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HomeMy WebLinkAbout03679 - Technical Information Report c � D s ) D. R. STRONG CONSULTING ENGINEERS WEI 1 (Yl2 o •"' Engineers .S■■ Surveyors II g'S W Landscape Architects 1 1 1 1 Full Service Engineering Since 1981 3Ce, 7a TECHNICAL INFORMATION REPORT (TIR) for WELMAN PLAT 18417 116th Ave SE - Renton,Washington ��g A. ,Q �Cr 'E OF nsy Of ca 3r ri 54-00 //OrV IONA I 1 I 40 DRS Project No. 12016 Renton File No. Owner/Applicant Harbour Homes LLC 1441 North 34th Street, Suite 200 Seattle, Washington 98103 Report Prepared by ,DS; D. R. STRONG Consulting Engineers, Inc. 10604 N.E. 38th Place, Suite 101 Kirkland WA 98033 (425) 827-3063 Report Issue Date 'G N.% _/0\1- N May 9, 2012 MPS CaQJ`�`O ©2012 D.R.STRONG Consulting Engineers Inc. TECHNICAL INFORMATION REPORT WELMAN PLAT TABLE OF CONTENTS SECTION I 1 Project Overview 1 Predeveloped Site Conditions 1 Developed Site Conditions 1 Natural Drainage System Functions 1 SECTION II 11 Conditions and Requirements Summary 11 SECTION III 13 Off-Site Analysis 13 SECTION IV 14 Flow Control and Water Quality Facility Analysis and Design 14 Existing Site Hydrology (Part A) 14 Pre-developed Hourly Time Step Modeling Input: 15 Pre-developed Hourly Time Step Modeling Output: 15 Developed Site Hydrology (Part B) 17 Developed Site Area Hydrology 17 Developed Hourly Time Step Modeling Input: 18 Developed Hourly Time Step Modeling Output. 18 Bypass Hourly Time Step Modeling Input. 19 Bypass Hourly Time Step Modeling Output: 19 Performance.Standards (Part C) 21 Flow Control System (Part D) 21 Flow Control BMP Selection 21 Flow Control Facility Design Output 22 Duration Analysis 27 Water Quality Treatment System (Part E) 28 SECTION V 30 Conveyance System Analysis and Design 30 Developed 15-Minute Time Step Modeling Input: 31 Developed 15-Minute Time Step Modeling Output: 31 Backwater Analysis 33 Backwater Table 33 BackWater Computer Program for Pipes 36 ©2012 D.R.STRONG Consulting Engineers Inc. Page i of ii Technical Information Report Welman Plat May 9,2012 SECTION VI 41 Special Reports and Studies 41 SECTION VII 42 Other Permits, Variances and Adjustments 42 SECTION VIII 43 ESC Plan Analysis and Design (Part A) 43 KCRTS Analysis for Sediment Trap 44 SWPPS Plan Design (Part B) 45 SECTION IX 46 Bond Quantities, Facility Summaries, and Declaration of Covenant 46 Stormwater Facility Summary Sheet 47 SECTION X 49 Operations and Maintenance Manual 49 APPENDICES 50 List of Figures Figure 1 TIR Worksheet 2 Figure 2 Vicinity Map 5 Figure 3 Drainage Basins, Subbasins, and Site Characteristics 6 Figure 4 Soils 7 Figure 5 Predevelopment Area Map 16 Figure 6 Post Development Area Map 20 Figure 7 Detention & Water Quality Facility Details 29 Figure 8 Backwater Analysis Map 35 Appendices Appendix A Bond Quantity Worksheet 51 Appendix B Offsite Analysis by Site Development Associates, LLC 52 ©2012 D.R.STRONG Consulting Engineers Inc. Page ii of ii Technical Information Report Welman Plat May 9,2012 SECTION I PROJECT OVERVIEW The subject site ("Site") is located at 18417 116th Ave SE in Renton, Washington. The applicant has gained approval to subdivide one existing parcel (Parcel Number 3223059033) into 25 lots for single-family detached residences, with the associated infrastructure and frontage improvements ("Project"). However, the current proposal would reduce this to 21 lots. The City of Renton ("City") annexed the Site in 2008. The property while located within the City is entitled to processing under the King County zoning and platting regulations. The Project is vested to the 2005 King County Surface Water Design Manual ("KCSWDM") and the 1993 King County Road Standards ("KCRS"). Drainage Adjustment L04V0085 was approved, allowing diversion of onsite flows to a single detention facility located in Tract "E". PREDEVELOPED SITE CONDITIONS Total Site area is approximately 3.24 ac. with a developable Project area of approximately 3.34 ac. The Parcel is currently developed with a single-family residence, garage, and carport. The Site is mostly residential lawn and landscaping with scattered trees. The majority of the Site slopes toward a Class 4 wetland located in the northwest portion of the parcel. This wetland drains offsite to the west into the Emerald Glen subdivision. All onsite areas are modeled as till forest (2.99 ac). Offsite areas are modeled as till pasture (0.14 ac.) and impervious (0.21 ac.). DEVELOPED SITE CONDITIONS The Project will create 21 lots with areas ranging from approximately 3,500 to 5,750 s.f. The Project area is approximately 3.34 ac. (includes minimal frontage improvements on 116th Avenue SE). Due to Site constraints, 0.10 ac. of backyard area modeled as till grass will bypass the detention facility. Post-developed impervious areas including rights-of-way, private access tracts, roofs, driveways and site frontage total approximately 2.20 ac. The remainder of the Site tributary to the detention facility will be modeled as till grass (0.97 ac.) and till pasture (0.06 ac.). Runoff will be collected and conveyed to the detention facility located in Tract "E" and discharged to the Class 4 wetland located in Tract "F" in the northwest corner of the Site. The facility will provide Level 2 Flow Control and Basic Water Quality treatment. NATURAL DRAINAGE SYSTEM FUNCTIONS A review of the SCS soils map for the area (see Figure 4, Soils) indicates Alderwood gravelly sandy loam with 0 to 6 percent slopes (AgB). Per the Manual, this soil type is classified as "Till" material. The SCS Soil series descriptions follow Figure 4. In evaluating the upstream area, we reviewed the Site Development Associates LLC offsite analysis and King County IMAP aerial topography and imagery. We have concluded that the upstream tributary area for the Site is negligible. The predeveloped Site is contained within one Threshold Discharge Area (TDA) and has three Natural Discharge Areas (NDA) that discharge to the northwest, southwest, and south. ©2012 D.R.STRONG Consulting Engineers Inc. 1 Welman Plat Technical Information Report Renton,Washington FIGURE 1 TIR WORKSHEET King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGINEER DESCRIPTION Project Owner: Project Name: Harbour Homes LLC Welman Plat Address/Phone: Location: 1441 North 34th Street, Suite 200 Township: 23 North Seattle, WA 98103 Range: 05 East (206) 315-8130 Section: 32 Project Engineer: Maher A. Joudi, P.E. D. R. STRONG Consulting Engineers Inc. Address/Phone: 10604 NE 38th Place, Suite 101 Kirkland WA 98033 (425) 827-3063 Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS APPLICATION Z Subdivision I I DFW HPA Shoreline Short Subdivision Management ® Clearing and Grading COE 404 Rockery n Commercial n DOE Dam Safety I Structural Vault n Other: FEMA Floodplain Other: COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community: Soos Creek Area Drainage Basin Black River ©2012 D. R.STRONG Consulting Engineers Inc. 2 Welman Plat Technical Information Report Renton,Washington Part 6 SITE CHARACTERISTICS ❑River ❑ Floodplain ® Wetlands ❑ Stream: ❑ Seeps/Springs ❑ Critical Stream Reach ❑ High Groundwater Table ❑ Depressions/Swales ❑ Groundwater Recharge ❑ Lake: __ ❑ Other: ❑ Steep Slopes Part 7 SOILS Soil Type: Slopes: Erosion Potential: Erosive Velocities: Alderwood 0-6% Slight Slow (AgB) ® Additional Sheets Attached: SCS Map and Soil Description, Figure 4 Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT ® Level 1 Downstream Analysis None ❑ Geotechnical Engineering Study ❑ Environmentally Sensitive Areas ❑ Level 2 Off-Site Stormwater Analysis ❑ Level I Traffic Impact Analysis ❑ Structural Report ❑ Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION ® Sedimentation Facilities ® Stabilize Exposed Surface ® Stabilized Construction ® Remove and Restore Temporary ESC Entrance Facilities ® Perimeter Runoff Control ® Clean and Remove All Silt and Debris ® Clearing and Grading ® Ensure Operation of Permanent Facilities Restrictions ® Flag Limits of SAO and open space ® Cover Practices preservation areas ® Construction Sequence ❑ Other ❑ Other ©2012 D.R.STRONG Consulting Engineers Inc. 3 Welman Plat Technical Information Report Renton,Washington Part 10 SURFACE WATER SYSTEM ❑ Grass Lined ❑ Tank ❑ Infiltration Method of Analysis: Channel ® Vault ❑ Depression KCRTS ® Pipe System ❑ Energy Dissipater ❑ Flow Dispersal Compensation/Mitigatio ❑ Open Channel ❑ Wetland ❑ Waiver n of Eliminated Site ❑ Dry Pond Stream ❑ Regional Storage ❑ Wet Pond Detention N/A Brief Description of System Operation: Runoff from impervious surfaces will be collected and conveyed to the detention facility. From there it will be discharged to the Class 4 wetland located in Tr. "E" at the Site's northwest corner. Facility Related Site Limitations: Reference Facility Limitation Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTS/TRACTS ® Cast in Place Vault ❑ Drainage Easement ❑ Retaining Wall ❑ Access Easement ❑ Rockery > 4' High ❑ Native Growth Protection Easement ❑ Structural on Steep Slope ® Tracts ❑ Other: ❑ Other: Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were ncorporated into this worksheet and the attachments. To the best of my kno/,'ed•;• t e i formation provided here is accurate. Signed/Date ©2012 D.R.STRONG Consulting Engineers Inc. 4 Welman Plat Technical Information Report Renton,Washington FIGURE 2 VICINITY MAP •Sa7THST aFN 1 �. �`' I m ¢'� Z ui SE '2',Q ST �I ,c rr,curr ra a.Q i� SE,73iDST - I o 1 x 3 = z, - w ;36TH P� S 0 S-_- f �. M a /74111s72'''\ F _ - -,n- SE I `1. ',,,. r. 1 1 i�T!I ST i L 'K y SE PE r 12 DVI l5 KY RD— n- -_. i9 _ -- - R l»�_ �' �1 II R-6 ;i q ,i6 ,tet 1 - RgRO ..-: • ) 5 t SE 178TH i EL,V H� Sons Crt�k Park and Trail SITE SE 187TH fl s_1I9T,1PL 1.5-4 gST ST �`-'181STST R.� • I },a2,,. Renton I, R i SE iII2ri Co ST W { , :f 1a�,D PL (. 3e ,. -•- al 1 ST - y SE 184TH ST a C v4 �i 4 f SE,BlTH%. sa�,asm Pi M Si d TE' sE 1BHTH sT k = se r65r,1 sr . SE METH sr _ �I I SE lasT'H Pi iLT;: j +k sE,aeri4 '- jdye1 5x s R SE,90THST , .j , _... ,5i _ N SE Tx T IX S sir SE 193T � 7IIi �`, f -� ..T... R 6 re {�.�. _ - I_ _d —_ r __ _ SE 19ThID•ST 9t►lD. 9 I ; d d 5a:1Y1RD ___.�—_—_T - __�_..--_--__—' i < 1: Y a II ) R-6 SE 197111a 15 — 1 e 1r _ - �, d , Kent 0 Q, R-1 I �..,-. SE ISETOsT t=-! The information included on this map has been compiled by King County staff from a variety of sources and tits subject to change without notice.King County makes no representations or warranties,express or implied, as to accuracy, completeness,timeliness, or rights to the use of such information. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including,but not limited to,lost revenues or lost profits resulting from the use or misuse of the information contained on this map.Any sale of this map or information on this map is prohibited except by written permission of King County. ©2012 D.R.STRONG Consulting Engineers Inc. 5 Welman Plat Technical Information Report Renton,Washington FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS 2012 D. R.STRONG Consulting Engineers Inc. 6 Welman Plat Technical Information Report Renton,Washington � SS!.i,-r I � I I R1=f=499.20 � � I£=dd3.80(CENIFR OF D Q � �. 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H�s G.�� j � � ,_ G� , TR,4�:T B % , i , j � J(NNT I7SE DR/VEWAY I �� 1 TRACT D" \ ` ' � ._ � , , � t � 1\ � JO/M USE OR AY k �2 '� I NORTH �` ��� ! �. �� \ � ' � I \ti `� � `� r0 � I � �4 � ; GRAPHIC SCALE ` ` 1 ,_. 502 r- �c' i DRAFIEO BY.• CWiI i � �:� � t 502 � _ � � -- ` ' "� soo "'"' y` �. , 0 25 50 75 �c+v£a er w�s I � � L , � � �EXISTING FLOWS LEAVE SITE�AS SHEET FLOW ,' ; ' � �� `� aaa�cr Eivcav�:w.ts L� � ' � \���`i � �O SOUTHWEST AND SOUTN ALONG P OPERTY I I ': � , � I oA� a-2�t2 �nc�; t � 1 INCH = 50 FT. i � �i � i UNE � ��__ \/ ? i PRo,.�cr No.:�2ms � � �, � l� }'i�+�,LH��U�^� v � i � �i Lj :\2072\0\72016\3\Drowings\Plots\Engineering\Figs\03-3FIG3_72016.dwa 5/8/2G12 3:46:14 FM ?DT flGUR£.• .3 I I � � V�L. 63, FG. 35 � I �' I � � � COPYRIGHT �Q 2012, D.R. STROVG CCNSULI:NG ENGIh=ERS I�C. FIGURE 4 SOILS Clistifn R2531,TCA F.Porl &A Map a h ♦ .r.r 1 ..41 a alt T } ySITE lit , ' . L 4. . r ,. 1 e :gyp [: 13. -- . n D I 4. lii, , ,477. .. x ..ifr if e p4. �/ rv. a ti nAlli lit tliaiiima 113Z 1".....iY.T,NY. I. ti m limn p A p S io- b "JLI o- G z TG 143 id AgB—Alderwood gravelly sandy loam, 0 to 6 percent slopes Map Unit Setting Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 220 days Map Unit Composition Alderwood and similar soils: 75 percent Minor components: 25 percent Description of Alderwood Setting ©2012 D.R.STRONG Consulting Engineers Inc- 7 Welman Plat Technical Information Report Renton,Washington Landform: Moraines, till plains Parent material: Basal till with some volcanic ash Properties and qualities Slope: 0 to 6 percent Depth to restrictive feature: 24 to 40 inches to dense material Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water capacity: Very low (about 2.5 inches) Interpretive groups Land capability (nonirrigated): 4s Typical profile 0 to 12 inches: Gravelly sandy loam 12 to 27 inches: Very gravelly sandy loam 27 to 60 inches:Very gravelly sandy loam Minor Components Buckley Percent of map unit: 10 percent Landform: Depressions Norma Percent of map unit:4 percent Landform: Depressions Bellingham Percent of map unit: 4 percent Landform: Depressions Tukwila Percent of map unit: 4 percent Landform: Depressions Shalcar Percent of map unit: 3 percent Landform: Depressions AgC—Alderwood gravelly sandy loam, 6 to 15 percent slopes Map Unit Setting Elevation: 50 to 800 feet ©2012 D.R.STRONG Consulting Engineers Inc. 8 Welman Plat Technical Information Report Renton,Washington Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 220 days Map Unit Composition Alderwood and similar soils: 95 percent Minor components: 5 percent Description of Alderwood Setting Landform: Moraines, till plains Parent material: Basal till with some volcanic ash Properties and qualities Slope: 6 to 15 percent Depth to restrictive feature: 24 to 40 inches to dense material Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water(Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water capacity: Very low (about 2.5 inches) Interpretive groups Land capability (nonirrigated): 4s Typical profile 0 to 12 inches: Gravelly sandy loam 12 to 27 inches: Very gravelly sandy loam 27 to 60 inches:Very gravelly sandy loam Minor Components Norma Percent of map unit: 1 percent Landform: Depressions Bellingham Percent of map unit: 1 percent Landform: Depressions Custom Soil Resource Report 13 Seattle Percent of map unit: 1 percent Landform: Depressions ©2012 D.R.STRONG Consulting Engineers Inc. 9 Welman Plat Technical Information Report Renton,Washington Tukwila Percent of map unit: 1 percent Landform: Depressions Shalcar Percent of map unit: 1 percent Landform: Depressions ©2012 D.R.STRONG Consulting Engineers Inc. 10 Welman Plat Technical Information Report Renton,Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 — Discharge at the Natural Location: Drainage Adjustment L04V0085 was approved, allowing diversion of onsite flows to a single detention facility located in Tract "E". Runoff from the Site will discharge at the natural location which is a Class 4 wetland located in Tract "F" at the northwest corner of the Site. • C.R. #2 — Offsite Analysis: A Level Three Downstream Analysis was performed by Site Development Associates, LLC as part of the preliminary plat phase of this Project. A copy of the analysis is included in Appendix C. • C.R. #3 — Flow Control: The Project is required to provide Level 2 Flow Control. The proposed flow control facility is a combined detention/wet vault located in Tract "E". The Level 2 Flow Control standard requires the Project to match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the two-year peak flow up to the full 50-year peak flow, and also match developed peak discharge rates to predeveloped peak discharge rates for the 2 and 10- year return periods, assuming historic conditions as the predeveloped condition. (KCSWDM, Sec. 1.2) Furthermore, the Project must meet the Flow Control BMP requirements as specified in Section 1.2.3.3 of the Manual. The Project will utilize the reduced impervious surface credit to meet this requirement. • C.R. #4 — Conveyance System: New pipe systems and ditches/channels are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures and ditches/channels may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a "severe flooding problem" or "severe erosion problem" as defined in C.R. #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 subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. The proposed conveyance system was analyzed using the KCBW program, and is capable of conveying the 100-year peak storm without overtopping any structures or channels (see Section V). • C.R. #5 — Erosion and Sediment Control: The Project provides the nine minimum ESC measures. A CSWPPP is included in Appendix B. • C.R. #6 — Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual is included in Section X. • C.R. #7 — Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and site stabilization financial guarantee. ©2012 D.R.STRONG Consulting Engineers Inc. 11 Welman Plat Technical Information Report Renton,Washington For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. • C.R. #8 - The Project is located in the Basic Water Quality Treatment area. A combined detention/wet vault is proposed to meet this requirement. • S.R. #1 — Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 — Floodplain/Floodway Delineation: Not applicable for this Project. • S.R. #3 — Flood Protection Facilities: Not applicable for this Project. • S.R. #4 — Source Control: Not applicable for this Project. ©2012 D.R.STRONG Consulting Engineers Inc. 12 Welman Plat Technical Information Report Renton,Washington SECTION III OFF-SITE ANALYSIS An offsite analysis was conducted by Site Development Associates, LLC as part of the preliminary plat phase of this Project. A copy of the analysis is included in Appendix B. ©2012 D.R.STRONG Consulting Engineers Inc. 13 Welman Plat Technical Information Report Renton,Washington SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) KCRTS was used to model the peak runoff from the Site. Per Table 3.2.2.b of the Manual the soil type is modeled as "Till" for the Alderwood gravelly sandy loam SCS classification as shown in Figure 4 Soils. All onsite areas are modeled as till forest. Offsite areas are modeled as till pasture and impervious. Results of the KCRTS analysis are included in this section. ©2012 D.R.STRONG Consulting Engineers Inc. 14 Welman Plat Technical Information Report Renton,Washington PRE-DEVELOPED HOURLY TIME STEP MODELING INPUT: Land Use Summary I f L .Ila i -Area 11 Till Forest 2.99 acres Till Pasture 0.14 acres Till Grass 0.00 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.21 acres -Total 3.34 acres Scale Factor : 1.00 Hourly Reduced Time Series: PREDEVI >7j Compute Time Series Modify User Input File for computed Time Series [.TSF] PRE-DEVELOPED HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Frequency Analysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.231 2 2/09/01 18: 00 0.339 1 100.00 0.990 0.097 7 1/05/02 16:00 0.231 2 25. 00 0.960 0.202 3 2/28/03 3: 00 0.202 3 10.00 0. 900 0.053 8 8/26/04 2:00 0. 195 4 5. 00 0.800 0.121 6 1/05/05 8:00 0.179 5 3.00 0. 667 0.195 4 1/18/06 16:00 0. 121 6 2.00 0.500 0. 179 5 11/24/06 4 :00 0.097 7 1. 30 0.231 0.339 1 1/09/08 9:00 0.053 8 1. 10 0.091 Computed Peaks 0.303 50. 00 0. 980 ©2012 D.R.STRONG Consulting Engineers Inc. 15 Welman Plat Technical Information Report Renton,Washington FIGURE 5 PREDEVELOPMENT AREA MAP • ©2012 D. R.STRONG Consulting Engineers Inc. 16 Welman Plat Technical Information Report Renton,Washington - � - _� ;� � r�. _ ��- D � �- --- — � ��-_- '- `•o + i ��� `` ' -�. �' � D � � .,..- --- � — ___ - -- - - - - - - - -.....- - '. � Z. ,.�-� f- -- -- _ : � . .� „� ` ,�� _ `_. �.� , ¢ �� , l I� �Q- \ � �'• i --�------ --- �' -- -- --- ------------ - , . ` ' `- - - -__ : _. � __.,- --__.� _ ,' l , — D.R. STRANG E �� � , __._� d/ l, i , — _ "�, � .. ` \J _ �-�.s. '-'7 , \ 1 / / �.. — �.'G;._ _t EA57 �C � � ; t_ � � � / 7��.. .S..G� ���1 �K�i E�If�1�1S � I . ��_ {C.,�.' .- � s i // �aaw�rr�i imva.uw,w� --- � / . �OFFSITE AREA C ________--- - \��� � % �1_.�.L, , , Ca ,,, oszier��w F+z�az�am i __ �_ � ��..�-,�—t1—._� --� r �; ��� � <� GRA 1/EL/I�fPERVlOUS r-0.a8 A.C. �~ -_ _ "°-: �� i'. ,' —ST`�,� �-�--���-�� ,M,,:a.�w.� PASTURE = 0.06 .�.C._, � _` i i ti . l . �.' / , _ -- ___C.A.T. AREA'0:30 AC:. ; � -- �', �\ ��._— � y -��,��� ;.ti,>. } , ; � J � � a• s•�oo� �:, E. � y � � �, i �.' �-' ASSUME 0.25 AC. TO REMA/N � , , � � �'-r<� �o �E:��- � �� f .' ,' ',' l, .= `_ ^UIVCHANGED (DUE TO RO�KERY��7,�jT � �''- -��, ` '� I �-c.�r�r+ e;sa; �f�. ` ;�-i �! � �/ �/ -- CONSTRI�"��� � O �� /� j��l: „j ..� � GRAT==4^s7 3?. I � � i! � � !� � t_ ' :_� 7ftE}_;92.#7'(i2'DJ.) 1 � / � __�_.._ / � �� .� ` � 6!4C.'•C i I �a>�f--< = iY � � � � � — -- - -- � __ � . i s � /� � .- '-- ' �� � � '- � L�� ----_ � � i � fRQRTNe�.'�STERP4 G:IYDEPd ^ � �,/' r � � ' I �� , � rr�r�c�rs p::�. No. � � ,�;: / � , _ ) � V�L. 41, PC. 7,�, c'�2'.F/ /� / / / I �J � _ � ` .. .,__ (�' �. / i � / �" �� ,', , _,, / J / __.. --_-__�� J .�-- -� ♦ j �� � �CAiCH EASi�'i f f--- � � i 1 � � �� .' -�� �� ,` ,� { �_ I �,�.r�_;��<:✓ � _ ._-,- -' � : ` - _ _.'�`'�'� % " :, --- -- � ,�, �� ;'` ,��' '` � -- --� � OFFSITE AREA A �' � i / j ONS1TF AREA � � - � i I 3.24 A.C. - 0.30 A.C. = 2.99 A.C. I � �' -�' � � PAVEMENT/IMPERVIOUS = 0.13 q.C. \ ; � 4,.-� y` i - `: � �� � i� � ,-�' , --� --' PASTURE = 0.08 A:C. �� � ; �I � I ALL ONSiTE AREAS TO BE MODELED AS r � f 1 _ - � ,' i t � � ��� , �` ��\ ', \ � � � ' FOREST PER 2005 KCSA.IDM . � € + � � ��,�;�' .. •' � � ,. � � f. r r � f Fc;::�= -==- t� t \ i � '� c= ' '� , � EXlS77NG WETLAND t � ` `� 1 � , , QFFSITE AREA __ �� / i ` f, � `���5��.� �t �1 � � �; � � � I AREA A + AREA C = 0.35 A.C. � - � � �,�n�,� rJ � �P`�+o��a�;.� �' �� � I j � ( : ALL OFFSlTE AREAS MODELED AS EXlS77NG Q � � � Le't^-,,�`v � lr�Y � � ,,� 4 � � i"n' '= W�,' : � CONDITIONS FOREST PER 2005 KCSMDM � _ _- � , t —— � � , �_'_J` ; �� �o� , � x � , Q ; � ~ W r z, -: —' � —————- - _� " ; �� kF����,' v� 1`"'--�� ,` ;,``� I ,? ; � i KCRTS EX/ST1NG AREAS � h � -' t Fse,c-ss:e�1 � ��� , ; � � ���� FOREST = 2.94 A.C. � � � r .-r_'t-. ,s -�_ ! , __� � � , _ �� ' ��- �� --� t �� ���P o »� pp�i� a:;�r-_c O? � � � IA�IPERVIOUS = 0.21 A.C. � s� Z � �c�icsY�__��,-� • � p i I`� i'-�',...`�� I - �, �, `�'_- `; ; >�r �; PASTURE = 0.14 A.C. � � W � �! „-�`o�;(2' -� �� � y k'� �� i � � . - 1---_ � v TOTAL = 3.34 A.C. Q �l � 4'X.�'"'S��a t C i t.�r�-"-f) ♦ �, 3 ni 4 LYF' '.,�.� i �-`j �� + __ lp'G.R�ULP:2K s �O�riFD � k��t "E ,� �� I !� �`Y„ �� -...-- -- - _.._��_ C � O � � i `'�:. �� � .� 1 '� Fr � B Eu , 1 7 �� � I J � J -'^� -c s .i�£A.t 20E•t: j � ' �' � 1.. i�� t � 7 `\ �l �� ^�Q.E`s' I _GL�,`rH J . � � � ;-' -� �.. ..,.- -� �'-----� � �� �'� . ��Y�}�,� �fa��c ti �,,� � ' ,� W �� �� � �- � � W � �� j � t �� / �� �-,�.-7 1 v ' � ♦_ I � � � � \ �y 't � 1 - ;7 ! ; �i %f O ( 'i � f � � � � �� � � F - f i� I � f y "� i { ��,.--==::_ 7 ' f 1 i � / i � _�.,,.-.,--� 7 �I � � � � \� � / � �," `i . , _ ,, ', j� _ , , , _ : , r , ,: �,_` r '�t ,-----� �� i; � , f , , I , � ,. ..s- ; ti ` °- � ^,�, � � Q _ ` ` � , o ' �' , t � + i 3 � � ` \ °� . � ! •, �_�� _ � ti r � � y1 J . �——_"�—�"~ .'`'-...\ � t"� � i /1 _...__'_'__.._.._ _.—._._..__.._ ._'"___"'_ t ss�:u; `�� � � � � 'ti 1 � Frht=_sp;.;s ' ' i S �` �i� � �, [ � tE=-G�0.7d((k?�17%R Q' � ! '.. �i � \ ��� � rv.^.>' CHAidk'£L-, '3'Fi-S)-+\ f, � � I � a__a.::- 1 . �. � ` �, �ti� // ,..�,�--\4 �e'' ' � J OFFSITE AREA B � ` �, i / � � I � . O.OIAC. ��\ �1-l � tt �l ���'i� \�\` �� `i � ? ! J (TO OFFSlTE BASIN) � � t � � � �, i � � � � ����� ' i � � �L_� v, ' � N O RT H ��� '� : t� � �. - _ ; _,.� I��� � , ..:- , : ;ti � � ''. �. `�., ..-- ��.zr � .. ; = t � ; ' — , ' `` f`�, ; �..�� ; I � s ' ; � f i� , GRAPHIC SCALE � ; ," ; � � t - � s�F � �; �j i � 0 25 50 75 � � ���c,cE: � � aeAF�er.• cw� � . , , �. << �—��V�� �, � a , �� � � � � ~" 4� �, � ` � 1 INCH = 50 FT. �So�,a�Ec�£rrc+N� w.�s i � � � ' :' � DA7E p/-27—f2 PFO..ECT NO.:J20f6 R:\2012\D\12D15\3\�ro�.vings\Plots\Engineer'ng\F'gs\CS-3PREFIG5_12076.dwa 5/d/2i:12 2:7g;07 P61 FDT �GURE.• J� CG?'�KIGHT �O 2��2, D.�4. STF.O^JG CCNSUL-1tJG EN�ME�=RS INC. DEVELOPED SITE HYDROLOGY (PART B) DEVELOPED SITE AREA HYDROLOGY KCRTS was used to model the developed peak runoff from the Site. The soil type is unchanged from the pre-developed conditions. The portions of the Site within the clearing limits tributary to the proposed detention pond were modeled as "Till Grass" and Impervious as appropriate. Results of the KCRTS analysis are included in this section. KCRTS allows the flexibility of bypassing a portion of the development area around a flow control facility. All of the requirements listed below must be met. 1. Runoff from both the bypass area and the flow control facility converges within a quarter-mile downstream of the project site discharge point; and 2. The flow control facility is designed to compensate for the uncontrolled bypass area such that the net effect at the point of convergence downstream is the same with or without bypass; and 3. The 100-year peak discharge from the bypass area will not exceed 0.4 cfs; 4. Runoff from the bypass area will not create a significant adverse impact to downstream drainage systems or properties; and 5. Water quality requirements applicable to the bypass area are met. All of the above requirements are met. Runoff converges just downstream of the R/D facility in the Class 4 wetland; the detention vault analysis compensates for the bypass area; the 100-year peak discharge from the bypass area is 0.021 cfs; the bypass runoff will discharge to the Class 4 wetland, which is the natural discharge point; and the bypass area is exempt from water quality treatment requirements per KCSWDM Sec. 1.2.8 Exemption 1, since only backyard lawn and landscaping areas will bypass the detention vault, with an area less than 35,000 s.f. ©2012 D. R.STRONG Consulting Engineers Inc. 17 Welman Plat Technical Information Report Renton,Washington DEVELOPED HOURLY TIME STEP MODELING INPUT: 40 Land Use Summary I o-11 J Nal —Area Till Forest 0.00 acres Till Pasture 0.06 acres Till Grass 0.97 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 2.20 acres Total 3.23 acres Scale Factor: 1.00 Hourly Reduced Time Series: RDIN »1 Compute Time Series Modify User Input File for computed Time Series [.TSF] DEVELOPED HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:rdin.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Frequency Analysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0. 623 6 2/09/01 2:00 1.25 1 100.00 0.990 0.516 8 1/05/02 16:00 0.824 2 25.00 0. 960 0.747 3 2/27/03 7:00 0.747 3 10.00 0. 900 0.567 7 8/26/04 2:00 0. 680 4 5.00 0.800 0. 680 4 10/28/04 16:00 0. 663 5 3.00 0. 667 0.663 5 1/18/06 16:00 0. 623 6 2.00 0.500 0.824 2 10/26/06 0:00 0.567 7 1.30 0.231 1.25 1 1/09/08 6:00 0.516 8 1.10 0.091 Computed Peaks 1. 11 50.00 0. 980 ©2012 D. R.STRONG Consulting Engineers Inc. 18 Welman Plat Technical Information Report Renton,Washington BYPASS HOURLY TIME STEP MODELING INPUT: Land Use Summary 1=1 � p-I Mai —Area Till Forest 0.00 acres Till Pasture 0.00 acres Till Grass 0.10 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.00 acres —Total 0.10 acres Scale Factor : 1.00 Hourly Reduced Time Series: BYPASS >>I Compute Time Series J - _ Modify User Input J File for computed Time Series [.TSF] BYPASS HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Frequency Analysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.009 3 2/09/01 2:00 0.021 1 100.00 0. 990 0.005 6 1/05/02 16:00 0.011 2 25. 00 0.960 0.011 2 2/27/03 7:00 0.009 3 10.00 0. 900 0.002 8 8/26/04 2:00 0.009 4 5. 00 0.800 0.005 7 1/05/05 8:00 0.008 5 3. 00 0.667 0.009 4 1/18/06 16:00 0.005 6 2. 00 0.500 0.008 5 11/24/06 3: 00 0.005 7 1.30 0.231 0.021 1 1/09/08 6:00 0.002 8 1. 10 0.091 Computed Peaks 0.018 50.00 0.980 ©2012 D.R.STRONG Consulting Engineers Inc. 19 Welman Plat Technical Information Report Renton,Washington FIGURE 6 POST DEVELOPMENT AREA MAP ©2012 D.R.STRONG Consulting Engineers Inc. 20 Welman Plat Technical Information Report Renton,Washington VAULT AREA ASSUMED BREAKDOWN -1s4.�o � � � ,-=;-a_so(c£,+rrr oF 259� IMPERVIOUS (0.�04 AC.) c,;:�,;,.��:, �,v-s) � � D � � OFFSITE AREA C 759 GRASS (0.11 AC.) r, � �l_ GRAVFL/IMPERVlOUS = 0.08 AC. � PASTURE = 0.06 AC. �._�,�T_o OFF-VAULT GRASS-CRETE ' � '� - � ASSUMEO_IMeER-VlOUS u:��^�,.Tr_�_� ^ i-_�_ �,' ' c�7 '��` �m�c�E�mPs I � , ! - raro�ns�s su�xrsv � = _ .s "_ - ----_�� ti rmx�xn�nor��anww,xc�aaau __. _ _....______'_ • .. r `�� I ` ` — —'_ — — — —" — —.:.'' - � I :; f; 0125G77.910iR3 FIZf3T71V2f - l � �, 4 ...�a.ewa.n � � --- ------- -- -- - -----�- - ---. .. ----i� __ �.- ----------- --� - � ��� � ---- --- �--/-�-�--f�--- - - - --- �� �, `j- -- 1 U �r� /, _ � � ,I 1 .,% � � ' f-- ---- --- -. _ _�_ ��I i', �'--- `i ' � � 6' �' , - -, , J � _ , �- - -- _ 1 i ' � � � � � --- - - � � i 8 I � f I .I .�� � �_ '� ' ^� t , F� ! � } � 5 /� �"� �� � ' � � + i � C.A.T. AREA TO REMA/N, ` c � I � � � . ` — ' , � UNCHANGED 0.25 AC.i ti{ .} \/ i , ' ' �;� ° �' � j ` � � � , c� �r i �� ; i ." ---- f�* --�-' i�l �S ��/ ���' f , � �/ i�� � i `! i . � I � `�.------- / �� �l � � �/ �f I ' ,�------- . / - - - -- -- -- � �.I,' I � CONCRETE SlDEWALK �� � ` � ,r � ___ � �� /� �I � ONERETE S/DEWALK %j� I ______-�0.04 AC. ; � � � y' �;� �/� �.' _ �0.07AC.- - � � ��"L.� �% � �'ti �Y S,_': ' — ` ` --- -/'����' / ' J /�• � � ` _---_ _ ' � I , '_ _--�\ i I \,� _ � -,� � __ � / �/ ` � ___ I� I /J � � `j iI �E i: i'i_;',i � ` - ' / ! / .� � � __ _ � \ � �% ! ! r_ _r --- '� ~ j_,� BAC1S-YARDS OF COTS 5,'& 6� ' / '�� ,-��� � ���'. ' j � _-,- --- �' � TO�BYPA>SS DETENTlON f' l ' ,�� `_' /` �. � - 1 I '>� _--�-� �-_ (0.1 A"C.) �� , ONSlTE AS.PH�IL T � i IR- -- � � ' � , ,_ _ � ,' � ST�2E�TS & TRACTS � � A � � � '�, �; ���' � � t � ` � 0.50'�I C`- � � ` �. c� I, �TI ��-�'� � � � � � F-- _ _ �` �\ � I' !�� i I II � � � ' � �/J �� � _i I Q I.� f::.1�;-I� ., �� � . � i ,.��.� _-_-- �� I z �1 �\ � r'a !..'� ' � I // I —� �, � ` �'—�—' I '' � �; ` � ! : W�j :__� � � ` '� / ' � ' � ` �-1 , • ' � � � , �_� __ -- -- J ' Ii ' � � r f I � > > � ` Q � �o Q � -�.-< � � � � ! � � � /a 4&�T / �/� � / � I� ' , . A 7fJ�[S PV f.� i� � f � �^ � I / � � �l� ' . � ,�,---� � ��� � � �� �J � �� I �', �`� � � � �, t � + ; I Z � �f -�- � � _ , ^ � I' �, �'3 � �� , / , fi �` � ,' OFFS/TE AREA, A I � � ; I Q � � � ������ 1 �L � r !MP RV10US = 0.17;AC. � N i -i � � W , _ =;.',� __ �� � r .=�� � f— f -GRASS = 0.04'AC` `----- � - _t . - -_ / � � �r � - .� ;� � / , � �:_'_�� •` f '� -, W � —�: � f ` � ' i ,' I� ��` _ 1 ' � W � . - -- �� -� n � - "" - `�. - , �. , � - _ < r� r.,;__, �.�F r�� ,-- �� � ��� i� , u O � � / `` -- � �.,.._ / � � � } I `— ';lii.. 1'�i, �-=�;�_ %9-L�vl . i �7,� 1 � �� e� � I � l � � _�1/ __..-- / :..r� -� i i � ( � f � '� � (-�-�Ck I. "_ ' ' / i I O ' - � � f � � �� �� l - � �� I � � -__�`l`� � � J� ___-` � i � ��,� ��� �� � + : I � � \� `' �� � —I —�-� _1 � � i i � I � \ � � I i ♦ �r�- ♦_ � , . � f� ;I , . , i � �� ,, � �� , , — � — � ,I ' _ `v, , ! t� , I ' i ` , �� � � '� � � � � �\ � / , - - - . .-- � � � , i � � � ''� � � `� � _ �� � / �� �`� i �� ' � _ � / 1' � rONSITEa AREA'� R/BUTARY � I I i �� � , i �----. �._ --f � �,"- � � X Q `� MPERVIOUS ;�0.01 AC.) cM il ; I r � � ' 1 � , ' + � �� `� ' j : ,, M , _ _ � , ,— � �_ -- � ,� `� � I � 'rl`� OFF TE.AREA'B I�. � \1 � �f � ti� � / - � TRIBUTARS`. TO.�'OFFStTE I I � + � � •�,'� � / 8ASlN ='�0.06'AL: � 'i I ; � � � � . � , 1 ���"'I' � I ` I ' � \ � _ r� `,` � ^ �I i ; � �, �� , ; ( , � �., � ;i -; i NORTH �- � '� , � � � � '� � : GRAPHIC SCALE I :` < ; � � ` � �`� � ��� � :� �I � � 0 25 50 75 aR,��°er.• cxu I � PRQEC�fNCINf£R:W.5 __— -- i f `. f � � � !� _ ; I i .� � ' '� ' � �i� � j �. .. . � � s J :' o��.u,—z�,z , � ,: ! , � , .�;,:< � , � � 1 INCH = 50 FT. 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STROVG CONSULTIPlG EkGWEERS '�'JC- 2.29 490. 49 13666. 0.314 0.049 0. 00 2.39 490.59 14262. 0.327 0.050 0.00 2.49 490. 69 14859. 0.341 0.051 0.00 2.59 490.79 15456. 0.355 0.052 0.00 2. 69 490.89 16053. 0.369 0.053 0.00 2.79 490. 99 16649. 0.382 0.054 0.00 2.89 491.09 17246. 0.396 0.055 0.00 2. 99 491. 19 17843. 0. 410 0.056 0.00 3.09 491.29 18440. 0.423 0.057 0.00 3.19 491.39 19036. 0. 437 0.058 0.00 3.29 491.49 19633. 0.451 0.058 0. 00 3.39 491.59 20230. 0. 464 0.059 0.00 3. 40 491. 60 20290. 0. 466 0.059 0. 00 3.42 491.62 20409. 0. 469 0.060 0. 00 3.43 491. 63 20469. 0. 470 0.061 0. 00 3.45 491. 65 20588. 0.473 0.064 0. 00 3. 46 491.66 20648. 0. 474 0.067 0.00 3.48 491. 68 20767. 0. 477 0.071 0.00 3.49 491.69 20827. 0. 478 0.075 0.00 3.51 491.71 20946. 0. 481 0.079 0. 00 3.52 491.72 21006. 0.482 0.080 0.00 3. 62 491.82 21602. 0. 496 0.088 0. 00 3.72 491.92 22199. 0.510 0.094 0. 00 3.82 492.02 22796. 0.523 0.099 0.00 3. 92 492. 12 23393. 0.537 0.104 0. 00 4.02 492.22 23989. 0.551 0. 109 0. 00 4.12 492.32 24586. 0.564 0.113 0.00 4.22 492.42 25183. 0.578 0. 117 0. 00 4.32 492.52 25780. 0.592 0. 121 0.00 4.42 492.62 26376. 0. 606 0.125 0.00 4.52 492.72 26973. 0. 619 0. 128 0. 00 4. 62 492.82 27570. 0. 633 0. 131 0.00 4.72 492. 92 28167. 0. 647 0.135 0.00 4.82 493.02 28763. 0. 660 0.138 0. 00 4. 92 493.12 29360. 0. 674 0. 141 0. 00 5.02 493.22 29957. 0. 688 0.144 0.00 5.12 493.32 30554. 0.701 0. 147 0.00 5.22 493.42 31150. 0.715 0.150 0. 00 5.32 493.52 31747. 0.729 0.152 0.00 5. 42 493.62 32344. 0.743 0. 155 0. 00 5.52 493.72 32941. 0.756 0.158 0.00 5. 62 493.82 33537. 0.770 0.160 0.00 5.72 493. 92 34134. 0.784 0.163 0.00 5.82 494.02 34731. 0.797 0. 165 0.00 5. 92 494.12 35328. 0.811 0.168 0.00 6.00 494.20 35805. 0.822 0. 170 0.00 6.10 494.30 36402. 0.836 0.480 0.00 6.20 494.40 36999. 0.849 1.050 0. 00 6.30 494.50 37595. 0.863 1.780 0.00 6. 40 494 . 60 38192. 0.877 2.570 0.00 6.50 494 .70 38789. 0.890 2.860 0.00 6. 60 494.80 39386. 0. 904 3.110 0.00 6.70 494.90 39982. 0. 918 3.350 0.00 6.80 495.00 40579. 0. 932 3.570 0.00 ©2012 D.R.STRONG Consulting Engineers Inc. 23 Welman Plat Technical Information Report Renton,Washington 6. 90 495. 10 41176. 0. 945 3.780 0. 00 7. 00 495.20 41773. 0. 959 3. 970 0.00 7. 10 495.30 42369. 0. 973 4 . 160 0. 00 7.20 495.40 42966. 0. 986 4.340 0.00 7.30 495.50 43563. 1.000 4 .510 0. 00 7. 40 495. 60 44160. 1. 014 4.680 0.00 7. 50 495.70 44756. 1. 027 4 .830 0.00 7. 60 495.80 45353. 1. 041 4.990 0.00 7.70 495. 90 45950. 1. 055 5.140 0.00 7.80 496.00 46547. 1. 069 5.280 0. 00 7. 90 496.10 47143. 1. 082 5.420 0.00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 1.25 0.83 6. 16 494. 36 36768. 0.844 2 0. 62 0.23 6. 02 494 .22 35921. 0.825 3 0.82 0. 15 5.26 493. 46 31395. 0.721 4 0.75 0. 13 4. 68 492. 88 27943. 0. 641 5 0. 66 0. 13 4. 48 492. 68 26728. 0. 614 6 0.44 0. 08 3.50 491.70 20864. 0. 479 7 0.52 0. 05 2.89 491.09 17243. 0.396 8 0.57 0. 05 2.36 490.56 14075. 0.323 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0. 83 0. 02 ******** ******* 0.84 2 0.23 0.01 ******** 0.23 0.24 3 0. 15 0.01 ******** ******* 0. 16 4 0. 13 0.01 ******** ******* 0.14 5 0. 13 0.01 ******** ******* 0.13 6 0.08 0.00 ******** ******* 0.08 7 0.05 0.00 ******** ******* 0.06 8 0.05 0.00 ******** ******* 0.05 Route Time Series through Facility Inflow Time Series File:rdin.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 1.25 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.829 CFS at 10: 00 on Jan 9 in Year 8 Peak Reservoir Stage: 6. 16 Ft Peak Reservoir Elev: 494.36 Ft Peak Reservoir Storage: 36768. Cu-Ft 0.844 Ac-Ft Add Time Series:bypass.tsf Peak Summed Discharge: 0.836 CFS at 10:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability ©2012 D.R.STRONG Consulting Engineers Inc. 24 Welman Plat Technical Information Report Renton,Washington CFS 0 %0 0 0 0 0.003 35035 57.135 57.135 42.865 0.429E+00 0.010 5221 8.514 65. 649 34.351 0.344E+00 0.016 5806 9. 468 75.117 24 .883 0.249E+00 0.023 4210 6.866 81. 983 18.017 0. 180E+00 0.029 3934 6.416 88.399 11.601 0. 116E+00 0.036 2841 4.633 93.032 6. 968 0. 697E-01 0.042 1543 2.516 95.548 4 .452 0. 445E-01 0.048 1078 1.758 97.306 2.694 0.269E-01 0.055 852 1.389 98. 695 1.305 0. 130E-01 0.061 487 0.794 99.490 0.510 0.510E-02 0.068 20 0.033 99.522 0. 478 0. 478E-02 0.074 12 0.020 99.542 0.458 0.458E-02 0.081 17 0.028 99.569 0.431 0. 431E-02 0.087 27 0.044 99. 614 0.386 0.386E-02 0.094 30 0.049 99. 662 0.338 0.338E-02 0. 100 22 0.036 99. 698 0.302 0.302E-02 0.107 22 0.036 99.734 0.266 0.266E-02 0.113 21 0.034 99.768 0.232 0.232E-02 0. 119 32 0.052 99.821 0. 179 0. 179E-02 0.126 25 0.041 99.861 0. 139 0. 139E-02 0.132 22 0.036 99.897 0.103 0. 103E-02 0.139 11 0.018 99. 915 0.085 0. 848E-03 0.145 11 0.018 99. 933 0.067 0. 669E-03 0. 152 21 0.034 99. 967 0.033 0.326E-03 0.158 5 0.008 99. 976 0.024 0.245E-03 0.165 7 0.011 99. 987 0.013 0. 130E-03 0.171 6 0.010 99. 997 0.003 0.326E-04 0.178 1 0.002 99. 998 0.002 0. 163E-04 0.184 0 0.000 99. 998 0.002 0. 163E-04 0.190 0 0.000 99. 998 0.002 0. 163E-04 0. 197 0 0.000 99. 998 0.002 0. 163E-04 0.203 0 0.000 99. 998 0.002 0. 163E-04 0.210 0 0.000 99. 998 0.002 0. 163E-04 0.216 0 0.000 99. 998 0.002 0. 163E-04 0.223 0 0.000 99. 998 0.002 0. 163E-04 0.229 0 0.000 99. 998 0.002 0. 163E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS 0 0 0 o 0 0 0.003 35062 57 .179 57.179 42.821 0.428E+00 0.010 5405 8.814 65. 993 34.007 0.340E+00 0.017 5948 9.700 75. 693 24.307 0.243E+00 0.023 4080 6.654 82.347 17. 653 0. 177E+00 0.030 4029 6.570 88. 917 11.083 0. 111E+00 0.037 2632 4.292 93.209 6.791 0. 679E-01 0.043 1564 2.551 95.760 4.240 0. 424E-01 0.050 1003 1. 636 97.396 2.604 0.260E-01 0.057 798 1.301 98 .697 1.303 0. 130E-01 0.063 478 0.780 99.477 0.523 0.523E-02 0.070 27 0.044 99.521 0.479 0.479E-02 0.076 12 0.020 99.540 0.460 0. 460E-02 0.083 20 0.033 99.573 0.427 0.427E-02 ©2012 D.R.STRONG Consulting Engineers Inc. 25 Welman Plat Technical Information Report Renton,Washington 0.090 27 0.044 99.617 0.383 0.383E-02 0.096 32 0.052 99.669 0.331 0.331E-02 0. 103 16 0.026 99.695 0.305 0.305E-02 0.110 21 0.034 99.729 0.271 0.271E-02 0.116 22 0.036 99.765 0.235 0.235E-02 0.123 29 0.047 99.812 0. 188 0. 188E-02 0.130 25 0.041 99.853 0.147 0. 147E-02 0.136 25 0.041 99.894 0.106 0. 106E-02 0.143 12 0.020 99.914 0.086 0.864E-03 0.150 11 0.018 99. 932 0.068 0. 685E-03 0.156 21 0.034 99. 966 0.034 0.342E-03 0.163 5 0.008 99. 974 0.026 0.261E-03 0.170 6 0.010 99. 984 0.016 0. 163E-03 0.176 7 0.011 99.995 0.005 0. 489E-04 0.183 2 0.003 99. 998 0.002 0. 163E-04 0.189 0 0.000 99. 998 0.002 0. 163E-04 0.196 0 0. 000 99. 998 0.002 0. 163E-04 0.203 0 0.000 99. 998 0.002 0.163E-04 0.209 0 0.000 99. 998 0.002 0. 163E-04 0.216 0 0.000 99.998 0.002 0. 163E-04 0.223 0 0.000 99. 998 0.002 0. 163E-04 0.229 0 0.000 99.998 0.002 0.163E-04 0.236 0 0.000 99. 998 0.002 0. 163E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS Fraction of Time Check of Tolerance Cutoff Base New %Change Probability Base New %Change 0.061 0.70E-02 0. 68E-02 -2.1 I 0.70E-02 0.061 0.061 -0.2 0.074 I 0.52E-02 0.46E-02 -11.3 I 0.52E-02 0. 074 0.063 -14.5 0.087 I 0.40E-02 0.40E-02 -0.4 I 0.40E-02 0.087 0.086 -0. 6 0.100 I 0.30E-02 0.32E-02 6.0 I 0.30E-02 0. 100 0. 104 3. 9 0.113 I 0.22E-02 0.25E-02 17.3 I 0.22E-02 0. 113 0. 119 5.2 0.126 I 0. 16E-02 0. 16E-02 1.0 I 0.16E-02 0. 126 0. 126 0.2 0.139 I 0. 11E-02 0.96E-03 -15.7 I 0. 11E-02 0. 139 0. 135 -3.2 0.152 I 0.88E-03 0. 60E-03 -31.5 I 0.88E-03 0. 152 0. 142 -6.4 0.165 I 0. 60E-03 0.21E-03 -64 . 9 I 0.60E-03 0. 165 0. 152 -7.9 0. 178 I 0.39E-03 0.33E-04 -91.7 0.39E-03 0.178 0. 156 -12.5 0.191 I 0.18E-03 0.16E-04 -90. 9 I 0.18E-03 0. 191 0. 168 -12.2 0.204 I 0. 98E-04 0. 16E-04 -83.3 I 0. 98E-04 0.204 0.173 -15.2 0.217 I 0.49E-04 0.16E-04 -66.7 i 0.49E-04 0.217 0. 176 -18. 9 0.231 I 0.16E-04 0.16E-04 0.0 I 0. 16E-04 0.231 0.237 2.7 Maximum positive excursion = 0.008 cfs ( 7.3%) occurring at 0. 106 cfs on the Base Data:predev.tsf and at 0.114 cfs on the New Data:dsout.tsf Maximum negative excursion = 0. 049 cfs (-21.1%) occurring at 0.230 cfs on the Base Data:predev.tsf and at 0.181 cfs on the New Data:dsout.tsf ©2012 D.R.STRONG Consulting Engineers Inc. 26 Welman Rat Technical Information Report Renton,Washington FLOW FREQUENCY ANALYSIS 1.oaa3ng lute Series eite:nypass.csr -f Pained-Flow Frequency-KCRTS ILII O Return Period 2 5 10 20 50 100 • • 0 rdout.pks in Sea-Tac • • dsout.pks _0 PREDEV.pks -• BYPASS.pks R o o p O • 3 • 10-1_ o •I"- 00 W - N - • O 10-27 • • • • • • • • i 10 3 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 Cumulative Probability DURATION ANALYSIS Paused-Duration Analysis-KCRTS 1- rdout.dur o dsoutdur • TARGET.dur o co o R • • Ln U o a c'71 o ee o0 co o_co 0 ° i i 1 1 1 1 1 1 I i 1 1 1 1 1 11 l l 1 1 1 1 111 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 5 10 ° 10 s 10 2 10 1 100 Probability Exceedence ©2012 D.R.STRONG Consulting Engineers Inc. 27 Welman Plat Technical Information Report Renton,Washington WATER QUALITY TREATMENT SYSTEM (PART E) The Project is located in the Basic Water Quality (WQ) Treatment area. The Project will utilize a combined wetvault meeting Basic Water Quality treatment criteria. The design information is as follows: A wetpool will be provided below the live storage in the two northernmost cells (Cell #1 and Cell #2) of the detention vault. Cell #1 is 19.67 ft. by 104 ft. by 4 ft deep. Cell #2 is 19.33 ft. by 104 ft. by 3 ft. deep. This will provide a greater than 10:1 length to width . ratio which exceeds Manual requirements. The two cells will provide 14,213 cu-ft of water quality treatment volume, exceeding the minimum volumetric requirement (11,401 cu-ft.) for basic water quality treatment. Furthermore, per Section 6.4.2.2, when the length to width ratio is greater than 5:1, no baffle is required and the wetvault may be one celled. BASIC WETVAULT ANALYSIS As required per Section 6.2 2005 KCSWDM Step 1: Identify required water quality facility volume factor("f') f= 3 (basic wetpond volume factor) Step 2: Determine rainfall (R)for the mean annual storm per Fig. 6.4.1.A R= 0.47 in. Step 3: Calculate runoff from the mean annual storm (Vr)for the developed site. V,= (0.9A1+0.25At9+0.10Atf+0.01A0)x R/12 where . . . V,= volume of runoff from mean annual storm (c.f.) A,= area of impervious surface(s.f.) A,9= area of till soil covered with grass(s.f.) Aff= area of till soil covered with till forest(s.f.) Ao area of outwash soil covered with grass or forest(s.f.) R= rainfall from mean annual storm (in.) A,= 95,832 s.f. At9 43,124 s.f. Atf= 0 s.f. Aa= 0 s.f. R= 0.47 in. V,= 3,800 c.f. Step 4: Calculate water quality volume (Vb). Vb= f x V, where . . . Vb= water quality volume(cf) f= volume factor from Step 1 V,= runoff volume from Step 3 Vb= 11,401 c.f. (minimum wetpool volume required) ©2012 D.R.STRONG Consulting Engineers Inc. 28 Welman Rat Technical Information Report Renton,Washington FIGURE 7 DETENTION & WATER QUALITY FACILITY DETAILS ©2012 D.R.STRONG Consulting Engineers Inc. 29 Welman Plat Technical Information Report Renton,Washington NE 1/4 SE OF SECTION 32, TOWNSHIP 23N, RANGE 5E, W.M. i WELMAN B 3.5' S'r10'GRATED ACCE55 I . -.. ... ._ _ - - - - - _ - - - - __ . .. .. ..- ..,.. . .,:. . .:-... . ,.:.... .... ...�- � ..;.�..,; ' .,",. �9 a�� . � ..-.. .. ..:. �... ,. -.- .:._. �. , .._ ..:.. -:.... .. ._.. . -'•::..... .. . ...-: .. . ... . . � II ae1.3o � � � I _._ _ _ DETEN7IGN VALCT NOTES FLFOW RE57idC70,4 /SP.rLL COIJ7ROL MO'�S� I \ J' � 1. HlILA!Uu L,'+E/C!'ESS/dANHIXE PER CELL NTlH AT LFAST }, plpE SlZES AND SLOPES PfR PLANS I . `FRA{�,GRA7E Q SCYID fRANE GRATE Q SIXfD� �NE A�Cf>5�fR SC'VA(�LT LE�VCTH Q7 W10R4 2 OlJIlE7 GPAGTY:NOT LESS THa'J CO.VdJ!£D IN[EiS. ICOY£R MARKfD bFA/N' COLfR MARK£D'APAM' {_ _ 2. 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I �' W/LOLY(IN6 30LiS�f , I I 5.4ALL BF�M1'STALLED AT PIE E:JIRAA'CF TD 7HE 6�IMDE CONCRETE PAD /�F•4CVAL. SPECIA!CARE SHALI 9E EXERGSED DURIMG N07E 3 k K075 ONG ✓AULT. 7FfE S'G.v 41ALL 6E HJlIG W^iE iL: ��/��j�� p• r COh'S7RUG77CN TO Pi'A7 Pr1c'VAN_T 15&IIiT KR PLAN I � I �1-022 4 2-023 LFM�ER Pli4'G GR£ASIEn'EO?O R1f A'SJE �j\\//i�i�/\/\' �I rF1M57!GRADE qS DETA2ED. ENGI,4EER C�RP.r;C/PON OF FNfL VA'J!7 � I 7(W 49760(NATCN fG) ��� ?,IfJ.^,A�:C 8E N93Lf FROM TH£OPEN�h'G ��. �\� VOLL'.'LES BASFO 01J AS 6'J.27 SURVEY GA7A ARE . �: ' � �%�/ /� �/%�/%i �/\�/i�/�{. RfIXI D 5Y T''E C N..F F N'�7N �. -�-::....,. ... ....:� . :'... ._. .._....... ,.. .....: ..� ,.. � - � , . _ ..._..::�. ' ' :,.:.., ,,.. . ._:.. .. .. - . _ �._ . . .� , . . ....::.. ....::�.:� . . ..._..,. . 48].70 - � - � - - - - - _ - -.. �.�:. .�.:".- - GCO \\ \t _ -,�� / ���i\i\/ %�Jj\�/i�i \ - - �' \ RcAIOVA82£NA/N7ENANCE ACCE55� - - -PLAN VIFW - - - - - -B - - V ��\\\ \���� . . � e . 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FOOIINC - . . -.. . .�...- ' SECTION A-A AVERAGE 1'SEfkN£N7 PROiEC�ON(lYP.)SEE SiRUC7URAL ONGS SECTION B�B 1'SEDl{IfN7 S�ORAGE � � SCAL.:7=5 STCRI,GE M C2L/7 ase� _ i ss SGLE:1=5 � c D.H.STRONG S15 �ns Noreo :� CITY O- WELMAN �'os-o7-i2 CaA 2 Workhg Deys Before You Dig D � � C0^'S""'"��"'�""� ��E""' �� � � R E N TO�`J TIR FIGURE 7 � �. r 1 800 424 5555 ���'� �"° ,aaxExe,�r,aw�maa�uaxw��r �� _ ���� oWTuu Uh7Siea Urxlergrand Lxation Centx or2iez7.sc�F�ziez72rv �'yN � •+�s� � P arr��ng/Buildirg/Publ�c Wor<s Dep'.. �. (D.LTf.FD.ORWA) ww:dwap.mn N0. r'.���I�ION � '�A,TE APP�3 � s-�c.a�c�r - . �iw ��'FlG 7' , � A-NNNNAA i SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per C.R. #4 of the KCSWDM, the conveyance system must be analyzed and designed for existing tributary and developed onsite runoff from the proposed project. Conveyance criteria require that all new pipes be designed to convey and contain (at minimum) the 25-year peak flow. The conveyance system as designed will convey the 100-year peak storm without overtopping any structures. A conveyance system consisting primarily of pipes and catch basins has been designed for the Project. Onsite runoff will be collected by the multiple catch basins. Pipes are typically twelve- and fifteen-inch diameter LOPE material. The pipes will have a minimum slope of 1.00%. The vault primary overflow riser is designed to convey the 100-year peak storm (design storm), based on the KCRTS 15-minute time series for developed, undetained conditions on site. This is calculated at 3.10 cfs. The results of the 15-minute KCRTS time series, overflow riser analysis, and KCBW Calculations are included in this Section. Vault Outfall The conveyance analysis for the outfall pipe was performed using the FlowMaster software. The analysis results are included in this section. Since the calculated barrel velocity is less than 5 fps, a rock pad outfall protection system is appropriate. This outfall system consists of a 15" diameter pipe and 7.5' wide by 10' long rock pad per Table 4.2.2.A of the KCSWDM. The rock pad is designed to dissipate energy from the developed, undetained 100-year, 15-minute design storm without adversely impacting the downstream properties. The rock pad will disperse runoff to the Class 4 wetland located in Tract "F". Due to Site constraints, the rock pad is located adjacent to the west boundary of the Site in order to provide a minimum 0.5% slope for the outfall pipe. 4 C:\Users\WJS.I.DRS\Desktop\FLCWMA--I.EXE Haestad Methods FlowMaster I version 3.43 Circular Channel: Manning's Equation Comment: i " LCPE $ut all Pi.e Anal sis Solve For Diameter ft Velocity fps Slope ft/ft Flow Area sf Manning's n Critical Slope ft/ft Discharge cfs Critical Depth ft Depth ft Percent Full. . X Froude Number. Full Capacity. cfs QMAX e_94D. . . . cfs Enter Worksheet Description <Fi> Hel. <112> Print <P3> Calculator <P.Dn> Create Table <ESC> Exit ©2012 D.R.STRONG Consulting Engineers Inc. 30 Welman Plat Technical Information Report Renton,Washington DEVELOPED 15-MINUTE TIME STEP MODELING INPUT: Land Use Summary I o p I wan -Area Till Forest 0.00 acres Till Pasture 0.06 acres Till Grass 0.97 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 2.20 acres -Total 3.23 acres Scale Factor: 1.00 15-Min Reduced Edit Flow Paths I Time Series: 15-MINUTE >> Compute Time Series I Modify User Input I File for computed Time Series [.TSF] DEVELOPED 15-MINUTE TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:15-minute.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Frequency Analysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 1.05 6 8/27/01 18:00 3. 10 1 100.00 0. 990 0.732 8 1/05/02 15:00 2.20 2 25.00 0. 960 2.20 2 12/08/02 17:15 1.45 3 10.00 0. 900 0.844 7 8/23/04 14:30 1.24 4 5.00 0.800 1.20 5 11/17/04 5:00 1.20 5 3.00 0. 667 1.24 4 10/27/05 10: 45 1.05 6 2.00 0.500 1.45 3 10/25/06 22:45 0. 844 7 1.30 0.231 3.10 1 1/09/08 6:30 0.732 8 1.10 0.091 Computed Peaks 2.80 50.00 0.980 ©2012 D.R.STRONG Consulting Engineers Inc. 31 Welman Plat Technical Information Report Renton,Washington FLOW CONTROL PRIMARY OVERFLOW Using standard orifice equation to determine stand pipe diameter in control structure Ref. KCSWDM '05 Figure 5.3.4.H Q100= 100-Year Peak Storm calculated using KCRTS 15-Minute Time Steps Q100= 3.1 cfs HMAX= Maximum available head in feet measured from crest of weir HMAx= 0.5 ft. D = Riser Diameter D= (Q100/(3.782 * HMAX"))" D = 1.08 ft. (min. diameter) round up to nearest standard pipe diameter use D= 15 in. or 1.25 ft. Calculate actual height above the weir expected during the 100-year peak storm H = Actual head above weir achieved with Q100 H = (Q100/(9.739 * D))^0.67 H = 0.40 ft. ©2012 D.R.STRONG Consulting Engineers Inc. 32 Welman Plat Technical Information Report Renton,Washington BACKWATER ANALYSIS BACKWATER TABLE Storm Water Runoff Variables: A= Total of Subasin and Tributary Areas C= Runoff Coefficient(the anticipated proportion of rainfall volume that runs off the area)see 2005 KCSWM Table 3.2.1A Cc= Composite Runoff Coefficient Cc= S(Cn*An)/Arota To= Time of Concentration(Typically 6.3 minutes which is the minimum value used in calculations) R= design return frequency IR= Unit peak rainfall intensity factor IR= (aR)(Tc)A(-IDR) aR,bR= coefficients from'98 KCSWM Table 3.2.1.6 used to adjust the equation for the design storm IR= Peak rainfall intensity factor for a storm of return frequency'R' IR= PR*tR PR= total precipitation(inches)for the 24-hour storm event for the given frequency. See Isopluvial Maps in 2005 KCSWM Figures 3.2.1.A-D QR= peak flow(cfs)for a storm of return frequency'R' QR= Cc*iR*A The Q-Ratio describes the ratio of the tributary flow to the main upstream flow. R= 100 -year storm aR= 2.61 bR= 0.63 PR= 3.09 inches Conveyance System Variables: d= pipe diameter n= Manning's Number 1= length of pipe ©2012 D.R.STRONG Consulting Engineers Inc. 33 Welman Plat Technical Information Report Renton,Washington Pipe Structures Subasins& A A C CC Tc iR IR QR SQR Q- d Material n I Slope invert invert over- Q V Bend CB Tributaries subasin Ratio in out flow Full Full Dia elev. Flow Flow FROM CB To CB sf Ac Ac Min. cfs cfs in ft % ft ft ft cfs fps CBtt5 TO INLET 1 5 5 4 5 10703 0.25 0.90 6.3 0.82 3.19 0.71 0.71 0.00 12 N-12 0.012 47 1.09 494.93 494.42 498.13 4.05 5.15 0 2 4 4 3 4 1051 0.02 0.90 6.3 0.82 3.19 0.07 0.78 0.10 12 N-12 0.012 48 1.01 494.42 493.93 497.62 3.90 4.96 0 2 3 3 2 3 10267 0.24 0.71 6.3 0.82 3.19 0.53 1.31 0.69 12 N-12 0.012 33 4.55 493.93 492.43 497.46 8.26 10.51 62.87 2 RUN 11-2 95794 2.20 0.70 2 2 1 2 4804 0.11 0.90 2 2 1 2 100598 2.31 0.71 6.3 0.82 3.19 5.25 6.56 4.01 15 N-12 0.012 96 3.35 492.18 488.95 497.18 12.85 10.47 62.87 2 1 1 INLET 1 1 10117 0.23 0.69 6.3 0.82 3.19 0.51 7.07 0.08 15 N-12 0.012 12 18.33 488.95 486.75 497.69 30.04 24.48 33.38 4 CB#12 TO CB#8 12 12 8 12 21176 0.49 0.68 6.3 0.82 3.19 1.06 1.06 0.00 12 N-12 0.012 34 1.00 496.00 495.66 499.22 3.87 4.93 0 2 C B#7 TO C B#6 7 7 6 7 9672 0.22 0.68 6.3 0.82 3.19 0.48 0.48 0.00 12 N-12 0.012 24 1.04 495.00 494.75 498.23 3.95 5.03 0 2 CB1f11 TO CB#2 11 11 10 11 13081 0.30 0.67 6.3 0.82 3.19 0.64 0.64 0.00 12 N-12 0.012 89 1.01 497.50 496.6 501.36 3.89 4.96 52 2 10 10 9 10 16852 0.39 0.70 6.3 0.82 3.19 0.87 1.51 1.35 12 N-12 0.012 33 1.53 496.60 496.09 499.82 4.78 6.09 29 2 9 9 8 9 18437 0.42 0.71 6.3 0.82 3.19 0.95 2.46 0.63 12 N-12 0.012 43 1.01 496.09 495.66 499.68 3.88 4.94 46 2 RUN 12-8 21176 0.49 0.68 8 8 6 8 6057 0.14 0.69 8 8 6 8 27233 0.63 0.68 6.3 0.82 3.19 1.37 3.83 0.56 12 N-12 0.012 73 1.25 495.66 494.75 498.97 4.32 5.50 0 4 RUN 7-6 9672 0.22 0.68 6 6 2 6 5715 0.13 0.72 6 6 2 6 15387 0.35 0.70 6.3 0.82 3.19 0.79 4.62 0.21 15 N-12 0.012 120 1.93 494.50 492.18 498.23 9.76 7.95 86 2 2 2 1 2 4804 0.11 0.90 6.3 0.82 3.19 0.32 4.93 0.07 15 N-12 0.012 96 3.35 492.18 488.95 497.18 12.85 10.47 26 2 95794 2.20 0.70 ©2012 D. R.STRONG Consulting Engineers Inc. 34 Welman Plat Technical Information Report Renton,Washington FIGURE 8 BACKWATER ANALYSIS MAP ©2012 D.R.STRONG Consulting Engineers Inc. 35 Welman Plat Technical Information Report Renton,Washington �„ , , :, _ I - _ -< < _ , . _ _- - __ ___ _ _ ` ___ � �__ _—...� � - - _ --- � .,�,, � _ ---- ----- ` :. � ' ��, � `, �- � . - - �CB._T TYP£2-48" ..—_-_ '� } t` , -- " i - _.._._ �-- �� 49.69 _ " � - . -- -- __��._ -.-___.— _ .�-_~._ �, '__- ----- .. .�-'- . I �. L '` � ---- --.--.__-._.------ �� ..;. ��. /- -�-- '-- 6 l£�6+3:70�-- ---- -. .-__ ... --- - �.. ' ... ` ` � , --- - '� �� / -"- -- - -}5'-I£-I88.9 --- - ' ._,_ __.-..._ ----�---- � __. ..-- '-, 1 . — _...._. --- - _ , i �` _ --- ---. � ' . - - 4 £7 � - -' _a,� � ` � t� �_ ��r��' '. , � � , -- _. SFA-7�f�5.0T,�T1.7 � � n� 5 TYd^-=t /� �as x�n�g stiavfraRg � � i, . 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' � r�u cuRe�ruEr , � : ' S � i i �� �' �-�- --- _. _STA 2f39.3� 2Q89'R � ; � � � � • o . --�u��s�ra �t� ca a rrPF� ' l , 03 SF %; t-.. : .�' c ��-� E q�. � 4 � � �� i .� � � 12'I£492 43£"� ' � �-{ U U� lN ' � _, C- t iF ;.. .: � � , i �� .'` % 15'tE��4?TB_S,tY 1 STA. ?+37.32, 72.00'L f' ! ..` I (�)_ .��(i� '.I.`,. __- -----"'- " _t-:_-., / �, � � ,�' �/,�- � ' �/ R1Y 497.46 i t g� . . � __ -_ � ' � � � i / . ..� _ � f� � 6'I£494.A3 S i . �1 i,.. � ' � j� � � � � . � � �� T2`lE 493.93 NJF.I�JSY � i� ' - .` ' � � �V� 1 - ' �: �; �or��i-���Ts; � �� . l � � __ jA -- -- -- 1Y.�,C7S E ��. /. , __ , � / ,- __ -__-- - � - '� L3 � �-`:�_ �; --- ---�' r / / f V -- A - -7,-8D�_,sF � ; � --:i 1 - __ __ - -e` •� "' � �. i- _ _---- .- .�/5- y ..-. ..,� \\., ' ' i -cA=cH _ . � � � � � �� �� ! c-:�.�- _ _._ 1 ! :, � � _ -'� � i- i __i0't.X�-25'W X J Tlii . .✓ � g J� " � - � �`` �� _ i� ' � P•OCX LINiNG OUTFAlL - " ` � - �' ,�� . - � PROTECTCN PfR ----� _ - _ � I �°� t � � C8 TY�E fl,/' --._ " CB 7 T1'PF 7 � I - �--KCSVr�U TABLE 4.2.2.A ,., / r / / �`. . _ ��� - - j f� � � R�99d22rn, i2f7'R STA 3t5Q01. 1217':,1 ;� I % I -� � ^ ~ i� l 1 t � �^' RMI498._A �� �.• � /, � r S'1E.495.1'3 W 7 _ _ 6'f£4s3.50. � �� i � � 72 1F 494.75£ ("` ���-�fi2'1£4rLi.00� ���`-� . � : ! I ; � i �i /` r 7 � , , J5'lE 494.513.�N _ I" 8 '� ` : _ __ . � � � :- ' l � , �- , .��, � � � , r � L6 -�� � -� - ' �` I ' 2s 7sF, '. ! v�i �, � � , - - � � � 3 995�SF � � � ' __--- - - , ;� � r , ; v � J i , ------ 1 l, -- - f + ; ' � J :. „ �. - � � ' ' - ./ i` t � ' t1 t N c�'o �� \' � � i � - 4 .F..�; .,_.,f � .- - j �� t-- � , 4 � ! � i W ! � " F �Cr�S)_ - - _ / -� � , ! � � i, � � ';<��_i r`--- � -- t � � � STA. �t25.06, 7295'R (n (n �� { � i,: � � � �! � ` RA/�9d98 � � � i '�i -- L9` .- ,� T '� 6-,�,�.�6 w �I �,rsl j � � � � � t J J � --- �f2'�t£�95.68 SS£ y ' � W � � --��i,14� SF� 1 � 1'.+�lF 495.41 N f- � . � � � �'-- � � , - --�" - -- � �� _ ' , � L8 co � , j Z � z �' � _ � ' � i� ,, ��,971 SF ,' � ._ i � �°� _ 1 Q C� Q _ . : ���.J G�-;,� t ,' ,_ ` -_� ` � R9 i � C9 !2 TYPE 1 ` : � `� � � W �t77 PG"u 7£af3o: . � � � � � ��4 297 SF ' �r�F ,srA 4fa9o4 �zrr c t' � �� ; �- � : f � ' , ' V 'R!N 499.22 .. -._ _.____ ---,--.----- � � , ,� , � � - �_ , � , a� s-��s�E W � Q ' � � ��j .__ - CB�?TYP£ i t � _ , `+f2P�1£4BG00 NW ` � ;�, � � �s� - -'- � - � STA. 4+86.SB,'l&6�'R; '6., } �` � �!"t i__ _ `. . ' � I � i v � t i t ` I ,� � t ? 72'1£�495.09�S,NF �� �''� ' � ' f i Q ` ' ` - 1490 � � � �� � ; r i „ ; �p , � ; ,�� = .. �� 3��646 iSF p,i - . --• c�N � � ��� � � `,, , i ,� ���8�o � ,'' � - L�2 � ( =; � ` � ' � � 73 60 ` . ; , ,,-- : ; STA. 5+0 . . � ' � ,� /J- R1AI 499.8 - --''-�18 �.-� 7 ' % 1 � �� • ' � 6'!f 497 «f `, � .�'�Ft .SF . �� I ; � ; � I - --- _ — _. r �-_ � � y � f2-�£as \ � � - , � � � , , .. F : . � � � 1 ' � � ` �` ��°� , r _ ,. � � � i �� ..� � � � � ; ; , .J./ H � 1 ca n rrPF r ' ` '- t ,: � --_ _ -----_-- t , �/ ! I STA 5+857. 44.D�'L '-- � _, ` �' ` j f . � f� � R!M 501..36 I t `. 11\854 SF� �cv j s`!£498.0 w L�� - ) i � ; ',, � `� ..\ �� � �N � i2'!£49Z5 N�3,206 SF j { i � � I �, �. �t � � ` I l, ,�\ `�_ � �� � �� , '�..` ! � � �� i � ��� � - � � %.� I t � � \ -�� l `, � � � I � j � � NORTH - �. , ` �'� ..� ` � . i�"��"� — � � �. - � � � ! � � � GRAPHIC SCALE � , � ' � \ r i i P 3 f � 0 25 50 75 . � � l: � � I I ( ^�_�C�i I � � �� I;�: � � � (�', � � .�' , ; �- � DRAF7E0 8Y.• CWA � / • / • YlALHh�N C8 14. TYPE i �+ ' ,.� i CB 1$ TYP£1 G STA.14+03.27, fd88 R � , t�LF� DE57pV£D BY.• MLlS � j � y�L. &3, PG. 3� � � i �M t49&70(dfATCH FG) + �� STA.i4tQ3.75, 77.74't 1 INCH = 50 FT. PRo,�cr£n,c,n,�•was � 12'I£49&79 I j'i+ I R/M t498.70(MATCH£G) DA7E.•01-27-f2 � � � ! �J I' 7 � f2"!£t�96.83(MATCF!£K lE) ��. � � � , �: , , PRO,.ECT NO.:1?018 R:\2012\0\72076\3\Drowings\Plots\Engineering\Fiqs\OS-3BWFIGS.dwg 5/5/2012 70:13:45 AM PDT fIGlIRf.' 8 '� COPYRIGHT �02��2, D.R. STRONG CONSU'_TING ENG.VEERS INC. '� � BACKWATER COMPUTER PROGRAM FOR PIPES BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#5 TO INLET 1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:494.22 feet Discharge Range:0.7 to 7.07 Step of 0.637 [cfs] Overflow Elevation:498.13 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 12 LF - 15"CP @ 18.33% OUTLET: 486.75 INLET: 488.95 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 497.69 BEND: 33 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.08 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.70 5.28 494.23 * 0.012 0.33 0.14 7.47 7.47 5.28 5.28 0.33 1.34 5.29 494.24 * 0.012 0.46 0.18 7.47 7.47 5.27 5.29 0.51 1.97 5.32 494.27 * 0.012 0.56 0.22 7.47 7.47 5.28 5.32 0.66 2.61 5.35 494.30 * 0.012 0.65 0.25 7.47 7.47 5.29 5.35 0.79 3.25 5.39 494.34 * 0.012 0.73 0.28 7.47 7.47 5.30 5.39 0.92 3.89 5.45 494.40 * 0.012 0.80 0.31 7.47 7.47 5.31 5.45 1.03 4.52 5.51 494.46 * 0.012 0.87 0.33 7.47 7.47 5.32 5.51 1.14 5.16 5.58 494.53 * 0.012 0.93 0.36 7.47 7.47 5.34 5.58 1.26 5.80 5.67 494.62 * 0.012 0.98 0.38 7.47 7.47 5.35 5.67 1.40 6.43 5.76 494.71 * 0.012 1.03 0.40 7.47 7.47 5.37 5.76 1.56 7.07 5.86 494.81 * 0.012 1.07 0.42 7.47 7.47 5.39 5.86 1.74 PIPE NO. 2: 96 LF - 15"CP @ 3.35% OUTLET: 488.95 INLET: 492.18 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 497.18 BEND: 62 DEG DIA/WIDTH: 2.0 Q-RATIO: 4.01 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.65 2.08 494.26 * 0.012 0.32 0.20 5.28 5.28 2.07 2.08 0.41 1.24 2.12 494.30 * 0.012 0.44 0.27 5.29 5.29 2.09 2.12 0.59 1.83 2.21 494.39 * 0.012 0.54 0.32 5.32 5.32 2.15 2.21 0.75 2.42 2.33 494.51 * 0.012 0.63 0.37 5.35 5.35 2.24 2.33 0.89 3.01 2.49 494.67 * 0.012 0.70 0.42 5.39 5.39 2.34 2.49 1.03 3.61 2.68 494.86 * 0.012 0.77 0.46 5.45 5.45 2.47 2.68 1.16 4.20 2.91 495.09 * 0.012 0.83 0.50 5.51 5.51 2.63 2.91 1.30 4.79 3.18 495.36 * 0.012 0.89 0.53 5.58 5.58 2.80 3.18 1.44 5.38 3.47 495.65 * 0.012 0.95 0.57 5.67 5.67 3.00 3.47 1.60 5.97 3.81 495.99 * 0.012 0.99 0.60 5.76 5.76 3.23 3.81 1.79 6.56 4.17 496.35 * 0.012 1.04 0.64 5.86 5.86 3.48 4.17 1.99 PIPE NO. 3: 32 LF - 12"CP @ 4.55% OUTLET: 492.43 INLET: 493.93 INTYP: 5 JUNC NO. 3: OVERFLOW-EL: 497.46 BEND: 62 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.69 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.13 0.34 494.27 * 0.012 0.15 0.09 1.83 1.83 0.33 0.34 0.18 0.25 0.39 494.32 * 0.012 0.21 0.12 1.87 1.87 0.37 0.39 0.25 0.37 0.49 494.42 * 0.012 0.25 0.15 1.96 1.96 0.46 0.49 0.32 0.48 0.60 494.53 * 0.012 0.29 0.17 2.08 2.08 0.58 0.60 0.37 0.60 0.77 494.70 * 0.012 0.33 0.19 2.24 2.24 0.75 0.77 0.42 2012 D. R.STRONG Consulting Engineers Inc. 36 Welman Rat Technical Information Report Renton,Washington 0.72 0.97 494.90 * 0.012 0.36 0.20 2.43 2.43 0.95 0.97 0.47 0.84 1.21 495.14 * 0.012 0.39 0.22 2.66 2.66 1.18 1.21 0.51 0.95 1.48 495.41 * 0.012 0.42 0.23 2.93 2.93 1.45 1.48 0.56 1.07 1.79 495.72 * 0.012 0.44 0.25 3.22 3.22 1.75 1.79 0.60 1.19 2.14 496.07 * 0.012 0.47 0.26 3.56 3.56 2.09 2.14 0.64 1.31 2.53 496.46 * 0.012 0.49 0.27 3.92 3.92 2.46 2.53 0.68 PIPE NO. 4: 48 LF - 12"CP @ 1.01% OUTLET: 493.93 INLET: 494.42 INTYP: 5 JUNC NO. 4: OVERFLOW-EL: 497.62 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.10 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.08 0.15 494.57 * 0.012 0.12 0.10 0.34 0.34 0.12 ***** 0.15 0.15 0.21 494.63 * 0.012 0.16 0.14 0.39 0.39 0.16 ***** 0.21 0.22 0.25 494.67 * 0.012 0.20 0.17 0.49 0.49 0.20 ***** 0.25 0.29 0.29 494.71 * 0.012 0.23 0.19 0.60 0.60 0.23 ***** 0.29 0.36 0.37 494.79 * 0.012 0.25 0.21 0.77 0.77 0.30 0.37 0.33 0.43 0.52 494.94 * 0.012 0.28 0.23 0.97 0.97 0.49 0.52 0.36 0.50 0.74 495.16 * 0.012 0.30 0.25 1.21 1.21 0.73 0.74 0.39 0.57 1.02 495.44 * 0.012 0.32 0.26 1.48 1.48 1.01 1.02 0.42 0.64 1.33 495.75 * 0.012 0.34 0.28 1.79 1.79 1.32 1.33 0.45 0.71 1.68 496.10 * 0.012 0.36 0.29 2.14 2.14 1.67 1.68 0.47 0.78 2.07 496.49 * 0.012 0.37 0.31 2.53 2.53 2.06 2.07 0.50 PIPE NO. 5: 46 LF - 12"CP @ 1.09% OUTLET: 494.42 INLET: 494.93 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.07 0.14 495.07 * 0.012 0.11 0.10 0.15 0.15 0.11 ***** 0.14 0.13 0.20 495.13 * 0.012 0.15 0.13 0.21 0.21 0.15 ***** 0.20 0.20 0.24 495.17 * 0.012 0.19 0.16 0.25 0.25 0.19 ***** 0.24 0.26 0.28 495.21 * 0.012 0.22 0.18 0.29 0.29 0.22 ***** 0.28 0.32 0.31 495.24 * 0.012 0.24 0.20 0.37 0.37 0.24 ***** 0.31 0.39 0.35 495.28 * 0.012 0.26 0.21 0.52 0.52 0.26 ***** 0.35 0.45 0.38 495.31 * 0.012 0.28 0.23 0.74 0.74 0.28 ***** 0.38 0.52 0.55 495.48 * 0.012 0.30 0.25 1.02 1.02 0.51 0.55 0.40 0.58 0.85 495.78 * 0.012 0.32 0.26 1.33 1.33 0.83 0.85 0.43 0.64 1.21 496.14 * 0.012 0.34 0.27 1.68 1.68 1.19 1.21 0.46 0.71 1.59 496.52 * 0.012 0.36 0.29 2.07 2.07 1.58 1.59 0.48 ©2012 D. R.STRONG Consulting Engineers Inc. 37 Welman Plat Technical Information Report Renton,Washington BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#11 TO CB#2.bwp Surcharge condition at intermediate junctions Tailwater Elevation:496.35 feet Discharge Range:0.64 to 4.93 Step of 0.429 [cfs] Overflow Elevation:501.36 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 96 LF - 15"CP @ 3.35% OUTLET: 488.95 INLET: 492.18 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 497.18 BEND: 26 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.07 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.64 4.18 496.36 * 0.012 0.32 0.20 7.40 7.40 4.18 4.18 0.40 1.07 4.20 496.38 * 0.012 0.41 0.25 7.40 7.40 4.19 4.20 0.53 1.50 4.23 496.41 * 0.012 0.49 0.29 7.40 7.40 4.21 4.23 0.64 1.93 4.27 496.45 * 0.012 0.56 0.33 7.40 7.40 4.24 4.27 0.74 2.36 4.33 496.51 * 0.012 0.62 0.37 7.40 7.40 4.28 4.33 0.83 2.78 4.39 496.57 * 0.012 0.68 0.40 7.40 7.40 4.32 4.39 0.91 3.21 4.46 496.64 * 0.012 0.73 0.43 7.40 7.40 4.37 4.46 0.99 3.64 4.54 496.72 * 0.012 0.78 0.46 7.40 7.40 4.43 4.54 1.07 4.07 4.64 496.82 * 0.012 0.82 0.49 7.40 7.40 4.50 4.64 1.15 4.50 4.74 496.92 * 0.012 0.87 0.52 7.40 7.40 4.57 4.74 1.22 4.93 4.86 497.04 * 0.012 0.91 0.54 7.40 7.40 4.65 4.86 1.29 4.93 4.86 497.04 * 0.012 0.91 0.54 7.40 7.40 4.65 4.86 1.29 PIPE NO. 2: 120 LF - 15"CP @ 1.93% OUTLET: 492.18 INLET: 494.50 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 498.23 BEND: 86 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.21 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.60 1.89 496.39 * 0.012 0.31 0.22 4.18 4.18 1.88 1.89 0.40 1.00 1.92 496.42 * 0.012 0.40 0.28 4.20 4.20 1.91 1.92 0.53 1.40 2.00 496.50 * 0.012 0.47 0.33 4.23 4.23 1.96 2.00 0.65 1.80 2.09 496.59 * 0.012 0.54 0.37 4.27 4.27 2.03 2.09 0.75 2.20 2.21 496.71 * 0.012 0.60 0.41 4.33 4.33 2.13 2.21 0.85 2.60 2.36 496.86 * 0.012 0.65 0.45 4.39 4.39 2.23 2.36 0.95 3.00 2.53 497.03 * 0.012 0.70 0.48 4.46 4.46 2.36 2.53 1.05 3.40 2.72 497.22 * 0.012 0.75 0.52 4.54 4.54 2.51 2.72 1.15 3.81 2.94 497.44 * 0.012 0.79 0.55 4.64 4.64 2.67 2.94 1.25 4.21 3.18 497.68 * 0.012 0.84 0.58 4.74 4.74 2.85 3.18 1.35 4.61 3.44 497.94 * 0.012 0.88 0.61 4.86 4.86 3.06 3.44 1.45 4.61 3.44 497.94 * 0.012 0.88 0.61 4.86 4.86 3.06 3.44 1.45 PIPE NO. 3: 73 LF - 15"CP @ 1.25% OUTLET: 494.50 INLET: 495.41 INTYP: 5 JUNC NO. 3: OVERFLOW-EL: 498.97 BEND: 0 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.56 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.49 0.98 496.39 * 0.012 0.28 0.22 1.89 1.89 0.98 0.98 0.36 0.83 1.04 496.45 * 0.012 0.36 0.28 1.92 1.92 1.03 1.04 0.48 1.16 1.13 496.54 * 0.012 0.43 0.33 2.00 2.00 1.11 1.13 0.57 1.49 1.24 496.65 * 0.012 0.49 0.37 2.09 2.09 1.22 1.24 0.66 1.82 1.39 496.80 * 0.012 0.54 0.42 2.21 2.21 1.36 1.39 0.73 2.15 1.56 496.97 * 0.012 0.59 0.45 2.36 2.36 1.52 1.56 0.80 2.48 1.76 497.17 * 0.012 0.64 0.49 2.53 2.53 1.71 1.76 0.87 ©2012 D.R.STRONG Consulting Engineers Inc. 38 Welman Plat Technical Information Report Renton,Washington 2.81 2.00 497.41 * 0.012 0.68 0.52 2.72 2.72 1.93 2.00 0.94 3.15 2.26 497.67 * 0.012 0.72 0.56 2.94 2.94 2.17 2.26 1.00 3.48 2.56 497.97 * 0.012 0.76 0.59 3.18 3.18 2.45 2.56 1.06 3.81 2.88 498.29 * 0.012 0.79 0.62 3.44 3.44 2.75 2.88 1.12 3.81 2.88 498.29 * 0.012 0.79 0.62 3.44 3.44 2.75 2.88 1.12 PIPE NO. 4: 42 LF - 12"CP @ 1.01% OUTLET: 495.66 INLET: 496.09 INTYP: 5 JUNC NO. 4: OVERFLOW-EL: 499.68 BEND: 46 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.63 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.32 0.36 496.45 * 0.012 0.24 0.20 0.73 0.73 0.31 0.36 0.31 0.53 0.46 496.55 * 0.012 0.31 0.25 0.79 0.79 0.36 0.46 0.41 0.74 0.56 496.65 * 0.012 0.36 0.30 0.88 0.88 0.45 0.56 0.49 0.95 0.67 496.76 * 0.012 0.41 0.34 0.99 0.99 0.57 0.67 0.57 1.17 0.82 496.91 * 0.012 0.46 0.38 1.14 1.14 0.74 0.82 0.64 1.38 1.00 497.09 * 0.012 0.50 0.42 1.31 1.31 0.93 1.00 0.71 1.59 1.25 497.34 * 0.012 0.54 0.45 1.51 1.51 1.16 1.25 0.78 1.80 1.53 497.62 * 0.012 0.58 0.48 1.75 1.75 1.41 1.53 0.85 2.02 1.85 497.94 * 0.012 0.61 0.52 2.01 2.01 1.70 1.85 0.91 2.23 2.20 498.29 * 0.012 0.64 0.55 2.31 2.31 2.02 2.20 0.98 2.44 2.58 498.67 * 0.012 0.67 0.58 2.63 2.63 2.37 2.58 1.04 2.44 2.58 498.67 * 0.012 0.67 0.58 2.63 2.63 2.37 2.58 1.04 PIPE NO. 5: 33 LF - 12"CP @ 1.53% OUTLET: 496.09 INLET: 496.60 INTYP: 5 JUNC NO. 5: OVERFLOW-EL: 499.82 BEND: 29 DEG DIA/WIDTH: 2.0 Q-RATIO: 1.35 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.19 0.24 496.84 * 0.012 0.19 0.14 0.36 0.36 0.19 ***** 0.24 0.32 0.31 496.91 * 0.012 0.24 0.18 0.46 0.46 0.24 ***** 0.31 0.46 0.37 496.97 * 0.012 0.28 0.21 0.56 0.56 0.28 ***** 0.37 0.59 0.43 497.03 * 0.012 0.32 0.24 0.67 0.67 0.32 ***** 0.43 0.72 0.48 497.08 * 0.012 0.36 0.27 0.82 0.82 0.36 ***** 0.48 0.85 0.60 497.20 * 0.012 0.39 0.29 1.00 1.00 0.48 0.60 0.53 0.98 0.81 497.41 * 0.012 0.42 0.31 1.25 1.25 0.76 0.81 0.58 1.11 1.10 497.70 * 0.012 0.45 0.33 1.53 1.53 1.05 1.10 0.62 1.24 1.43 498.03 * 0.012 0.47 0.35 1.85 1.85 1.37 1.43 0.67 1.37 1.80 498.40 * 0.012 0.50 0.37 2.20 2.20 1.73 1.80 0.71 1.50 2.21 498.81 * 0.012 0.52 0.39 2.58 2.58 2.13 2.21 0.75 1.50 2.21 498.81 * 0.012 0.52 0.39 2.58 2.58 2.13 2.21 0.75 PIPE NO. 6: 89 LF - 12"CP @ 1.01% OUTLET: 496.60 INLET: 497.50 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.08 0.15 497.65 * 0.012 0.12 0.11 0.24 0.24 0.12 ***** 0.15 0.14 0.20 497.70 * 0.012 0.16 0.13 0.31 0.31 0.16 ***** 0.20 0.19 0.24 497.74 * 0.012 0.19 0.16 0.37 0.37 0.19 ***** 0.24 0.25 0.27 497.77 * 0.012 0.21 0.18 0.43 0.43 0.21 ***** 0.27 0.30 0.30 497.80 * 0.012 0.23 0.19 0.48 0.48 0.23 ***** 0.30 0.36 0.33 497.83 * 0.012 0.25 0.21 0.60 0.60 0.25 ***** 0.33 0.42 0.36 497.86 * 0.012 0.27 0.23 0.81 0.81 0.27 ***** 0.36 0.47 0.43 497.93 * 0.012 0.29 0.24 1.10 1.10 0.30 0.43 0.38 0.53 0.58 498.08 * 0.012 0.31 0.25 1.43 1.43 0.55 0.58 0.41 0.58 0.93 498.43 * 0.012 0.32 0.27 1.80 1.80 0.92 0.93 0.43 0.64 1.36 498.86 * 0.012 0.34 0.28 2.21 2.21 1.34 1.36 0.46 ©2012 D.R.STRONG Consulting Engineers Inc. 39 Welman Plat Technical Information Report Renton,Washington BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#7 TO CB#6.bwp Surcharge condition at intermediate junctions Tailwater Elevation:497.94 feet Discharge Range:0.48 to 0.48 Step of 0.48 [cfs] Overflow Elevation:498.23 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 1.04% OUTLET: 494.75 INLET: 495.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.48 2.96 497.96 * 0.012 0.29 0.24 3.19 3.19 2.95 2.96 0.39 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB#12 TO CB#8.bwp Surcharge condition at intermediate junctions Tailwater Elevation:498.29 feet Discharge Range:1.06 to 1.06 Step of 1.06 [cfs] Overflow Elevation:499.22 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 34 LF - 12"CP @ 1.00% OUTLET: 495.66 INLET: 496.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 1.06 2.36 498.36 * 0.012 0.44 0.36 2.63 2.63 2.32 2.36 0.61 ©2012 D. R.STRONG Consulting Engineers Inc. 40 Welman Plat Technical Information Report Renton,Washington SECTION VI SPECIAL REPORTS AND STUDIES No special reports or studies have been prepared as of the date of this report. ©2012 D.R.STRONG Consulting Engineers Inc. 41 Welman Plat Technical Information Report Renton,Washington SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS The following are required or have been obtained as part of the approval process: • NPDES — Notice of Intent • Building Permit — Detention Vault • Drainage Adjustment L07V0085 (included in this section) 2012 D. R.STRONG Consulting Engineers Inc. 42 Welman Plat Technical Information Report Renton,Washington . 141 . King Count Y. . Department of Development • and Environmental Services 900 Oakesdale Avenue Southwest • Renton, WA 98057-5212 206-296-6600 TTY 2.06-296-7217 • • • www klnaeo aw _ • • January 24,2008 - . • - MW Holdings • Site Development Associates, LLC 3502 "B"Street NW 10117 Main Street • Auburn, WA 98001 • Attn:Michael Feuerborn Bothell; WA 98011 Attn:Ken McIntyre, P.E. • RE: WeIman Subdivision 2005 KCSWDM Ad'ustrnent Re. uest ile No. L07V0085 Dear Applicant and Engineer: The Department of Development and Environmental Services. Division(LUSD), Site Engineering Review Section, has complelted.rey DES), Land Use Se request for the Welman Subdivision. You are requestingapproval Vices 2005King review of the adjustment County Surface Water Design Manual S ) oval for an adjustment at them the Natural Location. Our review of the information proud s to followingction i fi Discharge at 1• The proposed Welman subdivision is located at 18417 findings: 25 lot, 3.24 acre,proposed subdivision is filed 116` Avenue SE in Renton. The file number L06P0009. ander Land Use Services Division (LUSD) • 2. .The Welman subdivision is located in the Black Rise Drainage m r subject to the Conservation flow control and waterquali Bas • 2005 KCSWDM. BasicThe site is �' quirements of the • 3. Currently the site discharges to the. northwest, southwest • Discharge from the north portion of the site travels vii o and south. • . through a small swale, which drains ains into the Emerald Glenand flow to the northwest • to the west. This swale has been identified as a Class 4 Wetland. - Discharge from the southwest portion of _ subdivision, adjacent and southwest corner of the site. the site travels via overland flow to the Ave SE, where it Runoff then travels west down SE 186th 114th turns north and joins with the runoff that exits the site along to northwest corner. • Discharge from the southeast portion of the site the Runoff then travels west down SE 186thStreetcn travels via overland flow to the south. and joins with the runoff that exits the site along the northAve westcorner. it tions north - • • • I L07V0085 • January 24,2008 • Page 2 • • All runoff from the site is routed through an infiltrationfac' ' . Glen subdivision. The point where the three do n flow paths combine is less ility built for the Emerald wnstrear than 400 feet downstream of the site: There is no u s 4. The proposal is to collect most runo 'fi Pe runoff that enters the site. ff detention and water quality facility.located ate project corner of the propertect site and direct it to a single • allowed release would then be discharged to the existing Class 4 We The diversion would eliminate flows to-the southwest and south of the project. Wetland. Y The 5. No decorative ponds or shallow wells have been identified that wo proposed diversion. • uld be affected by the . 6. The Level One Downstream Analysis identified the • -• A drainage complaint at 18504 112th following drainage complaints; ' January 2, 1997 d Ave�SE (Parcel #3223059287) was made on uring construction of the Emerald Glen Infiltration Pond • • (EGIP). The EGIP was confirmed to experience an overflow even t construction. The EGIP final corrected plans show a plan revision to the under • which called for the replacement.of the sand-filter media athe Pond. pond and drilling of several bore-holes, and backfill of the hole bottom of the There have been no further drainage complaints regar'diri this s with drainfrock. . since.the.date of the plan revision. :. :, g specific facility • Five drainage complaints dating from December 20 describe the Ruddell Detention Pond , 1994 to January 30, 1997 (Facility#D90914) overflowing or backing_ up, inundating the adjacent roads and lots. improvement project on this facility, King County performed a capital and the nearby tributary pipe system several years ago. There have been no drainage complaints in this vicinity logged since January 3-0, 1997. Additionally, the site was visited on December 3, 2007. On this da area experienced a significant storm event which caused localized flooding region and approached a 100-yew desiY, the Puget Sound hydrologic models. The site t storm event in most local event basedln the was visited just a few hours after theP eak intensity of this stormhad passed, and there was no standing water surrounding vicinity and the Riddell pond appeared toserved be as a normal EGISin the or in the 7. A consolidation of facilities for the proposed subdivisiooperating level. n will long term maintenance. be more economical in • Based on these findings, we hereby approve this adjustment to allow on-site facility(draining to SE 312thStreet) with the following conditions: nsdiversion of runoff to o : • 1. The release rates for the detention facility will be based on the land from the site in all directions, naturally draining • • • L07170085 • i January 24, 2008 • Page 3• . • • . 2._The-_volume for_the detention-facility w111-be-based-on-ail-flows directed;to-the-facility--at-�- - - - full development under current zoning. undetained.flows that would bypass te p proposed subdi ease rate will be reduced by vis detention volume shall be sized using the Conservation flow control 1pn.drainage facilities. The any KCSWDM. The design.Technical Information Report shall state the factor of the 2005 selected and the basis of that determination. • s safety • 3: Water quality facilities must be sized based on the entirero 0 to the facilities including any required frontage improvemens sed subdivision draining 4. TheOnsite drainage facilities must be located in a public right-of--way, recreation space • tract with easement or storm drainage tract dedicated to Kin Co g unty. 5. Conveyance (from the R/D facility)in a closed s • Core Requirement#4. pipe system must be in accordance with • •6. Additional storm drainage requirements identified bySEPA apply to this project. .The applicant retains all rights and privile es - EPA or the plat hearing•review Section 1.4.. g afforded in If you have any ''� . . .. :... : : . .. .. . . .. . . - further questions regarding the S WDM variance or the design requirements, please contact Claire ionson at(206)296-6641. Sincerely, 01\11 ,fru.... -., Mai. . r_7-Gf,f,i . Jim Sanders, P.E. , Mark Bergam, P.E. Supervising Development Engineer • Site Engineering and Pla • • Building Services Division ing Supervisor Land Use Services Division cc: Curt Crawford, P.E., Supervising Engineer, Local Service s, KCDNR Whittaker, Engineer III, Engineering Review Section, LUSDTrishahBuil, Project/ProgramIIII, Planning Section, LUSD Jonson,P.E., Engineer Review Section, ' L I1/ 1C (:J ,_i lY/ 0 ( .-. 0 AUG 2 7 2001 • • /�j .,r Web Date: 11/16/2005 King K.C. D. t '� I`14 'y��I t' aryl{ County E.S. �r r(yr`` � _ U,4i , Department of Development and Environmental Services 900 Oakesdale Avenue Southwest .r./.47/1L, r 7L �7 r. A D'34 S. T A� , ,r Vit.,- axe, �: •- - s Renton, r : ; Washington 98055 1219 ,..,.- = ?,Y hi. -s ...` t:,:.. 206-296-6600 a a :, i5�i a.1 } TTY 206-296-7217 _ ' , ' �.: "� F:���.., .. • For alternate formats, call 206-2g6-6600.Y' Project Name: Weect nN Subdivision DDES Project File No: L06130009 L , `'O Project Address: DDES Engineer/Planner Name; Trish Bull v 10 +" 18417 116th Avenue SE; Renton, WA Design Engineer. Applicant/Agent**: /116th: Ren McIntyre, P.E. Phone: Phone: Sin (425) 486-6533 Michael Feuerborn 9 lure of Design En.'ne: . (253) 859 9697 . Date: Signature of Applicant/Agent: Date: EngineeringFirm ���Z Name: Address: Site Development 'Also City, State,ZIP: ciates, LLC 3502 ^B^ Address: City, State, ZIP: W Auburn, WA 98001 Street Di INSTRUCTIONS TO APPLICANT/DESIGN ENGINEER: 10117 Main Street Bothell, WA 98011 Please be sure to include all materials (Level One Downstream Analysis, Certification of A maps)that may assist in complete review and consideration of this adjustment request. Failure to rovi information may result in delayed processing or denial of request. Please submit two com.fet�o•iesof Status,this re•sketces, photos, and application form and aoolicable fee to the Department of Development and Environmental Services S de all pertinent Renton, WA 98055-1219. For more information,contact Mark Bergam, P. 206-296-7270, es of re.uest 9 E., at 206-2g6-.7270 � 00 Oakesdale Ave. SW, **Applicant/Agent is the indivi individual financially responsible for ali fees s _igiiw ¢ um `? �ysEgy ' rNzT.Z '�" : yt=y-:r , n'f b_DESCRIPTION OF ADJUSTMENT REQUEST: ❑Standardd Complex ❑ Experimental ❑Blanket ❑Pre-appIiestjon APPLICABLE VERSION KCSWDM: 0 1990 (11/95)* 0 1998 (9/98) APPLICABLE SECTION(S) OF STANDARDS: *(Note: the term 'variance'replaced by ❑2005 (1/05) 'adjustment) Core Requirement #1 JUSTIFICATION PER KCSWDM SECTION ION 1.4 2' 0 See attachments listed below. Both existing downstream flow, paths combine within 1/4 mile from the site, so the project lies within a single threshold discharge basin. See attached justification. AUTHORIZATION SIGNATURES: i,E i tKMINATION: ❑Approval a onditional 0 DNRP/WLRD Approval Signed:: Approval(see below) ❑Denial DDES Staff Recommendation Signed: �" Date: Conditions ofA ✓rr.L.� , (Experimental&B►anket only) Approval: % Date: r. See attached memo dated: D S,LUSOEn.'. ng Review Supervisor: DDES DIRECTOR/DESIGNEE: S.ned: DDES,BS., .ite gineertn NW Date: �' / 9 Planning Supervisor �.. Fie Signed: �1 E/ "1. .,G Date:j' Check out the DDES Web site at www. �� SuiiWaterDesManRegStdsAdiRegFORM.doc 1I7@tr0/fC. py/do/� le-info-surrva-adj.pdf 11/16/2005 Page 1 of 1 SECTION VIII ESC PLAN ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design meets the nine minimum requirements: 1. Clearing Limits — Areas to remain undisturbed shall be delineated with a high- visibility plastic fence prior to any site clearing or grading. 2. Cover Measures — Disturbed Site areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection — Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. Traffic Area Stabilization — A stabilized construction entrance will be located at the point of ingress/egress. 5. Sediment Retention — One sediment trap will be utilized for sediment retention. The sediment trap is designed per Section D.3.5.2 of the KCSWDM, which requires 2080 s.f. of surface area per cfs of inflow calculated using the KCRTS 15-minute time steps to analyze the developed Site condition. The catchment area tributary to the sediment trap is 2.70 ac. and the 2-year flow rate is calculated at 1.05 cfs. The required surface area is 2,184 s.f. and the area provided is 2,500 s.f. The KCRTS analysis is included in this section. See Sheet C4 of the Plans for sediment trap details. 6. Surface Water Control — Surface water control will be provided by interceptor swales. 7. Dewatering Control — Not Applicable to this Site. 8. Dust Control — Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. 9. Flow Control — Runoff collected in the sediment trap will discharge to the Class 4 wetland. 2012 D. R.STRONG Consulting Engineers Inc. 43 Welman Plat Technical Information Report Renton,Washington KCRTS ANALYSIS FOR SEDIMENT TRAP teLand Use Summar} 1, o pf k -Area 2 G Till Forest 0.00 acres Till Pasture 0.00 acres Till Grass 0.50 acres Outwash Forest 0.00 acres 1 Outwash Pasture 0.00 acres 1 Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 2.20 acres Total 1 2.70 acres Scale Factor : 1.00 15-Min Reduced Edit Flow Paths ( 1 1 Time Series: 15-MIN TESCI »I I Compute Time Series I ti Modify User Input _ I \ File for computed Time Series [.TSF] ti Flow Frequency Analysis Time Series File: 15-min tesc.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Frequency Analysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 1. 05 6 8/27/01 18:00 2.85 1 100. 00 0.990 0.732 8 9/17/02 17:45 2.09 2 25.00 0. 960 2.09 2 12/08/02 17: 15 1.44 3 10. 00 0.900 0.844 7 8/23/04 14 :30 1.21 4 5.00 0.800 1. 14 5 10/28/04 16:00 1.14 5 3. 00 0.667 1.21 4 10/27/05 10:45 1.05 6 2.00 0.500 1. 44 3 10/25/06 22: 45 0.844 7 1.30 0.231 2.85 1 1/09/08 6:30 0.732 8 1. 10 0.091 Computed Peaks 2. 60 50.00 0.980 ©2012 D.R.STRONG Consulting Engineers Inc. 44 Welman Plat Technical Information Report Renton,Washington SWPPS PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP's listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash-up waters from water-based paints in sanitary sewer; disposing of wastes from oil-based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 3. Building demolition: Protect stormwater drainage system from sediment-laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP will be submitted prior to pre-construction meeting. ©2012 D.R.STRONG Consulting Engineers Inc. 45 Welman Plat Technical Information Report Renton,Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Bond Quantity Worksheet— to be submitted prior to final engineering approval. The Stormwater Facility Summary Sheet is included in this section. See Figure 7 for facility sketch. A draft Declaration of Covenant for reduced impervious surface BMP will be provided prior to final approval. 2012 D. R.STRONG Consulting Engineers Inc. 46 Welman Plat Technical Information Report Renton,Washington STORMWATER FACILITY SUMMARY SHEET Development Welman Plat Date May 7, 2012 Location 18417 116th Ave SE, Renton, Washington ENGINEER DEVELOPER Name Maher A. Joudi, P.E. Name Firm D. R. STRONG Consulting Firm Harbour Homes LLC Engineers, Inc. Address 10604 NE 38th Place, #101 Address 1441 North 34th Street, Suite 200 Kirkland, WA 98033 Seattle, WA 98103 Phone (425) 827-3063 Phone (206) 315-8130 Developed Site: 3.33 acres Number of lots 21 Number of detention facilities on site: Number of infiltration facilities on site: ponds ponds 1 vaults vaults tanks tanks Flow control provided in regional facility (give location) No flow control required Exemption number Downstream Drainage Basins Immediate Major Basin Basin Black River Green River Number & type of water quality facilities on site: biofiltration swale (regular/wet/ or continuous inflow?) sand filter (basic or large?) sand filter, linear (basic or large?) ADS BayFilter combined detention/WQ pond sand filter vault (basic or large?) combined detention/wetvault stormwater wetland compost filter wetpond (basic or large?) filter strip 1 wetvault flow dispersion pre-settling pond farm management plan flow-splitter catchbasin landscape management plan oil/water separator (baffle or coalescing plate?) ©2012 D.R.STRONG Consulting Engineers Inc. 47 Welman Plat Technical Information Report Renton,Washington catch basin inserts: Manufacturer pre-settling structure: Manufacturer DESIGN INFORMATION INDIVIDUAL BASIN RDIN Bypass Water Quality design flow Water Quality treated volume Drainage basin(s) Onsite area 2.88 0.10 Offsite area 0.35 Type of Storage Facility Vault Live Storage Volume (required) 35,805 Predev Runoff Rate 2-year 0.121 10-year 0.202 100-year 0.339 Developed Runoff Rate 2-year 0.623 10-year 0.747 100-year 1.25 Type of Restrictor Frop-Tee Size of orifice/restriction No. 1 1.09 No. 2 1.44 No. 3 ©2012 D.R.STRONG Consulting Engineers Inc. 48 Welman Plat Technical Information Report Renton,Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL See attached excerpts from the 2005 King County Surface Water Design Manual. n 2012 D. R.STRONG Consulting Engineers Inc. 49 Welman Plat Technical Information Report Renton,Washington APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 3- DETENTION TANKS AND VAULTS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is blocked Vents free of debris and sediment at any point with debris and sediment. Debris and Sediment Accumulated sediment depth exceeds 10%of All sediment and debris removed the diameter of the storage area for%length of from storage area. storage vault or any point depth exceeds 15%of diameter. Example:72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank. Joints Between Any crack allowing material to be transported into All joint between tank/pipe sections Tank/Pipe Section facility. are sealed . Tank Pipe Bent Out of Any part of tank/pipe is bent out of shape more Tank/pipe repaired or replaced to Shape than 10%of its design shape. design. Vault Structure Damage to Wall, Cracks wider than%-inch and any evidence of Vault replaced or repaired to design Frame,Bottom, soil particles entering the structure through the specifications. and/or Top Slab cracks,or maintenance inspection personnel determines that the vault is not structurally sound. Damaged Pipe Joints Cracks wider than Y.-inch at the joint of any No cracks more than V4-inch wide at inlet/outlet pipe or any evidence of soil particles the joint of the inlet/outlet pipe. entering the vault through the walls. Manhole Cover Not in Place Cover is missing or only partially in place.Any Manhole is closed. open manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. Not Working maintenance person with proper tools.Bolts into frame have less than%inch of thread(may not apply to self-locking lids.) Cover Difficult to One maintenance person cannot remove lid after Cover can be removed and Remove applying 80lbs of lift. Intent is to keep cover from reinstalled by one maintenance sealing off access to maintenance. person. Ladder Rungs Unsafe King County Safety Office and/or maintenance Ladder meets design standards. person judges that ladder is unsafe due to Allows maintenance person safe missing rungs,misalignment,rust,or cracks. access. Large access Gaps,Doesn't Cover Large access doors not flat and/or access hole Doors closes flat and covers access • doors/plate Completely not completely covered. NOTE however that hole completely. grated doors are acceptable. Lifting Rings Missing, Lifting rings not capable of lifting weight of door Lifting rings sufficient to remove lid. Rusted or lid. 1/24/2005 2005 Surface Water Design Manual—Appendix A A-4 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 4- CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed General Trash and Debris Distance between debris build-up and bottom of All trash and debris removed. (Includes Sediment) orifice plate is less than 1.5 feet. Structural Damage Structure is not securely attached to manhole Structure securely attached to wall wall and outlet pipe structure should support at and outlet pipe. least 1,000 lbs of up or down pressure. Structure is not in upright position(allow up to Structure in correct position. 10%from plumb). Connections to outlet pipe are not watertight and Connections to outlet pipe are water show signs of rust. tight;structure repaired or replaced and works as designed. Any holes—other than designed holes—in the Structure has no holes other than structure. designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and down easily and maintenance person. is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Gate is rusted over 50%of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and works as missing,out of place,or bent orifice plate. designed. Obstructions Any trash,debris,sediment,or vegetation Plate is free of all obstructions and blocking the plate. works as designed. Overflow Pipe Obstructions Any trash or debris blocking(or having the Pipe is free of all obstructions and potential of blocking)the overflow pipe. works as designed. Manhole See"Detention Tanks See"Detention Tanks and Vaults"Table No.3 See"Detention Tanks and Vaults" and Vaults" Table No.3 • 2005 Surface Water Design Manual–Appendix A 1/24/2005 A-5 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 5-CATCH BASINS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash&Debris Trash or debris of more than 1/2 cubic foot which No Trash or debris located (Includes Sediment) is located immediately in front of the catch basin immediately in front of catch basin opening or is blocking capacity of the basin by opening. more than 10%. Trash or debris(in the basin)that exceeds 1/3 the No trash or debris in the catch depth from the bottom of basin to invert the basin. lowest pipe into or out of the basin. Trash or debris in any inlet or outlet pipe blocking Inlet and outlet pipes free of trash or more than 1/3 of its height. debris. Dead animals or vegetation that could generate No dead animals or vegetation odors that could cause complaints or dangerous present within the catch basin. gases(e.g.,methane). Deposits of garbage exceeding 1 cubic foot in No condition present which would volume. attract or support the breeding of insects or rodents. Structure Damage to Corner of frame extends more than 3/4 inch past Frame is even with curb. Frame and/or Top curb face into the street(If applicable). Slab Top slab has holes larger than 2 square inches Top slab is free of holes and cracks. or cracks wider than'A inch(intent is to make sure all material is running into basin). Frame not sitting flush on top slab,i.e., Frame is sitting flush on top slab. separation of more than 1/4 inch of the frame from the top slab. Cracks in Basin Cracks wider than 1/2 inch and longer than 3 feet, Basin replaced or repaired to design Walls/Bottom any evidence of soil particles entering catch standards. basin through cracks,or maintenance person judges that structure is unsound. Cracks wider than 1/2 inch and longer than 1 foot No cracks more than 1/4 inch wide at at the joint of any inlet/outlet pipe or any the joint of inlet/outlet pipe. evidence of soil particles entering catch basin through cracks. Settlement/ Basin has settled more than 1 inch or has rotated Basin replaced or repaired to design Misalignment more than 2 inches out of alignment. standards. Fire Hazard Presence of chemicals such as natural gas,oil No flammable chemicals present. and gasoline. Vegetation Vegetation growing across and blocking more No vegetation blocking opening to than 10%of the basin opening. basin. Vegetation growing in inlet/outlet pipe joints that No vegetation or root growth is more than 6 inches tall and less than 6 inches present. apart. Pollution Nonflammable chemicals of more than''/2 cubic No pollution present other than foot per three feet of basin length. surface film. Catch Basin Cover Cover Not in Place Cover is missing or only partially in place.Any Catch basin cover is closed open catch basin requires maintenance. Locking Mechanism Mechanism cannot be opened by on Mechanism opens with proper tools. Not Working maintenance person with proper tools.Bolts into frame have less than%inch of thread. Cover Difficult to One maintenance person cannot remove lid after Cover can be removed by one Remove applying 80 lbs.of lift;intent is keep cover from maintenance person. sealing off access to maintenance. Ladder Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design standards and misalignment,rust,cracks,or sharp edges. allows maintenance person safe access. 1/24/2005 2005 Surface Water Design Manual—Appendix A A-6 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 5-CATCH BASINS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed Metal Grates Unsafe Grate Grate with opening wider than 7/8 inch. Grate opening meets design (If Applicable) Opening standards. Trash and Debris Trash and debris that is blocking more than 20% Grate free of trash and debris. of grate surface. Damaged or Missing. Grate missing or broken member(s)of the grate. Grate is in place and meets design standards. NO. 6-DEBRIS BARRIERS (E.G., TRASH RACKS) Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed. General Trash and Debris Trash or debris that is plugging more than 20% Barrier clear to receive capacity of the openings in the barrier. flow. Metal Damaged/Missing Bars are bent out of shape more than 3 inches. Bars in place with no bends more Bars. than 3/<inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50% Repair or replace barrier to design deterioration to any part of barrier. standards. NO. 7-ENERGY DISSIPATERS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed. External; Rock Pad Missing or Moved Only one layer of rock exists above native soil in Replace rocks to design standards. Rock area five square feet or larger,or any exposure of native soil. Dispersion Trench Pipe Plugged with Accumulated sediment that exceeds 20%of the Pipe cleaned/flushed so that it Sediment design depth. matches design. Not Discharging Visual evidence of water discharging at Trench must be redesigned or Water Properly concentrated points along trench(normal rebuilt to standards. condition is a"sheet flow"of water along trench). Intent is to prevent erosion damage. Perforations Plugged. Over 1/2 of perforations in pipe are plugged with Clean or replace perforated pipe. debris and sediment. Water Flows Out Top Maintenance person observes water flowing out Facility must be rebuilt or of"Distributor"Catch during any storm less than the design storm or redesigned to standards. Basin. its causing or appears likely to cause damage. Receiving Area Over- Water in receiving area is causing or has No danger of landslides. Saturated potential of causing landslide problems. Internal: Manhole/Chamber Worn or Damaged Structure dissipating flow deteriorates to 1/2 or Replace structure to design Post.Baffles,Side of original size or any concentrated worn spot standards. Chamber exceeding one square foot which would make structure unsound. 2005 Surface Water Design Manual—Appendix A 1/24/2005 A-7 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 8- FENCING Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed General Missing or Broken Any defect in the fence that permits easy entry to Parts in place to provide adequate Parts a facility. security. Erosion Erosion more than 4 inches high and 12-18 No opening under the fence that inches wide permitting an opening under a fence. exceeds 4 inches in height. Wire Fences Damaged Parts Post out of plumb more than 6 inches. Post plumb to within 11/2 inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence(including post,top rails,and Fence is aligned and meets design fabric)more than 1 foot out of design alignment. standards. Missing or loose tension wire. Tension wire in place and holding fabric. Missing or loose barbed wire that is sagging Barbed wire in place with less than more than 21/2 inches between posts. 3/4 inch sag between post. Extension arm missing,broken,or bent out of Extension arm in place with no shape more than 1%inches. bends larger than Y4 inch. Deteriorated Paint or Part or parts that have a rusting or scaling Structurally adequate posts or parts Protective Coating condition that has affected structural adequacy. with a uniform protective coating. Openings in Fabric Openings in fabric are such that an 8-inch No openings in fabric. diameter ball could fit through. NO. 9- GATES Maintenance • Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed General Damaged or Missing Missing gate or locking devices. Gates and Locking devices in place. Members Broken or missing hinges such that gate cannot Hinges intact and lubed.Gate is be easily opened and closed by a maintenance working freely. person. Gate is out of plumb more than 6 inches and Gate is aligned and vertical. more than 1 foot out of design alignment. Missing stretcher bar,stretcher bands,and ties. Stretcher bar,bands,and ties in place. Openings in Fabric See"Fencing"Table No.8 See"Fencing"Table No.8 1/24/2005 2005 Surface Water Design Manual—Appendix A A-8 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 10- CONVEYANCE PIPES AND DITCHES Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Pipes Sediment&Debris Accumulated sediment that exceeds 20%of the Pipe cleaned of all sediment and diameter of the pipe. debris. Vegetation Vegetation that reduces free movement of water All vegetation removed so water through pipes. flows freely through pipes. Damaged Protective coating is damaged;rust is causing Pipe repaired or replaced. more than 50%deterioration to any part of pipe. Any dent that decreases the cross section area Pipe repaired or replaced. of pipe by more than 20%. Open Ditches Trash&Debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sedirhent that exceeds 20%of the Ditch cleaned/flushed of all design depth. sediment and debris so that it matches design. Vegetation Vegetation that reduces free movement of water Water flows freely through ditches. through ditches. Erosion Damage to See"Detention Ponds"Table No. 1 See"Detention Ponds"Table No. 1 Slopes Rock Lining Out of Maintenance person can see native soil beneath Replace rocks to design standards. Place or Missing(If the rock lining. Applicable). NO. 11 -GROUNDS (LANDSCAPING) Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed General Weeds Weeds growing in more than 20%of the Weeds present in less than 5%of (Nonpoisonous,not landscaped area(trees and shrubs only). the landscaped area. noxious) Safety Hazard Any presence of poison ivy or other poisonous No poisonous vegetation present in vegetation. landscaped area. • Trash or Litter Paper,cans,bottles,totaling more than 1 cubic Area clear of litter. foot within a landscaped area(trees and shrubs only)of 1,000 square feet. Trees and Shrubs Damaged Limbs or parts of trees or shrubs that are split or Trees and shrubs with less than 5% broken which affect more than 25%of the total of total foliage with split or broken foliage of the tree or shrub. limbs. Trees or shrubs that have been blown down or Tree or shrub in place free of injury. knocked over. Trees or shrubs which are not adequately Tree or shrub in place and supported or are leaning over,causing exposure adequately supported;remove any of the roots. dead or diseased trees. 2005 Surface Water Design Manual—Appendix A 1/24/2005 A-9 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 12-ACCESS ROADS Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed General Trash and Debris Trash and debris exceeds 1 cubic foot per 1,000 Roadway free of debris which could square feet(i.e.,trash and debris would fill up damage tires. one standards size garbage can). Blocked Roadway. Debris which could damage vehicle tires(glass Roadway free of debris which could or metal). damage tires. Any obstruction which reduces clearance above Roadway overhead clear to 14 feet road surface to less than 14 feet. high. Any obstruction restricting the access to a 10-to Obstruction removed to allow at 12-foot width for a distance of more than 12 feet least a 12-foot access. or any point restricting access to less than a 10- foot width. Road Surface Settlement, Potholes, When any surface defect exceeds 6 inches in Road surface uniformly smooth with Mush Spots,Ruts depth and 6 square feet in area. In general,any no evidence of settlement,potholes, surface defect which hinders or prevents mush spots,or ruts. maintenance access. Vegetation in Road Weeds growing in the road surface that are more Road surface free of weeds taller Surface than 6 inches tall and less than 6 inches tall and than 2 inches. less than 6 inches apart within a 400-square foot area. Modular Grid Build-up of sediment mildly contaminated with Removal of sediment and disposal Pavement petroleum hydrocarbons. in keeping with Health Department recommendations for mildly contaminated soils or catch basin sediments. Shoulders and Erosion Damage Erosion within 1 foot of the roadway more than 8 Shoulder free of erosion and Ditches inches wide and 6 inches deep. matching the surrounding road. Weeds and Brush Weeds and brush exceed 18 inches in height or Weeds and brush cut to 2 inches in hinder maintenance access. height or cleared in such a way as to allow maintenance access. 1/24/2005 2005 Surface Water Design Manual—Appendix A A-10 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 17-WETVAULT Maintenance Defect or Problem Condition When Maintenance is Needed Recommended Maintenance to Component Correct Problem Vault Area Trash/Debris Trash and debris accumulated in vault(includes Remove trash and debris. Accumulation floatables and non-floatables). Sediment Sediment accumulation in vault bottom exceeds Remove sediment from vault. Accumulation the depth of the sediment zone plus 6 inches. Ventilation Ventilation area blocked or plugged Remove or clear blocking material from ventilation area. A specified% of the vault surface area must provide ventilation to the vault interior(see p.6-82 for required%). Vault Structure Damage to Wall, Cracks wider than%2-inch and any evidence of Vault replaced or repaired to design Frame,Bottom, soil particles entering the structure through the specifications. and/or Top Slab cracks,or maintenance inspection personnel determines that the vault is not structurally sound. Damaged Pipe Joints Cracks wider than'/2-inch at the joint of any No cracks more than''h-inch wide at inlet/outlet pipe or any evidence of soil particles the joint of the inlet/outlet pipe. entering the vault through the walls. Baffles Damaged/Defective Baffles corroding,cracking,warping and/or Repair or replace baffles to showing signs of failure as determined by specifications. maintenance/inspection staff. Inlet/Outlet Damaged Pipes Inlet/outlet piping damaged or broken and in Pipe repaired and/or replaced. need of repair. Trash/Debris Trash and debris accumulated in pipe or Remove trash and debris. Accumulation inlet/outlet(includes floatables and non- floatables). Access Cover Damaged/Not Cover cannot be opened or removed,especially Pipe repaired or replaced to proper Working by one person. working specifications. Access Ladder Damaged Ladder is corroded or deteriorated,not Ladder replaced or repaired to functioning properly,missing rungs,has cracks specifications,and is safe to use as and/or misaligned. Confined space warning sign determined by inspection personnel. missing. Replace sign warning of confined space entry requirements. • 1/24/2005 2005 Surface Water Design Manual—Appendix A A-14 APPENDICES ©2012 D.R.STRONG Consulting Engineers Inc. 50 Welman Plat Technical Information Report Renton,Washington APPENDIX A BOND QUANTITY WORKSHEET ©2012 D.R.STRONG Consulting Engineers Inc. 51 Welman Plat Technical Information Report Renton,Washington APPENDIX B OFFSITE ANALYSIS BY SITE DEVELOPMENT ASSOCIATES, LLC ©2012 D. R.STRONG Consulting Engineers Inc. 52 Welman Plat Technical Information Report Renton,Washington • • • • -- • Kai••• :.: . .�:�.. to #{ f : lNELMAN Site.E e :E.Jopme:nfi Assoeio f est:LLC l O i e S w s • ,; , tt . . ._... :•.:• . . : arv�},,tis �{L:evel One Do�.vns#re • .• :::::::.: : f . Project Location: • 18417 116th Avenue SE Renton, WA Prepared For: • Dreamcraft Homes 3502"B"Street NW Auburn, WA 98001 (253) 859-9697 • Prepared by: Site Development Associates, LLC Ken McIntyre, P.E. 10117 Main Street Bothell, WA 98011 Date: June 13, 2007 Project Number: 136-005-05 ,,=J, •WAS _ g � Vii;/ Ie� 0 • 3g018 4o s OVAL��` X•I'ES I./ b/ ,. ..A; • WELMAN SUBDIVISION Level One Downstream Analysis Project Location: 18417 116th Avenue SE Renton, WA Prepared For: Dreamcraft Homes 3502"B"Street NW Auburn, WA 98001 (253) 859-9697 Prepared by: Site Development Associates, LLC Ken McIntyre, P.E. 10117 Main Street Bothell, WA 98011 • Date: June 13,2007 Project Number: 136-005-05 WELMAN SUBDIVISION Level One Downstream Analysis • 7 TABLE OF CONTENTS Project Description 1 Core Requirement No. 1 1 Core Requirement No. 2 1 Core Requirement No. 3 4 Core Requirement No. 4 4 Core Requirement No. 5 4 I Core Requirement No. 6 4 Core Requirement No. 7 4 I Core Requirement No. 8 4 Special Requirement No. 1 4 I Special Requirement No. 2 4 Special Requirement No. 3 5 Ill Special Requirement No. 4 5 Special Requirement No. 5 5 IAppendix A— Figures Appendix B— Downstream Analysis IAppendix C— Calculations Appendix D— Operations and v"aii tci ids ice Manual u II II u WELMAN SUBDIVISION iLevel One Downstream Analysis Project Description ..,._.___ The purpose ofthis report is to present a Level-one downstream analysis of Welman Subdivision in accordance with King County requirements. The proposed project will subdivide the site into 25 single-family housing lots. In addition to the roadways, the proposed ' project will include all utilities and other improvements necessary to accommodate the new lots. Detention will be provided for in a vault on site. Water quality will be done with a wet vault under the proposed detention vault. This report addresses the storm drainage issues associated with the subdivision of the property, and construction of the new homes and access roads. The design standards addressed for this report are contained in King County Code and the King County Surface Water Design Manual. Review of the 8 Core Requirements and 5 Special Requirements of the 1998 King County Surface Water Design Manual SDA has reviewed the Core and Special Requirements in Chapter 1 of the King County Surface Water Design Manual, I and addresses each of the requirements as follows: Core Requirement No. 1 — Discharge at Natural Location Currently the site discharges to the northwest and southwest corners of the site. small swale, which drains into the Emerald Glen subdivision, adjacent and tothe west. Tg s swale h shwest been ident f eis throud asa a Class 4 Wetland. Discharge from the southwest corner of the site travels via overland flow to the southwest corner of the site. From here stormwater travels via overland flow through an adjacent residential lot in the Walhaven Plat, before entering the conveyance system located within SE 186th Street. From here runoff travels west down SE 186th Street to 114th Avenue SE, where it turns north and joins with the runoff that exits the site along the northwest corner. Runoff is I then routed through a stormwater detention facility built for the Emerald Glen subdivision. This is a multiple natural discharge and a single threshold discharge area. I Runoff from the developed site will be collected and conveyed via a tight line system to a detention vault located in the northwest corner of the site. The runoff will exit this vault and be conveyed to the northwest property line and discharged into the existing Class 4 Wetland. The proposed project will discharge stormwater from the entire site to the northwest corner of the property. A drainage adjustment will be requested for this change. IIICore Requirement No. 2 -- Offsite Analysis ii Task 1: Define and Map Study Area 111 This project is located west of 116th Avenue SE, in unincorporated King County, Washington. The property address is I18417 116th Avenue SE, Renton. The project consists of one tax parcel; 3223059033. Thero ert is approx 3.24 acres. The property will be divided into 25 residential lots. All of these lots will gain access from a newly Imately constructed public road that runs through the subdivision; one access on 116h Ave SE. IIIThe properties to the north, west, and south are zoned R-8. The property adjacent and to the west, known as Emerald Glen, was platted in 1996, and is fully built out. The properties to the south, along SE 186th Street, have into single-family residential lots. To the north, there are some larger, undeveloped parcels, which are also zoned R-8. IIThe properties to the east of 116th Ave SE are zoned R-6, and are partially developed, with several homes on large parcels. The analysis of the basin boundary indicates that the project is in the Black River Drainage Basin. See Figure 1 for a 1 vicinity map of the project and Figure 2 in (both in Appendix A)for an existing site survey of the project. Figure 3 in II WELMAN SUBDIVISION u Level One Downstream Analysis 1 Appendix A shows the proposed site plan for the development. There is an existing houses and associated outbuildings located on several parcels. All of the existing structures are to be demolished during plat construction. g ask 2: Review all Available Information on the Study Area Critical Drainage Area Map • Black River Drainage Basin • Duwamish—Green River Watershed • Duwamish-Green WRIA (9) Flood plain/floodway(FEMA) Maps • There are no mapped floodplains in the immediate area per the available FEMA map. The site is located in Zone X per the Flood Insurance Rate Map (FIRM) map number 53033C0991 F. See Figure 5 in Appendix A for I a copy of the FIRM map. Sensitive Areas I • Wetlands — Recent site investigations conducted indicate that there is a wetland located on the site. A wetland report, completed in April 2005 by Habitat Technologies, was provided to us by the property owner. The wetland report indicates that a small Category 4 Wetland is present on the site. Altmann Oliver Associates (AOA)was retained to conduct a field visit, and to review the wetland report and address the wetland classification and provide guidance related to wetland buffers and potential impact and mitigation alternatives. It appears that the wetland could be filled,with mitigation measures on site (creation of additional wetlands), and that the buffer width could be reduced to 25'with buffer enhancements. From our site visit, there does not appear to be any streams, steep slopes, or wildlife habitat on the site • Streams and 100 Year Flood Plains—There are no streams or floodplains Imapped on site. • Erosion Hazard Areas—There are no mapped erosion hazard areas on site. 1 • Landslide Hazard Areas—There are no landslide hazard areas mapped in this area. • Seismic Hazard Areas—This site is not within in a mapped seismic hazard area. III • Coal Mine Hazard Areas— None mapped in this area. U.S. Department of Agriculture, King County Soils Survey I • The soil on the site is Ground Moraine Deposits (Qgt). Figure 4 in Appendix A presents the soil survey for the project area. Flow Control Applications Map 0 • The site is located in a Level 2 area of Flow Control. Water Quality Appilcations ilcations Map I • The site is located in a Basic Water Quality Treatment Area. Landslide Hazard Drainage Area Map • The site is not located in a landslide hazard drainage area. II I I WELMAN SUBDIVISION Level One Downstream Analysis • • Task 3: Field Inspect the Study Area A representative of Site Development Associates, LLC (SDA) made a site visit to the property on December 15, 2005. The weather conditions were dry, 35 degrees and cloudy. The field investigation covered approximately 1/4 mile downstream of the site. Task 4: Describe the Drainage System, and its Existing and Predicted Problems Upstream Drainage Analysis: This site is located near the edge of the Black River Drainage Basin. There is no upstream runoff that enters the site. IOn-Site Drainage Analysis: The property is approximately 3.24 acres in size, and has approximately 400 LF of frontage on 116th Avenue SE. The site generally slopes to the north and west. The southern half of the site is on a relatively flat, grassy plateau and I contains an existing house, a garage, and a carport, which are located in the center of the property. The northern half of the property is also characterized by largely grass areas, and slopes down from the southern plateau toward a small swale, which drains into the subdivision adjacent and to the west. This swale has been identified as a Class 4 Wetland, and is addressed in the following pages of this report. The majority of the site is grassy varying size throughout the site. Please see Figures 2 & 3 for aerial views and general topographical ered nforscattmat otn. Thof e property appears to be frequently maintained, and the grass mowed regularly. IDownstream Drainage Analysis: The project site and surrounding vicinity was visited on July 14, no precipitation having recently occurred. No surface flow was visible b e u ring th06. The e site ser pin A brief description of dry,he I and downstream drainage path is included below. See the Appendix B for an off-site Analysis Drainage System Table and map. The majority of the site drains towards the northwest to a swale classified as a Class 4 wetland, located near the western boundary of the site. These wetlands drain offsite to the west(see photo#'s 1 &2)where they drain into the enclosed drainage system for the Emerald Glen Plat. This system flows southwesterly SE 185th Place, to 114th Ave. SE, which lies approximately 400 feet downstream of the project site. From this point, runoff continues southerly along 114th Ave. SE for a short distance, then turns westerly(see photo#3), beneath an access driveway, before entering a detention facility(see photo#4 a Ithe site.. The outfall from this pond could not be located, but from the regional topography,pproximaeand from a pry 625 feet ior ndrainage of investigation, it appears that the pond outfalls to the west. A 10' drainage easement exists along the back of the lots adjacent to SE 186th Street. It is likely that this easement contains a conveyance pipe, however, no pipe could be located. It appears that flow continues westerly from the detention facility to 112th Ave. SE. Upon reaching 112th Ave. SE, the runoff is intercepted by the public _t om draine system, anisa catch basin which lies just north of SE 184th PI. From this catch bas nr runoffs conveyed westerly to a sedconortherly nd, larger 1 detention facility (see photo#'s 5 & 6), approximately 1,400 feet downstream of the project site. The outfall from this detention pond appears to be at the southwest corner of the pond, and runoff appears this outfall (see photo#7). The remainder of the downstream flowpath is beyond the %mi e conveyedistanced required for th sm m analysis. III I III WELMAN SUBDIVISION Level One Downstream Analysis II IDrainage Complaints: Review of the King County Drainage complaints indicatesthat there are two relevant drainage complaints recorded I downstream of the site within the last 10 years. These complaints are included in Appendix B of this report. Task 5: Addressing Mitigation of Existing and Potential Problems IThe development of this project is not expected to have an adverse impact to the downstream Drainage for the 25 lot subdivision will meet King County requirements for detention and water quality. Portions of the Class 4 wetland will be filled as a result of this project. Mitigation measures will be employed to ensure that the III remaining wetland will continue to operate hydraulically in the same manor as before the subdivision. A sensitive area tract for the wetland and buffers is provided. There should be no impact to the downstream system as a direct result of this project. IIICore Requirement No. 3 — Flow Control 111 The proposed project is located in a Level 2 Flow Control Area. The Level 2 Flow Control requires the developed flow rates discharge to the predeveloped flow rates ranging from 50% of the 2-year peak flow up to the full 50 ear e See Appendix C for preliminary detention calculations. Y peak flow. IThe project currently contains two separate discharge locations, however, the two discharge points converge within 1/4- mile of the site, so the project is assumed to be contained within a single basin. The project proposes the re-aligning of an existing intersection, on the east side of 116th Avenue SE, near the northeast corner of the site. This improvement is being completed in order to align the intersection with the project's proposed intersection. The east side of 116th Avenue U SE lies in a separate basin than the project, and the proposed improvements there will add less than 5,000 square feet of new imprervious surface, so no flow control is proposed there. UCore Requirement No. 4 — Conveyance System As part of the final engineering design for this project, it will be required to demonstrate that the storm drainage system Ican convey the peak flow from 25-year storm event, and that the 100-year storm event does not create or aggravate a "severe flooding problem'. Core Requirement No. 5 — Erosion and Sediment Control In order to protect the downstream conditions from sediments several ill (BMP's)from the King County Surface Water Design Manual will be utilized. Duron riing and ntrol eafter grading, and dust Management ring house IIIconstruction, the site will be stabilized with appropriate BMP's consisting of silt fencing, mulching and hydroseeding. A temporary construction entrance will be installed for construction related traffic. Filter fabric will be placed over catch basin grates. All yard areas will be landscaped. Additionally, limiting earthwork and utility construction activities to dry weather conditions, minimizing area and duration of soil exposure, construction of temporary storage basins and protective dikes to control storm runoff, and sheathing of strippings, iii further vii, stockpiling and construction will include theco construction of sediment)al ba�ns,r it-laden runoff.the installation of silt measures the employed of during to be cleared and graded, and mulching and hydroseeding of exposed soils after lattainmennces t ogfinal low side the areas grade. Stockpiles I will be covered with polyethylene sheathing. Additional erosion control measures by individual builders are recommended during construction of houses. These should include installation of a silt fence at the roadside, placing a bed of builder's sand between the house and the street, and covering stockpiles. I 1111 WELMAN SUBDIVISION Level One Downstream Analysis I IIICore Requirement No. 6 — Maintenance and Operations p ons See Appendix D for the Maintenance and Operations Manual for the Welman Subdivision. __........ _...._........... Core Requirement No. 7 — Financial Guarantees and Liability IIIThe Financial Guarantees and Liabilities will be required prior to the project being finalized by King County. Core Requirement No. 8 — Water Quality IIThe project will provide basic water quality prior to discharge to the class 4 wetland on thej roec be accomplished in a wet vault under the project detention vault. See A P t site. Water quality will calculations. ppendix C for preliminary water quality IISpecial Requirement No. 1 — Other AdoptedArea- Specific Area Specific Requirements aThe project is located within the Duwamish-Green River Watershed, Water Resource Inventory Area (WRIA) 9. Special Requirement No. 2 — Floodplain/Floodway Delineation HThis requirement does not apply. Special Requirement No. 3 — Flood Protection Facilities IThis requirement does not apply. Special Requirement No. 4 — Source Controls Source Controls (J1, 1 This requirement does not apply because the project is located in the basic water quality treatment area. Special Requirement No. 5 — Oii Control IThis requirement does not apply. u II II II II I I WELMAN SUBDIVISION 1 Level One Downstream Analysis II II I I I II Il APPENDIX A - FIGURES uVicinity Map 1 Existing Site Survey I32 Proposed Site Plan 3 Soils Map 4 II Flood Insurance Rate Map 5 Flow Control Applications Map 6 III Water Quality Applications Map 7 7 Landslide Hazard Drainage Areas Map II8 Ill II 10 II II II WELMAN SUBDIVISION ILevel One Downstream Analysis InfrillINININE, 1111pri �;; , _- ;env® 1�-� � rp Attiou , 1 'IEEE ioviik - lab.la. '441 I AM 11:3/i ALM MIN MI I \ 1 minplyili r alltimuw/Apri- . i gl -111111ffilklit*ItcAll 1 arl, IN 1 ''''44P4/44,04,...., merrIcs0/ ' i,„, e: ,,,,, opuNL_„ gal iisolo I -4 ''Ail ® : � '4 "`�"�ai X11 it Allipallprp'� X11 inn j h1/4--4 - . I A N"'-' % iji-----..._ . ..6..,,- IT-Ieliiik ..._, c@)--i----„, .. '- i_ .__ . , .4,, II\ a, .....,........ -4, . , 1 lair, tAtifttnar, „ ._11' . x , . e _, , Nortit.,_. ..., . .., NI kp wa- ft 1 i . Ad��� wit � at/ 41 r —its- 'ROJECT ® Ati 1 I ' Ill ; /if' ir fir � I ri / , E IOW. OW it MI , ili IsU 1 pm 4 4mi a lin 10! ��E •T� z I 1 ra „,,,iv.'J .� ,«ITA,�RS 5,��T 1 , F ,........, „1,,,w; .,,.., „ *�..-..-. W 1 ,FicD x, iNIII/E ler .4eals I III i 1114Milittat*-200*11 ED EL,. al SAM iiir .iiL.i 1 Nri9n _.7 r; WELMAN PROPERTY N.T.S. 3/6/2008 Site Development Associates,LIC Scale Date 18322 Bother way NE:lathed.We Nn tan Keit I 136-ooh-oa : ;b,.,xi, ygc,25,,8; 3 . , �n c°rn VICINTY MAP I'rojdct No, 1 Figure No. I 1 N _ _--- :: -- --- - - v`_ - 11\ / p/j ----"' ___ _ _ ____. -.....s. 1 — l 1 L__ e9 /, , ti 09/ / I �/ ' / -_____/%A / i 1 1 % _ ( i •.l l• X , \ oo A- P ( _____ _ - / x / I o - __ , V / �� , X ( I I( , r r-41..., —"...._________,&7 /- ---7 1 I ( si 1 / 1 • l() ": \ 1 )I 1-41-- 4 . N - I I 1 -- / 7 ____\--: ______:j____ ,.-,,,,4E--_____ ... \,...c . ! [ I \ "si* ( - L-\ - K 1 _ - ' \ , -- 'I i N x __ I n I EXISTING SITE CONDITIONS TOTAL BASIN AREA = 2.96 AC. (ASSUME 100% FORESTED) I I SAM I NKJga Drawn WELMAN PROPERTY 3/5/2006 Site Development Associates,LLC Sca e Date 1E322 BothN�e8 Way Botha,wasyngton 98011 Scale I 136 -05 omae:47s.486.6533 roc 425.486.6593 wwwsdaeglneeisrnm EXISTING HYDROLOGY Pr06;2 5No. 2 Figure No. N f T--- ---------•________ _ P. I Ell --IN `_`_------- - MO- — . r / / , i ` � I .• 1 1 1 / z --- Acir- ...timiimmi_,__w=r._.....,z===m„,„, , , , --- --timiumor- 11\ / fb /r > 1 lk I TRACT / JIJ Olt DTE ON/OPEN SPACE! / I '' "-" x_49 .0 iFGs498.0 F8=4913.• FG=498.0 co .1.. .'------.4 -44, 'ilill ' ---,..._, ' ' �.. / �-- ,- to 1177 0 ,� .�--- 4. ts) CO ,! / I G=499.0 r-- I I -® O Oti, I - --/ / i - FG=502.0 FG=502.0 G=502.0 FG=500W�... mFGO. Q � - r I ( � ► Ii r FG=500.0 TRACT ETRVV —.-- --1,�,�„ cc77pp---A T C PRNAATECACCC _g J.U.D.T. (I r YPEN PACE `-�` �� ;"ciz 1 1k M il 11 ii : 111 FG=502.0 I 23 - 1 ( ) 4 j FC=501 `W�it �� 12 ,n t1 �� FG=502.0 E \ 2 i I JTRACT F ,+J J.U.D.T. CESS ]RAC7�H J.U.D.T. t�502 l.� ��, ` 1� t `\ (1 22 l 4\0• 1 20 / 19 18 17 16 15 14 13 I L,_1 • ;-j -502.0` FG= 02.0 FG-502.q' FG=502p FG=50.0 FG=502.0 FG=502.0 FG=502.0 FG=502.0 FG=502.0 \ / lK !) # soo i- Ia�� 502 I I DEVELOPED SITE CONDITIONS TOTAL BASIN AREA = 2.96 AC. IMPERVIOUS LOT AREA = 1 .43 AC. TOTAL LOT AREA = 1.90 AC. PVMT/WALK AREA = 0.58 AC. I PERVIOUS LOT AREA = 0.47 AC. TOTAL IMPERVIOUS AREA = 2.01 AC. IMPERVIOUS LOT AREA = 1.43 AC. TOTAL PERVIOUS AREA = 0.95 AC. I (ASSUME 75% IMPERVIOUS PER ZONING CODE) I SAM Design "'n WELMAN PROPERTY Drawn Scale I3/5/2006 Site Development Associates,LLC Scale Date 18322 Bothell Way NE;Bethel.wasNngfon 98011 136-005-05 orece:425.486.6533 Fac 425:186.6593 wwwsdaengfreas,oam PROPOSED HYDROLOGY 3 Project No. Flours No. MIK III1Mt = ME NIEL IN. Mit 1111111 III. 11.. 1,111 = = = = =I Milli Soil Map—King County Area,Washington (Welman Subdivision) 561220 561240 561260 561 80 561300 561320 561340 581360 i o '13 ,. ,• -.*.•:".`----7.:77: . 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'-'' •,-;.-,: ...-;-...;,..1s.;.`.ti..,... . .,-:tr4ifrr.„*:.:4<m.,... . 1 :; CV ,1) ........'- ' •'. •..• ;•P '. .... ..11:!?4,..v..A'...i....Y.',. . ....;`-{ ,r-r.ir ' - 1..1..`....': ' -.:,..7 1 • . , . .''---....yri.4i•-,rii-i,. * '`:•-•4'''.l'"----v,?....e:3.4•ilti.;,;:-..$.t.-,..-. ' ''...:'-ar.-, Yr-4.•`,..?.T1,--4,T•fl.-,:••,-..•-‘-k*".1t, _ ' -,,F,I.c•ft,,,,,N,,,,i431.•,V,„..71.;:,:ir4.:',..,:,!•‘"4,i.r,e'. _.? ci -...,-,.. .5.-,:,-,.,.,,,--:"...r.i. -,•• • -] ul :::" _ . - t .... 11 si. 1...:4.r.+1 561220 561240 561260 561280 561300 561320 561340 581360 N inuming== 3,..emonimmi== =iMeters A 0 10 20 40 60 rimenommiles ..... ..m....... Feet 100 200 300 Natural Resources Web Soil Survey 2.0 6/13/2007 gal Conservation Service National Cooperative Soil Survey Page '', of 3 Soil Map—King County Area,Washington (Welman Subdivision) MAP LEGEND MAP INFORMATION Area of Interest(AOI) Very Stony Spot Original soil survey map sheets were prepared at publication scale. Area Aof Interest(AOI) Soils V Wet Spot Viewing scale and printing scale,however,may vary from the original.Please rely on the bar scale on each map sheet for proper .I Soil Map Units Other map measurements. Special Line Features Special Point Features r�� Source of Map: Natural Resources Conservation Service c Blowoutcul Gully Web Soil Survey URL: http://websoilsurvey.nres.usda.gov Borrow Pit °{ Short Steep Slope Coordinate System: UTM Zone 10N X Clay Spot Other This product is generated from the USDA-NRCS certified data as of the version date(s)listed below. Political Features • i t Closed Depression Soil Survey Y A rea: King County Area,Washington X Gravel Pit Cities Survey Area Data: Version 4,Nov 21,2006 Gravelly Spot ® Urban Areas Date(s)aerial images were photographed: 7/10/1990;7/18/1990 n W The orthophoto or other base map on which the soil lines were igt Water Features A compiled and digitized probably differs from the background Lava Flow Oceans j imagery displayed on these maps.As a result,some minor shifting a14 Marsh Y.. Streams and Canals of map unit boundaries may be evident. •5 Mine or Quarry Transportation i I OO Miscellaneous Water i Rails Roads O Perennial Water • r",... Interstate Highways y Rock Outcrop w.^4..' US Routes , -I- Saline Spot • eli State Highways Sandy Spot Local Roads Severely Eroded Spot Other Roads .43:44- t> Sinkhole 3) Slide or Slip jzf Sodic Spot = Spoil Area • ( Stony Spot 11812 Natural Resources Web Soil Survey 2.0 loot National Cooperative Soil Survey 6/13/2007 Conservation Service Page 2 of 3 I ''41.1"-'11-u,.1,14011VV•M.741.*,. ..1. ..3,1-,. : ''.4 - ' -. • ••• ' . v.----.1.4.a.ky:',..‘4.-..r..?c•u_•;,, •;44.1.-7..",..,.7-,T....tit .. .:iiiiii:Al.4.mirtrai......,:,..,:...... ....r.. , .. ,,. ... ..... 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' Pz .fAvi rra � t-rrrl''{,y1:+n.'i,it^cWi.•r �w,ry County � 7,E R c E C°L."Y �'. a •[?g• CA 4'F� ..d ��3a'."Y�i-4 � T•r•z$y"1• �a .'3E.( /(r{r./.Count y s4 €� F`.•••'r.' ) an .t"y' t-iax'r .:zY. .x t_,._�'-'-77'l#r�•fi ✓ 'r c 4.r. r "S za X eb c <.c Zi t .. 11... i"s�,., fi bi v Yhy� 7 �3F*t bra•, , • t z x., ..!> a Ji,r tom,......: 7. f�C SI1t P Ha�arrl k s • .-, #��7--- ra n a a Areas Mapz�E , `? , 1,• �: €; ,_�..r �,t z* . , e `,R ct--: . /may( f aro a a rte•4... .+mZ' az -s{ k' �9.�cr 4`.�: 4.n • t$+{�3'`�.F„ogr'yrj� ''re I r,iy`'"�'S".y d3YFK 's Basin Boundary(thicker line.designates ; areas with Published$asin Plans) • landslide Hazard Arae y .-4-4,,,,,p14,-,4-' s . Urban Growth Areo Boundaryr' Landslide Hazard Drainage MIncorporated Area '"+w�a�«.�4i o�..�".«^...re y•wi.`+•PM s. -w.�+.r.3......a-t..ee.t.:4I i. ,fit,,.,.wV, Unincorporated Area _ e».,.x...x4444._I-,re W .'+�aTilr? *0O..I ad..,. E,........,wa-.Jpp&n.d'..'6. Forest Zone Area y"n,.14."....4,"'�'"'^c +map..+,..,,.*k, King County Department of Natural ReSOUrces and Parks Water and Card Resources Division =+r+„r..:a.:+`��,- 0 2 A MPn ..`,,,�r..•,•-....'_,.,:':. .'�,�...w.r-nom An.-....oc,;so n....e er,S!s nap is atn:4rb4.oo,he .•- ..........,.,..,._� S+a.nw,>t,fr Mop Sr.K C ..__.._...L....____1. • msQ.tt[4•'..'STV,,,,PM•k4i.,MP mau,.h.., e'f--^��•r Y.Aa • • • APPENDIX B - DOWNSTREAM ANALYSIS Downstream Analysis Basin Map 1 Downstream System Table 2 Downstream Analysis Key Map 3 Downstream Analysis Photographs 4 Drainage Complaints 8 WELMAN SUBDIVISION Level One Downstream Analysis , • p .1 ! 1 • • • :�a:, J ! r, 'JOS: �,1—« ; • R E N T O•N 1 'ti • r.r'• 465' • • t ,ff r. • tr• J ` -rh,� .. t Rentotl `.,....,•145-...:;_k t x;^ta. •, ff .„Del, o Lome.: ,/f`+. y .. t Lower• maple ter '.. •^t ... i i-.s}_. w..:.. t• t• '' 'i ".#y ,oy. nes ,� Gr en j ' Car '}. 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Ah • creeA -FGJ i {?1/1r1 1x61 L— • OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE • Surface Water Design Manual, Core Requirement#2 Basin: Black River Subbasin Name: Subbasin Number: Symbol Drainage Drainage Component Slope Distance Component Type, Existing Potential Observations of field inspector p yp Description from site Problems Name,and Size Problems resource reviewer,or resident Type: sheet flow,Swale, discharge see map stream,channel,pipe, drainage basin,vegetation,cover constrictions,under capacity,ponding, pond;size:diameter, �0 1/4 mi=1,320 ft overtopping,flooding,habitat or organism tributary area,likelyhood of problem, depth,type of sensitive area,volume surface area destruction,scouring,bank sloughing, overflow pathways,potential impacts. sedimentation,incision,other erosion 1 sheet flow Wetland Area/Swale No apparent No potential impacts assuming proper Varies 0'-80' None problems operation of proposed detention facility. 2 pipe flow Pipe Flow through Emerald Glen Subdivision Varies 80'-625' No apparent None problems None 3 Detention Facility Emerald Glen Detention Facility N/A 625'-700' No apparent None None problems 4 Overland Flowsee comment at This reach was on private property and Flow between Emerald Glen No apparent &112th Ave.SE Varies 700'-1100' problems right) could not be inspected. No well- Subdivisiondefined flowpath was observed. 5 pipe flow Flow beneath 112th Ave Se Varies 1100'-1400' No apparent None None problems 6 Detention Facility Detention Facility at intersection of No apparent 112th Ave.SE&Se 184th PI. N/A 1400'—> None j problems None _ . _----..._.. _ .....-----_ _ � ���� ���� DOWNSTREAM ANALYSIS KEY MAP -=-._ ---- ----- --._ __. _ _ . _._ _ _.. _....- ----------.. . ..._._ iMAP -- -.. . _.__... _ . __ --- - --___ --- -- ---__ __ _ __ . . - Legend • � [�ountyt ec,undary. . � . !��► �on���it� r; ;�'; Pubscl..and sw,rsy F`� � � ••• Sac�ong � � b'��.��� � _ S�a�rs - . � � �� � � � �' Nf l�al t�1� � �t1{�`1i0AA�4tt�3 � � l..skes ansi Largs � � i�ivsrs �3.�!�`� � .,,Y� � �� _ �� r.Yf Stre�ms � � ��� . � _ � ,����.��� �I � pRoTEc r s�rE � ��T�iyT�as� ��D S�t�C.LGS—� ' , . � —� �Pc FcaeJ � �i4F�R�+� J�Ta�� . .�. - i-�---� �1lERt.�.v0 �eJ � l���X ���J , `/ ' ��� �CATIoti • ti` ! �f�$GTlo� � �� � f��z.�,.vA�s �„�.�u.�vr � � . - � n�t mT¢�•- S.rE S�.�rc�t / "_ 2�� ' �.anprrox, � � � �`T - , ._ - � � �� ..��� �. ` ,�,,� 1 - - �fls# e information included on this map has been compiled by King County statf from a variety of sources and is subject to change without notice.King County makes no representations or warrandes,express or implied,as to accuracy,completeness,timeliness;or ri8h�s to the use of such infortnation.King County shall not be liable for. general,special,indirect,incidental,or consequential damages including,but not limited to,iost revenues or lost profits resutting from the use or misuse of the information contained on this map.Any sale of this map o�infortnation on this map is prohibited exc�t by written pertnission of FGng County. Date:7-13-2006 Source:King Counry iMAP-Prope Information (httpJ/www.metrokc.gov/GIS/iMAP) • DOWNSTREAM PHOTOGRAPHS -•g:ze... , fr:-. _ t:,•-4--- ..,,,,, , •t 4„,.., ,,,-,,- , - ----:--:(..:,...,.. , :..,,,,• .;-*- 4 1....„ .,,,,it,•,4 .1: litcgr'1,.' - . '..:.: :.?"5. .:.•:- • -..,. .•-• .•?..7,t, '1, tip .;:,---gi '24".•'-'- i-!:?•:-:j.:',.; • 1 ,11 tz: .....,,.',,i:4• ,, --.- ;',• • • • u • -•7, ..,. • .. - ..-•‘.. . . . . . . - . . . .., • ... ..... ,. . . . • . .. - • • • • . •• . • ..: I. I'. • ••' . . - • . • . ' • i• I • '• ' • . . . r ' . . ' ....• •' ...... .1 .‘ ,. . " .-• . . . .-.., !.••• . .. . . • . . ..,...". ..... ' . ' . • ..- .• r -• ' . • . . .. . .-'-... • . :N., : • . .' . ' . ... • -.. .r ,.. ..., . • , . . ! • PHOTO #1 • (Looking East along West Property Line) ' te;11111.:11-K;,vF-ntNk:,--• _ _ :..- '''''''-‘ - , ,..:4.. ,..-,..7::;:u4Ostc'''''..,-, ' --• •• "'-',.: , ,.::. ......,,-1;•,.;.;,,T,,,now.:-FT,:.;A • . , • '. 2..-.1:::::4.1.1-574,,,.,-;v:•.... -- _ . . - ._.._:. .--.7.-:--:::24:::----,i •,... . . . -•:.- . . • ... - -• -- • — • . _ -- • , • -. ' - ... - - . • • .... ... -. • • . • . ,... . . .. • - _ .. . .... •._- _..._ , .- - . • . . , . . ..,, .. •.,. ..-. .. . . • _ • - - • - • ; ._ ._••••••mommoot # • • Itiwairfaim '.••_-'--• 1 -.. ..4%. . . ... * ....' • . - -.E - '' *. .-._i; . --''-•.',...1. 1 ',....k4:10:.:.. ' -.. . . • .---...,.' .•-,'.;•.,...: 1..,....,... •• ,. . . .. . . . ..,. ,..1•:. .......,4 . .)-...:,v,•,...,. . . . - .. • _ 1 •h, ... - .--- ,r__--,,. .:,-,..._.--,..__, L,:-: ;.. •:,,,f,:i,!.-- : ?..-•.: . . . • - .• ... „.••.„. ., ,.....,ii-7....i-va •--.a• -.. . . . . ._,_._,..,•:. ,...._L,- -- ._.,.-..,,;.„-=-.., f:::$:.-....-.....,-'•..,-_-:-.,_ ... ----- • ,..: _.. . .. .. __ . . . . . - "., --•.•.. _. _ • . - .• , -- \-• , .... -- , , _ _., • •..:...,._.F.-,..110A.1.••-•.,:._:_;7;,---. .... . ., ' ...., PHOTO #2 (Looking South along West Property Line) WELMAN SUBDIVISION Level One Downstream Analysis -I • I ... ' •": 414 -.._ • • •• , . .-,.1,'• Jt----f51-1,-.,:.,:-.-.- . , .--- — 1 • .. _ E . .. • . . ..,... .. . • ,_... I I • - •• . .... , . _ -. - -- - • . _. . . ,. . ..- • . .1. F _ - Cl•:-!."--_-. OW . /Id .. . - - - .‘ ......-. -... . .. ., . " - •2- .- ,__-. . ., --- ' - • _. ..-.- . . • -.. 1 I) PHOTO #3 (Looking West from 114th Ave SE)) __ .., ... kt.• • '. . - - - _ - _ - - ` - - - . - ,._.„.,,r1."'........-5• -- . ., , . -' .- _ - - 1 .!!:::•:•:''.'-':•'._;:. ' ; .'-__,,'--.-,,,..,-,,,,-."- - -....,..1..:..,,-•t-'1-:=.7, ''7.,----"..-...-.. . ...:_t..--•'-'''"."'"-`-'. - 14.....-"i ..:";1?: .-?"?'-'"•''''.. .'. -;• -• J.-VZ-tr----='..-- ' ' ' ' •' -- • ' - ' Y''-.-".:j.:' '-45'•:;i?-st-,•fw•4i-'' .••.. --, •:--: .- .,' ,-...--'-:.•... ;_L. -- , ,._--...•--_ •,' ..-7._, ,-,1•:?•Zi`f,4f:' q'-!'. .. --1-,-'`,:,, -• '-; -. .-;.,,-; , -.,.; , ,, ;; - .......,..4.., ., ,.,• 51:',•'..4:-"I'!“,,-':'','• --7 v• ,..,'`'a•.'.--r-r- A-M,.' Y .. . •.: -, :'''-: ' •-••til,--• .. " - .. ... - *,.1..„..-2.,-,•....t..... J:4's.-«,--..-:-.- '- --- -,, ,-,---1,,,,ifa -t,4 ,:. -.4: . :go, !..„,.,,,-.,_ ,•4,rjr.,-K:it•ao,,,r,.. . i,,__, .,:.-•-...--, - • ,4..•-,.•••••••-...,..s.s -,-•••;-*:',',',f- •. .1 ' Wiri.t.-6,-;lif022--,.„'..q.'..."7-•:''. ''''',i''''''!": '•. Q:47,-,4_,-,44,-, „.-„,..,,.... , , . .v...,„,,,_.,, . . _ ..,,,....„: „„..„,,,,., „: ,- •„_:4 ,,,,., .„...... ,.,, ,..„.„......,,,,..„; -.,,......_„_. , :. • ,..,_, ,,,,, PHOTO #4 (Looking southwest at detention pond) WELMAN SUBDIVISION Level One Downstream Analysis • 1 •:... •. • •-• ,= - 4,100004P' 4.00650.00gegootwommsoltx**, ,04 PHOTO #5 (Looking North along 112th Ave SE) 4 ts 45- le. •PZ $4 • . . ..+e,rtemriiilkwisOrts,„4‘,..,..,. • ??.• . ' '" ••• • 'yr "<: •-•E r • - e 'a:217'7.7`. Nad y • • ‘N. \ \ -•!-;; r LeL . - - , - - 3.:5117%%1-74.:•$.11;t4Tizlita:";igIt'r:.4.-.4tg- 214.44MTVF,'-'74 PHOTO #6 (Looking West at detention pond) WELMAN SUBDIVISION Level One Downstream Analysis • • h • -?Pati* y • PHOTO #7 (Looking East along SE 184th Pl.) • WELMAN SUBDIVISION Level One Downstream Analysis 1 • • • • • • Drainage Complaint Number 2002-0314 • This drainage complaint applies to the property at 18524 114th Ave. SE. The complaint appears to be a Type 1 (nuissance) complaint. The property owner claims that an adjacent property is discharging flow to the complaintant property. King County listed the complaint as a private drainage dispute, and issued standard handouts to the property owner. No further action appears to have been taken by the County. The subject property and tributary properties are in the general vicinity of the downstream analysis, however, neither property appear to be directly in the downstream flowpath. Flow from the Welman subdivision is collected and conveyed around the complaintant property, and it does not appear that the Welman development will have any affect on this drainage complaint. WELMAN SUBDIVISION Level One Downstream Analysis KIN COUNTY WATER,AND LAND REsouRCES DIVISION ----74Le' DRAINAGE INVESTIGATION REPORT t INVESTIGATION REQUEST ice. S I-rt. , Type _C4_ PROBLEM: r / I . .-vc.v.1--- i` ECEIVED B:Y. C i 1 # Date:__,_ JO_a0K'd by:_ FILE No. 2002 -nn °J/4/ V. Received from: (Day) (4 215 (Eve) ( ) NAME: flJj ' ,k1 \ PHONE lz,1121 `J`1Y7 pt ADDRESS: it�}A`� //Q711 a4?-( OCity State Zip LOCATION OF PROBLEM, IF DIFFERENT: low% ,. 16 i�Access Permission Granted\FSCallFirst (Would Like•To:B;e.Present) 0 fi kft) ‘,1A1Wei --wm 2,,,,t ,, ! !' `o O y,�kt cmf2, 001,r, a ,Aeucc a. Nopplit2 . yA1,0 .0 . ' - ikt.'' . oamtuffeto pace, codeL too-, wi4eafk .i Plat,name:6/tYleagge, (7 iti,vi Lot No: Block No: Other agencies involve& No field investigation required TO_I3E.COQ'I,PLETED.B;�, OMPLAINT;PROGRAM STAI+'F SE-. -.34Z - — A S T R Parcel No., a_975-0-?5C) ((D Kroll Th.Bros: New RDP Basin 8 LK. Council District C : Charge No. RESPONSE: Citizen notified on. 5 '?-� � by: phone. letter in person --.?(. IQ An-I--- Vit43-6 t U) ?ti 'l-.el-0 tii0 °F-a1t/\ J'U(9 ft-6o ithVG t-OTS I P (z_. 6 IS 0 —re-P . , 4i.-10 t-- -7,lAr • 14 Dfao=rs C t.PL)-,1Q4c+'-'7=, C t--05 DISPOSITION: Turned to on / / by OR: No further action recommended becaus::: Lead agency has been notified: Problem has been corrected. — No problem has been identified. Prior-investigation addresses problem: SEE FILE if _ . rPrivate proble. -NDAP will not consider because:. /Water originates onsite and/or on n ighboring parcel. —_Other(Specify): DATE CLOSED: /3 /0 --By: . ........_ 1 _ , • ,..__,....-4,.,:, :."-,"'.--'1, , .. • — 't-0.-4,•-,4i-'•. . : . Complaint 2002-0114 Irwin . ..., . • Investigated by Andrew McDonald on April 25,2002 -,.--, - . Visited site and met with Deborah Irwin and discussed her property's rear yard drainage problem. . • Ms. Irwin experiences a wet rear yard during therainy season and complains that water is flowing from properties to the east onto her property. In particular, she says, water is draining from a paved area serving Lot 11 to the east Ms. Irwin assumed the driveway,.which accesses Lot 11,was a County right-of-way and therefore we were responsible for water coming from the east. I explained to her that it was a private driveway that serves Lot 11 and therefore was a private drainage problem between two property owners. I told her.I would look at the design of the drainage'system forher development and if there were:any lines in or near her rear yard I would be back out to investigate. There are no drainage lines in or near her rear yard per the as- built for the development of Emerald Glen. At the tithe of my site visit there was no water:in'the rear yard. However,there was saturation,of the rear yard. Grass growth.was moderate in its density and half of it was yellow. Pr the complainant, water"gushes" out of an area of plantings along her rear property line. I could findno direct source outletting water. From the way the property behilid her is graded it is possible that water is sheetflowing across their lots and onto s. her-s. , .. . .... • . ., . .saturated 1 ' . . ' ,4 ound. • • .• (11110.--4kik . • .- , . \ • i 8324 .• .. -4 -• . micare -•-________ woo. co• . \ co* \ Fenc.-9.,Srizicirr. /4 e, , ArZ11111:11 ' • \\ 4N, . . N. . . ..,;--- - •1 • • Drainage Complaint 18504 112th Ave SE No formal drainage complaints are on file at King County for this property. However, during King County's field review for the Welman Subdivision, County staff were apparently approached by the property owner regarding a drainage problem on the property. King County has requested that the property owner be contacted and interviewed regarding their drainage complaint. Site Development Associates contacted Judy Bryant, the property owner, in June of 2007. She indicated that her property was experiencing periodic Type 1 (nuissance)flooding problems. Based on the local hydrologic features, and topographical information available in the area, it is likely that the flooding problem originates east of her property, possibly near the discharge of an upstream detention facility. Ms. Bryant indicated that she had previously lived in the house immediately south of her current residence, and recalls that there is a 10' drainage easement across the back of the lots adjacent to her. This was verified on King CountyAssesor mapping. This easement most-likely contains a conveyance pipe, which is intended to carry flow from west from the upstream detention facility. A pipe could not be located during the field-investigation, and it's possible that it is buried, and not functioning correctly. From my conversation with Ms. Bryant, it appears that flooding has been limited to her yard, and that flooding events are periodic. It was unclear whether a flooding event had taken place within the past year. The property in question lies directly in the downstream flowpath of the proposed Welman development. However, the property is required to meet King County Level-Two flow control standards. This standard is intended to ensure that peak flows and peak flow durations are not exceeded for all flows ranging up to the 50-yr design storm event. With this in mind, the drainage is not likely to be further aggrevated by the proposed development. Location and maintenance of the existing detention pipe in the adjacent lots would be the logical first step in alleviating the problem. WELMAN SUBDIVISION Level One Downstream Analysis i r r, PKing in County Drama•e Com'faint 1.10. .r -t ,.t A- t.e' .7.r 146 " ,{ 'r. s - -71 S_.r' b2,, +. ry ,c•i r •'i. ?e 4-.1i �1:i ier,.. ".....0-:,,r1 [1 4 r „. "CMZ• ` u 'C 4 '' / // ac 'r,7", =xN + '4• 5+z �,,, ^X'i�i`t 't.' s h� ,S3 r -._,,..„7„..,44.,,,i,,,,,;.„,,,,,, i ! F!/ t Q' r ('t r1, f ��•: d r ,> l e g 4. 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'f---7147;-.:,,,,t F. ,, ,t,'r' -s, t •e r&kt....71,i .,A,,15 • _ ,-0. ":61 r, "p 6{" l-, ok i.:l.•."t? "'-�'.:,, iii 1t rk �'+' �: A• -- .. ^a;rl ,Y .d10 ."'' � V^,, . 1•i,rs t gc,+a t* A. It]ys+,eua - _ ..=.`..m.-x:� q r�`a4{En'�� r x+a- The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without` notice.King makes no representations or warranties,express or implied,as to accuracy,completeness,timeliness,or rights to the use of such information.King Cc shall not be liable for any general,special,indirect,incidental,or consequential damages including,but not limited to,lost revenues or lost profits result the use or misuse of the information contained on this map.Any sale of this map or information on this map is prohibited except by written permission c