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Home My WebLink AboutSWP272245(1) STORM DRAINAGE REPORT ~~ FOR BNRI8HT SHORT PLAT I N� RENTON, WASHIN8TON m� File No. SHPL-101-90 r FOR: DONALD E. ENRIGHT 2120 SW 338TH STREET FEDERAL WAY WA. 98023 PH. (206) 927-5914 U� � � °. // PREPARED BY m� TOUMA ENGINEERS H. 6632 SOUTH 191ST PLACE, cc) WA N� SUITE E-102 KENT, WA. 98032 (206) 251-0665 TABLE OF CONTENTS ' I . PROJECT OVERVIEW . . . . . . . . . . . . . 1-4 . ' II . PRELIMINARY CONDITIONS SUMMARY . . . . . . 1-4 . . Core and Special Requirements and responses TIR form III. OFF-SITE ANALYSIS . . . . . . . . . . . . . 1-3. . ' IV. RETENTION/DETENTION ANALYSIS AND DESIGN . 1-2 . . ' V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN . 1-7 . VI . SPECIAL REPORTS AND STUDIES . . . . . . 1 . . . ' Bio-filtration ' VII . BASIN AND COMMUNITY PLANNING AREAS . . . .N/A . VIII . OTHER PERMITS . . . . . . . . . . . . . .N/A. . ' IX. EROSION/SEDIMENTATION CONTROL DESIGN . . 1-4 . . . . . ' X. BOND QUANTITIES WORKSHEET . . . . . . . . . . ' XI . MAINTENANCE AND OPERATIONS MANUAL . . . . . . . . XII. APPENDIX ' STORM REPORT FOR RIDGEVIEW ESTATES . 1-4 D. PROJECT OVERVIEW This project involves a parcel of land about 1 . 15 acres in N� northeast Renton' The property is situated in the northwest quarter of Section 3, Township 23 North, Range 5 East , W. M. It is bounded on the south and east by Ridgeview Estates plat , a w� single family development . The proposed site is located at the northwest corner of Anacortes Ave. and NE 25th Street . The N� surrounding properties on the north and west are large single family parcels. The property is presently vacant with 5 single family lots proposed for this short plat . The existing 30-foot N� access right-of-way deeded to the City of Renton by Ridgeview Estates (Lauralwood) will be improved to provide access to the N� new lots. A dedication of future road right-of-way along the southerly 30 feet of the property to the City of Renton will be a portion of this short plat . The existing soils as depicted by the King County Soil Survey are Alderwood soil (AgC and AgD) . This soil type is characterized by m� moderately high runoff potential and a relatively slow infiltration rate. A YI ► A,; Ah - illtop II � . , .i...� BeD r it BM • I a �� BM 22 :4- _ 02 It .23 `,21 ; i ,�: I 5 `�;:k vq*1 Hills g � I 985 PG oo •*•iF i. Ur ArnC 22 ` ` AgC a ( 1 I I BeD I"• J I;c 1 _ Bh .� , AkF Low ABC ! I ' AkF C I AgD pp-BN g B AgC i B 2 3z 'AgC r — — I BeC — -- ----- ----- I -----t — -- < �� FQ h AgC' AgD I BeC 'Pin �: te Wpo /ur I N Hills BeC InA ��' .• AgC I '0' Ur ' • EvB tWr) BeD I Ahf •Kpp'/4 BeC ur i41 I Newca BM 93 • 2 AgD 3 a_ ' ' bM 996 8 AmC • I I EvC BeD •eC Bh ABC �' Bh• 1 j• �� AgC AgC K),C Y •EvC 9� / - P \ A B - - J ----O- I OvD 9 g • - ---- ISO• - -------\' - ------- --------- E BMA A gM ----- 1 AgD ' ' I I 690 692 I y� dO _ :� AgC BMA n �' AgC _ NO I ../ AgC No .L l 605 OvD I a• I - Sm J 9 I �• O �Q BeC �p •`:•r. ;. 1 AgC o .. AgD•• 1 1 AgD ; �r I •i; 34 i �3• LO AgD D AgC '•�, —i o� I. �•, 1 .l AkF I AkF AgC •• EVB !a. I AkF C T I OvD g I BeC EvC V • I PY.. c;r+AVEL AgC PIT a dkF C� 306 •I r I ••• 13M Ito rvl3 N BM111 ; m s •BM 0$ ••• o 11 l Bh• Sc EvC y` n Ev0 ABD �L :., •, AgC ' 452- - - AkF it r ° LAmC AgC FF • ' (` AgD EvC kF �� •I Ur 1 •� •� 1rf i ••Sm .. '•i �,'1 r:e ` ;•'e .� �. •i R ry u.• �` ,• RaC•. •� — FJ z Trailer ark i — EvC RdE 900 tT4 ' ell 11 - l: SCALE 1"=200' O �FI F I � ' 1 J r- -1 r-, .......... �_r r Ir Y� 1 L r L r T I I F---1 ........... T ' 1 7 I I J J :ii•:Si•r\ L J ..................... .................... r1 C -, ��i r--, r .,::::1 .- 1;- LJ J ! LLB r�a�,✓J I I L L I I- 1_ --� L_r �__J L ,1 _ r-1 r� L �l I I I 1 f I I I J ? '� LJ LJ SF 1 _ 1 v>/, 5th COURT ` Iff 1 f 1 1 t, Z �LL .-F r r �- , �--1 PARK `1 L I L I I I I J r--, I _� 1 i L.l♦, i t i NE 24th STREET v Z S F SF % %. PRELIMINARY CONDITIONS The proposal is consistant with present zoning and the N� comprehensive plan. Per the zoning one of the lots will require a variance because of the frontage width requirements. Fire and N� police resources are adequate for this proposed development . The utilities, storm, water , and sanitary sewer are existing and N� available to the site. The storm will be collected and tied into the existing outfall from Ridgeview Estates (Lauralwood) . The water supply and sanitary sewer will be extended to the end of w� the proposed new private street . Because of a cul de sac length of over 500' a covenant must be recorded with the short plat N� requiring all new homes to have a fire sprinkler system installed. The new private street will be 20' wide with an inverted crown. The storm water runoff will be collected at the N� north end and piped northward, then tied to an existing 12" dia. outfall . ADDRESS CORE REQUIREMENTS 1 THROUGH 5 From the King County Surface Water Design Manual (KCSWDM) w� 1 . DISCHARGE AT THE NATURAL LOCATION: The developed discharge from the proposed short plat will be located to the north N� and east of the private road improvements. This location will allow the construction of a catch basin and storm drain pipe that ties into the existing outfall from a detention N� system from Ridgeview Estates. This existing outfall is a 12" dia. drain, piped down slope at about 18. 06% for 2201f to a type I catch basin. This outfall empties onto 25 feet m� of rip rap leading to the centerline of a drainage ditch along SE 95th Way. See the "Offsite Analysis" for the check N� of this outfall system. 2. OFF-SITE ANALYSES: The off-site analyses is attached to this report and is contained in section III . Ii . - Pg. 1 3. RUNOFF CONTROL: The runoff control will be to KCSWDM standards. It is anticipated that the peak rate runoff control will not be required due to less than 5000 sq. ft . m� Of new impervious asphalt surfacing. A new catch basin and piping will be connected to the existing conveyance system N� outfall from Ridgeview Estates. The additional impervious roof top areas will be directed to indivdual lot infiltration systems. 4. CONVEYANCE SYSTEM: The storm drainage conveyance system will be composed of underground pipes and catch basins. This =� system will be designed using the rational method to the KCSWDM standards. The pipes will be designed for the 25 N� year storm and checked with the 100 year storm for overflows and required freeboard. N� 5. EROSION/SEDIMENTATION CONTROL PLAN: The erosion control plan will be designed to the KCSWDM. The minimum requirements N� will include but not be limited to the following; rock construction entrance' filter fence, sediment trap and hydroseeding of the exposed areas. Page 1 of 2 ' King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PROJECTPART I PROJECT OWNER AND PART 2 PROJECT LOCATION r DESCRIPTION ProjectOwner 001,11+�D_ IT Project Name Address 2-12-o W,___ 3 8+'�_F, U/. lvp. Location Phone __Zo1,- 927.- 5�._____ _. ____ Township Project Engineer ram"^ Range Section Company 1 U� _�n r;---FNL�'NrEjQs - -- ProtectSize __. _,/�___--_— ACC Address Phone _Z_5_L._-_ _ s__-_ Upstream Drainage Basin Size —_--___ AC PART 3 TYPE OF • OTHER ' Subdivision El DOF/G HPA Shoreline Management Short Subdivision C] COE 404 Rockery Grading 0 DOE Dam Safety C] Structural Vaults ' Commercial O FEMA Floodplain EJ Other Other _____._________ _ [] COE Wetlands HPA COMMUNITYPART 5 SITE r DRAINAGE ' Community Drainage Basin PART 6 SITE CHARACTERISTICS [_] River -__._ __ _ ___--.._--_ Lj Floodplain - 0 Stream - - - _ ----- [--] Wetlands - - ----- --- --- 0 Critical Stream Reach F ] Seeps/Springs Depressions/Swales F-] High Groundwater Table L Lake --- - -__--- [._ j Groundwater Recharge ' LD Steep Slopes - 1 1 Other I_j Lakeside/Erosion Hazard PART 7 SOILS Soil Type Slopes Erosion Potential Erosive Velocities [_I Additional Sheets Attatched 1/90 ' Page 2 of 2 King County Building and Land Development Division ' TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 .DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT [� Ch.4Downstr-eam Analysis_ FA L ---- - - ---- - - -- - - ' _[]—Additional Sheets Attatched — REQUIREMENTSPART 9 ESC ' MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION [ ] Sedimentation Facilities Stabilize Exposed Surface ' Stabilized Construction Entrance Remove and Restore Temporary ESC Facilities Perimeter Runoff Control ® Clean and Remove All Silt and Debris Clearing and Grading Restrictions ) Ensure Operation of Permanent Facilities ' [TX1 Cover Practices Flag Limits of NGPES E71 Construction Sequence Other 0 Other PART i SURFACE WATER SYSTEM ' C] Grass Lined Channel E�J- Tank ED Infiltration Method of Analysis [� Pipe System J Vault Depression _ Open Channel [:::-] Energy Dissapator Flow Dispersal Compensation/Mitigation E] Dry Pond El Wetland Cl Waiver of Eliminated Site Storage t El Wet Pond F-- I Stream C] Regional Detention ----------------------- - ---- -— Brief Description of System Operation -PLG]e-_ to P_S u!ef A I t7F F— LorLl /Pe Facility Related Site Limitations N DCTr,l /T/oN, L So00 9i F A C. 0 Additional Sheets Attatched Reference Facility Limitation PART12 EASEMENTS/TRACTS PART 111 STRUCTURAL ANALYSIS (May require special sttUctUral review) L>�j Drainage Easement ' J Cast in Place Vault I -] Other -] Access Easement FI Retaining Wall L_J Native Growth Protection Easement EJ Rockery>4'High �] Tract ' F-::] Structural on Steep Slope [—] Other PART 14 SIGNATURE OP PROFESSIONAL ' I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attatchments. To the best of my knowledge the information provided here is accurate. sry»ev,re II la� 1/9f1 IXI~ OFF-SITE ANALYSIS A field inspection of the site was performed on October 10, of U� 1995. The property slopes down to the north at about 2-3% to the top of a bank that slopes down sharply to SE 95th Way. These steeper slopes range up to about 27%. The site is covered with native brush and some scattered mature trees. The trees are more dense on the steeper slopes and consist primarily of alder and fir . UPSTREAM ANALYSIS N� There are no upstream drainage flows that enter this site. The — plat and storm drainage system of Ridgeview Estates (Lauralwood) intercepts any flows from the south. The storm drainage system N� from this plat was constructed in 1988 and appears to be in good working order . There did not appear to be any evidence of overtopping, washing or flooding of it ' s conveyance or outflow m� system. DOWNSTREAM ANALYSIS Surface runoff from the proposed short plat will sheet flow northerly to the top of the steeper slope. The runoff will travel in the brushy swales to SE 95th Way about 250' north of the site. At this point any acumulated runoff will follow the N� existing roadside ditch as it flows northwesterly to a low area cross then a cross culvert under SE 95th Way roadway and to May Creek. The collected runoff for the proposed short plat will be emptied N� into the existing 12" outfall from Ridgeview Estates (Lauralwood) . This outfall begins at the detention tank and drains toward Duvall Ave NE about 220' north. The outfall N� terminates in a type I catch basin that bubbles up through the grate as an energy dissipator . From the dissipator the runoff flows over riprap to the westerly roadside ditch of Duvall Ave NE III. - Pg. I (Coal Creek Pkwy) . The runoff flows about 30' north to an 18" concrete culvert under SE 95th Way. A roadside ditch carries the storm water north about 700' to May Creek. This swale starts as a graveled roadside ditch for about 501 . Then the broad ditch becomes heavily vegetated for the remaining 650' leading to May Creek. There did not appear to be any undercutting, washing, or evidence of flooding along the route leading from the existing detention tank for Ridgeview Estates (Lauralwood) . We do not anticipate having any more than the standard restrictions placed on this m� proposed short plat . N� SUMMARY It was noted during the site visit that the existing outfall , ditch, and swale systems were not experiencing any undercutting N� or uncontroled washing. It appears that a slight increase in runoff could be tolerated by the existing downstream system. N� There did not appear to be any reason to overly restrict or ~- control runoff outflows. E E K P A COUNT a REI;CRE,A T I ON 0 E P I 60 --—---- S. L) T EC A#Ay>_ G V A if 86 1!11 53 A c \"\061Ac 0464C I'*-- 050Ac Qlo� 06 W 0 5P Ac I, 0 5?Ac D19 cl: I, 05?Ac C) W H Marshall, Jr. "?Do, loe Pignalard rr-c� 19 13 -4 Ac �z James Dalpay 0 Kenneth Mar5hall 6, 5 Ac 10. 247Ac '7 Ac 6 78 Ac (130ow .14 Jr 4, 61/ 4o 7Alit' 5 \0' '04 �T 19 20 4: it F—Pr L)o\AJN STP 7 ON 4LYS I S lb�; BS 9 r " mp jo in 'Il 4Z,r) 11 It tv wo \a 278773 r NN IV. RETENTION/DETENTION ANALYSIS AND DESIGN � As noted above in the Project Overview for this short plat we are U� going to construct a private street , 20' wide for the 5 proposed lots. Our goal is to minimize impact to the existing site, and U� downstream storm drain system by infiltrating the new house roof — runoff, and keeping asphalt improvments as small as possible. N� The requirement for storm water detention per Core requirement #3, states two exceptions to peak rate runoff control on page 1 . 2. 3-5, of the KCSWDM: � The proposed project site post-developed peak runoff rate N� for the 100 year , 24 hour duration design storm event for each discharge location to be less than 0. 5 cfs more than the peak rate for the existing site conditions; OR, � The project proposes to construct 5, 000 square feet or less of new impervious surface. The new 20' wide private street will add about 2611 square feet N� of asphalt , impervious surface. The driveways for the 5 lots are estimated to add another 2, 200 square feet of impervious surfacing. Therefore the total new impervious surface will be N� 4, 811 square feet , 0. 11 acres. This means that peak rate runoff control and detention will not be required m� INFILTRATION SYSTEM FOR EACH LOT N� ROOF DOWNSPOUT INFILTRATION SYSTEM From a soil study performed in this area the soils appear to be a N� fine sany loam, soil texture 3. From Table 4. 5. 1B, in the Sea- Tac area, the lineal feet of infiltration trench per 1000 sq ft of roof area is 60 feet . Each of the lots is estimated to have a IV. - Pg. 1 house with roof area of at least 1800 square feet . Thus each of the 5 lots will have an infiltration system of at least: N� L=(A/1000) ( I ) (k) where: N� A= tributary roof area in sq ft — I= unit length of trench (601 ) k= reginal scale factor ( 1 . 0) L = ( 1800/1000) (60) ( 1 .0) = 108 If of infiltration trench. Use at least 60' per 1000 sq ft of roof area. The trench for each house may be divided, front , back, or sides, N� depending on amount of roof area and drainage pattern to each downspout . IV. - Pg. 2 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN N� The outfall from Ridgeview Estates' s restrictor detention system flows north down the hill to SE 95th Way. The capacity of the N0 existing outfall pipe is about 8. 22 cfs. The orifice restrictor � was calculated to limit the allowable flow to 0. 56 cfs. (See the attached copy of original calculations) . We plan to add the new N0 private street and driveway collection area, then calculate the combined conveyance flow' s assuming an overflow situation from Ridgeview Estates. To calculate the combined runoff we will use NN the runoff coefficient from the old storm detention calculations. The total developed, 25, 50, and 100 year flows through the U� outfall pipe are calculated to be 6. 37, 7 34 and 8 31cfs N� ^ ' ^ — respectively. Please note that these amounts of runoff could only happen when the restrictor from Ridgeview Estates was in U� overflow circumstance. The downstream pipe is adequate to handle the additional runoff generated from the new impervious surface from the private street and driveways. For the 100 year storm it «� will require the build up of 5' of headwater in a 10' deep catch basin. See the attached calculation and data sheets. V. - Pg. I ' 1/31/96 EngeniOUs Systems Inc: page 1 Ridgeview Estates REACH SUMMARY RoUtinq based on Seattle family G 25 yr freq Network: 1 ine3: Pipe Reach Basin Area --c- --c#A- --Sum- ---Tc- --i-- --QAct Dia -Mann -Slope -QFull Vfull -Vact -Length --tt-- ' ---------- Id -----ac ------c#A- - min in/hr cfs in --a-- ft/ft cfs fps fps ft min xx7--l--a----..----S-S----LS--S---II--..--7ax--..-----x----7x--------..------ p7 cb7 1.44 0.40 0.58 0.58 6.30 2.70 1.56 12 0.024 0.0177 2.57 3.29 3.43 235.00 1.14 ' Network line2: Pipe Reach Basin Area --c- --csA- --Sue- ---Tc- --i-- --QAct Dia -Mann -Slope -QFull Vfull -Vact -Length --tt-- ---------- Id ac --c*A- - min in/hr cfs in --n-- ft/ft cfs fps fps ft min ' cs=za:zesxsss7zzasa7ss7saxcsxxxsexcc:axsxcxxzssszscsexssxxxxs7xx=c=II=xxxII=sc==czszIIzszsxzssIIsasscs7IIIIaxssxss7smssII p3 cb3 0.11 0.90 0.10 0.10 6.30 2.70 0.27 12 0.024 0.0621 4.82 6.14 3.30 48.00 0.24 p2 0.10 6.54 2.65 0.26 12 0.024 0.6673 15.81 20.13 7.53 11.00 0.02 1 Network 1 inel : Pipe Reach Basin Area --c- --c#A- --Sun- ---Tc- --i-- --QAct Dia -Mann -Slope -QFull Vfull -Vast -Length --tt-- ---------- Id ac --c#A- - min in/hr cfs in --n-- ft/ft cfs fps fps it min p5 cb6 1.83 0.40 0.73 0.73 6.30 2.70 1.98 12 0.024 0.0100 1.94 2.46 2.52 125.00 0.83 p5 cb5 3.12 0.40 1.25 1.9B 7.13 2.54 5.04 12 0.024 0.0120 2.12 2.70 6.41 283.00 0.74 1 p4 2.56 7.86 2.40 6.15 12 0.024 0.1806 9.22 10.47 11.48 15.00 0.02 pl 2.65 7.89 2.40 L6.n 12 0.024 0.1806 8.22 l0.47 11.56 205.00 0.30 1 cw-p4C_►Ty o ►e- rk?k'- e S NFA-k- � ,o 1 i i 1 1 2/ 1/96 Engenimus Systems Inc page 1 1 Ridgeview Esta�es ===================================================================== NN REACH 81JMMARY � NN Routing based on Seattle family @ 50 yr freq Network line3: Pipe Reach Basin Area --,- --c*A- --Sum- --Tc- -i'- -gAbt Uia -Mann -Slope -QFul} Vfuil -Vact -Length -tt- NN ----- [d oc -c»A' - sin io/hr cfs in --o- ft/ft cfs fps fps yt sin p/ ch7 1.44 0.40 0.50 0.58 6.30 3,05 1,76 12 0,024 0.0177 2.5/ 3.28 3.53 235.00 1.11 Network l ine2: Pipe Reach Basin Area -c- -c*A- -Sum- --Tc- -QAck Uio -Mann -Slope -Q[ull Yfo|l -Vact -Length -tt- ----- 0 oc -'c*A- - sin io/hr cfs in -o- M/ft cfs fps fps ft min NN =`======================================================== o3 ch3 O.|l 0,90 0,10 0.10 8.30 3.05 0.30 12 0.024 0,0621 4.0 6.14 3,42 49.00 0,23 p2 0,10 6.53 3,00 0,30 D 0.024 0.6673 15.81 20.0 7.83 11,00 0.02 - Network 1ine1 : Pipe Reach Basin Area -c- '-c*A- --Sum- --lc- -i- -gAbt Dia -Mann -Slope -gFull YYull -Nat -Length -tk- N� ----- 0 oc -c»0- ' min io/hr cfs in -o- ft//t cfs fps fps ft min y6 ch6 1,83 0,40 0.73 0,/3 6,30 3.05 2,23 12 0,024 0.000 1,94 2,40 2.84 125.00 0.73 y5 ch5 3.12 0.40 1,25 1,9B 7,03 2.90 5.74 12 0,024 0,0120 2.13 2.70 7,31 2H3.00 0.64 N� p4 2.56 7.68 2,7/ /,08 12 0,024 0.006 8,22 0,47 11,78 15.00 0,02 p1 2'65 7,70 2.77 J 34. 12 0,024 0,IB06 H.-22 10.47 11.84 205.00 0,29 (7 V- F:�n&� � ' 1/31/96 Engenious Systems, Inc page 1 Ridgeview Estates REACH SUMMARY IRouting based on Seattle family @ 100 yr freq Network line3: ' Pipe Reach Basin Area --c- --cfA- _-Sue- --Tc- --i-- --QAct Dia _Mann -Slope -QFull Vfull -Vact -Length--tt-- - Id ac -cfA- - min in/hr CIS in -n-- ft/ft cfs fps fps ft min asassaaazseaaaaaasxsxzsscxsxaaaszsssxscasseccxasesssssaasaccccxsssscssaxxsxsscscssscsssasassssssssssssss=xsasssaas p7 c11 1,11 1,11 1,11 0.58 6.30 1,11 1,11 11 1,111 1,1171 1,11 1,11 3.61 135.00 1.09 Network line2: Pipe Reach Basin Area --c- --cfA- --Sue- ---Tc- --i-- --QAct Dia -Mann -Slope -QFull Vfull -Vact -Length --tt-- ' ---------- ld ac --c+A- - min in/hr cfs in --n-- ft/ft cfs fps fps It min aesszsaasssaxss=sxxxxsxsssxesxsssexsssssxccxssssssssxxssscr-ssxssssssaxsszssassassxsssssssxssszssaxaessasssszsssza p3 cb3 0.11 0." 0.10 0.10 6.30 3.40 0.34 12 0.024 0.0621 4.82 6.14 3.33 48.00 0.23 ' p2 0.10 6.53 3.35 0.33 12 0.024 0.6673 15.81 20.13 8.09 11.00 0.02 Network lines : Pipe Reach Basin Area --c- --c#A- --Sur ---Tc- --i-- --QAct Dia -Mann -Slope -QFull Vfull -Vact -Length --tt-- ' ---------- Id ac --c*A- - min in/hr cfs in --n-- ft/ft cfs fps fps It min ssssesseasassssssxaaxssaxsxsxxss:czaseaasassxszsassaeaxsxsssssaasaassszsssasssassssrsxcssxxsazsseszsaseasaszsaaess p6 cb6 1.83 0.40 0.73 0.73 6.30 3.40 2.49 12 0.024 0.0100 1.94 2.46 3.17 125.00 0.66 ' p5 cb5 3.12 0.40 1.25 1.98 6.96 3.26 6.45: 12 0.024 0.0120 2.12 2.70 8.21 283.00 0.57 p4 2.56 7.53 3.13 0.01 12 0.024 0.1806 8.22 10.47 11.93 15.00 0.02 pl 2.65 7.55 3.13 L!._3.0 12 0.024 0.1806 8.22 10.47 10.59 205.00 0.32 7 Fe OM F- 1C- tA �, rr 4-1 , , 5 D �V --IT ►'vGt`IU- D� T► IC 8, � I ' G P-S (a_) I �_ _ a-" 12 > �� ' (_) / 1, I 1'Z I G VY"1 CA/ I (_L. 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'r , ' (� 1 '9 � � `b o 160 Q� n, (!rl(> 1+\ ' ,, o �'�` r` Z (.n \,ptfe0 Q'0151 1 \rl`��(1�'D ^i 1 �� ?.► qb\,�0 !}3:1 4Li t� __OGo �..� - _4�_� '�`•'� 1 82,OL I�lrn `��YC n; ,, ` phi•,. �� , �. fy ro 1 I.._ 0 r 40 '�'-0., rrj ^' l�'loo ci I I J.,� ot I } .19 7 '1 f;• � ,•.•;. •:<� .gin ,vrwool rh 10 to I ('1F � N 3y3� ,� }y(ir.t r,r �;�d i n� r.,t, - `-� � I � �f � �� - l3 ' ,,• r� ,' 'I c, 1(1 4 n )n pn a t AN' r•I n, 1 4 �hlf I lP - ! ��._` \i r �I'11 '� _�._.... _._.....___..... ..._.__. _-•...__ ..._�. _.... ._ .. �. ... _ 1/31/96 Engenious .Systems, Inc page 1 Ridgeview Estates RATIONAL DRAINAGE AREA SUMMARY Drainage Area Id: cb3 ' Description. . . . . : drainage to cb #3 <---Description--> SubArea Subic L ( ft) Slope -Kr-- (min) New AG driveway 0.06 0. 90 125. 00 0.0100 20.00 1 .04 ' Composite "c" Value. . . . . . . . 0. 90 Time of Conc (min) . . 6. 30 Drainage Area Id: cb5 Description. . . . . : drainage to cb#5 <---Description--> SubArea SubC L ( ft ) Slope -Kr-- (min) street & lots 3. 12 0.40 165.00 0,0200 7.00 .2. 78 ' 200.00 0. 0100 20.00 1 .67 45.00 0.0356 20.00 0. 20 Composite "c" Value. . . . . . . . 0. 40 Time of Conc (min) . . 6. 30 Drainage Area Id: cb6 Description. . . . . : drainage to cb#6 ' <---Description--> SubArea SubC L ( ft ) Slope -Kr-- (min) street & lots 1 .83 0. 40 85.00 0.0100 7.00 2.02 200. 00 0.0100 20.00 1 .67 ' 20. 00 0.0122 20. 00 0. 15 Composite Value. . . . . . . .0. 40 Time of Conc (min) . . 6. 30 ' Drainage Area Id: cb7 Description. . . . . : drainage to cb#7 <---Description--> SubArea SubC L (ft ) Slope -Kr-- (min) street & lots 1 . 44 0. 40 115.00 0.0100 7.00 2. 74 125. 00 0. 0100 20. 00 1 .04 Composite "c " Value. . . . . . . 0. 40 Time of Conc (min) . . 6. 30 Df�IC,( N L, OF - 1,1TION C4LC_t4L /4riONS , 1 ' KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 4.3.5D HEADWATER DEPTH FOR CORRUGATED PIPE CULVERTS WANLET CONTROL Io,000 l68 - 8,000 EXAMPLE (I, - 156 .6.000 0.36 inches 43.0 feet) 6. — 5.000 0.66CIS �3� �� X DI► � 144 4,000 ttw' tlw ENTRANCE TYPE 132 3,000 0 (feet) cot (1) 1.8 5.4 - �— 5' 6- HEADWALL PLAN - 120 F 2,000 (2) 2.1 6.3 5. ' ; (3) 2.2 6.6 4' 108 n 4. 1 l '0 in feet 3' t 1 a t l - 96 1,000 3. ; t ' 800 3 84 N 600 2 (1) 500 ' - 400 — _--' MITERED TO N 72 /f 2. 2. CONFORM Ei w 300 — - - TO SLOPE SECTION Z_ Z 60 Z 200 �+s�Q � � 54 v w cr 0 Q w 48 ¢ - 80� o x- 60 ? PROJECTING u 42 /N 5o F 1 O I ° SECTION O / — ao w I.o x C3 -- rw �6 30 ENTRANCE a ' w 0 SCALE TYPE w t- 9 33 a 0 20 (l) tfead.all 30 8 30 (2) Mitered to conform � to slope x •6 ' u 27 10 (3) Projecting rc .7 - .7 a 8 0 a 24 .7 6 5 To use scale(2) or(]) project 21 4 horizontally to scale (1),then — ____-----_ _-- _-- use straight inclined line through .6 .6 3 0 and 0 scales, or reverse as 6 — 19 illustrated. 2 1.0 .5 121Nt = UZyrS `� 5 >< I1 _ `j � govr, LF ,q ) ND 0v TJ �� /VG 4.3.5-12 1/90 ' VI . BIOFILTRATION: ' The bicifiltration fc,r this shy-Irt plat will not be required. The total amount cif asphalt paving for the street will be about 2611 square feet . r ' VI . - Pg. 1 ' VII. BASIN AND COMMUNITY PLANNING AREAS 1 VII . - Pg. 1 ' VIII. OTHER PERMITS 1 1 ' VIII . - Pg. 1 IX. ERQSXON/SEDIMENTA%0N CONTROL DESIGN The initial improvments and clearing for this proposal will be m� limited to the private street and the easements for the utilities. The clearing limits will be limited to maximum of N� about 0. 2 acres. To design a sediment trap the peak discharge from the developed N� 2-year , 24-hour design storm from the contributing area hydrograph will be used. The required surface area of the sediment trap at the top of the weir or 2. 5' min depth will be w� determined as follows: N� L = 1801 , S = 2. 8%, nm = 0. 40(existing) L = 180' , S = 2. 8%, n* = 0. 05(cl ear ed) N� Tc = ? Existing N� t , = . 42( . 40x180' ) / (2. 0) 'ox ( . 028 89min pervious area = 0. 2 @ cn = 81 impervious area = 0, @ cn = 98 Cleared tx = . 42( . 05x180' ) / (2. 0) '»x ( . 028) '« = 46. 7min m� pervious area = 0. 2 @ cn = 87 impervious area = 0, @ cn = 98 from the hydrograph calculation the peak 2-year flow is 0. 03cfs SA = FS(Q~/V.) = 2 ( . 03/. 00096) = 62. 5 sq ft A sediment trap that is 2' by 5' at the bottom with 3: 1 side slopes will have a dimension of 17' by 25' at 2. 5' of depth. This will yield a surface area of 425 sq ft at the 2. 5' depth. More than adequate for the 62. 5 sq ft required. The trap should be 2. 5 feet deep from the top of the weir , and 3. 5' deep to the top of the berm. The dimensions at the top of berm will be a N� min. of 23' by 31 ' IX. - Pg. 1 ii:BUH/SCS METHOD FOR COMPUTING RUNOFF HYDROGRAPH STORM OPTIONS: 1 - S. C. S. TYPE-IA 2 - 7-DAY DESIGN STORM N�3 - STORM DATA FILE SPECIFY STORM OPTION: �� 1 ~~ S. C. S. TYPE-IA RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP( INCHES) N�2,24, 2. 1 ______________________________________________________________________ ******************** S.C. S. TYPE-IA DISTRIBUTION ******************** 2-YEAR 24-HOUR STORM **** 2. 10" TOTAL PRECIP. ********* ______________________________________________________________________ ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TC FOR BASIN NO. 1 06/ o re-, DATA PRINT-OUT: ~~ AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN .2 . 2 81 . 0 . 0 98. 0 89. 0 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) .01 0. 67 481 —ENTER [d: ][pmth] filename[ . ext ] FOR STORAGE OF COMPUTED NYDRO8RAPN: er m�SPECIFY: C - CONTINUE, N - NEWST8RM, P - PRINT, S - STOP C II_________________________________ _ _ _ _ _ ___ ENTER: A(PERV) , CN(PERV) , A( IMPERV) , CN( IMPERV) , TCFORBASINNO. 2--- . 2,87,0,98, 46. 7 DATA PRINT-OUT: AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A I.-:N A CN .2 . 2 87. 0 . 0 98. 0 46. 7 PEAK-Q(CFS) T-PEAK(HRS) VOL(CU-FT) N� .03 8.00 708 ENTER [d: ][path] filename[ . ext ] FOR STORAGE OF COMPUTED HYDRO8RAPH: ER-DV2YR SPECIFY: C - CONTINUE, N - NEWSTORM, P - PRINT, S - STOP -- / K ' -- PORTION OF THE NW 114 OF T1-/E NW 114 OF S NW COR R 3.5 E, W. M. CITY OF REN TON, KING COON ' MON & CASE NORTH LINE OF 3-23-5 (10/94) N 8879 35' W (KCAS) 1317.81' (CAL) 160 --- ------- -- N 88 29 33" W (DEED) 1317.92' (DEED) r EAST LINE OF IS ` \ `�\`\\�� ' `� ��\� \�`� o CISGOI�ERNMENT LOT 4 )LG b� D D7':1 D-��S`,\ �� p� LEGEND - --- -- '�� ` � 4� x FD PK NA00 004 426 - ----i----- ___ � ;,�i �!� ® _ MON IN Cl - � w w w O - FD 112" R, LOT 2 ��'� L'�T` ��`'= :` n in� w • - SET 1/2' REB � AENT p i 9,447. s(I.ft'Lli ' F RS F---. , 0.21 rres 3 - � ; \�S887 "E i J r r i i �? _30' INGRESSAGRESS A O- r ' ` r ' r UTILITIES EASMENT PER F TI O N Z r ' S6S� — - -- -i RIDGEWIEW ES TA TE" PL.A IE USE ETS 3L_ -1" LOT 3 /ATE -- 7,707. sq-ft. i Tract 11"A=l W — EXISTING Wt7 a 17 acres r2,720. �q.ft.r 11 O � r _. )�S i 10.06 acres rr URPOSES, Q3 � c.;Q �� EXISTING I h HOU5.F lu c I FILLS N- ---- LOT 4 N THE r Ir r o I ---- --- I rrj • 11 — - -— ----. SAID 1 7,190. sq.ft. .4 fA r a� __ 0.16 acres r LOT 25 RIDGEVIEW ESTATES ' ER o L------- � t IC --' -_-- r __- J 2600 k I HOWN A -- --- ---- ---- 1-- __---- L 'URPOSES `3� L h� -_------------------ jlB U ' • r N.E. 26 TH c E ; 7,858. sq.ft. 0.18 acres ' o SUCH r �o / �-Ai ON IN CASE (ALLY ' ----------------- J 0.11, S88'1 '480E ��,; '__`------ P R'SON p " 30' ROAD R/W O Tract B CITY OF RENTO BY 3,9OJ. sq.f t. )6201121 MON IN CASE --- i !in/0AI KING COUNTY, WASIIING 'FON, SURFACE WATER DESIGN MANtJAL 'I'ABI,E 3.5.2B SCS W[ S I LIZN WASI IINCTON RUNOFF CURVE NUMBERS ' SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP ' LAND USE DESCRIPTION A B C D Cultivated land(1): winter condition 86 91 94 95 Mountain open areas: low growing brush and grasslands 74 82 89 92 Meadow or pasture: 65 78 85 89 ' Wood or forest land: undisturbed or older second growth 42 64 76 81 Wood or forest land: young second growth or brush 55 72 W 66 Orchard: with cover crop 81 88 92 94 ' Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 80 86 90 fair condition: grass cover on 50% to 75% of the area 77 85 90 92 Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89 Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 100 100 Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number ' 1.5 DU/GA 20 shall be selected 2.0 DU/GA 25 for pervious and 2.5 DU/GA 30 impervious portion 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 tPlanned unit developments, % impervious condominiums, apartments, must be computed commercial business and ' industrial areas. (1) For a more detailed description of agricultural land use curve numbers refer to National Engineering Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. 3.5.2-3 11/92 1 X. BOND QUANTITIES X. Pg. XI . MAINTENANCE AND OPERATIONS MANUAL i XI . - Pg. 1 i i i i 1 I I 1 ' STORM REPORT ' FOR RIDGVIEW ESTATES PREPARED BY: ' TOUMA ENGINEERS 201 SW 41ST STREET RENTON, WA. 98055 r '�',sn�eswo�,• H. r .+ WA C/ . �oF Sti' . ? f N i +.... .m 1 1 ' GENERAL CONDITION Property Area = 7.8 Acres Total Basin Area = 11.9 Acres Land Cover = SPARES TREE C = .10 For S < 5% Developed C = 3.00 - 3.5 DU/GA = 0.40 ' ALLOWABLE FLOWS A = 11.9 Acres ' Overland Flow = 1060' @ S = 1.2% V = D .26 fps 170' @ S = 26% V = 1.30 fps TC = 10 + 1060/.26(60) = 170/1.30(60) = 10 + 67.95 + 2. 18 = 80. 13 min ' I = 0.52in/hr Q = ( C I A )5y + ( C I A ) 25yr ' = (. 10)(.52)(4. 1) + (.10)(.45)(7.8) = .56 cfs Since Q > .30 cfs , Two Orifices will be used. 1 STORAGE REQUIREMENTS ' Site Area As = 7.8 Acres Overland Flow = 740' @ S = 1.2% V = .26 fps ' 170' @S = 26% V = 1.3 fps - - T 10 + 740/.26(60) 170/1.3(60) = 10 + 47.44 + 2. 18 ' = 59.62 min. I = 0.45 in/hr Q� = CIA ( . 10)( .45)(7.8) .351 c f s Q Q, CD A .351/.40(7.8) o. fs ?U' o `U?s '• V J _ . 113 cfs/Acre ' -159.07ft =-2429.5ft /Acre __.2-42 T = -25 + 85500 ( 29.9Q 1 - - _ -25 fIN 500 .9(.113) ' 134.07 min VS _ 3420 'r 29.9 Qa T T + 25 ' = (3420)( 134.07) -29.9(. 113)(134.07) 159.07ft t = 2429.5ft /Acre VT = VS Cj A = 2429.5 (.40)(7.8) = 7580 ft13 STORAGE FACILITIES WILL CONSIST OF UNDERGROUND PIPES. ' 2 x 135 = 27OLF - 72" 0, 28.274 ftz/LF = 7634 ft 3 ' TOTAL: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 7634 ft Available Storage > Required Storage of 7580 FT. ORIFICE SIZING Two-Orifice Structure is proposed to control outflow. ' Total Flow Q =-.56 cfs Flow Per Orifice - .28 cfs ' hl = 6.68 For Orifice #1 h2 = 5.68 For Orifice #2 ' a, = Q/.62 f/2gh, = .28/.62 64.4(6.68) .0217 ft' ' d, V,4 a, = 4(.022) _ n . 167 ft ' = 2.00 inches. ZD 1 I I ' a2 = Q/.62 1/2gh, _ .28/.62 V64.4(5.68) _ .024 ftl d,z = J�+.a� - Y4( .024)_ . _ . 176 ft ' = 2. 11 inches Use 2 1/8" DOWN STREAM ANALYSIS ' The drainage from the subject property drain as sheet flow northerly to ditches along the west side of Duvall Ave. Small area of off-site drainage contributes to the subject property. ' Eventually, the runoff from the Site flows into the May Creek approximately some 1000 feet downstream of the Site. There is no evidence of restrictive structure exit dowmstream of the Site. TEMPORARY EROSION SEDIMENTATION CONTROL FACILITIES ' Drainage Basin Area = 11.9 Acres ' 40% of the Site Area will be cleared . . . . . . . 3. 12 Acres. Balance of Basin Area . . . . . . . . . . . . . . . . . . . . . . .8.78 Acres. Soil type and classification - Alderwood Gravelly Loam on a, 1.2% slope with an average slope length of 1100 feet - type "C" ' RUN-OFF VOLUME DETENTION The Ground Cover is Forest (ungrazed) ' 8.78 X 350 = 3073 ft for undeveloped Portion 3. 12 X 1250 = 3900 ft for cleared Acres. ' Total Runoff Volume = 6973 ft SEDIMENT VOLUME ' 2 X 40 XC 3. 12 = 249.6 = 250 ft TOTAL POND VOLUME 7223 ft.