Chapter 502.
Direct Watersheds of Lakes Most at Risk from New Development, and Urban Impaired Streams
SUMMARY: This chapter describes the criteria used to identify the direct watersheds of lakes most at risk from new development and urban impaired streams and lists these waterbodies.
1. Applicability. This chapter applies to (A) a project that requires a stormwater permit pursuant to 38 M.R.S.A. § 420-D, and (B) a development that may substantially affect the environment and requires a site location of development (Site Law) permit pursuant to 38 M.R.S.A. §§ 481 - 490.
2. Definitions . Unless the context otherwise indicates, definitions of terms in chapter 500 apply to terms used in this chapter. See "Definitions", 06-096 CMR 500.3.
3. Criteria . The criteria in this section are used to identify the direct watersheds of lakes most at risk from new development and urban impaired streams.
The criteria apply for both projects requiring a stormwater permit and developments requiring a site location of development permit, unless otherwise specifically stated.
A. Direct watershed of a lake most at risk from new development . A lake is considered most at risk from new development if it meets the criteria below. Lakes most at risk from new development are listed in Appendix A of this chapter if it is
(1) A public water supply; or
(2) Identified by the department as being in violation of class GPA water quality standards or as particularly sensitive to eutrophication based on
(a) Current water quality,
(b) Potential for internal recycling of phosphorus,
(c) Potential as a cold water fishery,
(d) Volume and flushing rate, or
(e) Projected growth rate in the watershed.
Severely blooming lakes are a subset of lakes most at risk. A severely blooming lake has a history of algal blooms, and the reduction of existing watershed phosphorus sources sufficient to eliminate those algal blooms is expected to be so difficult that the addition of new, incompletely mitigated development sources may prevent successful restoration of the lake.
B. Urban impaired streams. A stream is considered impaired if it fails to meet water quality standards because of effects of stormwater runoff from developed land. Additional stormwater treatment controls are necessary in urban watersheds of impaired streams because proposed stormwater sources in urban and urbanizing areas contribute to the further degradation of stream water quality. Impaired streams are listed in Appendix B of this rule and include all streams listed under Category 4-A or Category 5-A in the 2004 Integrated Water Quality Monitoring and Assessment Report that have urban non-point source (NPS) indicated as a potential source.
Appendix A. Lakes Most at Risk From New Development
Appendix B. Urban Impaired Streams
