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HomeMy WebLinkAboutSWP272332(1) STORM DRAINAGE REPORT FOR CURTIS H, LLC LOT 1 OF WASHINGTON TECHNICAL CENTER LOCATED AT SOUTHWEST 7TH STREET NEAR POWELL AVENUE RENTON,WASHINGTON FOR SGA CORPORATION BY JOHN E. ANDERSON, P.E. BUSH, ROED & KITCHINGS, INC. 2009 MINOR AVENUE EAST SEATTLE, WA 98102 (206) 323-4144 BRH JOB NO. 97102.00 � xZ DATE 268 � July 15, 1997 �.c► �`'�tsT 7878 EXPIRES 12111 Lol, 4 59' R—Mg 14* ------ - L-f28*;7' 3 LOT A-lfr 29' 5f -p L-115. ASEMEN7 .tiff it ,2W RAKROAD EASEMENT 20'RMAW PER RFC. NO. 7907399548 EAW"T PER REC. NQ Le =====)I rc =T-M!ll'-!ll SO 'UTILITY&SIDEWALK ENT LCORD', lf�1501(RVCORD) 12' W S.W. 7th ST. Wv 12" W Fli 14 J d" J - y'i `�Z r / / ro 9 CT� W N H 0 M E ' '� �-�� I • I- �' , �� r .r 70 60 UNITS $ / � ?Q ?S y�C/% 4 $ a 1/ e Cy/C C tie .K -� , `10IbHAs i 11 nasls tts, , a , '' O 4 lQ E 1I A O '/3; t �Av� s SA lC/�iC Q 3 b 1 B �`y A I �6 uNl S � `Y f414"go wo 5 Ac. +ems A CO/y0 rc.86 1 776.?S writ irr _ E�SIwK.vr � I 13 /210 q L03Ac•C . ,ov t to30-1 �- C A L I F ;C E E 3 R 6E0. A/ HORMEL 8 0. P A R K 1 6 CENTRAL a PUGET INC. SGA SITE E .1 2.113A� E/ Q a � n.t70 _ __f 457_fps n / r 37-77 5DIA6. '%� " A�% `l 7 TA..254 4 i — . " ' $ .o AS OF TTLE TLAS OF SEATTLE RIGHTED & PUBLISHED BY r 336W ntent COPYRIGHTED 8 PUBLISHED BY lipital KROLL MA OMPANY, INC., SEATT KROLL MAP COMPANY, INC., SEATTLE SCALE: ET SCALE t INCH 200 FEET 't,-Z00 d TABLE OF CONTENTS I. Project Overview H. Preliminary Conditions Summary III. Core and Special Requirements IV. Detention Analysis V. Water Quality Design VI. Level I Analysis VII. Pipe Sizing Calculations VIII. Erosion Control I. PROJECT OVERVIEW SGA is proposing to build a 34,585 square foot office/warehouse building on Parcel A of Washington Technical Center. The total site is 2.88 acres in size. Rail road track are located on the northern and eastern boundaries. The tracks are located within easements recorded with the plat. Southwest 7th Street is the southern boundary of the site. Grades on the site vary from elevation 20 in the northeastern corner to elevation 16 in the southwestern corner. The ground slopes within the property are between 1 and 2 percent. Ground cover consists of blackberry bushes and grasses. The proposed building would be dock high. Truck loading docks would be located on the north side of the building. The building finish floor elevation would be approximately 2.5 feet above the existing ground elevation. There will be approximately 1.3 acres of asphalt paving around the building for vehicle parking lot and truck maneuvering areas. Storm water runoff from the asphalt pavement will be conveyed to a combine wetpond/detention pond located at the southwest corner of the site. The wetpond is oversize so biofiltration swales are not required. Filter strips will be used for water quality improvements for the parking area along Southwest 7th Street. This area will have the most vehicle traffic and the filter strips will provide additional water treatment. Construction of an office/warehouse building on this site is consistent with surrounding developments. Utilities within Southwest 7th Street have been sized for this type of development. There is adequate depth for gravity storm water and sanitary sewer connections. According to City records, a 10-inch water main is stubbed to the southeast corner and a 12-inch water main is located within Southwest 7th Street. Therefore, the development of this property does not present any significant design problems. H. PRELIMINARY CONDITIONS SUMMARY The 2.88 acre site is covered with blackberry bushes and grasses. Existing ground slopes from west to east at slopes between 1 and 2 percent. A 60-inch storm drainage pipe is located in Southwest 7th Street. According to the City, storm water runoff from the developed site can be discharge to the 60-inch pipe. Storm water detention is required prior to discharge from the site. The detention pond will be sized using the King County Design Manual Method as adopted by city of Renton. No offsite areas contribute to the storm water flows. An existing CN value of 82 will be used to calculate the pre-developed storm water peak flows. III. CORE AND SPECIAL REQUIREMENTS CORE REQUIREMENT#1: Storm water will be discharged to the existing 60-inch storm drainage pipe located in Southwest 7th Street. The pipe design included this property in the tributary area. This is the City's recommended storm drainage connection. Therefore Core Requirement #1 is met. CORE REQUIREMENT#2 The railroad tracks and Southwest 7th Street grades prevent offsite storm water from entering the site. Therefore, no upstream basin analysis is required for this property. Storm water discharged from the site will be conveyed by 60-inch.storm pipes in Southwest 7th Street. The 60-inch pipe flows west to Naches Avenue. The storm water then flows north in Naches where it is discharged into a regional storm water mitigation area. The existing conveyance system was design to convey storm water discharged from the site. Original sizing for the pipe used the Rational Method of analysis. Current design standards use the hydrograph method that lowers peak rate discharge from that calculated by the Rational Method. Therefore, the downstream system has adequate capacity for the proposed development. CORE REQUIREMENT#3 Peak rate control will be provided for the storm water runoff. A storm water detention system will be located in the southwest corner of the site. Developed storm water peak rate discharges from the site will be limited to the 2 year, 10 year and 100 year pre-developed values. Storm water detention facility calculations are included in the report. The City allows over-sizing the wetpond for mitigation of the biofiltration swale requirements. The required wetpond volume is 3,955 cubic feet. The volume provided is 11,742 cubic feet. The proposed wetpond also provides nearly 3 times the required surface area. Therefore, biofiltration swales are not required. Wetpond sizing calculations are included in the report. CORE REQUIREMENT#4 Detailed pipe sizing calculations are provided. The calculations show there is more than adequate conveyance capacity for the 100 year storm water peak flows. CORE REQUIREMENT#5 A detailed erosion/sedimentation control plan has been prepared for the site grading. The storm water detention pond will be used for a settling basin during construction. According to the design standards, a sediment trap would meet the requirements for this site. Using the detention pond provides significantly more sediment volume and surface area than required. Since the pond is oversized for the developed conditions, it will more than adequate for controlling run off during the site grading phase. Interceptor swales and filter fabric fence will be installed at the limits of clearing. Rock check dams will be installed in the interceptor ditches. Rock construction entrances will be installed at the proposed driveway locations. SPECIAL REQUIREMENTS SECTION 1.3 The only Special Requirement that applies to this project is 1.3.5. A wetpond is required because the development will have 1.3 acres of imperious surface area subject to vehicular use. A wetpond will be constructed in the storm water detention pond area. According to the manual,the wetpond must provide the PT-WQ Storm volume and have a surface area equal to 1% of the impervious surface area. The proposed detention/wetpond design exceeds both of these conditions. IV. DETENTION ANALYSIS a BUSH, ROED&HITCHINGS, INC. ,JOB S(::�,�" CIVIL ENGINEERS& LAND SURVEYORS SHEET NO. OF 2009 Minor Avenue East Seattle,WA 98102 CALCULATED BY DATE —7/ t Z 9 / (206)323-4144 FAX(206)323-7135 BRH 1-800-935-0508 CHECKED BY DATE SCALE STOR rv� W RT`� ETk�T 0,,! / \,Aj ETPo,�-J_C) E nl LE S t"rt r'C,W tit_ P�PPRovatu __ L� ELEw►4zt��.f._. ..O.F ;`�-EC- :.."QETENT�orJ.__ FO►` 1> (JNS. M0VEX-) _hP 2 F't`ET. Ti-t�5 \Af I45 Po .IE __ Tb_ FI�DVCrE Tk- S ........ NGE OF s-r�Rw-\ \,v A-rEIZ Bac K I►•.� (o _ 11,4 TO- .T+m . DZTc- .7 o.N C't i NJ .. S W $4 .STD Te TiEo-�t orb DE E Tl.0�J_ �'S fJ'(�W .. 5 ? .....p.T P�PPf20`K t van A. L:�( "r --E T "rbP'.. . ar_ "r;- _.:._ ''_..P.�.......... e.► I .FLo�u_ v�.1 l -l- .. ALSO ... ..........--o. ............. "r............. Pav o . -F ...................... _ c. .. C rev R- M .. 1. .....0 ...�? ... ...-rc _., .. l,to ... .. T. __ kl►4t�. ......Pt\ .O_tJC�. 'C €,_..... JE.. T 1 e b Ca E... . t.Ao Tc� . ._ .�-�. _► Tc�,... 5 Peso .._�. .� ss - '►-�� TPoN a .. va . w► Rcv�� rROI _fo,z c -ro __..l l } _4� .G . Tl-� . u1 NT _Qv p.t. Y . U�LS.�Yv�E REQ l 2. C>:........._ FotLT -� �'t'E ...................t .. . 3 . 95 ............. 9"7... Tt 5.;. _ Pt'C'2 .Vol u m t 4-t'� T1t�►`1 ..M► Oc�E 1�0'C �EQv_t2D.• PNOOMT 204-1(U*,We6)205 I(Padded)®®Im Grobn,Man.01471.To Order PHONE TOLL FREE 1-800-225 @80 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL 1 FIGURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN KING COUNTY: HYDROLOGIC HYDROLOGIC SOIL GROUP GROUP' SOIL GROUP GROUP* Alderwood C Orcas Peat D Arents,Akierwood Material C Oridia D Arents..Everett Material B Ovall C Beausite C Pichuck C Bellingham D Puget D Briscot D Puyallup B Buckley D Ragnar B Coastal Beaches Variable Renton D Earlmont Sit Loam D Riverwash Variable Edgewick C SaW C Everett A Sammamish D Indianola A Seattle D K/tsap C Shacar D Klaus C Si Sit C Mixed Alluvial Land Variable _ Snohomish D Newton A Sultan C Newberg B Tukwila D Nooksack C Urban Variabl Normal Sandy Loam D Woodinville D HYDROLOGIC SOIL GROUP CLASSIFICATIONS A (Low runoff potentI4. Soils having high Infitration rates, even when thoroughly wetted,and consisting chiefly-of deep,well-to-excessively drained sands or gravels. These sods have a high rate of water transmission. B. (Moderately low runoff potential). Sons having moderate infiltration rates when thoroughly wetted,and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C. (Moderately high runoff potential). Sods having slow Infiltration rates when thoroughly wetted,and consisting chiefly of soils with a layer that Impedes downward movement of water, or soils with moderately fine to fine textures. These sods have a slow rate of water transmission. D. (High runoff potential). Sods having very slow infiltration rates when thoroughly wetted and consisting chiefly of clay sods with a high swelling potential, soils with a permanent high water table, sods with a hardpan or day layer at or near the surface, and shallow soils over nearly impervious material. These sods have a very slow rate of water transmission. • From SCS,TR-55, Second Editkx-,June 1986. Exhibit A-1. Revisions made from SCS, Sol Interpretation Record, Form #5,September 1988. 3.5.2-2 I/90 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.52E SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS In 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated land(1): winter condition 86; 91 964 95 Mountain open areas: low growing brush and grasslands 74 V 89 92 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed 42 64 76 81 Wood or forest land: young second growth or brush 55 72 81 86 Orchard: with cover crop 81 88 92 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 80 86 90 fair condition: grass cover on 50% to 75% of the area 77 85 90 92 Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89 Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 100 100 Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shag be selected 2.0 DU/GA 25 for pervious and 2.5 DU/GA 30 Impervious portion 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 . 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 Planned unit developments, % Impervious condominiums, apartments, must be computed commercial business and Industrial areas. (1) For a more detailed description of agricultural land use curve numbers refer to National Engineering Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff )s directed Into street/stoma system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. 1 i 3.5.2-3 I/90 • • • wow- moo ILI FIRM! i . �il w . gets 4A Ill Wig wrist, w► • � . •ems e� ��.. r::i* !, � r WAR 7/15/97 11 :38 :9 pm Bush, Roed & Hitchings, Inc page 1 SGA SITE AT WASHINGTON TECH CENTER JOHN E . ANDERSON, P.E. PROJECT NO. 97102 BASIN SUMMARY BASIN ID: B1 NAME: 2 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 2 . 88 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 82 . 00 0 .00 TC. . . . . 18 . 00 min 0 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 .29 cfs VOL: 0 . 16 Ac-ft TIME : 480 min BASIN ID: B2 NAME : 10 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 90 inches AREA. . : 2 . 88 Acres 0 .00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 82 . 00 0 . 00 TC. . . . . 18 . 00 min 0 .00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 0 .72 cfs VOL: 0 .31 Ac-ft TIME: 480 min BASIN ID: B3 NAME: 100 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 .88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 2 .88 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 82 . 00 0 . 00 TC. . . . . 18 . 00 min 0 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 1 .27 cfs VOL: 0 .51 Ac-ft TIME : 480 min BASIN ID: B4 NAME : 2 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 . 60 Acres 2 .28 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 82 . 00 98 . 00 TC. . . . : 12 . 00 min 12 .00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 1 . 07 cfs VOL: 0 . 37 Ac-ft TIME: 480 min 7/15/97 11 : 38 : 13 pm Bush, Roed & Hitchings, Inc page 2 SGA SITE AT WASHINGTON TECH CENTER JOHN E . ANDERSON, P.E . PROJECT NO . 97102 BASIN SUMMARY BASIN ID : B5 NAME: 10 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 . 60 Acres 2 .28 Acres TIME INTERVAL. . . . : 10 . 00 min - CN. . . . : 82 . 00 98 . 00 TC. . . . : 12 . 00 min 12 . 00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 1 . 66 cfs VOL: 0 . 57 Ac-ft TIME : 480 min BASIN ID: B6 NAME : 100 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 .90 inches AREA. . : 0 . 60 Acres 2 . 28 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 82 . 00 98 . 00 TC. . . . . 12 . 00 min 12 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 2 . 32 cfs VOL: 0 . 80 Ac-ft TIME: 480 min d A R N 1 m A O1 1 a 1 a 1 1 1 A A 1 1 R 1 Y7" Y TT7 4 ITT H N N o a N 0 0 0 0 H fl 1 H q A m q c0 a) c0 c0 c0 CO N N N N m 1 l a v q CO CO 0 CO 0 ro N CO OD CO H q 1J R N N N N N N N N N N •� N 1 C Q Q I 0 fl u q U u A N q •rl N R x � Rx tl l a I W u Na 44 W W 14 V4 W qa q iJ q u u u u U u u u u u ro a ( 0 u q N 0 0 N 0 0 m 0 0 N 0 0 l a a 0 Q 1 R r, in H o m m m 0 m m a u N 0 ?+ 0 fl w M N w d d M w I I A x u fl H N H N M H N M Q A x A m N N q W N w Q tl o o o o o o o o o o fl H Q W A OD 00 (0 OD N m N N H fl 1 fl H Z fl tl 0 tl q h f` N M m N m H t, 0 N fl Iv W tl N ri 1, r M N W m w N a 1 a H m 1 N N 0 W M N N M N W fl Q 0 Q w 1 fl W u N 0 o H H H N 0 0 0 ri fl a 1 f� fl a 1 m q N \ fl q N N N 1 q N rl N M d In w r, H N M 0 m N x A H CURTIS II DETENTION POND VOLUME ELEV AREA VOL @ ELEV 17.00 3223.00 0.00 0.00 0.00 18.00 3785.00 1.00 3500.24 3500.24 19.00 4521.00 1.00 4147.55 7647.79 7647.79 a 8/27/97 Bush, Road Hitclzing6, Inc - page S SC--.XL CORD. - Ci7RTI S =2 JOHN E_ ANDERS ON, P-E 97102 mesa-n-:a-s------------v---------: s:s:--»--s--------------------- S TORAGE STRUCTL7RE L S S T STORAGE L 2 S T I D NO_ 1 Da B c r ip t i on: DETENT 2 ON POND a 8/2 7/9 7 Su s ki, RoedC. H i t cri i ng s, I nc _ page 6 SGA CORP_ - CURT 2 S 12 JOHN E_ ANDERS ON, P_E _ 9 7 1 0 2 --------------------------------------------------------------------- D 2 S CHARGE S TRVCTVRE L=S T MULT=P LE OR=F I CE -2D NO_ 1 Description: FRO P-T Ou t l e t E 1 eV: 1 6 _ 9 0 E 1 eV: 3-6 . 90 r t O r i r i c e D i ame t e r: 3 _2 5 00 i n. R T S ER D=S CHARGE I D No_ 2 Description: ova r r 1 ow Riser Diameter (in) : 12 . 00 e1ev: 18 _60 rt weir Coerricierit . . . 3 _ 782 height . 0 .20 rt Orir Coerriciant _ 9 . 739 irncrecn: O _3.0 rt COMB SWAT 2 ON D S S CHARGE I D No. 3 Description: FRO PT W/ OVERFLOW Structure : 1 St ructore Structure: 2 Structure structure : • �8 •�V �10AC) S 8/27/97 13u62i, Roed a HitcYllrig6, Inc . page 7 Sc--A CORP_ - CURT S S 12 JOFII�T E_ ANDERSON, P-E. 973-02 -:--s-m e a s---------s a------m s a-s-------s-s s:-v-----s-m a-------------- LEVEL POOL TABLE SUMMARY MATCH 2 NFLOW Sr D S <-PEAK- STORAGE <--------DESCR2PTSON---------- (cta) (crs) id id id VOL (cE) --s a s-----------:--s--a------�--a:--------e-s--------s-- 2 YEAR - - - - - - - - - - - - - - - - - - - - - - 0 -2 9 1 . 07 1 3 3-7 . 93 1 1 32 1 O YEAR . . . . . . . . . . . . . . . . . . . . . . 0 -7 2 1 - 6 6 1 3 1 8 -5 4 3-2 63 1 O O YEAR - - - - - - - - - - - - - - - - - - - - - 3 -2 7 2 . 32 1 3 1 8 . 8 0 3.3 76 ?r ��Z 2 f 3t (19 3— 1 6.9 u, o � Zy� Dz (T u z U<7 Z CAS •� O'c— aRw�u � V. WATER QUALITY DESIGN x 8/27/97 BusYi, Road R Hitcl-iirium, SnC _ pages 3 Sc--A COR P_ - CVRT 2 S 12 -TOFIN E _ ANDERSON, P_E_ 972.02 --------------------------------------------------------------------- BAS 2N SS MMA4-nW BAS I N MID: 197 NAME : WATER QLIAL S TY S TORM SBLTH METHODOLOGY TOTAL AREA_ _ . . . . _ _ 288 Acres BASEFLOWS : 0 . 00 cra RA=NFALL TYPE . . . . _ VS ER 1 _ PERV 2 OUS AREA O . 6 7 i ric Yta s AREA. . _ 0 . 60 AC=a B T2ME SNTERVAL_ _ _ _ _ 10 . 00 man CN_ . . _ . 82 _ 00 T SME CIE' CONC. . _ _ . _ 3.2 _0 O mi ri =MPERV=OUS AREA AB STRACT S ON COE FF: 0 _2 O AREA_ . _ 2 .2 8 AC=a s CN_ _ _ _ _ 9 8 _ O 0 PEAK RATE : 0 .27 C=6 VOL c 0 . 09 Al--f t T 2 ME: 4 8 O min. �C.l tpow!1� VOW►-^ Q eau i Qc-D D,cat r►.c- FT CURTIS II WETPOND VOLUME PROVIDED ELEV 11 AREA 11 delta H Inc Vol Volume 13.00 572.00 0.00 0.00 0.00 14.00 1162.00 1.00 849.76 849.76 15.00 1391.00 1.00 1274.78 2124.54 16.00 1967.00 1.00 1670.71 3795.25 17.00 3223.00 1.00 2569.29 6364.53 A— rro-rAA-- Vltnpv� Vole PR0uIpl�- �low�>✓ � � CS�� -ems °� �-� µ = 3, g V Arr�a �E�1�b �2• zgac W 435�0 � � l�v) = a 33 S-F < A��t+� VI. LEVEL I ANALYSIS Storm water will be discharged from the detention pond at the pre-developed peak flow rates to a 60-inch pipe located within Southwest 7th Street. From the connection point the storm water will be tight lined approximately 1,100 feet west to Naches Avenue. Storm water is then tight lined north approximately 650 feet in the Naches Avenue storm pipe. From the Naches storm system the storm water is discharged into an open conveyance ditch that flows west into a regional detention basin. The tight line system and detention basin were sized using the Rational Design Method. Current City design standards for peak rate control are more restrictive than used to size the existing system. Therefore, development of this site will not adversely impact the existing storm system. VII. PIPE SIZING CALCULATIONS � \ yi, 07/15/97 STORM SEWER SUMMARY REPORT PAGE 1 OF 1 CURTIS I1. LLC FILE: 97102.STM RAINFALL FILE: SEATTLE.RND 10 YEAR DESIGN STORM I = 13.080/ ( Tc + 5.000) - 0.770 LINE ID 1 FLOW RATE INFO 1 PIPE INFO I HYDRAULIC INFO LINE#1 DESCRIPTION ZINC ARIRUNOFFCIINLTIMEIINLT 111NC CIA1 INPUTQ IUNIFORMISIZE/11NVERT 1PIPE 1 NVAL 1HGLSLOPEIHYD GRD 1 VEL I DOWNLINE# 1TOT ARIWEIGHTDI Tc ITOTL IITOT CIA1 TOTALQ IFLOWCAPITYPE 1UP/DOWN ILEN IINVSLOPI JLC IUP/DOWN 1UP/DOWN I I (ac) 1 C 1 (min) 1(in/h)1 (cfs) 1 (cfs) 1 (cfs) 1(in) 1 (ft) 1(ft) 1(ft/ft)1 (ft/ft)1 (ft) 1 (ft/s) I I I I I I I I I I I I I I I i I OUTFALL-CB1 1 0.41 0.871 0.001 3.791 1.191 0.001 1 12D1 14.931 551 0.0121 0.0071 15.711 3.70 1 DNLN = 0 1 1.91 0.881 12.531 1.441 2.441 2.441 2.71 12D1 14.651 1 0.0051 1.00 1 15.311 4.42 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 CBI-CB4 1 0.11 0.901 0.001 3.791 0.311 0.001 1 12D1 15.381 901 0.0121 0.0011 16.001 2.36 1 DNLN = 1 1 0.91 0.861 11.761 1.491 1.211 1.211 2.71 12D1 14.931 1 0.0051 1.00 1 15.921 1.54 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 1 CB4-CB5 1 0.31 0.851 0.001 3.791 0.801 0.001 1 12D1 15.801 841 0.0121 0.0021 16.251 3.23 1 DNLN = 2 1 0.91 0.861 11.221 1.531 1.121 1.121 2.71 12D1 15.381 1 0.0051 1.00 1 16.081 1.88 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 CB5-CB6 1 0.21 0.851 0.001 3.791 0.711 0.001 1 12D1 16.471 1341 0.0121 0.0031 16.851 2.97 1 DNLN = 3 1 0.61 0.861 10.251 1.611 0.831 0.831 2.71 12D1 15.801 1 0.0051 1.00 1 16.411 1.64 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5 1 CB6-CB7 1 0.21 0.851 0.001 3.791 0.741 0.001 1 12D1 17.001 1081 0.0121 0.0031 17.321 2.61 1 DNLN = 4 1 0.41 0.871 9.341 1.681 0.561 0.561 2.71 1201 16.471 1 0.0051 1.00 1 16.991 1.34 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6 1 CB7-CB8 1 0.21 0.901 8.301 1.781 0.241 0.001 1 12D1 17.441 871 0.0121 0.0031 17.711 2.04 1 DNLN = 5 1 0.21 0.901 8.301 1.781 0.241 0.241 2.71 12D1 17.001 1 0.0051 1.00 1 17.431 0.76 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 7 1 CBI-CB2 1 0.41 0.901 0.001 3.791 1.261 0.001 1 12D1 17.001 1751 0.0121 0.0091 17.421 3.10 1 DNLN = 1 1 0.61 0.901 9.461 1.671 0.951 0.951 4.21 12D1 14.921 1 0.0121 1.00 1 15.921 1.21 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 8 1 CB2-CB3 1 0.31 0.901 8.501 1.761 0.411 0.001 1 1201 17.471 931 0.0121 0.0031 17.831 2.33 1 DNLN = 7 1 0.31 0.901 8.501 1.761 0.411 0.411 2.71 12D1 17.001 1 0.0051 1.00 1 17.561 0.91 07/15/97 STORM SEWER SUMMARY REPORT PAGE 1 OF 1 CURTIS II, LLC FILE: 97102.STM RAINFALL FILE: SEATTLE.RND 100 YEAR DESIGN STORM I = 26.250/ ( Tc + 6.750) - 0.830 LINE ID I FLOW RATE INFO I PIPE INFO I HYDRAULIC INFO LINE#j DESCRIPTION JINC ARIRUNOFFCIINLTIMEIINLT IIINC CIAI INPUTQ JUNIFORMISIZE/lINVERT ]PIPE I NVAL JHGLSLOPEJHYD GRD I VEL DOWNLINE# ITOT ARIWEIGHTD1 Tc ITOTL I1TOT CIAI TOTALQ IFLOWCAPITYPE JUP/DOWN ILEN JINVSLOPI JLC JUP/DOWN JUP/DOWN (ad I C I (min) l(in/h)l (cfs) I (cfs) I (cfs) ](in) I (ft) l(ft) l(ft/ft)l (ft/ft)l (ft) I (ft/s) 1 1 OUTFALL-CB1 1 0.41 0.871 0.001 5.381 1.691 0.001 1 12DI 14.931 551 0.0121 0.0121 16.111 4.85 1 DNLN = 0 1 1.91 0.881 12.521 2.251 3.811 3.811 2.71 12DI 14.651 1 0.0051 1.00 1 15.481 5.48 2 1 CBI-CB4 1 0.11 0.901 0.001 5.381 0.441 0.001 1 12DI 15.381 901 0.0121 0.0021 16.691 2.39 1 DNLN = 1 1 0.91 0.861 11.901 2.311 1.881 1.881 2.71 12DI 14.931 1 0.0051 1.00 1 16.481 2.39 3 1 CB4-CB5 ( 0.31 0.851 0.001 5.381 1.141 0.001 1 12DI 15.801 841 0.0121 0.0021 16.951 2.21 1 DNLN = 2 1 0.91 0.861 11.281 2.381 1.741 1.741 2.71 12DI 15.381 1 0.0051 1.00 1 16.781 2.21 4 1 CB5-CB6 1 0.21 0.851 0.001 5.381 1.011 0.001 1 12DI 16.471 1341 0.0121 0.0011 17.181 2.18 1 DNLN = 3 1 0.61 0.861 10.101 2.521 1.301 1.301 2.71 12DI 15.801 1 0.0051 1.00 1 17.021 1.66 1 1 1 1 1 1 1 1 1 1 1 1 1 ( 1 5 1 CB6-CB7 1 0.21 0.851 0.001 5.381 1.051 0.001 1 12DI 17.001 1081 0.0121 0.0011 17.411 2.96 1 DNLN = 4 1 0.41 0.871 9.231 2.631 0.871 0.871 2.71 12DI 16.471 1 0.0051 1.00 1 17.251 1.31 6 1 CB7-CB8 1 0.21 0.901 8.301 2.771 0.371 0.001 1 12DI 17.441 871 0.0121 0.0031 17.781 2.26 1 DNLN = 5 1 0.21 0.901 8.301 2.771 0.371 0.371 2.71 12DI 17.001 1 0.0051 1.00 1 17.541 0.87 7 1 CBl-CB2 1 0.41 0.901 0.001 5.381 1.791 0.001 1 12DI 17.001 1751 0.0121 0.0061 17.521 3.62 1 DNLN = 1 1 0.61 0.901 9.381 2.611 1.481 1.481 4.21 12D] 14.921 1 0.0121 1.00 1 16.481 1.89 8 1 CB2-CB3 1 0.31 0.901 8.501 2.741 0.641 0.001 1 12DI 17.471 931 0.0121 0.0021 17.931 2.49 1 DNLN = 7 1 0.31 0.901 8.501 2.741 0.641 0.641 2.71 12DI 17.001 1 0.0051 1.00 1 17.721 1.06 09 09 Ob 06 02 OT 0 £i bT Si ��OOB'C) adid -uT ZT 30 -13 99 9T LT m 8T e do Is puno XIB remnI-em 6T OF � nue yq i Z 99 :q -iIA 0 I�3d I'RCD FILE Line 2 CBI-CBA 22 Natural ggoundslope 0.20% [F1] 21 M enu Z 20 0 19 1@ 17 HC3L slope 0.237�a 16 90 fi. of 12 in. pipe (—W 0.500% 15 l+i 13 0 20 40 60 80 STAT I C)N PP ()FI L.E Lirt� 3 CB4-CBS 22 [F1] 21 M enu Natural gxound slope -1.52� 20 � 19 w 18 w17 1-1GL slope 0.2035;1. 16 84 fi. of 12 in. pipe (L�F) 0.500";,,', 15 14 0 10 20 30 40 50 60 70 00 90 STATIQN PR�FIL.� Line 4 CB5-CB6 21 [F1] Menu 20 Natural ground slope 0.00 Z 19 f-r 18 " 134 ft. of 12 in. pipe (g) 0.500'i'o w HGL slope 0.114M'¢ 16 15 14 0 20 40 60 80 100 120 140 STATI�N PR�CJ FILE Line 6 CB7-CB8 23 [F1] lv!enu 22 21 Natural ground slope 2.00 20 w 19 $7 fi. of 12 in. pipe a 0.500" w 18 ~ HG�L. sloloEB 17 16 0 10 20 30 40 50 60 70 80 90 STATI 0 N PR�CJ►FI L.E ...�..� Lirt� 7 CB1-CBS 22 [F1] 21 Menu Natural ground Slope -O.69°T Il ,zr 20 H 19 18 175 ft. of 12 in. pipe (:gp 1. 19O',;o slope O.59637''. 16 15 1q 13 0 20 40 60 80 100 120 140 160 160 ST.PlTI C)N PRE FILE 22 Menu 21 z Natured ground slope 1.0 2'N. 20 19 93 fi. of 12 in. pipe (LD -------------4 HGL slope 0.220!;'.17 16 0 20 40 60 60 100 SPTA-r"r I Q N r nct- CONCEPTUAL DRAINAGE REPORT FOR 6 cSJ'"P l Lra..�l J Y .t � ✓ PARCEL A - WASHINGTON TECHNICAL CENTER LOCATED AT SOUTHWEST 7TH STREET NEAR POWELL AVENUE RENTON, WASHINGTON FOR SGA CORPORATION BY JOHN E. ANDERSON, P.E. 1997 BUSH, ROED & HITCHINGS, INC. 2009 MINOR AVENUE EAST CITY pF REN70NrvING SEATTLE, WA 98102 (206) 323-4144 BRH JOB NO. 97102.00 DATE Z APRIL 24, 1997 6878 N. ISTER�9 AL EXPIRES 12/1/ d17 3_ p,tt EA N V OL.0 nnP- .00 1089.00 0.00 0.00 0.00 0.00 1548.00 2.00 2623.58 2623.58 12.00 2057.00 2.00 3592.96 6216.54 — �'�oM I...1�{o RU C�2�'P K '13� �-�.E ��Z�,u�Q�-b �E.TPo►.�D vo�ur�E = o .oq Ac-FZ = 3, °155 GF 7o vjsTPotQD VOLLU MuST 1�GR-EASE �� A t•r1�r�l �rv.v,ir, vF 3a�o VOLUME FRd�ltpE� 4--(D e-f .a e Ad �w J, z -- 4L 7 VIM EROSION CONTROL 1. The owner may decide to pre-load the building area. This will depend on the availability of material at the time of building permit submittal. Separate pre-load plans have been prepared in the event material can be obtained. The pre-load plan limits work area to the building pad, stock pile area, sediment trap and construction entrances. All other areas will be undisturbed. Pre-loading the building pad will not significantly change the existing storm run off pattern for the site. All storm water run off will be conveyed to the natural low point of the site. The duration of a pre-load should be approximately 2 to 3 months. 2. The ECP for the site utilizes the detention pond for peak rate and sediment control. The detention pond sizing cLiculations show the pond has more than adequate volume for the developed site conditions.. Since the pond meets the developed condition requirements, it will also exceed the requirements for the grading phase. Storm water will be conveyed to the detention pond using interceptor swales. The interceptor swales will have rock check dams to improve sediment removal. The existing railroad tracks are a physical barrier that prevents storm water from leaving the site. Rock construction entrances will be installed at the proposed driveway locations and will help reduce the amount of soil transported to Southwest 7th Street. These measure should be adequate for controlling the drainage during site grading.