For a development, enlargement or site alteration located within the Special Natural Area District, the City Planning Commission may authorize:

(a)        modification of topographic features including existing natural topography and topsoil pursuant to Section 105-421 (Modification of topographic features on Tier I sites) and modification of steep slopes pursuant to Section 105-422 (Authorization of a development, enlargement or site alteration on a Tier II site or portion of a zoning lot having a steep slope or steep slope buffer);

(b)        modification of geologic features including the relocation of erratic boulders, and the alteration of rock outcrops pursuant to Sections 105-423 and 105-424;

(c)        modification of botanic environment, pursuant to Section 105-425;

(d)        alteration of aquatic features, pursuant to Section 105-426 in NA-1, NA-2 and NA-3 Districts.

The Commission may prescribe appropriate additional conditions and safeguards to protect the character of the Special Natural Area District.