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Home My WebLink About03381 - Technical Information Report - Conveyance Calculations . 1 ^ Core Design,lnc. i CORE 1471 1 N E.29th Place,Svite 1 O1 Bellevue,Washington 98007 ��D ES I G N 425.885.7877 Fax 415.885.7963 www.coredesigninc.com "l:' m "� CONVEYANCE CALCULATIONS � ,, FOR LAURELHURST -DIVISION III RENTON.WASHINGTON w� ��'� �G�` �`� d f� . ' � k A r, .f..� 1 �L. �� !� .\/ .+ 1 l ' / r K _�:,r .o S32S1 j.,� •� _ �. ��C�, ��},;ti`�'s _, , ��,...� ��'ror�AL��'�'�� r.l�b� EXPIRES 12-04- Prepared by: Nathan W. Driggers,E.I.T. Project Manager: Robert H. Stevens, P.E. Core Project No.: 02U52 Date: January 2007 ENGINEERING PLANNING SURVEYING ..� .-, .. •, , 1/25/2007 I. PROJECT OVERVIEW The Laurelhurst Plat Divisions I , II and III are located in Section 15, Township 23 North, Rang 5 East W.M. near the intersection of 138th AVE, SE and SE 132"a St. in Renton, Washington. This report is in reference to Division III (See Figure 1-Appendix). The Division III portion of Laurelhurst is a site approximately 2.5 acres in size and is located northwest of Phase I. The project proposes to construct 14 single family lots with the supporting roads, curb, gutter, sidewalk and utilities. There are also proposed frontage improvements along Bremerton Ave. The existing detention/water quality pond for the Laurelhurst Plat was originally designed and approved under the "Technical Information Report for Laurelhurst— Phase I" September 2004 and amended in"The Technical Information Report for Laurelhurst—Phase II" March 2005. The Appendix, "The Preliminary Technical Information Report for Laurelhurst—Phase III" confirms that the existing detention/water quality pond, as constructed and without modifications, is adequate to maintain release rate, frequency-duration and water quality with the proposed Division III improvements. This report will show that the Division III storm drain system is adequate to convey the 100-year storm water to the connection point to the storm drain system in Phase I. II. Conveyance System Analysis and Design The storm drainage conveyance system was designed in accordance the 2005 KCSWDM to provide for sufficient capacity to convey and contain the 25-year peak flow without overtopping storm structures and the capacity to contain the 100-year peak flow without creating or aggravating a severe flooding or erosion problem. A KCRTS time series was developed showing that the 25-year m�imum storm rate was 1.75 CFS and the 100-year maximum storm rate was 2.43 CFS (See Figure 1). �� CORE ��OES•;N , � 1/25/2007 DEVELOPED CONDITIONS Com lete Summa of Areas Ground Cover Area ac) Till-Grass .69 Impervious Area 1.77 Total Area 2.46 Flow Frequency Analysis Time Series File:div3dev.tsf Project Location:Sea-Tac ---Annual Pea}c Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob {CFS} (C�S) Period 0 .843 6 8/27/O1 18:00 2.43 1 100.Od 0.990 0.588 B 9/17/02 17:45 1.75 2 25.00 0.960 1.75 2 12/OB/02 17:15 1.16 3 10.00 0.900 0.679 7 8/23/04 14:30 0.988 4 5.00 0.800 0.937 5 11/17/04 5:00 0.937 5 3 .00 0.667 0.988 4 10/27/05 10:45 0.843 6 2 .00 0.500 1.16 3 1Q/25/06 22:45 0.579 7 1.30 0.231 2.43 1 1/09/08 6:30 0.588 8 1. 10 0.091 Computed Peaks 2.21 50.00 0.980 Figure 1. KCRTS Flow Frequency Analysis. The Tailwater Elevation values for the connection points were taken directly from ' the Technical Information Report for Laurelhurst Phase I. The backwater ' calculations were performed with the 25-year design storm and with the 100-year design storm. All results from the backwater calculations show that both the 25- year design storm and the 100 year design storm are well contained in the storm drain system(See Figure 2 and Figure 3). r� C�� 1/25/2007 FIGURE II : BACKWATER CALCULATIONS O�VAMG U�IR[I.N�1IlS9'DMlION Ill INEPAAClI 05'-. NWp O/NUMtRN: o305t u�.ti�bn�toN�t: � �'fdR ENTRANCE [NTILtNCE EX1T OIITLET RILEf A��BOAfII ��NO JUf:CTfON Fl�6 PI�C MANNING'S OUTI.LT ITVLtT PVE FWW VF.LOCITY TALLWAY'CR FRI(.TION IIGL HEAD !1l:AD CONTROL COKfROL VELOCITY HEAD IIf.AD IIGDWA7ER FROM 70 PWW IlNCTH DIA. x CLEYATION ELCVAT101Y ARl:A VEL(X:ITY f1E�D ELfYA710N LO56 CLF.VATIUN LO�F LO38 ELEVATIO!�ELEVATION fIWU W55 IASS ELEVATION C■ C� Ci3 FCF:T IN VAWC ICL71 f�C�7 G F7'1 ��RC tT FEL FG[T FEE IEl.T ►EL IT.►T1 (fEf,T ?E[ FE¢ll W.bT iCET1 RIM f'.L DRAINACE SVtiTF.M M 1 CB20 EXCB19 17M1(� 22 12 U1113 3'/%.2') 3YPJ(I 074 723 n11J7^. 74Rfi3 IIU448 3`N{0 np31t6 U�)77: iWS3 1W41� 111�71: �Ilna7 UIUW 3W04 �112��A C611 C81D 1.7.7P 17A 11 11�113 JYB1�1 )�0.1 �17�1 I.2J U.O773 iNln Ir1fi(IS JWW ii��?R!. nU772 a(qlb aiwl,lw U(17)2 i�in�i5 �IOUW Jfq.06 JUI.G2 CBI CB21 1.75U fi1 I3 0012 3'79.01 399.70 �779 2.13 I1U772 �IMIUP n1:103 1q070 11�13Nfi i10772 JUnA2 �IM7.711 001�2 �IN�v/ 0lY139 iU0.P1 �la.:U CD2 C01 I1�y0 71 12 nn12 19970 JWG3 U7J t175 001A7 aMINI f1011M1 �UIE7 U.W71 U.014S SU165 i111F) ��1/1�2 �IIYMuI uIMNp 4UIfi.t J(N7A f.B3 C8: U750 Ilq 13 n1113 �Ix)h] 40:0) O7Y n.95 OAt4: aU1M �Ii1171 i0SG3 UIx�71 0.014: IOi.6S i0)R) 7.0112 u1rMN nlMMp .101� �c1n2�i JUNCTIONS 7'O DRAIIVAGE SYSTEM MI CB� CDI IfN1 lR 12 (I.al2 3'N'lU 4W.lE 117v i.37 liU1Si iplXl on35J Oul IR li.pl2ti O.U2!2 4V122 il)1.16 OIMIU u1N�fM' UINIU(1 40122 4U3l�I Figure 2. 25 Year Design Storm Backwater Calculations. FIGURE III : BACKWATER CALCULATIONS O/IVAMC: LAUIlELM1RSl'DfV6fON�l INEPARED tY: NN'D O�NUM�ER: o1p32 DESIGN tiTORM11: IOD YCAR [A17�,Y�7, ENi4Anf.'F. EXIT OII7LF.T INLET A►�ROACH SCN� NNCTION �RE ►1►E MANIVINI;'S OUTLET fNLLI' �IPE FWW VELOCTT\'TAILWATLR FRICTIUN HCL HEAD HLAD COIYTIIOL (V1NTR01. �'CLOCITY HEAD HGD HLADWA7l:N FRbM TO FLOW LENGTH DIA. o ELEVATION LLLYATION AR6A V[LOQTY F�AD ILLVATION 1.055 CLEVA'110N WSG LOSb [LEVKfIOti ELEV.�T70N HEAU L095 L06S ELLYAT70N l7 (7 CFB (FEF, IN VAWE C P[ 5 ►T �T/S[C FE ILL 1lF. YLEII (Ftf. E (rLE li'EE IF6LT FEET kl:F. FEE71 RIMl:L DNAINAGE SVS't'F.M M 1 CFIIf� FXCB19 2.130 27 13 OUIl i�1829 3�1MUi 0.79 3.�Y1 UI�!! )YIIhI �Ii1Xh1 17DiU 1�n7i� IIIJ�e )wl,2 1T1JU UI�BB �)147G UUINM) 79412 d1�2�++ f821 CB'.n 2�u1 128 12 U012 398.W 3Y)W ��.77 7n4 �i1�lR )9952 UN123 tfY100 ��i1ai �)IaM .IM26 I�M Oi�RR �1�M�7o �iqM10 ilNl.l7 4��?��' f'A1 CA21 2d.N1 fiJ 13 00�3 i9'7M J7�70 U.79 3.UY ��I.IPN �Ix/13 U?SI. tfn711 (1n7J� �11�R8 a1M�43 a1M1.'10 O.OI77 �I�NN7l1 �IIIn7d ai%�W a1u20 C82 CB1 IUMI 31 12 O.OII 7yI7�� iW6t U7v 112 ��OS73 lr�9p ti1122i atllM17 ppl3ti uU:73 4UIR7 a01.6J U1127) �IIKM)fl IItMM1U �Pl(•1 JM.)J C83 CB] IUNI 1�1 II 0011 �rp.63 J024J 079 172 I�OZ77 401(.1 11U719 403.fi3 VOl)h U0.71 �I�ib7 i0.1.Ir.l UU27) i1�xMM1 l��Nl(IU JlUlvl 4lk•?� JUNCTIONS TO DRAINAGE SYSTEM Nl cea cei iav 3e iz uoiz �va�u <u�ia o�y i�v QIIiM7 40090 uaae u�i.i� ou:aJ ��HR� +oiu .+otie u.aroo oam „��w auizs �o��,i Figure 3. 25 Year Design Storm Backwater Calculations. i� CORE \ �'OfSI(:N V L 1/25/2007 III. EROSION CONTROL I A sediment trap will be built at the low point of the 2.4 acre site. The sediment trap was designed using the a KCRTS time series and the 2005 KCSWDM requirements per appendix D page D-45. SA= (2 "Q2)!0.00096 SA= Surface Area at the top of the riser Q2= 15 Minute peak flow for the 2 year runoff event. Sedimenf Trap East Side of Site Required SA = 2 * (0.843) / 0.00096 = 1756 FT2 Required Designed SA= 30' x 60' = 1800 FT2 Provided �' j �� CORE \ i Pf5lGN V ti • 1/25/2007 APPENDIX � � i �� CORE \ i DFSIGN �./ t I PRELIMINARY TECHNICAL INFORMATION REPORT FOR LAURELHURST -PHASE III RENTON,WASHINGTON d�� \� `�s A. ;�� tr�y� Vd ASl-II�rQ'� � � `� �� R �� .�� ;;$']'H �`�1��'�t4L C��'ts �tR�S 12l141 � Prepared by: James A. 1V'Iorin, P.E. Project ManaQer: Robert H. Stevens, P.E. Core Project No.: 02052 Date: September 2006 LAURELHL'RST -PH�SE [II T:�BLE OF C0�1TE�TS I. PROJECT OVERVIEW...............................................................................2 II. OFF-SITE ANALYSIS ...............................................................................3 UPSTREAM TRIBUTARY AREA..............................................................................................3 DOWNSTREAM ANALYSIS...................................................................................................3 III. DETENTION FACILIIY ANALYSIS / DESIGN................................................4 HYDRAULIC ANALYSIS .......................................................................................................4 EXISTINGCONDITIONS......................................................................................................4 DEVEIOPED CONDITIONS...................................................................................................8 DETENTION ROUTING CALCULATIONS ...............................................................................11 IV. WATER QUALITY VOLUME ..................................................................... 15 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN........................................ 16 VI. SPECIAL REPORTS AND STUDIES........................................................... 17 VII. OTHER PERMITS .................................................................................. 18 VIII. ESC ANALYSIS AND DESIGN.................................................................. 19 IX. OPERATIONS AND MAINTENANCE MANUAL ............................................. ZO ! � I? � ` !I' I'.i ' � I _" I. PROJECT OVERVIEW The Laurelhurst Plat Divisions I , II and III are located in Section 1�, To�;nship 23 North, Ran� 5 East W.M. near the intersection of 138t" AVE, SE and SE 132"d St. in Renton, Washington. This report is in reference to Division III (See Figure 1-Vicinity Map). The Division III portion of Laurelhurst is a site approximately 2.5 acres in size and is located northwest of Division I. The project proposes to construct 14 single family lots «�ith the supporting roads, curb, gutter, sidewalk and utilities. There are also proposed frontage improvements along Bremerton A��e. The existing detention/«-ater quality pond for the Laurelhurst Plat was originally designed and approved under the"Technical Information Report for Laurelhurst— Phase I" September 2004 and amended in "The Technical Information Report for Laurelhurst—Phase II" March 2005. Phase III, covered under this report, is referenced as area TA1 in said reports. See Figure 2- Site Plan, for the overall site plan, the existing 2.46 acre parcel is a mixture of forest and pasture with a home and outbuilding located on the property. The original pond and water quality facility was designed under the 1998 King County Surface Water Design Mannual (KCSWDM). The City of Renton requires, for this parcel, Conservation Flow Control and the Basic Water Quality Treatment for the site as specified in the 2005 Kin�County Surface Water Desi�n Manual. The on-site generated runoff will be conveyed to the combined detention/water quality pond in the south�vest corner of the property. All drainage discharge from the pond will be conveyed via pipe to Maple«ood Creek as shown on the improvement plans for Laurelhurst Div I. This report will check the impact of these proposed improvements on the detention and «�ater quality pond already constructed for Phase I and II and recommend improvements (if needed) to the live and dead storage or the control stnicture. ' , i '�,I, �, , �, � -ST... .. ..�.. . —�-°—�—•�--•'�-,�———=°""='�'—==�.E'=�=.�-128�fM11-.�- —'-ST.:.. )t (]33A1 )a aa 1 1�0.�l !t`3 iK' / �e �i ee b ' n��l rw 1 0 4i r° 'ou J a� � D� �] ¢�; Ll � � ji I ua i� a' � - " � y'�g ❑ ��.Q � � � � a � � m._Wi G r S 3 (z) ��I � ^ o � - - _ O 2N —Q-1+ � n 'Osr.wTsoss� � � ' ioY � isas:� .�tt � � na 2 - 3 4 ' r:�; �.�, �- ,.�� ___= �n.�.� ' ' �_ �` =_____� � ,5 + . I.Is Ac. `�is I � ' I s RTIN'S ACREA TRACTI�� _ � O O O r-�sA�,�,,�1 x�m�us.cji ��a x NTON � ce� S"�CORP. � LIW7 ia�S' iZlb � � � Z�� SP.BB2065 UNREC. - �^Q o ��a�A�. u, J 0 �a, �� ,�� ;; ��I TE =- W '=== ---- - � L m � j'� tz> , - ----- u. � ��µ G O O � � . - : �.. �'' 1 ;, --- __ � —g---- -- --- L. . -� -- — - �i --- ---- (31 N` f3) /� � �SP676075 w ims �J O� - °° w n � � e� Hs ^ ',�� s'*!.�:- , C I la) � l�!' � ^ 1=1 7 io v ns: ti a Q _—_ i w �� a s 56 19 1! i7 ��.5 31 33 32 C --- :a0` .815 4 � ` D I V. 1 � u � � � � � �� F iR 3i- .76 C. sa Sas 91 �� J ' � 32 C. : '� a � _ — Y a n 3 'a �u . ' rs- 't"�� "'' $, a '1°'. Z a m <,� -- - -- -- s i 1ST . a 69�—/�, ,.� - -- -- -- <. .p 6 �c y 4� � K W�'ze Nel-16ta V �d. �W p_`� � g,� �'7 - _ �z ¢�''�� °4 �' x7 f .yb`AG� �tz 13p 17 'b2Y2�Y�Z b y��6 TI 64A. Q CU� - ti' _ a PV � � �i 8£' NEIGHBORHOOD DETAIL MAP N �" = 400'f SEC. 15, TWP. 23N, RGE 5E., W.M, N � �il'M.L: �w : �� o so ioo zoo � � f - - � � - � r - � � - � - � I I 6 I � 4 � � 3 � � ! � I 1 � � II � � - --� L _ J L - J L -J - J N�.�C CT. i' � ` i � -�� -- - -- � � � I i I I � L - - -� - J � � � i - - � - �-- - - J � i � I p - i � � - - G � i � I I I I I � � L - - -� � _ _ � �- - - --� r- - - � r-- - - � r- - - � I ° � I ' � I µ I � L - - -� L - - J L - - � � FIGURE2 � �� i �� 14711 NE�91h PI«a.#101 BN4.u�,WmMinpan 96007 125.8857877 Faa 125.8857963 �DESIGN ENGINEERING • iLANN/NG • SURVEYING � � / � � � �\ / �/ L.q URELHURST Ol �/ /// T�!�D 6T D A TE SEPT, 2006 S H E E T O F DESIGNED ✓AM 2 4 DRAWN ✓AM PROJECT NUMBER 02052 II. OFF-SITE ANALYSIS UPSTREAM TRIBUTARY AREA There is no area upstream and tributary to this site. DOWNSTREAM ANALYSIS See the downstream analysis in the Division I Technical Information report for a complete description of the downstream path from the existing detention pond. The Division III parcel has a high spot in the south east region but overall the property flows south and east into Division I of Laurelhurts. The existing ditch and pipe system along Bremerton Ave NE will be tightlined into the Div I conveyance system and then conveyed to the pond. See Figure 3 —Existing Site HydroloQy. ' I'�i�ii��l (�'i��, I'I �"�i: _ '� , i „ SEC. 15, TWP. 23N, RGESE,, W,M. �� N � sc�: �• _ �oo� o � ,� z� ---- �� ss�au[ � � � NE fo R � ``` � � � � � � �� , Q � I � � � 0o ioa ' � ------ �u::vuc ��\ \ivia uc a:ar caxv � FIGURE 3 � � � »„��%�..��a, C� e.n..�»,w�9eoo� �45.885J877 Fax 123.885J963 �DESIGN �,�� ENGINEERING • PLANN/NG • SURVEYING EX/S T/NG Sl TE H YDROL OG Y L.qURELHURST PHASE //l DATE SEPT, 2004 SHEET OF DESIGNED JAM 3 4 DRAWN ✓AM PROJECT NUMBER 02052 III. DETENTION FACILITY ANALYSIS / DESIGN HYDRAULIC ANALYSIS Tlze drainage analysis «�as modele� usillg the Kiii� County Runoff Time Series (KCRTS) sofh��are version 4.2. The site soils are Alden��ood (AgC), KCRTS Qroup, Till. The site is located in Sea-Tac rainfal] re�ion �vitl� a sale factor of 1.0. EXISTING CONDITIONS The Laurelhurst Division III property is to be modeled as forested as required by "Historic Conditions" definition Chapter 1, page 1-3 2005 K.C.S.W.D.1�1. Tllis requirement is different than the original modeling required with the older KCSWDM standard. In the original model the area was modeled as a mix of impervious, forested and pasture landcovers. To account for this difference the e�isting landcover for the predeveloped condition was revised using only forested for area TA1. See Figure 4 for a detailed tabulation of the measured areas used to produce the predevloped timeseries. This information «�as used to produce the Predeveloped Runoff T'imeseries (called PREDEV.tsfl. I ��. II � , . f �i II' ��, ,i , SEC. 15, TWP, 23N, RGE 5E., W.M, .-�� . - .. . _ . A R EA TA B U LAT I 0 N S � _. �.�_ . _ ..,e-�� , _ �` , � �, .s _� � � � -- -,, � �, � ,� +��`�`�� , PREDEVELOPED � a k:' < 6 "r . ,, .� /� � AREA Imperv. Forested Pasture Total � � - �� - -- k:,� - .� � � � � � r : � �� / TA1 0.00 2.46 0.00 2.46 � , ; � - „ _ � �� , � � � �� .. � � ;��. � . : �'`�"�: - � 43 (�.20 0.14 0.2� 0.5� n-. r 1 #t- �r � •�%'��.�:�`�` �� '� � � � �ONT 0.50 4.25 0.35 .�.�� ` . �`` ` , '�- hase i �,.03 �,35 .5.4�� 5.� ' ;. �:~� � : _ _ . - : � . : . . � = . � _ ,�� [ '� � , . .. � i r � - �. = a � , � ��• � �,,{; .r . �, ; ; �`'� �� total: 3.13 14.10 13.59 30.82 _ � Y ° � * � .�- ; �- �, �, } . � � ' ;;: • � �..� -��'� � � � � ,, i,� �_ ,�� - � ~��.�� DEVELOPED . � � �_ �� `' ` F 3' - �'� � �: ' AREA Imperv. Foresfed Grass Total t � � , - _. � .�,, � .��¢�� Y _ : ` _ ' � � , � ._ _ � TA1 1.77 0.00 0.69 2.46 � . z: � � 4 � : = � :� � � � � � .� �� r�� - � � � . �- - � . TA3 0.36 0.00 0.20 0.56 � � �� ` � �� I , ��,, �.� � -, I _ __ . . . _ ;. ` - � � , s� � � _ . �� / � - . � s � _ �.y � ; ��y - �C�S� � �..Jl/ . . .r a 1 � � , : - � _ � t U t1(.� d .�.3 �J � r . � �- � �� 1,/',P ,, �'� �. -_� �,� ; �}�-r -rt 7� '� t� , �` ��.�f�i� � � � �� f� �, �� .� � � ' � �� j� � �� .'Ps,...� :.fi, I. , � . . � - total: 21. '�' � . :� � � ��'� . 60 0.23 14.49 36.32 , �i -'� �;,F�-�',� , _ ��.�: :.��i / ��'�� - ��'� �- '� �, ��, �- �� :�.� #: �� .� F I G U R E 4 �, ��'.�'./ji�+.�'.��.�'I�.%� ,�„ '�` - , � � , -, � - __._ ,.� --� � i ..� � � � -; � r i `:� � � ' `�� . ,_ � I � � . ' .� ,a�,. �� :� � Y�► � ��` °� �- �� i �� " �� . ;� r �� ]1711 NE29thPla%#101 � �� p . � �� - �� Bsllewa.Wmhirpron 98007 il ��'� ,�`'�� 4 �, � . # DESIGN �zs.ses.�en�ass.aes.�9a3 I �.:� �- � � �. .�/,,�,, � � � � . ' ` � ` . � � * � �,,�`�r�� /� ENGINEERING • PIANN/NG • SURVEYING � __. �� $ % '� �`� � �� _ »� � R�;�~ :. r` �,. `� �� .a �� -�' -_ , '.�.:'?' •a -s - �-- � � i' � �� ^ � .�� , S/ TE L.A NO CO VER . � . � . } " � LAURELHURST PHASE //l �` ' ` � ,�r.�...fir' � �:��i�i'`.r�+f�ii�.,�'.�`��'/. � ��*��r.. `�� `# ' SCALE: 1" = 200' - � � .. �. '� f .r o i oo zoo �oo ' � "'� . DATE SEPT 2006 SHEET OF- ';_ �: . - ., ., .�- _� - --- � � +�: � _ DESIGNED JAM 4 4 DRAWN JAM PROJECT NUMBER 02052 AREA TABtiLATIONS- Predeveloped (revised TRIBUTARY AREAS Area/ Ground Cover Area (ac) AREA T1 Till-forest (per KCSWDY12005) 2.46 Till-pasture 0.00 Impervious Area 0.00 Subtotal: 2.46 AREA T2 Till-forest 0.23 Till-pasture 1.35 Impervious Area (measured) 0.�2 Subtotal: 2.10 AREA T3 Till-forest 0.10 Till-pasture 0.26 Impervious Area(measured) 0.20 Subtotal: 0.56 Tributarv Area Totals Till-forest 1.03 Till-pasture 2.99 Impervious Area (measured) 1.10 FRONT (Frontage) Area (ac) Till-forest 0.25 Till-pasture 0.35 Impervious Area(measured) 0.50 Total: 1.10 ONSITE (Phase I +II) Area (ac) Till-forest 11.06 Till-pasture 11.63 Impen-ious Area(measured) 191 Total: 24.60 PREDEVELOPED CONDITIONS Total area= 30.82 ac (Complete Summary of Areas) Ground Cover Area (ac) Till-forest 14.10 Till-pasture 13.59 vnpervious Area (measured) 3.13 See the KCRTS calculations in the Appendix for the detail I � , '� � I ` III �' � � ,' ' ' PREDEVELOPED TIMESERIES (revised) Flow Frequency Analysis Time Series File:PREDBV.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 2.37 2 2/09/O1 15:00 4 .13 1 100. 00 0 .990 1.26 7 1/05/02 16:00 2 .37 2 25. 00 0.960 � 2.32 3 2/28/03 3:00 2.32 3 10. 00 0.900 i 0.841 8 8/26/04 2:00 2 .25 4 5.00 0.800 � 1.37 6 1/05/05 8:00 2 . 09 5 3 .00 0.667 �' 2 .25 4 1/18/06 16:00 1.37* 6 2 .00 0.500 2 .09 5 11/24/06 4:00 1.26 7 1.30 0.231 4 .13 1 1/09/08 6:00 0.841 8 1.10 0.091 Computed Peaks 3 .54 50.00 0.980 *Allowable release rate = 1/2 x (1.37) cfs = 0.68 cfs I ._��n��ll��:� ��' � ,.�. III �, ;� �� EAST BASIN TIMESERIES PREDEVELOPED CONDITIONS Total area= 5.50 ac ' East Basin Ground Cover Area (ac) Till-forest 0.50 Till-pasture 4.75 Impervious Area (measured) 0.25 Flow Frequency Analysis Time Series File:$ASTBASIN.tsf Project Location:Sea-Tac , ---Annual Peak Flow Rates--- --Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.405 2 2/09/Ol 15:00 0.728 1 100 .00 0. 990 0.186 7 1/05/02 16:00 0.405 2 25.00 0. 960 ' 0.392 3 2/28/03 3:00 0.392 3 10.00 0. 900 0.083 8 8/26/04 2:00 0.372 4 5.00 0. 800 0.223 6 1/05/05 5:00 0 .354 5 3 .00 0.667 0.372 4 1/18/06 16:00 0.223 6 2 .00 0.500 0.354 5 11/24/06 4:00 0.186 7 1.30 0.231 0.728 1 1/09/08 6:00 0.083 8 1.10 0.091 Computed Peaks 0.620 50 .00 0.980 � <�l�l�i:�'�i��l ! ��, II� !'' � t�i � DEVELOPED CONDITIONS The developed site will consist of 14 lots. The impervious area for the plat was determined by measuring the right of way area which is 100% impervious and adding 4,000 SF per lot. Phase III (Area TA1): measured rh�=0.48 Ac Impervious area= [14 x 4000]/43560+ 0.48 = 1.77 Ac Grass area=2.46 — 1.77 = 0.68 Ac Area TA3: Area TA3 is a parcel east of the existing pound on the south end of Laurelhurst ' Div I. This are was unimproved during the original pond design but now has a 4 ' lot design. The developed areas modeled for the pond with Div III will be revised to reflect the development of the parcel. The areas modeled are: '� Impervious Area=41ots at 4000 SF/lot= 0.36 Ac Grass= 0.56—036 = 0.20 Ac Below is a summary of the areas, see Figure 4 for a detailed tabulation of the measured areas. Note that the 5.50 area on the east side of Phase II is included in � the developed timeseries. This information was used to produce the Predeveloped Rimoff Timeserie�s (DEV) in the KCRTS program. The entire east basin (�.�0 ac) ��-ill be directed to the �vest basin in the de�-eloped state. The difference beri�-een the predeveloped area (�0.8�) and the developed area (36.3? ) is tl�e� 5.�0 acres. I ;��i��;�'�I'i�, -� ' ;i ,�I' !' �t � � AREA TABULATIONS (revised) I! TRIBUTARY AREAS ' Area/ Ground Cover Area (ac) AREA TA1 Till-forest 0.00 Till-grass 0.69 Impen-ious Area 1.77 'ii Subtotal: 2.46 ', AREA TA2 I Till-forest 0.23 Till-grass 1.35 , Impen%ious Area 0.52 Subtotal: 2.10 AREA TA3 Till-forest 0.00 Till-grass 0.20 Impervious Area 0.36 Subtotal: 0.56 Tributarv Area Totals Till-forest 1.03 Till-grass 2.99 j Impervious Area 1.10 ', FRONT (Frontage) Area (ac) I! Till-forest 0.0 ' Till-orass 0.20 Impervious Area 0.90 ', Total: 1.10 ONSITE (Phase I+II) Area (ac) Till-forest 0.0 Till-grass 12.05 Impervious Area 18.05 , Total: 3010 � DEVELOPED CONDITIONS Total area= 36.32 ac (Complete Summary of Areas) Ground Cover Area (ac) Till-forest 0.23 Till-grass 14.49 Iinpeivious �1rea 21.60 See the KCRTS calculations in the Appendix for tl�e detail I ;ii��, �,��i��_, i I ��. I`I '' �°1 ' ' DEVELOPED TIMESERIES Flow Frequency Analysis Time Series File:dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 6.54 6 2/09/O1 2:00 13 .29 1 100.00 0.990 5.28 8 1/OS/02 16:00 8.22 2 25.00 0.960 7.87 3 2/27/03 7:00 7.87 3 10.00 0.900 5.65 7 8/26/04 2:00 6.94 4 5 .00 0. 800 6.82 5 10/28/04 16:00 6.82 5 3 .00 0.667 6.94 4 1/18/06 16:00 6.54 6 2 .00 0.500 8.22 2 10/26/06 0:00 5 .65 7 1.30 0.231 13.29 1 1/09/08 6:00 5.28 8 1.10 0.091 Computed Peaks 11.60 50 .00 0.980 ! ,�� I'��i�,�� I ��. I�� i,., .� ��r� ,,� � � �, DETENTION ROUTING CALCULATIONS The City of Renton requires the Conservation Flow Control standard for Division III that requires the proposed pond outfall to match or not exceed the 2-year and 10-year predeveloped release rates. The pond is also required not to exceed frequency and duration for '/z the 2-year up to the 50-year stornl e�ents. Usin�the appropriate release rates the developed timeseries «-as modeled in a pond that closely approximates the existing pond as constructed for Division I and II. The existing pond modeled in KCRTS was modeled based on as-built information collected about the pond. This included actual orifice and outfall elevations along with the measured volumes for live and dead storage. The actual live storage volume provided in the pond is 408,298 cubic feet and the dead storage volume is 119,590 cubic feet. The tabulation for the asbuilt volume available in the pond is included in the appendix of this report. The followinQ calculations confirm that the pond, as constructed and without modifications, is adequate to maintain release rate, frequency-duration and«-ater quality with the proposed Division III impro�-ements. I ,ir•c�� i , l il 'I' ' � , I Actual As-constructed pond l�Iodel The existing pond was modeled from actual, measured dimensions. This included the actual elevations of the Live/Dead interface, the ele�ation of the orifice, the riser top and the volume available�vithin the pond itself. This information was used to produce the following pond parameters for modeling: Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 2 .00 H:1V Pond Bottom Length: 234.00 ft Pond Bottom Width: 100.00 ft Pond Bottom Area: 23400. sq. ft* Top Area at 1 ft. FB: 43122 . sq. ft 0 .990 acres Effective Storage Depth: 11.80 ft* Stage 0 Elevation: 364 .90 ft* Storage Volume: 377895 . cu. ft 8 .675 ac-ft Riser Head: 11.15 ft* Riser Diameter: 24.00 inches ; Number of orifices : 2 '� Full Head Pipe Orifice # Height Diameter Discharge Diameter ' (ft) (in) (CFS) (in) 1 0.00 3.06 0.849 2 8.46* 6.00 1.601 8. 0 Top Notch Weir: None Cutflow Rating Curve: None The developed timeseries (Dev.ts fl previously described was combined«�ith the pond detailed above to determine the resulting pond outfall timeseries (rdout.ts�. This timeseries«as compared against the predeveloped timeseries to check for both release rate and frequeney-duration to check the ponds compliance� ��ith the � KCS�VD��f ?005 perfoi7nance standard. ; , i . 11nir�;l f + �, �'�I I': ' ,, ' Pond Outfall Timeseries, release rate Check Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 2.39 2 2/09/O1 20:00 8. 03 11.58 1 100.00 0. 990 0.614 7 12/29/O1 10:00 2.39 10.99 2 25.00 0.960 1.80 4 3/06/03 22:00 1.97* 9.91 3 10.00 0.900V � 0.546 8 8/26/04 7:00 1. 80 9.55 4 5.00 0.800 0 .679 6 1/05/05 17:00 1.44 8.95 5 3 .00 0.667 II 1.44 5 1/18/06 23:00 0.679** 7.12 6 2.00 0.500� i 1.97 3 11/24/06 8:00 0.614 5.84 7 1.30 0.231 I 8 .03 1 1/09/08 10:00 0.546 4.60 8 1.10 0.091 Computed Peaks 6.15 11.47 50.00 0.980 �i, * release rate at or below Predeveloped release rate� ** release rate at or below 1/Z the Predeveloped rate� I �� I!• i� i I I'' !',� � � Comparing Prede�°eloped��ith Pond Outfall, Frequencv and Duration Check Duration Comparisor_ A�aylsis Base File: preaev.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- ' Cutoff Base New gChange Probability Base New �Char_ge 0.684 I 0.68E-02 0.60E-02 -12.4 � 0.68E-C2 0.684 0.673 -1.7 V � 0.739 I 0.59E-02 0.29E-02 -51.2 � 0.59E-02 0.739 0.687 -7.0 0.793 � 0.52E-02 0.24E-02 -53.9 � 0.52E-02 0.793 0.701 -11.6 0.847 I 0.47E-02 0.22E-02 -53.1 I 0.47E-02 0.847 0.710 -16.1 0.901 I 0.42E-02 0.20E-02 -52.5 I 0.42E-02 0.901 0.720 -20.1 0.955 � 0.37E-02 O.1BE-02 -51.1 ! 0.37E-02 0.955 0.726 -24.0 1.01 I 0.31E-02 0.16E-02 -49.2 I 0.31E-02 1.01 0.733 -27.4 1.C6 � 0.28E-02 0.16E-02 -41.4 I 0.28E-02 1.06 0.742 -30.3 1.12 I 0.25E-02 0.16E-02 -36.2 ' 0.25E-02 1.12 0.776 -30.6 1.17 I 0.20E-02 0.15E-02 -22.8 � 0.20E-02 1.17 0.891 -24.0 1.23 � 0.17E-02 0.15E-02 -10.5 � 0.17E-02 1.23 0.979 -20.2 1.28 � 0.15E-02 0.15E-02 0.0 '� 0.15E-02 1.28 1.28 0.0 1.33 � 0.14E-02 0.15E-02 7.2 � 0.14E-02 1.33 1.37 2.9 1.39 � 0.12E-02 0.13E-02 12 .3 I 0.12E-02 1.39 1.45 4.1 1.44 I 0.11E-02 0.12E-02 5.8 I 0.11E-02 1.44 1.49 3.1 1.50 � 0.98E-03 0.11E-02 11.7 � 0.98E-03 1.�0 1.58 5.7 1.55 I 0.86E-03 0.99E-03 15.1 i 0.86E-03 1.55 1.64 5.7 1.61 � 0.77E-03 0.91E-03 19.1 � 0.77E-03 1.61 1.70 5.7 � 1.66 � 0.68E-03 0.83E-03 21.4 I 0.68E-03 1.66 1.74 4.9 'I 1.71 � 0.62E-03 0.73E-03 18.4 I 0.62E-03 1.71 1.78 3.6 1.77 I 0.55E-03 0.62E-03 11.8 I 0.5�E-03 1.77 1.79 1.0 I, 1.82 I 0.49E-03 0.47E-03 -3.3 I. 0.49E-03 1.82 1.81 -0.6 ' 1.88 � 0.41E-03 0.42E-03 4.0 ; 0.41E-03 1.88 1.90 1.3 '� 1.93 � 0.31E-03 0.34E-03 10.5 0.31E-03 1.93 1.97 1.9 ', 1.99 � 0.28E-03 0.28E-03 0.0 j 0.28E-03 1.99 1.99 0.3 , 2.04 I 0.21E-03 0.24E-03 15.4 I 0.21E-03 2.04 2.11 3.6 I 2.09 I 0.16E-03 0.23E-03 40.0 ! 0.16E-03 2.09 2.21 5.7 , 2.15 I 0.98E-04 0.20E-03 100.0 ; 0.98E-04 2.15 2.31 7.6 ' 2.20 I 0.98E-04 0.18E-03 83.3 � 0.98E-04 2.20 2.31 4.9 � 2.26 � 0.82E-04 0.13E-03 60.0 � 0.82E-04 2.26 2.33 3.2 �, 2.31 I 0.658-04 0.98E-04 50.0 � 0.65E-04 2.31 2.36 2.1 I 2 .36 � 0.16E-0? 0.495-04 200.0 I C.16E-04 2.36 2.39 1.1 � Maximum positive excursion = 0 . 173 cfs ( 8 .2%) � < 10% ', occurring at 2.12 cfs en the Base Data:prede„�.�sf and at 2.29 cfs on the New Da�a:rdout.ts' ' �?aximum negative excursion = 0.340 cfs (-=� . -�, occurring at 1.11 c�s on the B�se Da_a:�rede-: ._�r �-d �r �.�5^ �f� �� tne I•:�.. ��t�.rc��=. _. � T1lerefore, the p�nd as modeled is adequate. The volume �unnnary is: Live Stora�e: 377,89� cf required 408,298 cf provided (as constl•ucted) I , i�r�.�l�•��i��, � i��,. lil ;� _ � , , � IV. WATER QUALITY VOLUME The water quality volume (dead storage) «-as deternlined using the procedure � outlined in the King County Surface Water Design Nlanual Page 6-68. In this ! procedure a volume is determined using the areas of Impervious, Forest and Grass land-covers in the developed basin. The volume (Vr) is then multiplied by a factor (3 in this case) to determine the total minimum volume required. The land-covers, ' as determined in the pond sizing calculations, are repeated in the following table: DEVELOPED CONDITIONS Total area= 36.32 ac Com lete Summary of Areas) Ground Cover Area (ac) Till-forest 0.23 Till-grass 14.49 Impervious Area 21.60 ' The calculation for minimum required dead storage volume is: The basic water quality menu(KCSWDM—both 1998 and 2005): Vr= 0.90�`Ai + 0.25*Ag + O.lOAtf X R/12 Vr= [0.90*(21.60*43560) +0.25*(14.49*43560) + 0.10(0.23*43560)] x R/12 Vr= (846,806 + 159,974 � 1002) x 0.47/ 12 Vr= 39,471 Vb = 3 x Vr Vb = 3 * 39,471 I Vb = 118,415cf ' Dead Storage: ! 118,415 cf required ' 119,�90 cf provided (as constructed) ' f �� II �i��. I �i I I! I' i �, � � ' � V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN The storm drainage conveyance «-ill be sized at final design. � �� u�e ll��ii��,l f)i�� I II I',i�:��' '� r, ,,i�_' ' VI. SPECIAL REPORTS AND STUDIES Technical Infornlation Report for Laurelhurst—Di�,�ision I ,Core Design Inc., Se�pt. 2004 Tecl-uiical Information Report for Laurelhurst —Division II ,Core Desi�n Inc, I�larch ?005 I ;��i��:�-!,i��, � I ,;, I ' I', , . I �� ,�� ' ' VII. OTHER PERMITS No special permits anticipated at this time. I ��ii��_�II�� .� I ?��, III l'��. I `� ,�,I ` ' VIII. ESC ANALYSIS AND DESIGN ' Total area= 2.46 Ac Therefore a sediment trap will be used ! i The King County E.S.C. manual page D-45: SA =2 x Q2 / 0.00096 Q2 = 0.5 cfs ** SA = 2(0.5)10.00096 SA= 1,050 SF of Sediment Trap ** **Actual final dimension to be determined at final plan submittal, these numbers are an estimate I ,�i,i�:_�,,i i � , i� I �, i , � „ � � , IX. OPERATIONS AND MAINTENANCE MANUAL The detention i water quality pond, along with all the conveyance pipe and structures are all public so the Operations and Maintenance Manuals are not required. ' I I ' I � � ;IUI'c'��IIII'`�) � )i'� �� ';1�<'c 'll ��I ' ' �'C � A z w a a � � ns<'��Nti'nzu��i�i�i� '�� LIVL/llliAll VOLUME CnL('ULA'I�IONS 02052 LAUIt�;LHUitS'I' _--- --- --_---- -- - GLEVATIO INCRI?MIiN'I'AL I:I.�VATIO INCKI?ML^;N'1'A 1U7AL LN� VOLUME VOLUMf; VOLUMF, VOLUM� sr ci cr cr �r cr 35G.0 28 � 1,259 357.5 1,768 357.4 1,770 1,25'I U 1,952 1,I 3 I 35R.0 (,,0411 35H.0 2.000 4,342 0 17,3 I 5 5,I S4 360.0 11,275 36O.O 3,154 � ?G,811 0 24,5G4 7,G75 3G2.00 13,289 3(>2.00 4,521 59.050 0 21,525 9.265 363.8 15,072 3G3.h 5,773 <)3,K39 0 0 31i3.S 21,252 93,�3�> I) 4,329 3G4.0 ?2,0�10 9R,I(iR 0 364.90 47,604 119,590 Dead Storage 3G6.0 25,564 145,772 2G,182 5�1,712 3G5.0 29,14H 2O0,484 8Q894 G2,OSK 370-0 32,910 2G2,542 142,952 (i�),71)�l 372.0 3G,799 332,251 212,GG1 77,571 374.0 40,772 409,822 ?90,232 85,54G 37(�.0 44,774 495,3Gti 375,77H 376.70 7K,`)77 527,888 408,298 Live Storagc 377.7 4h,140 � � �bNb �(b�uwl� � G5 CriylS�l�� . s Retention/Detention Facility * = values measured from constructed pond and control structure Type of Facility: Detention Pond Side Slope: 2 .00 H:1V Pond Bottom Length: 234.00 ft Pond Bottom Width: 100 .00 ft Pond Bottom Area: 23400. sq. ft* Top Area at 1 ft. FB: 43122 . sq. ft 0 .990 acres Effective Storage Depth: 11.80 ft* Stage 0 Elevation: 364.90 ft* Storage Volume: 377895. cu. ft 8.675 ac-ft Riser Head: 11.15 ft* Riser Diameter: 24 .00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) {in) (CFS) (in) 1 0.00 3.06 0.849 2 8.46* 6.00 1.601 8 . 0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 364.90 15494. 0 .356 0 .000 0.00 24275. 0.03 364.93 16223 . 0 .372 0.045 0.00 24316. 0.06 364.96 16953 . 0 .389 0.064 0.00 24357. 0. 10 365.00 17928 . 0.412 0.079 0.00 24411. 0. 13 365.03 18661. 0.428 0.091 0.00 24452 . 0 .16 365.06 19395. 0.445 0.102 0.00 24493 . 0.19 365.09 20131. 0.462 0.111 0.00 24534 . 0.22 365.12 20867. 0 .479 0 .120 0.00 24574 . 0.26 365.16 21851. 0 .502 0. 129 0 .00 24629. 0.44 365.34 26307 . 0.604 0.170 0.00 24875 . 0.63 365.53 31058 . 0.713 0.202 0.00 25136 . 0. 82 365.72 35858. 0.823 0 .231 0.00 25398 . 1.01 365.91 40709. 0 .935 0 .256 0 .00 25662 . 1.20 366.10 45610. 1.047 0.279 0.00 25926 . 1.39 366.29 50561. 1.161 0.300 0. 00 26192 . 1.58 366.48 55563 . 1.276 0 .320 0.00 26459. 1.77 366.67 60616 . 1.392 0 .338 0.00 26727 . 1. 96 366.86 65719. 1 .509 0 .356 0.00 26996. 2 . 15 367. 05 70874 . 1 .627 0 .373 0.00 27266 . 2 . 33 367.23 75805. 1.740 0.389 0.00 27523 . 2 .52 367.42 81061. 1. 861 0.404 0.00 27796 . 2 . 71 367.61 86368 . 1 . 983 0 .419 0. 00 28070 . 2 . 90 367. 80 91727. 2 .106 0 .433 0. 00 28344 . 3 . 09 367. 99 97139. 2 .230 0 .447 0.00 28620 . 3 .28 368. 18 102603 . 2 .355 0 .461 0.00 28898 . 3 .47 368.37 108120. 2 .482 0.474 0.00 29176 . �v� �� , 3 . 66 368.56 i13690. 2 .610 0.486 0. 00 29455 . 3 .85 368.75 119313. 2 .739 0.499 0. 00 29736. 4.03 368.93 124690. 2 .662 0.511 0. 00 30003 . 4 .22 369.12 130417. 2 .994 0.523 0.00 30286. 4 .41 369.31 136198. 3 .127 0.534 0.00 30570 . I 4 .60 369.50 142034. 3 .261 0.546 0.00 30855. ', 4 .79 369.69 147923. 3 .396 0.557 0.00 31141. ' 4 .98 369.88 153867. 3 .532 0.568 0 .00 31429. 5. 17 370.07 159866. 3 .670 0.578 0 .00 31717 . 5.36 370 .26 165920. 3 .809 0.589 0 .00 32007 . 5_55 370.45 172a29. 3 .949 0.599 0.00 32298. 5.74 370 .64 178193. 4 .091 0.609 0.00 32590. 5.92 370 .82 184085. 4 .226 0.619 0.00 32868. 6.11 371.01 190358. 4 .370 0.629 0.00 33163 . ', 6.30 371.20 196687. 4 .515 0.639 0.00 33458. i 6.49 371.39 203072. 4 .662 0.648 0.00 33755 . � 6.68 371.58 2�9513. 4.810 0.658 0.00 34053 . 6.87 371.77 216012. 4.959 0.667 0.00 34352 . 7.06 371.96 222567. 5.109 0.676 0.00 34652 . 7 .25 372 .15 229179. 5.261 0.685 0 .00 34953 . 7.44 372 .34 235849. 5.414 0.694 0.00 35255 . 7.63 372 .53 242577. 5.569 0.703 0 .00 35559. 7.81 372 .71 249003. 5.716 0 .711 0 .00 35848. 8.00 372 .90 255843. 5.873 0 .720 0.00 36154 . 8.19 373 .09 262742. 6.032 0.728 0.00 36461. 8 .38 373 .28 269698. 6.191 0.736 0.00 36769. 8 .46 373 .36 272645. 6.259 0.740 0. 00 36899. 8 .52 373 .42 274862 . 6.310 0.753 0. 00 36997. 8 .59 373 .49 277456. 6.370 0.788 0.00 37111. 8.65 373 .55 279685 . 6.421 0. 841 0.00 37209. 8.71 373 .61 281921. 6.472 0. 913 0.00 37307 . 8.77 373 .67 284162 . 6.523 1. 000 0.00 37405 . 8. 84 373 .74 286784. 6.584 1.350 0.00 37520 . 8.90 373 .80 289039. 6.635 1.400 0.00 37618 . 8.96 373 .86 291299. 6.687 1.450 0.00 37717. 9.15 374 .05 298494. 6.852 1.580 0.00 38029. 9.34 374.24 305750. 7.019 1.690 0 .00 38343 . 9.53 374.43 313065. 7. 187 1.790 0.00 38659. 9.72 374 .62 320440. 7.356 1.890 0.00 38975. 9. 90 374 .80 327483. 7.518 1.970 0.00 39276. 10.09 374 .99 334975. 7.690 2 .060 0.00 39594 . 10.28 375.18 342529. 7.863 2 .130 0.00 39914. 10.47 375.37 350143 . 8.038 2 .210 0.00 40235. 10.66 375.56 357816. 8.214 2 .280 0.00 40557. 10. 85 375.75 365554. 8.392 2 .350 0.00 40880. 11.04 375.94 373352 . 8 .571 2 .410 0.00 41204 . 11. 15 376.05 377895. 8.675 2 .450 0.00 41393 . 11.25 376.15 382043 . 8.771 3 .100 0. 00 41564 . 11.35 376.25 386208. 8. 866 4 .260 0 .00 41736 . 11.45 376.35 390390. 8. 962 5. 750 0.00 41908 . 11.55 376.45 394590. 9. 059 7.510 0.00 42081. , 11.65 376.55 398806. 9. 155 9.500 0.00 42253 . ' 11.75 376.65 403040. 9.253 11.700 0.00 42427 . ' 11.85 376.75 407292 . 9.350 14 .080 0. 00 42600. 11.95 376.85 411560. 9.448 16.230 0 .00 42774 . 12 . 05 376.95 415845. 9. 547 �7 . 080 0 . 00 42948 . 12 . 15 377. 0� ��0150 . ; . �4� =� . 8?�� 0 . ,�", 4312� . ��, �l� c . 12 . 25 377 . 15 �2441_. 9. 7=5 18 .60'0 0 . 00 43297 . 12 .35 377.25 428809. 9.844 19.390 0.00 43472 . 12.45 377.35 433165. 9.944 20 .100 0.00 43647 . 12 .55 377.45 437539. 10.045 20 .780 0.00 43823 . 12 . 65 377.55 441930. 10.145 21.430 0. 00 43999. 12 .75 377.65 446339. 10.247 22 . 070 0. 00 44175 . 12 .85 377.75 450765. 10.348 22 .680 0.00 44352 . 12 .95 377.85 455209. 10.450 23 .280 0.00 44529. 13 .05 377 .95 459671. 10.553 23 . 860 0 . 00 44705. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 13 .29 ******* 8.03 11.58 376.48 395686. 9.084 2 6.54 ******* 2.39 10.99 375.89 371310. 8.524 3 6.57 2.32 1.97 9.91 374.81 327798. 7.525 4 7.87 ******* 1.80 9.55 374.45 313762. 7.203 5 6.94 ******* 1.44 8.95 373.85 290989. 6.680 6 4 .10 0.69 0.68 7.12 372 .02 224771. 5.160 7 5.28 ******* 0.61 5.83 370.73 180993 . 4 .155 8 5.65 ******* 0.53 4.39 369.29 135561. 3 . 112 ---------------------------------- P,oute Time Series through Facility Inflow Time Series File:dev.�sf Outflow Time Series File:rdou� Ir_flow/Outflow Analysis Peak Inflow Discharge: "�3 .29 �FS a� 6 : 00 on �ar_ 9 in Year 8 Peak Outflow Discharge: 8 .03 CFS a� 10 : �0 on Jan 9 in �ear 8 Peak Reservoir Stage: 11.58 Ft Peak Reservoir Elev: 376.48 Ft Peak Reservoir Storage: 395686. Cu-=� . 9.084 Ac-Ft Flow Freq�ency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates-- ----F1ow Fre�uer_ci✓ Analysis------- ,low Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 2 .39 2 2/09/O1 20:00 8.03 11.58 1 100.00 0.9°0 0.614 7 12/29/O1 10:00 2 .39 10. 99 2 25. 00 0. 96� 1.80 4 3/06/03 22 :00 1.97 9. 91 3 10.00 0. 900 0.546 8 8/26/04 7:00 1.80 9.55 4 5.00 0.800 0. 679 6 1/05/05 17 :00 1.44 8.95 5 3 .00 0. 667 1.44 5 1/18/06 23 :00 0 .679 7. 12 6 2 .00 0.500 1 . 97 3 11/24/06 8:00 0 .614 5. 84 7 1.30 0.231 B. 03 1 1/09/08 10: 00 0 .546 4 .60 8 1. 10 0. 091 Ccmputed Peaks 6 . 15 11 ._? 50 . 0� 0. 980 3�� . Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS °s $ � 0.034 36948 60.254 60.254 39.746 0 .397E+00 0.101 4381 7.144 67.399 32 .601 0 .326E+00 0.168 4528 7 .384 74.783 25.217 0.252E+00 0.235 4018 6.553 81.336 18.664 0.187E+00 0.303 3450 5 .626 86.962 13 . 038 0.130E+00 0.370 2709 4.418 91.380 8.620 0 .862E-01 0.437 1837 2 .996 94.375 5.625 0 .562E-01 0.504 1231 2 .008 96.383 3 .617 0 .362E-01 0.571 767 1.251 97.634 2 .366 0 .237E-01 0.638 634 1.034 98.668 1.332 0.133E-01 0.705 504 0.822 99.490 0.510 0.510E-02 0.772 161 0.263 99.752 0.248 0.248E-02 0.840 16 0.026 99.778 0.222 0 .222E-02 0.907 17 0.028 99.806 0.194 0 .194E-02 0.974 14 0 .023 99.829 0.171 0 .171E-02 1.04 5 0 .006 99.837 0.163 0.163E-02 1.11 3 0.005 99.842 0. 158 0.158E-02 1.18 2 0.003 99.845 0. 155 0 .155E-02 1.24 1 0.002 99.847 0.153 0 .153E-02 1.31 5 0.008 99.855 0. 145 0 .145E-02 1.38 7 0 .011 99.866 0.134 0 .134E-02 1.44 9 0.015 99.881 0. 119 0.119E-02 1.51 8 0.013 99.894 0. 106 0.106E-02 1.58 S 0.008 99.902 0.098 0 .978E-03 1.65 8 0.013 99.915 0 .085 0 .848E-03 1.71 7 0.011 99.927 0.073 0 .734E-03 1.78 9 0.015 99.941 0. 059 0.587E-03 1. 85 9 0.015 99.956 0. 044 0.440E-03 1.91 3 0. 005 99.961 0 .039 0 .391E-03 � 1.98 7 0.011 99.972 0.028 0.277E-03 2.05 2 0.003 99.976 0.024 0 .245E-03 2.12 2 0.003 99.979 0.021 0.212E-03 2 .18 2 0. 003 99.982 0.018 0.179E-03 2 .25 2 0.003 99.985 0.015 0.147E-03 2 .32 4 0.007 99.992 0.008 0.815E-04 ' 2.38 4 0.007 99.998 0 .002 0.163E-04 Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) ' 1 13 .29 ******* 8. 03 11.58 376.48 395686. 9. 084 ', 2 6. 54 ******* 2 .39 10.99 375.89 371310. 8 .52� ' 3 6.57 2 .32 1.97 9.91 374 .81 327798. 7.525 4 7. 87 ******* 1.80 9.55 374.45 313762 . 7.203 5 6. 94 ******* '_.44 8.95 373 .85 290989. 6.680 6 4 . 10 0 .69 0.68 7 .i2 372 .02 224771. 5.160 7 5 .26 ******* 0 .61 5.83 370 .73 180993 . 4.1�5 8 5 . 55 ******* 0 .5? 4 .39 359.29 135�51 . 3 . 11= ��1