HomeMy WebLinkAboutSEPA EPIC-4-MISC - SEPA REFERRALS - FEDERAL PROJECTS (1982)SEPA REFERRALS
FEDERAL PROJECTS
EPIC- 4 -VIISC
0 • City of Tukwila
• ° 6200 Southcenter Boulevard
Tukwila Washington 98188
Gary L VanDusen, Mayor
2 August 1982
District Engineer
US Army Corps of Engineers, Seattle District
Post Office. Box C -3755.
4735 E. :Marginal Way So.
Seattle, WA 98124
Subject: Draft Feasibility. Report and
Draft Environmental Tmpact Statement,
East, West and .Duwamis:h. Waterway Navigation Improvement Study
Thank. you for the opportunity to comment on this study. As a. city located
within the Green River Vali ey limmedi:ately upstream from the project area,
we are concerned about the secondary influences of the proposed channel
improvement 'program on the :floodwater control characteristics of the
Green /Duwami's-h drainage basi'n.. It is our expectation that any construc-
ti:on, improvement or modi'ficati'on of the channel configuration at the
mouth of the Duwami :sh River will not diminish the flood water run --off
carrying ,capacity within the boundaries of up- stream communities such
as Tukwila. However, we do not find.in the report text any discussion of
the project alterantives' impacts on up stream drainage characteristics:;
. an •om.i::ssion which causes us some anxiety.
To assure that the document reflects adequate disclosure and treatment of
this vital topic, we suggest that the text be expanded as follows:
Al Impact on Green River Valley drain basin
Analyze : in both quantitative and qualitative terms the influcence.
of each.navi.gati'on channel improvement alternative on the
existing floodwater carrying capability of the Green River,
B) Tidal.: affects..of the project alternatives
- Section 1.02 of Appendix D, Engineering, Design and Cost
estimates states that "tidal influence extends well above (upstream)
the Federal project's head of navigation located at river mile
6.1." Tidal influences on the Green River's ability to conduct
flood waters away from the valley drainage basin are of vital
importance, expecially during seasons of peak flow. Again the
effect of each project alternative on tidal flows and resultant
effects, if any, on flooding of the Green River should be
provided.
Page -2-
District Engineer
US Corps of E.ngi,neer Seattle District
2 August 1982
C) Saltwater intrusion of upstream river reaches
- Section 3.03 (.a.1) of the E.I.S, describes the circulatory
characteristics of fresh and salt water layers within the
project vicinity. Section 4.03 of the feasibility report suggests
that the toe of the saline layer can extend as far upstream as
seven (7) river miles, placing it very nearly within the City's
borders. We wish to see the text discuss the different affects
of the project alternatives, if any, on their long -term
influence on salinity intrusion upstream and the resulting
,implications for recreation and fishery uses within the City's
planning ;area.
Sedimentation Characteristics
- On Page 36 of the feasibility report, the text points out that
a majority of the average annual sediment load is deposited in
_the upper:raaches of the project limits above the First Avenue
South. Bridge. Naturally, we are concerned that any diminution of
channel capacity closer to our city limits: will restrict the
outflow of flood waters =from the valley basin. We wish to
determine', therefore, if any one. of. the Federal project al terna=
'tives will :be more advantageous than the others in controlling
and di'stributi'ng evenly the deposition of sedimentary materials.
Agai :n, we appreciate the opportunity to comment'on this report and look
forward to your response.
Tukwila Planning Department
Brad sfins, Director
Mark Caughey:
Associate Planner
MC /'b :l k.
xc: Publ is Works
Mayor