Admin Order 58-14-01-F - Laserfiche WebLink

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1.14 EQUIVALENT ON -SITE AREA GUIDELINES Equivalent on -site areas are existing impervious surface areas that would otherwise not require stormwater quality treatment, being an equal or greater surface area of the new or replaced impervious surface area that requires stormwater quality treatment of its stormwater runoff. When designing a stormwater quality system using equivalent on -site areas, plans shall show and identify the following information: • The new or replaced impervious surface areas which, by code, require stormwater quality treatment of its stormwater runoff. • The new or replaced impervious surface areas which, by code, require stormwater quality treatment of its stormwater runoff, but will not receive stormwater quality treatment. • The equivalent on -site (i.e. existing) impervious surface areas which will receive stormwater quality treatment of its stormwater runoff. Using the square footages from the bulleted items above, the stormwater quality treatment facilities shall be sized using either the Simplified or Presumptive Approach. The use of equivalent on -site areas to meet stormwater quality standards does not exempt new or replaced impervious surfaces from having to meet flood control, flow control, oil control, or source control standards. The redesign of existing surfaces must meet current codes, including stormwater management. Stormwater Management Manual 1 -26 Eugene 2014