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HomeMy WebLinkAbout2120488.1 ., L■ Technical Information Report FREPARED FOR: Greene-Gasaway Architects, PLLC PO Box 4158 Federal Way, WA 98063-4158 PROJECT:' Honey Dew Elementary S:.hcol Portable Classroom 2012 — 2 800 Union Avenue NE Renton, WA 98059 r roject No. 2120488.10 PREPARED BY: Mason Skinner, r irProject Engineer REVIEWED SY.' William J. Fierst, PE Project Nlana,er Sean M. Comfort, PE Principal CITY OFRENTON RECEIVED DATE: JUL 2 7 2012 July 2012 BUILDING DIVISION Civil Engineers•Structural Engineers•Landscape Architects•Community Planners•Natural Resource Ecologists•Land Surveyors•Neighbors Technical Information Report PREPARED FOR: Greene-Gasaway Architects, PLLC PO Box 4158 Federal Way, WA 98063-4158 yQ„�pF h PROJECT: Honey Dew Elementary School Portable Classroom 2012 — 2 2 800 Union Avenue NE Renton, WA 98059 Project No. 2120488.10 PREPARED BY: I hereby state that this Small Project Mason Skinner, PE Drainage Review for Honey Dew Elementary School has been prepared by Project Engineer me or under my supervision, and meets the standard of care and expertise that is REVIEWED BY: usual and customary in this community for professional engineers. I understand that the City of Renton does not and will William J. Fierst, PE not assume liability for the sufficiency, Project Manager suitability, or performance of drainage facilities prepared by me. Sean M. Comfort, PE Principal DATE: July 2012 Table of Contents Section Page 1.0 Project Overview............................................................................................................1 2.0 Conditions and requirements summary.........................................................................2 2.1 Core Requirement #1 - Discharge at the Natural Location.............................................2 2.2 Core Requirement #2 - OfFsite Analysis........................................................................2 2.3 Core Requirement #3 - Flow Control............................................................................2 2.4 Core Requirement #4 -Conveyance System.................................................................2 2.5 Core Requirement #5 - Erosion and Sediment Control...................................................2 2.6 Core Requirement #6 - Maintenance and Operations ....................................................3 2.7 Core Requirement #7 - Financial Guarantees and Liability.............................................3 2.8 Core Requirement #8 - Water Quality..........................................................................3 2.9 Special Requirement #1 - Other Adopted Requirements................................................3 2.10 Special Requirement #2 - Flood Hazard Delineation......................................................3 2.11 Special Requirement #3 - Flood Protection Facilities......................................................3 2.12 Special Requirement #4 - Source Control .....................................................................3 2.13 Special Requirement #5 - Oil Control ...........................................................................3 3.0 Offsite analysis...............................................................................................................3 4.0 Flow Control and Water Quality Analysis and Design....................................................3 5.0 Conveyance System Analysis and Design.......................................................................3 6.0 Special Reports and Studies...........................................................................................4 7.0 Other Permits.................................................................................................................4 8.0 CSWPPP Analysis and Design.........................................................................................4 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant..............................4 10.0 Operations and Maintenance Manual.............................................................................4 Technical Information Report Q©O Q Honey Dew Elementary School Portable Classroom 2012—2 • Project No. 2120488.10 Appendices Appendix A Exhibits A-1................... Drainage Site Plan A-2................... Pre- and Post-Developed Site Flow Rates A-3................... NRCS Soils Report A-4 ................... City of Renton Flow Control Application Map Technical Information Report Honey Dew Elementary School Portable Classroom 2012—2 Project No. 2120488.10 1.0 PROJECT OVERVIEW The Portable Classroom 2012 — 2 project is proposing to install one double portable classroom at Honey Dew Elementary School located at 800 Union Avenue NE in Renton WA. This would result in the addition of 2,152 square feet (SF) of impervious surface, composed of one double portable class room (1,792 SF), landing ramp (240 SF), and sidewalk (120 SF). This project meets Full Drainage Review criteria per Section 1.1.2.3 of the 2009 King County Surface Water Design Manual(KCSWDM), as the project is adding more than 2,000 SF of new impervious surface, but is not subject to Small Project Drainage Review. Splash blocks will be used for basin dispersion as allowed in section C.2.4.2 of the 2009 KCSWDM: t F �'a ��i , r.z" t `Mt k .sfi.. qV ps aP A.Kennydale z # E N3QMSt ` EE M1�'aY jhl4 1 x , k � � Ma Creek � aY Ba fi"'� > a T ""Ca`ste.Cottksn Park � nxP lk m PROJECT # SITE . . k z n m " 'tia� '� �SEt$dtq ® Q,EINnrt Igaa9t Q . � € m = o v. �The LanElno '�pa'' n Rentcn � � n tr m #161h Bt ..HE 4ih SS - NOtHlmesl 4ttl Strc� N3rA 5t - 45t NE YvSt ,t NE 2n 3t RenRenton3, r,: :MUnw0H) d CeAer (jiver Pa'k a m Figure 1: Vicinity Map The new double portable classroom will include three downspout extensions with splash blocks for a total proposed roof area of 1,792 SF. Approximately 600 SF of roof area will drain to each downspout, thus meeting the one splash block per 700 SF of roof area requirement. A minimum 50-foot existing vegetated flow path segment is provided for each splash block, and thus exceeds the 50-foot minimum requirement. Roof and site runoff will flow overland, east through a grass lawn, towards existing play fields. Onsite erosion and sediment control measures, such as protection of existing stormwater inlets, will be implemented during construction. See Appendix A.1 for Drainage Site Plan, and Appendix A.3 for NRCS Soils Report. With the completion of this project, there will be three double portable classrooms on the Honey Dew Elementary site. This is only 75% of the four double portable classrooms that were included in the Site Plan Modification/SEPA Lead Agency/SEPA Exempt letter filed with the City on March 25, 2004. Technical Information Report (BM(30 Honey Dew Elementary School Portable Classroom 2012—2 1 Project No. 2120488.10 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Core Requirement #1 - Discharge at the Natural Location Stormwater roof runoff from the portable will be discharged from the roof with extended downspouts and will outfall to splash blocks that will flow overland to a large play field. Surface and stormwater runoff from the proposed development will continue to be discharged at the natural location, and thus will not adversely affect downstream properties or drainage systems. The 100-year peak discharge for the developed condition will remain less than 0.20 cubic feet per second (CFS), and therefore may be discharged to a rock pad or any other system that disperses flow, per Section 1.2.1 of the 2009 KCSWDM. See pre-developed forest and developed peak flow rates in Appendix A-2. 2.2 Core Requirement #2 - Offsite Analysis Stormwater runoff from the 2,152 SF of additional impervious area will be dispersed with a flow control Best Management Practice (BMP) and will flow across a grassy flow path before being discharged from the site. Stormwater runoff from the additional impervious area will likely infiltrate into the soils at the field and not discharge from the site. The proposed development will result in an increase in peak flow of 0.038 CFS during the 100-year storm event that will discharge downstream of our site.This increase in stormwater runoff is not deemed significant, and a downstream analysis will not be conducted. 2.3 Core Requirement #3 - Flow Control Developed 100-year peak flow rates for the proposed site will result in less than a 0.1 CFS increase from the 100-year existing peak flow conditions. No flow control will be required for the proposed development, as the project meets flow control exemption 2 for Flow Control Duration Standard Areas in Section 1.2.3.1.B of the City of Renton 2009 Surface Water Design Manual Amendment. The site is located in a Flow Control Duration Standard (Forested Conditions) area, per the City of Renton Flow Control Application Map located in Appendix A.4. 2.4 Core Requirement #4 - Conveyance System No new conveyance systems are proposed for this project. The existing onsite conveyance system will not see a significant change in flow characteristics, and need not be analyzed for conveyance capacity. 2.5 Core Requirement #5 - Erosion and Sediment Control Onsite land disturbance will be very minimal and will consist of clearing of existing grasses at the portable and demolition of approximately 80 SF of concrete mow strip. Erosion and sediment control will be provided with the use of a catch basin insert, which will prevent any sediment from entering the downstream conveyance system. Technical Information Report lomme Honey Dew Elementary School Portable Classroom 2012—2 2 Project No. 2120488.10 2.6 Core Requirement #6 - Maintenance and Operations Maintenance and operation of all drainage facilities will be maintained by the owner. The project does not propose new drainage structures. 2.7 Core Requirement #7 - Financial Guarantees and Liability No flow control, water quality, conveyance, erosion control, or road drainage facilities are being proposed for this development; therefore, Core Requirement #7 does not apply to this development. 2.8 Core Requirement #8 - Water Quality No pollution generating surfaces are proposed as part of this development; therefore, Core Requirement #8 will not apply. 2.9 Special Requirement #1 - Other Adopted Requirements No adopted requirements apply to this project. 2.10 Special Requirement #2 - Flood Hazard Delineation The proposed project is not in or adjacent to the 100-year floodplain. 2.11 Special Requirement #3 - Flood Protection Facilities No flood protection facilities are required for this project. 2.12 Special Requirement #4 - Source Control No source controls are required for this project. 2.13 Special Requirement #5 - Oil Control The site does not meet high use criteria and is not subject to oil control measures. 3.0 OFFSITE ANALYSIS See Section 2.2 above for Core Requirement #2 Offsite Analysis. 4.0 FLOW CONTROL AND WATER QUALITY ANALYSIS AND DESIGN See Sections 2.3 and 2.8 above for Flow Control and Water Quality Analysis sections meeting Core Requirements #3 and #8. 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN - See Section 2.4 above for Core Requirement #4 Conveyance System. Technical Information Report omms Honey Dew Elementary School Portable Classroom 2012—2 3 Project No. 2120488.10 6.0 SPECIAL REPORTS AND STUDIES No Special Reports or Studies are required as part of this proposed development. 7.0 OTHER PERMITS No other permits are required as part of this proposed development per Section 2.3.1.1 of the 2009 KCSWDM. 8.0 CSWPPP ANALYSIS AND DESIGN No CSWPP is submitted with this TIR. 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT See Section 2.7 above for Core Requirement #7 Financial Guarantees and Liability. 10.0 OPERATIONS AND MAINTENANCE MANUAL No flow control and water quality facilities will be located on site which will require an Operations and Maintenance Manual. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared using procedures and practices within the standard accepted practices of the industry. AHBL, Inc. Mason Skinner, PE Project Engineer MS/lsk July 2012 Q:\2012\2120488\10_CIV\NON_CAD\REPORTS\20120723_Rpt_(TIR)_2120488.10_(HoneyDewES).dooc Technical Information Report 13MI00 Honey Dew Elementary School Portable Classroom 2012—2 4 Project No. 2120488.10 Appendix A Exhibits A-1 ..................Drainage Site Plan A-2 ..................Site Flow Rates A-3 ..................NRCS Soils Report A-4 ................... City of Renton Flow Control Application Map Technical Information Report Q©Q O Honey Dew Elementary School Portable Classroom 2012—2 Project No. 2120488.10 F— EX.STORM WATER 3 4 CATCH BASIN TVP 1 OVdpATH N ll`J 1 FL t WAT Za - � c III �'II YYY ... ...W X4WLIJ W ENL W EA M W O WATERMAIN 10, O EX.8"WATERMAIN r a OTYP 1 fl . ... __.. -__-.. ...-.. _- TT :-- - _ j (A - , : -f f i I LLI - ,�--_"EEX.FIRd HYDRANTco Q \ I EXISTING HONEY DEW J / — ELEMENTARY SCHOOL p If z A,r — - CONSTRUCTION KEYNOTES: W Ot I DOWNSPOUT EXTENSION WITH SPLASH BLOCK.SEE DETAIL 21 ON SHEET A4 OF THE HONEY DEW ELEMENTARY SCHOOL PORTABLE CLASSROOM 2012-2 DRAWINGS AND DETAIL 1 W l'- 2O OVERLAND FLOW PATH THRU VEGETATED GRASS -- --- L1.1 ! 03 PROVIDE CATCH BASIN INSERT 1_�_; 4 EXISTING STORM DRAIN PER HONEY DEW ELEMENTARY WATER PLAN ASBUILTS PERMIT NO.V07GDW EXISTING WATER LINE Z PERMIT NO PER HONEY DEW ELEMENTARY WATER PLAN ASBUILTS p —.— 6 PROPOSED PORTABLE,SEE DETAIL 20 ON SHEET A2 OF THE HONEY DEW ELEMENTARY N SCHOOL PORTABLE CLASSROOM 2012.2 DRAWINGS. AHB L NE 8TH...STREET s 07 EXISTING PORTABLE.SEE DETAIL 20 2-SHEET A2 OF THE HONEY DEW ELEMENTARY SCHOOL PORTABLE CLASSROOM 2012-2 DRAWINGS. GENERAL NOTES GRAPHIC SCALE 1 EXISTING TOPOGRAPHY GENERATED FROM LIDAR OBTAINED FROM PUGET SOUND 0 10 20 40 FEET FACE OF(E) (E)DS PORTABLE R VAIRES,3.5'MIN. VARIES,3.5'MIN. 1- = 20 FEBT FLOWPATH CONCRETE PROPOSED LANDCOVER AREAS GRASS(TYP.) MOW STRIP 1 DOUBLE PORTABLE CLASSROOM =1,792 SF LANDING RAMP -240 SF IDS EXTENSION SIDEWALKS =120 SF I SPLASH BLOCK r / \ \\\\ \\ TOTAL PROPOSED AREA =2,152 SF A.dYb� •�' v NCO _ FG APPRox.os //�\`\ \ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\� ChecYed for C. Dliance to City Standards SIONAL / ice\\ice\//� SPLASH BLOCK DETAIL SECTION A � ��� T A o O MA S,T A T T 98 03 1 e�m_ e� 2215 N 21 300 Street Suits 300,Temme,WA 98403 253.3832422 m WT TO�E m� ,®p",��'; 12W Sbdh Avenue,111620,S.W.,WA 98101 DESIGN SUBMITTAL AS NOTED CITY OF HONEY DEW ELEMENTARY SCHOOL JU 2012 S :'. ,.� LY.rcmon M.SKINNER PROTABLE CLASSROOM 2012-2 Y.SKINNER RENTON RENTON SCHOOL DISTRICT e� W 'a'W.FIERST Pic nning/Building/Public Works Dept. DRAINAGE SITE PLAN NO. REVISION BY DATE APPR g COMFORT 1 4, - NIININIIN14A Appendix A-2 Site Flow Rates Project: Honey Dew Elementary School Portable Classroom 2012—2 Project Number: 2120488.10 Date: July, 2012 Performed By: Mason J. Skinner, PE Reference: City of Renton Amendments to the 2009 King County Storm Water Design Manual King County Storm Water Design Manual 2009 Software Used: King County Runoff Time Series (KCRTS) Core Requirement#1—Discharge at the Natural Location Design Criteria: IF the 100-year peak discharge is less than or equal to 0.2 cfs under existing conditions and will remain less than or equal to 0.2 cfs under developed conditions,THEN the concentrated runoff may be discharged onto a rock pad or to any other system that serves to disperse flows. Assumptions: Areas used were disturbed portion of the site/lot. Existing lawn (Till Grass) = 0.06 acres Existing concrete mow strip (Impervious) =0.002 acres KCRTS OUTPUT Existing Peak Discharge: Land Use Summary ih Area Till Forest 0.00 acres Till Pasture 0.00 acres, Till Grass 0;06 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres 0Y :?Wetland 0.00 acres r Impervious 0.00 acres fi FTotal- Scale Factor: 1.00 15-Min Reduced i Edit Flow Paths Time Series: Honey_Dew_ExstTSF Compute Time Series Modify User Input j File for computed Time Series 1.TSF1 Technical Information Report Honey Dew Elementary School Appendix A-2 Flow Frequency Analysis Time Series File: honey_dew_exst.tsf Project Location: Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) CFS Period 0 . 007 4 2/09/01 12 : 45 10.030 1 100.00 0. 990 0. 004 7 1/05/02 15: 00 0 . 018 2 25. 00 0 . 960 0. 014 3 12/08/02 17 : 15 0 . 014 3 10 . 00 0 . 900 0.002 8 8/26/04 0 : 45 0 . 007 4 5. 00 0. 800 0 . 018 2 11/17/04 5: 00 0. 006 5 3 . 00 0 . 667 0. 006 5 1/18/06 15: 00 0 . 006 6 2 . 00 0 . 500 0. 006 6 11/24/06 1 : 00 0. 004 7 1 . 30 0 .231 0. 030 1 1/09/08 6: 30 0. 002 8 1 . 10 0. 091 Computed Peaks 0 . 026 50 . 00 0 . 980 Assumptions: Areas used were disturbed portion of the site/lot. Developed lawn (Till Grass)=0.0007 acres Developed roofs, ramps, and sidewalk(Impervious)=0.057 acres KCRTS OUTPUT Developed Peak Discharge: >lse A I Is 1 ON Area , Till F orelm 0.00 acres Till Pasture 0.00 acres a Till Grass 0.00 acres Outwash Forest 040 acres Outwash Pasture D.00 acres Outwssh Grass Q-90 acres WiAand 0A acres:. Impervious 0,06 acres Total 0.06 acres Scele Factor.. 100 15=�A,in Reduced oa+ s Time Spnes Honey_Dew Prop.TSFJI Compute Time Series aiiilodity User Input •Flle bi camRuted Time Series[.T,SFJ. Technical Information Report Honey Dew Elementary School Appendix A-2 Flow Frequency Analysis Time Series File: honey_dew_prop.tsf Project Location: Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) CFS Period 0. 027 6 8/27/01 18 : 00 10.068 1 100.00 0. 990 0 . 019 8 9/17/02 17 : 45 0 . 052 2 25. 00 0. 960 0 . 052 2 12/08/02 17 : 15 0 . 037 3 10. 00 0 . 900 0 . 022 7 8/23/04 14 : 30 0. 030 4 5. 00 0 . 800 0. 029 5 10/28/04 16: 00 0. 029 5 3. 00 0 . 667 0 . 030 4 10/27/05 10: 45 0 . 027 6 2 . 00 0. 500 0 . 037 3 10/25/06 22: 45 0. 022 7 1 . 30 0.231 0 . 068 1 1/09/08 6:30 0 .019 8 1. 10 0 . 091 Computed Peaks 0 . 062 50 . 00 0 . 980 Core Requirement#3-Flow Control Design Criteria: The facility requirement in Flow Control Duration Standard Matching Forested Site Conditions Areas is waived for any threshold discharge area in which there is no more than a 0.1-cfs difference in the sum of developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historic) site conditions 100-year peak flows for the same surface areas. Note:for the purposes of this calculation,target surfaces served by flow control BMPs per Appendix C may be modeled in accordance with the flow control BMP facility sizing credits in Table 1.2.3.0(p. 1-42). Assumptions: Areas used were disturbed portion of the site/lot. Historic(Till Forest) =0.06 acres Technical Information Report Honey Dew Elementary School Appendix A-2 KCRTS OUTPUT Historic Peak Discharge: Area.--i Till Forest 0.06 acres Till Pasture 0.00 acres Till Grassi 0.00 acres Outwash Forest, 0.00:crescres Outwas6 Pasturei 0.00 Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.00 acres -Total---i 0.06 acres.:. Scale Factor: 1.00 15-Min Reduced Time Series; oney_Dew HistTSF » Compute Time Series Modify User Input -- p J.File for computed Time Series T, Flow Frequency Analysis Time Series File: honey_dew_hist.tsf Project Location: Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) CFS Period 0 . 004 2 2/09/01 15: 45 10.006 1 100.00 0. 990 0 . 001 7 1/06/02 1: 15 0 . 004 2 25. 00 0. 960 0 . 003 3 3/06/03 18 : 45 0 . 003 3 10 . 00 0. 900 0 . 000 8 10/31/03 15: 00 0. 003 4 5. 00 0 . 800 0 . 002 6 1/05/05 7 : 00 0 .003 5 3. 00 0. 667 0 . 003 4 1/18/06 18 : 00 0 . 002 6 2 .00 0. 500 0 . 003 5 11/24/06 3 : 15 0. 001 7 1 . 30 0.231 0 . 006 1 1/09/08 9: 30 0. 000 8 1 . 10 0 .091 Computed Peaks 0 .005 50. 00 0. 980 Assumptions: Areas used were disturbed portion of the site/lot. Basic Dispersion credit: impervious modeled at 50% impervious and 50%grass Developed Lawn (Till Grass)=0.0007 acres Developed roofs, ramps, and sidewalk(Impervious) =0.057 acres modeled at .029 Impervious and .029 Till Grass Technical Information Report Honey Dew Elementary School Appendix A-2 KCRTS OUTPUT Developed Peak Discharge Using Basic Dispersion: Area Till Forest 0.00-acres Till Pasture 0.00 acres 7111 Grass 0.03 acres Out}vash Fares 0.00'scres Ouiwash'Pasture 0.00'acres Outwash Grass 0.01 acres Wetland 0.00acres Impervious 0.Q1 des Total OX acres Scale Factor: 1.00 15-Min Reduced d t Flow Pailis Time Series;.Honey_Dew_Dev.TSF >? Compute Time Series Modify lyserinput File for computed Time Series 1.TSF] Flow Frequency Analysis Time Series File: honey_dew_dev.tsf Project Location: Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0 . 013 6 8/27/01 18 : 00 0.048 1 100.00 0. 990 0 . 010 8 1/05/02 15: 00 0. 031 2 25.00 0 . 960 0 . 031 2 12/08/02 17 : 15 0. 020 3 10 . 00 0 . 900 0 . 011 7 8/26/04 0: 45 0. 019 4 5. 00 0 . 800 0 . 020 3 11/17/04 5: 00 0. 017 5 3. 00 0 . 667 0 . 017 5 10/27/05 10: 45 0. 013 6 2 . 00 0 . 500 0 . 019 4 10/25/06 22 : 45 0 . 011 7 1 . 30 0 .231 0 . 048 1 1/09/08 6: 30 0 . 010 8 1 . 10 0 . 091 Computed Peaks 0 . 042 50. 00 0. 980 Conclusion: The difference in the sum of developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historic)site conditions 100-year peak flows for the same surface areas is calculated at 0.038- cfs, which is below the 0.1-cfs threshold. Technical Information Report Honey Dew Elementary School Appendix A-2 Soil Map—King County Area,Wasnington (Honey Dew Elementary School) M N Appendix A-3 N 562900 562920 562940 562960 562980 563000 563020 563040 563060 563080 563100 563120 562140 47"29'49" A6AL 47'29'4f,' lull WL r .:.r .I .. 3 O � � O N N N O O m N N o o o o N 0 o N <D O cD N N O O S. a I O N r e 47'29'44" 47'29'44" 562900 562920 562940 562960 562980 563000 563020 563040 563060 563080 563100 563120 563140 Map Scale:11,180 rf printed on Astze(8.5"x 11")sheet. c m m N N Meters N ^ 0 15 30 60 90 /,\V Feet 0 50 100 200 300 Appendix A-3 USDA Natural Resources Web Soil Survey 7/23/2012 Conservation Service National Cooperative Soil Survey Page 1 of 3 Soil Map—King County Area,Washington (Honey Dew Elementary School) MAP LEGEND MAP INFORMATION Area of Interest(AOI) f Very Stony Spot Map Scale: 1:1,180 if printed on A size(8.5"X 11")sheet. 1 Area of Interest(AOI) V Wet Spot The soil surveys that comprise your AOI were mapped at 1:24,000. Soils Soil Map Units Other Warning: Soil Map may not be valid at this scale. Special Point Features Special Line Features Enlargement of maps beyond the scale of mapping can cause =�.� Blowout Gully- misunderstanding of the detail of mapping and accuracy of soil line . Short Steep Slope placement.The maps do not show the small areas of contrasting ® Borrow Pit soils that could have been shown at a more detailed scale. ,.. Other X Clay Spot ease rel y the bar scale on each ma sheet for accurate ma Political Features y on p p * Closed Depression O Cities measurements. X Gravel Pit Water Features Source of Map: Natural Resources Conservation Service Web Soil Survey URL: hftp://websoilsurvey.nres.usda.gov Gravelly Spot Streams and Canals Coordinate System: UTM Zone 1 ON NAD83 Landfill Transportation This product is generated from the USDA-NRCS certified data as of Lava Flow +++ Rails the version date(s)listed below. ,k, Marsh or swamp Interstate Highways Soil Survey Area: King County Area,Washington R Mine or Quarry US Routes Survey Area Data: Version 7,Jul 2,2012 p Miscellaneous Water Major Roads Date(s)aerial images were photographed: 7/24/2006 p Perennial Water Local Roads The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background ., Rock Outcrop imagery displayed on these maps.As a result,some minor shifting of map unit boundaries may be evident t 5aline Spot Sandy Spot Severely Eroded Spot Q Sinkhole �} Slide or Slip pf Sodic Spot Spoil Area Stony Spot Appendix A-3 USDA Natural Resources Web Soil Survey 7/23/2012 �� Conservation Service National Cooperative Soil Survey Page 2 of 3 Soil Map—King County Area,Washington Honey Dew Elementary School Map Unit Legend King County Area,Washington(WA633) Map Unit Symbol Map Unit Name Acres in AOI Percent of AO1 AgC Alderwood gravelly sandy loam,6 to 15 2.5 43.2% percent slopes AmC Arents,Alderwood material,6 to 15 percent 3.2 56.8% slopes Totals for Area of Interest 5.7 100.0% Appendix A-3 USDA Natural Resources Web Soil Survey 7/23/2012 am Conservation Service National Cooperative Soil Survey Page 3 of 3 � -� i T Flow Control Standards Peak Rate Flow Control Standard(Existing Site Conditions) Flow Control Duration Standard(Existing Site Conditions) MIN Flow Control Duration Standard(Forested Conditions) 1116— Renton City Limits Potential Annexation Area W �311% p 4 . • 1 c � T I ;iL OC�b TACO MA SEATTLE www.ahbI.com J 2215 North 30th Street 1200 6th Avenue Suite 300 Suite 1620 Tacoma,WA 98403-3350 Seattle,WA 98101-3123 253.383.2422 TEL 206.267.2425 TEL 253.383.2572 FAx 206.267.2429 FAx