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HomeMy WebLinkAbout02785 - Technical Information Report - Storm Drainage Calculations DODDS ENGI INC. M� ^ � STORIVI DRAINAGE CALCULATIONS for TALBOT ROAD RENTON, WASHINGTON Ca�'Ft T J Prepared For: Bumstead Constiuction Co. r�,��:'04'" �. Prepared By : Brennan P. Tayior,P.E. �, Approved By: Edgar T. Jones,P.E. — , a DEI Project No.: 94172 �cv ' Mazch 1998 • 9 0;• �. ,,.. .• � � ,•LC,. Planning•Engineering•Surveying �' 7'� 4205-148thAvenue NE Suite 200 Bellevue,Washington 98007 A�5�$v'��' � Tel.425-885-7877 Fax.425-885-7963 z 78 5"' E Mail.o�ce@DE►online.com TABLE OF CONTENTS I. PROJECT OVERVIEW II. OFF-SITE ANALYSIS III. EXISTING SITE CONDITIONS IV. DEVELOPED SITE CONDITIONS V. PROPOSED DETENTION DESIGN SLTMMARY VI. CONVEYANCE CALCULATIONS I. PROJECT OVERVIEW The proposed project of Talbot Road is situated on approximately 26.6 acres in south Renton, of which approximately 22 acres will be developed. The site is located just east of Highway 167 and west of Talbot Road, approximately 1500 feet south of S.W. 43rd Street. The proposed project includes 240 units in 53 separate townhouse and condominium buildings. Access to the site will be from Talbot road, with a private street system through the development. The east half of the site is moderately sloped to the west at 3% to 10%. This area is presently developed with several residences, outbuildings and pasture area. The western portion of the proposed developed area continues to slope to the west at 8%to 30%. Much of this area is covered with second growth forest. The faz west portion of the site will not be developed due to steeper slopes and wetlands. The King County Soils Survey map indicates that the soils onsite are classified as `Alderwood', hydrologic group C. Drainage onsite will be collected and conveyed to a detention vault in the southwest corner of the site. All roofdrains will be tightlined to the conveyance system and all road runoff will be collected. The detention facility will be designed to Department of Ecology criteria for release rates and water quality treatment. The detention vault will discharge to a biofiltration swale prior to release into the e�cisting wetland. This drainage analysis is based on SBUH methodology and utilizes the WaterWorks hydrology program to generate and manipulate hydrographs. --- a;a� -- '---��N'.."' 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The north property is 1.69 acres in size and consists of two separate building structures and a small pond. The south property is 0.74 acres in size and consists of one building structure. The remaining portion of both properties is covered with grass. Drainage flows to the west onto the proposed development and will be intercepted by the onsite drainage system and conveyed through the detention system. An offsite drainage basin of approximately 36.79 acres, contributes runoff to the roadside ditch on the east side of Talbot Road South. A portion of the flows from the basin are intercepted in a 12" CPEP which travels under Talbot Road South and dischazges into a catch basin. The catch basin is located approximately 180 feet south of the northeast property corner of the proposed site. The existing catch basin has a solid lid and consists of the 12" CPEP described above along with a 4"PVC outlet pipe. Flow out of the catch basin is restricted by a 4"PVC which travels west and discharges into a small decorative/landscape pond on the property. Drainage in the 12" CPEP eventually backs up due to the restriction of the 4"PVC. Drainage not intercepted by the 12" CPEP or drainage that has backflowed back into the ditch along Talbot Road South, flows south in the ditch where it is intercepted by a 18" CPEP. The 18" CPEP which travels under Talbot Road South is located approximately 670 feet south of the northeast property comer of the proposed site. The 18" CPEP appears to have been recently installed or improved. The culvert discharges into a well defined ditch, which flows to the west through the southerly portion of the property, and then continues through the site to a ravine on the south side of the property. At the time of our field visit on February 26, 1998, there was a steady flow of water in the ditch and culvert. The proposed onsite drainage design will include intercepting this basin's runoff as it enters the site, conveying it through the project, and discharging it directly into the ravine, bypassing the detention system. DOWNSTREAM: Runoff from the site sheet flows to the west where it enters one of two onsite ravines, continuing to the west. The ravines are approximately 600 feet apart and both dischazge into the wetland at the west property line. The flows eventually merge within the wetland and continue west for approximately 100 feet to Highway 167. Three culverts cross the Highway in the vicinity of the wetland; one 36" CMP culvert approximately 800 feet to the south, one 30" CNIP culvert approximately 400 feet north, and one 24"concrete near the site. While we have assumed that the northern culvert is the main discharge route, it is difficult to determine for sure due to the flat terrain. During our site visit in February of 1996, the 24" culvert was dry and appears to be at a slightly higher elevation, which tends to indicate that it may be a secondary discharge for the wetland. It is safe to say that during periods of high flows, the wetland will fill up and overflow into all three of these culverts. . � , , . . ;, i / 1 . I /,l / o . / � � . � I ' � j �� � � � ,� i ; � ; � � _ JC� r i I � x •x=—,;: � ��——�— � � I � � (� � 1 ' I '. / --�-�;° � ( / � 1 ; ' + 1 � � '� l�� �1�� � ; � 1;�i�� I I ' i / �,, , / ( � l � � � � , � � i ; I , � � ; / I , � ; �, T�E ! .� I � � �� �,___� � � � � � , � � I i l , ►;� , � � j ' _ �',, ' , —__ i `' � I ; � � ` � �• . i ' '� ' ' i f ' � � I I ' j� � : i � I I � .I j j ' , 1 ' ' �/ )' { __�__� x , � � � I � ' l� �I � �'! `' / { I , , I I , _ � � i + � i� ! { � _._— ..._��� �L— - ! ' 't � ' / J i • � � !�� , x I f i— — l� � � � � / � , � � � � � !�� ' .� f X"6I �f ( ( ` I i,'��•.�' ./ z i • I I � ' j r j � '! 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" � ` '�� T R IL� � ( , ` � �, ` �, �� � `, �, ��, � � ��t �� ' � _ � � � , ` � � � j h \ � ; I i j 1 � ' 1 !;�� �l i�1 �� r� ;'�(q�� ,' ' - --�` i �.l i \ \ \ � � `\ 1 L� �_i__—•_= 4� � � � ( � � � . ' '`�.,�`,1 � ��t�, '�� � �-`-+- I � � -RE� �/I ;'i' 1 ' t K � '� �\�,, � "�,..�,� � I �'�1 �, ' 1 . I , 1, � '� �` \_\ ` � � I � � � � ', 1 \ � � Y�,� � r � ` �� � � �,c�—— ---,— = 1=_,` � ! ', t \ \ � :',, \ ,, �, - `, . , , ;6 y-;__*-_ i �, ,� I� , :,, . . . - . ; . i \ i � I � `� � � ' ' ' ` , � � � j�� � � 1 � � �:i I � L 1 :� � 1 1 �,\ � I �1 c`+1� / 1 � 1 � � \�. � �� . I � � . ,. � ; . ; ; \ � i � I �, �`` I \ �`i ; 1 . � �' 1 ', ; ; . � � � � � 1 � �,�',� ,' ! ; � I . ', '� ; . TALBOT RO�D � i1 �I \ i t � '�' � � . 1 I f ; " � � '� �' ` �,; ` f UPSTREAM TRIBUT�RY AREAS f � i �'; ' ��t �t ; � • \ , � � I W � ��'` \� � ' `, � �< <. DEI PROJECT NO 94172 � � , � , . � ( � � � l � �.. , � i ► � I , .. � J II. OFF-SITE �.r�I,YSIS (cont.) The 30" CMP crosses SR167 to the west and enters a well defined channel, I approximately 8 feet wide and 8 feet deep. The channel flows west for 1100 feet to the East Valley highway, where a 6 foot X 4 foot concrete box culvert crosses to the west. The channel then turns to the north where it continues for over 1000 feet where it enters industria�developments. The system ultimately reaches the Green River The 36" CMP south of the site, crosses SR 167 and conrinues to the west along the north side of South SSth Street in a 6 foot X 6 foot channel. It flows for approximately 600 feet and crosses SSth to the south in a 36" concrete culvert. The channel flows south and west for 500 feet to a pair of 48" concrete culverts. These culverts discharge into a large stream, designated as Drainage District#1 on the Kroll Maps. It flows to the northwest for 800 feet to the East Valley highway, where a stream gauging station is located. The stream crosses under the highway through a bridge and continues west. The 24" concrete culvert crosses under SR 167 to the west into an industrial development. A discharge point was not located during field investigarions,but this area originally drained to a wetland with discharges both north and south, it appears, towards the drainage paths described above. The developed drainage system must also follow one or both of these routes. � � � ��� � � � � � �,:!!./ .� ( � i � i• :� ..._ �., ,. J • � . . f � i+; � :` ' . i � •"/ I ..,, ;�, f_/ r i,.; � ,'; -� ; � �, '/,�-�� i ;'r` ��1 ��: � � � .,;•� 1 . .;��� .::;�€� � � ' �; -�l .!i � ��G�( '"'' � I r� 1 `�/ /'� ,' �• . , � , �f, + / �:i �, � � �t /. � ', �Ir/ � i � I /• �/ I 1 1� � �� i,'� �' � ' J! I . �" i /r � . 1 i i / � � / �i i��� t I � +�' �1�,�`:/• ; 3 JI�. �-ccs ` ; , �` !f'�I�l ' - --._ . : � -�--�'' i � �� ` i` 1 (( r `'��/ l�•e / -� — - . _� � ' ��o I i.1 ' �1 i /�f � �� - / i ��� ' j�� iM _�L►�.Y=' _ ' ';. 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Proceeding to the west, the site is forested with second growth cover. Forested wetlands extend along the western property line. Precipitation Amounts: 6-month/24-hour= 1.28 inches 2-year/24-hour=2.00 inches 10-year/24-hour=2.95 inches 100-year/24-hour= 3.95 inches Existin� Onsite Basin Input: Hydrologic Soils Group= C Total Area=20.20 acres Impervious Area=0.10 acres @ CN=98 (roofs) Pervious Area=20.10 acres @ CNa�g= 83.01 (10.10 ac. pasture @ CN= 85, 10.00 ac. second growth forest @ CN = 81) Time of Concentration=43.98 minutes RESULTS (Peak Flow Rates): 2-year/24-hour= 1.46 cfs 10-year/24-hour=3.65 cfs 100-year/24-hour=6.32 cfs • ` � � • ' • ' �� d •Ja�• +� �i � . ��A��,Q,7�7������������ �, a �. � 'r/ _.�� �M �,��1���� �, .���� � '` -�.+- � , ��� . : �I� _�, ��./� _ � � �i,,�" � ,�� �, � ` ��- � «�ir �� �,��� . '`" �... •; ► �� o � -, . '-=�u�ia��.� e . . �.�. `, ,. �.w � . .�.:� _ � � � �EQ� ��1L�'�� �6 �� _w��l ���� ��.;_ ' • �i . 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AgC ���• ? - - ' --�.--��- --- _�--- ' ''�'��. ! � DEI PROJECT NO 94172 �_ r :;�: i - -- ' � . .• i i :� '� 1�,> r�. __ :,� ,_ , �'P,� , � ,�-�-`�_;���-_ ..(� -� ' � y---- � ';� . . .� o • �, r � � ��r '�'� - 1 � i _ _�.�11 1 11 \ u ..� �� p\ IIO _.��._L_ 3/4/99 8 :58 :47 am Dodds Engineers, Incorporated page 1 TALBOT ROAD DBI JOB NO 94172 --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: EX002 NAMB: EXISTING BASIN 2YR. BVENT SBUH MBTHODOLOGY TOTAL ARFA. . . . . . . : 20.2Q Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPBIA PBRV IMP PRECIPITATION. . . . : 2 .00 inches AREA. . : 20 .10 Acres 0 . 10 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 83 .01 98 .OQ TC. . . . . 43 . 98 min 43 . 98 min ABSTRACTION COBFF: 0 .20 PEAK RATE: I .46 cfs VOL: 1 .18 Ac-ft TIMS: 490 min BASIN ID: EXO10 NAMS: �XISTING BASIN lOYR EVSNT SBUH METHODOLOGY TOTAL ARFsA. . . . . . . : 20 .20 ACres BASSFLOWS : 0 .00 cfs RAINFALL TYPE. . . . : TYPElA PFRV IMP PRECIPITATION. . . . : 2 . 95 inches AREA. . : 20 . 10 Acres 0 . 10 Acres TIME INTPRVAL. . . . : 10 .00 min CN. . . . : 83 . 01 98 .00 TC. . . . : 43 . 98 min 43 . 98 min ABSTR..ACTION COSFF: 0.20 PEAK R.ATE: 3 .65 cfs VOL: 2 .38 Ac-ft TIME: 490 min BASIN ID: PX100 NAMB: $XISTING BASTN 100YR EVENT SBUH METHODOLOGY TOTAL AREA. . . . . . . : 20 .20 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYP$ . . . . : TYP$lA PERV IMP PRECIPITATION. . . . : 3 . 95 inches AREA. . : 20 . 10 Acres 0 . 10 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 83 .01 98 .00 TC. . . . : 43 . 98 min 43 .98 min ABSTRACTION COSFF: 0 .20 PEAK RATE: 6 . 32 cfs VOL: 3 . 79 Ac-ft TIM$: 490 min UPSTREAM OFF-SITE CONDITIONS: As described previously, there are three basin areas that drain from tributary upstream areas onto the proposed site. Two basins are the basins located on the west side of Talbot Road South and that are surrounded by, but not part of the proposed project. As described above these basins are l�own as the north property which is 1.69 acres and the south property which is 0.74 acres. These basins will be referred to in the calculations as "Offsite Basin X" and Offsite Basin W'consecutively. The third basin is the basin located east of Talbot Road South and contributes runoff to the roadside ditch on the east side of Talbot Road South. For calculation purposes, the third basin will be divided into two sub-basins. The first sub-basin will be refened to as "Offsite Basin Y". This sub-basin naturally drains into the 12" CPEP described previously. The second sub-basin will be referred to as "Offsite Basin Z". This sub- basin naturally drains into the 18" CPEP described previously. Initial storm runoff calculations for the two sub-basins will assume that drainage in the 12" CPEP is not restricted. Further calculations for conveyance of the by-pass system for drainage entering the 18" CPEP will take into consideration that drainage that backflows back into the ditch due to restriction of the catch basin located on the downstream end of the 12" CPEP. Detention calculations will take this into consideration. Offsite Basin W Input: Total Area=0.74 acres Impervious Area= 0.21 acres @ CN= 98 Pervious Area= 0.53 acres @ CN= 86 (grass) Time of Concentration=31.49 minutes RESULTS(Peak Flow Rates): 2-year/24-hour=0.12 cfs 10-year/24-hour=0.23 cfs 100-year/24-hour=0.34 cfs Offsite Basin X Input: Total Area= 1.69 acres Impervious Area=0.30 acres @ CNa„g= 98.33 (0.25 ac. impervious surfaces @ CN= 98, 0.05 ac. pond @ CN= 100) Pervious Area= 1.39 acres @ CN= 86 (grass) Time of Concentration= 35.48 minutes RESULTS(Peak Flow Rates): �'I 2-year/24-hour=0.24 cfs 10-year/24-hour=0.47 cfs 100-year/24-hour=0.72 cfs Offsite Basin Y Input: Tatal Area= 5.27 acres j 3/4/99 9 :29 :52 am Dodds Sngineers, Incorporated page 1 TALBOT ROAD DBI JOB NO 94172 BAS IN SiJNINIARY BASIN Ip: OW002 NAME : OFFSITE TRIB BASIN W 2YR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 .74 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPB. . . . : TYPSIA PERV IMP PRECIPITATION. . . . : 2 .00 inches AREA. . : 0 .53 Acres 0 .21 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86 .00 98 . Od TC. . . . : 31 .49 min 31.49 min ABSTR.ACTION COEFF: 0 .20 TcReach - Sheet L: 69 .OQ ns : 0 .0110 p2yr: 2 .00 s : 0 . 0556 ' TcReach - Sheet L: 216 . 00 ns: 0 .4000 p2yr: 2 . OQ s :0 .0685 impTcReach - Sheet L: 69 . 00 ns : 0 .0110 p2yr: 2 .00 s :0 . 0556 . impTcReach - Sheet L: 216 . 00 ns : 0 .4000 p2yr: 2 . 0� s :0 .�685 PEAK R.ATE: 0 .12 cfs VOL: 0 . 07 Ac-ft TIMF: 490 min BASIN ID: OWO10 NAME : OFFSITF Z'RIB BASIN W lOYR SBUH MSTHODOLOGY TOTAL AREA. . . . . . . : 0 .74 Acres BASEFLOWS : 0 .00 cfs RAINFALL 'I'YPL. . . . : TYPPIA P�RZI IMP PRECIPITATION. . . . : 2 .95 inches AREA. . : 0 .53 Acres 0 .21 Acres TIME INTFRVAL. . . . : 10 .00 min CN. . . . : 86 . OQ 98 . 00 TC. . . . . 31.49 min 31 .49 min ABSTRACTION CO£FF: 0 .20 TcReach - Sheet L: 69 .00 ns : 0 . 0110 p2yr: 2 .00 s :0 .0556 TcReach - Sheet L: 216 .00 ns: 0 .4000 p2yr: 2 .00 s :0 .0685 impTcReach - Sheet L: 69 .00 ns :0 . 0110 p2yr: 2 .00 s :0 . 0556 impTcReach - Sheet L: 216 . 00 ns : 0 .4000 p2yr: 2 . 00 s :0 .0685 PEAK R.ATE: 0 .23 cfs VOL: 0 .12 Ac-ft TIME: 490 min BASIN ID: OW100 NAMg: OFFSITE TRIB BASIN W 100YR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 .74 Acres BAS£FLOWS : 0 .00 cfs RAINFALL TYPF. . . . : TYP�lA PERV IMP PRECIPITATION. . . . : 3 .95 inches AREA. . : 0 .53 Acres 0 .21 Acres TIMF INTERVAL. . . . : 10 .00 min CN. . . . : 86 .00 98 . OQ TC. . . . . 31 .49 min 31 .49 min ABSTR.ACTION COBFF: 0 .20 TcReach - Sheet L: 69 .OQ ns : 0 . 0110 p2yr: 2 . 00 s :0 . 0556 TcReach - Sheet L: 216 .00 ns: 0 .4000 pZyr: 2 .00 s :Q .0685 impTcReach - Sheet L: 69 .00 ns: 0 . 0110 p2yr: 2 .00 s : 0 .0556 impTcReach - Sheet L: 216 . �� ns :0 .4000 p2yr: 2 . 00 s : 0 .0685 PEAK RATE: 0 .34 cfs VOL: 0 . 18 Ac-ft TIME: 490 min i 3/4/99 9:22 :34 am Dodds Engineers, Incorporated page � TALBOT ROAD DEI JOB NE? 94172 _____________________________________________________________________ BASIN SUMMARY BASIN ID: OX002 NAME: OFFSITE TRIB BASIN X 2YR SBUFi METHODOLOGY TOTAL ARSA. . . . . . . : 1 . 69 Aeres BASFsFLOWS: 0.00 efs RAINFALL TYPE. . . . : TYPElA P$RV IMP PRECIPITATION. . . . : 2 .00 inches AREA. . : 1.39 Acres 0 .30 Acres TIME INTERVAL. . . . : 14.00 miz� CN. . . . : 86.00 98 .33 TC. . . . : 35 .48 min 35 .48 �tin ABSTRACTION COBFF: 0 .20 TeReach - Sheet L: 280 .00 ns : 0.4000 p2�r: 2 . 00 s :0 .0804 impTcReaCh - Sheet L: 280 .00 ns :0.4000 p2yr: 2 .00 s :0 .4804 PEAK RATT: 4.24 Cfs VOL: Q . 14 AC-ft TIME: 490 min BASIN ID: OX010 NAME: OFFSITE TRIB BASIN X lOYR ! SBUH METHODOLOGY ', TOTAL AR�A. . . . . . . : 1 .69 Acres BASPFLAWS: 0.00 cfs RAZI�IFALL TYPE. . . . : TYPEIA PERV IMP PRSCIPITATION. . . . : 2 .95 inches AR.EA. . : 1.39 Acres 0 . 30 Acres , TIME INT$RVAL. . . . : 14.00 min CN. . . . : 86.Q0 98 .33 TC. . . . . 35.48 min 35 .48 min ABSTRACTION COSFF: 0 .20 TcReach - Sheet L: 280.00 ns : 0.4000 p2yr: 2 .00 s :0 . 08(34 impTcReach - Sheet L: 280 . 00 ns : 0 .4000 p2yr: 2 . 00 s :0 .0804 PEAK RATE: 0.47 cfs VOL: 0 .26 Ac-€t TIME: 490 min BASIN ID: OX100 NAME: OFFSITE TRIB BASIN X 100YR SBUH MBTHODOLOGY TOTAL ARSA. . . . . . . : 1 .69 Acres BAS�FLOWS: 0 .00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 3 .95 inches AR.EA. . : 1.39 Acres 0 .30 Acres TIMB INTERVAL. . . . : 10.00 min CN. . . . : 86 .00 98 .33 TC. . . . . 35.48 min 35 .48 min ABSTR.ACTION COEFF: 0 .20 TcReach - Sheet L: 280 .40 ns : 0.4000 p2yr: 2 .00 s : 0 . 0804 impTcReach - Sheet L: 280 .00 ns: 0 .4000 p2yr: 2 .00 s :�.a804 PBAK R.AT$: 0.72 Cfs VOL: 4 .38 AC-ft TIME: 49Q min ' II� j i Offsite Basin Y Input: Total Area= 5.27 acres '� Impervious Area=0.0 acres Pervious Area= 5.27 acres @ CNa�g = 84.17 (1.09 ac. second growth forest @ CN= 81, 4.18 ac. pasture @ CN= SS) Time of Concentration=45.76 minutes , Peak Flow Rates: (Note: These flows are unrestricted) 6-month/24-hour=0.11 cfs 2-year/24-hour= 0.43 cfs 10-year/24-hour= 1.01 cfs 100-year/24-hour= 1.72 cfs Flows Comin� On-site from Offsite Basin Y: � Flows from Offsite Basin Y first enter a ditch before entering the 12"pipe that crosses under Talbot Road S to the existing catch basin described previously. Upon entering the catch basin, flow is restricted by the 4"PVC exiting the structure. The head working on the 4"PVC is calculated by finding the depth of the ditch during the 6-month, 2-year, 10- year, and 100-year storms and then adding the difference in invert elevations from the inlet into the 12"pipe to the outlet into the existing catch basin. Calculation o�epth of Water in Ditch: The ditch has the following properties: Depth= 1.5 feet Side Slopes= 1:1 Bottom Width= 1 foot n =0.03 (earth bottom and rubble sides) Slope=0.9% The depth in the ditch is calculated using a Ditch Flow Analysis spreadsheet attached. Results of Flow Depth: Storm Flow De th 6-month 0.11' 2- ear 0.24' 10- ear 0.39' 100- ear 0.52' The HW elevation is therefore equal to Flow Depth+Elevation Difference in the 12" pipe. The12" CPEP has the following properties: Diameter= 12" 3/3/99 3 :29 : 7 pm Dodds Engineers, Incorporated page 1 TALBOT ROAD DEI JOB NO 94172 --------------------------------------------------------------------- --------------------------------------------------------------------- BAS IN SUNIl�IARY BASIN ID: OYOOfi NAME: OFFSITg TRIB BASIiV' Y 6M0 SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5 .27 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPg. . . . : TYPglA PERV IMP PRECIPITATION. . . . : 1 .28 inches AREA. . : 5 .27 Acres O . OQ Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 84 .17 0 . 00 TC. . . . . 45 .76 min 0 . 00 min ABSTRACTION COfiFF: 0 .2Q TcReach - Sheet L: 300 .00 ns : 0 .4000 p2yr: 2 . 00 s :0 .0833 TcReach - Shaliow L: 55 .00 ks :5 .00 s :0 .0909 TcReach - Shallow L: 360 .00 ks :5 .00 s : 0 . 3750 TcReach - Channei L: 610 .Ofl kc :5 .00 s : 0 .1066 PEAFt RATE : 0 .11 cfs VOL: O . I3 Ac-ft TIME: 550 min 3/3/99 2 : 54 : 53 pm Dodds Engineers, Incorporated page 2 TALBOT ROAD DEI JOB NO 94172 --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: OY002 NAME: OFFSITB TRIB BASIN Y 2YR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5 .27 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE . . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 5 . 27 Acres 0 . 00 Acres TIME INTERVAL. . . . : I0 . 00 min CN. . . . : 84 . 17 0 . 00 TC. . . . . 45 .76 min 0 . 00 min ABSTR.ACTION CO£FF: 0.20 TcReach - Sheet L: 300 .00 ns : 0 .4000 p2yr: 2 . 00 s :0 .0833 TcReach - Shallow L: 55 .00 ks : 5 . 00 s : 0 . 0909 TCReach - Shallow L: 360 .00 ks :5 . 00 s : 0 .3750 TCReach - Channel L: 610 .00 kc:5 .00 s : 0 . 1066 PFAK RATE: 0 .43 cfs VOL: 0 .33 Ac-ft TIME: 490 min BASIN ID: OY010 NAME: OFFSITB TRIB BASIN Y lOYR. SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5 .27 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPE . . . . : TYPElA P$RV IMP PRECIPITATION. . . . : 2 .95 inches AREA. . : 5 .27 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 84 . 17 0 .00 TC. . . . . 45 . 76 min 0 . 00 min ABSTR.ACTION CO$FF: 0 .20 TcReach - Sheet L: 300 .00 ns : 0 .4000 p2yr: 2 .00 s : 0 . 0833 TcReach - Shallow L: 55 .00 ks : 5 .00 s :0 . 0909 TcReach - Shallow L: 36Q .00 ks :5 .00 s :0 .3750 TcReach - Channel L: 610 .00 kc: 5 .00 s :0 . 1066 PEAR RATE: 1 .01 cfs VOL: 0 .65 Ac-ft TIME: 490 min BASIN ID: OY104 NAMB: OFFSITE TRIB BASIN Y 100YR SBUH METHODOLOGY TOTAL AREA. . . . . . . . 5 .27 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPglA PERV IMP PRECIPITATION. . . . : 3 .95 inches AREA. . : 5 .27 Acres O . QO Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 84 . 17 0 . 00 TC. . . . . 45 . 76 min 0 . 00 min ABSTRACTION COEFF: 0 .2Q TcReach - Sheet L: 300 .00 ns :0 .4000 p2yr: 2 . 00 s :0 . 0833 TcReach - Shallow L: 55 .00 ks :5 .00 s :0 .0909 TcReach - Shallow L: 360 .00 ks :5 .00 s:0 .3750 TcReach - Channel L: 610 .00 kc :5 .00 s :0 . 1066 PEAK RATE: 1.72 cfs VOL: 1 . 03 Ac-ft TIME: 490 min DIT�H FLC�� ��TA;L'��IS : : .. DITCH DATA: BOTTOM WIDTH (FT� = 1.00 JOB NAME: TALBOT ROAD LEFT SIDE SLOPE (L:1) 1.00 JOB #: 94172 RIGHT SIDE SLOPE (R:l 1.00 OPERATOR: G.R. BROOKS BOTTOM SLOPE (FT/FT 0.0090 DATE: 3/3/99 MANNING'S n = 0.030 FLOW FLOW WETTED HYDRAULIC DITCH FLOW DEPTH AREA PERIMETER RADIUS CAPACITY VELOCITY (FEET) (SQ F'T) {FEET) (FEE'I� (CFS) (FPS) 0.00 0.0000 0.0000 0.0000 0.000 0.000 0.05 0.0525 1.1414 0.0460 0.032 0.603 0.10 0.1100 1.2828 0.0857 0.101 0.914 _. . _ _... ... .. .. . _ _. __ _ _ _ ` �;:1� O:;I��1 i ���1 , :: o.o��i : 0:1 xs o sss; 0.15 0.1725 1.4243 0.1211 0.198 1.150 0.20 0.2400 1.5657 0.1533 0.323 1.346 _. ... , I; {1:24 q:2�76 ::::: :1.�i7$8 : '.. .. '�}:1:`7'��:'::::::.. �:�1 I:1_4$3.: :: _. . .. .. _. . . ... . 0.25 0.3125 1.7071 0.1831 0.473 1.515 0.30 0.3900 1.8485 0.2110 0.649 1.665 0.35 0.4725 1.9899 0.2374 0.851 1.802 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ '0�;39 {�:���1 �.�Q31: 0:��`�8:' 1:032 1:90�':: :; 0.40 0.5600 2.1314 0.2627 1.080 1.928 0.45 0.6525 2.2728 0.2871 1.334 2.045 0.50 0.7500 2.4142 0.3107 1.617 2.155 : _.. ....... . _ . t?:�2. 0:7904 ' �.4�fl8 ' �:::.:'::.:�}:�19�: �:. :: . . 1:737 ' 2.198. ...: _. _ _ .. . 0.55 0.8525 2.5556 0.3336 1.927 2.260 0.60 0.9600 2.6971 0.3559 2.266 2.360 0.65 1.0725 2.8385 0.3778 2.634 2.456 0.70 1.1900 2.9799 0.3993 3.032 2.548 0.75 1.3125 3.1213 0.4205 3.462 2.638 0.80 1.4400 3.2627 0.4413 3.923 2.724 0.90 1.7100 3.5456 0.4823 4.942 2.890 1.00 2.0000 3.8284 0.5224 6.096 3.048 3/3i99 DODDS ENGINEERS, INC. PAGE 1 5i0�J� - 4�.�)�-+ Length=35 re�l Manning's n= 0.�)1� The difference is elevation of the 12"pipe is the slope times the length ���hicli is (0.054)*(35) = 1.90 feet. Therefore the head working on the 4"PVC is: Storm Flow Depth Elevation Head on 4" Di erence PVC 6-month 0.11' 1.90' 2.01' 2- ear 0.24' 1.90' 2.14' ' 10- ear 0.39' 1.90' 2.29' � , _ �� _�,• , ,-�• -- Assuming the 4" PVC follows the slope of the existing ground and taking the dil: in elevation between the rim of the catch basin(EL. 155) and the water surface elevati� of the pond(EL. 140), the slope of the pipe was calculated to be 8.33% with a length of 180'. To detemune whether or not the inlet into the 12"pipe is submerged the following equation is used. If Q/(AD°�') >_4.0 then the pipe is submerged where A=(4/12)*�/4. Storm /AD°�5 Submer ed? 6-month 0.11 cfs 2.19 No 2- ear 0.43 cfs 8.57 Yes 10- ear 1.01 cfs > 8.57 Yes 100- ear 1.72 cfs > 8.57 Yes The maYimum flows through the 4"PVC are calculated using a submerged inlet conditions equation listed on page 4.3.5-2 in the King County Surface Water Management Manual. HW/D =c(Q/AD0�5)`+Y - O.SS (entrance property: square edge with headwall) Where: c =0.0398 Y= 0.67 HW=head working on the 4"PVC S = 8.33% The results are as follows Storm Q max Restricted Q leaving 4" through 4" PVC PVC 6-month N/A No 0.11 cfs 2- ear 0.61 cfs No 0.43 cfs max , 10- ear 0.63 cfs Yes 0.63 cfs 100- ear 0.65 cfs Yes 0.65 cfs Peak Flow Rates (Note: These flows are resultant flows leaving 4" PVC an�i entering site from Offsite Basin Y): 6-month/24-hour=0.11 cfs 2-year/24-hour=0.43 cfs 10-vear!�4-hour=0.63 cfs 100-� KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Methods of Analysts For Culverts The theoretical analysis of culvert flow can be extremely complex because of the wide range of possible flow conditions which can occur due to various combinat(ons of inlet and oudet submergence and flow regime within the culvert barrel. An exact analysis usuaily irndves deta�ed backwater calculations, energy and momentum balance, and application of the results of hydraulic model studies. Simpte procedures have been developed, however, wherein the va�ious flow conditions are classified and analyzed on the basis of a co�trol section. A contrd section is a location where the�e is a unique relationship between the flow rate and the upstream water surface elevation. Many different flow conditions exist over time, but at any given time the flow is either govemed by the culvert's inlet geometry (inlet control); or by a combination of inlet geometry, ba�rel characteristics, and tailwater elevation (outlet control). Figure 4.3.5B illustrates typical condftions of inlet and outlet contrd. The procedures presented here provide for the analys(s of both iniet and outlet contrd conditions to determine which is governing flow capacity and what that capacity is. In{et Co�trol Analysis Nomographs such as those provided in Figures 4.3.5C and 4.3.5D can be used to determine the iniet control headwater depth at design flow for various types of culverts and inlet configurations. These nomographs were originally developed by the Bureau of Public Roads - now the Federal Highway Administratlon (FHWA) - based on their studies of culvert hydraulics. These and other nomographs can be found in the FHWA publicatfon, Hydraulic Design of Highway Culverts, HD No.S (Report No.FHWA-IP-85- 15j, September 1985; or the WSDOT Hydraulic Manuai. Also availabte in the FHWA publication, are the design equations used to develop the inlet contral nomographs. These equations are presented below: For unsubmerged (nlet conditions defined by (]/AD°'S < 3.5; Form(1�� HW/D = H�/D + K(Gl/AD°�"" -0.5S�� Form(2)� HW/D = K(Q/AD°�"" For submerged inlet conditions defined by �/AD°'S > 4.0; HW/D = c(O/AD°'�z + Y -0.5S�� Where, HW = Headwater depth above inlet invert, ft. D = interior height of culvert barrel, ft. H� = Specific head at critical depth (d� + V�2/2g), ft. � = Flow, cfs. A = Full cross sectional area of cuivert barrel, sq ft. S = Culvert barrel slope, ft/ft. K,M,c,Y = Constants from Table 4.3.5A. d� = Critical depth (See Figure 4.3.5G), ft. V� = Flow velociry at critical depth, fps. g = Acceieration due to gravity, 32.2 ft/sec2. : The appropriate equation form for various in�et types is specified in Table 4.3.5A � Fo� mitered inlets use +0.7S instead of -0.5S 43.5-2 1/90 KINU COUN7' Y, W ASHiNG "I' ON, S I; KFACE W �1TER UESiUN NSANL' AL TABLE 4.3SA C�NSTANTS FOR INLF_T CONTROL EQUATIONS � 8� SIIAPE Uuc�prql7GED U0r(4f,ED DESJGN �� A�O MQqfAl10M f0U0.7101 �� lIO.' NAiEI11A� SCJLLE 1KlE� [DGE DES' .:d IORM ( 11 c � �t/ere�c� iIOU(� �a,sg � Cirwl�r ' / Sq�re edpr Whed��l 1 0.00'D6 I.0 O.OSVe 0.67 (561 (STl Co+cre[e 2 Croox erd�/Atd�all .007e 2.0 .D292 .Ti (56) (S7) 3 Grome e�d projectirq .00GS 2.0 .0117 .69 (56) (S�1 �'�'� � Cirtulsr 1 Ned+ll 1 .007D 2.0 .OITV .69 (561 (ST) CMV , 2 Nitlred te llope .0210 I.J3 .Otb] .�S (S� 3 ►�ojectinq .03t0 1.30 .055] .S� t5T) � Circul�r A �evtled r1rq, t5°bevet� t .001E 2.50 .OJ00 .7i fSJ) � eevelM ring, 33.7°berels• .0010 2.50 .02i3 .'f3 t57) _ � Rectenq�ler 1 )U° to 7S°vinq.��lt fl��es • ,076 1.0 .OSES .a1 f56) � �oR 2 90°rd IS°�irq�U ft�res i .061 0.T5 .6t00 .60 (56) � 7 0°virgudl fl�rts .061 0.75 .W.23 .DI fa) _ 0 Rectwngul�r 1 CS°rlaq.el! R�re d�.00m 2 .510 .667 .03(119 .EO fE) � �or 2 ib° te 33.7°virqr�lt tl�re d�.OG30 .tHb .bbf .02t9 .117 (C) _ �Q Recteryul�r 1 90°he�d�ll rA/�'chater; I .515 .661 .0)75 .70 fE) •o� 2 90°Mdwll Wt5°bevelf .195 .(dT .0)li .82 <D) 3 90°��dyll v/33.7°Eevel• .tbb .667 .0252 .E65 (E) - 11 Ilectwnqul�r 1 7/N chMfvr, <S°skeuM he�dwll 2 .522 .61.7 .6e02 .TS (S) �w 2 ]/�"cAr+fen; 30°�k��rd At�ll .533 _667 .Ot2S .105 (S) 3 )/a'chrders; 1S°�ke.Rd hewd�lt ,StS .667 .Ot505 .68 (S) < t5°Aevels; 10°•l5° skewad htd��ll .�76 .667 _0J2� .7S (Sl - 12 �ectuqol�r 1 GS°nomollset rinq.��U flores 2 .�07 .66► .DSIo .N1} (E) Yo� 2 18.L°nm•ofhet rinyv�U fl�res .l4] .66T _0361 .d06 (al ]/t� ch�lers 3 1�.L°ron•elf�et rinqrd 1 11��es .<7S .667 A3t6 .71 fd) 70��tewmd b�rnl � - 13 11eet�rgul�r 1 �S°Y{1p�I� }I�fH • O/Ii[L 2 .t97 .66T .0l02 .dSS l6) �ot 2 33.7°�Irqrdi Tlve� • olhet .�95 .A67 .0252 .hSf (D) lop�evel� 3 is.t°�irqysll /l�ref - orlfet .t9S .667 .D:Z: .6E7 (0) - 1619 C M toxes 1 90°hex4a{i 1 .0067 2.0 .O3TD .69 LS:) 2 lAict v�tt projettirp .01<5 1.75 .001V .b6 (SJ► 3 lhin w�11 projKt��q .OSLO 1.5 .0��6 .S7 fiT) ' See FHWA HDS No. 5 4.3.5-7 1/90 Offsite Basin Z Input: ' Total Area=31.52 acres Impervious Area=0.0 acres Pervious Area= 31.52 acres @ CNa,,g= 84.93 (0.56 ac. second growth forest @ CN= 81, 30.96 ac. pasture @ CN= 85) Time of Concentration=42.87 minutes RESULTS: Peak Flow Rates (Note: These flows due not account for additional flow coming from Offsite Basin Y due to 4"PVC restriction): 6-month/24-hour=0.80 cfs 2-year/24-hour=2.87 cfs 10-year/24-hour=6.57 cfs 100-year/24-hour= 10.95 cfs The peak flow rates coming onto the site will be the sum of the flows from Offsite Basin Z plus those flows that backed up into the ditch due to the 4"PVC restrictor in Offsite Subbasin Y. Storm Q from Offsite Q (Offsite Q through 4" Q going into Basin Z with Basin Y when PVC outflow.f-om no Additional unrestricted Offsite Basin Flow Z 6-month 0.80 cfs 0.11 cfs 0.11 cfs 0.80 cfs 2- ear 2.87 cfs 0.43 cfs 0.43 cfs 2.87 cfs max 10- ear 6.57 cfs 1.01 cfs 0.63 cfs 6.95 cfs 100- ear 10.95 cfs 1.72 cfs 0.65 cfs 12.02 cfs Peak Flow Rates (Note: These flows are resultant flows with the additional from Offsite Basin Y entering site from Offsite Basin Z): 6-month/24-hour=0.80 cfs 2-year/24-hour=2.87cfs 10-year/24-hour=6.95 cfs 100-year/24-hour= 12.02 cfs 3/4/99 1 :48 :10 pm Dodds Engineers, Tncorporated page Z TALB4T ROAD DEI JOB NO 94172 � -------------=------------------------------------------------------- I ------------- ----------- ----- BASIN SUMMARY � BASIN ID: OZ006 NAME: OFFSITE TRIB BASIN Z 6MQ SBUH MSTHODOLOGY TOTAL AREA. . . . . . . : 31.52 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 1 . 2$ inches AREA. . : 31 . 52 Acres 0 . 00 Acres TZME ZNTERVAL. . . . : 10 .00 min C13. . . . : 84 .93 0 . 00 TC. . . . . 42 .87 min 0 . 00 min A.BSTR.ACTION COEFR: 0 .20 TCReach - Sheet L: 300 .00 ns : 0 .4000 p2yr: 2 .00 s : 0 . 11&7 TcReach - Shallow L: 250 .00 ks: 5 . 00 s : 0 .4200 TcReach - Shallow L: 700 .00 ks : 5 . 00 s : 0 . 1286 TcReach - Channel L: 480 .00 kc :20 . 00 s : 0 .0208 PEAK RATE : 0 . 80 cfs VOL: 0 . 83 Ac-ft TIME: 540 min _ 3/3/99 2 :54 :53 pm Dodds Engineers, Incorporated page 3 TALBOT ROAD DgI JOB NO 94172 --------------------------------------------------------------------- --------------------------------------------------------------------- BAS IN SUNIIKARY BASIN ID: OZ002 NAME: OFFSITE TRIB BASIN Z 2YR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 31.52 Acres BASEFLOWS : 0 .00 cfs RAINFALL TYPL. . . . : TYPElA PERV IMP I PRECIPITATION. . . . : 2 .00 inches AREA. . : 31 .52 Acres O . OQ Acres TIME INT$RVAL. . . . : 10 .00 min CN. . . . : 84 .93 0 . �0 TC. . . . . 42 . 87 min 0 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 300 .00 ns : 0 .4000 p2yr: 2 .00 s : 0 .1167 TcReach - Shallow L: 250 .00 ks :5 . 00 s :0 .4200 TcReach - Shallow L: 700 .00 ks :5 . 00 s :0 .1286 TcReach - Channel L: 480 .00 kc:20 . 00 s : 0 . 0208 PEAK RATE: 2 .87 cfs V4L: 2 . 08 Ac-ft TIM$: 490 min BASIN ID: OZO10 NAME: OFFSIT$ TRIB BASIN Z lOYR SBUH M$THODOLOGY TOTAL AREA. . . . . . . : 31.52 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPS. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 .95 inches AREA. . : 31 .52 Acres 0 . 00 Acres TIME INT$RVAL. . . . : 10 .00 min CN. . . . : 84 . 93 0 . 00 TC. . . . . 42 . 87 min 0 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 300 .00 ns :0 .4000 p2yr: 2 .00 s : 0 . 1167 TcReach - Shallow L: 250 .00 ks :5 . 00 s :0 .4200 TcReach - Shaliow L: 700 .00 ks :5 . 00 s :0 . 1286 TcReach - Channel L: 480 .00 kc:20 .00 s : 0 . 0208 PRAK RATE: 6 .57 cfs VOL: 4 . 05 Ac-ft TIME: 490 min BASIN ID: OZ100 NAME: OFFSITF TRIB BASIN Z 100YR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 31..52 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYP$lA PERV IMF PRECIPITATION. . . . : 3 .95 inches AREA. . : 31 .52 Acres 0 . 00 Acres TIME INT$RVAL. . . . : 10 . 00 min CN. . . . : 84 . 93 0 . 00 TC. . . . . 42 . 87 min 0 . 00 min ABSTR.ACTION COEFF: 0 .20 TcReach - Sheet L: 300 .00 ns :0 .4000 p2yr: 2 . 00 s : 0 .1167 TcReach - Shallow L: 250 .00 ks :5 .00 s:0 .4200 TcReach - Shailow L: 700 .00 ks :5 .00 s:0 . 1286 TcReach - Channel L: 480 .00 kc :20 . 00 s :0 . 0208 PEAK RATE: 10 .95 cfs VOL: 6 .32 Ac-ft TIME: 490 min IV. DEVELOPED SITE CONDITIONS As described previously, all runoff from roof drains, streets, driveways and the majority of the yard areas will be intercepted by the proposed storm drainage system and conveyed to the detention pond. Additionally, the drainage from Offsite Basin X will flow through the detention pond. Developed Basin Input: Total Area=20.2 acres Impervious Area= 9.75 acres @ CN=98 (impervious surfaces) Pervious Area= 10.45 acres @ CN= 86 (grass) Time of Concentration= 21.48 minutes RESULTS: Peak Flow Rates: 2-year/24-hour=4.65 cfs 10-year/24-hour=7.93 cfs 100-year/24-hour= 11.54 cfs iI � i F � �_ . � N 88'36'S3• W � - � _- _ i� �a t `4 � ,/�',--=�;.. `�_--�1_�� � � , r - - - – � _ . . , . . _ - I - –- - � _�,�----, —� , � ���— � ��I�� --.�� ' �'; �� ,-� _,' µ �� � (/�5 ,-�= �K -, � s • _ -__� . - - �. � Ir,� -- ��r _r?-au.y � :�e-r'=x� L�t�: �"`s•�Ex ` _ �-� ���-�--- _.�--�---�--� : J' L47 L/� 1 �`• L7� ' ' 1 . i.^� - i . ! � \ _ \ I � � �'_��_S�O'� ID 7 I iN �F.�. 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YETLMO 1'�`. ��\$ �� �� .J /1 1 .� ,� 'T �y/� � '�,��\ _ L'STlFY I iI. ,.� I / : i I I � _'_�.�/ . I ` . IS!!f ' \\\\ f ... .� �. t 4 . . ___�_ ' � ,� \� �� ?� ���� 1�� / , \bm (�' � _ •` I � '•`�J � `� �� _ -I O I ' � \ ���•�� �_�-__'—r.T�- ��� '✓`/� \ �_ i � — � �� I �o _ _/ I.� Y�� - ' � f \\�\ \�\\ \ ? J ��/y \ ". I �.� a\„c° „ i $ , • s j '1 _ 1 —r�r—'�`_' �o,� c l \ \\ �`=...i" - . �Y � 1 8' + � - . r ` '� I �`. : ' ____ .\\� � s - -_ \ �_ Y_—��--�_ ! }`�..I � g i -� �=y �` i �r' �� _ _ �-g;_-� - -- ;�- �_I /�— — _ �i 5 ~ � d` -�� , �pa i I1 _ r- B.e, W 1��._` • .a _ _X I �,�r°'�' �.�n��.�,,s � � =��J� � , �._�-:f _ _ .~'� ��- ?� � - _ ,= � I T_4LBOT ROAD •. es aE.y.: _ � -�. ,1��I I• ' I ' '�3 ' � � �� �, r— — — _ _ ; DEVELOPED CONDITIONS �-_..0 saot_ {.� �� - . iC.]�es^ • -e 9_a_X t � � --�. ;;`� ��� i ::J� i .. __ , . ' I E�v•a�.i�w.; i� : � . \ , � � � 8•...s..- : � � : ' P�` �esF•- ` _�'- � � � r-8- _Ek ' ' ' I . � I � � _ ' P 1 • - ` � `�—//a�'�� i j�I�: —Tp---�_ _ �1--�_;_6��_ =r- --- i; I ; B�IN�P ��•:<ob• � ' ��,�__ ' - - — �_ __ _, /' '.T I ; DEI PROJECT NO 941`: w -� �:� \ � J i ia�s�a __ , „� ^w ,r� ' � , t 3/4/99 8 : 58 :55 am Dodds $ngineers, Incorporated page 1 TALBOT ROAD DSI JOB NO 94172 --------------------------------------------------------------------- --------------------------------------------------------------------- BAS IN SUNIlKARX BASIN ID: DE002 NAME: D£VELOPED BASIN 2YR FVENT SBIIH METHODOLOGY TOTAL AREA. . . . . . . : 20 .20 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYP£. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2. 00 inches AREA. . : 10 .45 Acres 9 . 75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 86 . 00 98 .00 TC. . . . . 21 .48 min 21 .48 min ABSTRACTION COEFF: 0 .20 PEAK RAT$: 4 .65 Cfs VOL: 2 . 18 Ac-ft TIME: 480 min BASIN ID: DFSO10 NAM£ : DEVELOPFD BASIN lOYR. EVENT SBUH METHODOLOGY TOTAL AREA. . . . . . . : 20 .20 Acres BASEFLOWS: 0. 00 cfs RAINFALL TYPE . . . . : TYP�lA PERV IMP PRECIPITATION. . . . : 2 .95 inches AREA. . : 10 .45 Acres 9 . 75 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86 . 04 98 .00 TC. . . . . 21 .48 min 21 .48 min ABSTRACTION COFFF: 0 .20 P$AK RATE: 7 .93 CfS VOL: 3 .62 AC-ft TIME: 480 m; r BASIN ID: DE100 NAME: DEVELOP£D BASIN 100YR EVEN'_ SBUH METHODOLOGY TOTAL AREA. . . . . . . : 20 .20 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 .95 inches AREA. . : 10 . 45 Acres 9 .75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 86 . 00 98 .00 TC. . . . . 21 .48 min 21.48 min ABSTRACTION COFFF: 0 .20 PEAK RATE: 11 .54 cfs VOL: 5 .20 Ac-ft TIME: 480 min IV. DEVELOPED SITE CONDITIONS (CONT.) The developed site will consist of a bypass system that will intercept flows from Offsite Basins Y and Z. In the existing condition, these offsite basins flow through the site and discharge into the ravines on the western portion of the site. The bypass system will maintain this existing drainage pattern. The other offsite basins either sheetflow onsite and will be included in detention calculations or sheetflow into wetlands which are drained into a bypass system. Offsite Basin Y is intercepted into a proposed tightline stormdrainage system. The flows are then directed to a flow splitter which directs the Offsite Basin Y 6-month storm to Wetland `H'. The remaining portion of the flows are bypassed. The flow splitter will be designed such that the Offsite Basin Y 2-year storm will be restricted to the 6-month storm going to the wetland. This will be done in an effort to provide a base flow to the wetland. The 10-year and 100-year storms will then be routed through the designed splitter and flows into the wetland will be calculated. The flows that enter Wetland `H' will be picked up by the storm system. Offsite Basin Z is intercepted into a proposed tightline stormdrainage system. T'he flows are then directed to a flow splitter which directs the Offsite Basin Z 6-month storm to Wetland `E'. The remaining portion of the flows are bypassed. The flow splitter will be designed such that the Offsite Basin Z 2-year storm will be restricted to the 6-month storm going to the wetland. This will be done in an effort to provide a base flow to the wetland. The 10-year and 100-year storms will then be routed through the designed splitter and flows into the wetland will be calculated. The flows that enter Wetland `E' will be picked up by the bypass storm system. These flows will not be included in the detention system calculations. Offsite Basin X, which is adjacent to the site, primarily sheet flows into Wetland `H' in the exiting condition and will continue to do so in the developed condition in an effort to maintain flow into Wetland `H' Offsite Basin W, vahich is adjacent to the site, primarily sheet flows into Wetland `E' in the exiting condition and will continue to do so in the developed condition in an effort to maintain flow into Wetland `E'. Flow Splitter Calculations: The flow splitter will be designed such that there will be 1-foot of head acting on an orifice during the 2-year storms for Offsite Basins Y and Z. The orifice equation used is: Q=CA(2gh)os Where:C =0.62 h= 1' A= �r� Offsite Basin Y"Splitter Desi� Q (6-month) =0.11 cfs � A=0.02 sf or r= 1", dia= 2" To find the elevation difference between the bypass invert and the invert of the outfall into the wetland, the depth of flow in the 12"pipe for the 2-year storm needs to be determined. The bypass pipe leaving the flo«� splitter has the following properties: Diameter= 12" Slope=0.055 The flow in the pipe when flowing fiill is calculated using I��tanning's Equation: QF= 1.49/n (AR2�3S';') QF = 9.08 cfs 'The amount of flo«- Qoing to the bti�pass systell� for the 2-year stoi-m �vill be the 2-year ,torm �o�tlin�, ii-on� the �" P�,��(' i�„ th� an���unt ���,in� to thc �.�°c�tlat�ci. (�:,,��,,�:.= ii.�; cl�_s �1 1 ] ci_� - i'�.�� cts The depth of flow is determined using a"Hydraulic elements graph ior circular se�vers'� attached. QBYPASS�QF=0.035 � d/D= 0.17 � d=0.17*1' = 0.17' The elevation difference between the bypass invert and the outflow invert to the wetland should be head acting on orifice less the depth of water in the bypass pipe. Elevation Difference= 1' -0.17' =0.83' The flow into the wetland for the 10-year and 100-year will be determined by fmding the depth of flow in the bypass pipe by assuming that the flow in the bypass pipe is the total • flow less the targeted 6-month flow. The orifice equation is then used to calculate the flow going to the wetland using the depth to calculate the head working on the orifice. If the flow to the wetland is different from the assumed outflow then the flow in the bypass pipe is recalculated and a new depth of flow is deternuned. The flow into the wetland is iteratively derived when the depth of flow is the same as the previously calculated depth of flow. 10-YEAR STORM: QB,r�Ass= 1.01 cfs—0.11 cfs=0.90 cfs The depth of flow is determined using a"Hydraulic elements graph for circular sewers" attached. QsYrnss�QF=0.10 � dlD = 0.25 � d=0.25*1' =0.25' H =elevation difference+depth of flow H=0.83' +0.25' = 1.08' Q = CA(2gh)0�5 = 0.62*�*(1/12)Z(2g*1.08}°�5 = 0.11 cfs OKAY 100-YEAR STOR1�1: QB�.�ss — 1.72 cfs— 0.11 cfs = 1.61 cfs The depth of flow is determined using a"Hydraulic elements graph for circular sewers" attached. QB�Ass�QF =0.18 � d/D =Q.25 �d=033*1' = 0.33' H = elevation difference+depth of flow H= 0.83' +0.33' = 1.16' Q = CA(2gh)0�5 = 0.62*�*(1/12)'`(2g*1.16)°�5 =0.12 cfs MORE THAN 0.11 cfs QB�nss— 1.72 cfs—0.12 cfs= 1.60 cfs QB�ra.ss�QF =0.18 OKAY (same as above) therefore QB,,�Ass= 1.60 cfs Offsite Basin Z Splittef•Desi�n: Q (6-month) = 0.80 cfs � A = 0.16 sf or r= 2.7", dia= �.4" To find the elevation difference between the bypass invert and the invert of the outfall into the wetland, the depth of the 2-year storm needs to be determined. The bypass pipe leaving the flo�v splitter has the following properties: Diameter= 1�'� Slop: :; _. ' The flow in the pipe _ , __ Q = 1.49/n(_"�'"�� F QF = 13.44cf The amount of flow going to the bypass system for the 2-year storm will be the 2-year storm less the amount going to the wetland. ' QB�Ass —2•8� cfs—0.80 cfs=2.07 cfs , The depth of flow is determined using a "Hydraulic elements graph for circular sewers" attached. QBYrAss�QF =0.15 � d/D =0.30 � d=0.30*1.25' = 038' The elevation difference between the bypass invert and the outflow invert to the wetland should be head acting on orifice less the depth of water in the bypass pipe. Elevation Difference= 1' —0.38' = 0.62' The flow into the wetland for the 10-year and 100-year will be determined by finding the depth of flow in the bypass pipe by assuming that the flow in the bypass pipe is the total flow less the targeted 6-month flow. The orifice equation is then used to calculate the flow going to the wetland using the depth to calculate the head working on the orifice. If the flow to the wetland is different from the assumed outflow then the flow in the bypass pipe is recalculated and a new depth of flow is determined. The flow into the wetland is iteratively derived when the depth of flow is the same as the previously calculated depth of flow. 10-YEAR STORM: Qa,�rAss = 6.95 cfs —0.80 cfs = 6.15 cfs Ill� �Z�71�1 t�j j�C?\� 11 u�.�CT'.l!'1C�1 11�111,� �i "H�:C�1'aliilC ��tRl�I1I� `'T"�lj�f: ii)� �'1TCll�.1T �t:\�LC� attacheci. Qsxr.4ss� QF =0.46 � d/D = 0.54 � d= . H=elevation difference+depth of flo�� H=0.62' + 0.68' = 1.30' Q =CA(2gh}o.s = 0.62*�t*(2.7/12)Z(�Q* QsYrnss=6.95 cfs-0.90 cfs=6.05 c Qs�nss�QF =0.45 � d/D =0.54 �Ji�.-'�i l�a�ii� u� aU���j 11tc�c1u1 c i1��,y��5 - u.v;' 100-YEAR STORM: QBYrnss= 12.02 cfs-0.80 cfs= 11.22 cfs The depth of flow is determined using a"Hydraulic elements graph for circular sewers" attached. QBYrAss�QF=0.83 � d/D =0.77 � d=0.77*1.25' = 0.96' H=elevation difference+ depth of flow H= 0.62' + 0.96' = 1.58' Q =CA(2gh)°�5 =0.62*n*(2.7/12)2(2g*1.58)0�5 = 0.99 cfs MORE THAN 0.80 cfs QB,,�A� = 12.02 cfs-0.99 cfs = 11.03 cfs QBYrnss� QF=0.82 � d/D = 0.77 OKAY (same as above) therefore QB,�Ass = 11.03 cfs FLOYV SPLITTER RESULTS: Total Flow Coming Flow Going To Flow Going Directly to Onsite Wetland B ass S stem Basin Y 2- ear 0.43 cfs 0.11 cfs 0.32 cfs Basin Y 10- ear 0.63 cfs 0.11 cfs 0.52 cfs Basin Y 100- ear 0.65 cfs 0.12 cfs 0.53 cfs Basin Z 2- ear 2.87 cfs 0.80 cfs 2.07 cfs ' Basin Z 10- ear 6.95 cfs 0.90 cfs 6.05 cfs Basin Z 100- ear 12.02 cfs 0.99 cfs 11.03 cfs 1\STRtiCTION OF SANITaRY, STOR�I SEWERS � HYDRAULICS OF SEWERS 87 t increase as the dia�meter of the pipe increases. This vsi��o� � md ° �unced, the smoother the pipe. Thus, from a hydraulic lo.o i.2 i.a i.e i.a z.o z.2 fz.a xe 2.s a.o 3.2 3.4 3.6 �ctice of using somewhat smaller values of n for large � . 1 pipe is generally not correct. (A similar deduction is 09 n,J variable with depth � �\ ' are related.) ----n,/�o�gta�� � � � �pose that tests of a 12-in. (30.5-cm) pipe, with �t D/!c � 0e ---IndependentofqJ � � � iea:e an n vn,lue of O.U10; tl�en, the vnlue fOP t1 6O-lIl. Darcy-Weisbach �� ~� Frittion}actor,f � vith tl�e same k value (Equatiou 2U) would be n= - o� ' � � If an n ��alue is cleveloped for large pipe, it may be b , �� ' � � same �-alue for �mall pipes, since they may be subject do.e � q Oischargs, � � H draulie ig inRuences. o Q / � y � /. radius,R �, y similar channels of non-circular cross section roughly =o.s 's � may- be reached if 4R is substituted for the pipe 4 Manning�:„ � 0 o.a � dox iii that, on the one hand, f will decrease with con- � � ,�� � ` ` vai��ti,v /� .' the otl�er hand n generally must increase. This results o.3 , �\ � the \Ianning coefficient, assumed as a constant, does , � � a���,a �� � �r all of the variables and conditions of flow. 0'2 � � � �' `. �duit and Eycraulic-Elemente Graphs o.l � � � ` re-conduit and open-chaiinel fiow the hydraulic radius o ' � '� x " 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 ous friction formulas with sati�factory accuracy even v A R Hydraulic elements g , and — tl�e experimental data� w�ere dc�•cloped from circular vf' Q�' A� R� For roughiiesses of the type often found in pipe work f FIGURE 24.-Hydraulic-elementa graph for circular sewere. by concrete surfaces), pipe resistance diagrnms of the re 211 ma,y be used for estimating f for open channels. • et al. (22). Graphs for sewers of other than circular cross section may �iousl�-, 4R should he used in pla,ce of D in computicig be developed by the same general method. ber and relative roughness. It should be realized th�t Most of the hydraulic-elements graphs in common use have been pre- conduit changes the friction�l resista�nce from that pared on the assumption that the �Ianning n does not change with the �' �Iooch- chart. Chow (2) has discussed the shape effect depth of flow for the particular conduit shape. Nonetheless, many ex- •ictiotl:il resistance. perimenters have observed a variation of n with depth of flow. The es- e cl�;i►incl shape on Manning's n have not been defined periments of Wilco.r• (23) and of Yarnell and Woodward (24) show that ape<ifiects f it must also affect n. G the value of n for a pipe flowing partly full is greater than for the full epth ot flow on f and n have not been defined com- pipe; and the average n values for 824 experiments are as indicated by the �ct effect of depth of flo��� or the height of veoetal cover M1 curve through the points marked b3� circles in Figure 24. A simila,r curve oefficient has been inve�tigated in grass-lined channels for the Darcy-Weisbach fraction factor f also ie shown in the same figure. �d al:o for natural channels anci fiood plains (2). A _ The relation bet«-een the two friction coe$�icients is n ��•ith depth of flow without an apparent change in ss lia� been observed in circulat• conduits and other i n (Rl� f 11�` . , . , ,21 ng partly full. This vari�tion is due to the effects of i nr—\R�/ f�/ which is similar to Equation 19. �� nent: graph may be used for the solution of problems I The points in Figure 24 marked by triangles and x's were estimated annel flow in closed conduits. It also is useful to � from the measuremente made by Johnson (25) in large Louisville, Ky., ts of �-ariation of n with depth of flow. Figure 24 is a ;� sewers flowing partly full. Since individual values of f/f� in the experi- � g� ' "or s of � 3r c; �ctic i un me� � Wi' �nd - --�rne l W ird i wi fron � � � � V. PROPOSED DETENTION DESIGN Si�PvIMARY The detention criteria used for this analysis is from the Department of Ecology's Stormwater Management Manual For The Puget Sound Basin. Since offsite tributary basins are involved in this analysis, the design release rates must be adjusted to allow the runoff from those flows from offsite basins that will not be bypassed to pass through the detention system without being detained. This simply involves adding the appropriate offsite flows to the existing basin release hydrographs. The required peak release rates are as follows: �Developed 2-year release � 50%Existing Onsite 2-year+Offsite Basin"X"2-year+Flow Diverted to Wetland `H' 2-year� 1.08 cfs •Developed 10-year release � Existing Onsite 10-year+ Offsite Basin"X" 10-year+Flow Diverted to Wetland `H' 10-year� 4.23 cfs •Developed 100-year release � Existing Onsite 100-year+Offsite Basin "X" 100-year+Flow Diverted to Wetland `H' 100-year�7.16 cfs The flows entering the detention system is: •Developed Onsite 2-year+ Offsite Basin"X"2-year+Flow Diverted to Wetland `H' 2-year� 4.99 cfs •Developed Onsite 10-year+ Offsite Basin"X" 10-year+Flow Diverted to Wetland `H' 10-year� 8.50 cfs •Developed Onsite 100-year+OffsiteBasin"X" 100-year+ Flow Diverted to Wetland `H' 100-year�12.36 cfs The detention input hydrographs are the result of combining the developed onsite hydrographs to the offsite hydro�aphs for each storm event. The detention vault is to be 200' long X 40' wide X 8.48' deep. SLTMMARY: Required Depth Design Peak Peak Storage Live Release Rate Input Rate Release Rate Volume Storage 2-year 1.08 cfs 4.99 cfs 1.08 cfs 43,834 5.48 ft 10-year 4.23 cfs 8.50 cfs 4.18 cfs 48,822 6.10 ft 100-year 7.16 cfs 12.36 cfs 7.15 cfs 59,861 7.48 ft , I 3/5/99 10 :39 :23 am Dodds Bngineers, Incorporated page 1 TALBOT ROAD D�I JOB NO 94172 STAGE STORAGE TABLE RECTANGULAR VAULT ID No. VAULT Description: DETENTION VAULT Length: 200 . 00 ft . Width: 4D . 00 ft . voids : 1 .Q00 STAGB <---STORAGB----> STAGB <----STORAGB----> STAGB <----ST4RAGB----> SPAGB <----STORAGB----> (ft} ---cf--- --Ac-Ft- ift) ---cf--- --Ac-Rt- (ft� ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- 50.00 O.00OQ Q.00OQ 53.60 28800 0.6b12 57.2Q 576�0 1.3223 60.80 8640Q 1.9835 50.1� 80�.OQ Q.0184 53.70 29500 0.6795 57.30 584�0 1.3407 60.90 87200 2.0018 50.20 16QQ 0.03b7 53.fl0 344U0 6.b979 5?,40 5920Q 1.3590 61.00 $8000 2.0202 50.30 2400 O.D551 53.90 31200 0.71b3 57,50 64000 1.3774 61.10 8880D 2.0386 50.40 3200 0.0735 54.00 32090 Q,7346 57.60 b080� 1.3958 61.20 89b00 2.0569 50.50 4600 0.0918 54.iU 32800 0.7530 57,76 b16Q0 1.4141 61.30 90400 2.0753 50.60 �800 0.1102 54,20 33600 O.T713 57,80 624�0 1.4325 61.40 91200 2.0937 50.70 5600 0.1286 54.3Q 34440 0,7897 57.40 63240 1.45�9 61.50 92Q60 2.1120 50.80 6400 0.1469 54,44 35200 0.8D81 5B4O0 b400Q i.4692 61.60 92800 2.1304 50.40 7240 �.1653 54.50 36040 0.8264 58,10 64866 1.4876 61.90 93640 2.1488 51.00 8000 0.1837 54,64 36800 O.B448 58.20 65600 1.50fi0 61.80 94400 2.1671 51.10 884D U.202Q 54.70 37600 D.8632 58.30 6540Q 1.5243 62.40 952D4 2.1855 51.20 9600 0.2204 54,80 38400 U,88i5 58.40 67ZU6 1.5429 b2.00 96000 2.2039 51.30 1D440 0.2388 54.94 39200 6.8994 58,50 68040 1.5611 52.10 96844 2,2222 51.40 ]1200 0.2571 55.00 44000 0.9183 58,fi0 fi6800 1,5794 62.20 97600 2.240b 51.50 12000 0.2755 55.10 4U800 4.9366 56,70 69604 1,5976 62.3Q 96440 2,2596 51.60 12840 0.2938 55.20 41b00 0.9550 58.80 70404 1,61b2 62.40 99200 2,2773 51.70 13604 0.3122 55.30 42404 D.9734 58.94 712Q6 1.6345 62.50 106004 2.2357 51.$0 14400 0.330b 55.40 43200 0.9917 59.OD 72040 1.6529 62,60 1008DQ 2.3140 51.90 15240 0.3489 55.50 44000 1.4101 59.10 728Q6 1,6713 62.7D 101600 2.3324 52.00 16040 0.3b73 55.60 44800 1.0285 59.20 73600 1.fi89b b2.64 1fl2400 2,3508 52.10 168UQ 0.3859 55.70 45b00 1.0468 59.30 ?4444 1,7080 62.94 1Q3200 2,3fi91 , 52.20 176D0 0.4040 55.80 �6400 1.0652 59,40 35200 1.T264 63.00 1D4000 2.38�5 I 52.30 18444 0.4224 55.9U 47206 1.0836 59.50 76000 1.7441 63,14 104BQ0 2.4059 52.40 i920fl D.4408 5b.Q0 48000 l.1d19 59.60 76800 1,?631 63.24 105600 2,4242 52.50 20400 0.4541 56.10 48800 1.1203 f4.70 77fi00 1.7815 63.34 106404 2.4926 52.60 20800 0.4775 56.20 4960� 1.i387 54.80 78400 1,?996 63.40 147200 2,4fi10 52.70 21640 0.4959 56.3U 5440U 1.1570 54.90 7g244 1.6182 63.54 1480Q0 2.4T93 52.80 2240fl fl.5142 5b.40 5i200 1.i754 bD.00 804Q0 1.83b5 63.bD 106800 2.9979 52.44 23200 0.5326 56.50 52000 1.1g38 bD.10 808Q4 1.8549 63.74 104fi00 2,5151 53.00 24000 0.55i0 5b.fi0 52800 1.2121 b0.20 81600 1,B?33 63.80 114400 2.5394 53.i0 24800 fl.5693 5b.90 53500 1.2305 b4.3� SZ404 1,8g1fi 63.90 111204 2.5528 53.20 25500 0.58�7 5d.80 54490 1.2489 fi6.40 83204 1.9100 b4.44 11260Q 2.5712 53.30 26460 0.6061 56.g0 55200 1.2672 64.50 84Q00 1,4284 64,04 112000 2,5712 53.40 2720Q 0.6244 57,00 5600Q 1,2856 fi0.6D 8460D i.946? 53,50 28U00 0.6428 57,14 56800 1.3439 6D.70 85b40 1,9651 � 3/5/99 10 : 39:23 am Dodds Engineers, Incorporated page 2 ' TALBOT ROAD DEI JOB NO 94172 STAGE DISCHARGE TABLE T MULTIPLB ORIFICB ID No. REST Description: RESTRIC�I'OR Outlet E1ev: 50 .fl0 Elev: 48 .00 ft Orifice Diameter: 4 .1250 in. Elev: 55 .60 ft Orifice 2 Diameter: 12 .5730 in. STAGB <--DISC�AflGS---> SPAGB <--DISCHARGB---> STAGB <--DISCHARGB---> STAGB <--DiSC9ARGB---> fft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- [ft► ---cfs-- -----.. 50.00 Q.0000 52.1Q 0.6691 54,20 0.9463 56.3Q 4.7481 50,10 Q.1466 52.20 U.6849 54.30 0.9575 56.40 5.0051 50.20 0.2065 52.3a Q.7403 54.40 0.46�6 56.50 5.2469 54.34 4.2529 52.40 4.Z153 54.54 0.9795 56.b0 5.4761 50,40 0,2924 52.5U 0.73Q1 54,60 0.9944 5fi.7� 5.6944 5Q.50 0.3265 52.60 4,7446 54.70 1.0411 56.80 5.9034 5Q,b0 0.357? 52.70 0.1587 54.8D i.0117 56.90 6.i041 � 50.76 0.3863 52,84 0.7Z27 54.90 1.0221 57.00 6.2495 50.80 0.4130 52.90 Q.7863 55.fl0 i.0325 57.1U 6.4843 50.90 4.4381 53,�0 0.7998 55.1� 1.U428 57.20 6.6653 51.00 0.46i8 53.10 4.$130 55,24 1.0530 57.30 6.8406 51.10 0.4843 53,20 0.8260 55.3Q 1.0630 57.44 7.0115 51.20 0.5058 53.30 0.8388 55.40 1.0730 57.50 1.I777 51.34 0,5265 53.40 0.85i4 55.50 1.0829 57.60 7.3397 � 51.44 0,5464 53.50 0.8639 55.60 1.0927 5?.7� 7.4979 51.50 D.5655 53,b4 0.8761 55.70 2.4590 57.80 7,6524 51,b0 0.5841 53.70 0.8882 55.80 3.0305 57,90 7,8037 52.74 4.6421 53.84 4.9001 55.94 3,4712 58,40 7,9518 51.80 0.6195 53,90 D.9119 5b.40 3.8442 52.90 6.b365 54,4U �.9235 56.10 4.1738 52.00 0.6530 54.10 0.9350 5b.20 4.4726 _ ►l�le., o�.,� ��I C�., �t�.� �JR- ��� �$� o� v r�! t.2 S - �- .�, �a..�Q -�,t.e..�-�',�cm .i h e. C�� C s� �'�- o Z. o r t�l c..�,S W�91�. �c� -�n-th�. a-rec,� c� -�.Q., a n c i nr c.��c.e_- , � d a -� �-d�� " ���Z �`� C , � �� �,00se.. 8'' �'o�r d., P�a � a a� � la����� da+ t�.--.� `y � ^ Qu ► U 3/5/99 10 :39 :25 am Dodds Engineers, Incorporated page 3 TALBOT ROAD DEI JOB NO 94172 ________________________________________�___________________________- LEVEL POOL TABLE SUMMARY MATCH iNFLOA -STO- -DIS- c-P6AY-� OUTFLOW STORAGB <--------D�SCRIP'PION---------� fcfs) (cfS� --id- �-id- <-STAGB> id (cfs} P01 (Cf1 ------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------- 2YR .......................... 1.98 4.99 VAULT R�ST 55.48 17 1,08 43834.21 cf 100YR ... ..................... 7,1b 12,36 YAULT RBST 57.48 18 7.15 59860.79 cf lOYR ..... .................... 4.23 8.50 VAOLT x$ST §6.10 ?9 9.i8 48822.42 Cf . .� •��� ���1�wA�11�M1� ���v������e0�� �� ���aM��NO�/h �OO ��NNt� :�• ���R�O�YY � • ��p/1���dq�� ��r��a�����sn ■■�a�����■�n���� -�• �■���ra��aun�� ���i�■n�iuu��un .. ���,��uuurDnu . , „ � ���►/����l1ue , . , : . ��r�//�� ■IIH .. ///i`/l���p8� ,/��' ���� �r ������ .. � ������ •� itg' ///!I/1LW�S��N��NNl�Bp ����/,�///B/�Nv�i��ptlp �I�IIiI'nr�=�q��duqt� :• �A/I /A���lqB��O/� s'�irrre�'i.c:��e�a d d�■��n u NN�N� R//1///B�l.����/lp��qN �������/�i/f%//J����I�t�st�t■t/■��! - ���I�����Y . �1���@�dd��uB ����q����//����vU��U - . ���0�� ./s�►�/�/�S�O�q��f���B �l�Yl�J/ ��O��i�W111 � . ��-.�,� �%��,�i,���inunii�i"n � ,� �. , � ��g��� ���.z�� r „ � r �� �������:�� s � � r•'� ` � :� �:i �i ' ��'�`�`�� � ��� �� i'l�. .���o.���..��od N�..... �MVM��af� ��r�����.�� .�: ��a��::: i�v��/,r�'�.i���'s�������ia.�iii�iu ����.t/����l����Nr�q�■�i�� ��'1.�������1�� ��a�o ����n � ���iu�nan ���i��.r%i���� i�nuunu �u��.,r��'�'������ nniiuu°au i � ��� ������ �� ������� � =� � � � .� . . . . . .. .: . . . . . . : . . . . �� � . . 11 � / The vault will discharge into a biofiltration swale for water quality treatment prior to discharge into the wetlands. The bioswale will be designed accarding to the King County Manual using a design water depth of 8 inches for wetland vegetation (see attached spreadsheet). � ,� I I Size Biofiltration Swale Note: All values in boxes are entered and this computer spreadsheet calculates the rest Flow(Q2)= 1.08 cfs slope (s)= 2.00% (bottom slope for for biofiltration design) depth(y)= 0.67 ft. (Table 4.6.4A) Mannings n 0.35 for biofiltration design Sides(z)= 3 (3 to 1 side slope preferred) Required bottom width(b)calculation Q=(1.49/n)x A x R^.66 x S^.5, (mannings equation) A= (b+zy)y (Fig. 4.3.7E common sections) R= A/(b+2y(1-z^2)^.� (Fig. 4.3.7E common sections) Q=(1.49/n)X ��b+zY)Y� '� �b+�')Y/b+2y(l+z^2)^.5]^.66 x S^.5) All variables in the above equation aze given except "b" "b" is solved for using a computer spreadsheet function to obtain a trail and error solution of b= 4.10 feet, for a desired length of 200 feet. check Q= 1.5399 cfs, OK same as given Find bottom width required if actual length is 180 ft. (Minimum length is �0 feet.) Find water surface area of 200 foot long biofiltration swale as required. Required water Surface area=(2zy+b) x 200 feet = 1623 SF Actual bottom width required=(Des. Surf. Area)/(length (actual)) - 2zy = 5.00 feet Find depth required for conveyance of 100-year storm peak flotii� after developement. Flow(Q100) 12.36 cfs slope(s) 2.00% (actual) bottom width �.00 ft. (actual as calculated) , Mannings n 0.027 (high "n" due to very shallow flow) ' Sides(z) 3 (3 to 1 side slope preferred) Flow Depth(y)calculation Q=(1.49/n)x A x R^.66 x S^.5 (mannnings equations) A= (b+zy)y (Fig. 4.3.7E common sections) R= A/(b+2y(l+z^2)^.5 (Fig. 4.3.7E common sections) Q=(1.49/n)x[{b+zy)y] x [b+zy)y/b+2y(l+z^2)^.5]^.66 x S^.5) All variables in the above equation are given except "y" "y" is solved for using a computer spreadsheet function to obtain a trail and enor solution of y= 0.289 feet, for a desired length of 200 feet. check Q= 5.2741 cfs, OK same as given Check velocity at 100-year flow rate,use y= 0.289 as calculated. V=Q/A =Q/b+2zY) =3.112 fps «< 5 fps limit OK The velocity of the 2-yr flow rate will be less than the ma�cimum 1.Sfps since the 100-yr flowrate is less than 5fF ��� �--1 � � '�_J VI. CONVEYANCE CALCULATIONS: The proposed conveyance system consists of a pipe/catch basin network that was designed in accordance with Chapter 4 of the 1990 King County Surface Water Design Manual using the Rational Method and assuming the following: The conveyance analysis uses the rational method for calculation of flows. A conveyance spreadsheet was produced for both the 25-year and 100-year storms. The attached spreadsheet shows that the system as designed has adequate capacity to convey the 100- year storm event. � � �-I . � i , ,�. i I � � � ':::����;J�.:[►;�:�ilp/#�:�":��(-}}.�?I;��i;:��:47,.#;�`'.�;:�}�j��l.�J:?I;:;:;:;:;:�: I.00ATInN: KING(:OUM'Y(14;N'fON) 34f1ARAINFAI.I.: 3A INCN6S JOB NAME: ASHBUtW CONDOMINIUMS JUB NUMBER: 94172 PNEPARk:D BY: 8Y"f DESIGN STORM: 25 YEAN � fiVckE.pi!t+?rni::;::'.iwewer�����'��traY+nl�r�' smws?e,., nnwrnci': twectekY.: �•n•4 ��. �: ruw -::::r�re�:'�:;:�ati,u;" �Thn�xi :FIPE�C'APACIT'YSt3MMAlhY;;; �rIrFFY,eMV�:�- ::�r��� :f7}�iof�(?�;NY ��,Uk,'F: .µlfi�ir� �(aJc: � �Mrh$ifY' f�oN � .N.��.�.r iniie�tw� �� I rt .�i.FhckK Y$ePf�YY ':iiMk �lll�u�Lt .v�r10.�1�.;4Nc.�rit(Ciil-01; �'. FIt�M::� It> � ;:�}t4]q). . `y..'. ..Ir:C)'. EA-�): (FI{HUfElp�'. (INIIWI.� I�f31 : lf\C�N1:9�-'IikW'LNI):'.1Y1'P7)..��F'f/6M'� '�(AIINI(r�G� . (ClLI::� .�IihYC):: ,(PCNClT1��:�: 29A 29 0100 Q64 0.12fl 0.128 6,W 2.tl2 0961 U01� 12 U.]UU 48 2.07 099 2.339 2.9tl 15.4% 29 26 0.060 0.64 OASI 0.179 6.39 2]I 0.486 0.014 12 9270 187 6.Q9 0.50 10.073 12.81 4.8% 28 37 0.580 0.64 O.J71 0.371 10.00 ].02 0.752 0.014 12 6.Ooa Iil 624 0.78 H.104 10.32 9J°/ 27 26 OA20 0.64 0269 0.640 IO.7tl 198 1.265 0.014 l2 3.62U 101 6.21 0.Y7 6.295 8.01 2U.1% 26 25 0.190 Q64 0.122 0.941 10.65 1.94 1.828 0.014 12 1.700 94 4]5 0.32 J.772 4.tl0 4tl5% 25 24 OJIO 0.64 U.U70 1.011 10.97 1.91 1.92tl OD14 12 3.650 106 7.W 0.25 6.321 8.05 30.5% 24 23 0.430 0.64 0.275 1286 11.22 1.88 2.417 0.014 l2 5.600 UI 8.67 027 7.829 9.97 309% 23 22 0.410 0.G4 U.262 1.549 1149 1.85 2.tl65 0014 12 9.600 IJS 11.08 U.20 10.J57 1319 17.7% 22 21 U1Y0 0.64 0.196 1.774 11.69 1.63 3.172 0.014 12 3.990 74 825 0.15 6.609 8.41 48.0°/ 71 40 O.OBO 064 0.051 IJ86 11.84 181 7.2J9 0.014 12 5.200 103 9.17 0.19 7.544 9.61 42.7/ I 20 B 0.540 0.60 0346 2.131 IlA3 1.eU 3.826 0.014 12 3.200 60 BA7 012 5.918 7.54 64J°/ 70 69 0.070 064 0.045 0.045 6.W 2B2 0.126 0.014 12 3.00U 2W 2.77 1.20 5.730 7.30 ]2% 69 68 O.IIU 0.64 0.083 0.128 7.2U 1.51 0.321 0.014 t2 40.670 31 8.19 0.05 21.098 26.86 1.3% 68 67 U.USU 0.64 0.038 0.166 71ti 250 0.415 0.014 l2 LWU BO 2.80 0.48 3J08 4.21 12.5% ti7 18 0,180 0.64 O.IlS 0.282 7.77 2J9 0.674 OA14 12 1.000 9U ).26 0.46 3.30B 4.21 20.4% 19 IB 0.350 U.64 0352 0.352 10.00 2.U2 0]ll 0.014 12 7.900 6U 6.69 0.15 9299 11.84 7]°r IB IS 0.250 0.6J 0.160 OJ94 10.15 2.U1 1591 0,014 l2 7.440 17ti 833 095 9.024 11./9 IZ4% 17 16 0.270 064 0.173 0.173 f0.00 2A2 0950 0.014 12 5.100 110 4.52 0,41 �.471 9.51 4.7/ I6 l5 0580 O.fi4 U.371 0.544 1041 1.77 1.077 0914 12 4.000 52 6.11 0.14 6.617 tl.42 Iti2i IS 14 0.160 0.64 O.102 I.44U 10.55 196 2.816 O.Ol4 l2 7AW 66 9.97 0.11 9.000 IL46 31.3% 14 l3 0.460 0.64 0.294 1.734 10.66 1 A4 3.169 0.014 l2 6J00 6A 10.14 0.11 8.563 10.90 39.3% 1) 10 0.610 0.64 0.390 2.125 10.77 i.93 4.US�Y 0014 12 6.400 76 10.55 0.12 8.169 1066 49.Wi 12 II 0.4)0 0.64 0,275 0.275 IO.W 2.02 0557 0.014 12 5.300 84 5.58 025 7.759 9.88 7.2% 11 10 0.350 0.64 U224 0.499 1015 1.99 0.993 0.014 12 6.000 SO 686 0.12 8.100 1092 12.i°ib 10 9 0.170 0.64 0.10'J 2.733 10.89 1.92 5.234 O.Ol4 l2 8.580 BS 12.59 0.11 9.691 12.34 54.0°/ 9 8 0.280 1160 0.179 2.912 11.00 1.90 5.540 0.014 12 4.400 I 11 9.81 0.19 6.9�U 8 84 79.6 B 7 0.190 0.64 0.122 5.165 12J6 1.78 9211 0014 IS 8.930 l20 14.61 0.14 17.925 14.61 51.4% 7 6 0.390 O.b4 0.230 5.414 1229 1.77 9586 0.014 IS IIJW tiU 16J8 0.06 20.518 16J2 467°/ 6 5 OJ90 0.64 0.122 5.576 1215 iJ6 9.770 0.014 l5 8.500 43 14.54 0.05 17.488 1425 55.9% 3 1 OI00 0.64 0.064 S.M1W 1240 �J6 9.857 0.014 IS 5.770 7P 12.68 0.10 14.409 IIJ4 68.4% 4 3 0330 0.64 0.211 5.811 1251 1J5 IU.174 0.014 IB 2.400 91 9J5 0.17 IS.111 8.55 67)'% 3 2 Q290 0.64 0.186 3.997 12.67 IJ4 10410 0.014 �8 2.000 2J 8.59 0.04 UJ94 7.81 75.5% 3/5/99 DODDS ENGINEERS,1NC. YAGF.1 , '��,������V�:Y��J.\�.L` ���7:#�lX�.���11'Vl� , : LOCATION: KINGCOUNTY(RENTON) 34HRMINNALL: 3.0 INCHES UB NAME: ASf19U1t1V COIVDOMINIUMS JOB NUMBER: 94171 PREPARlU BY: BPT UESIGN STORM: 35 YEAH 1`ICj(EM�NTAL:� �'�µLNU1P : �:�Ip1FF.il}'lPV9�::'; : '�r��OF�:' RP�WYkL4"�1'NWIilANY�.:,'''�:�:,:�:;' ;�PJI't.': .'�IIYp�:��.�YIPf �fP,Opl Tw��•si��'���YINE�r1TACt3'kS�IMMARY: :r1�C✓FMlm" :'AI� :�.'i Yh�ftyiF?+Y:.� . 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