9 December 1999

Airport Communities Coalition
c/o Peter J. Eglick
Helsell Fetterman
P.O. Box 21846
Seattle, Washington 98111-3846

RE: Third Runway Wetland Analysis and Mitigation Plan

Dear Mr. Eglick:

Thank you for advising us that we have additional time to provide comments regarding the above referenced proposed project at Seattle-Tacoma International Airport. In my letter to you of 29 November 1999 I commented on the project-specific mitigation proposed by the Port of Seattle (Port). Towards the end of that letter, I noted that the Port’s reliance on off-site (i.e., out-of-basin) compensatory mitigation would set a dangerous precedent for future projects planned for the project vicinity. The purpose of this letter is to address potential cumulative impacts to wetlands of the Des Moines and Miller Creek basins from these projects.

As noted in the Port’s permit application materials, more than 18 acres of wetlands will be destroyed as part of the Third Runway project, with the majority of the mitigation achieved many miles away in Auburn. Other anticipated large projects, such as the future expansion of State Route 509 and State Route 518, as well as the LINK light rail system, could each have similar impacts to wetlands in this area. In addition, there will be many smaller projects implemented in this area. The cumulative effect of the loss of so many established wetlands within a relatively small area could have serious adverse impacts on local fish and wildlife populations, even if all of the compensatory mitigation were to be achieved within the Des Moines and Miller Creek basins.

This is because many species require mature habitat to survive. To many people, the notion of "mature" vegetation is tantamount to stands of large trees. That type of vegetation is certainly important to many types of wildlife. However, there are degrees of maturity even within scrub/shrub, emergent, and other types of wetlands as well. Much of the difference between immature and mature plants occurs below ground: more established plant communities often have different soil chemistry and soil biota than new systems. Since these soil organisms occupy lower levels of the food web, all higher life forms are dependent upon them.

A sudden large-scale loss of established wetlands could cause a disproportionately high loss of some species, or at least of local populations of some species. This would be particularly true for amphibians, reptiles, small mammals, and other wildlife that cannot readily relocate from their current habitat to new habitat constructed for them (especially if the new habitat is miles away). Should this occur, local populations could face extirpation.

Add to this the potential wholesale exportation of wetlands out of the Des Moines and Miller Creek basin under the Port’s proposed mitigation plan, particularly if proponents of the other anticipated projects use the same approach, and large portions of the project vicinity could have significantly compromised populations.

As you are aware, in 1998 Adolfson Associates, Inc. conducted a brief survey of potential mitigation sites in or near the City of Des Moines. Our findings suggested that there are many appropriate mitigation sites within the project vicinity that could help maintain the biological integrity of these basins. The Port’s application materials do not recognize these in-basin opportunities, and make no mention of their project’s role in the potential cumulative destruction of the area’s wetlands during the next decade or so. We strongly recommend that this analysis be conducted prior to permitting the Third Runway project. We further suggest that compensatory mitigation for all of these projects be coordinated so that long-term adverse impacts to local biota are minimized. Until the issues noted in my earlier letter and this letter are addressed, and the analysis concerning cumulative wetland impacts completed, we strongly recommend against approval of the project.

As always, we very much appreciate the opportunity to provide this material to you. I you have any questions, please contact me at 789-9658 or at acastelle@adolfson.com. Thank you.

Sincerely,

ADOLFSON ASSOCIATES, INC.

Andrew J. Castelle, PWS, CPSSc
Director of Natural Sciences

Information supplied by the ACC.
Designed and coded by Richard T. Kennedy.
The Des Moines City Attorney would like you to read the disclaimer.
Last modified: 16 January 2000
URL: http://www.ci.des-moines.wa.us/acc/adolfson-3.html