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Grant Avenue Townhomes Renton, Washington Technical Information Report November 16, 2015 Pacific Engineering Job No. 15022 TECHNICAL INFORMATION REPORT FOR Grant Avenue Townhomes RENTON, WASHINGTON November 16, 2015 PREPARED FOR Satwant Singh, Skyline Properties, Inc. 50 116th Avenue SE, Suite 120 Bellevue, WA 98004 Phone: (425) 455-2065 E-mail: pmvrsingh@gmail.com PREPARED BY Pacific Engineering Design, LLC. 15445 53rd Avenue S Seattle, WA 98188 Phone: (206) 431-7970 TABLE OF CONTENTS I. PROJECT OVERVIEW ............................................................................................... 3 Figure 1 Technical Information Worksheet to Follow .................................................. .4 Figure 2 Site Location Map to Follow ........................................................................... 5 Figure 3 Drainage Basin, Subbasin and Site Characteristics ....................................... 6 Figure 4 Soils ............................................................................................................... 7 II. CONDITIONS AND REQUIREMENTS SUMMARy .................................................... 8 III. OFF SITE ANALySiS ............................................................................................... 15 Task 1 Study Area Definition and Maps ..................................................................... 16 Task 2 Resource Review ........................................................................................... 17 Task 3 Field Inspection .............................................................................................. 18 Task 4 Drainage System Description and Potential Problems ................................... 19 Task 5 Mitigation of Existing or Potential Problems ................................................... 19 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ... 20 Part A Existing Site Hydrology ................................................................................... 21 Part B Developed Site Hydrology ............................................................................... 22 Part C Performance Standards .................................................................................. 26 Part D Flow Control System ....................................................................................... 26 Part E Water Quality System ..................................................................................... 34 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN (REVISED 6/26/2012) ............ 37 VI. SPECIAL REPORTS AND STUDIES ....................................................................... 38 VII. OTHER PERMITS ................................................................................................... 39 VIII. CSWPPP ANALYSIS AND DESIGN ...................................................................... 40 IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT ................................................................................................................... 42 X. OPERATIONS AND MAINTENANCE MANUAL ....................................................... 43 2 I. Project Overview The proposed project will develop 8 multi-family buildings (total 36 units) in parcel 202305-9052. The site is located two parcels north of the northeast corner of the intersection of South 18th Street and Grant Avenue South. The address of the site is 1600 Grant Avenue South. The site area is 2.11 acres. The site is a trapezoidal property that is approximately 583' x 158' (average) with frontage on its western short side along Grant Avenue South. The project site includes onsite development area and offsite improvement area along the Grant Avenue South frontage. Total project site area is approximately 2.17 acres. The site is located in the City of Renton Residential Multi- Family (RM-F) zone. The site is surrounded by single-family residents to the east and multi-family residences to the west and south and a Puget Sound Power and Light Company property to the north. The site is located in the Thunder Hills Creek drainage sub-basin of the Black River Drainage basin. The site is located in the Duration with Forested conditions flow control area (Level 2 flow control with Forest conditions as existing condition) and Enhanced Basic water quality control is required because the proposed development is a multi-family development. There is a single family house (built 1946) on the west portion of the site near the Grant Avenue South. The house will be demolished and removed for the proposed development. The remainder of the property is covered with grass with some scattered trees. The site is hilly with average slope of 11 % slopes westerly toward Grant Avenue South. There is no sensitive area on the site and no difficult conditions for the proposed development. For the on site improvement, a combined detention/wet vault is used to provide the required Level 2 flow control and a treatment train of wet vault and Storm Filter manhole with CSF cartridges is used to provide the required Enhanced Basic water quality treatment. The offsite frontage improvement creates approximately 1,200 square feet of new impervious area (480 square feet of it is pollution generating impervious area) and no new pervious area. For flow control, the new impervious area created by the offsite improvement is counted as bypassed target area Per KCSWDM Section 1.2.3.2.E. The onsite detention vault is oversized, so that the developed onsite detained runoff plus the offsite bypassed runoff meets the required Level 2 flow control requirements at the point of convergence (SDMH#1 at Grant Avenue South). For water quality treatment, new pollution generating area is only 480 square feet and is counted as untreated discharge per KCSWDM Section 1.2.8.2.0. Flow control and water quality treatment are not required for the offsite improvement. 3 Figure 1 Technical Information Worksheet to Follow 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project OwnerSkyl ine Properties, Inc. ,Phone (425) 455-2065 I Address 50 116th Ave. SE., #120 Bellevue, WA 98004 Project EnglneerJingsong Feng, P. E. CompanyPacific Engr. Design, LLC. Phone (206) 431-7970 Part 3 TYPE OF PERMIT APPLICATION o Landuse Services Subdivison I Short Subd. I UPD ~ Building Services ~ Commerical I SFR ~ Clearing and Grading ~ Right-of-Way Use o Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review ~ Targeted (circle): arge Site Date (include revision dates): Date of Final: Part 6 ADJUSTMENT APPROVALS I Part 2 PROJECT LOCATION AND DESCRIPTION Project Name Grant Avenue Townhomes DOES Permit # _________ _ Location Township _2_3 ____ _ Range _-=5'--___ _ Section __ 2_0 ____ _ Site Address 1600 Grant Ave. S. Renton, WA 98055 Part 4 OTHER REVIEWS AND PERMITS, o DFWHPA o COE404 o DOE Dam Safety o FEMA Floodplain o COE Wetlands o Other o Shoreline Management ~trugJuraL ~ o ESA Section 7 Site Improvement Plan (Engr. Plans) Type (circle one): ~ Modified I Small Site Date (include revision dates): Date of Final: Type (circle one): Standard 1 Complex 1 Preapplication 1 Experimental 1 Blanket Description: (include conditions in TIR Section 2) Date of A[l]Jroval: 2009 Surface Water Design Manual 1 11912009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: (iiiJ/No Describe: Start Date: Completion Date: Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: -'S'70"-o:..:..s---"c"'r..:.e..:e.:ck'--______ _ Special District Overlays: ______________________ _ Drainage Basin: Thunder Hills Creek sUb-basin of Black River Drainage basin. Stormwater Requirements: DJ!ration wi th Forest Condit i on Flow Control Enhanced BaS1C Water Qua11ty Treatment. Part 9 ON SITE AND ADJACENT SENSITIVE AREAS ~ River/Stream Thunder Hills Creek o Steep Slope ________ _ o Lake o Wetlands _________ _ ~ Erosion Hazard _--, _____ _ ~ Landslide Hazard Moderate o Closed Depression _______ _ o Coal Mine Hazard ______ _ o Floodplain __________ _ o Seismic Hazard _______ _ o Other __________ _ o Habitat Protection ______ _ 0 ________ _ Part 10 SOILS Soil Type Slopes Erosion Potential AgC 8% to 15% Moderate AgD 15% to 30% Severe o High Groundwater Table (within 5 feet) o Sole Source Aquifer o Other o Seeps/Springs o Additional Sheets Attached 2009 Surface Water Design Manual 2 1/9/2009 I I KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE a Core 2 -Offsite Analysis o Sensitive/Critical Areas a SEPA o Other LIMITATION / SITE CONSTRAINT Duration with forest condition Flow control and Enhanced Basic Water quality treatment. 0 _________ _ o Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: Storm drainage system at Grant Avenue South jname or description) Core Requirements (ali 8 apply) Dischame at Natural Location Number of Natural DischarQe Locations: 1 at SDMH#l Offsite Analysis Level: CD/2 / 3 dated: Flow Control Level: 1 K%}/ 3 or Exemption Number (incl. facility summary sheet) Small Site BMPs Perforated connections Conveyance System Spill containment located at: c;omolnea aetentlon/wet vault & StormFilter manhole Erosion and Sediment Control ESC Site Supervisor: Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private /(public) If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: ~/No Liability Water Quality Type: Basic / Sens. Lake <l. Enhanced Basicl!1Y Bog (include facility summary sheet) or Exemption No. Landscape Management Plan: (Y;;) No Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared Fac. /~ Requirements Name: ----- Floodplain/Floodway Delineation Type: Major / Minor / Exemption / <tIone) 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/A Source Control Describe landuse: Multi-Family (comm.lindustriallanduse) Describe any structural controls: 2009 Surface Water Design Manual 11912009 3 , , , , , KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes /~ Treatment BMP: Maintenance Agreement: Yes /@ with whom? Other Drainage Structures Describe: Combined detention/wet vault StormFilter manhole with CSF cartridges. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION tID Clearing Limits tID Stabilize Exposed Surfaces tID Cover Measures tID Remove and Restore Temporary ESC Facilities !ill Perimeter Protection E] Clean and Remove All Silt and Debris, Ensure tID Traffic Area Stabilization Operation of Permanent Facilities tID Sediment Retention ~ Flag Limits of SAO and open space ~ Surface Water Collection preservation areas o Other {ID Dewatering Control ~ Dust Control {ID Flow Control Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description ~ Detention Comb. detentior./ o Biofiltration wet vault Comb. detention/ o Infiltration {ID Wetpool wet vault StormFilter MH o Regional Facility tID Media Filtration w/CSF cartridges o Shared Facility o Oil Control 18.1 Flow Control Perforated o Spill Control connections BMPs tl ~ 0 Flow Control BMPs preserve ex. ee o Other o Other 2009 Surface Water Design Manual 11912009 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTSITRACTS Part 16 STRUCTURAL ANALYSIS E3 Drainage Easement ~ Cast in Place Vault : 0 Covenant I2:SI Retaining Wall o Native Growth Protection Covenant E3 Rockery> 4' High o Tract o Structural on Steep Slope o Other o Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site, Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Oat. 2009 Surface Water Design Manual 1/912009 5 · Figure 2 Site Location Map to Follow 5 Figure 3 Drainage Basin, Subbasin and Site Characteristics 6 ~"aj:J soos '=J ~fIaJ;)~ewD JO/I'l::jJE!P'I:)ia....01D /SaM uojlju,,<seM "'IVl D I&'3 uolllul\jSeM ~El 0 45,wenaD "'I\!l:!~""IB~ sam'~ 600Z/9~/O~ pajU!Jd Ueld all!sualjeJdwo::> iI.l!mn JalE!M aaE!pns ---.,..>- N V King County iMap ---'!II The nlarmation inckJdcd on this map has been ccmpicd by King Coonly stalffrom a vanety 01 sou r ces and,s sublect to charY;je v.ithou t notice_ King COlllly makes no re~ese nlatlons or walTa nUes, express or Implied. as to &Xu rdCY. completeness. t mcincss, or rghts to !he use 01 such Information . Tlls document IS not mtended for use as a SlrVL'Y product. King County shall no; be iaOle for any general, Special, ndirecL IncidenLa l , or consequential damages including. but no! Irrllled to, lost revenu es or bst profits lesuling from the usc or mISuse oI1ho ,n!ormallOn contained Ofllhs map. Ally sale 01 tI1ismap oflnlormatioflonthis map is prohblted except by written permssion 01 KlfIg County. Dale: 10/5/2015 Noles: N A tQ King County GIS CENTER Figure 4 Soils 7 47" 27'S9'"N 47" 2753"N • b N ~ • b ~ ""300 ""DO """" ""390 Map Scale: 1: 1,500 If j:mI:e.d en A ~ {11 H x BS'} s/"eet Soil Map-King Coun ty Area, Washington 560<20 560<SO 56O<8J ~ N O~----~2~O~~~~~----------~OO~~~~~~==CI~· O~---50~~~I OO~------~200~~~~~~3~ A Map projedXln: web Mertato' Corner a:x:roinates: WGS84 Edge tics: l.I1'M Zcne lON WGS84 US DA Natural Resources -Con servation Service Web Soil Survey National Cooperative Soil Survey S60S10 56OS4O 56ffi7O SOO6OO • ~ ~ • , 11 ~ ~ ~ :. ~ ~ R ~ If ~ 11 /16/2015 Page 1 of 3 47'" 2759"N 47" 27S)"N Soil Map----King County Area, Washington MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils 0 Soil Map Unit polygons -Soil Map Unit lines II Soil Map Unit Points Special Point Features ~ Blowout tl51 Borrow Pit llJ: Clay Spot 0 Closed Depression ;X; Gravel Pit ., Gravelly Spot 0 Landfill A Lava Flow 4-Marsh or swamp 'll;' Mine or Quarry @ Miscellaneous Water © Perennial Water V Rock Outcrop + Saline Spot . -. Sandy Spot § Severely Eroded Spot {} Sinkhole i~ Slide or Slip fi! Sodic Spot USDA Natural Resources :iiliiiiiiiiI Conservation Service § Spoil Area (j Stony Spot /AI Very Stony Spot '\? Wet Spot [:) Other ,-Special line Features Water Features Streams and Canals Transportation +++ Rails ..... ,-~ Interstate Highways US Routes Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil SUivey The soil surveys that comprise your AOI were mapped at 1 :24,000. i Waming: Soil Map may not be valid at this scal~:-"-" -_._ .. - I Enlargement of maps beyond the scale of mapping can cause !I misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Survey Area Data: King County Area, Washington Version 11, Sep 14, 2015 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Aug 31, 2013-0ct 6, 2013 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 11/16/2015 Page 2 of3 .Soil Map-King County Area, Washington Map Unit Legend King County Area, Washington (WA633) Map Unit Symbol I Map Unit Name I Acres inAOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes '. ! AgO ' Alderwood gravelly sandy loam, ' I ~ to 30 pereent slopes Totals for Area of Interest ·r·~~_ USDA Natural Resources ~ Conservation Service Web Soil SUlVey National Cooperative Soil SUlvey I 1.2 1.1 2.3 Pereent of AOI 53.9% 46.1% 100.0% ---•.. ~-- 1111612015 Page 3 013 II. Conditions and Requirements Summary CORE REQUIREMENTS -SECTION 1.2 OF KCSWDM 1.2.1 CORE REQUIREMENT #1: Discharge at the Natural Location Under existing condition, the site sheet flows westerly to Grant Avenue South. The low point of Grant Avenue South is located near the northwest corner of the site where there are two type 1 catch basins at both sides of the street to collect street runoff. The street drainage system drains to a storm manhole (SDMH#1) near the northwest corner of the site. SDMH#1 has an 18" outfall pipe that discharges westerly to Thunder Hills Creek. Under developed condition, same drainage pattern will remain. The outfall of the onsite storm system will be connected to SDMH#1 , other than that, the offsite storm system will remain unchanged. 1.2.2 CORE REQUIREMENT #2: Off-site Analysis This core requirement has been addressed in Section III of this report. 1.2.3. CORE REQUIREMENT #3: Flow Control Per SWDM section 1.2.3.3 and 5.2, Flow Control BMPs are required for the onsite development. Since the 2.11 acres lot is larger than 22,000 square feet and impervious area coverage of the site is approximately 66% which is larger than 45%, the large lot high impervious BMP requirements are applied. The feasibility and applicability of full dispersion is studied first, the study found full dispersion is not suitable for this site to fully disperse the new impervious areas and new non-native pervious areas because long native flow path is not available due to the high impervious area ratio. Full infiltration is also not suitable for this site because onsite soil is till soil (Alderwood gravelly sandy loam, 6 to 15% slopes, AgC and 15% to 25% slopes, AgD) according to City of Renton Soils Map. Even though not counting towards flow control credit, the following flow control BMPs are used: 1. Reserve existing trees (11 trees, total 170 caliper inches, 10,112 square feet dripline areas). 2. Perforated tie lines for downspout connections. Onsite flow control is provided by a combined detention/wet vault to provide the required Level 2 flow control (using forest condition as existing condition). 1.2.4 CORE REQUIREMENT #4: Conveyance System The new conveyance piping will be installed as needed. The new conveyance piping has been checked to confirm compliance with chapter 4 of the 2009 KCSWDM. Per KCSWDM Section 1.2.4.1: 8 1. New pipe system shall be designed with sufficient capacity to convey and contain (at the minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. 2. Pipe system structures may overtop for runoff that exceed the 25-year design capacity, provided the overflow from a 1 ~O-year runoff event does not create or aggravate a severe flooding problem or severe erosion problem as described in Core Requirement #2. Any overflow occurring onsite for runoff events up to and including the 1 DO-year event must discharge at the natural location for the project site. In residential subdivision, this overflow must be contained within an onsite drainage easement, tract, covenant, or public right-of-way. 3. The upstream end of a pipe system that receives runoff from an open drainage feature (pond, ditch, etc.) shall be analyzed as a culvert. The properties east and south of the site have their own drainage system to intercept runoff before it reach the site. The property north of the site slopes westerly to Grant Avenue South parallel with the site. The properties west of the site are located at elevations lower than the site. The site does not receive significant upstream runoff from adjacent properties. The new conveyance system is designed to convey and contain the 100 year peak flow and thus meets the requirements listed above. KCBW is used for Back water analysis following the requirements of KCSWDM 4.2.1.2 and designed for the 100 year peak flow. 1.2.5 CORE REQUIREMENT #5: Erosion and Sediment Control Erosion control will be installed as necessary for the frontage improvements and the on- site improvement. 1.2.6 CORE REQUIREMENT #6: Maintenance and Operations Any necessary maintenance of the onsite drainage system will be the responsibility of the property owner and manager. The on-site detention and water quality treatment systems will be maintained by the City of Renton. 1.2.7 CORE REQUIREMENT#7: Bonds and Liability Necessary bonds will be provided at the time the building permit plans are approved and the construction started. 1.2.8 CORE REQUIREMENT #8: Water Quality A treatment train of combined detention/wet vault and StormFilter manhole with CSF cartridges is used to provide the required Enhanced Basic treatment for the onsite development. Water quality treatment is not required for the offsite frontage improvement as mentioned in section 1 of this report. 9 SPECIAL REQUIREMENTS -SECTION 1.3 OF KCSWDM 1.3.1 Special Requirement #1: Other Adopted Area Specific Requirements No other area specific requirements are applicable. The site is not within a CDA, MDP, BP, SCP, SWCP, LMP, FHRPU or SFDP. 1.3.2 Special Requirement #2: Flood Plain I Floodway Delineation Not applicable to this site. There is no flood hazard area in the site. The site is not within a floodplain or floodway. The site is not subject to inundation by the base flood or channel migration. 1.3.3 Special Requirement #3: Flood Protection Facilities Not applicable to this site. There is no flood hazard area in the site. The site does not rely on any flood protection measures. 1.3.4 Special Requirement #4: Source Controls The site is subject to water quality source control. Dumpsters and recycle bins will be stored inside the garages of each units. 1.3.5 Special Requirement #5: Oil Control The estimated ADT of the developed site is approximately 290. The threshold for high- use site is ADT of 100 or more vehicles per 1,000 square feet of gross building area. Gross building area of the site is approximately 39,806 square feet. The threshold for high-use site is ADT of 3981 vehicles. Thus, ADT of the site will be less than the threshold ADT. Oil control is not required. The flow control riser tees with orifices in the flow control structures and the Storm Filter manhole will provide enough treatment for oil control, no extra treatment is required. 14 III. Off Site Analysis 15 Task 1 Study Area Definition and Maps The site is located on the east side of Grant Avenue South, two parcels north of South 18 th Street. The address of the site is 1600 Grant Avenue South. The parcel number of the site is 202305-9052. The site area is 2.11 acres. The project site includes onsite area and offsite frontage improvement area. The project site area is 2.17 acres. The site is located in the Thunder Hills Creek drainage subbasin of the Black River Drainage Basin. See attached Site Map and Topographical Map. 16 Task 2 Resource Review The following resources have been reviewed for existing Ipotential problems in the study area. 1) Adopted Basin Plans Exhibit C, City of Renton Shoreline Master Program Update Restoration Plan, prepared by City of Renton, dated March, 2010 http://www.ecy.wa.gov/programs/sea/shorelines/smp/mycomments/Renton/restoration plan.pdf 2) Finalized Drainage studies None. 3) Basin Reconnaissance Summary Reports and 1"=400' scale problem summary maps City of Renton Shoreline Master Program, Final Shoreline Inventory and Analysis, prepared by City of Renton, dated March, 2010 http://rentonwa.gov/uploadedFiles/Business/EDNSP/planning/2.3%20FINAL %20lnvento ry%20(3-31-10).pdf?n=2007 4) Critical Drainage Area maps Do not apply in the City of Renton per City of Renton Surface Water Design Manual. 5) Sensitive Area Folio See attached Sensitive Area Folio. 6) DNRP Drainage complaints and studies None. 7) Road drainage problems There are no road drainage problems within the study area. 8) U.S. Department of Agriculture, King County Soils Survey The King County Soils Survey map and City of Renton Soils Map show Alderwood soil on the site (AgO on the west portion of the site and AgC on the east portion of the site). See attached Soils map. 9) Wetland Inventory There is no wetland on the site and its adjacent areas. 10) Migrating river studies There is no migrating river within the study area. 17 Reference 11-A Peak Rate Flow Control Standard (Existing Site Conditions) Flow Control Duration Standard (Existing Site Conditions) Flow Control Duration Standard (Forested Conditions) ...... , L._ .. i Renton City limits p ..... . \-.... J Potential Annexation Area / Flow Control Application Map N A Printed 111412010 ----------'-I~tJJtGfJ~ o 2 _-===-_C::::JI ______ MiJes / / / / ( I I , ,-, //< ---::, / '~, 'i L, I I l~ \,r-- c(~ I D~ J~~~~ \ --- \ \ \ \ \ I I , / , \ \ \ \ \ ) / / / City of Renton -Water classes e f:conorruc Developme:1t. \lei,ghborhoods & Strategic Planning .p;M\. Alex Piersch, Adnllm,lnolur \~ j G 0.,1 Ro~"o D RA FT '~ 15 Uclaber 2003 Renton City Boundary PAA Boundary c~ss 1 Class 2 Class 3 Class 4 Culvert 0 I L r'-'-'-'-'- I I I ,_J ._ • ...l 3000 1 : 36000 6000 t ..q y o \ \ Di 'I'. '1' L;\KE YQCNGS ~ 1i JO(lQ / 6000 -- '=~----'-~-'----'----~---~ --'-'~-- AQUIFER PROTECTION ZONES Technical Services PlanninglBuildingIPtblic WOfks R. MacOnie, D. Vssneski January 22, 2008 Renton Mlillicipal Code Zone 1 Q"2Zd Zone 1 Modified :-:-_ -~---------:l Zone 2 ------Citv Limits 1 SEISMIC HAZARD AREAS Technical Services PlanningIBuildinglPublic Worio;s R MacOnie, D. Visneski January 22. 2008 ... ----City limits High Hazard ) ~~. " " -f Information Technology -GIS mapsupport@rentonwa.gov Printed on: 11/12/2014 Data Sources: City of Renton. King County This document is a graphic representation. not guaranteed to survey accuracy, and is based on the best information available as of tile dale shown. This map is intended for City display purposes only. CooTdj"!lte System: NAD 1983 HARN $latePiane Washington North FJP$ 4601 Fee! ProjeCtion: Lambert ConforrTl8/ Conic Datum: North Amencan 1983 HARN t:,.~'j Renton City Limits R Education .e Fire Station ill Valley Medical Center City of Renton Sensitive Areas o Coal Mine Hazards Severity M HIGH :==:) MODERATE C-::') UNCLASSIFIED r---, , ' , , ~/,-.' 1, City of Renton Sensitive Areas Flood Hazard Jublic Works Department 3. Zimmennan, Administrator fechnical Services ~. MacOnie, D.Visneski ::Irinted on May 21, 2009 .. )ata Sam;;e. Public Works, U~lPties Systems., Technical Servk:es --r ..... Cityo! , ----~ r~tnI0n Hazard Condition o 1 . .w<l 2.800' " ,', " Flood Hazard Critical Infrastructure Police Department ,;:~- Fire Stations V Valley MOOIC;;l.1 Ctlnter Schools City of Renton Sensitive Areas '-~=-=r"~-~=\\ --..!.-.:~ Public Works Department G. Zimmerman, Administrator Technical Services R. MacOnie, D. Visneski Printed on May 21, 2009 Data Sctu.ce; PubliC WO!1o:s, U~h~es Systems, Technical Services Stee Sio o 1.400 <.900 ,. " :-rl Renton City Limits '-__ 01 ~"-/J ~--'\ f I. Steep Slopes Percentage Range ::015% & <=25% :>25% & <=40% III >40% & <=90% 111>90% City of Renton Sensitive Areas Erosion Hazards ~'~~/' t )il. --""::=, •. }~ /' " , , ,.~--. " __ 1'_- :>ublic Works Department ?, Zimmerman, Administrator -echnical Services )onnaann Vlsneski, ES3 'rinted on May 21, 2009 • lala Source: Public WorKs, Utilil;es Systems, Technical Serv,CQs ---'---' r ....... Cityof • ~ -----_.r'ctJJ i CJJJ I~ 1,50(1 3,000 ,', ,I HAZARD CONDITION Critical Infrastructure Police Department Frre Stations V Valley Mooical Cent", City of Renton Sensitive Areas Landslide Hazard Public Works Department G. Zimmerman, Administrator Technical Services R MacOn~, D. Visneski Printed on May 21,2009 Data 500rce: Public Works. Utilities Systems, Technical Services o 125a 'J;I)C' !,! [',',' ,.-.r-1 '-.F Renton City Limits LANDSLIDE HAZARD Severity • Very High _High Moderate Unclassified CRITICAL FACILITIES Police Department Fire Stations V Valley Medical Center Schools MERCER Renton Municipal Code ~ Creeks For Reference Only Roads ~ Rivers City Boundary 1 Inch ~ 1 Mile -Wetlands ~-~ Lakes ---Municipality Boundaries I ! , ....a~"" Renton Wetlands Task 3 Field Inspection There is a single family house (built 1946) on the west portion of the site near the Grant Avenue South. The house will be demolished and removed for the proposed development. The remainder of the property is covered with grass with some scattered trees. The site is hilly with average slope of 11 % slopes westerly toward Grant Avenue South. There is no sensitive area on the site. The properties east and south of the site have their own drainage system to intercept runoff before it reach the site. The property north of the site slopes westerly to Grant Avenue South parallel with the site. The properties west of the site are located at elevations lower than the site. The site does not receive significant upstream runoff from adjacent properties. Under existing condition, the site sheet flows westerly to Grant Avenue South. The low point of Grant Avenue South is located near the northwest comer of the site where there are two type 1 catch basins at both sides of the street to collect street runoff. The street drainage system drains to a storm manhole (SDMH#1) near the northwest corner of the site. SDMH#1 has an 18" outfall pipe that discharges westerly to Thunder Hills Creek. The 0.25 mile downstream point is located at the Thunder Hills Creek. The 1 mile downstream point is located at the city storm drainage system that drains to Springbrook Creek. No capacity problem, erosion problem and water quality problem were found within 0.25 miles downstream of the site in the field inspection. 18 .. "' ... , ........... ~ """"'." """"'0 .~""~ •• "O~ Hn, "'-'1.-.... , ... 0 '"~''''''' _ .... o··< .... ,~o ",,''''> •• _,..., .... ,-.. ""'- )jJOMl8N J8lBM 8~BJ-Ins UOlU8tt JO Al!8 IU8>1 '~, PUBIS I JaoJa~ 2_ 3S!d ljl \" - .-. ..-.... • S 11",·-'-•• • • . - King Count 111(' ~1:r:rrn;lll()rll1"rllirl~~ (,n :1'1" ,T~p I'd~ l',c."'l :om~llC' by KIIl'~ CU\.lII:y ~tClfj fIUII::~ -,arl{):Y III ~;()'jrC:I~" ilr:ri I". ~lIhJ2CI to shange V,':~' UlI" C J: ,~~ C~'lill 1·1c.~(O" I 'J ,e 1-11 L" e r: '-itID'l~; r ','.'<'ITCl nLr>s, r'Xr,r(:~s Df If1' :-1,(,<".1, J S Ie ,-cell rac'y, lum,;lr.;tcn ";s",, t ,,",...,h ,,~!> '-'I ".1 ;.~ lu :1 u ~',l ';u;h I '~I:)I rm tl"n Th~ rl:x:u rn~ rt OJ: m:e nJ .od leI" OJse C\:, d ~LI ""'I i-JI oJ LU '<111:] 8,)u rI:)' sh;]11 no: be I;] hie 1.-,' '", ~l:,lcrd, ';I"~"~ ;1(I.'(;cl ·1~ldelli"'1. u'-':"Jn~c8~f.'Il:ld dd1 d~l'~ .n.lucw;; Int nu: ;I'll''(~:: id, '::J~: TVl,nucs 0' b~·. "roil:" Il' ~dtl;l~ I ;:r-I ',II L l!~'" or ITI~,I ,a, (111 h-, Inl,",1',1: c,n GerlalrlC (J O,l :11S map, An 'I 5alc ~'f 11>1 ~ 1"ld;; ur III fJrrT:GllOll (J nIh,'; rna;) 'l~; pr(:iT.:.:':J ,~Xf.'.~t ['j, .. Hlilell ;.lrn ',SlUr! d "'ll i C::'J :1) U:Jtc. 1 O/~i2C1:' Notes tQ King County GIS CENTER -:::-; '-'- -J ::. ~ OJ ~ _ Task 4 Drainage System Description and Potential Problems There are no unsolved existing and potential drainage problems within 0.25 mile downstream of the site. Task 5 Mitigation of Existing or Potential Problems There are no unsolved existing and potential drainage problems within 0.25 mile downstream of the site. For onsite improvement, the proposed project will reserve 11 existing trees (total approximately 170 caliper inches and 10,122 square feet of dripline areas), use a combined detention/wet vault to provide the required Level 2 flow control (use forest condition as existing condition) and use a treatment train of wet vault and Storm Filter manhole with CSF cartridges to provide the required Enhanced Basic water quality treatment. Treated runoff will be discharged to its natural discharged location (SDMH#1 at Grant Avenue South). For offsite frontage improvement, as discussed in Section 1 of this report, no flow control or water quality treatment is required. The proposed development will not create any adverse impact on the downstream drainage system. 19 IV. Flow Control and Water Quality Facility Analysis and Design 20 Part A Existing Site Hydrology Level 2 flow control requires matching developed flow duration from 50% of pre- developed 2 year peak to 50 year peak and matching developed 2 and 10 year peaks with the existing 2 and 10 year peaks. Existing site condition is forest condition per City of Renton Flow Control Application Map. Onsite and offsite improvements Total site area = 2.17 acres (assume till forest). Scale factor = 1.00 & land Use SummaI}' -Area ------. Till Forest 2.17 acres Till Pasture 0.00 acres Till Grass 0.00 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.00 acres ITO~~~~-~~:~sJ Scale Factor: 1.00 Hourly Reduced Time Series: "-lp_re_._ts_f ___________ ....lI_> ....... >1 Compute Time Series I Modify User Input I File for computed Time Series [.TSF] 21 Flow Frequency Analysis Time Series File:pre.tsf Project Location;Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of (CFS) 0,137 2 2/09/01 0,037 7 1/06/02 0.101 4 2/28/03 0.004 8 3/24/04 0.060 6 1/05/05 0.105 3 1/18/06 0,089 5 11/24/06 0.175 1 1/09/08 Computed Peaks Existing peak flows Q2y = 0.060 cfs Q10y = 0.105 cfs Q100y = 0.175 cfs Peak 18,00 3,00 3,00 20,00 8,00 21,00 4,00 9,00 -----Flow Frequency Analysis------- -Peaks Rank Return Prob (CFS) Period 0.175 1 100.00 0,990 0,137 2 25.00 0.960 0.105 3 10.00 0.900 0.101 4 5.00 0.800 0.089 5 3.00 0.667 0,060 6 2.00 0.500 0,037 7 1.30 0.231 0.004 8 1.10 0.091 0.162 50.00 0,980 22 Part B Developed Site Hydrology Onsite improvement Under developed condition, onsite runoffs will be collected and conveyed to the onsite detention system. Impervious area calculation: Total impervious area = 1.38 acres. (roof, driveway, walkway, etc.) Total pervious area = 2.11 -1.38 = 0.73 acres (till grass). Total area = 2.11 acres. :& land Use Summary l=IL'i~ -Area--·--·_· Till Forest 0.00 acres Till Pasture 0.00 acres Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious 0.13 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres 1.38 acres [Total--~-- 2.11 acres .-~-~------ Scale Factor: 1.00 Hourly Reduced 11 Time Series: Lld_e_v ___________ -L.I>--l>1 Compute Time Series I Modify User Input I . File for computed Time Series I.TSF] 23 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 (CFS) (CFS) 0.400 6 2/09/01 2,00 0.806 0.328 8 1/05/02 16:00 0.520 0.480 3 2/27/03 7:00 0.480 0.357 7 8/26/04 2:00 0.430 0.430 4 10/28/04 16:00 0.425 0.425 5 1/18/06 16:00 0.400 0.520 2 10/26/06 0:00 0.357 0.806 1 1/09/08 6:00 0.328 Computed Peaks 0.711 Developed condition peak flows before detention: Q2y = 0.400cfs Q10y = 0.480 cfs Q100y = 0.806 cfs Offsite improvement Counted as bypass areas Rank Return Prob Period 1 100.00 0.990 2 25.00 0.960 3 10.00 0.900 4 5.00 0.800 5 3.00 0.667 6 2.00 0.500 7 1.30 0.231 8 1.10 0.091 50.00 0.980 Under developed condition the right of way frontage improvement will create 1,200 square feet (0.03 acres) new plus replaced impervious area. Total area = 0.06 ac. Impervious area = 0.030 ac. Pervious area = 0.030 ac. (till grass) 24 f} land Use Summary Area-~-jJ Till Forest 0.00 acres Till Pa stu re 0.00 acres Till Grass 0.03 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.03 acres [ Total ~ 0.06 acres ----~~--.---- Scale Factor: 1.00 Hourly Reduced Time Series: Llo~ff~s~ite....:.I __________ ----LI~>"--'>1 Compute Time Series I Modify User Input I File for computed Time Series (.TSF] Flow Frequency Analysis Time Series File:offsite.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0.010 5 2/09/01 2,00 0.008 7 1/05/02 16,00 0.012 2 2/27/03 7,00 0.008 8 8/26/04 2,00 0.010 6 10/28/04 16,00 0.011 4 1/18/06 16,00 0.012 3 10/26/06 0,00 0.020 1 1/09/08 6,00 Computed Peaks Developed condition peak flows: 02y = 0.010 cfs 010y = 0.012 cfs 0100y = 0.020 cfs -----Flow Frequency Analysis------- -Peaks Rank Return Prob (CFS) Period 0.020 0.012 0.012 0.011 0.010 0.010 0.008 0.008 0.018 1 2 3 4 5 6 7 8 100.00 0.990 25.00 0.960 10.00 0.900 5.00 0.800 3.00 0.667 2.00 0.500 1.30 0.231 1.10 0.091 50.00 0.980 25 Part C Performance Standards The site is located in Duration Flow Control Area (Forest existing condition). Since no problem has been identified within the site and its downstream area, level 2 flow control (forest existing condition) is required. Since the project is a multi-family development, Enhanced basic water quality treatment is required. Per SWDM section 1.2.3.3 and 5.2, Flow Control BMPs are required for the onsite development. Since the lot is larger than 22,000 square feet and impervious area coverage of the site is larger than 45%, the large lot high impervious BMP requirements are applied. The feasibility and applicability of full dispersion is studied first, the study found full dispersion is not suitable for this site to fully disperse the new impervious areas and new non-native pervious areas. Also, full infiltration is not suitable for this site because onsite soil is till soil. Even though not counting towards flow control credit, the following flow control BMPs are used: Even though not counting towards flow control credit, the following flow control BMPs are used: 1. Reserve existing trees (11 trees, total 170 caliper inches, 10,112 square feet dripline areas). 2. Perforated tie lines for downspout connections. For onsite improvement, the proposed project will reserve 11 existing trees (total approximately 170 caliper inches and 10,122 square feet of dripline areas), use 10 feet minimum perforated downspout connection for each buildings, use a combined detention/wet vault to provide the required Level 2 flow control (forest existing condition) at the point of convergence (at SDMH#1 at Grant Avenue South) and use a treatment train of wet vault and Storm Filter manhole with CSF cartridges to provide the required Enhanced Basic water quality treatment. Treated runoff will be discharged to its natural discharged location (SDMH#1 at Grant Avenue South). See Section 2 of this report regarding special requirements, the only special requirement applicable to this site is special requirement 1.3.4 for source control. Dumpsters and recycle bins will be stored in the garages of each units. Since the site is not a high use site, oil control is not required. The new onsite conveyance systems is designed per chapter 4 of the KCSWDM to convey the 100 year peak flows. For offsite frontage improvement, as discussed in Section 1 of this report, no flow control or water quality treatment is required. 26 Part D Flow Control System Flow control facility: A combined detention/wet vault is used to provide the required Level 2 flow control (forest existing condition) at the point of convergence. The offsite frontage improvement is counted as bypassed areas. KCRTS method is used to size the detention system. Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 90.00 ft Facility Width: 40.00 ft Facility Area: 3600. sq. ft Effective Storage Depth: 7.95 ft Stage 0 Elevation: 0.00 ft Storage Volume: 28620. cu. ft Riser Head: 7.95 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter 1ft) lin) ICFS) lin) 1 0.00 0.68 0.035 2 4.65 1.25 0.078 4.0 3 7.20 1. 00 0.024 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation 1ft) 1ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 0.00 o. 0.000 0.000 0.00 0.01 0.01 36. 0.001 0.001 0.00 0.02 0.02 72. 0.002 0.002 0.00 0.03 0.03 lOB. 0.002 0.002 0.00 0.04 0.04 144. 0.003 0.003 0.00 0.05 0.05 180. 0.004 0.003 0.00 0.06 0.06 216. 0.005 0.003 0.00 0.21 0.21 756. 0.017 0.006 0.00 0.37 0.37 1332. 0.031 0.008 0.00 0.52 0.52 1872 . 0.043 0.009 0.00 0.68 0.68 2448. 0.056 0.010 0.00 0.84 0.84 3024. 0.069 0.011 0.00 0.99 0.99 3564. 0.082 0.012 0.00 1.15 1.15 4140. 0.095 0.013 0.00 1.30 1.30 4680. 0.107 0.014 0.00 1. 46 1.46 5256. 0.121 0.015 0.00 1. 62 1.62 5832. 0.134 0.016 0.00 1. 77 1.77 6372 . 0.146 0.017 0.00 1. 93 1. 93 6948. 0.160 0.017 0.00 2.08 2.08 7488. 0.172 0.018 0.00 2.24 2.24 8064. 0.185 0.019 0.00 2.39 2.39 8604. 0.198 0.019 0.00 2.55 2.55 91BO. 0.211 0.020 0.00 2.71 2.71 9756. 0.224 0.021 0.00 2.86 2.86 10296. 0.236 0.021 0.00 3.02 3.02 10872. 0.250 0.022 0.00 3.17 3.17 11412. 0.262 0.022 0.00 3.33 3.33 11988. 0.275 0.023 0.00 3.49 3.49 12564. 0.288 0.023 0.00 3.64 3.64 13104. 0.301 0.024 0.00 3.80 3.BO 13680. 0.314 0.024 0.00 27 3.95 4.11 4.27 4.42 4.58 4,65 4,66 4,68 4,69 4,70 4.72 4.73 4.74 4.75 4,91 5.07 5.22 5.3B 5,53 5.69 5.85 6.00 6.16 6.31 6,47 6.62 6.7B 6.94 7,09 7.20 7.21 7,22 7,23 7,24 7,25 7,26 7,27 7,2B 7.29 7.45 7.61 7.76 7,92 7.95 8.05 B.15 8.25 B.35 8.45 8.55 8.65 B.75 8.85 8.95 9.05 9.15 9.25 9.35 9.45 9.55 9.65 9.75 Hyd Inflow 3.95 4.11 4.27 4.42 4.58 4,65 4.66 4.68 4.69 4.70 4.72 4.73 4.74 4.75 4.91 5.07 5.22 5,3B 5.53 5.69 5.85 6.00 6.16 6.31 6.47 6.62 6.7B 6.94 7.09 7.20 7.21 7,22 7.23 7.24 7.25 7.26 7,27 7,2B 7.29 7.45 7.61 7.76 7.92 7.95 8.05 B.15 8.25 8.35 8.45 8.55 8.65 8.75 8.85 8.95 9.05 9.15 9.25 9.35 9.45 9.55 9.65 9,75 Outflow 14220. 14796. 15372. 15912. 164BB. 16740. 16776. 16848. 16884, 16920, 16992. 1702B. 17064. 17100. 17676. 1B252. 1B792. 1936B. 19908. 20484. 21060. 21600. 22176. 22716. 23292. 23832. 24408. 24984. 25524. 25920. 25956, 25992. 26028. 26064. 26100, 26136. 26172, 26208. 26244. 26820. 27396. 27936. 28512. 28620. 2B9BO. 29340. 29700. 30060. 30420. 30780. 31140. 31500. 31B60. 32220, 32580. 32940. 33300, 33660, 34020. 34380. 34740. 35100. 0.326 0.025 0,340 0.025 0.353 0.026 0,365 0,026 0.379 0,027 0.384 0,027 0.385 0.027 0.387 0,028 0.3B8 0.030 0.388 0.032 0.390 0.035 0.391 0.039 0.392 0,040 0.393 0,041 0.406 0.049 0.419 0.056 0.431 0.061 0,445 0.065 0.457 0.069 0,470 0.073 0.483 0.077 0.496 O.OBO 0.509 0,083 0.521 0.086 0.535 0.089 0.547 0,092 0.560 0,095 0.574 0.097 0.586 0.100 0.595 0.101 0.596 0.102 0.597 0.102 0.598 0.104 0,59B 0.105 0.599 0.107 0,600 0.109 0.601 0.110 0.602 0.110 0.602 0.111 0.616 0.119 0,629 0.125 0.641 0.130 0.655 0.135 0,657 0,136 0.665 0.447 0.674 1.010 0.6B2 1.740 0.690 2.540 0.698 2.820 0.707 3.0BO 0.715 3.320 0.723 3.540 0.731 3.750 0.740 3,940 0.748 4.130 0.756 4.310 0.764 4.4 BO 0.773 4.640 0.781 4.800 0.789 4.960 0.79B 5.110 0.B06 5.250 Storage 0,00 0,00 0.00 0,00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0,00 0,00 0.00 0,00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0,00 0,00 0.00 0,00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0,00 0.00 0,00 0,00 0.00 0.00 0,00 0,00 0.00 0.00 0,00 0.00 0.00 Peak Stage Elev (Cu~Ft) (AC~Ft) 28 1 0.81 0.26 7.99 7.99 28761. 2 0.40 0.13 7.66 7.66 27581. 3 0.48 0.09 6.58 6.58 23696. 4 0.52 0.09 6.51 6.51 23428. 5 0.42 0.06 5.29 5.29 19055. 6 0.43 0.04 4.76 4.76 17147. 7 0.33 0.03 4.67 4.67 16824. 8 0.36 0.02 2.99 2.99 10776. Hyd R/D Facility Tributary Reservoir poe Outflow Outflow Inflow Inflow 1 0.26 0.02 ******** 2 0.13 0.01 ******** 3 0.09 0.01 ******** 4 0.09 0.01 ******** 5 0.06 0.01 ******** 6 0.04 0.01 ******** 7 0.03 0.01 ******** 8 0.02 0.01 :Ie******* ---------------------------------- Route Time Series through Facility Inflow Time Series File'; dev. tsf Outflow Time Series File:rdout poe Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.806 Peak Outflow Discharge; 0.258 Peak Reservoir Stage: 7.99 Peak Reservoir Elev: 7.99 CFS CFS Ft Ft Target 0.17 ******* 0.10 ******* ******* 0.06 "':/e***** ******* at 6,00 at 11,00 Peak Reservoir Storage: 28761. Cu-Ft 0.660 Ac-Ft Add Time series:offsite.tsf Calc 0.26 0.13 0.09 0.09 0.07 0.04 0.03 0.03 on Jan on Jan 0.660 0.633 0.544 0.538 0.437 0.394 0.386 0.247 9 in Year 8 9 in Year 8 Peak Summed Discharge: 0.263 CFS at 11;00 on Jan 9 in Year 8 Point of Compliance File:dsout,tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0.127 2 2/09/01 20,00 0.028 7 1/07/02 4,00 0.091 3 3/06/03 22,00 0.022 8 8/26/04 8,00 0.042 6 1/08/05 3,00 0.063 5 1/19/06 0,00 0.090 4 11/24/06 8,00 0.258 1 1/09/08 11,00 Computed Peaks Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0.130 2 2/09/01 20,00 0.031 7 1/05/02 16,00 0.094 3 3/06/03 21,00 0.027 8 8/26/04 2,00 0.043 6 1/08/05 2,00 -----Flow Frequency Analysis------- --Peaks --Rank Return Prob (CFS) (ft) Period 0.258 7.99 1 100,00 0.990 0.127 7.66 2 25.00 0.960 0.091 6.58 3 10.00 0.900 0.090 6.51 4 5.00 0.800 0.063 5.29 5 3.00 0.667 0.042 4.76 6 2.00 0.500 0.028 4.67 7 1. 30 0.231 0.022 2.99 8 1.10 0.091 0.214 7.98 50.00 0.980 -----Flow Frequency Analysis------- --Peaks Rank Return Prob (CFS) Period 0.263 0.130 0.094 0.093 0.065 1 2 3 4 5 100.00 25.00 10.00 5.00 3.00 0.990 0.960 0.900 0.800 0.667 29 0.065 5 1/18/06 23,00 0.093 4 11/24/06 7,00 0.263 1 1/09/08 11,00 6 7 8 2.00 1. 30 1.10 Computed Peaks 0.043 0.031 0.027 0.218 50.00 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS 0.002 0.005 0.009 0.013 0.016 0.020 0.023 0.027 0.030 0.034 0.037 0.041 0.044 0.048 0.051 0.055 0.059 0.062 0.066 0.069 0.073 0.076 0.080 0.083 0.087 0.090 0.094 0.097 0.101 0.104 0.108 0.112 0.115 0.119 0.122 0.126 28152 7792 6633 6874 4170 3501 2006 1574 198 16 8 19 42 32 39 31 33 25 30 17 16 11 14 16 15 16 10 12 5 1 1 1 2 1 2 3 % % % 45.910 12.707 10.817 11 .210 6.800 5.709 3.271 2.567 0.323 0.026 0.013 0.031 0.068 0.052 0.064 0.051 0.054 0.041 0.049 0.028 0.026 0.018 0.023 0.026 0.024 0.026 0.016 0.020 0.008 0.002 0.002 0.002 0.003 0.002 0.003 0.005 45.910 58.617 69.434 80.644 87.445 93.154 96.425 98.992 99.315 99.341 99.354 99.385 99.454 99.506 99.569 99.620 99.674 99.715 99.764 99.791 99.817 99.835 99.858 99.884 99.909 99.935 99.951 99.971 99.979 99.980 99.982 99.984 99.987 99.989 99.992 99.997 54.090 41.383 30.566 19.356 12.555 6.846 3.575 1.008 0.685 0.659 0.646 0.615 0.546 0.494 0.431 0.380 0.326 0.285 0.236 0.209 0.183 0.165 0.142 0.116 0.091 0.065 0.049 0.029 0.021 0.020 0.018 0.016 0.013 0.011 0.008 0.003 Flow Duration from Time Series File:dsollt.tsf 0.541E+00 O.414E+OO 0.306E+00 a .194E+OO 0.126E+00 0.685E-01 0.357E-Ol 0.101E-01 0.685E-02 0.659E-02 0.646E-02 0.615E-02 0.546E-02 0.494E-02 0.431E-02 0.380E-02 0.326E-02 0.285E-02 o .236E-02 0.209E-02 0.183E-02 0.165E-02 0.142E-02 0.116E-02 0.913E-03 0.652E-03 0.489E-03 O.294E-03 0.212E-03 o .196E-03 0.179E-03 0.163E-03 o .130E-03 0.114E-03 0.B15E-04 0.326E-04 cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 0.005 0.009 0.013 0.016 0.020 0.024 0.027 0.031 0.035 0.038 0.042 0.046 0.049 0.053 0.056 0.060 28141 7745 6603 6777 4416 3369 1945 1641 244 34 9 21 43 33 37 28 34 45.892 12.630 10.768 11.052 7.202 5.494 3.172 2.676 0.398 0.055 0.015 0.034 0.070 0.054 0.060 0.046 0.055 45.892 58.523 69.291 80.342 87.544 93.038 96.210 98.886 99.2B4 99.340 99.354 99.388 99.459 99.512 99.573 99.618 99.674 54.108 41. 477 30.709 19.658 12.456 6.962 3.790 1.114 0.716 0.660 0.646 0.612 0.541 0.488 0.427 0.382 0.326 O.S41E+OO O.41SE+OO O.307E+OO Q,197E+OO 0.125E+00 0.696E-01 0.379E-Ol o .111E-01 0.716E-02 0.660E-02 0.646E-02 0.612E-02 0.541E-02 0.488E-02 0.427E-02 0.382E-02 0.326E-02 0.500 0.231 0.091 0.980 30 0.064 0.067 0.071 0.075 0.078 0.082 0.086 0.089 0.093 0.096 0.100 0.104 0.107 0.111 0.115 O.l1B 0.122 0.126 0.129 24 29 20 15 10 15 17 11 19 9 13 4 2 1 1 1 2 2 3 0.039 0.047 0.033 0.024 0.016 0.024 0.02B 0.018 0.031 0.015 0.021 0.007 0.003 0.002 0.002 0.002 0.003 0.003 0.005 Duration Comparison Anaylsis Base File~ pre.tsf New File: dsout.tsf 99.713 99.760 99.793 99.817 99.834 99.858 99.B86 99.904 99.935 99.949 99.971 99.977 99.980 99.982 99.9B4 99.9B5 99.989 99.992 99.997 Cutoff Units: Discharge in CFS 0.287 0.240 0.207 0.183 0.166 o .l42 0.114 0.096 0.065 0.051 0.029 0.023 0.020 0.018 0.016 0.015 0.011 O.OOB 0.003 0.287E-02 O.240E-02 0.207E-02 0.183E-02 0.166E-02 O.142E-02 o .114E-02 0.962E-03 0.6S2E-03 0.506E-03 0.294E-03 0.22BE-03 o .196E-03 0.179E-03 0.163E-03 o .l47E-03 o .1l4E-03 0.815E-04 0.326E-04 -----Fraction of Time--------------Check of Tolerance------- Cutoff 0.030 0.03B 0.046 0.055 0.063 0.071 0.079 0.087 0.096 0.104 0.112 0.120 0.129 0.137 Base 0.9SE-02 O. 64E-02 0.50E-02 0.37E-02 0.29E-02 0.22E-02 0.15E-02 0.10E-02 0.62E-03 0.34E-03 0.21E-03 0.16E-03 0.llE-03 o .16E-04 New %Change Probability Base 0.75E-02 -21.4 I 0.9SE-02 0.030 0.65E-02 1.5 I 0.64E-02 0.03B 0.S3E-02 7.6 I 0.50E-02 0.046 O.40E-02 B.B I 0.37E-02 0.055 0.30E-02 4.0 I 0.29E-02 0.063 0.21E-02 -6.6 I 0.22E-02 0.071 0.16E-02 5.5 I 0.15E-02 0.079 0.10E-02 1.6 I 0.10E-02 0.OB7 0.S2E-03 -15.B I 0.62E-03 0.096 0.23E-03 -33.3 I 0.34E-03 0.104 0.18E-03 -15.4 I 0.2lE-03 0.112 D.llE-03 -30.0 I 0.16E-03 0.120 0.49E-04 -57.1 I 0.llE-03 0.129 O.OOE+OO -100.0 I 0.16E-04 0.137 Maximum positive excursion = 0.003 cfs ( 7.4%) occurring at 0.038 cfs on the Base Data:pre.tsf and at 0.041 cfs on the New Data:dsout.tsi Maximum negative excursion ~ 0.004 cis (-12.8%) occurring at 0.034 cis on the Base Data:pre.tsf and at 0.030 cfs on the New Data:dsout.ts£ New %Change 0.02B -6.9 0.040 4.7 0.049 5.6 0.057 5.2 0.064 1.8 0.069 -2.7 O.OBO 1.3 0.088 0.3 0.094 -1.9 0.099 -4.6 0.107 -4.6 0.116 -3.6 0.123 -4.6 0.130 -4.9 31 f}; "-f Q :+----------------------------------------- - ci " " ci "', • ci lard." ~ d,~ut dur • ------------" ------~t__----------------------------------------'-~-~~,.------------------------------------~ w' " , 00' ,,' Predeveloped duration VS developed duration at point of convergence e.!.".~'!"."".!:-.~ ___________ _ -----------.~----------------.-.---.-I.,.,I(;)~ " pr~ ~ks 'n S~o·Ta~ .. d,out p~~ '00 ,,-~-------------------------------------------------------------------------------- oo--UL--~------~----~------~--~~--"'--~--~r---c_--~,_----~----~.-----~----, 1 10 20 3O~050601O 60 90 S~ 9<199 Predeveloped peaks VS developed peaks at point of convergence 32 -- Peak combined detention/wet vault release rate: Q2y = 0.042 cfs Q10y = 0.091 cfs Q100y = 0.258 cfs Peak developed peak flows at point of convergence: Q2y = 0.043 cfs < 0.060 cfs (existing site condition), o.k. Q10y = 0.094 cfs < 0.105 cfs (existing site condition), o.k. Q1 OOy = 0.263 cfs. The proposed combined detention/wet vault (90' Lx 40' W x 8' H live storage) provides 28,800 cubic feet of live storage. Required live storage is 28,761 cubic feet for the 100 year peak flow, o.k. Two flow control devices are used inside the vault. One is an 8" downturned elbow with a 0.68" bottom orifice and an 8" outfall pipe to the Storm Filter manhole which controls the under 2 year flow to the Storm Filter manhole, the other is a 12" riser for over 2 year flow control. The 12" riser has a 1.25" bottom orifice (used as the 2 nd orifice) and a 1" orifice at a 4" elbow (used as the 3rd orifice), the top of the riser is used for overflow for over 100 year storm event. The 12" outfall pipe for the 12" flow control riser is connected to a type 2 catch basin bypassing the Storm Filter manhole. The vault also has an 8" outfall with shear gate for maintenance dewatering. Use KCRTS method with 15 minute time step to calculate 100 year peak overflow for the detention system. 33 & land Use Summary l=li,l~l i Area --- Till Forestl 0.00 acres Till Pasture 0.00 acres Till Grass 0.73 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 1.38 acres r~tal~ L_ 2.11 acre:] Scale Factor: 1.00 15-Min Reduced Edit Flow Paths I Time Series: Lld_e_v-_l_5_.t_sf _________ --lI_>...J>I Compute Time Series I Modify User Input I File for computed Time Series [.TSFJ Flow Frequency Analysis Time Series File!dev-15.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 0.657 6 8/27/01 18,00 2.00 1 100.00 0.990 0.464 8 1/05/02 15,00 1.41 2 25.00 0.960 1.41 2 12/08/02 17:15 0.916 3 10.00 0.900 0.529 7 8/23/04 14 ,30 0.791 4 5.00 0.800 0.791 4 11/17/04 5,00 0.783 5 3.00 0.667 0.783 5 10/27/05 10,45 0.657 6 2.00 0.500 0.916 3 10/25/06 22,45 0.529 7 1. 30 0.231 2. 00 1 1/09/08 6,30 0.464 8 1.10 0.091 Computed Peaks 1. 80 50.00 0.980 01 OOy overflow = 2.00 cfs 12" riser overflow capacity with head = 0.35' o orifice = 3.728' D" (2)' H " (1/2) = 3.728' 1 '0.35 " (1/2) = 2.21 cfs > 2.00 cfs, O.k. The 12" riser has the capacity to handle the 100 year overflow. 34 Part E Water Quality System On site improvement A treatment train of combined detention/wet vault and Storm Filter manhole with CSF cartridges is used to provide the required Enhanced Basic Water Quality treatment. The Storm Filter manhole with CSF cartridges will be installed downstream of the combined detention/wet vault. The combined detention/wet vault is also used as a pretreatment device for the Storm Filter manhole. Wet vault sizing: Area to be treated: Total impervious area = 1.38 acres Total pervious area = 0.73 acres (till grass) Total drainage area = 2.11 acres Mean annual volume: Vr = (0.9 * Ai + 0.25 * Atg + 0.10 * Atf + 0.01 * Ao ) * R = (0.9 * 1.38 + 0.25 * 0.73 + 0.10 * 0 + 0.01 * 0) * 43560' 0.039 = 2,420 ct. Required dead storage = 3 • Vr = 7,260 cf. The proposed combined detention/wet vault is separated into two cells by a concrete wall in the middle, the west cell is used for detention only, it provide 90' L x 20' W x 8'H = 14,400 cubic feet of live storage, and minimum 6" average depth of sediment storage (900 cubic feet), the east cell is used as a combined detention/wet vault, it provide 14,400 cubic feet of live storage, 90' L x 20' W x 4.1' H = 7,380 cubic feet (> 7,260 ct, o.k.) of water quality dead storage and minimum l' average depth of sediment storage (1,800 cubic feet). Storm Filter sizing: Flow based sizing: The design WQ flow is the 2 year release rate from the combined detention/wet vault Qtreat = Q2y = 0.042 cfs = 18.86 GPM The capacity of the standard 18" high CSF cartridge is Qcart = 7.5 GPM / cartridge Nflow = Qtreat /Qcart = 2.51, Use 3 cartridges. Mass loading sizing: Annual average rainfall P = 38" Percent capture = 90% EMC = 60 mg/L (Seattle area commerciallanduse) Area to be treated: PGIS = 1.38 acres PGPS = 0.73 acres (till grass) Mean annual runoff volume: Vt = (P in)' C' (A acres)' (43560 ct /12 in/tt)· (% Capture) 35 = (38) * (0.9 • 1.38 + 0.25' 0.73) * (43560/12) * 0.9 = 176,846 cf. Annual mass load: Mtotal = (Vt cf) * (EMC mg/L) • (28.3 Llcf) * (1 E-6 kg/mg) • (2.2046 Ibs/kg) = 176,846 * 60 • 28.3 • 1 E-6 * 2.2046 = 6621bs. Assume pretreatment efficiency Epre = 80% (downstream of a wet vault designed to remove 80% TSS) Mpre = 662 * 0.80 = 529.60 Ibs Mpass1 = Mtotal-Mpre = 662 -529.60 = 132.40 Ibs Assume Filter efficiency Efilter = 72% Mfilter = Mpass1 • E filter = 132.40' 0.72 = 95.33 Ibs Mass load capacity of the standard 7.5 GPM ZPG cartridge Mcart = 36 Ibs/cartridge Nmass = Mfilter / Mcart = 95.33/36 = 2.65, Use 3 cartridges. Use the maximum number of cartridges calculated by both flow based and mass loading based sizing methods, three 18" high CSF cartridges with 7.5 gpm/cartridge capacity will be used. The cartridges will be installed in a 72" diameter Storm Filter manhole. The combined detention/wet vault has two flow control devices as described in Part D, only the under two year flows drain to the Storm Filter manhole, the higher flows are bypassed to a type 2 catch basin downstream of the Storm Filter manhole. The 2 year release from the vault is 0.042 cubic feet per second which is less than the overflow capacity (1.5 cubic feet per second) of the Storm Filter manhole. Offsite frontage improvement Total pollution generating impervious area for the offsite improvement is only 480 square feet and is counted as untreated discharge per KCSWDM Section 1.2.8.2.0. No water quality treatment is required for the offsite improvement. 36 V. Conveyance System Analysis and Design Conveyance system is designed to convey the 25 year developed peak flow and check for overflow for developed 100 year peak flow and shall not cause downstream property damage in case overflow happens in 100 year storm event. Use rational method to calculate the 25 year and 100 year 24 hour peaks QR = C * IR * A IR = PR * iR PR = 3.40 inch for 25 year storm = 3.90 inch for 100 year storm iR = aR * Tc A (-bR) Tc = Time of concentration = 6.3 minutes for small areas aR bR iR (for Tc = 6.3 minutes) 25 year 2.66 0.65 0.804 100 year 2.61 0.63 0.819 Total onsite drainage area = 2.11 acres. Total onsite impervious area = 1.38 acres Total onsite pervious area = 0.73 acres (till grass) IR (for Tc = 6.3 minutes) 2.734 3.194 Q25y = C * IR * A = (0.90 * 1.38 + 0.25' 0.73) * 2.734 = 3.90 cfs Q100y = C * IR * A = (0.90 * 1.38 + 0.25 * 0.73) * 3.194 = 4.55 cfs Onsite storm conveyance system consists with 12" storm pipes and catch basins with minimum slope over 2%. Using Manning's method, capacity of 12" ADS N-12 pipe at slope 2% is 5.47 cfs (> 4.55 cfs, o.k.). Q = 1.49 * A • (R**(2/3»*(S**(1/2»/n Where A = area (sf.) N = Manning's roughness coefficient = 0.012 for ADS N-12 pipe R = Hydraulic radius = area Iwetted perimeter (tt) S = slope of the energy grade line (ftlft) King County backwater method will used to verify the capacity of the proposed conveyance systems. 37 VI. Special Reports and Studies Special Reports related to this project: 38 VII. Other Permits Other permits include water and sewer franchise utility permits and right of way improvement permit as required by the City of Renton. 39 VIII. CSWPPP Analysis and Design ESC Plan Analysis and Design (Part A) TEMPORARY EROSION AND SEDIMENT CONTROL 1. The grading for this project is only limited to the onsite improvement and offsite frontage improvement. Temporary Erosion and Sedimentation Control will be provided by utilizing BMPs selected from the 2009 King County Surface Water Design Manual. These BMPS will likely include, but are not necessarily limited to construction entrance for traffic stabilization, silt fencing for parameter protection, plastic sheeting of stockpiles, straw mulch, hydro-seeding of exposed areas, catch basin protection, etc. All new impervious areas and new pervious areas will be treated by a combined detention/wet vault for Level 2 flow control and treated by a treatment train of wet vault and Storm Filter manhole for enhanced basic water quality treatment. At the beginning of the construction, construction entrance and silt fence along the grading limit will be installed. Then, combined detention/wet vault will be installed. The excavation of the vault and the vault itself can be used as temporary sediment trap during construction period. Temporary erosion and sediment control facilities will be maintained during construction period and will be removed after construction is finished. See Temporary erosion and sediment control plan, notes and details at the construction plan set for more details. Also see attached Stormwater Pollution Prevention and Spill (SWPPS) plan. 2. The site is hilly, no sensitive area exist onsite. No special measure is proposed. EROSION AND SEDIMENT CONTROL STANDARDS: ESC measures shall be applied and maintained to prevent, to the maximum extent practicable, the transport of sediment from the project site to downstream drainage systems or surface waters. This performance is intended to be achieved through proper selection, installation, and operation of the above ESC measures as detailed in the ESC Standard (detached Appendix D) and approved by the City of Renton. PERMANENT EROSION AND SEDIMENT CONTROL For Permanent Erosion and Sedimentation Control, access driveways, fire lane and walkways will be paved. Landscape areas will be covered with grass, trees and ground covers. All onsite new impervious areas and new pervious areas will be treated by the combined detention/wet vault for Flow control (Level 2, forest existing condition) and a treatment train of combined detention/wet vault and Storm Filter manhole with CSF cartridges for Enhanced Basic water quality treatment. 40 STORMWATER POLLUTION PREVENTION AND SPILL (SWPPS) PLAN (Part 8) 41 IX. Bond Quantities, Facility Summaries and Declaration of Covenant 42 " X. Operations and Maintenance Manual The onsite and offsite storm facilities will be maintained by the City of Renton. 43 PLANNING DIVISION ENVIRONMENTAL CHECKLIST PURPOSE OF CHECKLIST: City of Renton Planning Division 1055 South Grady Way-Renton, WA 98057 Phone: 425-430-7200 Fax: 425-430-7231 The State Environmental Policy Act (SEPA), Chapter 43.21C RCW, requires all governmental agencies to consider the environmental impacts of a proposal before making decisions. An Environmental Impact Statement (EIS) must be prepared for all proposals with probable significant adverse impacts on the quality of the environment. The purpose of this checklist is to provide information to help you and the agency identify impacts from your proposal (and to reduce or avoid impacts from the proposal, if it can be done) and to help the agency decide whether an EIS is required. INSTRUCTIONS FOR APPLICANTS: This environmental checklist asks you to describe some basic information about your proposal. Governmental agencies use this checklist to determine whether the environmental impacts of your proposal are significant, requiring preparation of an EIS. Answer the questions briefly, with the most precise information known, or give the best description you can. You must answer each question accurately and carefully, to the best of your knowledge. In most cases, you should be able to answer the questions from your own observations or project plans without the need to hire experts. If you really do not know the answer, or if a question does not apply to your proposal, write "do not know" or "does not apply". Complete answers to the questions now may avoid unnecessary delays later. Some questions ask about governmental regulations, such as zoning, shoreline, and landmark designations. Answer these questions if you can. If you have problems, the governmental agencies can assist you. The checklist questions apply to all parts of your proposal, even if you plan to do them over a period of time or on different parcels of land. Attach any additional information that will help describe your proposal or its environmental effects. The agency to which you submit this checklist may ask you to explain your answers or provide additional information reasonably related to determining if there may be significant adverse impact. USE OF CHECKLIST FOR NON PROJECT PROPOSALS: Complete this checklist for nonproject proposals, even though questions may be answered "does not apply." IN ADDITION, complete the SUPPLEMENTAL SHEET FOR NONPROJECT ACTIONS (part D). For non project actions (actions involving decisions on policies, plans and programs), the references in the checklist to the words "project," "applicant," and "property or site" should be read as "proposal," "proposer," and "affected geographic area," respectively. - 1 -06109 A. BACKGROUND 1. Name of proposed project, if applicable: Grant Place Townhomes 2. Name of applicant: Satwant Singh 24419 105'h PL SE Kent, WA 98030 3. Address and phone number of applicant and contact person: Washington Commercial Investment, LLC 24419 105th PI SE Kent WA 98030 206-391-3311 Contact: Satwant Singh Milbrandt Architects 2S Central Way Suite 210 Kirkland, WA 98033 425-454-7130 Contact: David J Vincent 4. Date checklist prepared: November 9, 2015 5. Agency requesting checklist: City of Renton Washington 6. Proposed timing or schedule (including phasing, if applicable): Approximate timeline for construction start would be the summer of 2016, with a 12 month construction timeline and an estimated completion time being the summer of 2017 respectively. 7. Do you have any plans for future additions, expansion, or further activity related to or connected with this proposal? If yes, explain. No 8. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. Geotechnical report prepared by Nelson Geotechnical Associates Inc., Limited Geotechnical Review letter by Cobalt Geosciences, Technical Information report prepared by Pacific Engineering Design, LLC. Traffic Study prepared by Jake Traffic Engineering, Inc. Arborist report for proposed trees to be saved. -3-06109 9. Do you know whether applications are pending for governmental approvals of other proposals directly affecting the property covered by your proposal? If yes, explain. Preliminary Plat for the site under concurrent review with the Preliminary PUD review. 10. List any governmental approvals or permits that will be needed for your proposal, if known. The standard City of Renton permits for construction, including clear and grade, site work construction, building permits and utility extensions will be required for this permit. NPDES permit from WSDOE. Franchise Utility Approvals (Power, Natural Gas, Telephone, Cable TV), Power Utility release letter for use of overhead power easement area. 11. Give brief, complete description of your proposal, including the proposed uses and the size of the project and site. The project will construct 8 residential buildings consisting of 4-5 units each for a total of 36 townhome units on a 2.12 acre parcel located at 1600 Grant Avenue South in Renton, Washington. -4-06109 12. Location of the proposal. Give sufficient information for a person to understand the precise location of your proposed project, including a street address, if any, and section, township, and range if known. If a proposal would occur over a range of area, provide the range or boundaries of the site(s). Provide a legal description, site plan, vicinity map, and topographic map, if reasonably available. While you should submit any plans required by the agency, you are not required to duplicate maps or detailed plans submitted with any permit applications related to this checklist. The project is located at 1600 Grant Avenue South in Renton Washington, parcel number 20230S-90S202 SW Section 20, Township 23N Range SE. B. ENVIRONMENTAL ELEMENTS 1. EARTH a. General description of the site (circle one); flat, rolling, IlilllYJ, steep slopes, mountainous, other _Some Slope ____ _ b. What is the steepest slope on the site (approximate percent slope?) Approximately 10% to 15%. c. What general types of soils are found on the site (for example, clay, sand, gravel, peat, muck)? If you know the classification of agricultural soils, specify them and note any prime farmland. According to a soils report prepared for the property in 2005 where 8 test pits were dug they found loose topsoil to 1.5 feet down and then medium to dense sand and gravel. d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. No signs of a history of unstable soils have been identified on the project site or in the vicinity. e. Describe the purpose, type, and approximate quantities of any filling or grading proposed. Indicate source of fill. The purpose of the fill and grading will be to construct proposed 36-unit townhome development and associated roads and infrastructure. Fill will be onsite cut to fill. There will be approximately 7,000 CV cut and 6,000 CY fill. Source material will be onsite Except for any rock/gravel for construction of walls, roads, or pipe bedding. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Erosion could occur during construction, but standard Best Management Practices will be used to prevent erosion sediment transport in accordance with City permit requirements. - 5 - 06/09 g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? Approximately 6S% h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: Standard Best Practices will be used to prevent erosion in accordance with the City of Renton permit requirements. -6-06/09 2. AIR a. What types of emissions to the air would result from the proposal (i.e., dust, automobile, odors, industrial wood smoke) during construction and when the project is completed? If any, generally describe and give approximate quantities if known. Exhaust emissions from equipment, both diesel and gas operated, will take place during construction. Dust may be emitted during compaction and grading throughout the construction phase. b. Are there any off-site sources of emission or odor that may affect your proposal? If so, generally describe. No c. Proposed measures to reduce or control emissions or other impacts to air, if any: Dust from earthwork activities will be controlled by watering and moisture conditioning. 3. WATER a. Surface Water: 1) Is there any surface water body on or in the immediate vicinity of the site (including year-round and seasonal streams, saltwater, lakes, ponds, wetlands)? If yes, describe type and provide names. If appropriate, state what stream or river it flows into. There is no surface water on the project property or in the immediate vicinity. 2) Will the project require any work over, in, or adjacent to (within 200 feet) the described waters? If yes, please describe and attach available plans. No 3) Estimate the amount of fill and dredge material that would be placed in or removed from surface water or wetlands and indicate the area of the site that would be affected. Indicate the source of fill material. None 4) Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities if known. No 5) Does the proposal lie within a 100-year flood plain? If so, note location on the site plan. No -7-06109 6) Does the proposal involve any discharges of waste materials to surface waters? If so, describe the type of waste and anticipated volume of discharge. No . 8 . 06/09 b. Ground Water: 1) Will ground water be withdrawn, or will water be discharged to ground water? Give general description, purpose, and approximate quantities if known. No 2) Describe waste material that will be discharged into the ground from septic tanks or other sources, if any (for example: Domestic sewage; industrial, containing the following chemicals ... ; agricultural; etc.). Describe the general size of the system, the number of such systems, the number of houses to be served (if applicable), or the number of animals or humans the system(s) are expected to serve. None c. Water Runoff (including storm water): 1) Describe the source of runoff (including storm water) and method of collection and disposal, if any (include quantities, if known). Where will this water flow? Will this water flow into other waters, If so, describe. The source of runoff from the site will be storm water. The storm runoff will be collected in catch basins along the access driveway and roof drain systems for the buildings. 2) Could waste material enter ground or surface waters? If so, generally describe. No d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any: Runoff will be detained for flow control and treated for water quality in a combined vault in accordance with City of Renton requirements prior to discharge to the Grant Avenue South public drainage system. 4. PLANTS a. Check or circle types of vegetation found on the site: _x_ deciduous tree: alder, maple, aspen, other _x_ evergreen tree: fir, cedar, pine, other _x_ shrubs _x_ grass __ pasture __ crop or grain __ wet soil plants: cattail, buttercup, bull rush, skunk cabbage, other __ water plants: water lily, eel grass, milfoil, other _x_ other types of vegetation Black Berry b. What kind and amount of vegetation will be removed or altered? The project will require the removal of approximately 41 trees ranging from 8" to 36" caliper. Trees to be removed are 23 Alder, 3 Cedar, 3 Cherry, 1 Deciduous, 6 Maple, 1 Locust, 3 Fir and 1 Ash. We will also be removing scrub brush that includes blackberry bushes. -9-06/09 c. List threatened or endangered species known to be on or near the site. None d. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: The normally required landscaping for permit approval will be provided by this project. Any tree replacement required to compensate for removal of significant trees will be done in accordance with City of Renton code requirements. S. ANIMALS a. Circle any birds and animals, which have been observed on or near the site or are known to be on or near the site: Birds: hawk, heron, eagle, IsongbirdS!, other _Crows and Chickadee's. __ _ Mammals: deer, bear, elk, beaver, other _Squirrels Fish: bass, salmon, trout, herring, shellfish, other _N/A::-_--- b. List any threatened or endangered species known to be on or near the site. None c. Is the site part of a migration route? If so, explain No d. Proposed measures to preserve or enhance wildlife, if any: None 6. ENERGY AND NATURAL RESOURCES a. What kinds of energy (electric, natural gas, oil, wood stove, solar) will be used to meet the completed project's energy needs? Describe whether it will be used for heating, manufacturing, etc. Gas and Electricity may be used to meet the needs of this project, the project will incorporate energy efficient fixtures and will utilize gas water heaters that will meet a .82 efficiency. b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. No c. What kinds of energy conservation features are included in the plans of this proposal? List other proposed measures to reduce or control energy impacts, if any: None • 10 -06/09 7. ENVIRONMENTAL HEALTH a. Are there any environmental health hazards, including exposure to toxic chemicals, risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this proposal? If so, describe. No 1) Describe special emergency services that might be required. Local fire, police, aid units or ambulances may be required in case of accident or injury during the course of construction. 2) Proposed measures to reduce or control environmental health hazards, if any: None -11 -06/09 b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? The ambient traffic noise from Grant Avenue is expected to be low. No other off-site noise is expected. 2) What types and levels of noise would be created by or associated with the project on a short-term or a long-term basis (for example: traffic, construction, operation, other)? Indicate what hours noise would come from the site. The ambient traffic noise from machinery during working hours will occur during the course of construction. Normal noise from residential neighborhood activities will occur after the project is completed and occupied. 3) Proposed measures to reduce or control noise impacts, if any: Working hours can be established by contract, limiting working hours to weekdays from 7:00 A_M. to 6:00 P.M. unless otherwise approved by the City of Renton. 8. LAND AND SHORELINE USE a. What is the current use of the site and adjacent properties? Residential b. Has the site been used for agriculture? If so, describe. No c. Describe any structures on the site. One single family residence and separate garage. d. Will any structures be demolished? If so, what? All structures on site will be demolished. e. What is the current zoning classification of the site? RM-F f. What is the current comprehensive plan designation of the site? RHO (Residential High Density) g. If applicable, what is the current shoreline master program designation of the site? Not Applicable. -12 -06/09 h. Has any part of the site been classified as an "environmentally sensitive" area? If so, specify. No i. Approximately how many people would reside or work in the completed project? Approximately 70 -80 people will reside in the completed project. j. Approximately how many people would the completed project displace? The project will not displace anyone, current single family home is vacant. k. Proposed measures to avoid or reduce displacement impacts, if any: None I. Proposed measures to ensure the proposal is compatible with existing and projected land uses and plans, if any: The project will be in compliance with all applicable land-use and zoning codes. 9. HOUSING a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low-income housing. Approximately 36 town home units will be provided. They will be configured as middle-income housing. b. Approximately how many units, if any, would be eliminated? Indicate whether high, middle, or low-income housing. One middle income home will be eliminated currently vacant. c. Proposed measures to reduce or control housing impacts, if any: None 10. AESTHETICS a. What is the tallest height of any proposed structure(s), not including antennas; what is the principal exterior building material(s) proposed. Approximately 33'- 7" from the lowest grade to the highest peak. b. What views in the immediate vicinity would be altered or obstructed? None -, 3 -06109 c. Proposed measures to reduce or control aesthetic impacts, if any: The architectural design and finishes will be in compliance with the City of Renton Land use Codes and design guidelines. 11. LIGHT AND GLARE a. What type of light or glare will the proposal produce? What time of day wou Id it mainly occur? The proposed development will produce the normal light and glare typically resulting from a residential/multifamily neighborhood. b. Could light or glare from the finished project be a safety hazard or interfere with views? No c. What existing off-site sources of light or glare may affect your proposal? None d. Proposed measures to reduce or control light and glare impacts, if any: The light from the development can be shielded and / or directed away from adjacent properties to prevent safety hazards and protect views as applicable. 12. RECREATION a. What designated and informal recreational opportunities are in the immediate vicinity? None b. Would the proposed project displace any existing recreational uses? If so, describe. No c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project or applicant, if any: A tot lot and small park area will be provided as a part of this development. 13. HISTORIC AND CULTURAL PRESERVATION a. Are there any places or objects listed on, or proposed for, national state, or local preservation registers known to be on or next to the site? If so, generally describe. No -14 -06109 b. Generally describe any landmarks or evidence of historic, archaeological, scientific, or cultural importance known to be on or next to the site. None c. Proposed measures to reduce or control impacts, if any: Not Applicable 14. TRANSPORTATION a. Identify public streets and highways serving the site, and describe proposed access to the existing street system. Show on site plans, if any. The site is directly served by Grant Avenue South, which is fed by Puget Drive SE, which is fed by Benson Road South and then Interstate 405. b. Is site currently served by public transit? If not, what is the approximate distance to the nearest transit stop? The site is not directly served by public transit. Bus service is available on Puget Drive SE approximately 1,000 feet to the South. c. How many parking spaces would the completed project have? How many would the project eliminate? The project will provide 2 parking stalls in enclosed garages for each unit for a total of approximately 72 enclosed spaces, and an additional 7 uncovered stalls for a total or approximately 79 stalls. d. Will the proposal require any new roads or streets, or improvements to existing roads or streets, not including driveways? If so, generally describe (indicate whether public or private? The proposal will include a private drive aisle entering the site at the North West corner looping around and exiting at the South West corner. e. Will the project use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. No f. How many vehicular trips per day would be generated by the completed project? If known, indicate when peak volumes would occur. Based on our traffic analysis, 199 net new daily trips will be generated by our project. g. Proposed measures to reduce or control transportation impacts, if any: None 15. PUBLIC SERVICES -15 -06/09 a. Would the project result in an increased need for public services (for example: fire protection, police protection, health care, schools, other)? If so, generally describe. No b. Proposed measures to reduce or control direct impacts on public services, if any. None 16. UTILITIES a. Circle utilities currently available at the site: lelectricitV\, Inatural ga~, IWiiM Irefuse servicel, ~elephone~ ~anitary sewed, septic system, other. b. Describe the utilities that are proposed for the project, the utility providing the service, and the general construction activities on the site or in the immediate vicinity which might be needed. Utilities proposed for the project include new sanitary sewer and water, new telephone, cable TV/Communications, power and gas. C. SIGNATURE I, the undersigned, declare under penalty of perjury under the laws of the State of Washington that to the best of my knowledge the above information is true, correct, and complete. It is understood that the lead agency may withdraw any declaration of non-significance that it might issue in reliance upon this checklist should there be any willful misrepresentatio r willful lack of full disclosure on my part. \ Proponent signature:(_...l..l;,.,\ck..:...J...c:....:.::::.... __ ~ _____ _ Name Printed: . ;6 Date: -16 -06/09