EXH1208046165

FROM: Michael Bailey, P.E.,and Michael Kenrick, P.E., Hart Crowser RE: Effects on Infiltration and Base Flow Proposed Third Runway Embankment J-4978-06 CC: Paul Fendt and Jim Kelley, Parametrix In response to your request, this memo presents Hart Crowser's most recent analysis of infiltration into the proposed Third Runway embankment and related effect on the shallow water-bearing zone in native soils that provide base flow to Miller Creek and adjacent wetlands. The analysis presented in the attachment to this memo is Appendix C from Hart Crowser's pending geotechnical report on the proposed embankment (Hart Crowser, 2000). The analysis presented in the attachment is the third and most sophisticated analysis we have accomplished on potential impacts of embankment construction to base flow (see Hart Crowser, 1999 and 1998). The three Hart Crowser analyses are consistent and confirm the independent analysis accomplished by Ecology's consultant Pacific Groundwater Group (PGG, 2000). These analyses indicate that construction of the embankment is expected to reduce overall annual base flow only slightly, and the net effect is a benefit to the environment since percolation through the embankment will experience a hydraulic lag, resulting in increased base flow in the summer months when it is most needed. The analysis described in the enclosed attachment used a sequence of three models to represent the process of unsaturated flow through the embankment. • The first part of this approach is a model called Rosetta that uses moisture-conductivity- suction relationships based on gradation of the actual fill materials, to develop parameter…

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PSCAA Advisory Council Meeting Agenda
Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
1904 3rd Avenue, Suite 105, Seattle, WA 98101
Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]