Notes
King County Department of Natural Resources draft review comments (AR034844-034846) on the Port Of Seattle / Parametrix Inc. December 2001 Low Streamflow Analysis – Summer Low Flow Impact Offset Facility Proposal. Review evaluates HSPF hydrologic modeling, impact assessment, and conceptual design of low-flow offset facilities for Miller Creek and Walker Creek against Washington State Department of Ecology conditional 401 Certification and 10/30/01 facilitated meeting notes. Findings note need for additional refinements before concurrence with revised Miller Creek impact numbers and demonstration of sufficient water collection for Walker Creek. Issues identified include IWS storage lagoon infiltration as unaccounted baseflow source, groundwater storage decay coefficient inconsistencies, gauge record discrepancies, and recommendation for a validation report on revised 1994 condition HSPF models. Mitigation proposal covers 100 acres of lost pervious groundwater area. Document also references the Port’s Comprehensive Stormwater Management Plan (SMP) and Master Plan Update (MPU).