In addition to the applicable underlying street tree planting requirements, in the Four Corners Subarea A2 of the Large-Scale Plan Subdistrict A, trees shall also be provided along the street edge of the mandatory sidewalk widenings along West 34th Street. All such trees shall be provided for the entire length of the street frontage of the zoning lot, at maximum intervals of 25 feet. Trees shall be planted in gratings flush to grade in at least 200 cubic feet of soil per tree with a depth of soil at least three feet, six inches. Species shall be selected and installed in accordance with specifications established by the Department of Parks and Recreation. The provisions of this Section shall not apply where the Department of Parks and Recreation determines that such tree planting would be infeasible.