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RS_Preliminary_Technical_Information_Report_170503_v1Reduced
Cedar Ridge Short Plat Renton, Washington Preliminary Technical Information Report cav -, rvF � rim---}�-k �. - -- - - --d .---; Aim- . May 03, 2017 Pacific Engineering Job No. 17006 PRELIMINARY TECHNICAL INFORMATION REPORT FOR Cedar Ridge Short Plat RENTON, WASHINGTON MaY 03, 2017 PREPARED FOR Satwant Singh, Cedar Ridge, LLC. 24419105 1h Place SE Kent, WA 98030 Phone: (206) 391-3311 E-mail: pmvrsingh@gmail.com PREPARED BY Pacific Engineering; Design, L.l_..C. 15445 53rd Avenue S Seattle, WA 98188 Phone. (2o6) 431-7970 6S0NQ QI�AIa OS 00 �n . TABLE OF CONTENTS P.. aqe 1. PROJECT OVERVIEW ...... .................... ..................................................................... 3 Figure 1 Technical Information Worksheet to Follow...................................................4 Figure 2 Site Location Map to Follow...........................................................................5 Figure 3 Drainage Basin, Subbasin and Site Characteristics.......................................6 Figure4 Soils .......... ................................................................•...--.------..............-------...7 II. CONDITIONS AND REQUIREMENTS SUMMARY .............. ..................... ............ .....8 111. OFF SITE ANALYSIS...............................................................................................15 Task 1 Study Area Definition and Maps.. ...................................... ............ ..16 Task 2 Resource Review... .............................•--••--.--•--•---•.- .....................................17 Task 3 Field Inspection...... ....... ........................... — ............................................. .... 18 Task 4 Drainage System Description and Potential Problems. ........................... ...... 19 Task 5 Mitigation of Existing or Potential Problems... ........... .................................... 19 IV. FLOW CONTROL. AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ...20 Part A Existing Site Hydrology ••-•--•• ......................••- .....-•-- .................... ......... 22 Part B Developed Site Hydrology...............................................................................23 Part C Performance Standards..................................................................................32 Part D Flaw Control System ...... -.............. ..................... .............. --- ....... ........... 33 Part E Water Quality System.....................................................................................57 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN (REVISED 6123120'12)....,.......58 V1. SPECIAL REPORTS AND STUDIES ........... ........... ....................... ........ .•-•---...........59 V11. OTHER PERMITS...................................................................................................60 V111. CSWPPP ANALYSIS AND DESIGN......................................................................61 X BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT................................................................................................................... 64 X. OPERATIONS AND MAINTENANCE MANUAL ....................................................... 65 I.- Project Overview The proposed project will develop 6 single-family lots. The site is located at the southwest corner of the intersection of 156th Avenue SE and SE 2110 Place in the Renton Highlands north of the Cedar River, The address of the site is 13669 1561h Avenue SE. The site area is 1.69 acres before Right of way dedication and 1.67 acres after Right of way dedication along 156th Avenue SE. The site consists of two existing parcels that form an overall rectangular piece of property that is approximately 484' x 152' with frontage on its eastern short side along 156th Avenue SE and frontage on its northern long side along SE 2n I Place. The project site includes both on-site development area and off-site improvements along 156th Ave SE and SE 2nd Place. The site is located in the City of Renton R-4 zone. The surrounding parcels are all single-family residential also zoned R- 4. The site is located in the Lower Cedar River drainage basin. The site is located in the Duration with Forested conditions flow control area (Duration flow control with Forested site conditions) and Basic water quality control area. There are single-family residences and various outbuildings on the two existing parcels. All existing buildings will be demolished and removed for the proposed development. The remainder of the property is covered with grass and trees, The site is hilly with average slope of 11 % slopes westerly toward Grant Avenue South. There is no sensitive area on the site and no difficult conditions for the proposed development. For the onsite improvement, Restricted footprint and Basic dispersion for downspouts are used for each lots as Flow control BMPs. New plus replaced impervious area is approximately 0.49 acres before applying flow control BMP credits, new pervious area is approximately 1.18 acres. A detention vault is proposed to provide the required Duration standard forested site conditions flow control. The offsite frontage improvements along SE 2nd Place and 156th Avenue SE remove approximately 4,396 square feet of existing impervious area and create approximately 6,090 square feet of now 1 replaced impervious area (1,632 square feet of it is pollution generating impervious area) and no new or replaced pervious area. For flow control, the new impervious area created by the SE 2nd Place offsite improvement is routed to the onsite detention vault and new impervious area created by the 1561h Ave SE offsite improvement is counted as bypassed target area Per KCSWDM Section 1.2.3.2.E. The onsite detention vault is oversized, so that the developed onsite detained runoff plus the onsite and offsite bypassed runoffs meets the required Duration standard forested site conditions flow control requirements at the point of compliance (Near the intersection of 149th Place SE and SE 142nd Street). For water quality treatment, total new and replace pollution generating area (onsite plus offsite) is only 4,690 square feet (less than 5,000 square feet) and is counted as untreated discharge per 2017 Renton SWDM Section 1.2.8.2.D. No water duality treatment facility is required. 3 Figure 1 Technical Information Worksheet to Follow CITY OF RENTON SURFACE. WATER DESfGN MANUAL REFERENCE S_A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part .1 PROJECT OWNER AND PROJECT. ENGINEER Project OwnerSl[ Deye%ynment Phone _ X061.3°1 f -33rf Address Z +I I t L7,F �Jh�LAL2 S � Project Engineeriyt Company Phone Part 3. TYPE OF PERMIT" APPLICATION `. Land Use (e.g., SubdivisionWSFR Building (e.g., MIF 1 Comrner ❑ Grading ❑ flight -of -Way Use I ❑ Other Part 5: PLAN AND REPORT INFORMATION Technical Information Report W Full Type of Drainage Review [] Targeted (Check one}: ❑ Simplified ❑ Large Project Date (include revision ❑ Directed dates): Date of Final: _.. Part.2 PROJECT LOCATION AND . DESCRIPTION Project Name CE LT R CED Permit 4 Location Township --- Range Range t)5 Section A Site Address 1360 [ t th Aye, ._5�, Part 4 OTHER REVIEWS. AND PERMIT'S ❑ DFW HPA ❑ COE 404 ❑ DOE Dam Safety ❑ FEMA Floodplain ❑ COE Wetlands ❑ Other ❑ Shoreline Management 0 Rocker Struct 2!1tl ❑ ESA Section 7 Site Improvement Plan (Engr. Plans) Plan Type (check Full one): ❑ Modified ❑ Simplified Date (include revision dates): Date of Final: 2017 City of Renton Surface Water Design Manual 12/1212016 S-A_f REFERENCE 8: FLAN REVIEW FORMS AND WORKSHRET '1't:i,T1N1(,'AI.. INF'ORIMA'l'IC)N REPORT (TIT) WORKSHEET Part to SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) I Approved Adjustment No. Date of Approval: Fart 7 =NITORING REQUIREMENTS Monitoring Required: Yes f No Describe: Start Date; Completion Date: Re: SWDM Adjustment No. Part 8 .SITE COMMUNITY AND DRAINAGE BASIN Community flan: N$W Special District Overlays: Drainage Basin: L -o ',P, Stornawater Requirements: C C Pari 9 ONSITE AND.ADJACE.NT SENSITIVE AREAS ❑ River/Stream ❑ take ❑ Wetlands ❑ Closed Depression Floodplain ❑ Other ❑ Steep Slope _ ❑ Erosion Hazard ❑ Landslide Hazard ❑ Coal Mine Hazard ❑ Seismic Hazard ❑ Habitat Protection} ® LJO&P, 11,12!2016 2017 C,tty of Rei wn Sw(acc Watcr Design Manual S -A-2 REFERENCE S-A; TECFtNICAL INFOIUVIATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR] WORKSHUT Part 10 SOILS Soil Type Slopes Erosion Potential ❑ High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other ❑ Seeps/Springs ❑ Additional Sheets Attached Fart 11 DRAINAGE DESIGN LIMITATIONS . REFERENCE ® Core 2—Offsite Analysis ❑ Sensitive/Critical Areas ❑ SEPA ❑ LID infeasibility [j Other ❑ Additional Sheets Attached LIMITATION f SITE CONSTRAINT Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: 5_" Yel"W, ` kpvtj Otrot,;YL15-to 11ow", (name or description) W(evY R i V w Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: .1 Offsite Analysis Level: 1 2 1 3 dated: 0O&r� Flow Control (include facitity Standard: _Q r,, -j,� n RIEW 4U1, -W _ are&t 51'& summary sheet) or Exemption Number: C.t711Pi�r i��h On-site BMPs: [� i i j BYSiD�I Conveyance System Spill containment located at: Erosion and Sediment Control f CSWPP/CESCLfESC Site Supervisor: Construction Stormwater Pollution Contact Phone: Prevention After Hours Phone: 2017 City of Renton Surlace Water Design Manual 12/12/2016 Lief 8-A-3 REFERENCE &: PLAN REVIEW FORMS ANI) WORKSHEET TECITNIC:AL INFORMATION REPORT (Tilt) WORKSITEET Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Maintenance and Operation Responsibility (circle ane): Private f Public If Private, Maintenance Log Required: Yes 1 No Financial Guarantees and Liability Provided: Yes f No Water Quality (include facility Type (circle ane): Basic 1 Sens. Lake 1 Enhanced Basic 1 Bog summary sheet) or Exemption No.... ... I . ...... ....... Special Requirements (as applicable): Area Specific Drainage Type: SDO f MDP 1 BP 1 Shared Fac. /G) 1 Requirements Name: FloodplainlFloodway Delineation Type (circle one): Major f Minor f Exemption f ane 100 -year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: Source Control Describe land use: (commercial f industrial land use) Describe any structural controls: Oil Control No High -Use Site: Yes IU BMP: Maintenance Agreement: Yes 1 No with whom? Other Drainage Structures Describe: 1211212016 2017 City of Renton Sm rfaee Water Design Manual 8-A-4 REFERENCE 8-A: TECi�'1CAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL IN! ORIVIATION KEPOWl' (Pitt) WORKSffEET Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS Type/Description MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Type/Description AFTER CONSTRUCTION r L1� Clearing Limits ' { ❑ Stabilize exposed surfaces Cover Measures Remove and restore Temporary ESC facilities Perimeter Protection Clean and remove all silt and debris, ensure ❑ Traffic Area Stabilization I I operation of Permanent BMPs/Facilities, restore Sediment Retention ( operation of SMPslFacilities as necessary Flag limits of sensitive areas and open space ❑ Surface Water Collection preservation areas ® Dewatering Control ❑ Other ❑ Dust Control © Flow Control i © Control Pollutants Protect Existing and Proposed BMPs/Facilities ® Maintain Protective BMPs 1 Manage Project Part 14 STQRMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description © Detention LJ Infiltration ❑ Regional Facility ❑ Shared Facility On-site BMPs ❑other i 17EiYG►.`tA LA-Ftoly t.�mn[Ol, Va,u�.lsF ' { Vegetated Flowpath F(rj_1 Wetpool ❑ Filtration j ❑ Oil Control j ❑ Spill Control L)on-siteBMPs Other Sr��► ; Part 15 EASEMENTSITRACTS .J Drainage Easement ❑ Covenant ❑ Native Growth Protection Covenant ❑ Tract ❑ Other Part 1E STRUCTURAL. ANALYSIS W Cast in Place Vault ❑ Retaining Wali ❑ Rockery > 4' High ❑ Structural on Steep Slope ❑ Other 2017 City of Renton Surface Wator Design Manual 12/12/20 1 G Ref 8-A-5 REFERENCE S: PLAN REVIEW FORMS ANIJ WORKSHEET TECHNICAL RNIFOICMI ATION I�EPOIUF (TIR) WORKSHEET ----------------------- Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical information Report. To the best of my knowledge the information provided here is accurate. SignedADate I2J1212016 2017 City ofRenion Surface Water Design Manual 8-A-fr Fi ure 2 Site Location Map to Follow �cqrinient of CorninunitV St reef C I a ssifieati o n for L i ve Wo rk 1) oc ket # 11 & Economic Development AJBx PH150, Adrnneinlor Zoning Designations Road C I w5s Ific 4fl i) n ❑ IdGls h"IYEis ser,ric% M CN Cninmerdal N,�,gwy5rfto; d — Freeway Adrian i A. Johnarsn, Patrick Rcduin M Ri A parcels adjacent arterials — Primary Amu 1-!� 20M— rdl�yor � ,,R• 0.9m gMMMMMMl — CcllecbF IfrD.GWUral ftdaA ed a5•-Cft orReaka I�'RWk 1. rA R-k- FM natft r*+~ Hq pnlXwLOI Mrg w�„r� r.r � r,miml t I is Name: FI' ED+Ptanr:� 134G15_p �xckrJ .worm• Iiu%w orm dhmnI. ily accui�rrr ro NLAiJ, Ertl 9'f4i�Q115111 1�'J'ry$_y k_Qii_ I •{a�k�ruod Figure 3 Drainage Basin Subbasin and Site Characteristics i Figure..4 Soils Deference 11 - iter of Renton of I Survey Map mma. km&"L„r A%NwNwbcbm"& rlu&e Okh kia ass 1 8Aq&WFFrhO.PrwD7w i7�� b 1 ti I f o f I �' M� nP.k,aru.� IL Conditions and Requirements Summary CORE REQUIREMENTS — SECTION 1.2 OF KCSWDM 1.2.1 GORE REQUIREMENT #1: Discharge at the Natural Location Overall topography throughout the drainage basin generally conveys flows from northeast -to -southwest and north -to -south. Streets and manmade conveyance systems within the vicinity of the site have broken up these flows, directing them in various directions that eventually flow to the same, original natural discharge point of the overall basin, which is a series of wooded ravines located on the south side of SE 142"d Street approximately 2,500 feet south of the project site. These ravines convey flows south off the Maplewood Heights 1 Renton Highlands to the valley below and connect to the Cedar River. Existing micro -topography on the project site generally slopes northeast to southwest in the general overall pattern of the drainage basin, directing surface flows from the site across neighboring downstream residential parcels toward 154t" Ave SE. Surface flows in this direction are eventually collected by manmade conveyance systems in 1541h Ave SE and directed south. There are several issues associated with releasing flows at the southwest corner of the site as a developed project: • This project will require installation of a detention vault and water quality facility. • There is no existing conveyance system located at the southwest corner of the site. • There is not adequate distance on-site to disperse flows from the detention vault to the surface toward the southwest corner of the site. • Parcels south and west of this site prohibit our ability to convey flows via pipe or swale in that direction without easements across those parcels. • Emerging groundwater is already an existing problem on parcels immediately south of us along 150th Ave SE (see downstream analysis)_ • Conveyance systems in 1541h Ave SE further south (outside city of Renton) are documented by homeowners in the area as overwhelmed in heavy and prolonged rain events. The overall topography in this area is virtually flat. For these reasons, we propose connecting our storm drainage system (post detention and water quality) to the pipets conveyance system located in SE 2nd Place which flows west to Maplewood Park. At this location, the piped conveyance system discharges to an open conveyance channel / stream that flows west and south through the park before re- entering a piped conveyance system at SE 1481h Place, travelling south along the 148th / 149'x' rights-of-way to eventual discharge to the same wooded ravine south of SE 142"d that overland course from the site connects to. This is the natural discharge point of the overall basin. See Fig.X included in section Ili, Task 3 for a map of the two drainage courses. 1.2.2 CORE REQUIREMENT #2: Off-site Analysis This care requirement has been addressed in Section III of this report. 1.2.3. CORE REQUIREMENT #3: Flow Control Per SWDM section 1.2.3.3 and 5.2, Flow Control BMPs are required for the onsite development. See 1,2.9 CORE REQUIREMENT #9 of this report for Flow Control BMPs. Onsite flow control facility is provided by a detention vault to provide the required Duration standard forested site conditions flow control. 1.2.4 CORE REQUIREMENT #4: Conveyance System The new conveyance piping will be installed as needed. The new conveyance piping has been checked to confirm compliance with chapter 4 of the 2017 Renton SWDM. Per City of Renton 2017 SWDM Section 1.2.4.1: 1. New pipe system shall be designed with sufficient capacity to convey and contain (at the minimum) the 25 -year peak flow with minimum 6 inches of free board, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. 2. Pipe system structures may overtop for runoff that exceed the 25 -year design capacity, provided the overflow from a 100 -year runoff event does not create or aggravate a sever: flooding problem or severe erosion problem as described in Core Requirement #2. Any overflow occurring onsite for runoff events up to and including the 100 -year event must discharge at the natural location for the project site. In residential subdivision, this overflow must be contained within an onsite drainage easement, tract, covenant, or public right-of-way. 3. The upstream end of a pipe system that receives runoff from an open drainage feature (pond, ditch, etc.) shall be analyzed as a culvert. The new conveyance system is designed to convey and contain the 25 -year peak flow with 6 inches of free board and the 100 -year peak flow and thus meets the requirements listed above. KCBW is used for Back water analysis following the requirements of City of Renton 2017 SWDM 4.2.1.2 and designed for the 100 -year peak flow. 1.2.5 CORE REQUIREMENT #5' Erosion and Sediment Control Erosion control will be installed as necessary for the frontage improvements and the on- site improvements. 1.2.E CORE REQUIREMENT #6: Maintenance and Operations Any necessary maintenance of the onsite drainage system will be the responsibility of the property owner and manager. 9 1.2.7 CORE REQUIREMENT #7: Bonds and Liability Necessary bonds will be provided at the time the building permit plans are approved and the construction started. 1.2.8 CORE REQUIREMENT #8: Water Quality The project site includes onsite improvement and frontage improvement (curb, gutter, sidewalk, planter strip) along both 156th Avenue SE and SE 2nd Place. Due to topography and existing drainage improvements, off-site flows do not drain onto the site and will not connect to the onsite detention vault. New sidewalk improvements along bath 156th Ave SE and SE 211d Place will drain to their adjacent streets and their respective existing conveyance systems. Total pollution generating area is 4,450 square feet and is counted as untreated discharge per 2017 Renton SWDM Section 1.2.8.2.D., no water quality treatment facility is required. 1.2.9 CORE REQUIREMENT #9: Flow Control BMPs Average lot size of this project is approximately 19,990 square feet, Small lot BMP requirements per 2097 Renton SWDM Section 1.2.9.2.1 apply to this project. BMPs must be implemented, at minimum, for an impervious area equal to at least 10% of the site/lot for site/lot size up to 11,000 square feet and at least 20% of the site/lot for site/lot size between 11,000 and 22,000 square feet. The feasibility and applicability of full dispersion was studied first. The study found full dispersion is not suitable for this site to fully disperse the new impervious areas and new non-native pervious areas because long native flow path is not available due to the dimensions of the overall site. Full infiltration is also not suitable for this site because onsite soil is till soil (Alderwood gravelly sandy loam, 6 to 15% slopes, AgC) according to City of Renton Soils Map. The following flow control BMPs are used to meet the requirements: 1. Restricted footprint. Impervious area coverage in each lots will be restricted to maximum 34% of their lot sizes for lots 1 through 5 and maximum 25% for lot 6. 2. Tree retention. 4 trees along the south property lines are preserved. 3. Basic dispersion for downspouts. Downspouts of the southeast corners of the houses on lots 1 through 5 up to 700 square feet per house are treated by Basic dispersion. Down spouts of the southeast and southwest corners of the house on lot 6 up to 1,400 square feet total are treated by Basic dispersion. to SPECIAL REQUIREMENTS — SECTION 1.3 OF KCSWDM 1.3.1 Special Requirement #1: Other Adopted Area Specific Requirements No other area specific requirements are applicable. The site is not within a CDA, MDP, BP, SCP, SWCP, LMP, FHRPU or SFDP. 1.3.2 Special Requirement #2: Flood Plain 1 Floodway Delineation Not applicable to this site. There is no flood hazard area in the site. The site is not within a floodplain or floodway. The site is not subject to inundation by the base flood or channel migration. 1.3.3 Special Requirement #3: Flood Protection Facilities Not applicable to this site. There is no flood hazard area in the site. The site does not rely on any flood protection measures. 1.3.4 Special Requirement #4: Source Controls This project is a single family short plat project. Source Controls are not required. 1.3.5 Special Requirement #5: Cil Control This project is a single family short plat project in R-4 zone and this site is not a high used site. Oil Control is not required. City of Renton Special Requirement #6: Aquifer Protection Area Not applicable to this site. The site is not located in the Aquifer Protection Areas (zone1, zone 1 modified and zone 2) shown on the City of Renton Aquifer Protection Zones Map. Ill. Off Site ,Anal sls 15 Task 1 Study Area Definition and Maps The site is located on the east side of 156th Avenue SE and on the south side of SE 2"d Place. The address of the site is 13609 156th Avenue SE. The parcel numbers of the 2 parcels making up the overall project site are 146340-0045 and 146340.0049. The onsite area is 1.67 acres. The site is located in the Lower Cedar River drainage basin. See attached Site Map and Topographical Map. 16 Task 2 Resource Review The following resources have been reviewed for existing /potential problems in the study area. 1) Critical Drainage Area maps Do not apply in the City of Renton per City of Renton Surface Water Design Manual. 2) DNRP Drainage complaints and studies None. 3) Road drainage problems See description of downstream drainage system (King County) in 154th Avenue SE in Task 3 — Field Inspection. 4) U.S. Department of Agriculture, King County Soils Survey The King County Soils Survey map and City of Renton Soils Map show Alderwood soil on the site (AgD on the west portion of the site and AgC on the east portion of the site). See attached Soils map. 5) Wetland Inventory There is no wetland on the site and its adjacent areas. 6) Migrating river studies There is no migrating river within the study area. 17 Referen 11-A XM �. i V - owantrol 9tandarda IJmk Hr4 f hk, :mL•:I .'iWdwod 1I Sm Ckmidimmi Flw C•Jw i ko I I err Lu 3 Li i d■ i d l�.d i k i � $ir Ucid Yds dI RMGMn- alta l{{• 513 r42 rd Tone WM C4"WV fh` m �1_+r+k. � Vd pial PlnamtLa i W o� Flow Control Application Map N PIt1lrrdi�Ir014 •il�or 1 # r rk r1 �e__� AM 1 r �? F � •1}L I ��� � • r� Flow Control Application Map N PIt1lrrdi�Ir014 •il�or 1 # r rk r1 �e__� City of Rertor Sensitive Areas Flood Hazard ti •, t J. LL I 14. Ea I it ' � ••� •I _ I , 4 • n — � 1... t .- r k1s + I 1.- I. _• _ ' �• "�•_ � � I '• ^`2� "�� 'i' �-I�'� i I "X' _ 4r . f �I r }' Pt I...l mar _ r l J+ --• f - -� a : II�L. If�'k I O—n ,;} :. I - ' - f �� l�*` .•� fir• r. i �. - ti • _... I• �'• j , lam, ., _..lJ ... _ J1 , it I . r I i •,��_ +' r� �T 1 ;F — ' FJL' r i • I 1 I �t FLA) r, V$rk$ Da Arlmarrl G AirmNllrm..,llri,cermrw Hazard Gondi#iork rr}llr:alrntrastrur;lurff 4",.h11"dl csurvkkeG c , ate• R. KUGOn a a'JIsnaski 1 ... 1 ... a I:krd I Ina,3 FSlnrrld m " 21, F040 ��,...-�a;�, I'�a 1�rt�ra 6o Sow yc RL#ic PKdx, Aim 2frwm TW&cgiwvzm ~- ,f wmmmmV 1- r� �� r � I C*riM City of Fenton Sensitive Areas Erosion Hazards i 1 -- ll X �:: ••• It l a r.r.. -tren r rte, — `*:; �,• Jr ; I f Ir ' • ' ' _ •`_• I; I .. ri_ � f.�p i �'='• --- '-- - r - 5 �•• _... I _ ''rJ ,.� _ - .,Y":, .. ,� •III ..� - r . r'{� _ # •� i Ir C,A t _.`' Ruhlie Vwulh De"Im* fiL — 13.i1rlmw 2in.1ldmOz1rJLPM I.. ' T&yn.Lw Sw &ois ' ' ' ' ' ` ° HAZARD GMDITION Crmkal InfrestruGWre pa" U&POOMn ILIu '�urc.•��c,,,- LJ 2,LJem,%H=,.-. ii � g7d _ V 54Prr Flood �e#r ,, � 1 City of Renton Sensitive Areas Step_Slopes. Jrl — ''L •1 4 _ 17, IL � ��. 5 .I •r Li} Y • ... •I�;.,!til � ._: '�' I � #• • I !• f ..r •� `� I kms- �,��— i w}r i lrir fir' _ • I'• 1 ti I •• � ..— _.• ILI • i .v ' ..;,� ;�'•�`�, :, ._I. ' I _ - -ext- �I_ '-•�'� ��rL"-�, •L.. + �� �I.•_ S: ' � • �' tib'~ ' _ ��,_� _ Jar 1•• r % if IIrr ' I �ti� •~ it �� �� ' I - - _ '-' I � .- �}rt��� i �• — all rZ� , I!11p r MAW V+firk IDip. nrtrnnrt 51mp 5lopea P9 ruenlArge Hsmg-e OLZYAmmwi.AU7widiiPAN I 'Am 3AM' redV*:!IJ UIan:lnL • �ib76l� t- S% R. MM+7■ir. k. X1cr�l _ =-Ji �'� �2JS' C 8 �-abSC PrlNW m May 21, 2M — sW%a {{A% I.T 'INA mw!'kz till 0 EMI I K M44:11-4ti 9%PUN%Hhb P P L Task 3 Field Inspection Upstream Tributary Area Based on the general neighborhood layout and topography, there are no significant upstream flows that enter the site. Upstream runoff to the east is intercepted by the existing conveyance system (CBs and underground pipes on the east side of the street) in 155th Ave. SE and conveyed south past the project site. Upstream runoff to the north is intercepted by the existing conveyance system (ditch along the north side l CBs and underground pipe on the south side) in SE 2"d Place and conveyed west past the project site toward Maplewood Park. Downstream Analysis Surface runoff from the site currently travels overland in a southwesterly direction toward SE 316 Place 1154th Ave. SE. While no standing water or water flows were observed on the project site, surface water (likely excess groundwater) was observed flowing off parcels on the east side of 154tt' Ave SE south of SE 3rd Place (approximately 350 feet downstream of the project site). A portion of this flow was crossing 1541h Avenue SE in a wide band to the gutter on the west side of 1501 Avenue SE where it was channeled to existing CBs in that flowline. The remainder of that flow was travelling south on the east side of 154th Avenue SE in a shallow to non-existent flowline to a CB located near the end of the paved portion of '154'" Avenue SE (approximately 520 feet downstream of the property). Both pipe systems continue south through an unopened section of 154th Avenue SE where they connect to an existing series of shallow, grass -lined conveyance swales, roadside ditches and culverts (beginning approximately 1200 feet downstream of the site) in the southerly open portion of 154th Avenue SE. This open conveyance system continues south within the right -of --way for approximately 570 feet to the intersection of SE 142nd St. and 1541h Ave. SE where it turns and continues west in SE 142nd Street (approximately 1870 feet downstream of site). This portion of downstream in 154tf' Avenue SE and SE 142nd Street is more completely described in the downstream analysis prepared for MeadowVue (LUA17-000106) by CPH Consultants. 18 r cn ■ r. M AA ■ m ■ ■ WIC T4ki *F - -W �- �• R -. - _ 5 ■ Ap CL- S. hT - - ■ F , i Ar ■ +t 9" lkw F , 17Y �'� - - I _''-rte ..__---=;--, :1��. -a i �L �4IF 12 _ Z4� Los TA • I , � _ r .4 P wr do lot a i it L9 N gee 4L Z King aunty _ # V _ _ ti{�F - ' ! ! i r C71 1 1 '�T J { Ap. I W , - f �� ' -1 -k +I, • �r - IL . 4Y i' Fti R'.C_ ., F'�' y��+'r� 7'M - # k, f',' F PI'S r �4', _ I r , L•+•-� y .��,*+� � �� ���M{yi�,�F .•�',�S`�J *+ � "�� x• _ �_� •4 �,! 4' z+ ` -i IF f I'• I �k I F - "+ � � y�� � 'r~.,� •'y' Y'� �F{� _ moi} �+ it �' { L ' 14 'I, 4•. •�I }.L' .lis ,__�'x., pIV y1 5�� � fr ! � f . 4 ]' '•� :2��, k -' �ilrt - Itti � i ti * ,j IP' 'mriP. Zvi L _L7, n. Alt YYY - } r I i�I'. I ' �a' i_ � rw. —0• Y # J, jiltfor �. .lam' :�, - _ } *•' � - � - _- I� , � • ., IL .',. � • �dh "I � � . ���SE yin �•'� { R ,�+ r,• •fir i '�• - •- 'i I��� -CBS '' � { •� � • .1 Y � ,- i f ' ; :' ` I i' f '�T Y .y „ ' , 1 Y L�-L'ne0"U(F% I �a! �YF Qr VOL' L V y + .+}�. ' T •I r '.. '��-• til _ - - f•- �M1 �jl �. r� F• ��f J .r � 4i. ;.il... r—•�r''7 dh r.' •. jgq= r e ' ' f � ' ' � rt r OL '' -� ' K L rrp + 5 i' 4 1 ' i I .l r • 'y I J - 1. I d !, 1 ,u y ■ I •� IAIL. ' _may FJL •�J ' ' - — r I ■cr ' ' - FZ2' Imo; PT jr - Nmmm ■ i 66 L� Existing &aragekhed looking In the southea%t direction rfsrou8h the site. PACIFIC ENGIIVEBR11VG DESIGN, LLC 15445 5:�30 AVE, $I1 *100 Seattle, WA. 98186 L206� 431-7970 www.pELceng.corn Cedar Ridge Short flat Downstream 1609 156d' Avenue SE Renton, WA 98059 JOB NUMBER: 17 LE NAME: BY: L�[_ L7006 Pktobaft DOWNSTREAM C ONDIFTION (0 feet downstrcam of sitc). PACIFIC IC ENGINEER FNG DEEIGH, LLC 15445 53m" A E. S.r #100 Seattle: WA. 98188 (206) 431-7978 -%vww-j)accng.cc)m Codu Ridge Short Plat Downstream 13604 150 Avenue SE Renton, WA 98059 SCALE: Now DA'M MW17 SHEET-, 20F 12 JOB KUMH&R: FELE NAME: BY; LeL 1 17006Fhuwmise 2 DOWNSTREAM CONDITIO (mpproxinn ly 250 fcvt downstwam of :Hitc), PACIFIC ANG-TREER11VG DESIGN, LLC 15445 531z AVE. B., *100 Seattle, 4#. 9915a (2c[6) 431-7970 WWW-Tjdcelllz.com tdar R idgc Short f lat Down-strcam 13609 1561h A -venue Sof Renton, WA 98059 KALE. Nam DATE; YM L F ISHEEM 3 OF LZ JOB NUMPF-R; FILE NAME; BY, "-L 17W I Phutubu c 3 DOWNSTREAM CONDITIONS L4uL)K3]1g �UULI] ml+_ulr. 1J*+ PLYV. aP- (approximately 530 fect downs=am of site). PACIFIC EN INEE INC DRE.TGN, LLC 1$445 53a° AVE, S. r 910-0 Seattle, WA, 98185 [206) 411-797Q www,pacCng-COTe CfAar Ridge Short ?lat Downs# -e= 13609 15 h Avenue. SE Renton, WA 98059 SCALE: Noon DATE: 312117 SHELT: I OF F 12 J0R NUMBER; FILE KAMM: LEL 17006 P'hatob®s44 DOWNSTREAM CONDITIONS 1 A w JR LLIF; bUULLI ig1A Hir 4Y1;;3L 5,LiP4 U 1 J'7 LAG (apgroximatol-y 540 fcct downsuram of site:), PACIFIC ENGINEERING Cedar Ridge Short Plat Downsirearn D.25IGNF LLC 1 ] 3609 15 V1 Avenue SE Kent -un, w A')?Sv.).y 1549-5 5�1` AVE, S.r X100 Seattle, WA98185 (206) 411-4970 W W.1faCCnfy.CA XA I,F ; Num RATE. 3120l i F SH .E r: 5 01, 12 J013 Nt�r'InER: F] [.E: NAME: EKY= LEL I .mbf) 1 M WMappl— �1 •. ,IF •_ �.. r - : .• � �-r: •- a �_ •Y r'•,�' -'mss -•� =';• r.. •.. '�.. +•'� • ,:r �' - - •'fes Looking scuds along Else gutter on the west side of ] 54'11 Ave. SE (approximately 6$0 feet downstream of situ. PACIFIC ENGINEERING DH,9I AT, LLC 1�44� sA- AVE. S., #100 Seattle, WA, 9838-0 1286) 431-7970 WWW.paccn-c0 Cedar Ridge Short Plat Downstream 13609 15 616 Avenue SE Denton: WA 98059 SCALE: N-Drx uxrg: 3120117 & P'.F•.'r. 6 O 12 JOB NUMBER: FILE NA -ME. 9 Y: LBL I n06 Phakobeac 6 4 1 Ir WO� V �' � r ,.j �r•JI J� �,+� • r��: ��•r r,.,.. � i•_ I:y)'x 1 �~J r' I �r�'�y.+�yl r - 1 I�j''F7_' Ir�47 ' t ••I �r .. �•_J, I.TA_ 1 •4�',f14"F''r ' .L•'L a'{'Sy+ 7r 1!�_•_JLL '-•1 �.L-�Ir••u.1,..'•i+��r'', ''k I ••r'.•f = f ,r� '�r i •'{�1y ���y � ray �'�� '�.� •-. .'�'�,,��'l� y_r'^''•ri I F.S�k' I� 4'ti •y'� , = I•��� I L•..F ,F'••:�,r. .ter: '�. i�{' '4 y : 1 F ;�y 1•' f 1 y��k �r�''�•l ,.3�i'. 'k' 1 '�: .I •'.i• r•J r f•i %-: �•y.• y ' � �, ` - ?:''_ _ • } 1., II.r• �e ' 'fir � �5 '.ti"Y`_ } 1 -' f�J' •T� � •'� ' • • lLr Ye'`,,. _ � Jti �;fi. • tom. ti;,�3:. 'i : _�,S 1 { •, .•'�. •y• r • � � _ ' � ' _ �: ��.+ .. 1. �_ ;t' ,ir`_. .: _. .11 . t ; �• '�1 ' 1 •' 'I •' i� .S � � , r r �,�",fir k r, li; rt: L ..I • �ti t 3 .5��'rr } •�w1•':�' `I ti.� I. �1�• r �..' AI{.•��� 1 .,,� ��, 'i •_ ° • - ��.. r.y ...'�• l i �� -.•� I - - .. {• yr [A �{iFr n� + v l ', 4 � /_r- r'��.�'l�+i.�•'. 1 c+ 1 Sl- Al �` ~•�i �{f ••L r ,Yrr ti~��� L F � {'� r I{' •. + i r'y 1 1 F f �'• �,+ �'R - - J�'� fr •+ r� S. r � a •L� L �� � YV•} Af ' �,r'� �f - ' : � � ' r •fir �• - r , � ,� rr r� � • ' F DOWNSTREAM CONDITIONS (a ximately 13`78 focE d wn%trcxrn of %de). PACIFIC ENG-TIVElJ'RIB G L?B IGIV, LLC 15445 UP" AVE, 8, , #104 Seattle, 'KA, 9818B (206) 431 -?970 Cedar Fridge Short Plat Downstrearn 13609 15 61 Avenue SE R mlan, WA 98059 4{:AI.F'.: U111IL! DATE: 1120? 17 Nil IF. '1: ()1 1.: J013 NUM131{11: F11.1{ NA}IF.: B:V: L:kQ: L7006 1 k'holkillasL 8 I)OW N S'1'R H;A M CoN1)I'1 I0N L««kIng soudi along the cost side of 1546 live. 5E (approxi=ely 15 30 feet dovoisrream of site)_ PACIFIC ENGINEERING DESIGN, LLC 15445 53RD AVE. 5 *1�0 Saattl$, WA. 98198 �20$] a.31-7970 www.paceng.co Cedar Midge Short Flat Downstream 13609 15611 Avenue SE Renton, WA 48059 SCALE; plana DATE: RM? H SHE IST; 1) ()F L 1 JOB NUM M, FILE MME. BY; LP_.I 1 ]FOLIb Pbot-Dboso 9 DOWNSTREAM CONDITIONS i ftJ I.46king south slang the wesL side, of 1501 Avo. SE (approximately 16SO feet downstream from site) PACIFIC EN INFERI N( DESIGN, LLC 15+145 53'° AVE, 8, , *log Seattle, WA. 98188 (2 05) 431-7970 www.paceng.co Cedar Ridge Short Plat Downstream 136N 1561' Avenue SE Renton, WA 98059 €:.41.1{ : Vtimc DAA 312M 7 41 [F:F:7': I �} � FI- 15 ,PUD MUM DER: FILE NAM E: BY: ].l,.T_ 1 17006 PhcMcihssc 10 Look ing South along the east side of 1541h Ave- SE. (approximately 1980 feet downsu am from site)_ PACIFIC rMlIVERIZING DEI::, LLC .. 15445 53no AVE, �- j 4100 Seattle, WA. 98180 (204) 431,7930 www. pacenc Cedar Ridge Short Ply Downstream 13609 156" Avenue ;SE Renton} WA 98059 SCALE; None vikTE; 3aOl'L F SHUT; T; I I o I: 12 aoa NUyfuha: FILE NAME: BY: LEL L 7-004 PhotDbnsc ] I (sPProx i mately L 950 feet downmeam of Rite). PACIPIC ENGINEERING DES IGNI LLc 15442 5370 AV -4. &. r #100 Seattle, WA. 99188 (200 431-7 70 Cedar Ridge Short Plat Downstream 13609 156" Avenue SE Renton, WA 98059 ,SUB NUMBER: FI 1A;. MANIC{: BY: LEL 1 17006 Pbfkobaw L2 Task 4 -Drainage S stem Description and Poterrtial Problems There are no unsolved existing and potential drainage problems within 0.25 mile downstream of the site other than the observed groundwater surface flows along 1541h Ave SE. Further south in the King County portion of 154t' Ave SE (gravel road surface) approaching SE 142nd Street (0.25 --- 0.36 miles downstream), the topography is quite flat with roadside swales and culverts. Discussions with residents in this unincorporated area of the county indicate minor flooding issues with this system during intense and /or prolonged rain I snowmelt events. Task S Miti ation of Existin or Potential Problems There are no unsolved existing and potential drainage problems within 0.25 mile downstream of the site, For the onsite improvement, Restricted footprint and Basic dispersion for downspouts are used for each lots as Flow control BMPs. New plus replaced impervious area is approximately 0.49 acres before applying flow control BMP credits, new pervious area is approximately 1.18 acres. A detention vault is proposed to provide the required Duration standard forested site conditions flow control. The offsite frontage improvements along SE 2"d Place and 1561'' Avenue SE remove approximately 4,390 square feet of existing impervious area and create approximately 6,09€7 square feet of new I replaced impervious area (1,632 square feet of it is pollution generating impervious area) and no new or replaced pervious area. For flow control, the now impervious area created by the SE 2"d Place offsite improvement is routed to the onsite detention vault and new impervious area created by the 1561'' Ave SE offsite improvement is counted as bypassed target area Per KCSWDM Section 1.2.3.2.E_ The onsite detention vault is oversized, so that the developed onsite detained runoff plus the onsite and offsite bypassed runoffs meets the required Duration standard forested site conditions flow control requirements at the point of convergence (Near the intersection of 149th Place SE and SE 142111J Street). For water quality treatment, total new and replace pollution generating area (onsite plus offsite) is only 4,690 square feet (less than 5,000 square feet) and is counted as untreated discharge per 2017 Renton SWDM Section 1.2.8.2.0. No water quality treatment facility is required. With connection to the piped conveyance system in SE 2"d Place, the proposed development will not create any adverse impact on the downstream drainage system in either direction between the site and the wooded ravine south of SE 142"" Street where the two downstream systems re -converge. 19 Downstream ma s anti Photos 20 IV. Flow Control and Water Qualily., Facility Analysis and Design 21 Part A Existing Site Hydrology Duration standard forested site conditions flow control requires matching developed flow duration from 50% of pre -developed 2 -year peak to full 50 -year peak and matching peak discharge rates of developed 2 and 10 -year peaks with the existing 2 and 10 year peaks. Existing site condition is forest condition per City of Renton Flow Control Application Map. Offsite frontage improvement along SE 2"d Place This is an existing developed street Right of way. Total drainage area = 0.334 acres (the south half right of way along the frontage of the site) Total existing impervious area = 0.229 acres Total existing pervious area = 0.105 acres (till grass, soil group C) Offsite frontage improvement along 166th Avenue SE This is an existing developed street Right of way. Total disturbed area = 0.050 acres Total existing impervious area = 0.005 acres Total existing pervious area = 0.045 acres The 1561h Avenue SE drainage system has a different drainage path from the SE 2nd Place drainage system and the onsite drainage system. All three drainage path joins to a stream that drains to the Lower Cedar River approximately 0.75 miles downstream from the site (Point of compliance). Onsite improvements Scale factor = 1.167 (Seatac) Total onsite area = 1.67 acres (assume till forest, soil group C) 22 Q %VWHM2012 5a#viantRenton HE Edit View Zoom Help C9 rlECa�� a 10- Z O i TV. Site ldwmelwn:.•: :3.a N.SEb�d . PdSua la[t9:i'fipiAvs` 23 WkWW012 Sato/antRenton File Edit View Help SummaryRepart D Del ® R Subbssin Name-. Surface # nterflow Groundwater FI aws To: ICK a nal....... .: ;::...,....; . ..•.....•::: ►ren in Busir7€ SFia i€]111+,5 lrwcted Available Pervious Acres Available Impervious Acres i A10 Fore k Flat:':::< t� ASH F�irest'W&:%;:;.::::.:<:::. = `: ROADSlMOD -A/0 Forest steep::...'.:.;:::;: f�:.� - ASB Pasture Fiat:::':;: : '':: P RQl7F: TCl .VFLAT.:'::>:::.:' = A/B, Pastry Mad.:`:`;f7gRIk1AYSF[AT`:;;:::';:; . it A/S Pasture aa i- :; Fl;°:::::.:.:.::: : :: Ir—AM, Lawn :. a I YS STEEP:::.`:::::: A }EWA dit = AYB .E......rr tvicsd:` :::;.'::.::::: aw • SIDE LKS2FLA VJA T AM'.Lawri Stee :`::':::; ;..: SIDi~WALKSityIEJD:.::.'::::::.:. - .............:. SIDE Ai.KSSTEEP;:>::::;::: C PARKING/FLAT.:..:::::::...:::::::: " ;.C. Faresk' Skee ':`:::.::;. ,,;:,:;. it ,�.�. '."..::P�1€�K{hlGIf�ICrC�:::.::;::::.: �` i CP stur6 Flat PARKIN GiS.TE - :L" Past re oPOOEM C Pasture step .::>:..::::::';::: Porous Pavement :':::':::;" .:::::::.:.:.10 24 lAJlt', HM20T2 SatwantRenton File Edit View He#p SurnmarXReport D 9?1®a Y It am Suhhasin Name: Surface Interilowr Groundwater Flaws To: Area. in Basin j Shan i]n! Seiecfed :`. 25 :.. ! Acres p' 'I - rV:. ROADS/M0f} A/0 : Foies1 M 6d.:: A/6`.Fo est' S e .; r #e R. `. `. DRIVEWAYS/I�OCi `..%.QRIVEWAYS15TEEl}':.:.:: ASB Aastufe FI 'rpt : ' - j�':''.'.: SIDEWALKSIFI:.�� `SIO AI81Pkuf6, Mod _ :::: PAIS I N Ca IFI..AT :.::.: `:' ::;::; : ;:: K D-: :.•. - PON[ °:::::;;:;; A/B ` Lai iri !'arcus Pave menk Aa8, La vn, I`+ 6d :.: AIB Lawm 5tea ". ..C" .o e - C, Pasture, Mod �• ; :. ;.:.`;:: ;''...;': C .Past re Ste €r a CA a FO � .... I Iwarr�rti,. T SAT FafesLFlat 25 Available Impervious ROADS/FLAT Acres p' 'I - rV:. ROADS/M0f} ROADS)STI7EP r `. `. DRIVEWAYS/I�OCi `..%.QRIVEWAYS15TEEl}':.:.:: fx - j�':''.'.: SIDEWALKSIFI:.�� `SIO _ :::: PAIS I N Ca IFI..AT :.::.: `:' ::;::; : ;:: K D-: :.•. r:; PARKINCfSTEEP . PON[ °:::::;;:;; !'arcus Pave menk 25 rl-11 MM NAMFIN12012 SatwantRenton File Edit View Help SummaryReport B Gi�l 61 � d% % Oft . . ........ ............ . . ... .................... ....... .. ............... .... . ........ ... ............... I Irmliml r(MIMINUMMI Subbasin Name- 17777 I&hj6w SuFface Intowflow Groundwater Flows To: 5 year 0.276802 10 year 0.339937 Area in Basin 0.4297 50 year 0.504201 100 year Available Pervious Acres Available Impervious Acres ML ROADS?FLAT..�..: W TdA'I�S MOD noADs/STEEP f-. A/8 P�Stbfe, Flat::::::.::::..: 478, -Fasturd, Mod. W..ROOFTOPWFLAT..-.� DRIVEWAYS/FLAT..... 17.:A/B; Paswfel SWO...: DRIVEWAYS/ 117. A/81 Ld�vh,- Flat': DR ME-WAYS/SlEEP SIDEWALKSMAT� f-:A/B, Lawn, Ste;-p�� SIDEWALKSMOD. F.:C, Fcrest, Flat.: SIDEWALKS/S' r,o. C, Fcn�st, Myd!� PARKINWFLAT 777777� r C, Faiest', Ste* .................... . PA8KING/MOD..'::.::..:. , �p r7..-PARKINGATEE C, Pasture, POND:..�:.:%.:........:::.�...�.�.%%: pad6ra S(6a� ................ ...... . . . C, FW ...... ..... C, Fomst, Fl r.:..SAT Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfz) 2 year 0.193946 5 year 0.276802 10 year 0.339937 25 year 0.4297 50 year 0.504201 100 year 0.585572 26 Part B Developed Site Hydirology Offsite frontage improvement along SE 2"d Place This is an existing developed street Right of way. Total drainage area = 0.334 acres (the south half right of way along the frontage of the site, this area will be collected and conveyed to the onsite detention vault) Total existing impervious area to remain = 0.135 acres Total new plus replaced impervious area = 4.116 acres Total impervious area = 6.251 acres Total pervious area = 0.083 acres (till grass, soil group C) Offsite frontage improvement along '156th Avenue SE This is an existing developed street Right of way. Total disturbed area = 0.05 acres (this area will be collected and conveyed to the existing storm drainage system that runs along the east side of 156'x' Avenue SE and Bypass the onsite detention vault) Total new and replaced impervious area = 0.02 acres Total pervious area = 0.03 acres (till grass, group C) Onsite improvement Under developed condition, onsite runoffs will be collected and conveyed to the onsite detention vault. Onsite impervious area calculation (before applying Flow control BMP credits): Roofs of lot 1 through lot 5 = 3,000 sf per lot. Roofs of lot 6 = 2,400 sf. Private, driveway, walkway and parking for 6 lots = 3,600 sf. Driveway to detention vault = 480 sf. Total impervious area = 21,480 sf. = 0.493 acres Total onsite area = 1.67 acres Total onsite pervious area = 1.67 -- 0.493 = 1.177 acres (till grass, group C soil) 27 �:•r.•.hrk.kzo�a SaHran�RenkcnOr Fla Edik Vi- Zu . H4 fi4f} $4&'IO�p I' A S '. 28 Q 1"VHM2012 SatvvantReritonDev File Edit View Help Sum wary Report D GO 9 1 � fib Eft Im%_0 dn Lot I.M. nolo-im Subbasin Name:j= Surface I'laws Taiz Area in Basin 14 J & w Ground"ateg 7 5- elaciedl Available Impervious r:flOADSXLAT.%�.:L- Available Perviaw3 AAB.Forest, Flat :.= Acres ROOF TOP5iFLAT%..: r.". DRIVEWAYS/FW. A/8; Formt, Mod rt. w[Awys/mo ........ .. .......... A/8 , Forest: Steep IOETEEP.�:....... SWALKWS .. . .. j A/ig, Pashk6, NI), PaSkka, Mod J—. PAA,K1NG/MOD..:.-.- Pastime` Ste' f�.T'0-106; ..... ................. C, Faest, Flat. C. Far est, . ..... Forest , teep FQ iF asture-, ROT— 77-y ....... ............. . Steed........ . ie, C. N � C, Lawn, Flat R�.C.LOwn,Wd . .... . .... f—.-S.AT, Fwast, F1&%-7 14 J & w Ground"ateg 7 5- elaciedl Available Impervious r:flOADSXLAT.%�.:L- Acres AP 90ADS/STEEP ROOF TOP5iFLAT%..: r.". DRIVEWAYS/FW. M rt. w[Awys/mo DREVEWAYSISTEEP SIDE-WALKSi [A r-..Sf0CWALKSN IOETEEP.�:....... SWALKWS .. . .. j PARKINGIFLAT777771 J—. PAA,K1NG/MOD..:.-.- . f�.T'0-106; PeTV.ousTotal Impeiviom Total Basin TQW Deselect zeio Select By: 29 Q VAVHM2012 SatwantRentonDcv File Edit View Help S(immary Report n Q; 611 A % Ch .............................................................................................................. Emlift—mowmk A 1,11 amh 0 Subbasin Namw 1— Designaie . as Bypass [of POC:m Surface Interflow Groundwater Flows To -.k Area in Basin Available Pervious A/0, Fofest:j: Pbt. Acres ftA?8IF6j6a,M6d: ROADSISTEEP A/8, Forest, Steep A/BPastu AIB, Pait6i6, M6 � AIB Pas�ure, Steep: ......... ... .. .. [7. AIR, UAn, FU At I L6whl DRIVEWAYSATEEP...' LL. 17. C, Forest, Fla(....:. SIDEWALKS]M r. C. Fofast, 9 tftap SIMWALKSIST f77% C, Nstule, PARKING/FLA.T...... PARKINGM01). 117' C, Lava6,:Steep PARKINCi/STEE SAT, Faest, Flat:m ..................................... 777� S k6w�nl�: seleQt6d.:. Available Impervious Acres ROADSISTEEP DRIVEWAYS/FLAT � DRIVEWAYS MOD :::. DRIVEWAYSATEEP...' SIDEWALKSi SIDEWALKS]M SIMWALKSIST PARKING/FLA.T...... PARKINGM01). PARKINCi/STEE 777� 30 \,VWHMZDIZ SahvantKentonl)ev Fite Edit View Help StimnfaryReport 'Mal-11%mm—'101MIM MR] Offil Subbasin assio[PCfC Surface Intcrflaw 6rnundwater Flows T = ❑ n. F1ow(cfs) Area in Basin Available Perviaus r : 5E7vw.l]nly:selected Acres Available Impervious ROADSJFIAT:::.::.:.::::::::'.::::: H 1M ROAMSTEP FW. ROOF TgPSlF'CAT:`:::':::`:>::'. ........:..:....:.. .©RiVEWAYSM ATs; Z-- r ORIVEVIAYSMCJU:`.:::::= RVEWf �iYVSTEEP:: l ;i:'::';?; ` s: .i : SIDEWALKS1FLfiT :.: f'">5€QEVJALKSiMiJDi.::=.:::::::. 7'E : •':::::': :SE[7E4Vf�LKS15 L P PAFIKINGfF :-': `_ <;-:;::::_ : r:: PARKINGNOD.:::::::.. r r.._A KtN17. 1� POND Por u Py m Acres 0.76618 !Alla FbbtisOte-ep. r. AlB Pastiai� Stee `.::::.. Alla Lawn F1aR A1B L wh 6d.::::::.:.:'.: ; 0.518046 :............................:..... 1.122584 50 year A..284265 17. l;:Foresi.flat:.:.;::.; - v. C. Faros€: C. Farest. Steep � Pasture Fat C. ;N tune Mod::;::::'.;.':::: CPasiure;Stee j + C, Lawn, Flat U:=::.,. ' •;, •:. ; •. Jf7.:C, .awn, Steepl.. SAT'. Forast; Flai`: ImpeIvious Total Basin Tata! ii.d5:', Aries, :- Dese€e-t Zero Select By: ' `'r'..''' `i :i G© Flow Frequency Return Periods for and no flown control SMPs) Return Period F1ow(cfs) 2 year 0.553387 5 year 0.76618 10 year 0.518046 25 year 1.122584 50 year A..284265 100 year 1.454035 Developed condition. POC #1 (Ho detention 31 Part C Performance Standards The site is located in Duration Flow Control Area (Forest existing condition). Since no problem has been identified within the site and its downstream area, level 2 flow control (forest existing condition) is required. Per SWOM section 1.2.3.3 and 5.2, Flow Control BMPs aro required for the onsite development. Flaw control BMP's for more than 10% of each lot area is required for lots 1 through 5 and Flow control BMP's for more than 20% of the lot area is required for lot 6. The feasibility and applicability of full dispersion is studied first, the study found full dispersion is not suitable for this site to fully disperse the new impervious areas and new non-native pervious areas because long native flow path is not available. Full infiltration is also not suitable for this site because onsite soil is till soil (Alderwood gravelly sandy loam, 6 to 15% slopes, AgC) according to City of Renton Soils Map. The following flow control BMPs are used: 1. Restricted footprint. Impervious area coverage in each lots will be restricted to maximum 34% of their lot sizes for lots 1 through 5 and maximum 25% for lot 6. 2. Tree retortion. 4 trees along the south property lines are preserved. 3. Basic dispersion for downspouts. Downspouts of the southeast corners of the houses on lots 1 through 5 up to 700 square feet per house are treated by Basic dispersion. Down spouts of the southeast and southwest corners of the house on lot 6 up to 1,400 square feat total are treated by Basic dispersion. For lots 1 through 5: Average lot size 10,655 sf. 10% of the lot size = 1,066 sf. Total impervious area in each lot is restricted to 3,600 sf. Total impervious area treated by Restricted foot print = 4,000 --- 3,600 = 400 sf. Total impervious area treated by Basic dispersion for downspouts = 700 sf. Total impervious area treated by Flow control BMPs = 1,100 A > 1,066 sf., o.k. For lot 6: Lot size = 12,019 sf. 20% of the lot size = 2,404 sf. Total impervious area in this lot is restricted to 2,996 sf. Total impervious area treated by Restricted foot print = 4,000 -- 2,996 = 1,004 sf. Total impervious area treated by Basic dispersion for downspouts = 1,400 sf. Total impervious area treated by Flow control BMPs = 2,404 sf., o.k. Final signed Flow Control BMP Covenant is required prior permit is issued and will be recorded with the Final Short Plat map. Onsite flow control facility is provided by a detention vault to provide the required Duration Flow Control (Forest existing condition) for onsite area and offsite improvement along SE 2nd Place. 32 Since total new plus replaced pollution generating impervious area is less than 5,000 square feet, water quality treatment facility is not required. The proposed detention vault provides 1' dead storage and 0.5' sediment storage which provides enough sediment control. See Section 2 of this report regarding special requirements, the only special requirement applicable to this site is special requirement 1.3.4 for source control. Dumpsters and recycle bins will be stored in the garages of each houses. Since the site is not a high use site, oil control is not required. The new onsite conveyance system is designed per chapter 4 of the 2017 Renton SWDM to convey the 25 -year peak with 6 inches of free board and the 100 -year peak €lows. For offsite frontage improvement along 1561h Avenue SE, as discussed in Section 1 of this report, no flow control or water quality treatment is required. 33 Yart t3 :Flow Control System Offsite frontage improvement along SE 211'�' Place This is an existing developed street Right of way. Total drainage area = 0.334 acres (the south half right of way along the frontage of the site, this area will be collected and conveyed to the onsite detention vault) Total existing impervious area to remain = 0.135 acres Total new plus replaced impervious area = 0.116 acres Total impervious area = 0.251 acres Total pervious area = 0.083 acres (till grass, soil group C) Offsite frontage improvement along 1561h Avenue SE This is an existing developed street Right of way. Total disturbed area = 0.05 acres (this area will be collected and conveyed to the existing storm drainage system that runs along the east side of 1561x' Avenue SE and bypass the onsite detention vault) Total new and replaced impervious area = 0.02 acres Total pervious area = 0.03 acres (till grass, group C) Onsite improvement Total onsite area = 1.67 acres Total impervious area = 21,480 sf. = 0.493 acres (before applying Flow control BMP credits) Total impervious area treated by Basic dispersion of downspouts = 7* 700 = 4,900 sf. (credited as 90% impervious area, 10% grass) For lots 1 and 2, dispersed flow from their southeast downspout and the back yards of these two lots sheet flow to the west adjacent lot bypassing the onsite detention vault. After apply the Flow control BMP credits, onsite drainage area draining to the detention vault = 1.408 acres Impervious area = 21,480 — 4,900 + (5 * 700) * 0,9 = 19,730 sf. = 0,453 acres Pervious area = 1.408 — 0.453 = 0.955 acres (till grass, group C soil) Onsite bypassed area = 0.262 acres Impervious area = 2 * 700 * 0.9 = 1,260 sf. = 0.029 scres Pervious area = 0.262 — 0.029 = 0.233 acres (till grass, group C soil) Flow control facility: A detention vault is used to provide the required Level 2 flow control (forest existing condition). 2012 WVVHM method with 15 -minute time step is used to size the detention vault. 34 The proposed detention vault (74' long x 36' wide x 7' live storage) actuary provides Level 3 Flaw control (forest existing condition) performance. 35 VMHivi201? SahvaritRenton File Edit View Help Summary Report Impeivious7otal Q.Q2S :::::<:: Acees.: :.';: .. �� - Subbasin Narrre= v e e y a,; :>:' : ':;::' ' rte: D] Signate W: Bypass f0i POC. Surface l nterfluw Groundwater Flows To : IChia'::: � Area in Basin]� :.Sfiow.bnil 'QPeted::: Available Pervious Acres Available Impervious Acres ]6 Fb est A F Flat'::':::::::::: ©D51FLA :' ::.::::: ::;::. R A T. M Fomst, o '. DAD51 OD:'. `....10, fB Forest, Stee :'`; :"+ ROADS/STEEP.:.'::'; .:. Af$ Pastiafe; Flat';':.::r:..: ROOF TOPVFLAT A , P . N+ d : ;::::::: fB astuie c ::: Q:'' �'' = ' ................ D 1 AYS FCA R �fFV�t 1 1 . r... r`. A 8 Pascua Stca '' E�RiV+fA�'S1Milf`.:'r::::':` AM LdWrL Nat:::`: :,:::.::. .. DIVE A S]STffiP---.- . A18 Lam Mcsd:: " :::..:;' : SIDEWALKS1FtAT:FM G Forest,Fiat:.:::::::;:::::.;:. SIgE'rJALKSISTEEP..:........ _ C' Forest. Mad:..: ;:;:':.:::;; it `:' <i:_ _; '::': :: PARKING1FLAT: 1 C Fa€ast Steg .::: PARKIis€G- r C Pastuie a`== r a PARKINJU/S E -EP -1. : G Pasture Mad 77771 POND i F::C, Pasture, Sten ,;' .< :`:': r P€irous Paver€ienE:::::...:::..::::::: s �' G Lawn, Flat i . � jtii C, Lawn, Mad ;�33,:- :•r ::'.: ! F C. Law Stee+ "::SAT; Fares,, Flat. Parv=Total Impeivious7otal Q.Q2S :::::<:: Acees.: :.';: .. Owin Total . . DeselectZera Select Ry:_'<<''`: ;'.'``"`'' . ;`:: GO 36 Q,' VAWWO12 SatwantRenton File Edit View Help SummoryDeport 1) GO 6119 Nb oft Subbasin besign4was D-v6ass fel POC. izw Surlace Intedlow Groundwater Flows To 2-= F ............. Area in l3asin PavjousTotal Available Pervious AM, Vdmi;t, Rat. Acres lmpervious Total 17. NBForest, Mod::. A S Dash T oW AiB, Fixed, Steep rZa Name. j-; DRIVEWAYS)F r DRIVEWAYUMOD. ORIVEWAYS)ST AIB store2e-P- r. SIF�EWAE.K51Mi�D r Aig, Lawn., Flat: r AtIBu, LL 6 Wn, Stec PdfoLn Pavement C. Pastwe, r: c, Paswie, steep r C Lawn, FW.: ry� CI Lawn, Mod.... c 'Lmyn, Steep-,:-. PavjousTotal Acres RQADSWLAT::. 7-7-7-1 lmpervious Total rl� RUADSIMOD...'%. A S Dash T oW rV WjY f6 FS—If Nf Available Impervious Acres RQADSWLAT::. 7-7-7-1 rl� RUADSIMOD...'%. r SYSTEEP:%.::= rV WjY f6 FS—If Nf j-; DRIVEWAYS)F r DRIVEWAYUMOD. ORIVEWAYS)ST r. SIF�EWAE.K51Mi�D PARKING/ PdfoLn Pavement DesefactZero Select By- jm7MI'ii �.- -Go. 37 WVVHI,12012 SatwantRenton RL Edit View Help Summary Report D 2r 9 1 It RR, a Irk-=. 9 MIMNIM132-0 0 Subbasin Name -MR, Surface Flows ToFZFF Area in Basin r Des;ggnate�as 13+pnsIoj POC: Interflow Groundwater r":S116W 0 .Sd ted.::.: Available Impervious Acres Available Pervious Acres F. AID, Folast, Mad..� ... .: .... ... .. .... Basin T oW ... .... .......... ... DeselecEera A?B i Fewest, SlaeO- AM , PasWre, Flat .m. 17 A/B, Pastupa,..Mod ..... ...... . ..... A?9, s J D! E 1T4 US - NO, Lawn, Fla. ..SIDEWALKS /MM NO Lawn, Mod-: 17. A/OLawn, Steep::: PARKINGIFLAT::..�. PARKINGMEEP Porbw Pavement j 7.. C, Forest, C'Pasturo, Rar::.. C. Pasture, Steeg ir C, Lawn: Mod SAT, Forest, F1 Available Impervious Acres ft:: HQADSIFLAT....:-�� �v Impemous Total ROADS/MOD: Basin T oW ... .... .......... ... DeselecEera ROOFTOPSIFLAT DRIVEWAYSISTEEP s J D! E 1T4 US - ..SIDEWALKS /MM SDEWALKSISTF�- PARKINGIFLAT::..�. PARKINGMEEP Porbw Pavement 38 Impemous Total Basin T oW DeselecEera Select By- cio I 38 0 MHM2012 SatlrjantRzmton File Edit View Help SummaryReport Subbasin Namo- M Surface Flows To F— Area in Basin r::D t .9� o to, POC. esigna e as pa 1"taillow PemousTotal Available Pervious Acres ADS ❑MOD A/8. Fwb�l, Mdd. AM, Forest f7i AID,Pasture Acyez:' A/8, Flattua, M ad TW A10: Pastw LaWn, Flat.:. AIB L hind C, Forest', FW. 17. S Faiest, Steep:-:'� f7c-, PWtum, DRIVF-WAYS)MO I)RIVEWAYSYSTEEP 17.: S I DEWALKS)FLA t�.:SIDEWALKSMO C, pa'3Wid' m6d: teep ---- i J7 C, Pasture. 'E ... . . .......... .... ...... ............ ........... ............ . . . . ....... .. .... ... ......... ..... POND C,� LaWm M ad. ................................ r c, I awn' steeV:. SAT, ro7i 6 s i, F !J PemousTotal Acres Impervious Total ADS ❑MOD Basin Total Acyez:' rsph4 Available Impervious Acres ADS ❑MOD r-.:ROADMTEEP: ................................................ 7. DRIVF-WAYS /F DRIVF-WAYS)MO I)RIVEWAYSYSTEEP 17.: S I DEWALKS)FLA t�.:SIDEWALKSMO PARKING/FLAT.:.':::;:::.:':: PARKING &OD.;:... PARKINGYSTEEP: POND Pardus Payernimt Deselect zefe--- Select By- 17 Flo - -------- ---- ..... ..... I .............. .. . .... . .... ........ ............. 39 UW MMM2012 SatwantRenton File Edit View Help Surnrnafy Report: d� ��[0 [2 1 �� 1 9 i 9.. lFacilityName Downstream Connection f'�:Pr�cipiiatior�,4ppHed ta:Facil�iy : ;::.<:: •: )` `t=vappraiivai Applied to Fa :ilit�::::::`:.:.: Facility Dimensions Length [€t].:;<; MA (It) 3tz ElieUtiue Oepth (tt) i! .Infiltration N1) 1i;�]0® Outlet 1 Outlet 2 Outlet 3 IKFMM X222=1 Auto Vault _ Quick Vau€t� 17. Fii gd.Width ForA.utct.Vault` .`: arilrlY ptmensian Diagfarn � Outlet Structure. Dat , {riser l7iameter [in) �� . "�€ Riser Type lFlat.7i Notre Type Orifice diameter Height Number (in) M 7.25 -tt] 3 1.876 ' -�H 4.7 -: VaultWiume at Riser Head (ac -R) .133 Show Vault Table Open Table i Initiel.Siage (ft)} .......... 410 Q VN}1M2D12 sawrantRrnlon File Edh View Help Sd--yAepan M, ' to r:: E7n i-; i ':Ij i O.W..._..___d._.-07 ........................................................... A v� � neo '----'-----'---- ---------'----'-'--------'- ]v ------- ------------------------- ' 4nna t� az _._ „-....._......_._..._. Q mjHF62052 $6twahlHMldA Fdr fdR Vrn Help summay Rgor! In5&61;x�ha The: Faai1ACY i'ASSIW A Plox a,cfsJ Pred-Hit PercrntasG PhRAJYaII;': 0.6570 7945 1934 69 P- o. 161A ano0.1613 2502 1595 67 Paas 0.3752 7VU 1869 71 1)0.9 0.1693 1929 1447 75 P4a9 0.1199 1709 1326 77 r- 0.1175 1503 1228 81 Pena 0, a217 }309 112E E6 Paae 0.1253 1178 1039 13a PAa9 9.1299 }P55 443 es P.- 0. a 40 aae0.1340 945 849 39 p4sa 0.1381 850 749 93 Pas. 0.3422 708 655 93 Paae 4.1555 Gl2 S5?. 95 Pasa 0.1504 594 5613 23 Fa11 . 0.1596 594 °90 90 Pana 5.1567 590 366 93 P.- 0 , 16V3 aa.0.1688 395 293 75 13". 0.1669 357 250 76 Paaa 0.1710 93.} 193 63 Paas 0.3751 217 173 62 Pasa 0.1'.92 245 153 6H Pa $3 0.33a1 224 349 66 Paaa ' 0.1675 245 19G 613 Pais O.i916 iBS 126 434 Paa. 0.1957 163 ?19 73 Pass 0.1942. 148 115 79 Paaa 6.2899 133 117 P,2 P.4. ❑.25a0 1161" 88 Pa.s D.2i21 111 95 E8 8093 6.2163 104 92 88 Pa - 01. 2 2 D-1 aas6.7204 95 87 91 13a99 a.2234 e6 85 98 Pae. 0.2286 79 89 10113a93 D.2327 76 71 101 Paaa .. A .331 u 99 i�s N§ Oi (i e i 0.19 i---------'-------------------`-------fid--------------'-----------' ------------------------------ 1 DEQ, TGE -4 10E-3 }C.2 ICE -1 1 1D .33 Fec rercnl Tirnc Exi]cr"rtin¢ Strwn Prdeclip 0u&In F16DuaDon Fk'Pmgaaa.y Water Cuais HIrk. �w WeL'and lrpeY VoAm.a uDIHepva P.charga Duration 1l..h gaPred- ..�f.. y�-. eloped Hechspe Md'galcd A..Ey-daiaxels Curpac[41UM . PDCY . J Ev :.,••._f CIC 1___� ABDalaiels 5 YGdr ... 4.2766 011697 +++' Q mjHF62052 $6twahlHMldA Fdr fdR Vrn Help summay Rgor! In5&61;x�ha The: Faai1ACY i'ASSIW A Plox a,cfsJ Pred-Hit PercrntasG PhRAJYaII;': 0.6570 7945 1934 69 P- o. 161A ano0.1613 2502 1595 67 Paas 0.3752 7VU 1869 71 1)0.9 0.1693 1929 1447 75 P4a9 0.1199 1709 1326 77 r- 0.1175 1503 1228 81 Pena 0, a217 }309 112E E6 Paae 0.1253 1178 1039 13a PAa9 9.1299 }P55 443 es P.- 0. a 40 aae0.1340 945 849 39 p4sa 0.1381 850 749 93 Pas. 0.3422 708 655 93 Paae 4.1555 Gl2 S5?. 95 Pasa 0.1504 594 5613 23 Fa11 . 0.1596 594 °90 90 Pana 5.1567 590 366 93 P.- 0 , 16V3 aa.0.1688 395 293 75 13". 0.1669 357 250 76 Paaa 0.1710 93.} 193 63 Paas 0.3751 217 173 62 Pasa 0.1'.92 245 153 6H Pa $3 0.33a1 224 349 66 Paaa ' 0.1675 245 19G 613 Pais O.i916 iBS 126 434 Paa. 0.1957 163 ?19 73 Pass 0.1942. 148 115 79 Paaa 6.2899 133 117 P,2 P.4. ❑.25a0 1161" 88 Pa.s D.2i21 111 95 E8 8093 6.2163 104 92 88 Pa - 01. 2 2 D-1 aas6.7204 95 87 91 13a99 a.2234 e6 85 98 Pae. 0.2286 79 89 10113a93 D.2327 76 71 101 Paaa .. A .331 u 99 i�s N§ Oi (i e i 41 ------------------------------ �A o3ysis :•� �••-� P1au Yreq¢3u3o3* n •ia01.11�3G1;e 3'm6ahiksty . 2 Year .. 5.1939 >). 1132 5 YGdr ... 4.2766 011697 +++' l5 Y.ar .. 5.:3399 5.2509 ' W 25 Year a Mov. 5.4257 9.2536 W W r6 '- to Year +• R.5H56 0.3402 ' 3 501 Annnal Pcal:a S...x;:rC• 1949 5.2992 0.1462 't �i 1950 x.2898 ❑.15 11 1951 0.2585 0, 15EA 1.9:12 0.1273 5.5752 3 1913 5.1529 5.0686 I 1954 0.1595 0.0896 Ut -_______________-__-- nos 1955 1956 9,16y8 0.1911 a.loOT 0.1099 u5 [ 2 5 10 23 30 w 70 SD � SS 98 99'11.51 1957 0.21A4 0.1267 Strluz, PrdectinrE)rratiwt 1JU 5wdi3n Fqw FrEquersy W,h.n n, ff�k *O, 1958 1959 0.3364 6.1277 9.0789 0.0734 WeBaM]rpul Vrk na� i]D Raprr[ Fcch.ru y[Tuadon ,••Rceher9e R� v�,aNx1 Fi�chu9a hEpipyrd,w� 19130 0.2373 0.1784 Aaa[yxe datasets Carrpet VJDhi 1961 4.1476 o.A"-1 1962 5.1012 0.0621 .t 196.3 0.1736 0.0987 19133 0.1960 5. 106'f 1966 0.1380 0.6172 19137 5.2964 0. 12552 .. .... .. .. .. .. . . .... .. .. .. ... 1968 5.1205 0.1206 Evap _.._ P(FC 4 POL 2 39139 197❑ 5,1554 5.1521 O. SSS7 0. 1033 A3Da[a5ale ••Ai FE.$lagsN Pie[ -p �..-. _....,--_._.... ,-. FWaAF&It. gF{B71iad ::'.:::'...�... 1971 19'12 5.1977 0.2382 D. 127E 0.1352 G. LopPcanm TSYall3.37fl'...:::-:::�. 1974 5.1x73 D.n7a6 0.2130 5.1087 !� Ctriwie:'.�::.'.:.::':..'.:".•:.":: 3975 9.1274 511345 o.i6o1 41 File Edit tier HEEp SummaTRepert I-1 r 0: Y ®a WE l A U 99 >._. K! rt1 WWHM2 0171 PROJECT REPORT Project Aflame: SatwantRenton Site Name: SE 2nd P1 Short Plat Site Address: 13609 156th Ave SE City : Renton Report Date: 5/1/2917 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 7.17 Version : 2013/11/20 Law Plow Threshold for POC l : 50 Percent of the 2 Year High Flow Threshold for PGC l: 50 year PREDEVELOPED LAND USE Name : onsite Bypass: No Groundwater: No Pervious Land use Acres 42 5tnQc 7remaanop fO.P .......... ......... ... ....... ...... . 10.0 Cumula5ve ilRy {Peetj 10ff1 2 Yonr = 2.9245 ----- t + S Year 3.4168 F++++ 18 Y— – 4.19 G9 25 Year 5.2430 50 Year 6.0646 140 Y— 6.9219 , 1.0 ..+ ...+..�_f . ....... ....... ........ .... ..... .. ... ... .. Annn.+3 Yeaka i 101 1949 3.9492 i 1950 2.5'722 7981 19'u2 1993 1.50H9 0.1 _._...._...�..�._�...............�_____ __----_________—___ 01 2955 2.$0.11 65 E 2 5 10 2p :0 SO T $S6 :q 55 SH S4 rJ33i 1956 2.8418 1957 2.2144 SUNS P'O.0j+ Qu:a lip [)V -S-ikrrKieazncy Waielgwfpi H7irogi aph 1959 3959 1960 F96F 2.17F4 . 1.7913 4.4945 2.4044 . _Yi rilord Erput Vo�m:rwi.f;7 Hrlod i{eriw9C pude+ EieC1i+Y9b Prcdvvehpo7 Rocha;ga hlRga[ed J Analyze da—t. Tvactl'!1,'7a 1952 1 O . 3U33 Ch—d. t SiRTE F?c&V&ped'.;'. I9fi3 2.1187 1964 2.003fl . 1965 2.1971 F96S 1.6352 1967 2.604 . .. .. .. ......... .. .. 1968 1.6694 1969 1.4644 Al C.4ueli fhw Sla9a pIR�1 1970 1.9006 Erm%tlt:2 1972 2.4726 _ —PdG1 ._..— .-...-�� F]uodP[eque;wy McOnd�: :::.�.�.:::.:; :� 2972 9.4941 Pessan Tp. lh!]777:: :::.:: F.973 1.73312 . 7974 2.A3.95 WWHM2 0171 PROJECT REPORT Project Aflame: SatwantRenton Site Name: SE 2nd P1 Short Plat Site Address: 13609 156th Ave SE City : Renton Report Date: 5/1/2917 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 7.17 Version : 2013/11/20 Law Plow Threshold for POC l : 50 Percent of the 2 Year High Flow Threshold for PGC l: 50 year PREDEVELOPED LAND USE Name : onsite Bypass: No Groundwater: No Pervious Land use Acres 42 C. Forest, Mod 1.67 Pervious Total 1.67 Impervious Land Use Acres Impervious Total 0 Basin Total 1.67 Element Flows To: Surface Interflow Channel. 1 Channel 1 Name : SE 2nd P1 Frontage Bypass: No Groundwater: No Pervious Land Use Acres C, Lawn, Mod. .105 Pervious Total 0.105 Impervious Land Use Acres ROADS MOD 0.229 Impervious Total 0.229 Basin Total 0.334 Element Flows To: Surface Intarf low Channel I Channel 1 Flame : 156 Ave SE Front Bypass: No Ground.Water! No Pervious Land Use Acres C, Lawn, Mod .095 Pervious 'Total 0.445 Impervious Land Use Acres ROADS MOD 0.005 Impervious 'Total 0.0€35 Groundwater Groundwater 43 Basin Total 0.05 Element Flows To: Surface Interflow Channel. Z Channel. 1 Name : Channel 1 Bottom Length: 10.00 ft. Bottom Width. 5.00 ff. Manning's n: 0.03 Channel bottom slope 1; 0.025 To 1 Channel Left aide slope 0: 3 To 1 Channel right side slope 2: 3 To 1 Dischar a structure Rimer Height: 0 ft. Riser Diameter: 0 in. Element FlowB To: Outlet 1 outlet 2 Channel Hydraulic 'Fable Groundwater Stage(ft) Area (ac ) Volume(ac-ft) Discharge(cfs) lnfilt(cfs) 0.0000 0.003. 0.000 0.000 0.000 0.0222 0.001 0.000 0.069 0.000 0.0444 0.001 0.000 0.220 0.000 0.0667 0.001 0.000 0.435 0.000 0.0889 0.001 0.000 0.706 0.000 0.1111 0.001 0.000 1.02.8 0.000 0.1333 0.001 0.000 1.400 0.000 0.1556 0.001 0.000 1.818 0.000 0.1778 0.001 0.000 2.282 01000 0.2000 0.001 0.000 2.791 0.000 0.2222 0.001 0.000 3.343 0.000 0.2444 0.001 0.0010 3.938 0.004 0.2667 0.001 0.000 4.576 0.000 0.2889 0.001 0.000 5.257 0.000 0.3111 0.001 0.000 5.979 0.040 10.3333 0.003. 0.000 6.743 0.040 0,3556 0.001 0.004 7.550 07.000 0.3778 0.001 0.000 8.398 0.000 0.4000 0.001 0.040 9.288 0.000 10.4222 0.001 0.000 10.22 0.000 0.4444 0.041 0.1000 11.19 0.000 0.4667 0.001 0.000 3.2.21 0,000 0.4889 0.001. 0.000 13.26 0.0100 0,5111 0 . 001 0.000 14.36 0. 000 0.5333 0.001 0.000 15.51 0.000 0.5556 0.001 4.000 16.69 4.040 0,5778 0.001 0.000 17.92 0.000 44 0.6000 0.002 0.000 19.20 0.000 0.6222 0.002 0.001. 20.51 0.000 0.6444 0.002 0.001 21,87 0,000 0,6667 0.002 0.001 23.28 0.000 0.6889 0.002 0.001 .24.73 0.000 0.7111 0.002 0.001 26.22 0.000 0,7333 0.002 01001 27,76 0.000 0.7556 0.002 0.001. 29,34 0.000 0.7778 0,002 01001 30,97 0.000 0.8000 0.002 0.001 32.64 0.000 0.8222 0,002 0.001 34.36 0.000 0.8444 0.002 0.001 36.13 0.000 0.8667 0.002 0.001 37.94 0,000 03.8889 0.002 0.001 39.81 0.000 0.9111 0.002 0.001 41.71 0.000 0,9333 0.002 0.001 43.67 0.000 0.9556 0.002 0.001 45.67 0.000 0.9778 0.002 0.001 47,73 0.000 1.0000 0.002 0,001 49.83 0.000 1.0222 0.002 0,001 51.98 0.000 1.0444 0,002 0.002 54.18 0.000 1.0657 0.002 0.002 56.43 0.000 1.0889 0.002 0.002 58.72 0,000 1.11.1.1 0.002 0.002 61.07 0.000 1,1333 0.002 0.002 63.47 0.000 1.1556 0.002 0.002 65.92 0.000 1.,1778 0.002 0.002 68.43 0.000 1,2000 0.002 0.002 70.98 0.000 1.2222 0.002 0.002 73,59 0,000 1.2444 0.002 0.002 75.24 0.000 1.26157 0.002 0.002 78.95 0.000 1.2889 0.002 0.002 81.72 0.000 1.3111 0.003 0.002 84.53 0.000 1.3333 0.003 0.002 87.41 0.000 1..3555 0,003 0,002 90.33 0.000 1.3778 0.003 0.002 93.31 0.000 3..4000 0.003 0.003 96.34 0.000 1,4222 0.003 0.003 99.43 0.000 1.4444 0.403 0.003 102.5 0,000 1.4667 0.003 0.003 105.7 0.000 1..4889 0.003 0,003 1.09 .0 0,000 1.5111 0.003 0.003 112.3 0.000 1.5333 0.003 0.003 115.7 0.000 1.. 5556 0.003 0.003 1.1.9 .1 01000 1.5778 0.003 0.003 122.6 01000 1.6000 0.003 0.003 126,1 0.000 1.6222 0.003 0.003 129.7 O A00 1..6444 ().003 0.003 133.4 0.000 1.&667 0.003 0.003 137.1 0.000 1.&889 0.003 0.003 140.9 0.000 1.7111 0.003 0,004 144.7 0.000 1.7333 0.003 0.004 148.6 0.000 1.7556 0,003 0.004 152,5 0.000 1..7778 0.003 0,004 1561.5 0.000 1.8000 0.003 0,004 160,6 ().000 1.8222 0.003 0.004 164.8 0.000 1.8444 0,003 0.004 1.69.0 0.000 1.8667 0.003 0.004 173.2 0.000 1.8889 0.003 0.004 177.5 0.000 45 1.9111 0,003 0.404 181.9 0.000 1.9333 0.003 0.004 185.4 0.000 1.9555 0.003 0.004 190.9 0.000 1.9778 0.003 0.005 195.4 0,000 2,0000 0.003 0.005 200.1 0.000 2.0222 0.004 03.005 204.8 0,000 M1T1GA'.E37 LAND USE Name : Onsite to vault Bypass: No Groundwater: No Pervious Land Use Acres C, Lawn„ Mod. .955 Pervious Total 0.955 Ism ervious Sand Use Acres ROAMS MOD 0.094 ROOF TOPS FLAT 0.359 Impervious Total 0.453 Basin Total 1.408 Element FlowB To: Surface Interflow vault 1 Vault 1 Groundwater name : Vault 1 Width : 36 ft.. Length : 74 ft. Depth: 7 ft. Discharge Structure Riser Height: 7 ft. Riser Diameter; 12 in. orifice 1 Diameter; 1.25 in. Elevation: 0 £t. orifice 2 Diameter: 1.5 in. Elevation; 3.6 ft-. Orifice 3 Diameter; 1.875 in. Elevation: 4.7 ft. Element Flows To: Outlet 1 Outlet 2 Channel 1 Vault Hydraulic 'Table Stage(ft) Area(ac) Volume(ac-ft) Discharge(cts) Infilt(cfa) 0.0000 0.061 0.000 0.000 0.000 0.0778 0,061 0.004 0.0711 0.000 46 0.1556 0.061 0.009 0.016 0.000 0,2333 0.061 4 . 01.4 0.019 0.000 0.31.11 0.061 0.019 0.022 0.000 0.3889 0.061 0,023 0.025 0.000 0.4667 0.061 0.028 0.028 0.000 0.5444 0.061 0.033 0.034 0.000 0.-6222. 0.061 0.038 0.032 0.400 0.7000 0.061 0,042 0.034 0.000 0.7778 0.061 0,047 0.036 0.000 0,8556 0.0761 0 . 052 0.038 07 . 000 0.9333 0,061 0.057 0.039 0,000 1.Cill 01,061 0.061 0.041 0.000 1..0889 0.061 0.066 0.042 0.000 1.1.667 0.061 0.071 0.044 0.000 1.2444 0.061. 0.076 0.045 0.000 1.3222 0.061 0.080 0.047 0.000 1..4000 0.061 0.085 0.046 0.000 1.4778 0.061 01090 0.049 0,000 1.5556 0.061. 0.495 4.051 0.000 1.6333 0.061 0.099 0.052 0.000 1.7111 0.061 0.104 0.053 0.000 1,7889 0.061 0,109 0.054 0.000 1.8667 0.061 0.114 0.056 0.000 1.9444 0.061 0.11.8 0.057 0.000 2.0222 0,061 0.123 0.058 0.000 2.1000 0.061 01128 0.059 4.000 2.1778 07.061 0.133 0.0760 0.000 2.2556 07.061. 0.137 0.061 0.000 2.3333 0,061 0,142 0.062 0.040 2.4111 0.061 0.147 0.063 0.000 2.4889 0.061 0.152 €3.064 0.000 2.5667 0.061 0.157 0.065 0.000 2.6444 0.061 0.161 0.066 0.0001 2.72.22 0.061. 0.1.66 0.067 0.0003 2.8000 0.061 0,171 01068 0,00€3 2.8778 0.061 0.176 0.069 0.000 2.9556 0.061. 0.1.80 0.070 0.000 3.0333 0.061 07.185 0.071 0.000 3.1111 0.061 0.190 0.072 0.000 3.1889 0.061 0.195 0.0'73 0.000 3.2667 03.063. 0.199 0.074 0.000 3.3444 4.063 0.204 0.075 0.000 3.4222 4.061 0.209 0.075 0.000 3.5000 0,0)61 0,214 0.076 0.000 3,5778 0,0)67. 0.218 0.077 0.000 3,6556 0.061 0.223 0.092 0.000 3.7333 0.061 0.228 0,1007 0.000 3.81.11 0.061 0.233 0.107 0.000 3.8889 0.061 0.237 0.112 0.000 3.9667 0.061 0.242 0.117 0.000 4.0444 0.061 0.247 0.121 0.000 4.1222 0.061 0.252 4.1.26 0.000 4.2000 01061 0,256 0,129 0.000 4,2778 01051 0,251 0,133 0.000 4,3556 0.061 0.266 07.137 4.000 4.4333 0.061. 0.271. 01.1.40 0.0070 4.51.1.1 0.061 0.275 0.143 0.400 4.5889 0.061 0.280 0.146 0.000 4.6667 0.061. 0.285 0,1.49 0,000 47 4.7444 0.061 0.290 0.1."72 0.000 4.8222 0.061. 4.294 4.187 0.000 4.9004 0.061. 4.299 0.199 0.000 4.9778 0.061 0.304 4.209 0.000 5.0556 0.061 0.309 4.218 0.000 5.1.333 4.061. 0.313 0.226 0.000 5.2111 0.051 0,318 0.234 0.000 5.2889 0.061 0,323 0.242 0.000 5.3667 0.061. 0.328 0.249 0.000 5.4444 4.061 0.333 0.255 0.000 5.5222 0.061 0.337 -0.262 4.000 5.6000 0.061 0.342 0,268 0.000 5.6778 0.061. 0.347 !3.274 0.000 5.7556 ❑.061 0.352 0.280 4.000 5.8333 0.061 0.356 0.285 0.440 5.91.11 0.061. 0.361 0.291 0.000 5.9889 0.061 0.366 0,296 0.000 6.0667 0.061 0.371 0,301 0.000 6.:€.444 0.061. 0.375 0.307 0.000 6.2222 0.061 0,380 0.312 0.000 6.3040 0,061 0.385 0.316 0.000 6.3778 0.061 0.390 0.321 0.000 6.4556 0.061 0.394 0.326 0.000 6.5333 0.1761 0.399 0.331 0.000 6.6111 0.061 0.404 0.335 0.000 6.6889 01061. 0.409 0.340 0.000 6.7667 0,061 0.413 0.344 0,00(3 6.8444 0.061 0.41.8 0.349 0.000 6.9222 0.061. 0.423 0.353 0.000 7.0000 0.061 0.428 0.357 0.000 7.4778 0.061 0.432 0.573 0.000 "7.3.556 0.000 0.000 0.963 0.000 Name : onsite Dispersed Bypass: No GroundWater: Na Pervious Land Use C, Lawn, Mod Pexvious Total Tmnervious Land Use ROOF TOPS FLAT Impervious Total Basin Total Element Flaws To: Surface Channel 1 Acres .233 0.233 Acres 0.029 0.029 0.252 Interflow Channel 1 Groundwater 49 Name : SE 2nd PI Front Bypass: No Groundwater: No Pervious Land Use Acres C, Lawn, Mod .083 Pervious Total 0.083 Impervious Land Use Acres ROADS MOD _ 0.251 Impervious Total 0.251 Basin Total 0.334 Element Flows To: Surface Interflow Vault 1 Vault 1 name : 1.5 -6th AVS, SE F.roz:t Bypass: No Groundwater: No Pervious Land Use Acres C, Lawn, Mod .03 Pervious Total 0.03 Impervious nand Use Acres ROADS MOD 0.02 Impervious Total 0.02 Basin Total 0.05 Element flows TO: surface Interflow Channel 1 Channel 1 Name : Channel 1 Bottom Length; 1.0.00 ft. Bottom width: 5.043 ft. Mannincg's n: 0.03 Channel bottom slope 1: 0.025 To 1 Channel Left side slope 0: 3 To I Groundwater Groundwater 49 Channel sight side slope 2: 3 T❑ 1 Discharge Structure Riser Height: 0 it•. Riser Diameter: 0 in. Element Flows To: Outlet 1 Outlet 2 Channel Hydraulic Table Stage(ft) Area (ac) Volcune(ac-ft) Discharge(cts) Snfilt(cfs) 0.0000 0.001 0.000 0.000 0.000 0.0222 0.001 0.000 0.069 0.000 0.0444 0.001 0.000 0.220 0.000 0.0667 0.001 0.000 0.435 0.000 0.0885 0.001 0.000 0.706 0.000 0.1111 0.001 0.000 1.028 0.000 0.1333 0.001 0.000 1.400 0.000 0.1556 0.001 0.000 1.818 0.000 0.1778 0.001 0.000 2,282 01000 0.2000 0.001 0.000 2.791 0.000 0.2222 0.001 0.000 3.343 0.000 0.2444 0.001 0.000 3.938 0.000 0.2667 0.001 0.000 4.576 0.000 0.2889 0.001 0.000 5.257 0.000 0.3111 0.001 0.000 5.979 0.000 0.3333 0.001 0.000 6.743 0.000 0.3556 0.001 O.ODO 7.550 0.000 0,3778 0.001 0.000 8.398 0.000 0.4000 0.001 0.000 9.288 0.000 0.42.22 0.001 0.000 10.22 0.000 0.4444 4.001 0.000 11.19 0.000 0.466'1 0.001 0.000 12.21 0.000 0.4889 0,001 0.000 13.26 0.000 0.5111 0.001 0.000 14.36 0.000 0.5333 0.001 0.000 15.51 0.000 0.5556 0,003. 01000 16.69 0.000 0,5778 0.001 0.000 17.92 0.000 016000 0.002 0.000 19.20 0.000 0.6222 0.002 0.001. 20.51 0.000 0.6444 0.002 0,001 21.87 0.000 0.6667 0.002 0.001 23.28 0.000 0.6889 0.002 0.001 24.73 0.000 0.7111 0.002 0.001 25.22 O.0OO 0.7333 0.002 0.001 27.76 0.000 0.7556 0,002 0.001 29.34 0.000 0.7778 0,002 0,001 30.97 0.000 0.8000 0.002 0.001 32.64 0.000 0.8222 0.002 0.001 34.36 0.000 0.8444 0.002 0.001 36.13 9.000 0.8667 0.002 0.001 37.94 0.000 0.8889 0.002 0.001 39.81 0.000 0.9111 0.002 0.001 41.71 0.000 0.9333 0.002 0.001 43.67 0.000 0.9556 0.002 0.001 45,67 0.000 0.9778 0.002 0.001 47.73 0.000 50 1.0000 0.002 0.001 49.83 0.000 1.0222 0.002. 0.001. 51.98 0.000 1.0444 0.002 0.002 54.18 0.000 1.0667 0.002 0.002 56.43 0.000 1.0889 0.002 0.002 58.72 0.000 1.1111 0.002 0.002 61.07 0.000 1.1333 0.002 0.002 63.47 0.000 1.1556 0.002 0.002 65.92 0.000 1,1778 0.002 0.002 68.43 0.000 1.2000 0.002 0.002 70.98 0.000 1.2222 0.002 0.002 73.59 0.000 1.2444 0.002 0.002 76.24 0.000 1.2667 0.002 0.002 78.95 0.000 1.2889 0.002 0.002 81.72 0.000 1.3111 0.003 0.002 84.53 0.000 1.3333 0.003 0.002 87.41 0.000 1.3556 0.003 0,002 90,33 0.000 1.3778 0.003 0.002 93.31 0.000 1.4000 0.003 0.003 96.34 0.000 1.4222 0.003 0.003 99.43 0.000 1.4444 0.003 0.003 102.5 0,000 1.4657 0.003 0.003 105.7 0.000 1.4889 0.003 0.003 109.0 0.000 1.5111 0.003 0.003 112.3 0,000 1.5333 0.003 0.003 115.7 0.000 1.5556 0.003 0.003 119.1 0.000 1.5778 0.003 0.003 122.6 0.000 1.6000 0.003 0.003 126.1 0.000 1.6222 0.003 0.003 129.7 0.000 1.6444 0.003 0.003 133.4 0.000 1.6567 0.003 0.003 137.1 0.000 1.6889 0.003 0.003 140.9 0.000 1.7111 0.003 0.004 144.7 0.000 4.7333 0.003 0.004 148.6 0.000 1.7556 0.003 0.004 152.5 0.000 1..7778 0,003 0,004 156,5 0,000 1.8000 0.003 0.004 160.6 0.000 1.8222 0.003 0.004 164.8 0.000 1.8444 0.003 0.004 169.0 0.000 1.8667 0.003 0.004 173.2 0.000 1.8889 0.003 0.004 177.5 0.000 1.9111 0.003 0.004 181.9 0.000 1.9333 0.003 0.004 185.4 0.000 1.9556 0.043 0.004 190.9 0.000 1.9778 0.003 0.005 195.4 0.000 2.0000 0.003 0.005 200.1 0.D00 2.0222 0.004 0.005 204.8 0.000 ANALYSIS RESULTS stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.82 51 Total impervious Area:4.234 Litigated Landuse Totals for PDC #1 Total Pervious Area:1.301 Total Impervious Area:0.753 Flour Frequency Return Periods for Return Period Flow (cfs) 2 year 0.193946 5 year 0,276802 10 year 0.339937 25 year 0.4297 50 year 0.504201 100 year 0.585572 Predeveloped. POC #1 Flow Frequency Return Periods for Mitigated.. Return Period Flow(cfs) 2 year 0.113206 5 year 0.163253 10 year 0.200891 25 year 0.253786 50 year 0.297213 100 year 0.344213 Stream Protection Duration ,Annual Peaks for Predeveloped and Mitigated. Year Predeveloped Mitigated 1949 0.299 0.146 1950 0.270 0.151 1951 0.209 0.3.84 1952 0,127 0.075 1953 0.103 0.059 1954 0.158 0.090 1.955 0.'1,54 01101 :1956 0.191 0.105 1957 0.211 0.7.27 1958 0.1.37 0.079 1959 0.128 0.075 1960 0.238 0.179 1961 0.1.68 0.105 1952 0.101 0.052 1953 0.174 0.099 1964 0.180 0.101 3.955 0.196 0 ,:107 1.966 0.138 0,077 19&7 0.297 0.154 1968 0.220 0.:1.23. 1969 0.165 0.117 1970 0.182 0.103 1971 01198 0 .3.27 1972 0.238 0.135 1973 (3 . 117 0. 0'75 1974 0.213 0.109 1975 0,227 0,134 1976 0.181 0.100 1977 0.:1.44 0.075 POC #1 PoC #1 52 1.9'78 0.1.87 0.094 1979 0.193 0.076 1980 0.429 0.1.75 1981 0.172 0.107 1982 0.311 0.239 1983 0.184 0.102 1984 0 , 3.35 0,073 19$5 13.138 0.100 1985 0.215 0.126 1987 O.20'7 0.142 1988 0.112 0.067 1989 0.169 0.060 1990 0.596 0.254 1991 0.376 0,203 1992 0.164 0.089 1993 0.131 0.073 1.994 0.11)2 0.055 1995 0.150 0.09& 1996 0.347 0.213 1997 0.230 0.1.77 1998 0.1.83 0.1108 1999 0.430 0.194 2000 0.179 0.1010 2001 0.156 0.086 2002 0,239 0.164 2003 0.298 0.128 2004 0.344 0.284 2005 0.184 0.115 2006 0.178 0.108 2007 0.498 0.290 2008 0.447 0.343 2009 0.255 0.150 Stream Protection Duration Ranked .Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.5958 0.3434 2 0.4981 0.2898 3 0.4469 0.2845 4 0.4296 0.2541 5 0.4290 0.2388 6 €3.3761 0,2127 7 0,3473 4.2034 8 0,3443 4.1936 9 0.3106 0.1,944 10 0.2992 0.1789 11 0,2978 0.1765 12 0.2969 0.1751. 13 0.2698 0.1638 1.4 0.2546 0.1542 15 0.2390 0.157.0 16 0,2362 0.1503 1.7 0.2-375 4.1462 18 0.2304 0.141.7 19 0.2274 0,1352 20 0,2205 0.1345 21 0.2154 0.1.280 22 0,2130 0.1274 53 23 0.2114 0.1267 24 0.2085 0.1264 25 6.2069 0.1206 26 0.1977 0,:1.1.67 27 0.1964 0,1151 28 0.1931 0.1687 29 0.1911 0.1.079 30 0.1871. 0,1076 31 0.1841 0.1075 32 0.1839 03.1067 33 0.1832 0.1055 34 0.1821 0,1054 35 0.1810 0.1033 36 0.1798 0.1023 37 0.1.793 0.1009 38 0.1784 0.1007 39 0.17112 0.1061 40 0.1'7].7 Q.:1.001 41 0.1693 0.0996 42 0.1676 0.0987 43 0.1654 0.0961 44 0.1639 0.0940 45 0,1638 0.0895 46 0.1585 0.0890 47 0.1561 0,0860 48 0,1498 0.0788 49 a . 1437 0 . 0"772 50 0 . 1.380 0,0764 51 0.1377 0.0752 52 0,1369 03.4750 53 0.1348 0.0746 54 0.7.33.2 0.0746 55 0.1277 0.6732 56 0.1273 0.0725 57 0.1:[.73 0.0686 58 0.1116 0.0670 59 0.1029 0.0621. 60 0.1024 0.0605 61 0.1012 6.13548 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Fjow(cfs) Predev Mit Percentage Pass/Fail 0.0970 2945 1934 65 Pass 0.1011 2502 1695 67 Pass 0.1052 2182 1.564 71 Pass 0,1093 1929 1447 75 Pass 0,1134 17€33 1324 77 Pass 0.1175 :.503 1228 81 -Vass 0.1217 1309 1128 85 Pass 0.1258 1178 1039 88 Pass 0.1299 1055 943 89 Pass 0.1.340 945 849 89 Pass 0.1381 800 749 93 Pass 54 0,1422 708 665 93 Pass 0.14.63 612 582 95 Pass 0.1504 544 506 93 Pass 0.1546 484 440 90 Pass 0.1587 440 366 83 Pas: 0.1628 396 .298 75 Pass 0.1669 357 250 70 Pass 0.1710 314 198 63 Pass 0.1751. 277 1.73 62 Pass 0.1792 245 1.54 62 Pass 0.1834 224 149 66 Pass 0.1875 203 136 66 Pass 0.191.6 185 128 69 Pass 0.1957 163 119 73 Pass 0.1998 146 116 79 Pass 0,2039 134 110 82 mass 0 , 2084 11.6 i.Q3 88 Pass 0.2121 ill 98 88 Pass 0.21.63 104 92 88 Pass 0.2204 95 87 91 Pass 0.2245 86 85 98 Pass 0.2286 79 80 101 Pass- ass0.2327 0.2327 76 77 101 Pass 0.2368 70 71. 101 Pass 0.2409 60 64 106 Pass 0.2451 57 58 101 Pass 0,2492 51 51 100 Pass 0.2533 47 48 102 Pass 0.2574 45 42 93 Pass 0.2615 40 31 77 Pass 0.2656 39 24 61 Pass 0.2697 36 17 47 Pass 0.2738 33 12 36 Pass 0.2780 32 9 28 pass 0.2821 30 8 26 Pass 0.2862 29 5 17 Vass 0.2903 29 4 13 Pass 0.2944 29 3 10 Pass 0.2985 25 2 8 Pass 0.3026 23 2 8 Pass 0.3068 23 2 8 Pass 3.3109 22 2 9 Pass 0.3150 20 2 10 bass 0.3191 17 1 5 Pass 0,3232 17 1 5 Pass 0.3273 3.4 1 -7 Pass 0.3314 14 1 7 Pass 0,3356 14 1 7 Pass 0.3397 3.4 1 7 Pass 0.3438 14 1 7 Pass 0,3479 12 0 0 mass 0.3520 13 0 0 Pass 0.3561. 11 0 0 Pass 0.3602 10 0 0 Pass 0.3643 10 0 0 Pass 0.3685 1.0 0 0 Pass 0.3726 10 0 0 Pass 0.3']&7 9 a 0 Dass 0.3808 8 0 0 Pass 55 0,3849 S 0 0 Pass 0.3890 8 0 0 Pass 0.3931. 7 0 0 Pass 0.3973 7 0 0 Pass 0.4014 7 0 0 Pars 0.4055 7 0 0 Pass 0.4096 7 0 0 Pass 0.4137 7 0 0 Pass 0.4:1.79 7 0 0 Pass 0.4219 7 0 0 Pass 0.4260 7 0 0 Pass 0.4302 5 0 0 Pass 0.4343 5 0 0 Pass 0.4384 5 0 0 Pass 0.4425 5 0 0 Paas 0.4466 5 0 0 Pass 0.4507 4 0 0 Pass Q.4548 4 0 0 Pass 0.4590 3 0 0 Pass ().4631 3 0 0 Pass 0,4672 3 0 0 Pass 0.4713 3 0 0 Pass 0.4754 3 0 0 Pass 0,4795 3 0 0 Pass 0.4836 3 0 fl Pass 0.4877 3 0 0 Pass 0,4919 2 Cl 0 Pass 0,4960 2 0 0 Pass 0.5001 1. 0 0 Pass 0.5042 1. 0 0 Pass Water Quality BMP Plow and Volume for POC #1 On-line facility volume: 9,0563 acre-feet Ora -line facility target flow: 0.0284 ofa. Adjusted for 15 mica: 0.0284 afs. off -lime facility target flow: 0.0189 afs. Adju.8ted for 15 inin: 0.0189 c£g. LID Report LID Technique Used for Total Volumn Volumn Infiltration Cumul.atiae Percent Water Quality Percezit Comment Treatment? Needs Through Volumn 'Volumn Volumn Water Quality Treatment: Facility (ac -ft) Infiltration infiltrated Treated (ac -ft) (ac - ft Credit Channel 1 POC N 255.18 f T ^T N 0.00 Vault 1 N 221.44 Id 0,00 Total Volume Infiltrated 476.62 0.00 0.00 0.00 0.03 0t No Treat. Credit Compliance with LID Standard S Duration Analysis Result = Failed 56 Flow Frequency Return Return Period 2 year 5 year 10 year 25 year 50 year 140 year Flaw Frequency Return Return Period 2 year 5 year 10 year 25 year 50 year 100 year Periods for Predeveloped. POC #1 Flow(cfs) 0.193946 ❑.275802 0.339937 0.4297 0,504203, 0,585572 Periods for Mitigated. POC #1 Flow(Cfs) 0.113206 0.163253 0.200891 0.253786 0.297213 0. 3442:1.3 Part -E Water Quality System Total new plus replaced pollution generating impervious area is less than 5,000 square feet, no water quality treatment facility is required. All onsite driveways are treated by pervious concrete pavement Flow control BMP and can be consider treated. For offsite improvements total pollution generating impervious area is reduced and no new pervious area is created, no mitigation is required. 57 V. Conveyance System Analysis and Desi n Conveyance system calculation will be provided at the phase of construction design. V1. Special Reports and Studies Special Reports related to this project: Geotechnical Report. Limited Stormwater & Geologic Hazard Evaluation prepared by Cobalt Geosciences, August 22, 2016 - updated April 12, 2017. • Arborist Report. Greenforest Incorporated, April 14, 2017 59 V1. Other Permits Water Service through Ding County Water District #90 Sewer Service through City of Renton Right -of -Way permits through City of Renton Franchised utilities (power, cable, gas, etc.) through individual utility purveyors NPDES Permit Through WA State Department of Ecology 60 Vill. CSV PPP Analysis and C esi n ESC Plan Analysis and Design (Part A) TEMPORARY EROSION AND SEDIMENT CONTROL 1. The grading for this project is limited to the onsite improvement and offsite frontage improvement. Temporary Erosion and Sedimentation Control will be provided by utilizing BMPs selected from the 2017 Renton Surface Water Design Manual. These BMPS will likely include, but are not necessarily limited to construction entrance for traffic stabilization, sift fencing for parameter protection, plastic sheeting of stockpiles, straw mulch, hydra -seeding of exposed areas, catch basin protection, etc. All new impervious areas and new pervious areas will be treated by a detention vault for Duration flow control (forest existing condition). At the beginning of the construction, construction entrance and silt fence along the grading limit will be installed. Then, combined detention/wet vault will be installed. Temporary erosion and sediment control facilities will be maintained during construction period and will be removed after construction is finished. Temporary erosion and sediment control plan, notes and details to be provided at construction plan stage. A Stormwater Pollution Prevention and Spill (SWPPS) plan will also be provided at construction plan stage. 2. The site is sloped, no sensitive area exists onsite. No special measure is proposed. Temporary sediment trap sizing: Qty using WNHM method with 15 -minute time step: Flow Frequency Return Periods for Mitigated. PCC #1 (Before detention) Return Period Flow(CfS) 2 year 0.419887 5 year 10 year 25 year 50 year 100 year 0 . 591.:7.57 0.712288 0.873986 A..000687 1,132724 Qty = 0.42 cfs Required surface area = 2080 * Q2y = 2080 * 0.42 = 874 sf. The proposed temporary sediment trap is located at the northwest corner of the site. A temporary overflow path is provided to over flow to the existing 12" storm that runs along SE 2nd Place. EROSION AND SEDIMENT CONTROL STANDARDS: ESC measures shall be applied and maintained to prevent, to the maximum extent practicable, the transport of sediment from the project site to downstream drainage systems or surface waters. This performance is intended to be achieved through proper 61 selection, installation, and operation of the above ESC measures as detailed in the ESC Standard (detached Appendix D) and approved by the City of Renton. PERMANENT EROSION AND SEDIMENT CONTROL For Permanent Erosion and Sedimentation Control, driveways and walkways will be paved. Landscape areas will be covered with grass, trees and ground covers. All onsite new impervious areas and new pervious areas will be treated by the detention vault for Flow control (Duration, forest existing condition). 62 STORMWATER POLLUTION PREVENTION AND SPILL (SWPPS) PLAN (Part R) 63 NSC. Bond Quantities Facilit Summaries and Declaration of Covenant 64 X. Operations and Maintenance Manual The onsite storm facilities will be maintained by the property owner and manager. 65