk River may be prone to this problem, but air monitoring data gathered thus far does not show any significant contribution of particulates by residences. Should the need arise for such a control strategy, implementation might most easily be handled by the Planning and Building Departments, rather than the UAQMD.
Several specific industrial activities have been identified as having the potential to cause significant damage to the surrounding area in the event of an accident. These activities include the use of chlorine at the Samoa pulp mills, shipping and receiving of hazardous materials other than chlorine, and the nuclear materials at the P.G. & E. Humboldt Bay Power Plant. Each of these activities/facilities has a contingency plan which directs the appropriate disaster responses. In addition, policy is provided here to address the siting of new hazardous industrial facilities.
For a fuller discussion of these issues, the reader is referred to the Hazards Policy Background Study, Section 2.80.
Although a solid waste element is not one of the nine required General Plan elements, the passage of the NejedlyZ'bergDills Solid Waste Management and Resource Recovery Act of 1972 established the mandate that each county prepare a comprehensive, coordinated solid waste management plan (Government Code Section 66700 et seq.). Such a plan is subject to approval by a majority of the cities within the County which contain a majority of the population of the incorporated area of the County.
In addition, the issues of solid waste handling and disposal may also require attention pursuant to Government Code Section 65302(a), which lists solid and liquid waste disposal facilities as a use to be designated in the land use element. The safety element (Government Code 65302(i) also may be considered an appropriate place to discuss the issues relating to hazardous materials handling. A public services and facilities element is a permissive element described in Section 65303(e).
In the outline of the County's General Plan, solid waste is addressed both in this section of the Plan and as a section in the Public Facilities Chapter.
As a means of insuring consistency and coordination with the recently adopted Solid Waste Management Plan (1981), relevant policies of that document are included here.
1. To reduce public exposure to natural and manmade hazards.
2. To ensure the continuity of vital services and functions.
3. To educate the community.
1. General
B. Development within the coastal zone shall minimize risks to life and property in areas of high geologic, flood and fire hazard, assure stability and structural integrity and neither create nor contribute significantly to erosion, geologic instability or destruction of the site or surrounding areas or in any way require the construction of protective devices that would substantially alter natural landforms along bluffs and cliffs.
C. Encourage the education of the community regarding the nature and extent of hazards.
D. Continue to provide for the maintenance and upgrading of disaster response plans.
B. Provide for more detailed scientific analysis of natural hazards in the County.
C. Provide for implementation and periodic review of the Seismic Safety and Public Safety Element.
B. Agricultural lands which are in flood plain areas shall be retained
for use in agriculture.
B. Use the appropriate sections of the California Department of Forestry "Fire Safe Guides" as guidelines for review of residential development in rural areas, to be applied consistent with other plan policies.
C. Actively support and pursue the implementation recommendations of the Humboldt County Fire Chief's Association (see Fire Hazards Implementation, Section 5-2300.3).
B. Existing and potential incompatible noise levels in problem areas should be reduced through land use planning, subdivision review, building code enforcement, and other administrative means.
C. The land use noise compatibility matrix (Figure 3-2) shall be utilized as the standard for General Planning and zoning purposes.
D. Provide for periodic review and revision of the Noise Element.
E. A local interagency program should be developed for the general public in the nature, extent, and solutions to noise problems in Humboldt County.
F. Coordinate noise control activities with those of other responsible jurisdictions.
G. Identify and evaluate potential noise problem areas on a continuing basis.
B. The County's current Airport Approach Zone Building Height Regulations (County Code Section 333) should be revised to bring the standard into conformance with Part 77 of the Federal Aviation Regulations. (A recommended ordinance has been prepared by the Consultant and submitted to the County as a separate task in the Master Plan Study).
C. Regulate and plan land use around airports according to the Airport Land Use Compatibility criteria matrix.
D. Specific land use zoning, appropriate for the areas around the County's airports, should be adopted as soon as practical.
E. Ensure that future development within the community is compatible with the airport and its associated noise and hazard nuisances.
2) Increased risks to adjacent human populations have been adequately mitigated by approved disaster response plans. (See definition of "hazardous industrial development" in Standards section.)
B. Minimize the environmental impact of solid waste handling and disposal.
1. Require geologic reports according to the Geologic Hazards Land Use Matrix as follows:
A. R1 Report Requirements:
2. The preliminary engineering geologic report shall be prepared by a certified engineering geologist and shall provide a geological reconnaissance and evaluation of the project site and surrounding terrain. The preliminary report shall identify areas or issues which either do or do not require further engineering geologic and/or soils engineering evaluation.
3. The preliminary soil engineering report shall describe the nature of the subsurface soils and any soil conditions which would affect the design and/or layout of the proposed development. The report shall include the locations and logs of any test borings and percolation test results if on-site sewage disposal is proposed. The report shall recommend areas or issues of concern which require additional engineering or geologic evaluation.
4. The additional information that is recommended by the preliminary reports shall be provided or the proposed development shall be modified to avoid the identified areas of potential instability. The proposed development shall be sited and designed in accordance with the recommendations of the reports in order to minimize risk to life and property on the project site and for any other affected properties.
NOTE: A report prepared by a registered geologist is required in the fault rupture Special Studies Zone unless waived pursuant to the Alquist-Priolo Act.
2. A soils engineering analysis may meet the preliminary geologic report requirement for developments where the primary concerns are soils mechanics and appropriate structural design. In such cases it is incumbent upon the engineer to consult a registered geologist should it become apparent that an adequate structural solution requires additional geologic input. If, after preliminary investigation of the project site and the surrounding terrain, no geological consultation is felt by the engineer to be required, the engineer shall certify that such an evaluation is not required. It is incumbent upon the geologist to recommend that a soils engineer be consulted when it becomes apparent that soils mechanics analyses are needed.
3. The applicant shall either provide additional information as recommended by the preliminary geologic or soils report or modify the application to avoid identified areas of potential instability. The proposed development shall be sited and designed in accordance with the recommendations of the report(s) in order to minimize risk to life and property on the project site and for any other affected properties.
D. The report requirement may be waived when an adequate geologic assessment at a suitable scale already exists for the site proposed for development.
E. The criteria for determining whether or not a report is required when it is discretionary include the following; however, where evaluation of items 1-6 is inconclusive, a statement is required by a registered engineer that a geologic report is not required for the safety of the project.
2) geologic maps and reports covering the area;
3) the potential for the development to affect adjacent property or improvements;
4) the degree to which public exposure to risk may be a factor;
5) the size and scale of the proposed development;
6) for development within the Coastal Zone, the policies of certified local coastal plans.
G. Utilize California Department of Forestry (CDF) series of 15 minute geologic maps and 7 1/2 minute landslide maps as information to assist in review of developments. (Res. 85-126, 12/17/85)
H. Utilize California Mines and Geology Board policies and Criteria for Alquist-Priolo Special Studies Zones as standards of implementation within zones.
B. Tsunami Run-up Report: H-78-26, Army Corps of Engineers.
B. Air Pollution Control Plan for the California North Coast Air Basin.
B. Chlorine Accident Contingency Plan.
C. Humboldt Bay Nuclear Reactor Contingency Plan.
D. Prohibition on Transport of Nuclear Materials (Ordinance #1403; Humboldt County Code, Title III, Division 8, Chapter 3).
E. Define "Hazardous industrial development" as any development that handles toxic, flammable, or explosive materials in such quantities that would, if released or ignited, constitute a significant risk to adjacent human populations or development.
B. Require new development which may generate significant quantities of hazardous wastes to provide a plan for disposal which emphasizes on-site treatment, neutralization, and recycling.
The topic of water in Humboldt County is discussed in various sections of the Plan. Flooding and dam failure are discussed in the Hazard section. Water supply for domestic purposes is discussed in the Development Timing and Public Facilities sections. Water as an important component of wildlife habitat is discussed in the Biological Resources section.
This section, containing a discussion of water as a natural occurring resource, addresses some of the requirements of the Conservation and Open Space Elements.
Under the Conservation Element, state law requires:
(2) Open space for the managed production of resources including...areas required for recharge of ground water basins, bays, estuaries, marshes and rivers and streams which are important for the management of commercial fisheries..."
(4) Open space for public health and safety including... watershed, protection of water quality and water reservoirs. (Government Code Section 65560(b).
| Fault | Critical | |||||||||||||
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| hazardous | Nuclear power plants,
major dams, hazardous chemical storage |
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| essential | Hospitals, fire and police stations, civil defense headquarters, life line utility systems, ambulance stations |
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| high risk | Schools, theaters, auditoriums, hotels, large motels, major office buildings, high density residential, redundant utility systems, major highway bridges | |||||||||||||
| low risk | Major subdivision, heavy industrial |
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| Residential structures on existing lots with footing loads greater than typical two story wood-frame dwellings |
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| Residential wood frame structures two stories or less on existing lots |
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D means preliminary report is discretionary
*SSR means Alquist-Priolo Special Studies Zone - see NOTE in Section 3292.1B
Minor Subdivision: subdivisions requiring the filing of a parcel map pursuant to the Subdivision Map Act.
Much of Humboldt County is either blessed with an abundance of water resources or cursed with such a resource, depending upon the time of year and the amount of flow. Because of the disparity of flow conditions, which is directly related to the rainfall within the area, insufficient summer flows are experienced in many areas of the county. As recently as 1977 there were drought conditions affecting water supplies countywide.
The hydraulic basins in Humboldt County, like most parts of the North Coastal area, provide very large surface water volumes. Mean annual runoff in Humboldt County from the major rivers and streams is approximately 23 million acre feet. In comparison, total groundwater yield of the entire County is approximately 100,000 acre feet. The largest individual drainage area of the County is that of the Eel River and its various tributaries. The contributory surface area involves over 763,000 acres, and is in excess of one-third of the surface area of the County.
The total average annual runoff of the rivers running through the County reflects almost 30 percent of the total runoff of the State of California, yet there is an extreme variance in flows of the various rivers. For example, the Mattole River has a maximum recorded winter discharge in excess of 90,000 cubic feet per second and a minimum summer flow of under 20 cubic feet per second.
Since the flows of all of the rivers in the County except the Trinity and Klamath Rivers are directly related to the precipitation within the area, and over 80 percent of the flows of these streams occur during the months of November through March, it is important to note that insufficient summer flows could create some problems in the future. The 1975 Winzler and Kelly report stated that, insofar as the domestic projections for water needs of the rural communities are concerned, the major rivers and their perennial tributaries should meet future demands for water. Updated population projections are well within those used in the report. However, facilities to distribute this supply are in many cases inadequate to meet the projected demand.
The steep terrain of Humboldt County coupled with the amount of runoff, offers a tremendous opportunity for generation of electricity with small hydroelectric projects. Development of this resource should be much less detrimental to fish populations than large hydroelectric dams. Access to electrical transmission lines is often a barrier to development of small hydroelectric projects. (See Section 2530).
Ground water development in the rural area of Humboldt County has generally been directed only to individual domestic requirements or to the irrigation demands of the more extensively farmed areas of the Eel River delta and Mad River delta areas.
The prime source of ground water, insofar as quantity, lies in the Eel River and Van Duzen delta. Though the storage capacity is about 136,000 acre feet, the usable yield of this ground water storage basin is estimated to be 40,000 to 60,000 acre-feet annually. A little more than 10,000 acre- feet of ground water is currently being pumped from the basin for use in agricultural purposes (Winzler and Kelly, 1973). The Mad River basin has been reported to have a yield of about 45,000 acre-feet annually (Baruth and Yoder, 1973).
Other ground water basin areas include: Hoopa Valley, Prairie Creek, Big Lagoon, Mattole River Valley, Honeydew, Pepperwood, Weott, Garberville, Larabee Valley, and Dinsmore.
More wells each year are being drilled to serve new development,
yet little is known about the location or capacity of the groundwater aquifers.
Better estimates of ground water availability is needed so development
will not surpass the capacity.
3330 WATER QUALITY
The relatively high water quality of Humboldt County's waters make it all the more important to maintain and protect this aspect of the area's environment. Technological advances in sewage treatment plants, together with the Federal Clean Water Grant Program, have substantially reduced pollution problems of our bays and rivers. Septic systems in rural areas and their cumulative impacts on water quality is a more difficult management problem, however. Past water resources developments which have failed to fully mitigate fisheries impacts are also of concern.
Soil-disturbances associated with human activities have caused a significant increase in siltation and sedimentation in streams and reservoirs. Vegetation removal, for instance, can cause water to run off slopes more rapidly, causing increased erosion. The resulting water pollution causes damage or losses to fish habitat and fish populations, impairs water-related recreation and tourism, reduces the life span of reservoirs, and can increase flood damage. Major soil-disturbing activities include road-building, logging, vegetation clearing, over- grazing, mining, and certain agricultural practices. The Regional Water Quality Control Board's waste discharge requirements, the California Department of Fish and Game's streambed alteration agreements and the State Board of Forestry Timber Practice rules provide some controls on certain soil-disturbing projects. Other activities such as grading and private road building follow the Uniform Building Code grading chapter. An implementation measure of this section recommends revision of the grading ordinance to ensure adequate erosion control protection.
Humboldt County generally has sufficient water resources where the majority of the population reside. Presently quality, with regard to domestic use, is high. Urbanization and industrial pollution have not seriously plagued Humboldt County water resources. The ground water basins near the coast exhibit salt water intrusion, but the boundary has remained stable for the past several years. The potential pollution resulting from urbanization and other land uses needs to be prevented. Many of the activities that can affect a community's quality of water occur away from the community area in some other part of the drainage basin. Concerns for preventing water quality degradation must encompass the entire watershed area.
Variance in water availability, both seasonally and geographically, necessitates an assurance of a year round available water supply. Many of the existing communities are located on the flat coastal plains and the timing of new development, should be consistent with the available water supplies and the existing uses of water.
Conditions are not the same for much of the inland areas. Many of the rural areas depend upon ground water for individual sources of water. Because of high summer temperatures and low water-bearing soils, many areas cannot provide a suitable year round water supply. Past developments have shown that some rural parcels have been created that cannot support residential usage. Since each created parcel is supposed to be a legally buildable site, it is necessary to assure on-site water availability prior to receiving final approval for land use development
Because of the extremes of water availability, serious
consideration should be given to water conservation techniques. More information
is required for groundwater management, irrigation efficiency, water pricing,
building and health regulations and thoughtful land decisions. Techniques
that can be utilized now include domestic and industrial water flow restrictors,
native vegetation landscaping, water reclamation, and education programs.
The added benefit of saving the water pumping costs and energy when water
is conserved should be emphasized when encouraging water conservation.
3350 WATER EXPORT
The Humboldt County Board of Supervisors appointed a 16 member committee to develop a Water Policy Statement. This was adopted by the Board on June 12, 1978, which states in part:
The County Board of Supervisors has been participating in water resource projects such as the joint management programs on the Eel and Trinity Rivers, as well as the Van Duzen Management basin. This participation should continue to be an important part of the Board of Supervisors' responsibility.
Major water impoundments occur on both the Trinity and Eel River outside of the County. These have both decreased the fishery resource and increased the erosion and sedimentation in the County by not allowing sufficient flows to keep sediment from accumulating in the streams. Additional flow releases are being pursued for these rivers.
Other investigations are needed to ensure the protection of the needs of the people regarding water resources. According to a recent report of the Governor's Commission to Review California Water Rights Law:
Wild and Scenic Rivers
The following rivers of Humboldt County have been designated as components of the Wild and Scenic Rivers System.
Trinity River -the main stem from 100 yards below Lewiston Dam to the river mouth at Weitchpec; the South Fork of the Trinity from the junction of the river with State Highway 36 to the river mouth near Salyer.
Eel River -the main stem 100 yards below Van Arsdale Dam to the Pacific Ocean; the South Fork of the Eel from the mouth of Section Four Creek near Branscomb to the river mouth below Weott; Middle Fork of the Eel from the intersection of the river with the southern boundary of the Middle Eel-Yolla Bolly Wilderness Area to the river mouth at Dos Rios; North Fork of the Eel from the Old Gilman Ranch downstream to the river mouth near Ramsey.
Van Duzen River from Dinsmore Bridge downstream to the river mouth near Fortuna at the Eel River.
Those portions of the Eel River included in the State Wild and Scenic Rivers Act are only ensured protection from new dams and reservoirs until 1984. At that time, the California Department of Water Resources "shall report to the Legislature as to the need for water supply and flood control projects on the Eel River and its tributaries, and the Legislature shall hold public hearings to determine whether legislation should be enacted to delete all or any segment of the river from the system."
2. To maintain a dependable water supply, sufficient to meet existing and future domestic, agricultural, industrial needs and to assure that new development is consistent with the limitations of the local water supply.
2. Regulate development that would pollute watershed areas.
3. Ensure that the intensity and timing of new development will be consistent with the capacity of water supplies.
4. Existing water uses shall be considered during the review for new water uses.
5. The availability of groundwater should be used as a prime factor in determining the desirable amount of residential development in a particular area in order to protect groundwater resources from depletion or contamination.
6. Projects must provide evidence of water availability prior to recordation of map.
7. Maximize the use of water conservation techniques appropriate for new and existing development.
8. Continue participation in all state, regional or local water resource planning efforts effecting surface run-off or groundwater supplies.
9. Encourage further investigation on the County's water resources by federal and state water resource agencies.
10. Large water export projects will not be approved or supported unless specific requirements and assurances are satisfied. These shall include the 1978 water policy statement policies regarding "Water Export Projects on Humboldt County Streams". (See Standards 5a-1)
11. Support flow release schedules from existing reservoirs that maintain or enhance the fisheries of those rivers.
12. Support the development of fisheries enhancement projects on small Humboldt County streams.
13. Ensure that projects located within state designated wild, scenic or recreational river basins are consistent with the guidelines in the State Wild and Scenic Rivers Act (as amended).
14. The development of environmentally sound small hydroelectric projects on publicly and privately owned lands in Humboldt County is generally encouraged. The County should only examine small hydroelectric project proposals for impacts not reviewed by other agencies and for overall consistency with the intent of the General Plan.
2. A Critical Water Supply Area is defined as the specific area used by a municipality or community for its water supply system, which is so limited in area that it is susceptible to a potential risk of contamination from development activities.
3. Development proposed within Critical Water Supply Areas shall demonstrate that no risk of contamination to the water supply area would occur due to the development activity proposed.
4. Development within Critical Water Supply Areas shall utilize appropriate Erosion Control Measures including, but not limited to, those in Section 3432.9.
5. "Water Conservation Techniques" include but are not limited to, domestic and industrial low-flow water fixtures and native vegetation landscaping.
6. Water Export Projects on Humboldt County Streams.
The Humboldt County Board of Supervisors, prior to giving its approval and support to large export projects on County streams, will require the following:
B. Full recognition shall be given to the ecological impact of any proposed project. Appropriate ecological studies by a team of independent experts, qualified to conduct such studies, should be funded by the project sponsor and completed before project authorization.
C. Absolute assurance must be given that funding will be made available for development and improvement of suitable fisheries above, and maintenance and improvement of native fisheries below, any project. Absolute assurance must also be given that funding will be made available for the effort to replace, restore, and maintain the native wildlife habitat destroyed or altered by any of the contemplated projects. The funding requirement for such development, improvement and maintenance of the fisheries and native wildlife habitat set forth herein above, shall be a funding requirement of the project and shall be identified as a commitment of the state, federal or local entity sponsoring the project. Recognition must also be given to the difficulty in accurately predicting long range financial requirements to meet the fisheries and wildlife policies set forth herein. Consequently, reappraisal and adjustments should be considered on five to ten year schedules throughout the projected project life in order to meet all of the funding requirements which may occur during the project life. Funding shall be provided for post project evaluation. Wildlife mitigation should be accomplished insofar as possible on existing public lands with prime consideration given to the wildlife resources involved and to its habitat requirements.
D. Inasmuch as Native Americans comprise a large segment of Humboldt County's population with environmental and historical ties to some of the river valleys, assurances must be given prior to the construction of any water project that no Indian tribal lands, including burial, or ceremonial grounds in Humboldt County will be inundated without specific prior consultation with the Indian people concerned.
E. Water supplies must be planned and financed as part of any project in sufficient quantity to provide ultimate future supplies of agricultural, municipal, industrial, recreational, and environmental water, and water for fisheries and wildlife habitat development. Recreational, and environmental water requirements (i.e., non-consumptive water requirements for the general public enjoyment including non-resident populations of tourists to north-western California) may well exceed consumptive uses in many hydrographic areas. Thus, the project sponsor must take an active role in providing such water and must absorb the burden of expenses for such water. Greater consideration of the values of non-consumptive water uses should be given when assessing the economic feasibility of water projects.
F. Recreation land acquisition should be included in the project development, consistent with the project's purpose.
G. Land acquisition should include provisions for exchange.
H. Water quality control must be included as a specific purpose of the project.
I. Projects which result in property tax loss to local entities shall have in-lieu taxes as a part of the project costs.
J. The state must assume the non-federal recreational costs of a federal project. These costs must include the improvement of existing roads and development of roads required for the recreational development.
K. If hydroelectric power is generated by a major water project using the water resources of the county, the county should be compensated for the sale of such power.
L. Department of Fish and Game shall develop a flow release schedule to provide for the maintenance of the fishery resources and habitat. The project sponsor shall agree to provide the water for the release schedule.
B. Efforts designed to improve the anadromous fishery resources of Humboldt County streams. Specifically, the assessment of the natural capacities of the streams and identification of factors limiting production of anadromous fish.
C. The use of Humboldt County Water Resources for the development of mariculture and aquaculture, with appropriate regulations to protect the native fish populations and the general public interests.