Water Quality Control Commission Hearing June 8, 2015 IN THE MATTER OF THE ADOPTION OF REVISED WATER QUALITY CLASSIFICATIONS, STANDARDS AND DESIGNATIONS FOR MULTIPLE SEGMENTS IN THE CLASSIFICATION AND NUMERIC STANDARDS FOR SOUTH PLATTE RIVER BASIN, LARAMIE RIVER BASIN, REPUBLICAN RIVER BASIN, SMOKY HILL RIVER BASIN, REGULATION 38 (5ccr 1002-38) Site Specific Mercury Standard for Segment 16i of the Upper South Platte Subbasin Water Quality Control Commission Hearing June 8, 2015

April 2013 WQCC Rulemaking Hearing Proposal In 2013, Suncor proposed a site-specific mercury (Hg) standard, based on fish tissue analysis and bioaccumulation factors to be applied below Suncor’s discharge Results Concern from the Agencies (EPA, CPW, WQCD) on data and calculations WQCC directed Suncor to collect more data Adopted “current condition” temporary modification for Hg for Segment 16i, set to expire in 2017, to provide time to resolve uncertainty about the appropriate underlying standard

In 2013 and 2014, Suncor: 2013 – 2104 Sampling Developed a Sampling and Analysis Plan approved by EPA, WQCD and CPW (“Agency’s”) Conducted fish tissue sampling for the largest fish caught during multiple sampling events over variable flow conditions and seasons Conducted monthly water column sampling for total mercury (TotHg) and methylmercury (MeHg) Collected tissue samples as skinless filets and analyzed for TotHg Submitted annual progress reports to the WQCD

Sand Creek Study Locations

Suncor’s Proposal - 2015 Rulemaking Hearing Suncor developed an alternate site-specific standard of 0.029 µg/L for total mercury based on comments in the WQCD’s RPHS, using the following data and calculations: Geomean water column TotHg concentration for Site SW2-1 (downstream of discharge) Weighted geomean fish TotHg concentration using green sunfish and common carp for Site SW2-1 Site-specific BAF using the weighted geomean fish tissue concentration and the geomean water column concentration Calculate a TotHg standard using site-specific weighted BAF and the 0.3 mg/kg fish tissue criterion

2015 Rulemaking Hearing - Agency Proposal WQCD developed an alternate site-specific standard of 0.026 µg/L, based on USGS methodology, using the following data and calculations: Mean fish tissue concentration for each species Weighted 85th percentile MeHg water concentrations from SW2-1 and SWP (upstream of discharge) Site-specific BAF for each species Utilize species with the highest BAF for MeHg (green sunfish) and calculate a MeHg standard, then translate to a TotHg water column standard Because the 85th percentile is used in the calculations, 303(d) assessment would be based on the weighted 85th percentile of TotHg data

Agreement between Suncor and the WQCD Summary Agreement between Suncor and the WQCD Suncor agrees to the site-specific standard of 0.026 µg/L TotHg The standard is protective of the 0.3 mg/kg fish tissue criterion for the highest potential for bioaccumulation Assessment should occur using the weighted 85th percentile of TotHg data from Sites SW2-1 and SWP

Questions

EXTRA SLIDES

Water Column Concentrations Total Mercury Concentrations in Sand Creek 2009-2014

Fish Tissue Concentrations Methyl Mercury Fish Tissue Concentrations in Sand Creek 2009-2014

Mercury Concentrations - Effluent Effluent Total Mercury Concentrations 2009-2014

Predicted South Platte River Concentrations Predicted South Platte River Total Mercury Concentrations

Fish Length and Abundance