Except as hereinafter provided, every structure in which is conducted a principal use shall be located upon a parcel having an area not less than the minimum required in this chapter for the district in which the parcel is located.

(Ord. 1967-80 § 1 (6201 (part)), 1967)

Parcel area is the total of the area measured in a horizontal plane, within the parcel lines bounding the parcel, exclusive of:

A.

Easements for streets or driveways which are not for the exclusive use of the parcel on which any such easement is located;

B.

Any portion of an individual accessway in excess of five percent of the parcel area required in the district.

(Ord. 1967-80 § 1 (6201 (A)), 1967)

The following are recognized as parcels for the purpose of use and development under provisions of this title even though less in dimension or area than required by this title and may be used by the owner of the parcel or his successor in interest as a building site for a principal use permitted in the district provided that all other regulations for the district are complied with:

A.

Any lot or unit of land established prior to October 6, 1937 which has not been merged by the town;

B.

Any lot in a subdivision established in full compliance with subdivision regulations in force at the time, provided the subdivision map was recorded subsequent to October 6, 1937 and provided the lot has not been merged by the town;

C.

Any unit of land caused by the merger of lots or units of land by Resolution No. 1137-1985 of the town council or as may otherwise be merged by the town council.

(Ord. 1988-229 § 1 Exh. A (part), 1988: Ord. 1979-166 § 9 (part), 1979; Ord. 1967-80 § 1 (6201 (B)), 1967)

For lands included in an S-D combining district, the values set forth in Table 3, as based on the formulae given therein, apply in lieu of the values for minimum parcel areas set forth in Table 1 in Section 18.48.010. Column one, gross area per dwelling unit, shall be used for planned unit development, and column two, required minimum parcel area, shall be used in all other cases. Gross residential area is the total area devoted exclusively to the use of the residents plus all trail easements and roads rights-of-way. Net residential area is the total area devoted exclusively to the use of the residents. Where any lands in a planned unit development are in excess of fifty percent slope, such lands may be assigned a slope of fifty percent and the number of dwelling units permissible on the fifty percent and over lands may be added to the number permissible on the balance of the parcel to obtain the total permissible on the entire parcel. In other than planned unit developments, lands in excess of fifty percent slope may be considered as fifty percent in determining the average slope of the parcel.

TABLE 3—PARCEL AREA REQUIREMENTS FOR
S-D DISTRICTS*

SD-1 Districts*

*The values in this table are derived from the equations:

(1) Gross area = 1 / 0.89-0.01560S (2) Minimum parcel area = 1 / 1.0-0.01770S

where S is the average ground slope in percent.

SD-1a Districts*

*The values in this table are derived from the equations:

(1) Gross area = 1 / 0.89-0.0223(S-15) (2) Minimum parcel area = 1 / 1.0-0.0253(S-15)

where S is the average ground slope in percent.

SD-2 Districts*

*The values in this table are derived from the equations:

(1) Gross area = 1 / 0.459 - 0.0070S (2) Minimum area parcel = 1 / 0.5 - 0.0077S

where S is the average ground slope in percent.

SD-3 Districts*

*The values in this table are derived from the equations:

 (1) Gross area = 1 / 0.308 - 0.0051S (2) Minimum area parcel = 1 / 0.333 - 0.0055S

where S is the average ground slope in percent.

(Ord. 1995-285 § 1 Exh. A (part), 1995; Ord. 1989-246 § 1 (Exh. A), 1989; Ord. 1981-182 § 2, 1981; Ord. 1981-181 § 4, 1981; Ord. 1979-166 § 9 (part), 1979; Ord. 1969-99 § 1 (part), 1969: Ord. 1967-80 § 1 (6201.1), 1967)

The slope of a parcel shall be measured using the following formula and either the town topographic map, dated August 22, 1968, with a scale of one inch equals two hundred feet, or a topographic map with an accuracy acceptable to the administrative official and a scale in which one inch equals no more than two hundred feet. The formula is:

S = .00229 IL / A

(Ord. 1995-285 § 1 Exh. A (part), 1995)

A. The number of dwelling units permissible in any planned unit development shall be determined as follows:

1.

In areas within a slope density combining district, the gross residential area shall be divided by the required gross residential area per dwelling unit indicated in Table 3 for the applicable slope category;

2.

In all areas not included in a slope density combining district, the net residential area shall be divided by the minimum parcel area required for the district or combining district in which located.

B.

Where individual parcels or building sites are to be sold or leased within any planned unit development, the net area for individual parcels or building sites shall be as required by Sections 18.50.010 through 18.50.030 except as modified below:

1.

In R-E and M-R districts the planning commission may authorize the net area for individual parcels or building sites to be reduced to twenty thousand square feet if the commission finds that development results in less disturbance to the natural terrain and vegetation and produces a development more in keeping with the objectives of this title and the Portola Valley general plan than could overwise have been obtained.

2.

In R-1 districts the net area may be reduced to not less than one-fourth of that required in the combining district in which the planned unit development is located but not less than four thousand square feet in any case, provided the planning commission makes the findings required in paragraph B (1) of this section.

(Ord. 1979-166 § 10, 1979; Ord. 1971-113 § 3, 1971; Ord. 1967-80 § 1 (6201.2), 1967)

Where a planned unit development includes area in categories Pmw, Ms, Pd, Pdf, Md, Psc or Pf as shown on the Ground Movement Potential Map of Portola Valley adopted by council Resolution 2506-2010 and as thereafter amended, the maximum number of parcels permitted shall be determined by either of the two following procedures at the option of the applicant:

A.

The applicant may compute the maximum number of dwelling units permitted by procedures set forth in Sections 18.50.040 and 18.50.050 except that for those lands in one of the land movement potential categories enumerated in this section, the number of dwelling units shall not exceed ten percent of the number permitted by procedures set forth in Sections 18.50.040 and 18.50.050.

B.

The applicant may design a conventional subdivision, one for which a planned unit development is not required, pursuant to the purposes and standards of the subdivision ordinance, to determine the number of lots possible on the property. If the applicant demonstrates to the satisfaction of the planning commission that the purposes and standards of the subdivision ordinance are complied with in the design and that the subdivision could reasonably be expected to be constructed as proposed, the number of lots thus determined shall then be the maximum number permitted in the planned unit development.

(Ord. 2010-387 § 7, 2010; Ord. 1979-166 § 11 (part), 1979: Ord. 1967-80 § 1 (6201.3), 1967)