"Nutrient credit" or "credit" means a type of offsite option that is a nutrient credit certified pursuant to Article 4.02 (§ 62.1-44.19:12 et seq.).
"Offsite option" means an alternative available, away from the real property where land disturbance is occurring, to address water quality or water quantity technical criteria established pursuant to § 62.1-44.15:28.
"Tributary," within the Chesapeake Bay watershed, has the same meaning as in § 62.1-44.19:13. For areas outside of the Chesapeake Bay watershed, "tributary" includes the following watersheds: Albemarle Sound, Coastal; Atlantic Ocean, Coastal; Big Sandy; Chowan; Clinch-Powell; New Holston (Upper Tennessee); New River; Roanoke; and Yadkin.
This subdivision applies only to areas where there has been a documented prior use of nutrient credits to meet nutrient control requirements in an MS4 service area that flows to or is upstream of a water body segment for which a nutrient-related TMDL is being developed. For a TMDL waste load allocation applicable to the MS4, the Board shall develop the TMDL waste load allocation with the nutrient reduction benefits represented by the nutrient credit use being attributed to the MS4, except when the Board determines during the TMDL development process that reasonable assurance of implementation cannot be provided for nonpoint source load allocations due to the nutrient reduction benefits being attributed in this manner. The Board shall have no obligation to account for nutrient reduction benefits in this manner if the MS4 does not provide the Board with adequate documentation of (i) the location of the land-disturbing activities, (ii) the number of nutrient credits, and (iii) the generation of the nutrient credits upstream of the site at which the land-disturbing activity discharges to the water body segment addressed by the TMDL. Such attribution shall not be interpreted as amending the requirement that the TMDL be established at a level necessary to meet the applicable water quality standard.
Va. Code § 62.1-44.15:35