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<br /> m, Retention o6 Runo66 6nom Tndu4tniae S.rtee - On aites deveeoped
<br /> Son .tnduatkiat. putpozea IL.e., u6e.6 invoeviilg the manu6actwruig,
<br /> I pn.ocebding, cneati.ng, nepaiaing, •tenovati.ng, painting, awning,
<br /> on aaaeinbLing o6 gooda, mevr.cluuidi.ee, on equipment), ne•ten.tion o.t
<br /> detention aneaa meeting the etandatde set 4onth in bubeec-ton j.
<br /> aha.CC be coed to irwune that nuno46 •i.e neta.ined on the aite be4one
<br /> ? being neeea4ed. The pwtpo'e o6 thib nequiaement t to inzune -that,
<br /> not on.ey wi.et the e.tandand det 6onth in aubaeeti.on 9a. be met, {
<br /> but aL6o a meehaniem wiU be pnovfded to ea4eguand the wa tenbhed
<br /> kaga.ut t the .ep.i.etage o6 .toxic on dangenoub eubbtanee.6. I,
<br /> e Section 9 Permanent Downstream Protection of Stream Banks and Channels
<br /> i Provision shall be made for permanent protection of off-site stream banks ..
<br /> and channels from the erosive effects of increased velocity and volume of
<br /> • fi,
<br /> c stormwater runoff resulting from land-disturbing activities.
<br /> S iI
<br /> a. ContnoZ o6 'O.Lbciuvcge - pnov.i4ona aha.ee be made eon the carctnoZ oe i
<br /> dtonmuatet discharged son the typed o6 devetopment az bpeci.4•ced i
<br /> I below. A4tet deveZopnierut o4 the a.cte, the peak di change o4
<br /> etonmuxlten nuno44 ne6ueting 4nom a ten-yea& etonm bha Z be no
<br /> greaten than that which wowed nesuet 4nom a ten-year atonm on the
<br /> ', F Game aite pn.inn to deve.eopment. .ThJ.o negwiaelnent ahat.e apply to:
<br /> 1 1. Cormnet:Riae, .i.nduat,ia.e, o54i.ce, and •inatitutionat deveeopmenta
<br /> j, 2. Muett:-'6ami,2y ne6•i.dentine deveZgpmen o4 mone tluut 10 unit& !
<br /> 1 3. Singt.e-6ami,ey detached ne a identia.L deveeopmenta where mone than
<br /> i 3 .eoth are to be cheated.
<br /> E b. Control of Velocity - stream banks and channels downstream from any
<br /> land-disturbing activity shall be protected from increased degradation
<br /> 1 by accelerated erosion caused by increased velocity of runoff from a
<br /> land-disturbing activity. The land-disturbing activity shall be
<br /> planned and conducted such that the velocity of stormwater runoff in
<br /> the receiving watercourse at the point of discharge resulting from
<br /> _. { a 10-year storm after development shall not exceed the greater of:
<br /> k 1 (i) the velocity as determined from the table in (F) of this rule, or
<br /> ' (ii) the velocity in the receiving watercourse determined for the i`•
<br /> 10-year storm prior to development.
<br /> ,
<br /> If conditions (i) and (ii) of this paragraph cannot be met, the channel i
<br /> i below the discharge point shall be designed and constructed to withstand
<br /> the expected velocity. .
<br /> 1) Acceptable Management Measures - measures applied alone or in
<br /> combination to satisfy the intent of this subchapter are acceptable
<br /> if there are no objectionable secondary consequences. Innovative
<br /> techniques and ideas will be considered and may be used when shown
<br /> to have the potential to produce successful results. Some alternatives
<br /> are to:
<br /> (i) avoid increases in surface runoff volume and velocity by
<br /> including measures to promote infiltration to compensate for
<br /> increased runoff from areas rendered impervious;
<br /> (ii) avoid increases in stormwater discharge velocities by using
<br /> vegetated or roughened swales and waterways in lieu of closed
<br /> 1_ drains and high velocity paved sections;
<br /> ,I (iii) provide energy dissipaters at outlets of storm drainage 1
<br /> facilities to reduce flow velocities at the point of discharge; is
<br /> • these may range from simple rip rapped sections to complex
<br /> • structures:
<br /> w iv) protect watercourses subject to accelerated erosion by improving
<br /> I cross sections and/or providing erosion-resistant lining. I
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