The purpose of this class of district is to protect the open quality and preserve the natural characteristics and scenic qualities of lands in visually important locations and in accordance with the Portola Valley general plan. Any parcel in an O-A district, as established by Section 18.06.010, may be occupied by a principal use listed in Section 18.26.020 or, when authorized by the planning commission, by a conditional use listed in Section 18.26.030, together with uses accessory to such principal use or conditional use, as specified in Section 18.26.040. Use of any parcel is subject to:

A.

The provisions governing accessory uses set forth in Chapter 18.42;

B.

Parcel area, open space and bulk requirements set forth in Chapters 18.42 and 18.48 through 18.60;

C.

The off-street parking requirements set forth in Chapter 18.60;

D.

The provisions regulating nonconforming uses set forth in Chapter 18.46;

E.

The required conditions set forth in Section 18.26.050;

F.

Special building setback lines set forth in Chapter 18.58.

(Ord. 1967-80 § 1 (6401), 1967)

Principal uses permitted in the O-A district shall be as follows:

A.

Uses permitted by Section 18.36.010;

B.

Agricultural uses including horticulture, grazing, minor shelters for stock and equipment, but not including uses listed under Section 18.26.030 unless such uses are authorized by conditional use permit;

C.

Public parks and open spaces in conformance with the general plan;

D.

Temporary uses permitted by Section 18.36.020;

E.

Any other use which is determined by the planning commission, as provided in Chapter 18.38, to be of the same general character as the above permitted uses.

(Ord. 1967-80 § 1 (6401.1), 1967)

The following uses are permitted only when a conditional use permit is granted therefor as provided in Chapter 18.72.

A.

Uses permitted by Section 18.36.020;

B.

Barns and agricultural equipment storage sheds exceeding one story in height;

C.

Private and commercial recreation uses and buildings;

D.

Residential uses as provided for in the residential and combining districts shown in parentheses in association with the O-A designation on the zoning map, subject to a height limit of twenty-six feet, and when developed as a residential planned unit development;

E.

Employee housing for qualified agricultural uses as set forth in California Health and Safety Code Section 17021.6;

F.

Any other use which is determined by the planning commission, as provided in Chapter 18.38, to be of the same general character as the above permitted uses.

(Ord. 2011-390 § 9, 2011; Ord. 1981-181 § 5, 1981; Ord. 1967-80 § 1 (6401.2), 1967)

Accessory uses permitted in the O-A district shall be as follows:

A.

Uses permitted by Section 18.36.030;

B.

Signs as provided for in Chapter 18.40.

(Ord. 1967-80 § 1 (6401.3), 1967)

A. All uses and structures shall be subject to architectural and site control commission approval as provided in Chapter 18.64.

B.

All uses and activities conducted in the O-A district shall be consistent with the purpose of the district, and the following uses and activities are prohibited unless specifically authorized by the architectural and site control commission as part of a building or site development project:

1.

Removal of vegetation, other than poison oak, from more than five percent of the area of any parcel;

2.

Removal of living trees with a trunk having a circumference of over twelve inches measured four feet above the surface of the ground;

3.

Excavation or filling or any combination thereof totalling in excess of twenty-five cubic yards on any parcel;

4.

Disturbance of the surface of the ground exceeding five percent of the area of any parcel;

5.

Dumping of refuse.

C.

Properties identified on the Flood Insurance Rate Maps shall comply with the provisions of Chapter 18.32.

D.

Properties with historic resources as identified in the historic element of the general plan shall comply with the provisions of Chapter 18.31.

E.

All recycling and trash enclosures shall conform with the requirements set forth in Section 18.37.010.

(Ord. 1994-279 § 2 (part), 1994; Ord. 1994-276 § 4 Exh. A (part), 1994; Ord. 1979-166 § 18, 1979; Ord. 1967-80 § 1 (6401.4), 1967)