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HomeMy WebLinkAboutSWP272255 Sw /� 27- 22f:f' STORM DRAINAGE REPORT _... FOR - RAYMOND AVENUE CENTER RENTON, WASHINGTON BY BUSH, ROED & HITCHINGS 2009 MINOR AVENUE EAST SEATTLE, WA 98102 (206) 323-4144 CONTACT: JOHN E. ANDERSON, P.E. TD r RH JOB NO. 92233. 02 �`� 26F378 W� MARCH 26, 1996 / STE��� � s`sI�NAL� G 3lZo/g4 EXPIRES 12/1/q JUN 1 2 1996 •Z IZF�v�cVC- �-0,5k/�� �5 (v�11���' � S�IILDING (?it�iS10!ti1 Raymond Avenue Center is a 10. 39 acre site located at the southwest quadrant of the intersection of Southwest 19th Street and Raymond Avenue South. The proposed development would occur on Parcel B. Development would include the construction of a 99, 900 square foot building and associated parking. Spring Brook Creek defines the southern and western boundary of the site. The original easement for Spring Brook Creek did not coincide with the actual stream location. Bush, Roed & Hitchings has prepared a lot line adjustment which defines the easements according to the surveyed location of the stream. Lot lines shown on the documents submitted for site plan and shoreline review reflect the most current survey information. Several years ago, the site was filled to approximately elevation 18. Fill slopes toe down to the banks of Spring Brook Creek on the southern and western boundary. On the eastern boundary, the fill slopes toe down approximately 60 feet west of the east property line. Areas east of the fill slopes are classified wetlands. A 60 inch culvert discharges into a ditch on the west side of Raymond Avenue. The ditch is located within the 19th Street right-of-way just north of the north property line. Existing drainage maps indicate the area tributary to the ditch include Panther Creek Wetlands. From the 60 inch culvert, the ditch flows west to Spring Brook Creek. Existing grades on the developable areas are approximately 9 to 10 feet higher than surrounding grades . The ground surface where the proposed development will occur is flat. Tall grasses cover the area. There are no significant trees located within the buildable area. Storm water run-off from the site sheet flows to the surrounding low lands . No defined drainage courses were observed on the site. The proposed site plan maintains a minimum 50 foot setback from Spring Brook Creek and a 25 foot setback from the surrounding wetlands. Storm water run-off from the developed areas will sheet flow to catch basins located in the parking lot . The storm water will then be conveyed directly to a combine wetpond/detention pond facility. A wetpond is required because the development is located next to Spring Brook Creek, and has more than one acre of impervious surface area subject to vehicular traffic. Also, since the storm water will discharge into Spring Brook Creek the detention volume will be calculated using Department of Fisheries guidelines. These standards require a peak discharge rate from the detention system equal to 1/2 the pre-developed 2 year rate for a 10 year developed storm inflow. Peak discharge rates from the detention system for storm events greater than the 10 year match pre-developed peak rates for the same storm event. • Analysis of the combined wetpond/detention pond design shows that it performs significantly better than the Department of Fisheries guidelines . Initial sizing was based on maximizing the available area. The goal was to make the detention volume shallow. By making the detention volume shallow, there is not sufficient head pressure to reach the pre-developed 25 year and 100 year peak discharge rates . The calculations show the developed 25 year and 100 year storm will be discharged at approximately 1/2 the pre- developed 10 year peak rate. Therefore, development of this site will reduce the peak rates for all storm events. Volume provided by the wetpond exceeds the required volume by approximately a factor of three. This is also a result of maximizing the available area. The design guidelines require a 3 foot minimum depth plus 1 foot of sediment storage. Maintaining the depth requirement across the pond provides a storage volume of approximately 28, 846 cubic feet. The required volume is approximately 8, 514 cubic feet. Therefore, the storm water quality will be significantly better than required by Department of Fisheries guidelines . The additional wetpond volume will also mitigate the two small areas filled within the 100 year flood plain (below elevation 16) . reports/92233 . 02 • • I ' r'LONGACRES RACE TRACK \ J m m °tid�d� fn OCIFIC S.W = THOMAS AV W. j]► O RAYMOND AV S.W. Ln Q Z !pi 1 f (VALLEY FREEWAY) ' STATE SIGN ROUTE 167 d Cf .... / Culvert o - RM333 _ K - � RM334 C �6 ZONE X LU Q I I I i I I I. I I I II i I ZONE X 4t 1' ! i li I ZONE ZONE X I I � STREET R I-N-1-0N 188 I 14YATtw�! -�� • CONSIRU( 11UN ! ! b a souTuWF,T ?77 RM338 - STRFFT.. Ftu, IcoYP T c.)rAL 1 Z C C. , Z4 GF y M -CURB BREAK � t a , I, P I---------ta' SS MH TE-19.00+ ~ IE-11.2g EXIST. SS MH 04 30 SS r TH A NUE TE- CH EX I IE-1 64 �� g� SAN SEM]l (RAYMOND AVENUE S IIE-10. ONKOKOJEOJ Gig MICRO Fill till 1OF - . Ira M�R'� ` I Not w PIZ FA I/tR h 1 ji �+w►" r V �� . _�•_�,.� ...,ram,',' :;j.��i►� ��"'"'� 41 .00 �_--war Il A - -gird "! . kir t �i I AM ,f r� elks A o _ I � E� lu �W 3.4 ISOPLUVIALS OF TOTAL • • 1 1 • • ' P Ij • ` PAN IIA Ila PNI E, •mob:��.,� ;� _ 4 Ewa► � � `�*w� , lw,w l►'ii f ,. I���i►;'mow, � • / KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL *gE3-5.2B SCS %N' -STERN WASHINGTON RUNOFF CURVE NUMBERS ------ l SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type to 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 94 95 Mountain open areas: low growing brush and grasslands 74 82 89 92 65 78 85 89 Meadow or pasture: Wood or forest land: undisturbed or older second growth 42 64 76 81 Wood or forest land: young second growth or brush 55 72 81 86 81 88 92 94 Orchard: with cover crop Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75%. 68 86 90 or more of the area (D fair condition: grass cover on 50% to 75% of the area 77 92 Gravel roads and parking lots 76 85 89 91 72 82 87 89 Dirt roads and parking lots i Impervious surfaces, pavement, roofs, etc. 98 98 98 98 s, ponds, etc. 100 100 100 100 Open water bodies: lakes, wetland Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall 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 is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. 3.5.2-3 I1/92 i 3/10/96 Bush, Roed & Hitchings, Inc. page 1 Raymond Industrial Center 40 John E. Anderson, P.E. 92233 ----------- -------------------- BASIN SUMMARY BASIN ID: B1 NAME: 2 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2.00 inches AREA. . : 5.24 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 0.31 cfs VOL: 0.25 Ac-ft TIME: 490 min BASIN ID: B2 NAME: 10 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2.90 inches AREA. . : 5.24 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30.30 min IMPERVIOUS AREA ' ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 0.89 cfs VOL: 0.51 Ac-ft TIME: 480 min BASIN ID: B3 NAME: 25 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3.40 inches AREA. . : 5. 24 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30.30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 1.27 cfs VOL: 0.68 Ac-ft TIME: 480 min 2 3/10/96 Bush, Roed & Hitchings, Inc. page 2 Raymond Industrial Center John E. Anderson, P.E. 92233 BASIN SUMMARY BASIN ID: B4 NAME: 100 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3.90 inches AREA. . : 5.24 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 1.68 cfs VOL: 0.86 Ac-ft TIME: 480 min BASIN ID: B5 NAME: 2 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5. 24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2.00 inches AREA. . : 0.31 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 4.93 Acres CN. . . . . 98.00 PEAK RATE: 2 .05 cfs VOL: 0.74 Ac-ft TIME: 480 min BASIN ID: B6 NAME: 10 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2.90 inches AREA. . : 0. 31 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16.30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 4 .93 Acres CN. . . . . 98.00 PEAK RATE: 3 .08 cfs VOL: 1 . 13 Ac-ft TIME: 480 min i 3/10/96 Bush, Roed & Hitchings, Inc. page 3 Raymond Industrial Center John E. Anderson, P.E. 92233 ------------------------ BASIN SUMMARY BASIN ID: B7 NAME: 25 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3.40 inches AREA. . : 0.31 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 4 .93 Acres CN. . . . . 98.00 PEAK RATE: 3 .65 cfs VOL: 1. 34 Ac-ft TIME: 480 min BASIN ID: B8 NAME: 100 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5.24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3.90 inches AREA. . : 0. 31 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 4.93 Acres CN. . . . . 98.00 PEAK RATE: 4.22 cfs VOL: 1.56 Ac-ft TIME: 480 min BASIN ID: B9 NAME: PTWQ VOLUME FOR WETPOND SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5. 24 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 0.67 inches AREA. . : 0.31 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 4.93 Acres CN. . . . . 98.00 PEAK RATE: 0.54 cfs VOL: 0. 20 Ac-ft TIME: 480 min i 2 3/10/96 Bush, Roed & Hitchings, Inc. page 1 Raymond Industrial Center John E. Anderson, P.E. 92233 HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf-AcFt Acres --------------------------------------------- --------------------------------------------- 1 0. 314 490 10699 cf 5. 24 2 2 0. 888 480 22360 cf 5. 24 �o '�e �X,sTi �Ca ----------- --- 3 1 . 272T---4-80--- — -29624--cf ----5. 24- 25 -g -T as co --4—_ I-.68 2-------4 8 0 - -----3 7 2 6 9_c f - 5. 24 �00 1'12 EX�ST�►.JC� b -2-:053 480-------32387 -cf --------5 -24_-_-_---Z 6 3 .-081---480 - - -49081 cf 5.24 __. 1 0 `(2 D E�.tE�''c(� \tit Fl.o W T —3.653 4-80------58425---cf --- -- -._5=24-. - - ----8 4.224 480 --67800 cf -- 5. 24 _ Z5 -`�fR C�C�./EI�'PED t T.ir�3 9 0.54 ---480 -- 8514 cf - 5.24 goo t(R. DEVEyOPED I,.1F�w .. P Tv.l 4 �o R w ET'Fb nJ D �!o W vv�E 11 0.153 1470 22217 cf --5.24 12 0.4�2�-1070 _-.__ -31003 cf - 5.24 toYsZ po�v RE��s� --____-- ---- _ _ 2S YR orb r,tP RELET�S'E 13 0.675 900 40325 cf 5.24 1�oiR poNd �t�RS� - _ Dt:TEtsTto►.t Pat.lc� 17>:S1C�t�l rd��>,�N F'�sN�z.�tS DEs�b,t.l STP.I.�DR2D5, I • h.t.�..owAT3�E REI.ERSE SATE FoR �p `�EA'R Dt�l£t..opC-p INFLo>� YZ, PRE - t7 E V�l PC D PCPt�G iZc.TE. �/Z PK6-pEVE�pQED = (D/2= ©.314/2 a D . 15-1 c.�s 1 p `j��tu C7EvEl..oP�t� = fo = 3 o�IGFS p.�rt:rJ T►o N Pow v �ELE L'+S£ = 1� = O. 15 3 C.�S � O. •I S'1 c.'F S ✓ Z, At✓�ow►o.�3LE REUc1�5E 1ZATE5 FOR Z5 '(EF-k9- D too�e+'�R �EvEw�E� 1�+>=ww5 Must 1.�oT f�G L�Rr'1 Tt�f �.l THE �aE - nEvEwPtr� PEp.k tz�T�s. p., PRE�bEvEwpEr� 25 `�2 Pc�•k.= 3O = 1t2'1'2 ��5 �7ETENTi � "FUND REUcY-t5£= O = O• �I-2(oL,GS �/ TE f•►-f1 o r`1 PoN t� C-Z E l�►P�s = i`3 - p , ro"'15 C-F s ✓ 3. T�+E �ETEN'�io1.1 �o1J1> �XLEET�� its N EtzIES 5rp,►,j vJ&T p0r.1 D VOLt)&A E FE6 L)1 e Ed E--Q vALS p7vjQ STORM vat'V fvj 6 P-r•,u VOL_ Q = 8 S 14 Cr YOLv►\4E 17R0v10 ?-00 oCF c/ = 3/10/96 Bush, Roed & Hitchings, Inc. page 2 Raymond Industrial Center John E. Anderson, P.E. 92233 STORAGE STRUCTURE LIST STORAGE LIST ID No. 1 Description: DETENTION POND A Aw-To Go r-> bES16►.1 Zo SF �OZ SF viCTPo D 2-a1 SF SF C2E'CG►,171 C)Q VoL-u t A G l l , 0 13 812 SF �O'R too YsZ SToRtrt 13,b 1Cc 13r7 5 FoIZ Ioo �R STORKn 14 ,0 17 Zq4 51= = tz,oq �.t7D 1Ti oN��- Vot-.0 M'C ?9 Coy kDED • t 3/10/96 Bush, Roed & Hitchings, Inc. page 3 Raymond Industrial Center John E. Anderson, P.E. 92233 DISCHARGE STRUCTURE LIST MULTIPLE ORIFICE ID No. 1 Description: FISHERIES DESIGN RELEASE Outlet Elev: 9.00 Elev: 9.00 ft Orifice Diameter: 1.8100 in. Elev: 12.00 ft Orifice 2 Diameter: 8.0000 in. D VET - LEV i— E���/ Z, a i � I 2 3/10/96 Bush, Roed & Hitchings, Inc. page 4 Raymond Industrial Center John E. Anderson, P.E. 92233 LEVEL POOL TABLE SUMMARY MATCH INFLOW ST DI <-PEAK-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) id id <-STAGE> id VOL (cf) 1/2-2 YR. FOR 10 YR . . . . . . . . . . 0. 31 3.08 1 1 11.98 11 397 25 YEAR STORM . . . . . . . . . . . . . . . . 1. 27 3. 65 1 1 12.05 12 408 100 YEAR STORM 1.68 4.22 1 1 12.09 13 415 i J ile Basin Hydrograph Storage Discharge Level pool Bush, Roed & Hitchings, Inc. 2 ROUTING COMPARISON TABLE MATCH INFLOW STO DIS PEAK PEAK OUT DESCRIPTION PEAK PEAK No. No. STG OUT HYD 1/2-2 YR. FOR 10 YR 0. 31 3 .08 1 1 11.98 0.15 11 25 YEAR STORM 1.27 3 .65 1 1 12.05 0.43 12 100 YEAR STORM 1.68 4 . 22 1 1 12.09 0.68 13 ______====>Done<====_______= F10 to Exit Available Memory remaining: 151037 bytes Current Data Set Name: a:\92233 le Basin Hydrograph Storage Discharge Level pool Bush, Roed & Hitchings, Inc. 2 ROUTING COMPARISON TABLE MATCH INFLOW STO DIS PEAK PEAK OUT DESCRIPTION PEAK PEAK No. No. STG OUT HYD 1/2-2 YR. FOR 10 YR 0. 31 3 .08 1 1 11.98 0.15 11 25 YEAR STORM 1. 27 3 .65 1 1 12.05 0.43 12 100 YEAR STORM 1.68 4 . 22 1 1 12.09 0.68 13 ______====>Done<====_______= F10 to Exit Available Memory remaining: 151037 bytes Current Data Set Name: a:\92233 • BUSH,ROED&HTTCHINGS,INC. JOB CIVIL ENGINEERS &LAND SURVEYORS SHEET NO. Of 2009 Minor Avenue East Seattle,WA 98102 CALCULATED BY DATE (206)323-4144 • BRH (206)323-7135 • Fax CHECKED BY DATE SCALE y A-7! y,.).S E Tyr 6Z 2S 0, log; 7-Hf JSC-SS CA-" ULA-TE 4 PG>,�JTS or-1 C v2QE 2 15 pyl:nJfc� =is =(3. 4) CZ.(06 30 0 F-f 77 6 i4'V o PRODUCT 20/-1(SNk SWS)205.1 f goped1.®a m<Grow Mass Ci a:t to D•de'PHONE TOLE FREE 1 800.225 63K BUSH, ROED & HITCHINGS, INC. JOB G 2���. o Z RAY►�o►Jt� CIVIL ENGINEERS & LAND SURVEYORS SHEET NO, OF 2009 Minor Avenue East CALCULATED BY �P � DATE Seattle,WA 98102 l' (206)323-4144 CHECKED BY DATE i R (206)323-7135 • Fax SCALE A-Y �E i.I T�►-1 � �-�A�Nt �r--�Ca T O T H CG Foy o�J Li G��V c.J L A T,.-> cz�— ,OJ TEy F ✓AIp Im(Z XT6e L DE .scam► ti..;... �+�t .�..i►J.v .... ........... _ ........... T►-4� ... x15T�►J,t-a._:......._St..T�`�-_ ►_5 .. ._... ._ .UR-�2t�..�'t.'u-!. __ ... . .. .. ---._ ..__.. ...... y ....._. T F r-�- A,rn o.j J 7- at5i�,.r��'� AteA p. ►� _ '�1. 1_$." T4 16-- - _.�'L ►oJ�SE.�Dir-'1cJ.T 1-0 _Po►J P 71-14 _ _: �1. "AGP-f3S. 1►,l ro 3 57eP6v�►�► L �As,►Js. (� a-[��t�+-moo _ M/�P Fo� �Tw�,�5) _. .. io it PEAS►►-� �` i.IoQTK� 2 .53 Ace A c� C7/�� 5t�1MV+Ji �O•J� 4� 1`� & l�(�0111 0c y:) �r T2— • moouci�,rsr►sr.�zos,pme�®.rK�.�oun,o a..r,+o�rou�E uooas�eo i I/22/95 Bush . Roed & Hitchings , Inc. page 1 Winmar John E. Anderson, P.E. storm disk-92233 HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf-AcFt Acres 1 0. 298 490 10148 cf 4 .97 2 0. 843 480 21207 cf 4.97 3 1 . 206 480 28097 cf 4.97 4 1 . 596 480 35348 cf 4.97 5 1 .955 480 30824 cf 4.97 6 2.932 480 46683 cf 4.97 7 3 .474 480 55555 cf 4.97 8 4 .016 480 64455 cf 4.97 9 0. 515 480 8068 cf 4 .97 11 0.129 1470 19342 cf 4.97 12 0. 397 1450 26581 cf 4.97 13 0. 504 1030 35290 cf, 4.97 14 0, 281 480 6157 cf 1 .65 Ea�T gAs��.l • 15 0.431 480 9441 cf 2. 53 qog-T►i a Ac%O 16 0 , 511 480 11194 cf 3 .00 vleGT E^5*4 • KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL 5.4.5.1 SEDIMENT TRAP Code: ST Symbol: Purpose To remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually only result in a small reduction in turbidity. Conditions of Use 1. A sediment trap shall be used where the contributing drainage area is 3 acres or less. Design and Installation Specifications 1. See Figure 5.4.5.11A for detail. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see the introduction to this section). 3. To determine the trap geometry, first calculate the design surface area (SA) of the trap, measured at the invert of the weir . Use the following equation: SA = FS(Q2/Vs), where: Q2 = Design inflow based on the peak discharge from the developed 2-year, 24-hour design storm from the contributing drainage area as computed in the hydrologic analysis. The 10-year, 24-hour design storm shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the rational method may be used (Section 4.3.3). Vs = The settling velocity of the soil particle of interest. The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs) of 0.00096 ft/sec. FS = A factor of safety of 2 to account for non-ideal settling. Therefore, the equation for computing surface area becomes: SA =2 x Q2/0.00096 or 2080 square feet per cfs of inflow NOTE: Even if permanent facilities are used, they must still have a surface area that is at least as large as that derived from the above formula. If they do not, the pond must be enlarged. 4. To aid in determining sediment depth, all traps shall have a staff gauge with a prominent mark 1 foot above the bottom of the trap. 11/94 KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL FIGURE 5.4.5.11A SEDIMENT TRAP SURFACE AREA DETERMINED - AT TOP Of WEIR �' MIN. 1' MIN. OVERFLOW Jy 1' MIN. f_ 1' MIN. it FLAT BOTTOM RIPRAP 3/4"-1.5" 2"-4" ROCK WASHED GRAVEL GEOTEXTILE NOTE: TRAP MAY BE FORMED BY BERM OR BY DISCHARGE TO STABILIZED PARTIAL OR COMPLETE EXCAVATION CONVEYANCE, OUTLET OR LEVEL SPREADER CROSS-SECTION 6* MIN. =1 I M I Ed I F1 I Ed I 1=11 1• MIN. DEPTH OVERFLOW SPILLWAY —III—III—III—III—I{I=1 i i=11 r=Ti=i i�1i1=11�l I I L—ii=lil=lil=1 i�i l r- II -I MIN. 1' DEPTH NATIVE SOIL OR iI I . :j• ` _ - 2"-4' ROCK COMPACTED BACKFILL _ MIN. 1' DEPTH 3/4"-1.5" GEOTEXTILE -.I 11=I I I—III—I I{=I I f—III—III I {=I I I— WASHED GRAVEL • _{I l-1 I�I I I-1 I I-1 I l-1 I�{I I={I�I TRAP OUTLET Maintenance Standards 1. Sediment shall be removed from the trap when it reaches 1 foot in depth. 2. Any damage io the trap embankments or slopes shall be repaired. 5.4.5.2 SEDIMENT POND Code: SP Symbol: Purpose To remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually reduce turbidity only slightly. Conditions of Use 1. A sediment pond shall be used where the contributing drainage area is 3 acres or more. 5.4.5.2-1 11/94 BUSH,ROED& HTTCHINGS, INC. roe CIVIL ENGINEERS & LAND SURVEYORS SHEET NO, OF 2009 Minor Avenue East Seattle,WA 98102 CALCULATED BY DATE (206)323-4144 CHECKED BY DATE B R H (206)323-7135 - Fax SCALE C.�SC ��J,A�1 0� 'Fob 5J✓LF�-� /4Q�� '�C�J�2EM^L:.� tie�s i�Ar-t►-� '� x St l �Fs c7. DO®`lam -_.......__........:__. ......... .... .. . -2A 2_.. ............ _ t... . _ ._ . ... .... 0 .000 . __ �A� s-La..� (--�CZ 0.����.oP EEO Go,J O�►t o�S. PRDDLV M I*0 5MMI M 1(rrm)®.IK.GOM U-01471 To aan nnM[TOLL FW V4*225.4W 04 7/96 STORM SEWER SUMMARY REPORT PAGE 1 OF 2 RAYMOND CENTER FILE: 92233C.STM RAINFALL FILE: CHARTIO.RND 25 YEAR DESIGN STORM I - 16.930/ ( Tc + 5.200) ^ 0.792 LINE ID I FLOW RATE INFO I PIPE INFO I HYDRAULIC INFO LINE#j DESCRIPTION JINC ARIRUNOFFCIINLTIMEIINLT IIINC CIAI INPUTQ JUNIFORMISIZE/lINVERT IPIPE I NVAL IHGLSLOPEIRYD GRD I VEL DOWNLINEA ITOT ARIWEIGHTD1 Tc ITOTL IJTOT CIAO TOTALQ IFLOWCAPITYPE JUP/DOWN GLEN JINVSLOPJ JLC JUP/DOWN JUP/DOWN (ac) C I (win) l(in/h)l (cfe) I (cfa) I (cfa) l(in) I (ft) 1(ft) l(ft/ft)l (ft/ft)l (ft) I (ft/6) 1 1 cbl to pond 1 0.01 0.901 0.001 4.591 0.001 0.001 1 24DI 9.141 381 0.0131 0.0011 12.041 2.41 1 DNLN - 0 1 5.41 0.901 15.271 1.551 7.571 7.571 13.81 24DI 9.001 1 0.0041 1.00 1 12.001 2.41 2 1 cb2 to cbl 1 0.41 0.901 0.001 4.591 1.531 0.001 1 18DI 9.411 721 0.0131 0.0041 12.451 3.97 1 DNLN - 1 1 5.01 0.901 14.971 1.571 7.021 7.021 6.41 18DI 9.141 1 0.0041 1.00 1 12.131 3.97 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 1 cb3 to cb2 1 0.31 0.901 0.001 4.591 1.401 0.001 1 18DI 10.251 2271 0.0131 0.0021 13.121 2.54 1 DNLN - 2 1 3.01 0.901 13.491 1.671 4.491 4.491 6.41 18DI 9.411 1 0.0041 1.00 1 12.701 2.54 4 1 cb4 to cb3 1 0.61 0.901 0.001 4.591 2.271 0.001 1 18D] 11.021 2071 0.0131 0.0021 13.551 2.40 1 DNLN - 3 1 2.61 0.901 12.041 1.781 4.241 4.241 6.41 18DI 10.251 1 0.0041 1.00 1 13.221 2.40 1 cb5 to cb4 1 0.61 0.901 0.001 4.591 2.401 0.001 1 18DI 11.411 1051 0.0131 0.0011 13.761 1.98 1 DNLN - 4 1 2.11 0.901 11.151 1.851 3.501 3.501 6.41 18DI 11.021 1 0.0041 1.00 1 13.641 1.98 6 1 cb6 to cb5 1 1.01 0.901 0.001 4.591 4.211 0.001 1 18DI 11.851 1181 0.0131 0.001l 13.901 1.53 1 DNLN - 5 1 1.51 0.901 9.841 1.981 2.711 2.711 6.41 18DI 11.411 1 0.0041 1.00 1 13.821 1.53 7 1 cb7 to cb6 1 0.51 0.901 6.301 2.451 1.101 0.001 1 12DI 13.461 3231 0.0131 0.0011 14.291 1.67 1 DNLN - 6 1 0.51 0.901 6.301 2.451 1.101 1.101 2.51 12DI 11.851 1 0.0051 1.00 1 13.941 1.40 I I I I I I I I I I I I I I 8 I CB9 - CB1 1 0.31 0.901 0.001 4.591 1.201 0.001 1 12DI 11.211 791 0.0131 0.0011 12.181 1.16 1 DNLN - 1 1 0.41 0.901 7.711 2.231 0.911 0.911 5.81 12DI 9.141 1 0.0261 1.00 1 12.131 1.15 9 1 CBS - CB9 1 0.21 0.901 6.301 2.451 0.351 0.001 1 12DI 14.211 1141 0.0131 0.0201 14.541 2.27 1 DNLN - 8 1 0.21 0.901 6.301 2.451 0.351 0.351 5.81 12DI 11.211 1 0.0261 1.00 1 12.201 0.45 10 1 CB10 -CB2 0.71 0.901 0.001 4.591 2.811 0.001 1 12DI 10.891 1311 0.0131 0.0071 13.591 3.73 1 DNLN - 2 1.61 0.901 9.461 2.021 2.931 2.931 3.81 12DI 9.401 1 0.0111 1.00 1 12.701 3.73 11 1 CBI 1. - CB10 1 0.31 0.901 0.001 4.591 1.201 0.001 1 12DI 14.201 2931 0.0131 0.0041 14.841 3.49 1 DNLN - 10 1 0.91 0.901 7.811 2.221 1.861 1.861 3.81 12DI 30.891 1 0.0111 1.00 1 13.811 2.37 12 1 CB12 - CBll 1 0.31 0.901 0.001 4.591 1.401 0.001 1 12DI 15.361 1021 0.0131 0.0081 15.851 3.49 1 DNLN - 11 1 0.61 0.901 7.171 2.311 1.331 1.331 3.81 12DI 14.201 1 0.0111 1.00 1 15.031 1.91 13 1 CB13 - CB12 1 0.31 0.901 6.301 2.451 0.661 0.001 1 12DI 16.531 1021 0.0131 0.0091 16.991 2.75 DNLN - 12 1 0.31 0.901 6.301 2.451 0.661 0.661 3.81 12DI 15.361 1 0.0111 1.00 1 16.041 1.17 04/17/96 STORM SEWER SUMMARY REPORT PAGE 1 OF 2 RAYMOND CENTER FILE: 92233C.STM RAINFALL FILE: CHARTIO.RND 100 YEAR DESIGN STORM I - 21.753/ ( Tc + 5.600) - 0.787 AMk LINE ID FLAW RATE INFO PIPE INFO HYDRAULIC INFO LINE11 DESCRIPTION JINC ARIRUNOFFCIINLTIMEIINLT IIINC CIAI INPUTQ JUNIFORMISIZE/INVERT IPIPE I NVAL IHGLSLOPEIHYD GRD I VEL DOWNLINEO ITOT ARIWEIGHTD1 Tc ITOTL IJTOT CIA) TOTALQ IFLOWCAPITYPE JUP/DOWN ILEN JINVSLOPJ JLC JUP/DOWN JUP/DOWN (Ac) I C I (sin) l(in/h)l (cfs) I (cfs) I (cfs) l(in) I (ft) ((ft) l(ft/ft)l (ft/ft)l (ft) I (ft/0) 1 cbl to pond 1 0.01 0.901 0.001 5.611 0.001 0.001 1 24DI 9.141 381 0.0131 0.0021 12.081 3.34 DNLN - 0 ( 5.41 0.901 13.341 2.151 10.501 10.501 13.81 24DI 9.001 1 0.0041 1.00 1 12.001 3.34 2 cb2 to cbl 1 0.41 0.901 0.001 5.611 1.871 0.001 1 18DI 9.411 721 0.0131 0.009) 12.871 5.50 1 DNLN - 1 1 5.01 0.901 13.131 2.171 9.711 9.711 6.41 18DI 9.141 1 0.0041 1.00 1 12.261 5.50 1 1 1 1 1 1 1 1 1 1 1 1 { 1 1 3 1 cb3 to cb2 1 0.31 0.901 0.001 5.611 1.721 0.001 1 18DI 10.251 2271 0.0131 0.0031 14.111 3.46 1 DNLN - 2 ( 3.01 0.901 12.041 2.281 6.121 6.121 6.41 18DI 9.411 1 0.0041 1.00 1 13.341 3.47 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 cb4 to cb3 1 0.61 0.901 0.001 5.611 2.781 0.001 ( 18DI 11.021 2071 0.0131 0.0031 14.911 3.23 1 DNLN - 3 1 2.61 0.901 10.981 2.391 5.701 5.701 6.41 18DI 10.251 1 0.0041 1.00 1 14.301 3.23 5 1 cb5 to cb4 1 0.61 0.901 0.001 5.611 2.931 0.001 1 18DI 11.411 1051 0.0131 0.0021 15.281 2.64 1 DNLN - 4 1 2.11 0.901 10.311 2.471 4.661 4.661 6.41 18DI 11.021 1 0.0041 1.00 1 15.071 2.64 1 1 1 1 1 1 ( 1 1 1 1 1 1 1 1 6 1 cb6 to cb5 1 1.01 0.901 0.001 5.611 5.151 0.001 1 18DI 11.851 1181 0.0131 0.0011 15.531 2.01 1 DNLN - 5 1 1.51 0.901 9.331 2.591 3.551 3.551 6.41 18DI 11.411 1 0.0041 1.00 1 15.391 2.01 - to cb6 ( 0.51 0.901 6.301 3.101 1.401 0.001 1 12DI 13.461 3231 0.0131 0.0021 16.131 1.78 DNLN - 6 0.51 0.901 6.301 3.101 1.401 1.401 2.51 12DI 11.851 1 0.0051 1.00 1 15.591 1.78 8 I CB9 - CHI 1 0.31 0.901 0.001 5.611 1.461 0.001 1 12DI 11.211 791 0.0131 0.0011 12.341 1.48 1 DNLN - 1 1 0.41 0.901 7.571 2.861 1.161 1.161 5.81 12D] 9.141 1 0.0261 1.00 1 12.261 1.48 9 1 CB-8 - CB9 1 0.21 0.901 6.301 3.101 0.451 0.001 1 12DI 14.211 1141 0.0131 0.0191 14.591 2.44 1 DNLN - 8 1 0.21 0.901 6.301 3.101 0.451 0.451 5.81 12DI 11.211 ( 0.0261 1.00 1 1.2.371 0.57 10 1 CB10 -CB2 1 0.71 0.901 0.001 5.611 3.431 0.001 1 12DI 10.891 1311 0.0131 0.0111 14.761 4.70 1 DNLN - 2 1 1.61 0.901 9.691 2.551 3.691 3.691 3.81 12DI 9.401 1 0.0111 1.00 1 13.341 4.70 1 1 1 1 1 1 1 1 1 1 1 ( 1 1 F 11 1 C811 - CB10 1 0.31 0.901 0.001 5.611 1.461 0.001 1 12DI 14.201 2931 0.0131 0.0041 16.361 2.98 1 DNLN - 10 1 0.91 0.901 7.981 2.801 2.341 2.341 3.81 12DI 10.891 1 0.0111 1.00 1 15.101 2.98 1 1 1 1 1 1 1 1 1 1 1 1 ( 1 1 12 1 CB12 - CB11 1 0.31 0.901 0.001 5.611 1.721 0.001 ( 12DI 15.361 1021 0.0131 0.0021 16.731 2.15 DNLN - 11 1 0.61 0.901 7.151 2.941 1.691 1.691 3.81 12DI 14.201 1 0.0111 1.00 1 16.501 2.16 13 1 CB13 - CB12 1 0.31 0.901 6.301 3.101 0.841 0.001 1 12DI 16.531 1021 0.0131 0.0021 17.061 2.66 1 DNLN - 12 1 0.31 0.901 6.301 3.101 0.841 0.841 3.81 12DI 15.361 ' 0.0111 1.00 1 16.811 1.07 0 • i • PRE]FILE 13 Line 1 cb Ito pond 20 [F1] Menu 18 r4mturel ground slope 0.533;'o 14 ~ 16 14 w HC3L slopa 0.112370 12 10 38 ft. of 24 in. pipe 0.370% 8 0 5 10 15 20 25 30 35 40 STATI O N PRC�FILE Lime 2 cb2 to cb 1 20 [F1] Menu 1$ Zi Natural ground slope -1.467 14 w 14 HOL slope 0:447!;,a _.. _.. _ . _.. -.. _.. _ - - 12 10 72 fi. of 18 in. pipe Cu-) 0.370,7 8 0 10 20 30 40 50 60 70 80 STATI O N PRE FILE 3- Line 3 cb3 to cb2 20 [F1] M enu 18 Natural ground slope 0.55326' ~ 16 w 14 HC1, slope 0.1S3?o 12 228 ft. of 18 in. pipe 0.970% 10 8 0 50 100 150 200 250 STATI O N PRt3 FILE Lines 4 cbA to cks3 -q 20 [Flj M enu 1$ atural ground slope -1.54% ~ 16 14 HOL slope 0.163% w 12 208 ft. of 18 in. pipe c� 0.370%0 10 8 0 50 100 150 200 ST�4TI�N PRE FILE Lines 5 cb5 to cb4 16 [F1] Menu 15 QNaiural ground =lope 0.00% ~ 14 HGi L, slope 0.11137o w 13 w106 ft. of 18 in. pipe @ 0.3701Pb 12 11 10 0 20 40 60 80 100 120 STA.TI O N PR0FII- E Line 6 cb6 to cb5 6 � 16 [F1] Menu 15 Natural ground slope -0.08'.M' w 13 � 118 ft. of 18 in, pipe a� 0.370�4 w 12 11 10 0 20 40 60 80 100 120 STATI c:)N I�R�FILE Line 7 cb7 to cb6 7 1s �F1] Menu 17 16 Q Natural ground slope 0.59% 15 ft. of 12 in. pipe (9) O.500%o 14 w 13 12 11 10 0 50 100 150 200 250 300 350 STATI O N PRE►FI LE Line 8 CS9 - CB1 20 [F1] Menu 18 Natural gar ourld slope -1.01 ~ 16 w 14 w 12 _.. _.. _.. _.. _.79..fs_.of. 12.in_pipa .2.61OIo. _.. _.. _.. _. HGi L- slope 0.059� 10 8 0 10 20 30 40 50 60 70 80 STATI�N • • i PRE FILE Line � �B8 - CB9 18 [F1] 17 Natural ggourxd slope 0.2697. Menu 16 15 _ 115 ft. of 12 in. pipe Q 2.61 w 14 w 13 ---HCFL:. slope 2. o 12 11 10 0 20 40 60 80 100 120 STATI�N PRC)FILE Line 10 C1310 -CO2 18 [F1] Natural ground slope O-19% Imenul y lb 14 HGL_ slope O.67610- PLI w 12 32 ft. of 12 ir.. pipe 10 $ 0 20 40 60 80 100 120 140 STATI O N s • ! PRO FILE 11. L in-e 11 CD 11 - CO 10 22 [F1j Menu 20 'z Nextural Sr oiund 51 op a 1.O 4% Q 18 16 293 ft. of 12 in. pipe g� 1: 130 12 10 S 0 50 100 150 200 250 300 STATI O N PR0 FILE 1� Line 12 CB 12 - CB 11 21 (F1] Menu 20 Natural gxound slope 0.00% � 19 18 w 17 103 ft. of 12 in. pipe (g) 1. 130%a w 16 - 1s .. _. _ . r . - • - HGL slope 0.798 14 13 0 20 40 60 80 100 120 STATI O N PRE FILE •13 Line 13 CB 13 - CB 12 21 (FS] Menu 20 Natural gx ound 51 op a 0.00 Q 19 18 w103 ft. of 12 in pipe 0 1- 130% 17 - -ffdL slope 0.92 16 15 14 0 20 40 60 80 100 120 STATI Q N