§ 14-510. /WWO, Wissahickon Watershed Overlay District.

(1) Purpose.

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 regulations to protect the health, safety, and general welfare, to improve water quality, and to achieve environmentally sound land development within the Wissahickon Watershed.

(2) Applicability.

The /WWO district regulations apply during and after construction and to all construction site clearing and earth moving within the Wissahickon Watershed and will promote a regional approach to the protection of the Wissahickon Watershed.

(3) District Boundaries.

These special environmental regulations apply within the boundaries of the /WWO, Wissahickon Watershed Overlay district, encompassing the area generally bounded by Ridge Avenue, Schoolhouse lane, Germantown Avenue, Mount Airy Avenue, and the Montgomery County Line, as shown on Wissahickon Watershed Overlay Map of § 14-510(4) (Wissahickon Watershed Overlay Map).

(4) Wissahickon Watershed Overlay Map.

The Commission shall maintain the official Wissahickon Watershed Overlay map and make the map available to the public for inspection during normal business hours. The following map is provided for illustrative purposes only.

{For printable PDF version of image, click HERE}

(5) Setbacks from Watercourses. 505

(a)   There shall be no new impervious ground cover constructed or erected within 200 ft. of the bank of a stream or within 50 ft. of the center line of a swale within the /WWO overlay district. Streams and Swales that have been buried in sewer or in embedded culverts, shall be excluded.

(b)   For the purposes of this section, § 14-510 /WWO, Wissahickon Watershed Overlay District, the following terms are defined:

(.1)   Culvert.

A tunnel, typically embedded so as to be surrounded by soil, carrying a stream or open drain under a road or railroad.

(.2)   Sewer.

An underground conduit for carrying drainage water and waste material.

 

Notes

505	Amended, Bill No. 180346-A (approved July 18, 2018); amended, Bill No. 200577 (approved January 20, 2021).

(6) Impervious Coverage Regulations.

(a)   Basic Impervious Coverage.

The Commission shall establish, by regulation, an Impervious Coverage Map designating land areas within the /WWO overlay district as one of five categories of impervious coverage in order to prevent and control floods of the Wissahickon Creek. No building, paving, street, or other impervious ground cover may be constructed or placed on any property within the watershed in excess of the requirements of the following table:

 

Category	Limit of impervious ground coverage
1	20%
2	27%
3	35%
4	45%
5	No limit, see § 14-510(6)(b)

 

(b)   Category 5 Requirements.

There is no percentage limitation of impervious ground coverage on land deemed to be developed or otherwise disturbed from its natural state, provided that lots larger than one-half acre may be further developed only as follows:

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

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

(.3)   Such development must not significantly diminish the infiltration capacity of the site.

(c)   Additional Impervious Coverage.

Additional impervious coverage in excess of the coverage permitted by § 14-510(6)(a) (Basic Impervious Coverage), above, may be permitted by the Commission, after review and comment by the Water Department and other appropriate City agencies according to the following criteria: 506

(.1)   Stormwater leaving the property shall be substantially similar in effect to that under the basic impervious coverage limitation under § 14-510(6)(a) (Basic Impervious Coverage).

(.2)   Stormwater countermeasures shall not require excessive or significant maintenance.

(.3)   Design of stormwater countermeasures must take account of stormwater runoff that enters the property from adjacent land.

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

(.5)   Such development must not significantly diminish the infiltration capacity of the site.

(d)   Aggregate of Impervious Coverage in Subdivisions.

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 will 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 must be included within the approved plan of subdivision (see § 14-304(7) (Subdivisions and Subdivision Plats).

 

Notes

506	Amended, Bill No. 150264 (approved June 16, 2015).