PARENT SESSION
TP7 - Water Quality Criteria
Chair: Canton, Steve¹, ¹ Chadwick Ecological Consultants, Littleton, CO
2:10 PM to 5:30 PM - Tuesday, 19 November 2002
Room Ballroom A

(463) Development of site-specific water quality criteria for lead and zinc in the upper reach of the South Fork Coeur d'Alene River, Idaho .

Mebane, Chris^*,1, Hennessy, Dan², Dillon, Frank³, ¹ Idaho Department of Environmental Quality, Boise, ID, USA² Anchor Environmental LLC, Seattle, WA, USA³ Windward Environmental LLC, Seattle, WA, USA

ABSTRACT- Federal (40CFR section 130-131) and State of Idaho (IDAPA 58.01.02 section 275) regulations provide for and encourage the review of existing water quality criteria, and, where appropriate, the development of site-specific criteria. In the South Fork Coeur d^'Alene River upstream of Canyon Creek, the Idaho acute and chronic criteria for lead and zinc were sometimes exceeded. However, biological monitoring data demonstrated the presence of self-sustaining populations of resident Westslope cutthroat trout (Oncorhynchus clarki lewisi) and benthic macroinvertebrate community composition similar to regional reference areas. This discrepancy between chemical and biological monitoring data supported the case for developing site-specific water quality criteria. The State^'s goal in developing site-specific criteria upstream of Canyon Creek was to allow better management, using water quality criteria that are reflective of supported uses. Within EPA^'s dataset for deriving lead, or zinc criteria, there are few toxicity data for species resident to the South Fork, and few exposure data from tests conducted in water with quality similar to that found in the South Fork. Following a thorough review of available water quality and biological information, the study design was developed. EPA^'s resident species procedure was adopted as the foundation for our conceptual approach. The overarching approach for the study was as follows: 1) Identify resident species for testing, 2) Conduct toxicity tests with rangefinding exposures to identify the most sensitive species, 3)Conduct definitive toxicity tests with the most sensitive species, including acute and chronic exposures, 4) Conduct testing across a range of water quality conditions, and 5) Conduct metals mixture testing to verify that proposed site-specific criteria are protective in combination. The test data was used to determine acute and chronic site-specific criteria, which have been adopted by the State.

Key words: Site-specific Criteria, Resident Species, Lead, Zinc