Smaller Site Development

Stormwater Requirements

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The Regulation Requirements

The Regulation

These are stormwater regulations for developed or redeveloped smaller sites that were previously exempt. 

  • Lots less than one acre used for single family/duplex dwelling 
  • Less than half an acre used for any other purpose 

These lots are now subject to maximum impervious surface limitations by zoning district. 


  • Grandfathered lots and subdivided lots that meet their applicable Use Standards will be exempt from Active Stormwater Control Measures provided they stay under the Zoning District Maximum Percentage of Impervious Surface Coverage;
  • Grandfathered lots include any lot recorded prior to May 1, 2001 and residential lots created by a subdivision of one acre or less in aggregate size approved after May 1, 2001;
  • Development of lots qualifying for an exemption that exceed new impervious limitations are required to either:
    • Demonstrate that post-development volume of stormwater leaving the site is equal to or less than the volume of stormwater leaving the site under the maximum percent impervious limitation (or existing impervious, whichever is greater) for the lot; or
    • Provide a stormwater impact analysis to show that there will be no adverse impact on downstream properties during the 2, 10, 25, 50, and 100 year storm events;
  • Any lot with a detached single-unit living or attached two-unit living home in existence as of November 27, 2016 is entitled to a one-time 400 square foot increase of impervious surface area.
  • Substitution of impervious surfaces is still a qualifying exemption.



Ben Brown, PE
Stormwater Administrator 

Engineering Services
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Stormwater Permitting and Inspections Requirements



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