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EXH AR024627: Handwritten Notes – Mixing Zones, NPDES, Regulatory Implications, Third Runway EIS

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Sea-Tac Airport
Third Runway
PCHB
Box 10

Handwritten notes outline eight key discussion points related to a mixing zone (MZ) study, including an examination of stream dynamics, regulatory questions about MZ implications under NPDES permitting, and how to weigh evidence for defensibility. The notes raise questions about whether mixing zones are appropriate at all, and whether existing regulations are flexible enough to accommodate site-specific MZ conditions. A final point flags that mixing zones near water quality listing designations will be a particularly difficult policy 'sell.'

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Notes

Handwritten notes, AR024627, listing eight numbered discussion points related to the third runway EIS and water quality regulatory issues. Topics include: USA combines restudy and range of stream dynamics; question of regulatory implication of mixing zones (MZ) and how NPDES applies and how to make it fit the process; goal is ‘weight of evidence’ not ‘chat’ defensibility; definition of ‘reasonable’; contact with Norm Glen and Kevin with possible follow-up; question of whether mixing zones are appropriate; whether other regulations (REG’S) are flexible enough to accommodate MZ for site; and MZ and WQR will be the ‘tough sell’ especially with listing. References to NPDES, mixing zones, and stream dynamics suggest water quality permitting context within PCHB third-runway proceedings.

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