December 10, 1999

Peter J. Eglick, Esq.
Helsell Fetterman
1500 Puget Sound Plaza
1325 Fourth Avenue
Seattle, WA 98101

Re: PN 96-4-02325 Revised, Port of Seattle, Sea-Tac International Airport, Third Runway Expansion

Dear Mr. Eglick:

Earlier, we (BioAnalysts, Inc.) commented on fishery aspects of the runway expansion proposed at Sea-Tac. Since then, we have read information and statements provided by other reviewers of the permit application. Some of those materials caused us to believe we should re-emphasize some of our positions. Thus, we respectfully add the following brief comments.

Our first re-emphasis involves stormwater conveyance and hydrology. We note that Northwest Hydraulic Consultants, Inc. (NHC), in a letter signed by W.A. Rozeboom and K. M. Leytham, were concerned about feasibility and performance of proposed stormwater facilities. Their concerns as specialists in hydraulic engineering, competently enhance our worries about heightened peak flows that would scour stream substrates and increase erosion (especially, see their p. 6, item 14).

The comments by NHC also reinforce our concerns about the extent of impervious surfaces. Any underestimate of the effects of impervious surfaces on peak flows becomes a concern for erosion and stability of spawning and rearing sites.

We also note possible concerns about the runway fill embankment as a source of recharge (see their p. 8, item 20) and the stability of the fill. Possible recruitment of fines from failure of the fill is a major potential problem for fish.

Based on the analysis of NHC, Miller, Walker, and Des Moines creeks will experience greater streambank erosion, which will result in increased fine sediment recruitment. This will decrease bank stability, habitat complexity, and water quality.

In summary, these changes will likely harm the habitat and production of fish in the streams and also in the near-shore environment. In light of this, we recommend against approval of the project at this time.

Please let me know if you have any questions or need further clarification.

Yours very truly,

BioAnalysts, Inc.

Tracy W. Hillman, Ph.D.

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Last modified: 16 January 2000
URL: http://www.ci.des-moines.wa.us/acc/bioanalysts-2.html