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HomeMy WebLinkAbout03331 - Technical Information Report - Drainage � STORM DRA(NAG�F, R[:PCIRT c� �n� m ���������� �E�n�� p��-�� (� 3UGJ312 SO(��T�Y 15��r� STREET�� ; RE�TON, �����St1�NGTON ;' !�I I.1�. A'(l. �`1(1-I111-�I-(1�I 1'lil_1'_li:Ll) l�1 TOUNIA ENGINEERS 6G32 SOUT11 191ST PLACE, S1117'E E-102 kEN"I', WA 98032 (425) 251-OGGS Janu�ry 24, 200G _____.__ _- -- �;�`..•.;<<< �,� �==�-�_,=�� �_! ,�_�� ..�, ;. ,-��, =,�,; ��:.� - �' _;�� �,,,�'� - ' (�,' �" ' ; _ 1,;. ,_�� � }` � ir, '� u'�C}�� �1i t� ~ !l 4 ' i�� � y `J � �� ;;�,-, • �' L. ,-, , �' :� „� �,�:, -�.`' G�� +� ' , '' �t r ._,-.°� :'�.� � 1 �� 1��11 .,`,�tn,',���,�� � �� - _ -- � '��::ti l';._., ;J_,p�^_----- r�� �,� '� 3�31 G�� �� l - ' - `_ ,`J ��� .� ,� t P 1��� � � , TABLE OF CONTENTS L PROJECT OVERVIEW II. CONDITIONS & REQUIRMENT SUSNIMARY III. OFF-S[TE ANALYSIS IV. rLOW CONTROL AND WATER QUALITY V. CONVEYANCE SYSTEM ANALYSIS V1. SPECIAL REPORT AND STUDIES ' VI1. BASIN ANU OTt[ER COMI�7UNITY AREAS VIll. OTHER PERMITS IX. EROSION/5EDMINTA7'ION CONTROL DESIGN � X. I30ND QUANITIES WORKSI�EET , I � I. PROJECT OVERVIEW This project involves two single family parcels of approximately 1.27 acres. The project is situated in the south end of the City of Renton. It is located within no�theast quarter of Section 19, Township 23 North, Range 5 East W. M. The site is bounded on the north by Interstate 405, and on the south by S 15th street. It is bounded on the east and west by single-family lots. The proposal is to create 8 single-family lots, "Fill in" subdivision. Access to the proposed project will be from an existing street, South 15'h Street. A secondary access will be provided from the north via a private easement connecting the proposed subdivision to Shattuck Avenue South. The eight proposed lots will be served via 26- foot private access and utilities easement. Two parcels of land involved in this development. There exists a house on each of two parcels. The existing structures will remain, and will occupy the proposed Lots 1 and 8. The proposed private road is designed to follow the existing boundary line between the two parcels, and approximately mid-point between the two homes. The approximate distance between the two existing homes is 40 feet, plus or minus. The side setback for the existing two homes measures 7 feet, plus or minus, as compared to the required setback of 15.00 feet. Currently, the access to the existing homes is from South 15`n Street. The lot line proposed for lots 1 and 8 are set in accordance with minimum rear and front yard setbacks. The applicant submitted "Request for Modification" and received an approval from Public Works to allowing eight lots to be served by a private street, conc�itioned that i another access for the Fire Department is provided. The applicant secured necessary easement to provide a secondary access. The soils on the site are composed of Urban Land (Ur). The site is fairly flat at the southerly portion of the site, and steeper slopes ranges from 6 to 12 percent along the northerly portion of site. There is no indication of slope instability visible at the time of visiting the site. The surface water flow from the site is I oriented from south to north toward a perimeter road adjacent to I-405. The flow from i the site is oriented north across an existing single family lots situated north of the site. ; There exists storm system in the perimeter road (S 14"' Street) paralleling I-405. The flow is directed east toward Monroe Avenue South. Thence the flow is directed to the north into the I-405 storm system, . Pg. - 1 The proposed development of the property is considered as "infill" project and it is located in a Single Family (SF) zone. The City of Renton designates the site with the SF zoning. The SF zoning allows for a minimum lot size of 4500 square feet and a maximum density of 8 units per acre. The setbacks allowed in the SF zone are as follows: front yard setbacks, 20 feet; rear ya�d setbacks, 20 feet, and side yards setbacks, 5 feet on all interior lots, and 15 feet on corner lots. The City of Renton Comprehensive Plan designates the site as Single-Family Residence, which is consistent with present zoning. The density for the proposed three lots yield a density of 7.71 DU/ACRE which falls between the minimum of 5.0 and less than 8.0 required by Code. Majority of trees will be retained except for few trees which fall within the building envelope of the proposed new lots. � There will be no land to be dedicated to the City on this project. Pg. - 2 �I , ��. 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LAND SURVEYOR'S C£R1IFlCATE ��e�7 ror -�co�n rh�� �� �i_,=� � �`��: °� 7 , LAKEVIEW SHORT PLAT _ __ y �_ �t_ �his map ._orr?cUy � present � :ur�ev maae -ai +�sq�l�. _� �> >ook_�t �r oage__ ... �tir �eaues; °'' "`� -'� �naer ,ny directi� � �on�ormunca l�6� � i� � TOUMA ENGINEERS 306/312 S. 1�JTI-I STREET «rn �ne -evu rNments �f the �urvev Rec��aing .i RENTON, W/�1 �r �Aounlr � "���r^�7 ^c: ]t the reauest �i ��_ouis Maiesfs I1�\ ,��:i aF`7'/ALLEY FXECYJD4£PARK �,Ma jY Onrf �OB �O. in .;uiv "_005 ��n��s�'tiF.� 'j eQu soun�rsrn�ucE.�nr[c-ros•�c�+r. .0 xan _,nN � xT j. �oos ��o-��oa-,?5� ��, ,�aee�.nl ni-usss r�r�.nl n�-usas � '='�'AL VJv%� �HKD. 3r SCAt_E SHEe' ' M � �uDt. ot RecOrtls @�`����� � uHr YOiED 9 � l�@f�ifiCOfP, iVO. 34in ' �'F " iul. u� , ��,I �I � , p � rt I� � 'I ��._�Ile�_ �I' f i � . i , j�+4: . � C:i. I i�._ , : �ili��1' IV��i1W1� __ � �_� 1 � � F . - ! , � ����: ��� l� ��� ��� = ..� �� ���,,, �-t...,., _�!���," �=� - -�1�,, � . _ -�It � . .�s�„•:i�i „�. 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' � . l_ _._- ��j � � I— _ -- i `tCN, I i ■, ~ /• •• � f • ',� .A�C u� � i U� ' ' , Tu �/��; - InC I ! — q�e _�` � � � � °� 3a 'G,)'e�. � �A�n, � �'� .AmEi - --}- - --� - - --_ -' ______ _______ ----- � M� 17�' • �=i � : _ _ Py � Pu --- =-_-- --- I i •�1 ; � I � � Wo —, 0 � -��• � - - - ;� ;� � '. � Wo �' Q-1 ~:'-ti\� �M 194 i , !i�� ,' . �, j Illi � r �; ��� :C. ,,; �l. �II � .� 3 ., , ''�L— -� 'n . �g� "� �.�; ;�� �i � � •� Ur . -r�-"�. r/. �. --- ��OAmG IIr � II fl�� f�k � ���, i � � � --�i � t � _ . ��� _. /• ' r�Y. . � • • . . • .. � � 5 !� � �E � '/ � i' �I r ��"� � � ����v �� ��. ,•�� � 1 i. �''... i ... . �� 1•, , � , , , [I. PRELIMINARI�' CONDITIONS SUMMARY CORE REQUIREMENTS 1-5 CORE REQUIRLMEN'I' #l: D[SCf�ARGE AT NATURAL LOCATION The allowable outilows from the site will be discharged to its natural locations. The level l flow control is calculated to match the developed peak discharge rate to the e�cisting site condition peak discharge for the 2-year and l0-year. CORE REQUIREMENT #2: OFF-SITE ANALYSIS A level one downstream analysis is a portion of this report. See the analysis laterl in this report below. CORE REQUIREMENT #3: RUNOFF CONTROL The increased peak runof�', due to any change in pervious conditions and incl-ease of impervious areas, will be attenuated using peak rate runof�'control in accordance with KCSWM , 1990 Edition. Initial calculation indicates there is no detention facility required. Please refer to attached calculation. CORE REQU(REMCNT #4: CONVEYANCE SYSTEM Conveyance system is minimal for this proposed short plat. Storm runofl'from roofs and private �I driveways will be directed into storm treatment facilities prior to release runoff from the site CORE REQUIREMENT #5: EROSION/SEDIMENTATION CONTROL PLAN The erosion control plan will be designed using the King County storm manual. Silt fences will be used to intercept silt laden material resu(ting from clearing and/or constn�ction of short plat improvements. T'hese facilities will be adhered to minimize any impact to d�wnstream or ot�site areas. CORL; RLQU[REMCNT #6— MAINTENANCE AND OPERATION N/A CORE REQUIREMENT #7 — FINANCIAL QUARANTEES AND L[AI3ILITY N/A Pg. - 5 CORE REQU[REMENT #8 — WATER QUALITY The impervious surfaces subject to vehicular traf�ic within this proposed short plat is 12850 square feet, thus installation of water quality tank or pond or similar facilities will be included. This will be based on the 1990 KCSWDM, the vault volume wil) be the runof�'volume for the hydrograph for 1/3 of the 2 year precipitation. SPECIAL REQUIREMENTS: THOSE APPLICABLE TO PRO.IECT 1. Critical Drainage Area - N/A 2. Compliance with existing Master Drainage Plan - N/A 3. Conditions Requiring Master Drainage Plan - N/A 4. Adopted Basin or Community Plans - N/A 5. Special Water Quality Controls— N/A 6. Coalescing Plate Oil/Water Separators—N/A 7. Closed Depressions-N/A 8. Use of Lakes, Wetlands, or Depressions for Detention - N/A ' � 9. Delineation of 100 Year Flood Plain - N/A 10. Flood Protection for Type 1 and 2 Streams - N/A 11. Geotechnica( Analysis and Report - N/A i 12. Soils Analysis and Report - N/A � � Pg. - 6 III. OFF-SITE ANALYSIS CORE REQUIREMENT #2 LEVEL 1 ANALYSIS UPSTREAM This short plat does not have appreciable of�site surface runoff entering the site from upstream. Most of the runoff is intercepted by S. 15�' Street, adjacent on the south, at�d direct these to the west. DOWNSTREAM ` The runoff from the site is oriented from south to north toward existing single family lots, and a conveyance system in the frontage road along 1-40_S, S 14�` Street. Runof�flows are directed easterly to a culvert east of Morris Ave S. Per Renton's storm information a two 30" concrete pipes flow A sketch is included on the following paged showing the pipes and ditches observed along this downstream path. This sketch also indicates drainage areas that drain to the downstream stretches along S 14"' Street. Our short plat ties into an existing catch basin on the south side of S 14`�' Street. A 12" concrete pipe 152' long then drains easterly to a 2.5' deep ditch on the south side of S. 14`h Street. We have perCormed a pipe and ditch CIA calculation for a 25 year storm. These calculations indicate , that the ditches are more than adequate to carry runoff flows. P3 and P4 are just able the contain I the 25 year runof�' A 100 year storm will overtop the street at the culvert crossing at P3 and P4 and be guided into the ditches on the downhill side of the roads. The 30" concrete pipes under I- 405 are adequate for the upstream flows. Pg. - 7 H �� � >> S �� W�+�a+ �� tv rn�a , n � �` - , - , , , , , ; -- ; , ; � � , , , , , , ��, �, � - �� r� - , � � : �r �;� � � , �' i. ,___ ,_.._,.._ _... _.._. _ . , _.._..._ _.._..._ _.,_..._.,._..._ ._..._ _.._...� -- - ._._ _ �_� ___ �_ _ � --�-- __ __..._ � 'll I�' i �, �r���,-, > /'1'l<:, I � ; �,, , , � � o- _____ ; ; � ,� ; ,,, � `a l`1'l,' �� _� I�-L J'l�� 1 I j i � t ' II I� i i �:1 �. _ ._.._._ _ _._ _ _.__ � i , _ _ _ _ _ i � i (� � ___ _ _ _ ___.__._ _. _.._..._ ___..___s i i '� I I, i J- ��, ;I I'I�' j ! j ti� I i i i i j ! j � i t � � • ,� � i i i i � � i ,, � 1 � � � i . � i 1. '.)I���,� I )I I ' / �)'Y c,' �. ' .� j � i , ; i � i � �� I'[�, �� '111'I,' „ 'i��'I,� , � ! \ ��♦ ;� .,,i��,, • I i �1 I � j i i � i ,' � ' .� ; � ,,�,�i,' n I � �`� / i '� I I' I.' '� '!I I I ' I � `i ^ � � 7 j `� ; �� ,�,�' I�' 1 I ' i � � j ' i � i � ! � i � `! � 1 � j -'f�l �� � 1 ' 1 ( � � �i- -��.) ���� �. / \ _ ' �, ��I�' � � 1 `1 ( 1 � I � �.�� �<<l' � �i�� ��� , ` I I I' ` � l -". '_ ' '.._..._..._ ._.._..' _� ��_ � •� A � � • I � ��'� - -.._..-� - - -,._..._.._.._.. i � __._.._..._. _.._ _..._..._.._.._.._. � � ` � t,�)`l� '� ` I I I.' , � � � � � �,'I'l�' ���� � � ' ,c �,��`I, i '� � � � . i ' i i • \ ; . � I �� i ' ' �'`�Z _�t� � j/ y\ i ' � i � � _� ���;� � � ; , � ' ' � � ,C►a 2 =��� � � � , � �, T i i i � � � ..�, �ti•Z: f/ � � �, � i�i i � , 1 i M ' � � . _� � � 1�b= � � -�- -�a ,� y_ ' � Q$'b= � _ - � ���r"I �. I , I '� _ _ ._ -__ A 9'���� r�£ t a _ d��,?�.T i�� i)I ' I•I�� � _ _ � , J �JoFd E�5 �0 I� ♦ °'es'�v� ���'� d � � •_---T _ _ /B'�,Z� '~� Ze 2 CI t- _ _ _ 4+ �,�,, , - :��«•,?,-?,r £� t,�_� iii ' M a�o �� � Z� �;( �;�i'(; -,i , ,�:i , n a�pA rc _ _ _ _ - -� .---� S�Z \ �c_ _ " 7/28/06 Engenious Systems, Inc page 1 LAKEVIEW REACH SUMMARY 1 � ! ! I� � �•' , � ' Routing based on RENTON family @ 25 yr freq � `� ' � � I � DITCH REACH ID No. Dl Ditch Length: 210 . 00 ft Ditch Width: 1 . 00 ft Side Slopel : 1 . 00 Ditch Slope : 0 . 0300 ft/ft Side Slope2 : 1 . 00 Contrib Bas : Mannings n : 0 . 0500 Dn Invert . 0 . 00 ft Dn W.S . Elev: 0 . 0000 Num Steps : 10 Trib Area : _ � Ac . Design Flow : 2 . 87 cfs Depth . (0 . 65 ft Vel . 2 . 69 fps Upstream W. S . Elevc 0 . 00 ft . �_ l �� ���� DITCH REACH ID No. D2 Ditch Length: 200 . 00 ft Ditch Width: 1 . 00 ft Side Slopel : 1 . 00 Ditch Slope : 0 . 0500 ft/ft Side Slope2 : 1 . 00 Contrib Bas : Mannings n : 0 . 0500 Dn Invert . 0 . 00 ft Dn W. S . Elev: 0 . 0000 Num Steps : 10 Trib Area : Ac . Design Flow : 5 . 05 cfs Depth . f0 . 7�ft Vel . 3 . 77 fps Upstream w. S . Elev: j � o . 00 ft . __ � � ' ^;� DITCH REACH ID No. D3 Ditch Length: 200 . 00 ft Ditch Width: 1 . 00 fr Side Slopel : 2 . 00 Ditch Slope : 0 . 0500 f+ � � Side Slope2 : 2 . 00 Contrib Bas : Mannings n : 0 . 0500 Dn Invert . n nn � Dn W. S . Elev: 0 . 0000 Num Steps : 1�! Trib Area : - Ac . Design F1. Depth . i0 . 93�ft Vel . 4 . 29 £p, Upstream W. S . Elev: �� 0 . 00 ft . `,... / ' r4' DITCH REACH ID No. D4 Ditch Length: 50 . 00 ft Ditch Width: 1 . 00 ft Side Slopel : 3 . 00 Ditch Slope : 0 . 0300 ft/ft Side Slope2 : 3 . 00 Contrib Bas : Mannings n : 0 . 0500 Dn Invert . 0 . 00 ft Dn W. S . Elev: 0 . 0000 Num Steps : 10 Trib Area : !� Ac . Design Flow : 18 . 62 cfs Depth . �1 . 14) ft Vel . 3 . 72 fps Upstream W. S . Elev: � � 0 . 00 ft . _� � ' � '- � , � 1 ' t 7/28/06 Engenious Systems, Inc page 2 LAKEVIEW --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY PIPE REACH ID No. Pl From: To: Pipe Diameter: 1 . 00 ft n: 0 . 0120 Pipe Length . 152 . 00 ft s : 0 . 0290 Up invert . ft down invert : -4 . 41 ft Collection Area: 2 . 71 Ac . Design Flow . 2 . 92 cf s v�o�, Dsgn Depth : 0 . 47 f t Pipe Capacity . 6 . 59 cfs Design Vel . 8 . 14 fps Travel Time : 0 . 31 min Pipe Full Vel . 8 . 39 fps PIPE REACH ID No . P2 From: To: Pipe Diameter: 1 . 00 ft n: 0 . 0120 Pipe Length . 30 . 00 ft s : 0 . 0500 Up invert . ft down invert : - 1 . 50 ft Collection Area: 5 . 14 Ac . Design Flow . 5 . 06 cfs� ��� Dsgn Depth: 0 . 55 ft Pipe Capacity . 8 . 65 cfs Design Vel . 11 . 45 fps Travel Ti.me : n _ n-� nu n Pipe Full Vel . 11 . 02 fps PIPE RE�CH ID PJo . P3 From: To : Pipe Diameter: 1 . 00 ft n : 0 . 0120 Pipe Length . 30 . 00 ft s : 0 . 0900 Up invert . 3 . 00 f t do�vzl izi�.r�rt � �� . ',�i f 1 Collection Area: 14 . 87 <,�� Design Flow . 11 .45 cf s�. ��k: Dsgn Depth : 0 . 81 f t Pipe Capacity . 11 . 61 cfs Design Vel . 16 . 85 fps Travel Time : 0 . 03 mi Pipe Full Vel . 14 . 78 fps PIPE REACH ID No. P From: To: Pipe Diameter : 1 . 50 ft �i: 0 . 012!_. Pipe Length . 30 . 00 ft s : 0 . 0300 Up invert . 0 . 90 ft down invel_ Collection Area: 24 . 67 Ac . Design Flow . 18 . 64 cfs �pl� Dsgn Depth: 1 . 16 ft Pipe Capacity . 19 . 76 cfs Design Vel . 12 . 72 fps Travel Time : 0 . 04 min Pipe Full Vel . 11 . 18 fps ��{ -- iC7 V 7/28/06 Engenious Systems, Inc page 3 LAKEVIEW --------------------------------------------------------------------- --------------------------------------------------------------------- REACH SUMMARY PIPE REACH ID No. P5 From: To : Pipe Diameter: 2 . 50 ft n: 0 . 0120 Pipe Length . 82 . 00 ft s : 0 . 0100 Up invert . 0 . 82 ft do���ii iri���ert : -0 . 00 £L Collection Area: 24 . 67 Ac . Design Flow . 18 . 52 cfs v p�_ Dsgn Depth : 1 . 12 ft Pipe Capacity . 44 . 55 cfs Design Vel . 8 . 66 fps Travel Time : 0 . 16 min Pipe Full Vel . 9 . 08 fps ' J . IV. FLOW CONTROL AND WATER QUALITY The following calculations conclude that the 100-year peak flow diff'erence between the pre- developed ilow and post-developed flow is less than 0.5 cfs. ln accordance with 1990 King Count Surface Water Draina�e Manual detention is not required. The following calculations include: Basin areas "I'ime of Concentration Isopulvial graphs for 2, 10 and 100 year storms Pre-developed and Post-developed hydrographs The soil type found on this site is classified as Urban Land (Ur). The soil has been modified by addition of fill material several feet of depth to accom►nodate industrial and housing development. VI. WATER QUAL(TY There will be about 12850 square feet of new asphalt for private streets and driveways which are subject to vehicular traf�ic (PG[S). We anticipate construction of vault or under ground culvert tp treat the surface runof�'before releasing to its natural flow location. Per the attached developed condition information above, the increase in impervious surfacing is greater than 5000 square feet and is subject to water quality measures. Water quality is required and will be designed per t}ie 1990 KCSWDM. On page 1.3.5-1 the volume of a vau(t will be the runoff volume for the calculated runoff based on 1/3 of the 2 year precipitation. The attached hydrograph shows this volume is 1542 cubic feet. This can be stc�rcd in a 60" diameter cmp pipe. We have graphical(y depicted the volume availahl,� ir� tl��� E��4��� "i�l� the bottom 6" and top 0.95' eliminated. Sec the sketch on the fc�llc����in� ��a�t��; LENGTH OF PtPE REQUIRED f L = 1542/16.02 = 96.2_5' Use 97' of 60" dia. 12 ga. pipe with 2 - 2' lon� 3G" connectors tc� the 54" catch basins on each end The impervious surface is 36,700 square feet. The design water surface is to be 1% of tl�e contributing impervious surface per page 1.3.5-1 of the 1990 KCSWDM. The required surface area in the water quality vault should be 36,700 X 1% = 367 square feet. Per the attached sketcl�, 97 feet of 60" pipe with 0.95' of head room will provide 97' x 3.92' = 3R0 squar-e feet of surtace area OK. Pg. - 12 �—405 R w s�.�.*..nc�w.o�o — �,�.�.�� T _ 5 14TH STREE� ��,azo ` f T; , �U' � � � �'��� � — � �� i�s»sF �+�' � ' �j � � -- .��,;� r`_, �� 5 --_ -----_=---_.-- i- laaz IY \ ��j, r � � / r^ y'�' � I j � ��� ``7 �`� 6 1 �� � ,•' 4� I � I � �• 2 �?,'�L__---� �� � ` 1 ' �F~-- � � a nauE �1�� /' ; '� �.o� 2� I ; I a \ �� ��' � ; '��' �+�gob�°' � ; � � � I � � �% �; .��� �M ; �'""� ' ' � �\ � � I ;,, ;` � � ; , � �B `.1 I ; LOT S i i��Df HOUSE \�•� — — — — � — � �I I � \ LOT 4 � � � '; \ �r� � � � i i ti�^ ��' I / � ; , , r� '`.- '� � �°� +2'� � ' I 1 '/' I R£►��8�qg0"1 � I I ' i `�`PARCEL NQ� � , � �or e O 33�Qs0—f6o6 I � � ��wur,u� i I � � I i ;I I 12710i0 Si � � ; i —I i � — — — — " — — — I I � i � I . i � i I �� � i � i L0T 7 � �f"- �59�NG5�G_et)f.{�1 � � I� I N`� � �or z ' I � � c.o•��N•' I ;I a I � �� � ati� �Y � � I � t�osF � - - - - - - - - - - - - I �v W� � , � '� I �o I ; r-1 ~ �2 ; I � r',`"-a-� ��� 1s .5� � I Q � �� � � � � o S � �o Y�.�� i � j��oT a � � �- , ny,o�� � �R I (Z I VO J—.�J I ; Ex MQ15E ('�I i � � E%l1WSE �; � � ��3 I �i 1.108 SF J�; I ; °Y L439 SF �� ' I � I , ' 65 SF as.sr �r--� � `�=,=�� � . � PRED£V AC dc �g ! ��4 �' I ' ���', ��� OfV AC Qr 5/W I D/W= ?368 SF � ' � 4703 SF I 1� � f '� � i � CRASS = ?86B Sf i + ', , ' GRASS� SJ.I SF I - -�— ' - - - - - - - - - - - - -� � R/W ARE � � � ` , a ;� � = 5236SF . ' ,�ji �ra .ua - ----1- - - - �-- ------ -----�--------- ---' -- --------- W W � - - --- fX AC��236E SF ---- ----- ----- ;+���� _� SS 55 SS`��--i=i---SS SS �----R�- :� --MeosYre^w qS19 M =_---- -------------- ----°= .�_..,,� — MI��Yi �'� w=="�- AREA EXHIBIT � LAKEVIEW SHORT PLAT BASIN AREA ANALYSIS R/W AREA 0.12 ACRES ' PLAT AREA 1.27 ACRES � TOTAL AREA 1.39 ACRES SOIL TYPE BeD- Beausite Type "A" EXISTING CONDITIONS IMPERVIOUS HOUSE 8 SHED 3072 DRIVEWAY 1400 CONCRETE 1255 R/W AC & D/W 2368 TOTAL 8095 0.19 ACRES CN 98 PERVIOUS GRASS 49594 1.14 ACRES CN 86 R/W GRASS 2868 0.07 ACRES CN 86 1.20 ACRES CN 86 POST CONDITIONS-EAST SUB-BASIN IMPERVIOUS HOUSES& DRWYS 24000 ROAD 12700 R/W AC & D/W 4703 41403 0.95 ACRES CN 98 �, PERVIOUS LANDSCAPING 0.43 , R/W GRASS 533 0.012236 � 0.442236 ACRES CN 86 TIME OF CONCENTRATION -PRE DEVELOPMENT- FOR 10-YEAR, 24-HOUR STORM DESIGN EAST SUB-BASIN SHEET FLOW- OI MANNING-n 0.15 I OVERLAND-L 300 FEET PRECIPITATION-P 2.9 INCH SLOPE- S 0.09 FT/FT T1 = 13.58 MINUTES TIME OF CONCENTRATION -POST DEVELOPMENT-FOR 10-YEAR, 24-HOUR STORM DESIGN SINCE THERE WILL BE A SHORT SHEET FLOW RUNOFF ANTICIPATED THE TIME OF CONCENTRATION USED IS THE MINIMUM OF 6.3 MINUTES I 1y . , � _:�:�� -Isl.xl -- - . __----- _ - -1 nui��scs METHOD hoR conr�irtNc auNorr nvnnocRnrn I OItf1 OFi I ONS= - S_(:_S_ iYl'Ei 1R I�D " Y� ���� FLV�I - 7-iMY DF.SIGH SiURn - STOFW DAT11 FI I.F. pF�/ � �. ZD C FS iPFCIPY STORH OPTION: �✓� `� .6� G�S O _c_s_ ivrE -�n 1tAINI'RLL D1SiR1DUIION p y �FS .( D• ��F� tER= FRL•Q<Y[RR>. DURAiION(HOUR). PHECIPCIFK:HL•S) iee.z�.a.v D!G »+�-�»«���x+�+�-� S_(;.5. iYPF.-IA DISiRIFtUT10H �Mi�M��fwatMMxHMN�rw..,...„ +��►+t+F+a lifA-YF..fIR 7_4-IIOIIR SIORH ���+t 3_9fl" TOTAi, PRE(:IP_ *N���„K�N ENtER= A<PERV>, CN<PL'RV>. AC1tIPERV). CNCIflPERV>, iC POR I�RSIN N(►_ 1 .2,86._19,98,13_58 iM7(1 PR I Ni-(�IT: AREO<f1CRES) PERU[OUS IIiPERUlOI1S TC<11IMITIiS) i A CN A f,N 1 _1 1 _� R(._it _7_ 9R_R 1:1_f, ' PIiAK-4<CFS) 7-I'LRIiC111tS) UOL(CU PT) � .86 7.BJ iJ2B5 I F1lTF.R ld: ll�nf:hlFil�nanMl .extl POR STQRACF OP COt1PI1TF.D IIVDRUCRfIi'll- � �:x ( ILE ALRFADV FXIS7; WERNRITE <Y o� N> ? I PECIPY= C - CONIIMIE, H - NE�lSiOHti, T - PRIN1, S - SIOP i ----------------------------------------------------------- _ F]1TF.R: A<PEftV). (,'H(PF_RU>, A<I►IPF_RU>. (:N<IflPF.RU). TC FOR HASIN Nt�_ 'l .�4.A6._95.9R.f,_3 iA PR(HT-4UT: pR[Q<ACRES> !'TIiVIOUS InPGRV1011S iCCI'11MIIES> R CN R CN i _4 _4 R6.N _9 4R_R (�_:1 PEf1K-qCCNS) I-PF./IK<NR5> UOI.(CU-FT) 1 _7`1 'l_6'7 16561 : TER [d:l[pathlfilen��ne[_extl POR srorencr• or COF1PIIifD HYDROGRAPIIc [U '11.E AI.RERDV IiXISI; UUEIZWRI7E <Y or H) ? !i PECIFY: C — (:ONiIHOE, N - HE{JSiORn, P - PRINT. S - STOF' �� �� � �� _ _ ' � � ��r#i - �� , ,. NTER OPTION: BUH/SCS MEiHOD FOR COMPUTING RUNOFF HYDROGRAPH 70RM OPTIOHS: - S.C.S. TYPE-1A ��.;..V� � f�Pr �_� ; r, t = � r�, �-�, , < <-� � , ,-,, ; - 7-DAY DESIGN STOR11 - STOIq1 DATA FI LE � � . PECIFY STORM OPTION: .C.S. TYPE-1A RAINFALL DISTRIBUiION ER_ FREQCYEAR), DURATIONCHOUR>� PRECIP<INCHES) ,24,2 -------------------------------------------------------------------- S.C.S_ TYPE-1A DIS1'RIBUTION 2-YEAR 24-NOUR STORM �� 2.88" TO?AL PRECIP. �� -------------------------------------------------------------------- NTER: A<PERU), CN<PERU), A(InPERU). CN(IMPERU), 1'C FOR BASIN NO. 1 .43,86�.84,98,6.3 TA PRINT-OUT_ AREACACRES> PERUIOUS IMPERUIOUS TC<MINUTES) A CH A CN 1.3 .4 86.0 .8 98.0 6.3 PEAR-QCCFS) T-PEAHCNRS) UOLCCU-FT) ,�L -� p,c�g"G F`� _48 7_67 6735 t�ll'ER [d_ I[path)f ilenawe[.ext] FOR SIORAGE OF COMPUl'ED NYDROGRAPH: D2YR PECIFY: C - CONTINUE, N - NEwSTORM, P - PRINT, S - STOP � ' � � ---- ------------ � 1 � .=�� �`` �.1.J_J � ���. o x ii - RETURN I'0 DOS � TER OP?ION: ' BUH/SCS MEtHOD FOR COMPUTING RUNOFF HYDROGRAPH 'I ORM OPl'I ONS: - S.C.S. 1'YPE-1A - 7-DAY DESIGN STORM - STORn DATA FILE PECI PY StOR11 OP?I ON: .C.S. TYPE-1A RAINFALL DISIRIBUiION NTER: FREQ<YEAR), DURATIONCHOUR>� PRECIPCINCNES> �,24,2_9 -------------------------------------------------------------------- S.C_S. TYPE-1A DISTRIBUTION 10-YEAR 24-HOUR SI'ORM �� 2.98" TOTAL PRECIP. ���� TER: A(PERU>. CN(PERU), A(I1IPERU), CNCIMPERU), TC FOR BASIN NO. i .43,86, .84,98,6.3 ATA PRINT-OUT: AREA<ACRES) PERUIOUS IMPERVI4US TCCMIF#1TES> A CN A CN 1.3 .4 86.@ _8 98.0 6.3 PEAIi-Q<CFS> T-PEAK<HRS> UOL(CU-Ft> .77 7.67 18598 Nl'ER [d: ][pathlfilename[.extl FOR STORAGE OF COMPU?ED HYDROGRAPH: D18Y R PECIFY: C - CONTINUE, H - HEVSTORM, P - PRIHT, S - STOP � • I � 7 I , I �I'}?CTFY: C - CONTIN�JE, N - NEWSTORM, P - PRINT, S - S'I'OP l� IIYUROGRAPH DATA PRINT-OUT: '1'(HKS) Q (CFS) T(HRS} Q (CFS) T(HRS) Q (CFS) T (HRS) Q (CFS) . 00 . 00 6 . 33 . 23 12 . 67 . 18 19 . 00 . 11 . 17 . 00 6 . 50 . 23 12 . 83 . ]_6 19 . 17 . 1_1 . 33 . 00 6 . 67 . 27 13 . 00 . 16 19 . 33 . 1]_ . 50 . 00 6 . 83 . 32 13 . 17 . 16 19 _ 50 . 11 . 6? . Ol 7 . 00 . 33 13 . 33 . 16 19 . 6'1 . 11 . 83 . 02 7 . 17 . 39 13 . 50 . 16 19 . 83 . 11 1_ . 00 . 03 7 . 33 . 45 13 . 67 . 16 20 . 00 . 12 l_ . ].7 . 03 7 . 50 . 64 13 . 83 . 16 20 . 17 . 12 1 . 33 . 04 7 . 67 1 . 09 14 . 00 . 16 20 . 33 . 12 1 . 50 . 04 7 . 83 1 . 07 14 . 17 . 16 20 . 50 . 12 1 . 67 . 05 8 . 00 . 66 14 . 33 . 16 20 . 67 . 12 1 . 83 . 06 8 . 17 . 45 14 . 50 . 16 � ?_0 . 83 . 12 2 . 00 . 07 8 . 33 . 37 14 . 67 . 15 21 . 00 . 12 2 . 17 . 07 8 . 50 . 37 14 . 83 . 14 21 . 17 . 12. 2 . 33 . 07 8 . 67 . 31 15 . 00 . 14 21 . 33 . 12 7_ . 50 . 07 8 . 83 . 25 15 . 17 . 14 21 . 50 . 12 ?_ . 67 . 08 9 . 00 . 24 15 . 33 . 14 21 . 67 . 12 2 . 83 . 09 9 . 17 . 24 15 . 50 . 14 21 . 83 . 12 3 . 00 . 10 9 . 33 . 24 15 . 67 . 14 22 . 00 . 12 3 . 17 . 10 9 . 50 . 24 15 . 83 . ]_4 22 . 17 . 12 3 . 33 . 10 9 . 67 . 24 16 . 00 . 14 2?_ . 33 . 7.2 3 . 50 . 11 9 . 83 . 24 16 . 17 . 14 22 . 50 . 12 3 . 67 . 12 10 . 00 . 24 16 . 33 . 14 22 . 67 . 12 3 . 83 . 13 10 . 17 . 24 16 . 50 . 14 22 . 83 . 12 4 . 00 . 13 10 . 33 . 24 16 . 67 . 13 23 . 00 . 1.2 �} . 1_7 . 14 10 . 50 . 24 16 . 83 . 12 23 . 17 . 12 4 . 33 . 14 10 . 67 . 23 17 . 00 . ].:1 23 . 33 . 12 4 . 50 . 14 10 . 83 . 20 17 . 17 . 11 23 . 50 . 12 4 . 67 . 16 11 . 00 . 20 17 . 33 . 1]_ 23 . 67 . l?_ 4 . 83 . 17 11 . 17 . 20 17 . 50 . 11 23 . 83 . 12 5 . 00 . 18 11 . 33 . 20 17 . 67 . 11 24 . 00 . 06 5 . 17 . 18 11 . 50 . 20 17 . 83 . l]_ 24 . 17 . Ol 5 . 33 . 18 11 . 67 . 20 18 . 00 . 11. 24 . 33 . 00 5 . 50 . 18 11 . 83 . 20 18 . 17 . l]. 24 . 50 . 00 5 . 67 . 20 12 . 00 . 20 18 . 33 . 11_ 24 . 67 . 00 5 . 83 . 22 12 . 17 . 20 .18 . 50 . l.]_ 2.4 . II3 . 00 6 . 00 . 22 12 . 33 . 20 18 . 67 . 11 25 . 00 . 00 6 . 17 . 22 12 . 50 . 20 18 . 83 . 1_1 25 . 17 . 00 r � �g • � i -5a • : , ��� '�u�J BUH/SCS METHOD FOR COMPUTING RUNOFP NYDROGRAPH TORM OPTIONS: yc/AT E Q Q (,�, A � I I / VDL C� I"1 F�. — S.C.S. 'fYPE-1A �r - STORM DATAGFI LEORM I�, ��r Z ye 2�� : �� (,, � PECIFY STORM OPTION: .C.S. tYPE-1A RAINPALL DISTRIBUTION 'fER: FREQ<YEAR>, DURATIONCHOUR>, PRECIP(INCHES> ,24._67 - ----- ------------- S.C.S. TYPE-iA DISTRIBUT[ON 1-YEAR 24-HOUR STORM �� .67" TOtAL PRECIP_ -��� ----------------------------------------------------------------- NTER: A(PERU)� CNCPERU), ACIMPERU). CHCIIIPERU)� TC FOR �SIN HO. 1 .43,86,.84,98,6.3 TA PRINT-OUT: AREA<ACRES) PERUIOUS IMPERUIOUS TC(MIFNlTES> A CN A CH 1_3 .4 86.0 .8 98.8 6_3 �,7q� k� S�t� �� j'7 �.� ��"/ PEAK-QCCFS) T-PEAB(HRS) UOL<CU-FT> .11 7_83 1542 L2 VDL , NTER [d: ][pathlf ilename[.ext] FOR S70RAGE OF COMPUTED HYDROGRAPN: DiYR PECIFY: C - CONTINUE, N - NE�lSTORM� P - PRIHT� S - STOP � �9 - t:����, 1,� � 2. 60 SF D. 95 ', ���-�. ,,� ► ��.►,r. s, r ' - .3. 92 - _ _ , = n,,��,� , - ,�. 6. 02 SF- � , 3 DIA PIPE � ►� 5 �. 02SF 8�� , 1 s 60 " DlA CMP 'i � "=2 ' 20 V. CONVEYANCE SYSTEM ANALYSIS ' The proposed storm system consists of one 12-inch pipe (smooth inside wall pipe N-12) conveying runoff from the site. The 100-year developed runoff from the site calculated at 1.20 cfs. A 12-inch pipe at a slope of 1.0 percent slope, is capable to carry 4.15 cfs, more than the i.20 cfs anticipated in a 100-year flows during post development. See the following pipe flow calculation sheets. Pg. - 21 r i tmp#1.txt �Vf�¢1( (,'Z }'}-j Manni ng Pi pe Cal cul ator F(,� �„L FL D y-� Given Input Data: shape . . . . . . . . . . . . . . . . . . . . . . . . Circular solving for . . . . . . . . . . . . . . . . . . . . . Flowrate Diameter . . . . . . . . . . . . . . . . . . . . . . . . 12.0000 in Depth . . . . . . . . . . - • - - - • - - - . . . . . . . . 11.2000 in 4-- Slope . . . . . . . . . . . . . . . . . . . . . . . . 0.0100 ft/ft Manning's n . . . . . . . . . . . . . . . . . . . . . 0.0120 computed Resul ts: �D�� J� 2(� D IL Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 4.1512 cfs Area . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7854 ft2 Wetted�Area . . . . . . . . . . . . . . . . . . . . . 0.7629 ft2 wetted Perimeter . . . . . . . . . . . . . . . . 31.4313 in Perimeter . . . . . . . . . . . . . . . . . . . . . . . 37.6991 in velocity . . . . . . . . . . . . . . . . . . . . . 5.4413 fps Hydraulic Radius . . . . . . . . . . . . . . . . 3.4952 in Percent Full . . . . . . . . . . . . . . . . . . . . 93. 3333 % Full flow Flowrate . . . . . . . . . . . . . . 3.8597 cfs Full flow velocity . . . . . . . . . . . . . . 4.9143 fps r � Page Z Z tmp#l.txt Manni ng Pi pe cal cul ato r �l-OW D�P 1 N �'T Given Input Data: Q IvV shape . . . . . . . . . . . . . . . . . . . . . . . . Circular Solving for . . . . . . . . . . . . . . . . . . . . . Depth of Flow Diameter . . . . . . . . . . . . . . . . . . . . . . . . 12.0000 in Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 1.2000 cfs slope . . . . . . . . . . . . . . . . . . . . . . . . 0.0100 ft/ft Manning's n . . . . . . . . . . . . . . . . . . . . . 0.0120 Computed Results: Q 19 p [�epth . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5943 in .¢--- Area . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7854 ft2 wetted Area . . . . . . . . . . . . . . . . . . . . . 0.2766 ft� Wetted Perimeter . . . . . . . . . . . . . . . . 16.0117 in Perimeter . . . . . . . . . . . . . . . . . . . . . . . 37.6991 in velocity . . . . . . . . . . . . . . . . . . . . . 4.3378 fps Hydraulic Radius . . . . . . . . . . . . . . . . 2.4879 in ` Percent Full . . . . . . . . . . . . . . . . . . . . 38.2856 % Full flow Flowrate . . . . . . . . . . . . . . 3.8597 cfs Full flow velocity . . . . . . . . . . . . . . 4.9143 fps Page Z �j IX. EROSION/SED[NIENTATION CONTROL llESIGN The temporary erosion plan will be designed to the requirements of the 1990 King County Surface Water Design Manual. The silt fence and silt trap will be placed to help reduce the chances that any construction related silty runoff will leave the site and affect downstream property or facilities. The amount of cleared area for road and site construction will be the 2-year developed peak, which will produce a peak flow of about 0.48 cfs. From section _5.4.5.1 Erosion and Sediment Control Standards a sediment trap for less than 3 acres development should contain a minimum surface area at 2.5' depth to riprap weir overflow and 3.5' to top of berm will allow settling of the silt particles. The minimum surface area is to be based on the formula; SA = FS (Q2/Vs) where ES = Safety Factor= 2.0 Q2 = Peak 2-year developed flow (0.48 CFS) Vs = Particle settling velocity=0.00096 f/s SA = (2) (0.48)/ (0.00096) = 1000 SF. Required 3:1 side slopes 102 - 34 X 42 = 1428 SF TOP BERM 101 — 28'X36' = 1008 SF TOP WE1R OK ]00 —22'X30' = 660 SF 99 — ]6'X24' = 3 84 SF , 98 — l0'X18' = 180 SF , 97.5 — 7'X15' _ ]OS SF BOT SEDIMENT TRAP � Pg. - 24 . , .F:�l�. � . . i.JJ .�I S�..;i�� :NI'ER OPi I ON: � BUN/SCS MEiHOD POR COMPUTIHG RUNOPF HYDROGRAPN I TORM OP?IOHS- - S.C.S. ?YPE-1A ��Vr, L (?r�r, r� � �, t � ► r�, r=�� < <�� � r ,,, , - 7-DAY DESIGN Si0R11 - Sl'ORM DA?A PI LE � •j - PECIPY SiORM OPTIOH: .C.S. 'fYPE-1A RAINPALL DISTRIBUiION N?ER: FREQCYEAR>, DURATION(HOUR), PREC[P<IHCHES> ,24,2 ---------------------------------------------------------------- +� S_C.S_ 7YPE-1A DISIRIBU?IOH �-*����� Z-YEAR 24-HOUR S1'ORM �+�-+•-M 2_�9" TO?AL PRECIP. ��+�+F»� ----------------------------- ---------------------------------------- � 1'ER: A<PERU), CN(PERU), A(I1IPERU), CNC111PERU)� 7C FOR BASIN NO_ 1 _43,66,.84,98,6.3 AiA PRIHI'-OUT- AREA<ACRES> PERUIOUS IMPERUIOUS 7'CCMIHUI'ES> A CN A CH 1.3 .4 86.8 _B 98.0 6.3 PEAK-Q<CFS> i-PEIIK(HRS) UOLtCU-PT> ��Z -�_ U,��Q,"G F`; .48 7.67 6735 .NIER [d: l[path)f ilenawe[.ext 7 pOR SIORAGE OF C011PUTED NYDROGRAFII- D2YR PECIFY: C - CON?INUE, H - NEYSi'ORM, P - PRIN1', S - STOP � �� ' Z 5