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<br />, <br /> <br />!:~,'='!:,:'. '-'--~-":-'-~ <br /> <br />. <br /> <br />WBcerr,Dc,' 0, ~l ::.::;0 <br /> <br />Page 6 <br /> <br />We do not believe that it would be appropriate for EPA to require "a thorough <br />description of the biota that will be protected" in all instances where ambient quality- <br />based standards are adopted. Where the limiting factor is elevated natural or <br />irreversible levels of individual pollutants, determining the attainable chemical water <br />quality is the key issue and an extensive biological evaluation of the aquatic life <br />resulting from that water quality will not add to the protection provided. <br /> <br />b. Temporary modifications to water quality standards are adopted in Colorado <br />where numeric water quality criteria adopted for a water segment are not being met <br />at present, but it is believed that better water quality is attainable within a 20-year <br />time frame. The use of temporary, modifications encourages the establishment of <br />protective long-term water quality goals, while recognizing the reality that the <br />desired water quality standards are not attainable at present. In many instances, <br />the circumstances that warrant a temporary modification are not specific to a <br />particular discharger, and it is therefore more appropriate to adopt a temporary <br />modification of the water quality standards for the water segment, rather than a <br />discharger-specific variance. This also assures that the temporary modifications are <br />documented in Colorado's water quality standards regulations. . <br /> <br />. <br /> <br />Colorado does not believe that it is necessary or appropriate for EPA to require a <br />new type of "plan and driving mechanism aimed at achieving needed water quality <br />, and habitat improvements to fully support compliance with the designated uses" <br />whenever temporary modifications to water quality standards are adopted. <br />Whenever a temporary modification is adopted, a TMDL will be required for such <br />waters since, by definition, it is not fully attaining the underlying standards at <br />present. Thus, the TMDL becomes the "plan and driving mechanism" that defines <br />needed improvements. Establishing a separate, duplicative requirement for a new <br />type of documentation in such circumstances would not be helpful. <br /> <br />Criteria <br /> <br />1. III.C. Criteria: <br /> <br />At the outset, we note that many of the new types of water quality criteria advanced <br />, by EPA are principally relevant to nonpoint sources of pollution, although there is <br />no clear legal or administrative structure in place for the application of such criteria. <br />While often providing useful new information about water quality, these initiatives <br />should not be translated into enforceable water quality standards until there is an <br />overall Clean Water Act nonpoint source strategy, that also resolves issues such as <br />TMDLs for nonpoint sources and considers !h.!l1ff~~;[q01!l~g1IDlo_nj~witfl EPA's . <br />