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Subject: Comments on stormwater, hydrology, and hydraulics aspects of proposed 3rd runway and related development actions at Seattle-Tacoma International Airport, Corps Reference No. 1996-4-02325. Northwest Hydraulic Consultants has been retained on behalf of the Airport Communities Coalition to provide technical reviews of stormwater, hydrology, and hydraulics elements of proposed development actions at SeaTac airport. Our comments on the November 1999 version of the project stormwater management plan and related environmental documents were submitted to Ecology and the Corps in a series of three letters dated I1/24/99, 5/3/2000, and 7/31/2000. Our comments on the August 2000 version of the stormwater management plan were submitted to Ecology (but not the Corps) in a series of four letters dated 9/7/2000, 9/21/2000, 9/25/2000, and 9/27/2000. The purpose of this lener is to record our review comments on the December 2000 version of the documents listed below. • "'Comprehensive Stormwater Management Plan; Seattle-Tacoma International Airport Master Plan Update Improvements" dated December 2000 by Parametrix, Inc. Also reviewed were the separately-bound (as Volumes 2 through 4) Comprehensive Stormwater Management Plan Appendices A through Z dated December 2000. (SMP) • "'Natural Resource Mitigation Plan; Seattle-Tacoma International Airport; Master Plan Update Improvements" dated December 2000 by Parametrix, Inc. Also reviewed were the separately-bound Natural Resource Mitigation Plan Appendices A-E Design Drawings dated December 2000. (NRMP) AR 019008 ,, "Wetland Functional Assessment and Impact Analysis; Master Plan Update lmprovemems; Seattle-Tacoma International Airport" dated December 2000 by Parametrix, Inc. (WFA) Our qualifications to perform this review were described in our…

16300 ¢hristensen road. suite 350 sacramento I A( Z_'_00/3'_ ! " ._ s...,e,w=s,,ngto.9a,aa-34,a vancouver | _xHlsrrNO_-J#(206) 241-6000 - phone edmonton (206) 439-2420 -fax I ,_ -5 "0 ,_, www.nhcweb.com seattle • M. Green February 15,2001 U.S. ArmyCorps of Engineers Regulatory Branch Post Office Box 3755 Seattle, Washington 98124o2255 ATTN: Jonathan Freedman, Project Manager Washington State Department of Ecology Shorelands and Environmental Assistance Program 3190 - 160_ Avenue Southeast Bellevue, Washington 98008-5452 ATTN: Ann Kermy,Environmental Specialist Subject: Comments on stormwater, hydrology, and hydraulics aspects of proposed 3rd runway and related development actions at Seattle-Tacoma International Airport, Corps Reference No. 1996-4-02325. Northwest Hydraulic Consultants has been retained on behalf of the Airport Communities Coalition to provide technical reviews of stormwater, hydrology, and hydraulics elements of proposed development actions at SeaTac airport. Our comments on the November 1999version of the project stormwater management plan and related environmental documentswere submitted to Ecology and the Corps in a series of three letters dated 11/24/99, 5/3/2000, and 7/31/2000. Our comments on the August 2000 version of the stormwater management plan were submitted to Ecology (but not the Corps) in a series of four letters dated 9/7/2000, 9/21/2000, 9/25/2000, and 9/27/2000. The purpose of this letter is to record our review comments on the December 2000version of the documents listed below. * "Comprehensive Stormwater Management Plan; Seattle-TacomaInternational Airport Master " Plan Update Improvements" dated December 2000 by Parametrix, Inc. Also reviewed were the separately-bound (as Volumes 2 through 4) Comprehensive Stormwater Management Plan Appendices A through Z…

Subject: Preliminary Comments (Set 3) on August 2000 Stormwater Management Plan for Seattle-Tacoma International Airport Master Plan Update Improvements. This letter is our third installment of preliminary review comments on the August 2000 Stormwater Management Plan, and should be read as a continuation of our letters dated September 21, 2000 and September 25, 2000. As explained in the first installment, our comments are being provided on an incremental basis because of delays in our being provided the SMP and the lack of adequate time to .... - provide comprehensive review comments. This letter focuses on the SMP's failure to address basin boundary, modifications as required in the Governor s Certification for this project, and on problems with SMP assumptions/reliance on future modifications to the airport's Industrial Wastewater System (IWS). No Demonstration of Compliance with Governor's Certification The Governor's Certification tbr this project includes the lbllowing requirement: "'The Port of Seattle will design and construct the third runway such that the project will not cause changes in the location of the hydrologic divide between Miller and Des Moines Creeks in a manner that alters the average instreom flow of either creek, " The SMP does not demonstrate that this requirement is met. The title on SMP Volume 2-Appendix A, "'Hydrologic Evaluation of Stormwater Drainage Basin Changes..." gives a misleading description of the contents of that document. Nowhere in the SMP is there a complete description of the proposed basin changes or an assessment of how basin changes would afti_ct the average…

A 16300 christen,senroad. Suite350 vancouver I EXHIBIT NO_ "y')_/ I seattle, washington98188-3418 edmonton • ..?_._-c.:. I (2o6)241-eooo._ seattle • M. Green(206) 439-2420 - ILX September27, 2000 Mr. GordonWhite ProgramDirector ShorelandsandEnvironmentalAssistanceProgram WashingtonStateDepartmentof Ecology 300 Desmond Drive SE Lacey, WA 98503 Subject: Preliminary Comments (Set 3) on August 2000 Stormwater Management Plan for Seattle-Tacoma International Airport Master Plan Update Improvements. This letter is ourthird installmentof preliminaryreviewcommentson theAugust 2000 Stormwater ManagementPlan, and shouldbe readasa continuationof ourlettersdatedSeptember21, 2000 and September25, 2000. As explainedinthefirst instaJlment_ourcommentsarebeingprovidedon an incrementalbasisbecauseof delaysin ourbeingprovidedthe SMP andthe lack of adequatetime to providecomprehensivereview comments. This letter focusesonthe SMP's failureto addressbasinboundarymodificationsasrequiredin the Governor'sCertificationI for thisproject,and on problemswith SMP assumptions/relianceon future modificationsto the airport'sIndustrial WastewatexSystem(IWS). No Demonstration of Compliance with Governor's Certification The Governor's Certification for this project includes the following requirement: "'ThePort of Seattle will design and construct the third runway xuch that the project will not cause changes in the locat_on of the hydrologic divide between Miller and Des Haines Creeks in a manner that alters the average instream flow of either creek." The SMP does not demonstrate that this requirement is met. The title on SMP Volume 2-Appendix A, "Hydrologic Evaluation of Stormwater Drainage Basin Changes..." 8ires a misleading description of the contents of that document. Nowhere in the SMP is there a complete description of the proposed basin changes or an assessment of how basin changes would affect the average flows of the receiving streams. ILetter dated June 30, 1997, from Governor Gary Locke to Rodney Slat, r, Secretary, U.S.…

Subject: Preliminary Comments (Set 2) on August 2000 Stormwater Management Plan tbr Seattle-Tacoma International Airport Master Plan Update Improvements. This letter is our second installment of preliminary review comments on the August 2000 Stormwater Management Plan, and should be read as a continuation of our letter dated September 2 l, 2000. As explained in the first installment: our comments are being provided on an incremental basis because of delays in our being provided the SMP and the lack of adequate time to provide comprehensive review comments. This letter focuses on project impacts to stream base flows and seepage flows to wetlands. The current SMP does not adequately assess project impacts and does not demonstrate that there will be appropriate mitigation for predictable project impacts. These are not new concerns. The August 2000 SMP continues to provide conflicting information which fails to consistently recognize the impacts and consequently fails to propose sufficient mitigation. We recently questioned the Port's commitment to base flow mitigation and preservation of seepage flows during a meeting with Ecology on August 3, 2000 with follow-up by an email on August 7, 2000 from Bill Rozeboom to Eric Stockdale as follows: At our meeting last week, you asked me to provide something in writing to supplement my statement that the present design offers no assurance that seepage flows will be preserved to wetlands below the proposed 3rd embankment. My statement is based in part on the following text which is in the public record from the Port's March…

northwest hydraulic consultantSsacramentoinC. ]I16300 christensenroad, suite350 vancouver | EXHIBIT NO:2_'_,_seattle,washington98188-3418 edmonton | ,2.5-0._(206) 241-6000 - phone(20e)439-242o- tax seattle • M. Green September 25, 2000 Mr. GordonWhite ProgramD.'ector Shorelands and Environmental AssistanceProgram Wasl_gton State Department of Ecology 300 Desmond Drive SE Lacey, WA 98503 Subject: Pre"luninaryComments (Set 2) on August 2000 Stormwater Management Plan for Seattle-Tacoma International Airport Master Plan Update Improvements. This letter is our secondinstallmentofpre"hminaz7reviewcommentson the August 2000 Stormwater ManagementPlan, and shouldbe readasa continuationof our letterdatedSeptember21, 2000. As explainedin the first installment,our commentsare being provided on an incrementalbasisbecauseof delaysin our being provided the SMP andthe lackof adequatetime to provide comprehensivereview comments. This letter focuseson projectimpactsto streambaseflows and seepageflows to wetlands. The current SMP doesnot adequatelyassessprojectimpactsand doesnot demonstratethat there will be appropriate mitigationfor predictableproject impacts. Theseare not new concerns.The August 2000 SMP continuesto provide conflicting information which failsto consistentlyrecognizethe impactsand consequentlyfailsto proposesufficientmitigation. We recentlyquestionedthePort's commitmentto baseflow mitigationand preservationof seepageflows duringa meetingwith Ecology on August 3, 2000 with follow-up byan email on August7, 2000 from Bill Rozeboomto Eric Stockdaleas follows: At our meeting last week, you asked me to provide something in writing to supplement my ytatement that the present design offers no assurance that seepage flows will be preserved to wetlands below the proposed 3rd embanlonent. My statement is based in part on the following text which is m the public record from the Port's March 10, 2000 response to 401/404 comments... In the text which follows, the part of greatest relevance to your concerns is the part which reads,…

Subject: Preliminary Comments (Set 1) on August 2000 Stormwater Management Plan for Seattle-Tacoma International Airport Master Plan Update Improvements. Northwest Hydraulic Consultants (nhc) has been retained on behalf of the Airport Communities Coalition to provide a technical review of stormwater facilities and related streamflow impacts from the proposed 3rd runway development at SeaTac airport. By a letter dated November 24, 1999, we provided our initial comments from our technical review of the November 1999 version of the Stormwater Management Plan (SMP) for Master Plan Update Improvements at Seattle-Tacoma International Airport. Substantive follow-up concerns were presented in our email of 4/4/2000 and letters of 5/3/2000, 7/31/2000, and 9/7/2000. Our technical comments and concerns have been consistently corroborated by King County and Pacific Groundwater Group under separate contracts to Ecology. The purpose of this letter is to provide our first set of preliminary comments on the August 2000 version of the project Stormwater Management Plan (SMP). Our comments are being provided on an incremental basis because of delays in our being provided the SMP and the lack of adequate time to provide comprehensive review comments. We were advised by Ray Hellwig during a meeting on September 6, 2000 that a decision on the Port's 401 Certification application ." might be made by Ecology at any time after September 15, 2000. Please take the time to consider this letter and the subsequent letters which will follow in this series. The August 2000 SMP is a half-foot thick, 17-pound document. An incomplete version of…

Subject: Pr_ Comments (Set1) on August 2000 Stormwater Management Plan for Seattle-Tacoma InternationalAkpon Mas_ Plan Update Improveo_.nts. NorthwestHycL"au]JcConsultants(rdtc)h_ bee_retainedonbeha]fof the Airport Commumti= Coalitionto providea techmca/reviewof stormwaterfacilitiesa_ relatedstreamflowimpactsfrom the proposed3rd runwaydevelopmcmatSeaTacairport. Bya letterdstedNovember24, I999, we provided our ;.;_,,I commea_fi'omour tet.hnicalreview of the November 1999version of the Stormwaterl_/_a_gememP[an($1v_) for MasterPlanUpdateImprovementsat Seattle-Tacoma Intermtion=lAirport. Substantivefollow-upo0n_rm werepresentedin our emailof 4/4/2000 and lettersof 5/3/2000,"//31/2000,and9///2000. Ourtecknicalcorrummtsandconcernshavebeen consJste_lycorroboratedbyKing Com;tyand Pacific C-rou=lwaterGrouptraderscpar-4tecontractsto Ecology, The purpose of thi, letter is to provide our firstsetof pr"¢hminarycommentson the August 2000 version of the project Stormwater ManagementPlan (SMP). Our comments are being provided on an incrementalbasis because of ddays in our being providedthe SMP and the lack of adequate time to provide comprehensive review commmtts. Wc were advisedby Ray Hdlwig duringa meeting on September 6, 2000 that a decision on the Port's 401 Certificationapplicationmight be made by ]Ecology at amytime a_terSeptember15, 2000. Plea_ takethe dineto considerthis lettef and the subsequ¢,_t letters wkich will follow in this series. TheAugust2000SMP isahalf-footthick,1T-pounddocument.An incompleteversionoftheAugust 2000gMP wasfirstrel¢asedtotheACC forpublicreviewonAugust29,2000. ColorcopiesofSMT color-coded figures were released to the ACC for publicreview on September 7, 2000, and SMP errata pages andsupplemental analyses were released to the ACC for public review on September 13, 2000. King County fired review comments on the August 2000SMP were submitted to Ecology and m'_ultancouslyreleasedtothe Ace onSeptember15,2000. - The time fTamebetween our receipt of the Au!past2000 SMP document andthe deadline for a decision byE_olob---yon401 C¢rt;_:;oatior_is=tot=u_:;¢i-ntfor =tthoroughorc_mpletereview of thelatestS_v[P RIVER ENGINEERING , NT3RAt.'L|C MO_EL TE$71NG / N_'OR==UI.=C ANALYSIS AN0 OEgIGN / COASTAl. k'kG|N|E_IINQ _YOROEO(_Y .' tl[OtMI; NTATIOht Ir NGINE…

Subject: 401 Certification for Seattle-Tacoma International Airport. Dear Mr. Hellwig: Further to our meeting yesterday afternoon, we would like to briefly summarize the main findings to date of our review of the August 2000 "Preliminary Comprehensive Stormwater Management Plan Seattle-Tacoma International Airport Master Plan Update Improvements" (SMP). Please note that we only received our copy of the four-volume SMP on Friday August 31 and to date have only made a very preliminary and incomplete review of these documents. Further review comments will be forthcoming. We understand that Ecology will be making a preliminary determination today regarding the adequacy of the Port's submittals for making a decision on 401 Certification, and we are submitting these incomplete comments for your consideration in making that determination. Also, we would like to record our objections to both the delay in Ecology providing copies of the SMP to the Airport Communities Coalition and to the lack of adequate time for us and others to provide review comments. Our preliminary comments to date are as follows: 1. Anticipated impacts on base flows Volume 1: Section 6.2.1 - Predicted Baseflow Impacts Volume 4: Appendix F - Evaluation of Potential Base Flow Impacts There appear to be significant discrepancies or inconsistencies in the evaluation of the project's base flow impacts. It appears that the analysis presented in Appendix F does not rely on the same hydrologic model parameters as used elsewhere in the SMP. Most significantly, the base flow impact analysis appears to have relied on hydrologic model…

_e_-07-OO _2:55P northwesi: hy_rauli{ ¢ontU 206 439 24Z0 P.02 northwest hydraulic consultantssacramentoinc. 16300ch_Nmlen toad.Suite3S0 VaNCOUVer ..me,,._.,_Jn_:o._1u-_, s edmonton (20@241"6000"ohone (206}4]9-2420- fl_ seattle September 7, 2000 Mr. Ray Hel[wig ILegion_l DLrector Northwest ResJonal OfBce Waddn&,toa State Depa_xment of Ecology 3190- 160t.h Ave. SE Bellevue, WA 98008-5452 Subject: 401Cemficat.ion for Seattle-Tacoma International Airport. - Dear/Ca. HelIwig: Further to our meeting yesterday edtemoon, we would Liketo briefly summa.,ize the main findings to date of our review of the August 2000 "PrelJminL5,ComprehensiveStormwater Management PJ_n Seat'Je-Tacoma I.nternational Airport Master Plan Update Improvements" (SMP), Please note that we onlyreceivedourcopyofthefour-volumeSI_PonFridayAugust31 andtodatehaveonlymade a verypreli_naryand incompletereviewofthesedocuments.Furtherreviewcomments willbe forthcoming We understandthatEcology will bemaking aprelimina_ determinationtodayregarding theadequacy of the Port's subrmttals for making a decision on 401 Certification, and we are submitting these incomplete cornmemsfor your considerationhamakingthat determination. Also. we would like to recordourobjectionstoboththedelaym Ecologyprovidingcopiesof theSMP totheAirport Communities Co=die,onand to the tack of adequate time for us and others to provide review cozntT_r_ts. Our preliminary commentstodate are asfollows: 1. Anticipated impacts on base flows Volume 1." Section 6.2. ] - Predicted Baseflow Impacts Volume 4: Appendix F - Evaluation of Potential Base Flow Impacts Thereappeartobesignificantdiscrepanciesor inconsistenciesintheevaluationoftheproject'sbase flow impacts. It appearsthat the atudysispresented in Appendix F does not rely on the same hydrologicmodel ptrametessasusedelsewherein the SM:P.Most significantly, the baseflow impact a,'udysisappears:ohavereliedonhydrologicmodelparametersforthefillembanXmentwniclaare AR 018968 '_ _!_!E S_D " , R._D_,E/, ., -07'O0(THU! [c !7 +;063402524 F C03 0l:-C1-2_0_O_:22_e _:r:m-i_ELSEL"" ' ._V,.N 4Gl=',?-6an ; C;3/0_5 F-6211 Sap-07.00 12:B6P northwest hjtarauli¢ consu 206 439 2420 P.03 September 7,2000 oftheHSPI=modeltoac&ua/_embankmentrunoi_'daza.We haveattemptedtorepeattheanalysis presented LnAppendix 1_ using the…