EXH0112017889

TO: Ray Hellwig, Director, Ecology Northwest Region Ann Kenny, Ecology NWRO Shorelines and Environmental Assessment THROUGH: Kevin Fitzpatrick, Ecology NWRO Water Quality Section Manager FROM: Dave Garland, Ecology NWRO Water Quality Nonpoint Unit SUBJECT: Report of Discussion on 'Slice Model Integration' relating to "sea-Toe Airport Master Plan Update Low SWeamflow Analysis" Earth Tech, December 2000 This is to document a meeting I had on April 20, 2001 with Pony Ellingson and Crispin Prahl of Pacific Groundwater Group (PGG) regarding methods of integrating results of the 'slice model' (PGG, June 2000) over the length of the proposed 3'e runway embankment in order to provide improved estimates of embankment drainage. Pony had indicated earlier that the so-called 'slice model' actually consists of several modeli-z tools, which are linked together to provide a cross- sectional estimate of runway embankment dr_irm3e. The most important of these models are known as a-Iydrus'and 'Slice'. In general terms, Hydrus accounts for vertical percolation of water through the embankment and Slice divides the percolating water into shallow and deep recharge components and accounts for horizontal transport of infiltrated groundwater to its discharge at the embankment toe. At our meeting on April 20, Pony recommended that PGG improve the existing drainage estimate by rigorously integrating vertical infiltration over the emlmnkmem footprint using Hydrus and perform a more qualitative assessment of the horizontal Slice component. I agreed with Pony that his recomnmulation would improve the accuracy of the existing embanknmm drainage estimate and would satisfy Ecology's concerns regarding the accuracy…

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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 [...]