CT Stormwater Manual

The MS4 Permit refers to The CT Stormwater Quality Manual in several places.

  • Towns must require contractors, developers, and construction site operators to maintain consistency with the manual
  • The use of low impact development must meet or exceed the practiices and standards laid out in the manual
  • Disconnections of impervious cover from the stormwater system must be designed, installed, and contained consistent with the manual

The manual was published by DEEP in 2004 and amended in 2011. Recently, DEEP has released a new updated version of the Manual, to take effect on March 31st, 2024. Here is the adoption timeline for this new updated Manual:

  • September 30th, 2023: Updated Manual is Published
    • Get familiar with new Manual
    • Update local regulations authorities
  • March 31st, 2024:  Effective Date (with grace period for projects which have completed preliminary design)
    • Adopt updated guidance
    • If grace period is applicable, communicate this to review authority. Permit must be completed before grace period ends.
  • September 30th, 2024: Grace Period Ends
    • Adopt updated guidance

Online Stormwater Quality Manual

A new interactive, searchable, online version of the updated Connecticut Stormwater Quality Manual is available on the main CT NEMO site. The pdf version of the manual can be viewed or downloaded below.

stormwater quality manual cover

Entire PDF of Manual


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ch 1

Background: Ch. 1 - Ch. 3


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ch 4

Design: Ch. 4 - Ch. 13


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SWQM Appendices



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