EXH2009029221

SUBJECT: Low Streamflow Analysis, Summer Low Flow Impact Offset Facility Proposal, Seattle--Tacoma International Airport The purpose of this letter is to provide some clarifications on my letter to you dated July 23. These clarifications are a result of the discussions that occurred yesterday on a conference call between the Port, Ecology, King County, Parametrix, Aquaterra, and Floyd Snider McCarthy. Specific items for clarification are listed below. 1. On page 4, the second sentence in paragraph 2 should read, "In areas where the embankment is proposed, recharge entering the embankment was calculated using 'flat outwash grass.' " 2. The paragraph that discusses the non-contiguous groundwater contributions to Walker Creek (paragraph starting on the bottom of page 4 and continuing on page 5) contains two errors. The new impervious area is 69 acres, not 38. The effective impervious area is 59.3 acres, not 37.2. The modeling and back up are correct and consistent with these areas. 3. The sixth to the last page in the Walker Creek package entitled "Reserve Storage Vaults for Walker Creek" includes a section called "Contributing Drainage Area." This page has been revised as follows: Subbasin Vaults Area % Contribution SDW2 F 6.0 52 SDW2 F 3.5 30 Lined Area SDW2 F 2.0 18 Pond Cover Total 11.5 The modeling is consistent with this table. Seattle-Tacoma InternationalAirport AR 029221 PO. Box 68727 Seatt/e, WA 98168 USA FAX_206)8_5-57o_ 1_ Exhibit-2009 4. Additional information on the Hydrus/slice modeling of the embankment is included. This information consists of a draft figure…

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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 [...]