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Home My WebLink About03482 - Technical Information Report r �� ► � ` N i � . �' DEVELOPMENT PLANNING � 1� CITY OF RENTON SEP 2 6 2007 C, RECEivEn �, RVT SHORT PLAT Parcel # 516970-0140 �- � _ Technical Information Report E i Renton, Washington , August 8, 2007 i r � � ; " I i � I I � � � -, —— �-� ' , I\ — '— 8716 142n°Avenue NE i i } I Redmond, WA V INdc eosan bqinw�q,t�c. i ,_. �_ ��Z RVT SHORT PLAT Technical Information Report Renton, Washington August 8, 2007 Prepared for: JMT Building 232 Wells Avenue N. Renton, WA 98057 S •�!: ��.�1 �.-�'�1 �',,. . �>>• � �A�� 1}r�� .� �r� �� Y`�� _- .. y } � f:� � 29631 Q ,�• � �7r AF��ST��• .a�� `,� ,.,,ti;��.� E�,�' E�PIRES 7/2/09 � � � `� � 8716 142'd Avenue NE � �� Redmond, WA i Nkk Boswff Englneertg,1nc. JMTB-0701 i J TABLE OF CONTENTS SECTION 1 PROJECT OVERVIEW 3 Pre-developed Site Conditions 3 ' � Post-developed Site CondiUons 3 TECHNICAL INFORI�IATION REPORT(TIR)�'�'ORKSHEET 4 � SECTION 2 CONDITIONS & REQUIREMENTS SUMNiARY 11 � King Counry Surface Water Design Manual Core Requirements 1 1 �� King County Surface�Vater Design b�fanual Special Requirements l 2 SECTION 3 OFF-SITE ANALYSIS 14 Drainage System Description �4 Upstream l 4 I On-site 14 Downstream 14 , Resource Review 1� Problem Descriptions 1� i � A�litigation of Existin�or Potential Problems I S SECTION 4 FLO`�' COVTROL & «'�TER QU.��LITY AI�ALYSIS AND DESIGN 19 1 Existing Site Hydrology l 9 Developed Site Hydrology �y Basin Areas and Runoff Rates (y SECTION 5 CONVEYANCE SYSTENi ANALYSIS AND DESIGN 23 SECTION 6 SPECIAL REPORTS AND STUDIES 24 SECTION 7 OTHER PERMITS 25 SECTION 8 ESC ANALYSIS AND DESIGN 26 SECTION 9 BOND QtiANTITIES,FACILITY SUMI��IARIES AND DECLARATIO'V OF COVENANT 27 Technical Inforrnation Report for RVT Sfiort Plnt Aiegust 8, 2007 SECTION 10 OPERATIONS AND MAINTENANCE MANUAL 28 TABLE OF FIGURES FigureI: Vicinityl�lap..................................................................................................................................................8 I=igure 2:Existing Condition.........................................................................................................................................9 [=igure 3:Developed Condition...................................................................................................................................10 Figure4: Off-site System ............................................................................................................................................16 Figure 5: Existing Hydrology............................................................................................................................... .......21 Figure 6: Developed Hydrolog� ................... �� ...............................................................................................................-- , Tecfinrc�nl Inforrnation Report,far RVT S/tort Plat August 8, 2007 SECTION 1 PROJECT OVERVIEW � The project is a 3-lot short plat on a 0.39-acre property. The property is a single parcel (Parcel Number 516970-0140) with an area of 16,916 square-feet (0.39 acres). The site fronts the south side of NE 18`h Circle and the west side of Duvall Avenue NE (see Figure 1 - Viciniry Map). The proposed development will include two lots that access off NE 18t� Circle and one lot that accesses off Duvall Avenue NE. Frontage improvements to NE 18`i' Circle will consist of sidewalk installed behind the existing curb. Frontage improvements in Duvall Avenue NE include pavement widening and installation of curb, gutter and sidewalk. The improvements to Duvall Avenue will be constructed bv the Citv. Pre-developed Site Conditions The property is currently developed as single family residential. Exiting improvements include a residence, concrete patio and sports-court and gravel driveway. The remainder of the property is covered with lawn and some trees. The existing impervious area is 2,869 square feet. There is no constructed drainage system on-site; roof drainage discharges to grade. Soil is Alderwood sandy, gravelly loam per the NRCS mapping. The tenain is mildly sloping at an a�erage of 1.5 percent down to the southwest. The frontage along NE 18`h Circle is improved with asphalt pavement and curb. Duvall Avenue I�E where it fronts the site has a rough asphalt edge, gravel shoulder and shallow grassed ditch. Post-developed Site Conditions The three proposed developed lots will be developed as single family residential. Plot plans have not yet been developed but the maximum building coverage allowed by zoning (R-8) is 35% or 2,500 square feet, whichever is greater. Frontage improvements will include pavement widenin� and installation of curb, gutter and sidewalk on Duvall Avenue NE, and new sidewalk on NE 18` Circle. The scope of the proposed improvements do not trigger a requirement for formal rate control and �vater quality facilities (see Section 4). Roof and lot drainage will be collected and conveyed in buried pipes to the proposed storm facilities in Duvall Avenue NE. The proposed storm system in Duvall Avenue will be constructed by the City as part of the planned improvements for that road. If this development precedes the City improvements, then the site discharge will be to the existing public storm main located beneath the road pavement on the east side of Duvall Avenue. Perforated stub-outs per the current King County ma�ual will b� provided for each lot. � _--- _ _ � Techr�iic al Informatio�i Rc port Joi�RVT Shor-t Plut Aug«st 8, 200i King County Department of Development and Environmental Services � TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER Part 2 PROJECT LOCATION AND . PROJECT AND . ENGINEER DESCRIPTION .' Project Owner John M. Tharp Project Name RVT Short Plat �, Address 232 Welis Avenue N. Location Renton, WA 98057. Township 23North Phone 206-601-6921 Range SEast Project Engineer Nick Bossoff P.E. .............Section 3 . Company Nick Bossoff Enqineerinq Address/Phone 8716 142�d Ave. NE, Redmond. WA 98052, 425-881-5904 Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS APPLICATION ❑ Subdivision ❑ DFW HPA ❑ Shoreline Management � Short Subdivision ❑ COE 404 ❑ Rockery ❑ Grading ❑ DOE Dam Safety ❑ Structural Vaults ❑ Commercial ❑ FEMA Floodplain ❑ Other ❑ Other ❑ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN - Community Newcastle Drainage Basin May Creek a Technical/nformation Report for RVT Short Plat August 8, 2007 Part 6 SITE CHARACTERISTICS ❑ River ❑ Floodplain ❑ Stream ❑ Wetlands � ❑ Critical Stream Reach ❑ Seeps/Springs ❑ Depressions/Swales ❑ High Groundwater Table ❑ Lake ❑ Groundwater Recharge ❑ Steep Slopes_ ❑ Other � Part 7 OILS S Soil Type Slopes Erosion Potential Erosive Velocities Till . Less than 2% Slight Sliqht Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT � Sec. 3—Off-site Analvsis ❑ ❑ ❑ � ❑ ❑ ❑ Additional Sheets Attached 5 � Technical Information Report for RVT Short Plat August 8, 2007 Part 9 ESC RE�UIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION � Sedimentation Facilities � Stabilize Exposed Surface � Stabilized Construction Entrance � Remove and Restore Temporary ESC � Perimeter Runoff Control Facilities � Clearing and Grading Restrictions � Clean and Remove All Silt and Debris � Cover Practices � Ensure Operation of Permanent Facilities � Construction Sequence ❑ Flag Limits of SAO and open space ❑ Other preservation areas ❑ Other Part 10 Surface Water SystemPart 10 SURFACE WATER SYSTEM ❑ Grass Lined ❑ Tank ❑ Infiltration Method of Analysis Channel ❑ Vault ❑ Depression � Pipe System ❑ Energy ❑ Flow Dispersal SCS SBUH ❑ Open Channel Dissipator ❑ Waiver ❑ Dry Pond ❑ Wetland ❑ Regional Compensation/Mitiga ❑ Wet Pond ❑ Stream Detention tion of Eliminated Site Storage N/A Brief Description of System Operation Runoff collected from lots will be conveved via qerforated stub-out and buried pipe to the street svstem. Facility Related Site Limitations Reference Facility Limitation � !� Tec1¢nical/nformation Report for RVT Short Plat Augc�st 8, 2007 � � Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTS/TRACTS ❑ Cast in Place Vault � Drainage Easement(private) ❑ Retaining Wall ❑ Access Easement ❑ Rockery> 4' High ❑ Native Growth Protection Easement ❑ Structural on Steep Slope ❑ Tract - ❑ Other ❑ Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. 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' - j . ��Q�0��E:_�� . .. � � ' '. 1 �;aeau+;�ew tss.,, - � 'ss�' � ' "` NE 18T 4 HAIPAINN P N '"`� � FEN�cs's � e cE; M er�e'oe'w t25.so''-'!� � ., ' �.__ .:. .._..; , ' I t � a,r�f �r� i � ' ..::� .��. �: r� -.: .,.�\� -..`. . �� '�II... , , .' . . . . E ' ' SET REBARjt'.fR tS 5a1i ., `,�� : ' . � _ _.- �- � I I ' . 111 . /� �' . . . , .. ... ' � - � : i �� ti;';� r t " % � 3.5•H�� . � � /. : riacEr r�Nct �,;:.: � i. ---�e�-__e ��: � . ._ga.__. �.d:.-. � �� X .r i f � �° � sa o � zo ,o �� 1 �': }f r��. fR-�_�....,�3 I �1*,�� r I �.� . - �rG-� 3 ��L o�F� GoND �n or� ' , Technical Information Report for RVT Short Plat August 8, 2007 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY Included in this section are responses to the 1990 King County Surface Water Design Manual Core and Special Requirements. King County Surface Water Design Manual Core Requirements: The 1990 King County Surface Water Design Manual Core and Special Requirements are being met in the following manner: 1. Dischar�e at the Natural Location The direction of existing runoff follows the terrain slope to the southwest of the property. The flow exits over the south property boundary into adjacent lots where it is eventually picked up by the drainage system in the adjacent plat or flows overland towards Duvall Avenue NE. The flow in Duvall Avenue pipe system is south to Honey Creek. The proposed drainage system collects site drainage and discharges to the same pipe system in the Duval Road right-of-way thereby preserving the existing discharge location. 2. Off-site Analysis An off-site analysis is included in Section 3 of this report. The analysis includes an inspection of the downstream system and research. 3. Flow Control Flow control is not required due to the small scope of the project. A threshold analysis is included in Section 4. Perforated stub-outs are provided for mitigation. 4. Conve. ay nce S. sy tem Conveyance will be provided by buried pipes. All runoff from the� site will be controlled. 5. Temporary Erosion & Sediment Control Temporary erosion & sediment control (TESC) measures ��ill be in place during construction. A TESC plan is included as part of the engineering drawings. 6. Maintenance & Operations ', � maintenance and operations manual is provided in Section 10 of this TIR. �� 7. Financial Guarantees & Liability I The project owner will provide bonding a5 r�quired by the City. Bond amounts ��ill be � determined later in the process. ii Technical Information Report for RVT Short Plat August 8, 2007 King County Surface Water Design Manual Special Requirements: � l. Critical Drainage Areas � A P-suffix conditions search did not identify the site as being in a critical area. 2. Compliance with Existing Master Drainage Plan There is no known existing Master Drainage Plan for the site. The site is under the City of Renton jurisdiction. _� 3. Conditions Requiring a Master Drainage Plan. The site does not trigger this requirement 4. Adopted Basin ar Communitv Plans The site is in an area that is included in the May Creek Basin Plan. The site naturally drains to Honey Creek (Stream #0285) which is a tributary of May Creek. The Basin Plan recommends basin-wide detention and water quality standards, and forest retention for rural areas. Also included in the plan are habitat and drainage improvement projects. The recommendations are not applicable to this project. The proposed development does not trigger a detention or water quality requirement. , S. Special Water Quality Controls I This site does not exceed the threshold that would trigger this requirement. 6. Coalescing Plate Oil/Water Separator This site does not exceed the threshold that �vould trigger this requirement. 7. Closed Depressions This site does not discharge to a closed depression. 8. Use of Lakes. Wetlands or Closed Depressions for Peak Rate Runoff Control Not applicable. , ti._ 9. Delineation of� 100-vear Floodplain ', vot applicahle. " l0 Flood Pro[cction Faeiliti�5 for�I�ti�pe l and 2 Strcams -�� Not applicable. �? �_ Technical Information Report for RVT Short Plat Augasst 8, 2007 11. Geotechnical Analysis and Report Not applicable. � ': 12. Soil Analysis and Report � Not applicable. �, � i__; I r. ' l , < > I� I I '� ' i a i i � ; � i 4 r�� Technical Information Report for RVT Short Plat Auga�st 8, 2007 I SECTION 3 OFF-SITE ANALYSIS �' 4 A Level 1 downstream analysis is included in this section. The site and downstream system were inspected in July of 2007. Drainage System Description Upstream There is no significant quantity of upstream runoff that enters the subject property. The north and east boundaries of the property abut street rights-of-way that have constructed drainage systems � that collect and convey runoff away from the site. NE 18''' Circle has curb, gutter and drainage � inlets, and Duvall Avenue NE has a ditch. The parcel to the south is down-slope of the site. The parcel to the west does have some area that slopes towards the site but the contributing drainage area is small. The pervious area that potentially drains to the property is only a few hundred square , feet. No signs of significant water movement across the property were observed during the site inspection. On-site The existing site contains a building, concrete surfaces, gravel driveway, lawn and some trees. �, Drainage from the hard surfaces discharges to grade. Runoff generated on-site follows the terrain slope and flows to the southwest and over the south property line. There is no constructed drainage system on-site. Downstream Existing drainage exits the property over the south property line. The drainage is either picked up by private drainage systems or flows overland following the topography to the ditch on the west side of Duvall Avenue NE. After development the site runoff will discharge directly to the storm system in Duvall Avenue NE. The drainage in the ditch eventually flows into the same pipe system. The roadside ditch flows south along the west side of Duvall Avenue NE (Photograph #1). The ditch is shallow, vegetated with grass and extends from the site frontage a further 350 feet from the southeast site corner to the south. The ditch is generally about two feet deep but shallows to about one foot in depth just south of SE 107`h Street (Photograph #4). Along this route the ditch is interrupted by four driveway culverts (Photograph#2). All culverts are 12-inches in diameter and are either concrete or double-wall corrugated plastic. The ditch appears to be stable with no signs of significant erosion. The ditch terminates at a 12-inch diameter corrugated metal pipe inlet near the north edge of SE 107`h Place (Photograph #5). South of SE 107`� Place the flow is contained in a buried pipe system that flows south through ia 11 i Tech�ticnl Infonraatio�t Report for RVT Sl:ort Plat Ac�gust 8. 2007 several catchbasins. The pipe size is initially 12-inches in diameter but changes to 24-inches north of NE Sunset Boulevard. The pipe system continues south along the west edge of Duvall Avenue NE and crosses NE Sunset Boulevard. About 275 feet south of Sunset Boulevard the pipe system connects to an approximately 48-inch diameter culvert that conveys Honey Creek east to west below Duvall Avenue NE (Photograph#6). The culvert continues southwest across a multi-store retail development parking lot, then beneath Anacortes Avenue NE, and across a McDonalds parking area to discharge west of the McDonalds (Photograph#7). The flow continues as an open stream to the southwest (Photograph #8) and passes through a large-diameter pipe or arch culvert about 160 feet downstream of the McDonalds (Photograph#9). The culvert is about 50 feet long. The stream continues west sometimes contained inside vertical walled banks (Photograph #10). The stream is of low gradient and appears to be stable with no obvious erosion or flooding problems. At the east edge of an office building on the east side of Whitman Avenue NE the stream enters twin large-diameter corrugated pipes (Photograph #1 1). The flrnv continue� ��est and north��est to an eve�ntual confluence ��ith Mav Creek. Resource Review Se[isitive Area Folios The County SAO folios were reviewed. The site is in an urban area �+�ithuut any sensitive areas either on-site on in the immediate vicinity. The nearest mapped sensitive area is a class 2 wetland (ID # 3706) about 1,300 feet south east of the site. The wetland is on Honey Creek upstream of the confluence with the site draina�e. An SAO compilation map is included in this report. Problem Descriptions No significant drainage problems were found in the do�vnstream system during the inspection. The existing downstream system within a quarter-mile downstream of the site is comprised of ditches, buried pipes and a stream (Honey Creek). 'I'he ditch system in Duvall Avenue NE is shallow and would have a limited capacity. In some places the ditch is about��ne foot deep. There was no evidence to su��est that the pipe system is under-capacit}�. ; Nlitigatio� of Existing or Potential Problems � The proposed system should preferably discharge to a storm main in Duvall Avenue I�E; cilhcr to � the proposed system to be installed by the City or to the existing 18-inch system under the east half �� of the road pavement. The shallow roadside ditch fronting the site is of limited capacity and is the ., less preferable dischar`�e point. i� I � i ' ,e?`� - .. �i: �oi � - • �r - �v � uo. a�� y- ._.. .. ,A`, � mo i� ,.. _`� M z: `. ^! . ,.u• �.. �ia �,�5 �..:,. n� ,,,_ o s. �,,,. ,. _�,. � .... �''" a ' "" ! �I � .a,.. ' rcM7KiN I � i� �� ixa x ��r� n,- Rao v � ..•. �Nf� W I �. 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'*r - -- i i . k'h�,t�� #I 1 �l��in cul��rt� under��'hi[n�an :A��. ly f �._ iMAP �� c,Q,��A Q � ��a � N€aarf+cT `�s-� � � r��r►�cT s ''�'(�"; SE tooTM �� i NE 2fTM ST � SE 1pQTM R � NE Z'�tp PL � � � � � � � � �� ' � G� � �aa+o a � � � �"� o ' �'F �� ,�ftr'� , ,. �2� �Cr ME�VD R L' , � � ��yp� �) � � NE21�� i� � � ��,� i � � ��srsT r � Ne�r„cr � � �[ !i < i r+��urM a � � a ��j�„� NE 2�TM ST � IV6 f91'M gT � -• � �_.. � � � ,' � �rgfH� I � �� { � � y� �t` "E�sn'sr � �0'2 �,ernsr � '�. �� ti i � �tan,c� F � � H ' �' ��arN sr y �,�'`�� r�+an+r� � wE`e� °i Ne'�"c� � SE 107TN � � z Renton � j��, "�� ,�n,sr sE,an-F,r� ` �L_l Z � � Y~-- � Z �', , __�--�--. . i �� >��f��_ �Ftir�'J � �NFS :'- DI_ - `� �� _ `` ��G : - � •�, 4S' � �'�s� ' - ° _- - � l.�. .;��t'�,�a � r`�,,�a ? � ; � r �`, . ' '� �. -�� - � `` t:,``' �� _ �--.� ___�� ? � �----- � -N t_-•r r H s r _ :.,�,� � _.' r�r1rN sr .. sE»�sr ._ ,5 �t HF»TMR ..� � �. � �. NE 1 tTM CT NE 11TM g'i' � � � � 11E 1�CT NE 1 iTM ST 2 � Cr'�' � _ � � � 72 � = NE h711 ST 1�1 � M � F r � � � � _ �� f/E iQT N PL m ' � � � NE to�sT S�t ie7-►+sr = {CI�5 Kmg County � T�B� The informauon induded on this map has been compiled by King County staB from a variety of sources and is subject to change without notice.King County makes no representations or wartanties,e�ress or implied,as to accuracy,completeness,timeiiness,or nghts to the use of such intormation. This documern is not intendetl for use as a survey product King Counry shall not b?liable for any general,special,indirect,incidental.or consequential a � . damages including,but not limited to.lost revenues or lost profits resulhng from lhe use or misuse ot th=informat�on contained on this map.Any sala of King County this map or information on[his map is prohibited except by written pertnission of King County. Date�.&'1012007 Source:King County iMAP-SensiUve Areas(http:/lvrvnv.melrokc.gov/GISIiMAP) iMAP Le ge nd � FNghlighted Feat�e �,,;�` �� SAO Erasion r ' �_I ��tY ��ry . , un�f;sd � Ghirwak Distributian ' x MaurMtain Peaka � Lakes arxf la�ge Rivers �9�aYs Streams � Incurporatsd Area ��, Flaodway 5tree� � 100 Year Flaalplain H;�.,,� Ghannel h�gratian Hazard �� Area� I � NOOERATE Parcels Sf1lE11E SAO Stream � SA�O YMetland � Clas 1 ' f: $AO La nds I ide �/ c��A.�.�.,� , ` � SAO Caa l A�i rre �/ c��s�„�.�:a (cant� � $�5eismic i 'I t � (_ � t I lir I ! 1 ti �, The information included on this map has been compiled hy King County slaft from a vanety of sources and is subject to change without notice.King CounTy makes no represeMations or warrenties.express or implied,as to accuracy,complet=ness,timeliness,or rights to the use ot such iniormation. Th�s tlocument is not in[ended for use as a survey product.King Counry shall r.ot be liabie for any general,special,indirect,incidenlal,or consequential a damages induding,but not limi[ed to,lost revenues or lost profits resulting from th=use or misuse oi the information contained on this map.Any sale of King County this map or information on ihis map is prohibited=xcept by written p=rmission of King County. Date:8110/2007 Source:King County iMAP-Sensitive Areas(http2�www.metrokc.godGlSlMAPj Technical Information Report for RVT Short Plat August 8, 2007 SECTION 4 FLOW CONTROL & WATER QUALITY ANALYSIS AND DESIGN The project is exempt from providing detention due to a negligible peak runoff rate increase as defined in Section 1.2.3 Core Requirement #3 of the 1990 KCSWDM. The proposed project site post-development peak runoff rate for the 100year, 24-hour duration design storm event is calculated to be less than 0.5 cfs more than the pre-development peak runoff rate. The calculations are summarized below. Water quality treatment facilities are unlikely to be required. The total impervious area subject to traffic will be about 1,000 square feet per lot or 3,000 square feet total. This is the estimated area of the driveways. Existing Site Hydrology The existing land cover for the property consists 2,869 square feet of impervious area and 14,047 of urban landscaping. Soil is Alderwood sandy, gravelly loam per the NRCS mapping. Time of concentration for hydrological modeling assumes 130 feet of sheet flow over lawn (159 minutes); impervious flow time is assumed at 2 minutes. Developed Site Hydrology The developed site consists of impen-ious areas and landscaping. The quantity of new impervious area will be limited by the maximum structural coverage allowed by zoning (2,500 square feet per lot). The quantity of impervious surface assumed for this analysis is 60 percent of the site for R-8 density extrapolated form Table 3.5.2B of the 1990 KCSWDM. Basin Areas and Runoff Rates Area breakdowns for the existing and developed condition are tabulated below. '� Cover Type Existing Condition Developed Condition II Area Area I (acres) (acres) I Impervious 0.07 0.23 Landscaping 0.32 0.16 Total 0.39 0.39 i� - � Technical Information Report for RVT Short Plat August 8, 2007 �- � The 24-hour/100-year precipitation from County isopluvials is 3.95 inches. 100-year runoff rates are summarized below. Return Period Existing Condition Developed Condition Flow� Flow (cubic feet per second) (cubic feet per second) 100-year 0.24 0.38 The change in runoff rate for the 100-year, 24-hour storm is calculated at 0.14 cfs which is less than the 0.5 cfs threshold. �r� s� r'E �6 � � b &�' (D. 39�c) I,►�nErtvr�vs 2�?6°I �SF CO• D7�) � � ; - �, . i------ ----*:� G'' � ii o -in' i �• i C�� ,\� � �i �.�0' ��,#�' � �r i( ��0 G � ��. � 5 � r! � �� + ' u C � Q � �� x q,�� / o � � ti, i: ,.��• � �`�� e � � �S'V � vt` /•7 / � d; f � ' {/ 1�t � v� �`�� n, ,: I � `\tp`'�+��Sp, � � '(�aa..,�°� i 'i� � � o r� 4: �1� G�� : 1 i' I � : i 1��C . 5� CO FEN•..�� SDM. PIA + 4 .�1 f { : � � �',"' � � S IE . - 115. i � r . 1 i ' �I`1' �. . - __.__ '.. ' �c\•1"E - IT�FtAE. T: �E4SURF� �f � 11 ! � � r ,... .... � i � ' t2o ' ..... .. ... �, i.Ai � � ..._. _ _ .. ._. ., . .. � . 4v� 6 tf '. s. — _— f�( ! i �: , , � . 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'�I�i�.iJf)II (�.�.1'illf'. � . 5f-�.f2$C)llR I N Meters li A 0 50 100 200 300 Feet 0 300 600 1,200 1,800 �� Natural Resources Web Soil Survey 2.0 8/8/2007 I�I % Conservation Service National Cooperative Soil Survey Page 1 of 3 � � Soil Map—King County Area,Washington (RVT Short Plat) MAP LEGEND MAP INFORMATION , Area of Interest(AOI) (� Very Stony Spot Original soil survey map sheets were prepared at publication scale. Area ot Interest(Aol) Viewing scale and printing scale,however,may vary from the ,� Wet Spot original.Please rely on the bar scale on each map sheet for proper soils ma measurements. � Other p Soil Map Units Special Line Features Source of Map: Natural Resources Conservation Service Special Point Features - Gully Web Soil Survey URL: http://websoilsurvey.nres.usda.gov � Blowout Coordinate System: UTM Zone 10N , . Shorl Steep Slope � eorrow Pi� � This product is generated from the USDA-NRCS certified data as of �. Other the version date(s)listed below. X Clay Spot Poiiticai Features Soil Survey Area: King County Area,Washington � Closed Depression Municipalities Survey Area Data: Version 4, Nov 21,2006 x Gravei Pit � Cities Date(s)aerial images were photographed: 7/10/1990;7/18/1990 ., Gravelly Spot � Urban Areas The orthophoto or other base map on which the soil lines were � Landfin Water Features compiled and digitized probably differs from the background A Lava Flow � Oceans imagery displayed on these maps.As a result, some minor shifting of map unit boundaries may be evident. ,�, Marsh i..� Streams and Canals � Mine or Quarry Trensportation � Rails po Miscellaneous Water Roads p Perennial Water N Interstate Highways � Rock Outcrop N US Routes t Saline Spot State Highways , . Sandy Spol N Local Roads z Severely Eroded Spot Other Roads � Sinkhole � Slide or Slip � Sodic Spot I � Spoil Area I Q Stony Spot I �= Natural Resources Web Soil Survey 2.0 8/8/2007 Conservation Service National Cooperative Soil Survey Page 2 of 3 Soil Map-King Co�nty Area. Washington RVT Short Plat Map Unit Legend King County Area,Washington(WA633) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 73.8 55.8% 6 to 15 percent slopes EvC Everett gravelly sandy loam,5 51.1 38.6% �� to 15 percent slopes �� ',RdC Ragnar-Indianola association, ! 0.0 0.0% sloping Sm I Shalcar muck �, 7.3 5.5% Totals for Area of Interest(AOI) 132.3 I 100.0% USDA Natural Resources Web Soil Survey 2.0 8/8/2007 � Conservation Service National Cooperative Soil Survey Page 3 of 3 EX Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /Loss EX 0.24 8.00 0.0884 0.39 SBUHrSCS kc24hr 100 yr Drainage Area: EX Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur 24.00 hrs Area CN TC Pervious 0.3200 ac 86.00 0.27 hrs Impervious 0.0700 ac 98.00 0.03 hrs Total 0.3900 ac Supporting Data: Pervious CN Data: Landscaping 86.00 0.3200 ac Impervious CN Data: Impervious 98.00 0.0700 ac Pervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Sheet Landscaping 130.00 ft 1.70% 0.1500 15.92 min Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Impervious 0.00 ft 0.00% 2.0000 2.00 min DV Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /�oss DV 0.38 7.83 0.1a46 0.39 SBUH,SCS kc24hr 100 yr Drainage Area: DV Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur 24.00 hrs Area CN TC Pervious 0.1600 ac 86.00 0.08 hrs Impervious 0.2300 ac 98.00 0.03 hrs Total 0.3900 ac Supporting Data: Pervious CN Data: Landscaping 86.00 0.1600 ac Impervious CN Data: Impervious 98.00 0.2300 ac Penrious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Landscaping 0.00 ft 0.00% 5.0000 5.00 min Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed None Entered 0.00 ft 0.00% 2.0000 2.00 min Technical Informcrtion Repor-t for RVT Short Plat A�egc�st 8, 2007 SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN Conveyance will be by 6-inch diameter pipe. The capacity of a 6-inch diameter pipe laid at a slope of 2 percent is 0.79 cfs. From Section 4 the 100-year flow from the developed site is 0.38 cfs. Therefore the pipe system should have more than adequate capacity for the expected flows. � z; I 6-INCH PIPE AT 2% SLOPE ', Worksheet for Circular Channel 'I Project Description Project File c:lnbelprojects120071jmtb-a701\stormlpipe.fm2 Worksheet pipe Flow Element Circular Channel i Method Manning's Formula Solve For Discharge Input Data Mannings Coefficient 0.013 Channel Slope 0.020000 fUft Depth 0.50 ft Diameter 6.00 in Results Discharge 0.79 cfs Flow Area 0.20 ftz Wetted Perimeter 1.57 ft Top Width 0.15e-7 ft Critical Depth 0.44 ft Percent Full 100.00 � Critical Slope 0.017869 fUft Velocity 4.04 ft/s Velocity Head 0.25 ft Specific Energy 0.75 ft Froude Number 0.2e-3 Maximum Discharge 0.85 cfs Full Flow Capacity 0.79 cfs Full Flow Slope 0.020000 fUft Flow is subcritical. Ij i j i ( I `�l ,.i i�� , I i� �' O8/16/07 FlowMaster v5.13 02:14:41 PM Haestad Methods, Inc. 37 Brookside Road Waterbury,CT 06708 (203)755-1666 Page 1 of 1 � Tec:hniccrl lrifor-�natron Report for RVT Short Plcrt At�gctst 8, ?007 � SECTION 6 SPECIAL REPORTS AND STUDIES There are no special reports or studies. �} Technical Information Report for RVT Short Plat August 8, 2007 SECTION 7 OTHER PERMITS No state permits are anticipated to be required. City permits will include site development, right-of-way use and utility connection permits. A grading permit may be required depending on the quantity of earthwork. Site grades are expected to be maintained with no substantial cut or fill. ,, � ; I ,� � Te��hnicul Ittforirtutior2 ReE�urt for RVT Sltort Plat Att�ust 8, 21107 i SECTION S ESC ANALYSIS AND DESIGN II! A Tem orar r Erosion and Sedimentation Control TESC lan ��ill be re ared as art of the I p } ( ) P P P P , permit and construction drawings. The TESC BMPs are anticipated to include: '� • Clearing Limits. Clearly defined limits will limit disturbed area and hence limit the source of �� sediment. • Silt Barrier Fence. Placed at the down-slope limits of construction the silt fence will provide �� silt retention far the disturbed areas. • Construction Entrance. A construction entrance will be provided at the entrance to the construction site to remove wheel-tracked soil. • Covering Practices. This will limit the area available to erode. Straw mulch or plastic sheeting will be placed over exposed soil that remains unworked for more than seven days in the dry season or two days in the wet season. • Revegetation. Disturbed areas that are not covered with impervious surface will be hydroseeded towards the end of construction to provide permanent stabilization. • Catchbasin inserts. Inserts will be placed in existing and new catchbasin inlets in the right-of-way to prevent sediment form entering the existing storm system. ,6 � Teclinical Information Report for RVT Short Plat Acsgust 8, 2007 � � � SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT A Retention/Detention Facility Summary Sheet is not applicable. Bond quantities will be developed during engineering plan stage. '� _� Technical Information Report for RVT Slzort Plat Accgust 8, 2007 SECTION 10 OPERATIONS AND MAINTENANCE MANUAL No large scale facilities are proposed. The system will consist of only buried pipe and maybe catchbasins. A preliminary maintenance schedule extracted from the County Manual is included in this section. ,,� Technical Information Report for RVT Short Plat August 8, 2007 , NO. 5- CATCH BASINS Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed �, General Trash&Debris Trash or debris of more than 1 i2 cubic foot which is No Trash or debris located (Includes Sediment) located immediately in front of the catch basin immediately in front of catch opening or is blocking capacity of the basin by more basin opening. 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 lowest basin. pipe into or out of the basin. Trash or debris in any inlet or outlet pipe blocking Inlet and outlet pipes free of trash more than 1/3 of its height. or 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 volume would 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 Slab curb face into the street(If applicable). Top slab has holes larger than 2 square inches or Top slab is free of holes and cracks wider than 1/4 inch(intent is to make sure all cracks. material is running into basin). Frame not sitting flush on top slab,i.e.,separation of Frame is sitting flush on top slab. more than 3/4 inch of the frame from the top slab. Cracks in Basin Walls/ Cracks wider than 1/2 inch and longer than 3 feet, Basin replaced or repaired to Bottom any evidence of soil particles entering catch basin design standards. through cracks,or maintenance person judges that structure is unsound. Cracks wider than 1/2 inch and longer than 1 foot at No cracks more than 1/4 inch the joint of any inleV outlet pipe or any evidence of wide at the joint of inleVoutlet soil particles entering catch basin through cradcs. pipe. SedimenU Basin has settled more than 1 inch or has rotated Basin replaced or repaired to Misalignment more than 2 inches out of alignment. design standards. � 29 T<�c�lr�ur�ul I�zfc�rin�urnn /Zrp��rt jur Rl�'l�S'/�nr! Plru ,1 u�t�ct�Y. ZOi)' NO. 5- CATCH BASINS (CONTINUED9 i Maintenance Defect Conditions When Maintenance is Needed Results Expected When � Component Maintenance is performed � Fire Hazard Presence of chemicals such as natural gas,oil and No flammable chemicals gasoline. present. Vegetation Vegetation growing across and blocking more than No vegetation blocking opening 10%of the basin opening. to basin. Vegetation growing in intetroutlet pipe joints that is No vegetation or root growth more than six inches tall and less ihan six inches apar�. present. Pollution Nonflammable chemicals of more than 1;2 cubic foot No pollution present other than , per three feet of basin length. surface film. I Catch Basin Cover Cover Not in Place Cover is missing or only partially in place.Any open Catch basin cover is closed catch basin requires maintenance. ' � Locking Mechanism Mechanism cannot be opened by on maintenance Mechanism opens with proper Not Working person with proper tools.Bolts into frame have less tools. than 1�'2 inch of thread. Cover Difficult to One maintenance person cannot remove lid after Cover can be removed by one Remove applying 80 Ibs.of lift;intent is keep cover from sealing maintenance person. off access to maintenance. Ladder Ladder Rungs Ladder is unsafe due to missing rungs,misalignment, Ladder meets design standards Unsafe rust,cracks,or sharp edges. and allows maintenance person safe access. Metal Grates (If Grate with opening wider than 7i8 inch. Grate opening meets design Applicable) standards. Trash and Debris Trash and debris that is blocking more than 20%of Grate free of trash and debris. grate surface. Damaged or Missing. Grate missing or broken member(s)of ihe grate. Grate is in place and meets design standards. �0 Technical Information Report for RVT Short Plat August 8, 2007 NO. 10- CONVEYANCE SYSTEMS (PIPES& DITCHES) Maintenance Defect 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 of Pipe repaired or replaced. 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 sediment that exceeds 20%of the Ditch cleanedi 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 through ditches. ditches. Erosion Damage to See"Ponds"Standard No. 1 See"Ponds"Standard No. 1 Slopes Rock Lining Out of Place Maintenance person can see native soil beneath Replace rocks to design or Missing(If the rock lining. standards. Applicable). Catch Basins See"Catch Basins:Standard No.5 See"Catch Basins"Standard No.5 Debris Barriers See"Debris Barriers"Standard No.6 See"Debris Barriers"Standard (e.g.,Trash Rack) No.6 3l � III� J