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(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.
(.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Coverage may be aggregated to any section of a subdivision provided that an equal amount is withdrawn from remaining sections and provided further that such aggregation will not cause any significant additional erosion or channel enlargement to any portion of a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). |
(a) No earth moving activity will be permitted within the watershed unless done in accordance with approved earth moving plans. These plans must be prepared by a licensed professional engineer in accordance with regulations approved by the Commission and must set forth the measures by which erosion and sedimentation are controlled. Such plans must be filed with and approved by the Commission except as follows: 507
(.1) Where the site is designated as being within Category 5 on the Impervious Coverage Map; or
(.2) Where the earth moving or additional impervious coverage will be less than 500 sq. ft.
(b) A professionally-sealed earth moving plan must be maintained on site for the duration of earth moving and construction and must be available for inspection as deemed necessary by the Commission.
(c) Where the Commission finds earth moving plans are not in accordance with its regulations, it may require the filing and approval of revised plans.
Notes
| 507 | Amended, Bill No. 130764 (approved December 18, 2013). |
L&I shall not issue any zoning or building permits unless the Commission has certified to L&I that the proposed development conforms to the requirements of this section. The Commission has a maximum of 45 days after all required documents are received to approve or disapprove the application, after which its approval will be presumed.
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