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Home My WebLink About03163 - Technical Information Report - Drainage � �/ � � !03 STORM DRAINAGE REPORT ��OSE SHORT PLAT � � � 3414 NE 1"7�PI.ACE lYl SECTION4, T. 23N,RSE.W. M. RENTON,WA5HIl�TGTON 98055 RENTON-LUA-03-079 FOR: WENDELL WOODALL 329 NW 2r1D PLACE RENTON,WA 98055 DECEMBER, 2003 JOB NO. 719-015-031 Prepared by TOUMA ENGINEERS& LAND SURVEYORS 6632 S. 191ST PI,Suite E-102 Kent WA. 98032 (�� 1� 10, 11 PH. 425-251-0665 ��A H. Tp m ►�Q. 2�o y Faa 425-251-0625 �O�` dr w� *1� � ! 9 �� sa�o � y '�e►st�¢e �N� <�,� ROSE-SD.DOC �� 'ti.•`=�'�'�"'�� '�'3��3 � TABLE OF CONTENTS Pages I. PROJECT OVERVIEW 1-4 II. CONDITIONS & REQUIREMENTS SUMMARY 5-6 III. OFF-SITE ANALYSIS 7-8 IV. FLOW CONTROL & WATER QUALITY 9-16 V. CONVEYANCE SYSTEM ANALYSIS AND DESIG(� 17-18 VI. SPECIAL REPORTS AND STUDIES 19 VII. BASIN AND OTHER COMMUNITY AREAS 20 VIII OTHER PERMITS 21 IX. EROSION/SEDIMENTATION CONTROL DESIGN 22 X. BOND QUANTITIES WORKSHEET 23 XI. MAINTENANCE & OPERATIONS MANUAL 24 APPENDIX: GEO-TECH REPORT BY 25 GEO GROUP NORTHWEST, INC. ROSE-SD.DOC 1 � 1. PROJECT OVERVIEW This project consists of one parcel of land appro�mately 1.70 acres. The project is situated in the northeast end of the City of Renton. It is located within southeast quarter of Section 4 Township 23 North, Range 5 East W. M. The proposal is to create 3 lots, "Fill in" subdivision. Access to the proposed project will be via from NE 17�' Street situated south of the property. There exists a house on the property, which the owners are planning to retain. The soils on the site are composed of Alderwood (AgC) gravelly sandy loam per the King County Soil Survey. This soils information is substantiated by the geologist report prepared by GEO Group Northwest, Inc. The site is hilly for most of the area with an average slope of 15 percent. There are steep slopes greater than 40 percent noted on the site covering most of the east portion of the site. The flow from the site is oriented from west to east directing sheet flows to the northeast toward May Creek situated within the eastern portion of the site. The proposed development of the property is considered as "infill" project and it is located in a Single Family(SF) zone. The City of Renton designates the site with the SF zoning. The SF zoning allows for a minimum lot size of 4500 square feet and a maximum density of 8 units per acre. The setbacks allowed in the SF zone are as follows: front yard setbacks, 20 feet; rear yard setbacks, 20 feet, and side yards setbacks, 5 feet on all interior lots, and 15 feet on corner lots. The City of Renton Comprehensive Plan designates the site as Single-Family Residence, which is consistent with present zoning. The density for the developed portion calculates at 5.85 dwelling unit per net developed acre. There is no right of way to be deducted from the site. The proposed lots will be served from existing roads or private access easements. Majority of trees will be retained except for few deciduous specimens that fall within the building and driveway enve(ope of the proposed new lots. There will be no land to be dedicated to the City on this project. REVIEW OF RESOURCES 1. Vicinity Map 2. King County Soil Survey Mapping. 3. City of Renton Zoning and Subdivision Ordinances Pg. — 1 ROSE-SD.DOC v i v .�;: ,t� u ;��, 3 / 4 � , 3 5`� �, 1 _ _ � 23 � 21 ^�� . �ot � �� , a ` `' ^ 4 � ia� � ' � ; �`V 24 ^� TR 8 � � • t ` ig � S� , 2� .�� t • N �L� rn no � ,s.es 5 1 i � , \ S 25 ;` �/ '� i l ~ �,�ii{� �o tt : o � B " � i i �� t1� a 6 � .. � � � r iso � � ' ,,��' � 20 g 19 � �8 * � i2o� o ^ 9�� ; � �;r �i � � s � I,J � �^ L+, w `:' 10! _ � _ _ v Zf � � �S S� M N K 63 � /06 09 �t7s� s� !�S! , CEN� "r ts ��:�� N E �21ST ST °� b ,o� s` E' 1O4 H ?' ° GS3 i2l 60 � / o� �o� 71 0'� � iesier ,. �—�' �3 - lt� iurtso�k / / r '� � io 9 �^ g °"i 5 �, �.o ,.�o 0 �a H � N E Y C R E E K m �� :� �.�' " W ��$` z , � " 10�! 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Fv�' �. dy L.�� Vt�" � '?.' ��'= �.� �� '� � � I�� y �i � � �t " j t �!�` ! �� g1, � Plam �� V i � � � � II � � , � �, � �� ,��• �4 •�7 i��`�''� ♦ '��.: � � '�i �4 I� �• ' � ♦ r � :� I �ti I �� ` �I �1 ��r __v. '-1�(\+{ .,% \�A'� RdE 9fjp•pc;. �p i.��.- �� I� 1 ��;i 11'� II '� �. �' .! I� �• . . . � /. _.� .. `P_ ..,. ... . . ' `•�r.;�._ ,1 _-•__. _ �1.. ..�17�1i� � � �r�. . � ��I�"�?(1" 1 L,inc �1�,r•I 1 1) � '�,.,.� �. . � o . .i �.�„ri i 7 an S� �� , � � � �� sc��c. ��P ��,e��r� P� . — �I _ . � Il. CORE AND SPECIAL REQUIREMENTS CORE REQUIREMENTS 1-5 CORE REQUIREMENT#1: DISCHARGE AT NATURAL LOCATION The allowable outflows from the site will be discharged to its natural locations. The level I flow control if required will be calculated to match the developed peak discharge rate to the existing site condition peak discharge for the 2-year and 10-year. CORE REQUIREMENT#2: OFF-SITE ANALYSIS A level one downstream analysis is a portion of this report. See the analysis later in this report below. CORE REQUIREMENT#3: RUN4FF CONTROL The increased peak runoff, due to any change in pervious conditions and increase of impervious areas, will be attenuated using peak rate runoffcontrol in accordance with KCSWDM , 1998 Edition. Initial calculations indicate there will be no detention or detention facility required. Please refer to attached KCRTS calculation. CORE REQUIREMENT #4: CONVEYANCE SYSTEM Conveyance system is minimal for this proposed short plat. Storm runofffrom private road and new homes will be directed into storm drain spreader allowing the water to sheet flow over the steep slopes situated east and northeast of the property. CORE REQUIREMENT #5: EROSION/SEDIIv1ENTATION CONTROL PLAN The erosion control plan will be designed using the King County 1990 storm manual. A sediment trap is anticipated during construction. It will be situated and constructed to minimize any impact to downstream or offsite areas. CORE REQUIREMENT #6—MAINTENANCE AND OPERATION N/A CORE REQUIREMENT#7—FINANCIAL GUARANTEES AND LIABILITY N/A CORE REQUIREMENT#8 —WATER QUALITY The water quality facility proposed for this site will consist of a wet-vault or a similar facility. Pg. - 5 ROSE-SD.DOC � SPECIAL R�QUIREMENTS: THOSE APPLICABLE TO PROJECT 1. Critical Drainage Area- N/A 2. Compliance with existing Master Drainage Plan-N/A 3. Conditions Requiring Master Drainage Plan -N/A 4. Adopted Basin or Community Plans-N/A 5. Special Water Quality Controls—N/A 6. Coalescing Plate Oil/Water Separators - May be required to provide water quality mitigation. 7. Closed Depressions - N/A 8. Use of Lakes, Wetlands, or Depressions for Detention - N/A 9. Delineation of l 00 Year Flood Plain-N/A 10. Flood Protection for Type 1 and 2 Streams -N/A I� 11. Geo-technical Analysis and Report - A copy of the geo-technical report is enclosed with this I report. 12. Soils Analysis and Report - Refer to geo-technical report Pg. - 6 ROSE-SD.DOC � . III. OFF-SITE ANALYSiS A: UPSTREAM This proposed short plat does not have notable off-site surface runoff entering the site. NE 17`� Place(south of the property) intercepts most of the runoff and directs the right of way flow east and southeast. B: DOWNSTREAM ANALYSIS Surface runofffrom the site is directed to the northeast toward Honey Creek. The site outflow will be directed to a flow dispersal trench to prevent point discharge. These trenchs must be limited to a maximum of 0,5 cfs, and will spread and directed runoff through vegetation down the forested hill toward Honey Creek. From the KCRTS calculation in the next chapter the peak 100 year flow is 0.345 cfs, below the limit for a spreader trench. The creek is about 4' to 5' wide with cobbles and gravel bottom. The stream meanders with heavy brush and tree overhangs for about 1800 feet to NE 27th St. to the northwest. At about 300' upstream from NE 27�' St. as shown on Thomas Brothers sheet 626, Honey Creek makes a bend to the northeast to cross under a 12' wide, 15' long bridge with concrete abutments. About 200 feet downstream of the bridge the creek enters a 54" 100' long culvert that appears to have a riprap spillway constructed above the pipe as an overflow if the 54' pipe is full. A 60" diameter culvert 40' long carries Honey creek under NE 27�' St. and continues northwesterly toward May Creek about 1200' downstream. Honey Creek is a tributary of May Creek which lies about 3600' north northwest of the proposed Rose Short Plat project site. May Creek's main stream has been inventoried as a salmonid habitat � for Chinook, coho and sockeye salmon. The City of Renton inventoried May Creek as part of their"Critical Areas Inventory, City of Renton Wetlands and Stream Corridors", June 1991. There does not appear to be overflow or flooding problems within '/4 mile downstream of the proposed site. 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FLOW CONTROL AND WATER QUALITY This proposal will be designed in accordance with the 1998 KCSWDM. We will first check the additional peak runoff for the 100 year between the undeveloped condition and the developed conditions. The area of the plat to be developed is 1.71 acres, including asphalt paving, driveways, houses and landscaping and the Tract"A" open space. The roof runoff from the new houses will be collected in catch basins with roof drain pick-ups and directed to the conveyance system. The site runoff will be directed to an outfall conveyance pipe down the slope to be discharged to an energy dissipating manhole flowing to a filter fabric protected riprap pad to Honey Creek. Pre-Developed Conditions 1.71 acres total Pervious Forest l.04 acres Grass 0.46 acres Impervious Roof and Driveways 0.21 acres 1.71 acres Post-Developed Pervious Forest 1.04 acres Lawn& Landscaping 0.17 acres Impervious Driveways 0.22 acres Lots(use 4000SF or 75% of lot whichever is less Section 3.2.2.1 KCSWDM) I,ot/area SQ. FT. 75% Imp Area Imp Area Used Lot 1 9558 SF. 7168.5 SF 4000 SF Lot 2 9067 SF 6800 SF 4000 SF Lot 3 10149 SF 7612 SF 4000 SF 12000 SF = 0.28 acres 0.22 acres Total Lot Impervious 0.50 acres Pg. - 9 ROSE-SD.DOC The above information will be used in the King County KCRTS computer pro�ram to establish the existing and proposed time series for the peak flows for existing and developed conditions. The 100-year existing condition peak and developed condition peak flows are as follows; Developed 0.347 cfs Undeveloped 0.271 cfs 0.076 cfs is less than 0.l Ocfs difference therefore no detention will be required. The Hearing Examiners Report and Decision Oct. 7, 2003 asks that the outflow be piped down the steep slope to Honey Creek. The site runoffwill be directed to an outfall conveyance pipe down the slope to be discharged to an energy dissipating manhole flowing to a filter fabric protected riprap pad to Honey Creek. Therefore the surface water runoffwill be collected from the driveway and roof areas and directed to catch basins and conveyance pipe. This will ailow the storm water to pipe flow down the steep slope to Honey Creek. WATER QUALITYIBI0.FILTRATION The existing driveway that provides access to the existing houses has a surface area of about 6577 square feet. The older existing house and driveway were built in 1978 per King County property tax information. See the existing and developed sketches on the follo��ving pages of this report. Therefore about 5424 square feet of driveway was installed prior to May 1979, a date to establish existing conditions. The new proposed asphalt driveway area is calculated at about 9585 square feet. The gross new pollution generating impervious surface area subject to automobile traffic will be 9585 square feet. Per the 1998 KCSWDM page 1-50 CORE REQUiREMENT NUMBER 8. Water Quality measures will be required for this project. Because there is insufficient area for a bio swale we will design a wet-vault per section 6.4 of the KCSWDM. The wet-vault permanent pool will be sized per section 6.4.1.1, page 6-68 of the KCSVVDM. The City staff have stated that the existing gravel driveway can not be counted for Pollution Generating Impervious Surface, PGIS. Therefore we will use the area of the new asphalt driveway for new PGIS, with the house roofs connected downstream of the wet-vault V�_ (0.9A; + 0.25A,� + O.I OAtf+O.OI Ao) x (R/12) V� = volume of runoff from mean annual storm A; = area of impervious SF Pg. - 10 ROSE-SD.DnC A,� = area oi�till grass �oil covered with grass SF A,�= area of till forest soil covered with forest SF A� = area of outwash soil covered with grass or forest SF R = rainfall from mean annual storm(figure 6.4.1.A) = 0.4T' Only the area of the 9585 square foot driveway will flow to the water quality facility . V� _ (0.9(9585) + 0.25(0) ) x (0.47/12) _ (8627 + 0) 0.47/12 = (8627)(0.47/12) = 338 CF Vb = 3(338) = 1,014 CF Try 10' wide and 34' long '� DEPTH = 1014/(340) = 2.98' say 3' deep. Pg. — l0A ROSE-SD.DOC 6.4.1 WET�'ONDS—RA51C AND LARGE—METNODS OFANALYSIS FIGURE 6.4.1.A PRECIPITATION FOR MEAN ANNUAL STORM IN INCHES (FEET) ', ST 1.0/ � 1 2 �I ST 1.1 � ST 1 0 � Q.S LA. 0.9 LA 1 .0 , �,.�4 `� � ! � a . �. .,,w . � • �--. __ a . . . _;-: -.- ,S � f I�, • i� ' � �# � _ 77 ;, ��+ M � ` �. I 1 ..� l��.i . �'! .'1.� ' . � f.�t{'� �� `"� ' � �. �� ly._._. a ��.I...I ` . � � L F :�a �• �i � fi � �� ' $ �� ,_.[_,�� h r:� �,� �� + S�� .f"� ] f 4 �' l �( `� .�-a, f�"' ��` t � , "�'�1..�j � «�i?.' . �` . _ '�'aRw=�y. .�'..:i� . t� _-�. `�� \�� .� � �, � � "F�� 1 � x a —' � "" 4 y,`. ,� /+ � r ,i ��. /�i r �( % f� � rd � � y � � I , rt,� . - -� ' e � �� , — . N ��tllia[C �/ i' '�YI/I� l5,.� j 4RTL�"J� �� lI . ��; �� t��'� � ..�, � A�'' � � . `�� ,�� 1 t. �.� .. � / 1\� yd Y � �t \, � . 1 .'✓ �-�Y`/ ` ♦ � `'`f�i� � ��1�� S+�c i � G�^ " , - ..:�}ti �I�r'.f/ � 'r'. � r' � J-.r��- ',��;�- i , . � �� i +' � .-tti;l,�j,l` ' �� !i ( .J� �_\.._.. / a� .. f }� rt ��tix ��. ' € ;r e�l �I,_.�,�:' .yC�..�'�—�.' t., '� .� ,�. _� 1J�Ir' v �_, 4. f � ` , ' .� � ' S P ! � ,� s ,.. �'— —— • . , iI -{� ,. �' $ � � `'' - � ' � / � f '� p ,.�' � ��:? 4 �a,: � .. ,. _, - o � o.�'7 . _ , , . , � d� � � '� � ..'iYr' �FdY` . / .'f:.v'�� '� K�._ . . ... .. ,' . � . � I �� /�- /f /I � � •. f�`T��. � -�.—� � �y �� 4 I � _ `' � � � t / �� 1-�=1 r�-�� .'i E {�i� ✓{ I � � � n i Q �` _ , F4 ; ,� � .. j`�� i i , � ' / i1 _ � --i:..._..�,_--.-.-. �~� z ` r�� 1,f` .� ..yi , u. '� �� n� .'. -�_ �-Pao.c ��,��, � r;.-'1 , d „� ti,f { ' 9Gm� ..h Q � ,-�5� _____ + �.�.�1 . y .'r @� � t'q. : ` L ^� '. � . i p � ';F 4 5. I i��e� `r�/ � �I,` / I � �� ,t,��h r't. 1f � � �� . -�� ,f � j , � � 1 � �f •, /,.,:.. ��, — .� � A,--- f� , �,:: "r �f ��, '- _ � � , 0.5 4" "i'�'� e � _ � ' .f �f' i . J JE} �7r�' ! , �;`1 (0.045' ) F ,. � B ,� ''� ; 6 4 c'lI ro .saz4 - � •t��,;� eon... \� 0.47" (0.039' ) �� " `-- — _ �.�_� - -_� =__�. r__� Incorporated Area >� --., � � ..�c_� Rivedlake 0.4 7" �� , — MajorRoad (0.039' ) 0.52" - -- � � `� 0.65"� NOTE:Areas east of the easiemmost isoplwial shouid use 0.65 �0.043'b.5 6" (0.054' ) inches unless rai�all data is arradable tor the location of interest (0.04 7' ) u The mean arnwal stortn is e micaptual atortn fouM by drviding Ihe annu�preap�ation by Ihs totai number d slortn everrts per year result,generates large amounts of runoff. For this application,till soil types include Buckley and bedrock soils,and alluvial and outwash soils that have a seasonally high water table or are underlain at a shallow depth(less than 5 feet)by glacial dll. U.S. Soil Conservation Service(SCS)hydrologic soil groups that are classified as till soils include a few B,most C,and all D soils. See Chapter 3 for classification of specific SCS soil types. 1998 Surface Water Design Manual 9/1l98 P� - 1 � f3 � The above information will be used in the King County KCRTS computer program to establish the existing and proposed time series for the peak flows for existing and developed conditions. The 100-year e�cisting condition peak and developed condition peak flows are as follows; Developed 0.347 cfs Undeveloped 0.271 cfs 0.076 cfs is less than 0.l Ocfs difference therefore no detention will be required. The Hearing Examiners Report and Decision Oct. 7, 2003 asks that the outflow be piped down the steep slope to Honey Creek. The site runoff will be directed to an outfall conveyance pipe down the slope to be discharged to an energy dissipating manhole flowing to a filter fabric protected riprap pad to Honey Creek. Therefore the surface water runoffwill be collected from the driveway and roof areas and directed to catch basins and conveyance pipe. This will allow the storm water to pipe flow down the steep slope to Honey Creek. WATER QUALITY1B10-FILTRATION The existing driveway that provides access to the e�cisting houses has a surface area of about 6577 square feet. The older existing house and driveway were built in 1978 per King County property tax information. See the e�sting and developed sketches on the following pages of this report. Therefore about 5424 square feet of driveway was installed prior to May 1979, a date to establish ea�cisting conditions. The new proposed driveway area is calculated at about 9585 square feet. The gross new impervious area subject to automobile traffic will be 9585 — 5424 =4161 square feet. The new pollution generating impervious surface subject to automobile traffic, is less than 5000 square feet. Per the 1998 KCSWDM page 1-50 CORE REQUIREMENT NUMBER 8, Exemptions from Water Quality, this project would be exempted from water quality measures. Pg. — 10 ROSE-SD.DOC � \ � , :< � I ^ \ 357.80' N887 4 32"W '3 �� '. �. �, _ N �.�\ ` � _- .__ -, 0 � \ ` �` -- �m�� -- -- - � � '_ _ - -_ � I ' � ` �� , BUIL T 1978 PER �' � . , 1"=50' �� Q ,� COUNTYEXEHOUSE \� � 3 � � ;, �� \ b -- �ss2 s.F) � GRASS � � TRACT A = �=- � ^ �0.46 acxes `� (NGPE) ,'�� ..` . , . �, , , � , '�., . . � � � W ', ^ - �,Q� ', � ' � � � �s �� —I' _ \` 9? \' ` \` ' a `, ° '-- :? ` �' ` ', 45,310. sq.ft. � � -z ' � - _-' 3��'paj ��:� `�',� ., �, ��,\�, 1.04 ccres ^ _ _ � ' `, �,�.'� � � � , v� � � �� .� R�,, °��.� ,o,g,G�',,� t � \ � W � . �y 3 . :� qp , ., ` ` a .��=`3�;__ / ,� � ,�y �,,,�,��; , , �, � ��, — _ � ````,- ��'��!2e'� � 1 Q ` ,�`\ �� M ��•�r��9 ` J \ .1'��O ^ .,=-- _ _ `� �� .� � � ` /`� ,,\ _� „ I J , �. � �� l i � � �U��AFJF'R � `� �� i \ � - �-----_- ` ', � ��\`yOj,_,A/A �79 �� \� �� • -`,--_-'--___- \ • ` � ! � � z '. ' --=��_ � � �� _'__"`__' �t \♦ \ � � ` . _�1 \ � � ` � `� 1 �� , t � , ,� ,d. � �\i • �� , , , I ; �`� .\ -=--- '�. �- ' \` 1� \ ` �~ p 93.65� n�a�as 40 �v 3 t� � I \ 134.39' S88 U9'40'E = �s c'�A va ��'. , � , , tu � �- �. �_� ROOF d� � Q ' � �i �o - . DRIVEWAYS ° � '. ;. � � � -_ � 0.21 acres r ; � � � ° � , $ � � � o �_ , � o� _ � ; ��, � 2 I � � ' � I �� ,��,�� ,�� M� EXISTING ' e �� --`_ s� o ,+�---�--1 ', � c NE 17th PLACE �'T�� ' ! ^ CONDI I IONJ ��_`�_ ��oT ,�s� _ — -_,. —�' , ,1,, � , _ � -�' �� `'' � 71915SKTCH.DWG _ �� . � � � , " � - \ 357.80� N8874'32"W . 3 _ �� . N • � ` ` . 1 � ----_' Q �, ` �` - \- - =�-� N I ------ o �OT 3 �� , �� x � - -- , �, �� \', �� 9,558. sq.ft. 4 � �, �',�, f"=50' 1�, _ , g '° . �, - - _�o � ��, , �: � 3 , , - '��, '� b -- LO'F, 2 �� ,\. T NGPE A �' ' ; �; `,, �� ,067. ��ft � �� , � � ^ .�, , '� , r -, , , � �. �s �� —�� \��- 9?��. `, ? �',��, 45,310. sq.ft c°n _, z `,_ ___== �Ns,.. � / � ' 1.04 ccres . _ �� ;� , �� ,� �, ' LOT 1 , h0 - -. ', '� ��. ^ , 9. s .�ft. ', �, \ � � ` .F�.�,3��, � \�,� . , � , , LAWNS & N � _, _ � �� c� „ 1 �� ', LANDSCAPING '- �� , �� ' o�'; . �, \ � 0.17 acres Q \ ✓ � � / \ Z9�;. \\\ � � � / '. -----__ ', � " f� , �% / %/ ,�� , � �� / � z -- ------_ �, , ,, ,, � ��'�,, , �,,�:� ; ; \; � ----- -----_ '� �, �. , �. ,, , , , ' , �<J �' �, ,, � - _-� - ` �I ' ~ ~' 93.65' ',M83 b5'40"W C � 134.39' S88 U9'40 E ` V� � ,� ��+" � ; � � 1� lU _ � � _ : � o � � �� . _ � , S`•v , DRIVEWAYS ^ �� i�� ' �"� '- � " I � � � 0.22 acres ^ ,- j , `', ► ° - o .�.� ,� ± 2' � i�/ i `� i �� ; .�3� , �,& �i DEI/E� OPED � --� ��z a� /;i \ ,,,_-_ ''� NE 1 7th PLACE _ :��`~�_:,' `�,, ��:�, CONDI l IONS �Mo�� — — — �_ �_�=�— � � � --� ti _.,_�` . — � -,-_ _ _ j �� -- ? �`'� 7!9�5 S 1<�F�. D w G , SECTION III � - - FIGURE III-2. RAINFAIL REGIONS AND SCALE FACTORS ST 1.0/ ST 1.0 LA 0.8 LA 0.9 LA 1.0 LA 1.2 ST1�� _ •MONO4ISH COVHiY — �6� l�N' � O�MFI .` _ MYRt y� KINO--COU�� 1 yh ' � _� 4 � _ � 1 �'� i -.�"� � � �J� (�� r r,�7� ; e - t r-- z _ . � �_ , - �{-�- T � __.,� rt�«�o . ` \r -- �,.. �; �� b 7 - k`•j AE OND �� ' _ � �r� __ I � , �� e ��; .� d � > ,-� --i-.�� ,,: �� . ,„u _- ,r � e r A �,: , i J � ,_ �� drrki��,•a� 81Lf.:� si r t"y.` ELLE E . � � � : , M J, � it,°_�z?. .�V�'� ..v._ E'; u �,�� u� i.� a;2..+1..� _ : '. . .� �_ :. . ��;Y'� ` ,.-.6:./�cV�� .b t�� 'c7�t.: i { � / s F� ' " ..� - . p,�S� . } �' Cl �" f i /F . 4N ` � Z... e�,' � � f �/ 1.,�1 I: .: . Y� . 'E Z'"� �tn i f�. �! f� � ! � � Mioduiura � '� LE� � � �� r. *rsi'F* ' rowr �� J_� � ��t � .��t � r , _,�.��'��4 f � S�rC �� . �� y�c! - E T� , � �'��#z r�e a r�' ' � � � r ✓ �[. 0 � ;s :�e 'a �rart � b , �; �� ` ' ,.. �� ,i � / � �m� .MR s rAp , % �: � - LANDSBURG '` e -o„ � ...� , ,^ ; ,� � o � , ,�.. .. �. �3 ; ,.� ' ff,,/ "'r" 0 �""� � .i `f �.q�;�:�'�� /� � � .�__ , y' ' - � r t' f � � f; ,�li�,� hM - ,d'' , � .. � `u'su"° � � «ae , : � ;��'r�� >�. ,:�",ri f �< ! � � � v+ ��^;fi� - � 't � � %� � � ;i1�-y G7 �� V ':;' •��' ' � � � �/ _ ,, , ,��,- � �. ST1.1 �"` , � /;�. �` � � ,�-, ';- /f';�. 6 �. ` �� iGo'eouN.. .�.�yy ��ea eouwT. �` ST 1.0 ^` n S � Rainfall Regions and �0 8 Regionai Scale Factors � 0,9 LA 1.� � �=-1 Incorporaled Area LA 1.0 �-c� RivedLake Major Road III-4 T,� KCR7'S User's Guide � � � December 15, 1995 � } � RECORD.TXT KCRTS Command CREATE a new Time Series ------------------------ Production of ttunoff Time series Project Location : Sea-Tac Computing Series : PREDEV.tSf Regional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time Series File Loading Time Series File:C:\KC_SWDM\KC_DATA\STTF60R.rnf . Till Forest 1.04 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STTG60R. rnf . Till Grass 0.46 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STE160R. rnf . Impervious 0.21 acres -------------- Total Area : 1.71 acres Peak Discharge: 0.271 CFs at 6:00 on 7an 9 in Year 8 Storing Time Series File:PREDEV.tsf . Time Series Computed KCRTS Command CREATE a new Time Series ------------------------ Production of Runoff Time series Project Location : Sea-Tac Computing series : DEV.tsf rtegional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time series File Loading Time Series File:C:\KC_SWDM\KC_DATA\STTF60R.rnf . Till Forest 1.04 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STTG60R. rnf . Till Grass 0.17 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STE160R. rnf . impervious 0.50 acres -------------- Total Area : 1.71 acres Peak Discharge: 0. 347 CFs at 6:00 on �an 9 in Year 8 Storing Time Series File:DEV.tsf . Time Series Computed KCRTS Command eXit KCRTS Program ------------------ Page � � 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 0.140 4 2/09/O1 15:00 0.271 1 100.00 0. 990 0.083 7 1/05/02 16:00 0. 155 . . 0.155 2 2/27/03 7:00 0.143 3 10.00 0.900 0.061 8 8/26/04 2:00 0.140 4 5.00 0.800 0.084 6 1/05/OS 8:00 0.129 5 3.00 0.66� 0. 143 3 1/18/06 16:00 0.084 6 2.00 0.500 0.129 5 11/24/06 3:00 0.083 7 1.30 0.231 0.271 1 1/09/08 6:00 0.061 8 1.10 0.091 Computed Peaks 0.232 50.00 0.980 Flow Frequency Analysis Time Series File:dev.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. 178 5 2/09/O1 2:00 0.347 1 100.00 0. 990 0. 132 7 1/05/02 16:00 . . . 0.205 2 2/27/03 7:00 0.191 3 10.00 0.900 0. 128 8 8/26/04 2:00 0.186 4 5.00 0.800 0. 153 6 10/28/04 16:00 0.178 5 3.00 0.667 0.191 3 1/18/06 16:00 0.153 6 2.00 0.500 0.186 4 10/26/06 0:00 0.132 7 1.30 0.231 0.347 1 1/09/OS 6:00 0. 12B 8 1.10 0.091 Computed Peaks 0.300 50.00 0.980 C �� r G u 1=o✓Z � . I D GFS � M c ►2r A-s � F'�j2 1 uv-y r� �Gy4►c. s p. 3 �7 - d� 271 = �, p7� C_ �5 �lv ►� r_- Tr�vTlvM � � � c.� � � �� h�cr��s� . rY F,r��Ti O^� S E GT r t�N �, � 2. 3 �w-Q9 �� i �y ��' �G su�vn� �� . - I 5 C DEV-15.TXT KCRTS Command CREATE a new Time Series ------------------------ Production of rtunoff Time series Project Location : Sea-Tac computing Series : DEv-15.tsf ►tegional Scale Factor : 1.00 Data Type : Reduced Creating 15-minute Time Series File Loading Time Series File:C:\KC_SWDM\KC_DATA\STTF15R. rnf . Till Forest 1.04 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STTG15R. rnf . Till Grass 0.17 acres �oading Time Series File:C:\KC_SWDM\KC_DATA\STE115R. rnf Impervious 0.50 acres ; -------------- � Total Area : 1.71 acres I Peak Discharge: 0.754 CFs at 6:30 on ]an 9 in Year 8 I Storing -r;,,,a �Pr;�� r; 1�,� nF�� t � , ;f Time Series Compute ------------------ Flow Frequency Analysis Time series File:dev-15.tsf Project �ocation:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.239 � 6 2/09/O1 12:30 0.754 1 100.00 0.990 0.182 8 1/05/02 15:00 0.528 2 25.00 0.960 .o- -- 0.528 2 12/08/02 17:15 0.330 3 10.00 0.900 0.192 7 8/23/04 14:30 0.278 4 5.00 0.800 0.262 S 10/28/04 16:00 0.262 5 3.00 0.667 0.278 4 10/27/OS 10:45 0.239 6 2.00 0.500 0.330 3 10/25/06 22:45 0.192 7 1.30 0.231 0.754 1 1/09/08 6:30 0.182 8 1.10 0.091 computed Peaks 0.679 50.00 0.980 l � 1`� rlUtnTr� -- D� VrL � 1�� /�F�- �Ls �ar� G�rIV � �/ �9rvcC Gf��G/G p , � 5 y GFS ► t� u -y2 r� F �- �c_ Page I � . V. CONVEYANCE CALCULATION The calculated 25 year and 100 year peak flow from this site using the KCRTS method are 0.53 cfs and 0.75 respectivley. It appears that the piping system will be able to carry the required flows in the 12" pipes. See the following pages for the capacity of a 12" pipe at S=0.5% min slope. Pg. — 17 ROSE-SD.DOC tmp#l.txt Manning Pipe Calculator Given Input Data: Shape . . . . . . . . . . . . . . . . . . . . . . . . circular solving for . . . . . . . . . . . . . . . . . . . . . Flowrate Diameter . . . . . . . . . . . . . . . . . . . . . . . . 12.0000 in Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2500 in slope . . . . . . . . . . . . . . . . . . . . . . . . 0.0050 ft/ft Manning's n . . . . . . . . . . . . . . . . . . . . . 0.0120 Computed Results: Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 2.9358 cfs Area . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7854 ft2 wetted�Area . . . . . . . . . . . . . . . . . . . . . 0.7650 ft2 Wetted Perimeter . . . . . . . . . . . . . . . . 31.6348 in Perimeter . . . . . . . . . . . . . . . . . . . . . . . 37.6991 in Velocity . . . . . . . . . . . . . . . . . . . . . 3.8379 fps Hydraulic Radius . . . . . . . . . . . . . . . . 3.4821 in Percent Full . . . . . . . . . . . . . . . . . . . 93.7500 � Full flow Flowrate . . . . . . . . . . . . . . 2.7292 cfs Full flow velocity . . . . . . . . . . . . . . 3.4750 fps critical �nformation Critical depth . . . . . . . . . . . . . . . . . . 10.0468 in Critical slope . . . . . . . . . . . . . . . . . 0.0069 ft/ft Critical velocity . . . . . . . . . . . . . . . 4.8461 fps Critical area . . . . . . . . . . . . . . . . . . . 0.7299 ft2 Critical perimeter . . . . . . . . . . . . . 26.9432 in Critical hydraulic radius . . . . . . . 3.9012 in Critical top width . . . . . . . . . . . . . . 12.0000 in Specific energy . . . . . . . . . . . . . . . . . 1.2196 ft Minimum energy . . . . . . . . . . . . . . . . . . 1.2559 ft Froude number . . . . . . . . . . . . . . . . . . . 0.8244 Flow condition . . . . . . . . . . . . . . . . . . subcritical Page — / 8 VI. SPECIAL REPORTS AND STUDIES Pg. - 19 ROSE-SD.DOC VII. BASIN AND OTAER COMMUNiTY AREAS Pg. -20 ROSE-SD.DOC VIII. OTHER PERMITS Residential Building Permits Pg. —21 ROSE-SD.DOC IX. EROSION/SEDiMENTATION CONTROL DESIGN The temporary erosion plan will be designed to the requirements of the 1990 King County Surface Water Design Manual. The silt fence and silt trap will be placed to help reduce the chances that any construction related silty runoff will leave the site and affect downstream property or facilities. The amount of cleared area for road and site construction will be similar to the 2-year developed peak, which will produce a peak flow of about 0.24 cfs. From section 5.4.5.1 Erosion and Sediment Control Standards a sediment trap for less than 3 acres development should contain a minimum surface area at 3.5' depth to riprap weir overflow and 4.5' to top of berm will allow settling of the silt particles. The minimum surface area is to be based on the formula; SA=FS (Q2/Vs) where FS = Safety Factor= 2.0 QZ =Peak 2-year developed flow (0.24 CFS) Vs=Particle settling velocity=0.00096 f/s SA= (2) (0.24)/(0.00096) = 500 SF. Required 3:1 side slopes � 351.0 28'x30' Top of berm 350.0 22'x24' S28 SF Overflow 500 sf req'd. �'�� 349.0 16'x18' 288 SF �' 348.0 10'x12' 120 SF �' 347.0 4'Xb' 24 SF ' 346.5 1'x3' bottom of sediment trap I The sediment trap should be constructed on the lower portions of the site. Pg. —22 ROSE-SD.DOC IX. BOND QUANTITIES NONEiNCLUDED Pg. - 23 ROSE-SD.DOC X. MAINTENANCE AND OPERATIONS NONEINCLUDED Pg. -24 ROSE-SD.DOC _ _ __ �,�..,..r..,.,:�_ ..r.._ . .._._. ...._.., _.._,._- - -_-_- - _. APPENDIX : GEO-TECH REPORT BY GEO GROUP NORTHWEST, INC AUGUST 5, 2003 P . -25 'I g ROSE-SD.DOC I ..,. i • � , GEOTECHNICAL ENGINEERING STUDY LOTS 1 8[2-ROSE SHORT PLAT 3414 NE 17TM PLACE RENTON,WASHINGTON G1541 Pre ared for I P Mr. Jeff Rieker 1075 Bellevue Way NE, #1500 Bellevue, Washington 98004 August 5, 2003 Geo Group Northwest, Inc. 13240 NE 20th Street, Suite 12 Bellewe, WA 98005 Phone: (425) 649-8757 emaii: wchang@geogroupnw.com . . f.�s �_ : �. __ __ _ ___ I G r o u p N o r t h w e s t, 1 11 C• Geotechnical Engineers,Geologists � 8 Environmental Scientists i -- August 5, 2003 G-1 �41 Mr. Jeff Rieker 1075 Beilewe Way NE, #I500 Bellevue, Washington 98004 Subject: GEOTECHNICAL ENGINEERING STUDY LO'CS 1 &2-ROSE SHORT PLAT 3414 NE l7TM PLacE RENTON, WASHINGTON Dear Mr. Rieker: We are pleased to submit this report entitled "Geotechnical Engineering Study, Lots 1 & 2 - Rose Short Plat, 3414 NE 17"' Place, Renton, Washington." This report presents our findings and geotechnical recommendations for the proposed single family residential development of Lots 1 and 2. Lots 1 and 2 are relatively flat, however they are located within 50 feet of a steep slope critical area. The steep slope has a 50 percent average gradient and is located northeast to east of the subject lots. Four test pits were excavated to characterize the subsurface conditionss on Lots l and 2. The site soils consist of Advance Outwash Sand overlain by fill. Within I 5 feet of the ton of slope we observed that the filt thickens toward the slope indicating that low areas along the t��p of the slope were filled when the site was regraded many years ago. We observed no indicators of slope instability, such as slumps, scarps, or tension cracks. The slope is vegetated with mature large trees that do not show signs of slope instability. It is our professional opinion that Lots 1 & 2 of the Rose Short Plat are cunently stable and wiil remain stable during and after the proposed development, provided the recomrnendations contained herein are implemented. 7'here is a low to moderate potential for shailow surficial landslides in the loose surficial soil on the hillside, primarily during the wet winter/spring months. The shailoiv slides should be limited to the top 3 to'S feet. Deep seated slides are not anticipated. Based on the results oFthis study, it is our opinion that Lots 1 and 2 can be developed with singl•� family residences. We recommend a minimum building setback of 20 feet from the top of the slope if the homes are supported on spread footing foundations. The setback may be reduced to 13240 NE 20th Street,Suite 12 • Belleuve,Washington 98005 Phone 4251649-8J57 • FAX 4251649-8758 . { �� August 5, 2003 G-i 541 , ' Lots 1 & 2 - Rose Short Plat Page ii Geotechnical Engineering Study 15 feet provided foundations and decks located closer than 20 feet to the top of the slope are supported on piles. Spread footing foundations should be supported on the native site soils below the root aone or on structural fill that extends down to the native soils below the root zone. To prevent potential settlement the top two feet of native soil underlying foundations and slab-on-grade floors should be compacted to achieve a dense and unyielding subgrade. To improve the stability of the slope, we recommend co(lected surf'ace water from impervious surfaces be dispersed over a wide area or be tight-Gned to discharge into the creek at the bottom of the steep slope. We do not recommend that surface water be concentrated at the top of the slope using a dispersion or infiltration trench. Our recommendations, along with other geotechnical aspects of the project, are discussed in mure detail in the text of the attached report. If you have any questions regarding this report or need � additional consultation, p(ease feel free to call us. Sincerely, GEO GROUP NORTHWEST,INC. � ti�� e~ °�' c William Chan PE. � � g� Principal - '�zo�� ONAI. EXPIRES: 2/19/ I � GEO Group Northwest, Inc. � � � � , - ' ; TABLE OF CONTENTS ' Project No. G-l 541 1.0 INTRODUCTION I'a¢e 1.1 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Scope of Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 SITE CONDITIONS 2.1 Surface Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Subsurface Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3.0 SEISMICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.0 DISCUSSION AND RECOMMENDATION5 4.l General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.2 Slope Stability Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.3 Steep Slope Building Setback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.4 Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.4.1 Subgrade Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S 4.4.2 Conventional Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.4.3 Pipe Pile Supported Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.5 Excavations and Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.6 Wet Weather Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.6.1 Subgrade Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 � 4.7 Structural Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.8 Permanent Basernent and Conventional Retaining Walls . . . . . . . . . . . . . . . . . . . . . . 9 4.9 Slab-On-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.10 Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.0 LIMITATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.0 ADD[TIONAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 LLLUSTRATIONS Plate 1 - Vicinity Map Piate 2 - Site Plan Plate 3 - Footing Drain Detail APPENDIX A: USCS Legend & Test Pit Logs GEO Group Northwest, Inc. I• 4 1 � � GEOTECHNICAL ENGINEERING S1'UDY . E � LOTS 1 & 2-ROSE SHORT PLAT 3414 NE 17T"PLACE ' RENTON,WASHIIVGTON G1541 1.0 INTRODUCTIQN 1.1 PROJECT DESCRIPTION Single family homes are proposed to be constructed on Lot 1 and Lot 2 of the Rose Sliort Plat. No conceptual siting or architect plans were available at the time of the writing of this geotechnical engineering study. 1.2 SCOPE OF SERVICES The scope of our services included the following: • An evaluation of the subsurface soil and groundwater conditions in Lot l and L.ot 2 by excavating test pits with a backhoe. • Logging of the test pits and collection of representative soil samples for examination a•:d laboratory testing for moisture content; • Evaluation of the site conditions and preparation of recommendations addressing slope stability, building setback recommendations, site preparation and earthwork, criteria for foundations, floor� slabs, structural fill, drainage, and subgrade stabilization. � Preparation of this geotechnical engineering report with our activities, 6ndin�s, conclusions, and recommendations for the proposed development c�f I,ots 1 & 2 This report has been prepared for the specific application to this site f��r the exclusive use of th� property owner, Mr. Ricker, and his representatives. We recommend that this report in its entirety be included in the project contract documents for the information c�f the contract�r GEO Group Northwest, Inc. i • ►, � ; August 5, 2003 G-I 541 ' Lots 1 & 2 - Rose Short Plat Page 2 , Geotechnical Engineering Study 2.0 SITE CONDITIONS 2.1 SURFACE CO(YDITIONS The project site is located in the Renton Highlands, on the north side of NE 17"' Place, as showa� on the Vicinity Map, Plate 1 and Site Plan, Plate 2. The short plat is comprised of three single family residential lots (Lots l, 2, and 3) and a steeply sloped native growth protection area (Tract A). Lot 3 is developed with a single family residence. Tract A is located northeast of the three lots and has an average gradient of 50 percent and a slope height of about 60 feet. Honey Creek cuts across Tract A at the base of the slope. We understand there is a sewer main easement near the base of the slope. This report addresses the proposed development of Lots 1 and 2. The northeastern property lines of Lots 1, 2, and 3 are approximately located at the tvp of the steep slope of Tract A(Top of Bank as indicated on the Site Plan, Plate 2). Lots 1 and 2 are irregular in shape with dimensions as shown on the Site Plan, Plate 2. Lots 1 and 2 are relatively flat, sloping down slightly to the northeast with elevations ranging from about 3 56 feet at the southwest corner of Lot 2 to elevation 348 feet along the top of the slope. Vegetation on Lots 1 and 2 consists of grass. Vegetation consists of large deciduous trees, evergreen trees, and i underbrush within Tract A. � 2.2 SUBSURFACE COND[TIONS According to the Preliminary Geologic Map and Brief Description of the Coal Fields of King County, Washington, published by the U. S. Geological Survey, dated 1945, the project site area soils are mapped as glacial drift(Qg). The glacial drift soils are undifferentiated and include proglacial, glacial, and recessional deposits formed during the last glaciation period dating somt 12,000 to 14,000 years ago. A total of four test pits were excavated on Lots 1 and 2 to characterize the subsurface conditions. The test pits were logged by an engineering geologist from Geo Group Northwest, Inc. Test pit depths varied from 3 to 8 feet. The site soils consist of 1.5 to 3.5 feet of loose to dense silty Sand with gravel (Fill), underlain by 1 to 3 feet of inedium dense silty Sand with pebbly gravel, roots and some top soil (roodtop soil zone). Underlying the top soiUroot zone is medium dense to GEO Group Northwest, Inc. � ` . August 5, 2003 G-154 l , � Lots 1 & 2 - Rose Short Plat Pag�� 3 Geotechnical Engineering Study and some top soil (roodtop soil zone). Underlying the top soil/root zone is medium dense to dense Sand with some pebbly gravel. The soils aze interpreted as Advance Outwash Sand deposited in advance of the glacier. For a more complete description of the site soils please refer to the Test Pit Logs in Appendix A at the back of this report. No groundwater seepage was observed during our site reconnaissance and groundwater seepagP was not encountered in the test pits. It is important to note that seepage levels and groundwater levels can fluctuate seasonally, depending on rainfa(l, surface runoff and other factors. 3.0 SEISMICITY According to the 1997 Uniform Building Code(UBC), Western Washington is classified as Seismic Zone 3, with a Seismic Zone Factor, Z, of 0,30 (Table 16-1). The soil soils correspond to a Soil Profile Type S�, Very Dense Soil (Table 16-J), a 5eismic Coefficient C�of 0.33 (Table 16-Q) and the Seismic Coefficient C� of 0.45 (Table 16-R). The site soils are not saturated an� have a minimal risk of liquefaction during a seismic event. I 4.0 DISCUSSION AND RECOMMENDAT`IONS 4.1 GENERAL The main geotechnical issues for development of the lots include the stability of the steep slope. erosion potential, building setback from the top of the slope, foundation support, foundation design criteria, structural fill placement and compaction criteria, subgrade preparation for slab-��n- grade floors, and drainage. 4.2 SLOPE STABILITY EVALUATION The average gradient of the slope below Lots 1 and 2 is 50 percent (26.6 degrees) or 2H:1 V (Horizontal:Vertical), and the slope is about 60 feet tall. The medium dense to dense clean sand on the slope has an estimated angle of friction of 33 to 35 degrees. We observed no indicators of slope instability, such as slumps, scarps, or tension cracks. No groundwater seepage was ' observed on the slope, although our site reconnaissance was performed during the dry summer GEO Group Northwest, Inc. i ' i � August S, 2003 G-l 54 l • Lots 1 & 2 - Etose Short Plat Pagc: 4 Geotechnical Engineering 5tudy months. The slope is vegetated with mature large trees, the trunks of which are generally straigi�t indicating that the near surface soils are generally stable. We estimate that the potential for landslides or mud-flows is low to moderate, unless groundwater seepage occurs on the slope causing erosion and over-steepening of the embankment. It is our experience that such slides a�y typically shallow, limited to the surficial 3 to 5 feet. Deep seated slides are not anticipated. In tlie event of a shatlow slide, the slide zone is not anticipated to impact an area beyond about 5 feet from the top of the slope. To mitigate the potential for such slides we recommend that the trees and vegetation on the slope be maintained. Yard waste and other types of debris should be removed from the slope to promote heathy vegetation on the slope. Storm water runoff should not be concentrated on the slope or within 30 feet of the top of slope. We recommend concentrated storm water be tight-lined to the creek at the base of the slope or be dispersed across a large area of the site, similarly to the way the water is dispersed on the lots currently. It is our professional opinion that Lots 1 & 2 of the Rose Short Plat are currently stable and wil' remain stable during and after the proposed development, provided the trees and vegetation on the slope are maintained and the recommendations contained herein are implemented. 4.3 STEEP SLOPE BUILDING SETBACK Based on the site conditions, it is our professional opinion that a building setback of l 5 feet fro!n the top of the slope is acceptable provided that building foundations located closer than 20 feet from the top of the s(ope are supported by piles. A minimum building setback of 20 feet from t`�e top of the slope is acceptable for structures supported by conventional spread footings, provide:1 the foundation walls facing the slope are embedded a minimum of 3 feet below the finished exterior grade. There is no existing vegetative buffer behind the top of slope. The vegetation was removed some time ago and Lots 1 and 2 are grass covered. It is our opinion that a vegetative buffer in addition to the building setback is not necessary. 4.4 FOUNDATIONS Foundations and deck supports located closer than 20 feet from the top of the slope should be >>ile supported. Piles may consist of pipe piles. Foundations located 20 feet or greater from the toF of the slope may be supported on conventional spread footing foundations, consisting of continuo�as strip footings and individual column footings. GEO Group Northwest,Inc. t � �:; ' August 5, 2003 G-15�41 . ' Lots l & 2 - Rose Short Plat PagP S Geotechnical Engineering Study 4.4.1 Subgrade Preparation The fill should be stripped, and the root zone soils removed within the footprint of the homes. To provide adequate support for foundation footings, we recommend supporting foundation footings directly on dense soils below the root zone or on stnictural fill that extends down to the dense soil. The sandy native site soils may need to be confined to achieve compaction. To confine the sandy soils we recommend placing a 12 inch thick layer of crushed rock, recycled concrete, or gravelly structural fill, compacted as specified in the Struclural Fill Specificatio�is section of this report. Structurat fill should be placed as a prism under the footings to adequately transfer the loads to the underiying soils, extending down from the inside and outside edges of the footing at 1H:1 V. The native site soils should be compacted until dense and unyielding prior to placemen� of structura! fill. . 4.4.2 Conventional Foundations i The structural fill should extend below the footing at 1H:1 V forming a prism under the footing. We recommend that the foundation footings facing the steep slope be deepened so they are embedded a minimum of 3 feet below the finished grade, instead of the standard 18 inches. We recommend conventional foundations be constructed using the following design criteria: • Allowable bearing pressure, including all dead and live loads: = 2,000 psf • Minimum depth to bottom of perimeter footing below adjacent exterior grade. - General — 18 incl�es - Foundation walls facing steep slope -- 36 inc-�es • Minimum depth to bottom of interior footings below top of floor slab — 12 inc��es • Minimum width of wall footings — 16 inc tes • Minimum lateral dimension of column footings — 24 inc,ies • Estimated post-construction settlement = 1/4 inch � Estimated post-construction differential settlement; across building width = 1/4 i��ch GEO Group Northwest, Inc. I ; ------ I r � It i August 5, 2003 G-154 I , � Lots 1 & 2 - Rose Short Plat Page 6 Geotechnical Engineering Study A one-third increase in the above allowable bearing pressures can be used when considering short- term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the existing undisturbed soil or backfilled with a compacted fill meeting the requirements of structural fill. Our recommended parameters are as follows: • Passive Pressure(Lateral Resistance) = 300 pcf equivalent fiuid pressure; • Coefficient of Friction(Friction Factor) = 0,35 4.4.3 Pipe Pile Supported Foundations Foundations and deck supports located between 15 and 20 feet from the top of the slope may be , supported on 3-inch minimum diameter galvanized steel pipe piles. Piles should be tied together with grade beams to generate lateral resistance and the grade beam shoutd be embedded three feet � below the finished grade. Pile spacing and the number of piles required wiil need to be designed � by a structural engineer. The pipe piles should be driven to the refusal criteria below:. Pipe Pile Pile Hammer Teledyne Refusal Criteria Allowable Diameter Specification Size Hammer (Seconds Per Inch) Capacity, 3 inch Schedule 40 650 lb TB225 16 6 tons The refusal criteria and allowable capacity may be different for other hammer weights, manufactures, and pile sizes. Please contact us if other driving equipment or pile sizes are to be used. By themselves, pipe piles do not generate lateral capacities. Lateral forces can be resisted by thE; passive earth pressures acting on grade beams, and friction with the subgrade. To fulty mobilize the passive pressure resistance, the grade beams must be pvured "neat" against compacted fill, Our recommended allowable passive soil pressure for lateral resistance is 300 pcf equivalent fluid weight. A coefficient of friction of 0.35 may be used between the subgrade and the foundation. GEO Group Northwest, Inc. i e ! � ` � August 5, 2003 G-1441 . I' ' Lots 1 & 2 - Rose Short Plat Pag,: 7 Geotechnical Engineering Study 4.5 EXCAVATION3 AND SLOPES Temporary cuts greater than 4 feet in depth should be sloped at an inclination no steeper than 1 H:1 V (Horizontal to Vertical). Temporary shoring will be required if excavation slopes of this inclination or flatter cannot be constructed. Permanent cut and fill slopes at the site should be inclined no steeper than 2.SH:1 V. [f groundwater seepage is encountered during construction, excavation of cut slopes should be halted and the cut slopes reevaluated by Geo Group Northwest, Inc 4.6 WET WEATHER CONS[DERATIONS The Soi) Conservation Service c(assifies the site soils as AgD (Alderwood gravelly sandy (oam, �5 to 30 percent slopes), however based on our site exploration it is our opinion that the fill soils , covering the subject lots are composed of reworked glacial till soils from previous grading activities. The reworked glacial till soil corresponds with the AmC (Arents, Alderwood material, 6 to 15 percent slopes) mapped above the site to the southwest. Runoff of AmC is classified as medium, with an erosion haaard of moderate to severe. 5ilt fencing installed below areas to be disturbed should be adequate to control site erosion. During wet weather, stockpiled soils should be covered with plastic sheets to minimize water infiltration and erosion. Exposed soils should be protected by plastic sheeting or straw mulch. For erosion control af�er construction, we recommend the exposed soils be planted with suitabl� ground cover vegetation to reduce erosion and improve the stability of the surficial soil layer. During construction we recommend installing temporary sediment control traps, check dams, a stabilized construction entrance and other erosion control devices and techniques as needed to provide temporary erosion and sediment transport control. The surficial fill soils and root zone soils on the site contain silt, making thern moisture sensitive during wet weather. It is difficult to achieve structural fill compaction requirements with the moisture sensitive soils during wet weather. Soils containing roots and organics should not be used as structural fill. During dry weather the non-organic native site soils may be used as structural fill provided the materia] is near its optimum moisture content for compaction purpos::s and the material can achieve the required compaction specifications. GEO Group I�iorthwest, Inc. August 5, 2003 G-1 S��I Lots 1 & 2 - Rose Short Plat Page 8 Geotechnical Engineering Study 4.6.1 Subgrade Stabilizxtion We do not anticipate problems with subgrade stability, however the surficial fill soils could rut and pump excessively during wet weather. In the event subgrade stabilization is needed, we recommend removing the unsuitable soils and replacing them with a granular structural fill. A woven geotextile fabric, such as Mirafi SOOX or equivalent, may be required below the bridging soils to provide base reinforcement, separation and stabilization. The geotechnical engineer should provide specific subgrade stabilization recommendations based on the site conditions. 4.7 STRUCTURAL FILL Structural fill is defined as all fill material used to achieve design site elevations adjacent to basement walls and below foundations, floor slabs, patios, porches, sidewalks, and pavements. Structural fill material shou(d be placed at or near the optimum moisture content that enables th � soil :o be compacted to the highest dry density for a given compaction effort. During dry weather, any compactable non-organic soil with gravel sizes of 3 inches or less may be used as structural fill. Structural fill should be placed in thin horizontal lifts not exceeding ten (10) inches in laose thickness. Each lift should be compacted to the minimum percentages shown in the ta��e below in accordance with ASTM Test Designation D-1557 (Modified Proctor). STRUCTURAL FILL COMPACTION CRtTERIA Maximum LiR Thickness 10-inches (loose) MINIMUM COMPAC7'lON APPLICATION % of Maximum Dry Density ASTM D-1557 Modified Proctor Under driveways, sidewalks, patios,porches, 95%for the top 12-inches ete., &adjacent to ve:rtical drain mats 90%below the top l2-inches Under foundation footings and 95"/0 slab-on-grade floors GEO Group Northwest, Inc. 1 � August 5, 2003 G-1541 • " Lots 1 & 2 - Rose Short P(at Page 9 Geotechnical Engineering Study During wet weather conditions we recommend an import structural fill material meeting the following criteria to achieve the compaction specifications: 1. Be free draining, granular material, which contains no more than five (5) percent fines (silt and clay-size particles passing the No. 200 mesh sieve); 2. Be f'ree of organic and other deleterious substaT�ces; 3. Have a maximum size of three(3) inches. 4.8 PERMANENT BASEMEIVT AND COIYVENTIONAL RETALNING WALLS Permanent basement walls restrained horizontally on top are considered unyie(ding and should be designed for a lateral soil pressure under the at-rest condition; while conventional reinforced concrete walls free to rotate on top should be designed for a active lateral soil pressure. Active Earth Pressure Conventional reinforced concrete walls that are designed to yield an amount equal to O.Oc)2 times the wall height, should be designed to resist the latera! earth pressure imposed by a�� equivalent fluid with a unit weight of: • 35 pcf for level backfill behind yielding retaining walls At-Rest Earth Pressure Walls supported horizontally by floor stabs are considered unyielding and should be designed for lateral soil pressure under the at-rest condition. The design lateral soil pressure should have an equivalent fluid pressure of: • 50 pcf for level ground behind permanent unyielding retaining walls The above values are based on the wall backfill being fully drained. The above values do not inciude the effects of surcharges. For sloped ground behind the wall, a surcharge load equival�nt to 50 percent of the soil height above the wall should be considered in addition to the above so� pressures. Construction or driveway traffic above the walls can be assumed to have a surchargt• equivalent to 2 feet of soil. GEO Group Northwest, lnc. , August 5, 2003 U-15�11 Lots 1 & 2 - Rose Short Plat Page 1 1 Geotechnical Engineering Study 4.10 DRAINAGE During construction, water should not be allowed to stand in areas where footings, slabs or pavements are to be constructed. Water collected from impervious surfaces should be tightlined to the creek at the base of the slope or be dispersed across the lots. Surface water should not be concentrated on the slope or at the top of the slope. Dispersion trenches should be kept a minimum of 30 feet from t6e top of the slope. Footing drains, consisting of four (4) inch minimum diameter, perforated or slotted, rigid drain pipe should be installed at or near the bottom of the footings with a gradient suf�icient to genera�e flow, as illustrated on the Footing Drain Detail, Plate 3. The drains should be bedded on, surrounded by, and covered with washed gravel. The washed rock and drain line should be completely sunounded by a non-woven geotextile filter fabric, such as Mir� 140N, or equivalent. Footing drains should be tightlined separately from the roof drains. Cleanouts are recommended at strategic locations to allow for periodic maintenance. 5.0 LIMITATIONS Our findings and recommendations stated herein are based on the field observations, our experience and judgement. In the event the soil conditions vary from those described herein, Geo Group Northwest, Inc. should be notified and the recommendations herein be re-evaluated. The recommendations herein are our professional opinion derived in a manner consistent with the le��el of care and skill ordinarily exercised by other members of the profession currently practicing , under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. 6.0 ADDITIONAL SERVICES We recommend that Geo Group Northwest Inc. be retained to perform a general review of the final design and specifications of the proposed development to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction documents. We also recommend that Geo Group Northwest Inc. be retained to GEO Group Northwest, [nc. i..` � August 5, 2003 G-1541 � ' Lots 1 & 2 - Rose Shart Plat Page 12 Geotechnical Engineering Study provide monitoring and testing services for geotechnical-related work during construction. This is to observe compliance with the design concepts, specifications or recommendations and to aliow design changes in the event substance conditions differ from those anticipated prior to the start of construction. Special geotechnical inspections at the time of construction should include: • Structural fill placement and compaction testing • Foundation soi( bearing capacity • Subsurface drainage Please call us should you have any questions regazding this report. Respectfully Submitted, a W�s h;,� , GEO GROUP NORTIiWEST, INC. �e y� ry . , `� � /�`� 'x` ' / �. ��.y Wade Lassey � '��n�e1�1;6Qo,o4• � Engineering Geologist � Wade J. L�ssey ; . William Chang, P.E. tp►M C 'I �. . . ti W � Pnnc�pal 3,ti�,o�.. ��{y_��'�+� � � } �� I Y.• I �� 011TA1, EXPIRES: 191e� j l. �� . I I� ( � � GEO Group Northwest, Inc. ; ILLUSTRATIONS G1541 I GEO Group Northwest, Inc. a 0 1�00' 30W' Approximate Scale: l inch=1500 teet ' ;" - -{' � W ` `' � I ^y� �,� o D»�. 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VICINITY 1V1AP Group Northwest, Inc. LOTS 1 & 2 - ROSE SHORT PLAT GeotechnicalEngineers,Geologists,8 3�41�1 NE 17TH PLACE ' Env�ronrtentalSc�entsts RENTON�WASHINGTUN SCALE 1°=1500' DATE 8/S/O3 AtADE W.TL CHI{D WC JOriIYO. G_I541 P1.�1T� l_ � ,r _ ...,__...._ ._.. � -. � :-...:, �. . � . . . . . .. . . . . . . . . . ,. _ . . . _ . �., . _ U N P L A TTE� - _ sE co� oF • -;se , y�° � NE4�,NE4,SE4 ; - . ' \ '� `�A�„ � �'. � J,. j� SEC 4-23-05 � � � \ �c \ �� 3�� \� 6.43' `T�� \� ��'�\ � ` CatLG POSI�IOH , \ t � �� 1962_10(C�4L) � S88'�4'32"E �� ,; � ��. � \ \ � � � S887 4'32"E " _ - ,`'T,—00 ` ` � �7.80` N�6't�'3' � � �,,� .�2' �, � , \ �\ � � •, � —• 5.�5'(CAL;� 4 � � �� `�� '�,�� \� \\ \� \� � -- \.� C1TY OF RENTON MOt� �716 LANJSCAPING . � EAScMENT � \� •��.�! '9Q `, � � � TQp 0�`�ANK �� \� � lNTER QF NE 19TH ST & R�c �s�os-2ss�-2 � �, � �� 5�=�- (�r�) � � � � - � e� UN10N AVE NE, FND " BRASS 2Q' NW CGRNER 0 \`-�_�_ �. `�� LOT 3 �,� �..q�, ��, � �� -�S�cc,�� \ - �V DiSK W/PUNCH IN C�NC SW4,NW4,SE4 � �.. �` T s� .� \��j��.. - �� \ \. � IN CASc (1—Q21 SEC 4-23-05� ''� �.�� ":`I � �� \ \ \ t"% \ o" �Z� \ ''� `' / TP-3 ti� '� \ \ \ �2 \ �� \,`�� `� � � �LOT.�2 R• s. �R � TR�4CT � � �, � 3 .�.� F-- ,^^ —L— � , � �. � {NGPE)�, \ ��, ; W,W , , .� "' �, ;,�„� � � � �' ' '�, �.` , � ; Y�, �, � N�v . �� `•` � , � —`''—� tn� � �\ �. } �' v0 • �` � -•-.� � �-1 ` � � � � � � [x�000 \ ' C� O�� -, ` _ � ` '�Al \ � � � p �;�5 �� j1�` � ,.\ _ . 1 �� 50' 1°0' � \�`��_ ��`_�� LOT 1'� `. '� `� `� '� `� �ti �p zz Scale: 1 inch=50 feei \ ` � �`\ TP-; ""�t�, \ \ \ ` \ � \ r.w `�\ � -.� \�,� �� • � � � � \ �'� CtTY OF RENTON MON #1894 nr,�o�, �� ' � _ `'�� 2 \ � \ \ \ {— _ INTER OF NE SUNSET*BLVD & � \ �. �' .� �, ��, � - '� ti 1 � � - � � ' ` Q UN10N AVE NE, FND BRASS `� � � •, 1, F . = TOP OF BANK\ \ � , \ • =1 DISK W/PUNCH IN CONC _ ��I_ , � .' � ;,, _ � , ;� �� \\ �\ � \ \ � � !N CASE (1-02) ----� _ ', •` \ \- � �`-� Z �c;�s� ��. � . ��`, � � � _ � � ; _t ;� �. � ` �,�� 2�9Qt� ` �-� � � � . � - \.. _____ •.� ,� � d � l LEGEND � ��,�� „ ,�, �� ; � \ � � ` _ . _ � � �� ..,�.� '�:\' \\ `.�'�,\�=. �ti,'- �� i � t34.�• \ � Test Pit�umber& 1 `�' ,�' •�_ `�� nA''� � 1` \�� ` �� Appro�mate Locarion � � � �, ; �e - � �� ,\� TP-1 -, 3 � ",,, , . v � � �� 'tS' \:''� �i= t-° ` O � L HOn1`� c:!?�� P,�;='K PLA T � � ' � � ,`Jv , ^;��+` � ��EY�\�'Q� ,�'�Q�FC`�c�'/ ,4 ; Site Plan Adapted From Rose Short Plat. Topo� � �v K �— � • _ i R�360�.00 \\ � F Uti�ities Plan Prepared by Touma En�ineers. April ?003. alIl ✓�'L ... Pfl Gc .�i EX SSAIH (OR AIH) � \ � L�S2.� \ � � � lN/V Q = 367. 8'� CDNC /N ,� � � TQ�ps�j�"�s+ ___ � !NV EL = 361. 6" 8" CL1N� Ot! �.� � �3� wA� M�s LFGEIV D '� ,y,'b 'k � N NE )7th PLq CE � s�r�ie�c 9+w� N �'6a¢` �' D( CCA�f�t ��l/uT m IX S9ff � AECQIIOUS A?fE �__ _ � � � � —' � � N�V �STJr' 8'COVVC /N ❑ Ex Cn7r�e�9rv �cr � cv - — j � '� 1NV � _ ��57' 8' CONC OUT g �Ntr��a.wr � ca�r�x natF � ln ' f � � i °l� ^ IIOITER 1EJFR 4 UJ�/N f�QCE t_. � j 1 m 1ELF�F�E 'A�fA7E o AfAR. BQ.Y 2 rJ� � � � r� ; :� � \ iG GAS 161LfE �rm AOC7�R1' � . � - �' -' _ �� . � 1F1ZrMA7�E YiW�F —81 1kaN N CAS� �., �l � � P�OM6�1NGCT p fi7U10 AEBAR a GP � � + C£N7ER[!NE CUR1E DATA �" aj \ o �T/fXE G�IiGN PFE M ft--.3�0� ` � ti s Ma+�c�u � I L—?79 15 � � 4' PE�ES�►M1►Pt�9r Bu77�N PotE Tarr=ll,T 66 e ry a � t_� l,�efta■.3778'S5' y'-9� � 1RAfF1�C.�+WC71pn Bo7C s� � SITE PLAIv � � Group Northwest, TI1C. LOTS 1 &2-ROSE SH�RT PI.AT c�ucM;�,i�,�n.«s,c.a,�,a 3414 NE 11TH PLACE, � �°""�+�� RENTON,WASHINGTON 3CAL,E 1�_�0' DATE 8/5/43 MADE W1I. (� WC JOBNO. G-1541 PLATE 2 I ._.... .:, ; ;: �:�t`,�, w 4 , FOUNDATION f�'ALL . � Slob � • _ . . Slope to dmin - , :�:;:;:;:�:�:�•�:•�� : . , . : � . .• . ,: . � � � , q . . - . n . . .. ��€ . . i: I ' � r , � o � O 0 : ��'��' � � . �` 6 to 1? Relahve o o O • �� Intptrnteable Cap 0 � � ° e o ' � ,�� ` o COMPACTED o a - _ _ GEOTEX77LE � FILL o - FILTfiR FABRIC �� ° ° � � (Mir+aft 140N,or o o � � o ' _ equivalen�) O 0 0 � . . Free dmining �►taterral, o o _ (Waahed rock) `"'� "� o ,,r.;�. o <: �:.�,^ � .� - . �f�'1 c; '»..'j.,.'f',k� Y 2 . . . . . Fnor�lvc D�rN• .�''' ;>�:r: � . . Minimum 4-inch diameter�lotted or ?°�'' FO�TING perforot�d rigid PVC pipe with positive �/_= �j'"`�� ' s /nvert gradisret to discharge � NOT TO SCALE NOTES: 1.) Do not replace rigid PVC pipe with flexible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should be tight jointed and laid with perforations or slots down, with positive gradient to discharge. 3.) Do not connect roof downspout drains into the footing drain Lines. 4.) Exterior backfill should be compacted to 90%of maximum dry density based on Modified Proctor. The top 12-inches to be compacted to 95%of maximum dry density if bacicfill is to support sidewa(ks, driveway,etc. Interior backfill below floor slab should be compacted to 95°/a. TYPICAL FOOTING DRAIN DETA[L Group Northwest, Inc. LOTS 1 &2- ROSE SEIORT PLAT ceaecnaica�5g�ne«s,Geo�oo:ra,a 3414 NE 17TH PLACE �"'�O""1B"''��°""'�' RENTON,WASHINGTON SCALF, NONE ��n�rr, R/5/03 MADE W1L CHKD WC •lOBIV�). G-l�dl PI,.�TF. z � w i � . � APPENDIX A TEST PIT LOGS G1541 GEO Group Northwest, Inc. , � ., • n i w � ' LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST UNIFIED SOIL CIr4S3lFICATION SYSTEM USCS) MAIOR DNISION ��. TYPICAI.D�TION LA90RATORY CLASSIFlCJ1T10N C�IA a�w c�v �or�o�aw►ve.s,c�va��ro cu=�oeo i o�q�.rr s,.�� l7RAVB.9 I�CiIAtE.11TlLfi CR NO FRIE� �� Co s(p3p�)/lDt�'O�q b�n 1�nd 3 PF7�ITAop oF — ciR/1VH8 (�a no POORLY ORA�ED GRAVB9.AND ciRAAVB-3AND OR/1VQ AND 9AND COARSE ��TF�n Wf �I � MD�TLXtES Uf�LE oR NO FNES FROM GRAIN SQE NOT MEE7Ndf3/IBOVE RBOlJ�E1MBiT9 Corsr ciraYu OfSiRIBUiION ORAlEO SOKS ��Th�n No.1 Cl1RVE ATTHtBBl4 I�fIS B�OW ��) DR�Y Gill 9L7Y ORAVB..3,GRAVELSANO-SI.T MOCTURE3 '�'l.rE �/+yg,3 �� a P.L tF.lS 1}iM11 ATT91P610 I.IYIR8 ABOVE (w��sana � CLAYEY ORA��1sl9.SM�CLAY COARSE QRAIPI� IX��12% ��L�. , gp�� a P.I.WIIC+THMI 7 �� WBL ORAOEO SA11D3.I�RAVELLY 3ANO8. �Q�� +=(��1d)Dl�i�1M t - UTTLE OR NO F7rE3 Co=(09D=)I N1�'�!q p�lw��n 1�nd 3 SAMD! ��O�� (qrh a ro � POORLY(iR/1�EQ 3A1�6,ORAVEIIY SANDS, <5%Flna G�ined. ��E p�� Tlrn H�f ��) UTTiF OR NO F�IE9 QW�6P,3W.SP W��w 9��Iar Than No. Tlsn No.700 4`�'�) A7'THi�ic3 lMTS BB.OW �12%Fln�Gwinad: �� ORTY SM 9LTY SAt�.9.SMO-.91.T MIXTt�tEB GM,OC.9M,3C CONTB�T OF �A'LNE g��pg �� wilh PS 16R31HMl � � 5 Lo 127�Flne IXC�R0.S 1276 ATTERBHtO lJ�TS ABOVE ��M 9C Cl11YEY SAPO-4,3MOdxJ1Y MDCiURE3 O�h�s�use dwl •J1'LNE s�npds wYA P.1 AAORE THAN 7 SLT9 Uqi�fd Umk IlrOftOAMC SI173�ROCX ROUR SMIOV S�.7S (B�Io�N p.�yM an <50% � OF SLK3FfT PlAB�ICfTY � 1 p�yp�r q�� PI.ASi1GTY CHART A-lin� � FINE�GRAl1� N�� Uquld LMIt M10R6M11C 31L75,dMGCE0U3 0R yp FOR 9OIL P/LS9ND 90L3 ��'ir�) �lf07i � OIATOMACEOl1B.FN�E 3ANOV OR 91LTY 90L NO.�0 SEVB CM a OM � CLAYB tJa�id LJm� MOROANIC CLAYB OF lOW PI.A3TICITY, y��p �b�� CL q1AVH.LY.9M1DY�OR 9�.TY ClAV3,CLE/W 1!� CL11Y8 � PI�tloLY Chrf. 30 ��b' liquid LMnit NOROMMC CiJ11/9 OF FNGFI PlA8i1CiTY.FAT � qpr� >,� � p,/1VS CL or OL AAa�Tirn Filf � W�Iplk�rYM l3qu�d LWnk OROAPMC SN.TB AND aR0/WIC 31L7Y CiJ1YS OF � ��'� TMn No.�0 �� <� a' LONV Pl.A8ilpiY 10 9few — lB�low A1M»an 7 �C�l �� OH dROANIC CLAYS oF FM011 P1.ASTIQTY < � !- 0 0 �0 1D 30 �0 50 90 70 � 90 100 1�0 F�(iFLY 0(tOMYC SOIL9 R PEATAPD OTHER HOFLY OROANIC 901.4 L1QU�LMT C16) 301L PARTICLE 3f� eiB�l@W.GlJ1�ANCE OF 301L BiO1NEERING U.S.sTMa11RD 31E1f! 1'ltOPB'tTE1 PROM STAPOAR�PEf1E71tAT10N TEST(�PT) p�pN Patah+g I�YMd s11NDY sO1Ls s��rr a cuv��s SIN►� � 31�'Y! �� Blew Ral�rs Fietlon Blow U�0°^�� mm) (�) Co1rM� DerM�r Angb OeseAPtlon Cou� �� /�npdvn �.r►cur �oo o.o� N �c �,d�.. N q�.ea � a-� oas v«r�.s <2— - <o.as v�mrt � s+o aa�s s�xoo ame ••to �a-ae ae-so ��.. z-a axs-aao sw� M�IUA1 HO 200 MO O.�Zf 10•3D 36-S�S 29-35 AileiNum Oanse 4-8 0.5D-1.m Madhrn u�fl t��IR3E f1 1.75 R10 200 30-CO 9S-aS 35-42 Denae B-15 1.00-200 Stlfl O �30 �-10C 36-Ie Very D�se 15-30 200-4.00 Very StiR FM/E /9 �Wt 1.75 >30 >1.00 Fird COARBE 7e 18 COl�lB! 7A mm b 2D3 mm � >200mm • Group Northwest, Inc. OwMehnkal E�qb�s.Cieo b glsb.3 RO�x >7�mm Eflvhonenenh13da1ftists �°�� ts2�o HE 2ah sha.c,su�r.�2 B.neNb,w� seaae ROCX >O.M cubk;meter in vdisne �»(�1 A�O�b�57 Fax(d25�848�875D �' A�; ` � L!` 1 �, �. c TEST PIT NO. TP-1 LO(iOED BY W7L EXCAVATION DATE: 8/1/03 GROUND ELEV. 350 feet(f) OEPTH SAMPLE MOISTURE OTHER R. USCS SOIL DESCRIPTION No. % COMMENTS Siltv SAND with eravel, light brown, loose to medium dense, II ' SM �,�gILL). 3 to 4 foet thick&t�uckens towazd slope. S� �4 '�I -- ------------------------- SAND with silt,darker bmwn,roots and top soil,fine grained, 6 SM some gravel,loose to medium dense,dry(Top Soil& Root S2 10.6 Zone) 1 to 3 feet thick&thickens toward slope. sP SAND, reddish tan to gray,fine grained,mediam dense to dense, S3 5.1 some fine gravel,damp(Advance Outwash Sand) Total Depth=8 feet �� No Water Seepage TEST PIT NO. TP-2 LOO(iED BY W7L EXCAVATION DATE: 8/1/03 GROUND ELEV. 35U feet(t) DEPTH SAMPLE MOISTURE OTHER R. USCS SOIL DESCRIPTION No. X CUMMENTS SM Siltv SAND with Sravel, light brown, loose to medium dense, S1 5.8 dry(FILL). -- --------------------------- sM SAND with silt.darker brown,some gravel,roots(Root Zonc) g2 7.� 6 -- --------------------------- 5P SAND,tan to gray, minor oxidation at top,fine grained, medium dense to dense,damp(Advance Outwash Sand) S3 4.5 10 Totai Deptt�=9 feet No Water Seepage TEST PIT LOGS Group Northwest, Inc. ROSESHORTPLAT LOTS 1 &2 Oeotechnbel Enqinaer�s,Geob�su,8 RENTON,WASHINGTON Fm•►onmenMl Sclerdists Pro,ject No. G1541 PLATF A2 � �s w / TEST PIT NO. TP-3 L�OOED BY W1L EXCAVATION DATE: 8/1/03 GROUND ELEV. 350;eCt(f) DEPTH BAMPLE MOISTURE OTMER R. USCS SOIL DESCRIPTION No. '�i COMMENTS SM Siltv SAND with Qravel.gray,medium dense,dry(FILL). S1 4.6 -- ------------------------- \SM Siltv SAND, reddish brown, roots,Fine grained, medium dense,r S2 R.7 `_ dr�'(itootZone)-----------------J� -Probel2" 6 SAND,o�cidized reddish brown to 3.5 feet, S3 5.6 5P then tan to gray,fine grained,medium dense to dense, moist -Probe 12" below G feet(f)(Advance Oatwash) Note: Increase in moisture content likely from nearby septic tank. sa ��.3 Total Depth=8 feet �� No Water Seepege TEST PIT NO. TP-4 LOG(;ED BY WJL EXCAVA71oN DATE: 8/1/03 GROUND ELEV. 3'2 feet(f) DEPTH SAMPLE MOISTURE JTHER R. USCS SOIL DESCRIPTION No. °�f► CGMMENTS SM Siltv SAND with p.ravel,light brown, medium dense to dense, FILL . SM �� Sh brown,fine,medium dense to dense,dry S� g.3 _ ?roUe �2� (Advance Outwx�h) Total Depth=3 feet 6 No Water Seepage 10 �� m�c�r� vrr � nrc