Request for Site-Specific Copper StandardUpper South Platte Segment 15 Middle South Platte Segment 1a

Metro Wastewater Reclamation District

Water Quality Control CommissionJune 8/9, 2015

In 2009, the Commission adopted a temporary modification for Segment 15 based on Water Effects Ratio (WER) copper values.

WER-based copper standards were adopted for Segment 1a.

The Commission determined that appropriate site-specific standards to protect aquatic life would be better resolved through BLM/FMB approach.

Background

Upper South Platte Segment 15 at 124th Avenue

2

Replace copper table value-based standards in Upper South Platte Segment 15 downstream of Hite facility outfalls plus Middle South Platte Segment 1a with BLM/FMB site-specific standards:

35.1 g/L acute

23.5 g/L chronic

Metro’s Site-Specific Copper Proposal

3

South Platte River in Brighton, Upper South Platte Segment 15

Biweekly monitoring of 11 sites provided spatial coverage of both segments between 2009 and 2013.

Monitoring data produced a robust dataset and are representative of a variety of flows and seasonal conditions.

4

Segments 15 and 1a Monitoring

Map of South Platte River indicating copper monitoring sites

BLM/FMB modeling for each monitoring station produced a set of protective acute and chronic copper values for each station.

Statistical analyses showed that protective values were not significantly different among the 11 stations.

The most protective acute and chronic values were selected to apply to both segments.

BLM/FMB Model Results

5

South Platte River south of Brighton, Upper South Platte Segment 15

Metro’s Longevity Plan

6

Metro will continue to collect all necessary data to develop the current proposed site-specific standards.

Prior to every Regulation 38 review Metro will review and revaluate the chronic and acute copper criteria for each location.

Should significant changes in the BLM/FMB-based copper standards be revealed, Metro will work with Division staff to propose appropriate protective changes to the site-specific copper standards.

Adopt site-specific copper standards for Upper South Platte Segment 15 below Metro outfalls plus Middle South Platte Segment 1a:

35.1 g/L acute

23.5 g/L chronic

Metro will continue to monitor BLM/FMB parameters at stations throughout both segments and evaluate standards prior to every Regulation No. 38 review.

Copper Proposal Summary

7Hite Facility outfalls (upper left)

on Segment 15

Questions