EXH0688025785

P.O. Box 47600 • Olympia, Washington 98504-7600 {360) 407.6000 • TDD Only {Hearing Impaired) {360) 407.6006 MEMORANDUM August 9, 1999 TO: Tom Luster FROM: Jerald LaVass_, I_I.S., P.E. SUBJECT: Evaluation of Retaining Wall/Slope Alternatives to Reduce Impacts to Miller Creek, Embankment Station 174+00 to 186+00 You have asked that I review the above named report for the Third Runway at Sea-Tac International Airport. In particular, you were concerned that adverse foundation conditions might be encountered during construction that would prompt a request to disturb additional wetlands from those mapped in this proposal. You wished my opinion whether construction techniques existed to deal with such unanticipated foundation conditions and still restrict the disturbed area to the current proposed footprint. The short answer is yes, there are such techniques. These techniques generally are expensive and typically require a specialty contractor. My foregoing comments are based on limited site specific data. The report did not provide detailed logs of the foundation explorations along the wall alignment. I am relying on the Site Description section of the report on page 1-1 where it notes the presence of "'very dense glacially overridden soils at depths on the order of lO to 30 feet." Clearly, the considerable height of the wall dictates that it be founded on a dense, unyielding foundation or a structural fill that spans between such a stratum and the base of the wall. Obviously, a conventional sloped excavation 30 feet or more in depth likely would extend the area of wetlands disturbance…

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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 [...]