The purpose of this section is to provide for the reasonable use of hillsides and mountainous areas while protecting the public health, safety, and welfare by ensuring that development will not induce soil erosion, result in excessive grading, create sewage disposal problems, increase wildfire danger and slope instability, or lead to a loss of aesthetic value. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.010 Applicability.

This section implements the goals and policies of the Colusa County General Plan and sets specific standards and regulations for all grading and development of slopes exceeding 15 percent average natural slope. This section is not a base zoning classification or combining classification, however, it is applicable to all development in any zoning classification on slopes that exceed 15 percent average natural slope. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.020 Average Natural Slope Calculation.

A. For the purposes of this section, slope is defined as the relationship between the change in elevation (rise) of land and the horizontal distance (run) over which the elevation occurs. The percent slope of any given slope is determined by dividing the rise by the run on the natural slope of land, multiplied by one hundred (100).

B. Average natural slope shall be calculated by using the following formula:

The calculated average natural slope shall be rounded to the nearest whole number. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.030 General Development Standards.

A. The developable area should be located, to the maximum extent feasible, on stable land and on natural slopes which allow building without excessive cuts and fills.

B. Natural slopes having a 30 percent or greater grade should not be disturbed.

C. Access should be through lands where roads or driveways can be designed without cuts and fills, to the greatest extent feasible.

D. The area proposed for development must include suitable lands for a septic system, unless the property is connected to a municipal sewer system.

E. The design of building sites shall be done in the manner that best protects the hillsides from excessive disturbance of the terrain and vegetation. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.040 Residential Density Standards.

Residential development shall not exceed the maximum density permitted by the General Plan Land Use Designation applicable to the parcel. In addition, the following residential density standards apply:

A. No lot shall be created after the effective date of this section on which the average natural slope exceeds 60 percent, except if the lot contains a contiguous area of 10,000 square feet within which there is no slope greater than 10 percent and on which development is proposed.

B. One single-family dwelling may be built on any lot that was legally created prior to the effective date of this section, regardless of slope, provided that all other requirements of this section are met.

C. Residential density standards shall comply with the density standards shown in Table 44-5.40-1 (Hillside Residential Density Standards).

(Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.050 Grading Standards.

Grading shall respect the natural contour of the existing terrain wherever possible. The following grading standards shall apply to all land subject to this section, in addition to the grading requirements of Chapter 70 of the latest edition of the California Building Code as adopted and modified, and Chapter 9 (Land Grading and Leveling) of the Colusa County Code:

A. Grading shall be limited to building pads and access drives thereto, and extensive grading shall be discouraged.

B. Cuts in excess of 16 feet in height from top to toe shall be discouraged.

C. Where grading is necessary, the principles of contour grading should be employed:

1. Cut slopes shall not exceed two horizontal to one vertical (2:1). Shallower slopes may be required if indicated by soils and geologic investigations to be necessary.

2. Graded slopes should be rounded and shaped to simulate the natural terrain.

3. Grading should follow the natural contours as much as possible.

4. Graded slopes should blend with naturally occurring slopes at a radius compatible with the existing natural terrain.

D. Graded slopes should be screened from view under or behind buildings or by landscaping or natural topographical features wherever possible.

E. Graded slopes shall be revegetated with a mixture of grass seeds, shrubs, or other native vegetation, as recommended by the Director. Planting may be waived by the Director for slopes that, due to the rock character of the material, will not support plant growth. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.060 Drainage Standards.

All proposed drainage facilities shall respect the natural terrain, preserve major drainage channels in the natural state, and be designed in such a manner as to minimize soil erosion and to otherwise preserve the public health, safety, and welfare. The following standards shall apply to all lands subject to this section, in addition to the requirements of the Colusa County Subdivision Ordinance and Chapter 9 (Land Grading and Leveling) of the Colusa County Code:

A. To the maximum extent possible, all natural drainage courses serving major drainage areas, and containing significant perennial vegetation which may constitute a significant wildlife habitat, should remain in their natural state.

B. In the event that off-site drainage facilities will be required to handle increased runoff, interim drainage facilities which provide for no increase in peak runoff rate from a 10-year storm shall be constructed and maintained until such time as the permanent facilities are completed.

C. The overall drainage system shall be completed and made operational at the earliest possible time during construction or shall be otherwise provided for in a manner acceptable to the County of Colusa. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.070 Driveways and Access Roads Standards.

All proposed driveways and access roads shall be designed to provide convenient and safe access while minimizing the extent of grading. The following standards shall apply to all lands subject to this section in addition to the requirements of the Colusa County Subdivision Ordinance and Chapter 9 (Land Grading and Leveling) of the Colusa County Code:

A. Driveways and access roads shall enter the fronting public road or street as nearly at right angle (or radial line, if on a curve) as physical features permit.

B. Driveways shall be designed and constructed in such a manner that stormwater runoff originating on the roadway will not drain down the drive, and stormwater runoff originating on the private property will not drain down the roadway, except in the ditch or gutter line.

C. Adequate and safe sign distance shall be provided for a design speed of 15 miles per hour.

D. Wherever feasible, driveways and access roads shall be installed parallel to elevation contours and shall not cut perpendicularly across contours.

E. The maximum grade for driveways and access roads should be 15 percent.

F. Driveways entering a public road or street shall comply with all requirements of an Encroachment Permit issued by the Department of Public Works.

G. Driveways and access roads shall comply with the requirements of the Colusa County Department of Public Works. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.080 Additional Standards.

The following standards apply to the issuance of a building permit on existing parcels, as well as subdivision of existing parcels subject to this Section.

A. Development Plan. Prior to the approval of any parcel split, a development plan for all contiguous parcels under a single ownership shall be submitted and approved by the Planning Commission.

B. Water.

1. Prior to the approval of any subdivision creating five or more parcels or any parcel map creating four or fewer parcels, the proponent shall demonstrate to the satisfaction of the Director that sufficient water exists within the underlying aquifer to support the ultimate population for the lands within overlie the aquifer, or the proponent shall provide a water development plan, which demonstrates that sufficient water will be provided to the residents for domestic use and fire protection.

2. Parcels shall have a test well dug and certified to yield a minimum of five-gallons per hour for 24 hours. If feasible, the test should be conducted not sooner than one month after cessation of winter rains. (Ord. No. 765 § 2 (Exh. A) (part))

44-5.40.090 Placement of Structures.

Proposed structures shall comply with the following standards, to maintain the natural appearance of hillsides and ridgelines:

A. Each structure shall be located as follows, provided that the review authority may modify or waive these standards where it determines that a structure on the only feasible building site of an existing parcel cannot comply.

1. No part of a proposed structure shall appear silhouetted against the sky above the nearest ridge or knoll when viewed from a public street. See Figure 44-5.40-1 (Silhouetted Structure).

2. The topmost point of a proposed structure and all site grading shall be at least 30 feet below the top of the nearest ridge or knoll. See Figure 44-5.40-1 (Location of Structure Below Ridgeline).

FIGURE 44-5.40-1: SILHOUETTED STRUCTURE

FIGURE 44-5.40-2: LOCATION OF STRUCTURE BELOW RIDGELINE

(Ord. No. 765 § 2 (Exh. A) (part))