[Added 4-24-2013 by L.L. No. 6-2013]
A separate stormwater retention permit, issued by the Incorporated
Village of East Hills, shall be required for the installation or construction
of any dry well or retention system.
Any construction or alteration upon any lot that results in
an increase of impervious surface on such lot equal to or greater
than 200 square feet must include facilities for on-site retention
and discharge of stormwater runoff from the added area of impervious
surface. Impervious surfaces include roofs, driveways, patios and
athletic courts, but shall not include walkways and stoops. In instances
where runoff from new rear yard patios, athletic courts and impervious
surfaces, in the opinion of the Code Enforcement Official, will not
have an adverse affect on adjoining or down-slope properties, the
Code Enforcement Official shall have the authority to allow exceptions
to these requirements.
All new or substantially improved structures shall provide for
the on-site stormwater retention for the entire structure and all
impervious surfaces on the subject property. A "substantially improved
structure" is defined as the enlargement, replacement or alteration
of any structure, the cost of which equals or exceeds 50% of the market
value of the preexisting structure prior to the time of the improvements,
as determined by the Building Inspector of the Incorporated Village
of East Hills.
If added impervious surfaces are constructed in separate locations
and connecting the additional stormwater areas into a single retention
system is impractical, then facilities for the on-site retention and
discharge of the additional stormwater may be connected to existing
areas of impervious surface, rather than to the newly constructed
portions, providing that the area retained is equal to, or greater
than, the combined area of the added impervious surface.
A.
When runoff from added impervious surface will combine with runoff
from existing impervious surface and discharge into the same dry well
or retention system, the system shall be sized to accommodate all
runoff from the entire combined surface area.
B.
When the additional impervious surface added results in an increase
of more than 50% of existing impervious surface, runoff from the combined
surface shall be retained on site.
C.
New on-site retention facilities required shall be designed for the
on-site retention and discharge of 100% of runoff calculated on the
basis of three inches of rainfall over a one-hour period.
Where drainage is needed or required for new cellar entranceways,
emergency exits, window wells and other below-grade openings that
have the potential for stormwater entering and flooding the cellar,
such openings shall be provided with a dry well or retention system
that is separate from all other dry wells or retention systems. This
shall not prohibit combining more than one such below-grade opening
on the same dry well or retention system.
A.
All stormwater connections shall be made with SDR 35 gasketed sewer
pipe. Other rigid pipe of similar quality may be used only with prior
approval of the Building Inspector or Code Enforcement Official.
B.
Piping with a minimum diameter of four inches shall be used for each
leader. When two or more runs of pipe are combined, continuance of
such run shall be sized accordingly.
All stormwater retention systems installed which require approval
under the provisions of this article shall be inspected and approved
by the Building Inspector or Code Enforcement Official. In instances
where, in the opinion of the Code Enforcement Official, spatial constraints,
soil composition or other site conditions prevent the installation
from conforming to generally accepted practices, the Code Enforcement
Official may require alternate design and certification by a duly
licensed design professional.
