(1) Legislative Finding and Purpose. Council finds that development within the Wissahickon Watershed has led to increased flooding of the Wissahickon Creek and its tributaries, and has increased the hazards of erosion, siltation and channel enlargement within the Wissahickon Watershed. To prevent such adverse conditions and the degradation of the environment, it is necessary to impose environmental controls to protect the health, safety and general welfare, to improve water quality and to achieve environmentally sound land development within the Wissahickon Watershed.

(2) Scopes. These special environmental controls shall apply within the boundaries of the Wissahickon Watershed, encompassing the area generally bounded by Ridge avenue, Schoolhouse lane, Germantown avenue, Mount Airy avenue, and the Montgomery County Line, more fully defined on accompanying Map "A." This map shall be filed with the Department of Licenses and Inspections and the City Planning Commission, and shall be available for public inspection upon request. All such controls shall supplement other provisions of this Title. These controls shall apply during and after construction and shall encompass all construction site clearing and earth moving within the Wissahickon Watershed and shall promote a regional approach to the protection of the Wissahickon Watershed.

(3) Definitions.

(a) Bank of a Surface Water Body--The land which contains a surface water body at its highest flow.

(b) Commission--City Planning Commission.

(c) Countermeasures--Any engineering, design, construction or landscaping activity undertaken to avoid environmental damage.

(d) Developed Land--Land having more than one dwelling unit per acre or having a structure or structures with an area in excess of 5,000 square feet per acre.

(e) Earth Moving Activity--Any construction or other activity which disturbs the surface of the land including but not limited to excavations, embankments, land development, subdivision development, mineral extraction and the moving, depositing or storing of soil, rock or earth.

(f) Impervious Ground Cover--Any building, pavement or other material which impedes the natural infiltration of surface water into the soil. Impervious ground cover includes but is not limited to structures, swimming pools, and paved non-permeable patios, walks, driveways, parking areas, streets, sidewalks, and any other non-permeable ground cover.

(g) Slope--The change in elevation between two points as indicated by a ratio obtained by dividing the horizontal distance between the two points into the difference in their vertical elevations.

(h) Surface Water Body--Any stream, pond, marsh or water course which drains an area of 64 acres or more.

(i) Swale--Any area of low land which drains an area of more than 20 acres and less than 60 acres.

(j) Watershed--All of the land area within the City which contributes surface water runoff into the Wissahickon Creek. Maps describing this Watershed shall be kept at the Department of Licenses and Inspections and the City Planning Commission.

(4) Special Environmental Controls. The following special environmental controls are imposed (in addition to any applicable provisions of Section 1603.1) to regulate: setbacks from water courses, construction and earth moving activity on slopes, impervious cover, and, earth moving plans.[298]

(a) Setbacks from Water Courses Within the Watershed. There shall be no new impervious ground cover constructed or erected within 200 feet of the bank of a surface water body or within 50 feet of the center line of a swale within the Watershed.

(b) Construction and Earth Moving Activity on Slopes.

(.1) Where the natural slope of land is twenty-five (25) percent or greater, no site clearing or earth moving activity shall be permitted.

(.2) Where the natural slope of the land is more than fifteen (15) percent and less than twenty-five (25) percent, site clearing or earth moving activities shall be permitted only in conformance with earth moving plans approved by the Commission.

(c) Impervious Coverage.

(.1) Basic Impervious Coverage. No building, paving, street or other impervious ground cover shall be constructed or placed on any property within the Watershed in excess of the requirements of the following categories as designated on Map "B" cited in Paragraph (4)(c)(.4):

Category 1: There shall be no impervious ground coverage in excess of twenty (20) percent of the lot area or subdivision.

Category 2: There shall be no impervious ground coverage in excess of twenty-seven (27) percent of the lot area or subdivision.

Category 3: There shall be no impervious ground coverage in excess of thirty-five (35) percent of the lot area or subdivision.

Category 4: There shall be no impervious ground coverage in excess of forty-five (45) percent of the lot area or subdivision.

Category 5: There shall be no percentage limitation of impervious ground coverage on land deemed to be developed or otherwise disturbed from its natural state, provided that parcels in excess of one-half acre may be further developed only as follows:

(.a) The increased surface water runoff leaving the site shall not adversely affect adjacent property.

(.b) The method of handling runoff on the site shall be in accord with sound engineering practices and shall not significantly accelerate on-site erosion.

(.c) Such development shall not significantly diminish the infiltration capacity of the site.

(.2) Additional Impervious Coverage. Additional impervious coverage shall be permitted by the City Planning Commission, after review and comments by the Water Department and other appropriate City agencies according to the standards and regulations adopted by the Commission and the Water Department. Such standards and regulations shall assure that:

(.a) Storm water leaving the property shall be substantially similar in effect to that under the basic impervious coverage limitation.

(.b) Countermeasures shall not require excessive or significant maintenance.

(.c) Design of countermeasures shall take account of storm water runoff that enters the property from adjacent land.

(.d) The method of handling runoff on the site shall be in accord with sound engineering practices and shall not significantly accelerate on-site erosion.

(.e) Such development shall not significantly diminish the infiltration capacity of the site.

(.3) Aggregate of Impervious Coverage. Coverage may be aggregated to any section of a subdivision provided that an equal amount is withdrawn from remaining sections and provided further that such aggregation shall not cause any significant additional erosion or channel enlargement to any portion of a surface water body greater than that allowed prior to aggregation. Any such aggregation shall not cause any significant additional erosion or channel enlargement to any portion of a surface water body greater than that allowed prior to aggregation. Any such aggregation provisions shall be included within the approved plan of subdivision.

(.4) The map designated as "Impervious Coverage Categories" shall define the areas where the restrictions imposed under this Section shall apply and is made part of this ordinance (Map "B" attached). Where a parcel crosses category lines, each portion of the parcel shall be governed by the controls applicable to that portion.

(d) Earth Moving Plans. No earth moving activity shall be permitted within the Watershed unless done in accordance with approved earth moving plans. These plans shall be prepared in accordance with regulations approved by the Commission and shall set forth the measures by which erosion and sedimentation are controlled. Such plans shall be filed with and approved by the Commission except as follows:

(.1) Where the site is designated as being within Category 5 on Map "B" cited in Paragraph (4)(c)(.4); and,

(.2) Where the site is one-half acre or less in area; and,

(.3) Where the earth moving or additional impervious coverage will be less than 500 square feet.

(.4) An earth moving plan prepared in accordance with Commission regulations shall be maintained on site for the duration of earth moving and construction, and shall be available for inspection as deemed necessary by the Commission.

(.5) Where the Commission finds earth moving plans are not in accordance with its regulations, it may require the filing and approval of revised plans.
(5) Certification and Enforcement. No building permit shall be issued unless the Commission shall have certified to the Department of Licenses and Inspections that the proposed development conforms to the requirements of this Section. The Commission must take action of approval or disapproval within 45 days after all required documents are received.

(6) Regional or Intergovernmental Cooperation. The Commission shall be empowered to work with federal, state and other local governmental agencies in implementing a regional approach to preserving the Watershed.

(7) Inter-Departmental Cooperation. The Commission shall seek advice where appropriate from the Water Department and other governmental agencies.