5 Colo. Code Regs. § 1002-61.73
The provisions of 25-8-202(1)(d) and (2), 25-8-401, 25-8-501, 25-8-501.1, and 25-8-502, C.R.S., provide the specific statutory authority for the amendments to this regulation adopted by the Water Quality Control Commission (Commission). The Commission has also adopted, in compliance with 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
The definition of Regulated Small MS4 in section 61.2(90(a) and designation criteria for MS4s throughout sections 61.2 and 61.3 refer to "urbanized areas" as based on either the 1990 Census or the latest Decennial Census. This terminology and designation criteria stem from EPA Phase II stormwater rule. On June 7, 2023 EPA signed the final rule clarifying Phase II stormwater regulations regarding Census Bureau eliminating the definition of "urbanized area." Changes to EPA's regulations are limited to clarifying that the designation threshold criteria of population criteria of 50,000 people for small MS4s will remain the same. Specifically, the final rule replaces the term "urbanized area" in the Phase II regulations with the phrase "urban areas with a population of at least 50,000." This has been the Census Bureau's longstanding definition of the term urbanized areas since 1999. The Commission is replacing the term "urbanized area" in Regulation 61 throughout with "urban areas with a population of at least 50,000" for consistency with EPA and Census Bureau's terminology.
MS4 designation criteria were established in 1999. At that time and previously the Census Bureau definition of "urbanized area" was "one or more cities of 50,000 or more and all the nearby closely settled suburban territory, or urban fringes." Therefore, replacing of the term "urbanized area" with "urban area with a population of at least 50,000 people does not change the scope of the designation criteria.
In order to distinguish Phase II designation criteria from the static requirements under Phase I, the division has added, where appropriate, clarifying text that urban areas with a population of 50,000 or more people is to be based on the latest Decennial Census by the Bureau of Census. The static requirements under Phase 1 continue to refer to the 1990 Census.
Historically a request for a responsive comment period must be made within ten (10) calendar days of the close of the public comment period. Stakeholders have commented that it takes time for the division to post the public comments which limits the period for one to review and decide whether to request a responsive and rebuttal comment period. The Commission division is changing Regulation 61.5(2)(d)(i)(B)(I) to extend the time period from ten (10) to fifteen (15) calendar days. It is anticipated that the Division will seek to post received comments within the first five (5) days allowing the public ten (10) days to review and decide whether to request a responsive comment period.
This action reinstates section 61.8(2)(m) which was inadvertently removed after the 2020 Rulemaking. The 2020 Rulemaking's statement of basis and purpose in 61.73 does not discuss removing 61.8(2)(m) as this was not an indicated change in the draft final action. It was an editorial error in updating Regulation 61 post the rulemaking hearing as other sections still refer to it (e.g., see 61.8(4)).
5 CCR 1002-61.73