Notes
Internal email dated June 1, 1999, from Ken Ludwa to Linda Logan and Paul Fendt (CC: Brian Pippin), analyzing upstream receiving stream compliance for Miller Creek and Des Moines Creek. Using Reasonable Potential Analysis methods, Ludwa calculated 90th percentile instream copper concentrations and compared them to standards based on 10th percentile hardness values. Neither stream is in compliance: Miller Creek shows 90th percentile copper of 16.4 against a standard of 4.3 (10th percentile hardness 23.0); Des Moines Creek shows 7.5 against a standard of 6.0 (hardness 33.0). Email discusses Water Effect Ratio (WER) thresholds — WER of 2 or more for Des Moines and 4 or more for Miller — needed to achieve compliance. Also references Stream Effects Study, de-icing upstream samples, King County and City of Des Moines reports as data sources. Suggests possibility of discarding prior data if clean sampling yields lower concentrations. Document AR024560 is part of PCHB Third Runway EIS administrative record.