(a) As used in this section, the following terms shall have the following meanings:

1. (1) “Eligible housing development” means a development that satisfies all of the following criteria:

   1. (A) The development is a multifamily housing development that contains five or more residential units, exclusive of any other floor area ratio bonus or incentive or concession awarded pursuant to this chapter.

   2. (B) The development is located within one of the following:

      1. (i) An urban infill site that is within a transit priority area.
      2. (ii) One-half mile of a major transit stop.
   3. (C) The site of the development is zoned to allow residential use or mixed-use with a minimum planned density of at least 20 dwelling units per acre and does not include any land zoned for low density residential use or for exclusive nonresidential use.
   4. (D) The applicant and the development satisfy the replacement requirements specified in subdivision (c) of Section 65915.
   5. (E) The development includes at least 20 percent of the units, excluding any additional units allowed under a floor area ratio bonus or other incentives or concessions provided pursuant to this chapter, with an affordable housing cost or affordable rent to, and occupied by, persons with a household income equal to or less than 50 percent of the area median income, as determined pursuant to Section 50093 of the Health and Safety Code, and subject to an affordability restriction for a minimum of 55 years.
   6. (F) The development complies with the height requirements applicable to the underlying zone. A development shall not be eligible to use a floor area ratio bonus or other incentives or concessions provided pursuant to this chapter to relieve the development from a maximum height limitation.
2. (2) “Floor area ratio” means the ratio of gross building area of the eligible housing development, excluding structured parking areas, proposed for the project divided by the net lot area. For purposes of this paragraph, “gross building area” means the sum of all finished areas of all floors of a building included within the outside faces of its exterior walls.
3. (3) “Floor area ratio bonus” means an allowance for an eligible housing development to utilize a floor area ratio over the otherwise maximum allowable density permitted under the applicable zoning ordinance and land use elements of the general plan of a city or county, calculated pursuant to paragraph (2) of subdivision (b).
4. (4) “Major transit stop” has the same meaning as defined in Section 21155 of the Public Resources Code.
5. (5) “Transit priority area” has the same meaning as defined in Section 21099 of the Public Resources Code.

(b)

1. (1) A city council, including a charter city council or the board of supervisors of a city and county, or county board of supervisors may establish a procedure by ordinance to grant a developer of an eligible housing development, upon the request of the developer, a floor area ratio bonus, calculated as provided in paragraph (2), in lieu of a density bonus awarded on the basis of dwelling units per acre.

2. (2) In calculating the floor area ratio bonus pursuant to this section, the allowable gross residential floor area in square feet shall be the product of all of the following amounts:

   1. (A) The allowable residential base density in dwelling units per acre.
   2. (B) The site area in square feet, divided by 43,560.
   3. (C) 2,250.

(g)

1. (1) This section shall not be interpreted to do either of the following:

   1. (A) Supersede or preempt any other section within this chapter.
   2. (B) Prohibit a city, county, or city and county from providing a floor area ratio bonus under terms that are different from those set forth in this section.
2. (2) The adoption of an ordinance pursuant to this section shall not be interpreted to relieve a city, county, or city and county from complying with Section 65915.