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Home My WebLink About03872 - Technical Information Report g.zj $� �ba 2�1 L 1 .. . - :- ;` �,�'{ ,�� r-.t�£ �{ �g,,.. s.� , �.� �5�� •`, �'�y�:+ � t.,t��f'��;�L,�j ��.- � �,t�,' �s s+- j��`+ '� �°�Y.. S Y.3R SS�rT)' ,.,.:� �"�"s.,, �`-�'t f ''� � �1� .: - r � � �!f� �w�, `.�^ 'Ar-5��..� �4t] t�' I I I I �� ' I i. . - ��y � a.-��:r � s .�,,�• � j ' � t� f��+' �+.+� ; °--,.Q � �...r �`�i� 'k :;�p�. }T��;..j,•i� ' k,.~,��e . ..' � K� ��i� J. 5� ��. `1`` .",\ � . �;� �`. �� :� : -'�.� r'� �..... r>�`' d� �_ . t �.., Technical Information Report For Liedolo Apartments Date Prepared: November 16, 2015 Site Address: 520 Williams Avenue South Renton, WA 98055 Parcel Number: 723150-1545 Project Number: B15 002961 U15 002967 Prepared By: Lisa A. Harbert, P.E. �..�,,--f : ,� :., � . r� � A� � t��g�'�� - �` �,�, r f ��` �-,r �,'15�. � ♦ -° ''�t � a �'.�:;:�'o•� � 47529 � ��v�= i ��`` ��S�ONAL ��` ,ti�� `" •• titi I Lisa A. Harbert PE, PLLC � ��F� I RECE�VED 2021 201St PL SE #309 ' Bothell, WA 98012 DEC 2 9 2015 Phone: (206)371-3079 Email: LisaHarbert@ymail.com BUtLDING DtVISION 38�.2 � Table of Contents TIRWorlcsheet .......................................................................................................... 4 TIR Section 1: Project Overview ..................................................................................... 9 TIR Section 2: Conditions and Requirements Summary ......................................................... 10 TIR Section 3: Offsite Analysis ..................................................................................... 11 Task 1: Define and Map the Study Area .................................................................. 11 Task 2: Review all Available Information on the Study Area ......................................... 11 Task 3: Field Inspect the Study Area ..................................................................... 12 Task 4: Describe the Drainage System, Its Existing and Predicted Drainage and Water Quality Problems .......................................................................... 12 Figure1: Site Map ........................................................................................... 13 Figure2: Upstream Basin .................................................................................. 14 Figure 3: Downstream Storm Drain ...................................................................... 15 Figure 4: Utilities Within Analysis ...................................................................... 16 TIR Section 4: Flow Control and Water Quality Facility Analysis Design .................................. 21 ' TIR Section 5: Conveyance System Analysis and Design ...................................................... 25 TIR Section 6: Special Reports and Studies ...................................................................... 26 TIR Section 7: Other Permits ....................................................................................... 27 TIR Section 8: CSWPPP Analysis and Design ................................................................... 28 Drainage Assessment/SVVPPP..................................................................................................................28 Minimum Requirement 1: Preparation of Stormwater Site Plans.......................................................29 Minimum Requirement 2: Construction Stormwater Pollution Prevention.......................................30 Element#1—Preserve Vegetation/Mark Clearing Limits...................................................................30 Element#2—Establish Construction Access.......................................................................................30 Element#3—Control Flow Rates........................................................................................................30 Element#4—Install Sediment Controls..............................................................................................31 Element#5—Stabilize Soils.................................................................................................................31 Element#6—Protect Slopes...............................................................................................................31 . , Element#7—Protect Drain Inlets.......................................................................................................31 Element#8—Stabilize Channels and Outlets.....................................................................................31 Element#9—Control Pollutants.........................................................................................................32 Element#10—Control De-watering...................................................................................................32 Element#11—Maintain BMPs............................................................................................................32 Element#12—Manage the Project....................................................................................................32 Element#13—Protect Low Impact Development BMPs....................................................................32 Minimum Requirement 3: Source Control of Pollution........................................................................33 Niinimum Requirement 4: Preser�ation of Natural Drainage Systems and Outfalls.........................33 Minimum Requirement 5: On-site Storm VVater Management...........................................................33 Minimum Requirement 6: Runoff Treatment........................................................................................33 Minimum Requirement 7: Flow Control................................................................................................33 Minimum Requirement 8: R'etlands Protection....................................................................................33 Minimum Requirement 9: Operations and Maintenance.....................................................................33 BMP List for Contractor ............................................................................................................................ 34 TIR Section 9: Bond Quantities,Facility Summaries,and Declaration of Covenant ......................... 35 TIR Section 10: Operation and Maintenance Manual ............................................................ 42 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN NtANUAL • • TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGI�EER DESCRIPTION Project Owner �z;� 1�C'�(1��5C C Jl1 r Project Name � �d L�C �'P�r�'m� �� : Phone �� - �yU— 2�\�j DDES Permit# I Address Location Township Range Project Engineer �1� �C�-t �'�( Section � Company �.�SG- �•�L��'�, �,�� Site Address Gi2�;- �i�� I�►C�i'1�15(�,� � Phone ' '�� - �-�� Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS ❑ Landuse Services ❑ DFW HPA ❑ Shoreline Subdivison / Shcrt Subd. / UPD ❑ COE 404 Management Building Servi�es ❑ DOE Dam Safety � Structural MI I Commerical / SFR RockeryNault/ Clearing and Grading � FEMA Fioodplain ❑ ESA Section 7 Right-of-Way Use ❑ COE Wetlands ❑ Other ❑ Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review �/ Targeted / Type (circle one): Full / Modified / (circle): Large Site Small Site Date (include revision �� Date (include revision ��{�1� dates): dates): Date of Final: Date of Final: Part 6 ADJUSTti1ENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental ! Blanket Description: (include conditions in TIR Section 2) Date of A roval: 2009 Surface Water Design Manual 1'9:'2009 1 KING COUNTY, WASHINGTO�, SURFACE WATER DESIGN v1ANUAL ' ' TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Requirad: Yes No Describe: Start Date: Completion Date: Part 8 SITE COAIMUNITY AND DRAINAGE BASIN Community Plan : Special District O��eriays: Drainage Basin: i�'�� UE� Stormwater Requirements: Part 9 ONSITE F�ND ADJACENT SENSITIVE AREAS �UC (l�. ❑ RiverlStream ❑ Steep Slope ❑ Lake ❑ Erosion Hazard ❑ Wetlands ❑ Landslide Hazard ❑ Closed Depression ❑ Coal Mine Hazard ❑ Floodplain ❑ Seismic Hazard ❑ Other ❑ Habitat Protection ❑ Part 10 SOILS Soii Ty�e Slopes Erosion Potential t�C� �High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other ❑ Seeps/Springs ❑ Additional Sheets Attached 2009 Surface Water Design Manual 1:'9i2009 2 KING COUNTY, Vl'ASHINGTON, SURFACE WATER DESIGN MANUAL I � � TECHNICAL INFORMATION REPORT (TIR) WORKSHEET '�, Part 11 DRAINAGE DESIGN LIMITATIONS I, REFERENCE LIMITATION/SITE CONSTRAINT �I ❑ Core 2—Offsite Analvsis ❑ Sensitive/Criti�ai Areas ❑ SEPA ❑ Other ❑ ❑ Additional Sheets Attached Part 12 TIR SUMVIARY SHEET provide one TIR Summa Sheet perThreshold Dischar e Area) Threshold Discharge Area: name or descri tion Core Requirements (all 8 apply) Dischar e at Natural Location Number of atural Dischar e Locations: v� Offsite Analysis Level: 1 2 / 3 dated: Flow Control lU Level: 1 / 2 / 3 or Exemption Number incl. facili sumrna sheet Small Site BMPs � r- (1C�C �' L t'� Conveyance System Spill containment located at: � Erosion and Sediment Control ESC Site Supervisor: Contact Phone: �J �� After Hours Phon � Maintenance and Operation Responsibility: Private Public If Private, Maintenance Lo e uired: Yes No Financial Guarantees and Provided: Yes / No Liabili WaterQuality �� Type: Basic / Sens. Lake / Enhanced Basicm / Bog (include facility summary sheet) � or Exemption No. Landsca e Mana ement Plan: Yes / No S ecial Re uirements as a licable Area Specific Drainage Type: CDA/SDO/MDP/ BP/ LMP J Shared Fac. / None Re uirements Name: Floodplain/Flcodway Delineation Type: Major / Minor / Exemption 1 None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: Source Control Describe landuse: (comm./industrial anduse) Describe any structural controls: 2009 Surface �E'ater Desian Manual 1 9 2009 ` 3 KING COUNTY, VVASHINGTON, SURFACE WA7"ER DESIGN MANUAL ' ' TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Draina e Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION �Clearing Limit� �(.,t„�� Stabilize Exposed Surfaces Cover Measures Remove and Restore Temporary ESC Facilities Perimeter Protection Clean and Remove Ali Silt and Debris. Ensure Traffic Area Stabilization Operation of Permanent Facilities Sediment Retantion ❑ Flag Limits of SAO and open space preservation areas ❑ Surface Wate•Collection ❑ Other ❑ Dewatering Control �Dust Control ❑ Flow Control Part 14 STORMV'JATER FACILITY DESCRIPTIONS Note: Include Facili Summa and Sketch Flow Control T e/Descri tion Water Qualit T e/Descri tion ❑ Detention ❑ Biofiltration ❑ Infiltration ❑ Wetpool ❑ Regional Faci!ity ❑ Media Filtration ❑ Shared Facilit�r ❑ Oil Control ❑ Flow Control ❑ Spill Control BMPs ❑ Flow Control BMPs ❑ Other ❑ Other ?009 Surface�V'ater Desi�n Manual 1'9'2009 � � KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL ' ' TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS ❑ Drainage Easement ❑ Cast in Place Vault ❑ Covenant ❑ Retaining Wall ❑ Native Growth Protection Covenant ❑ Rockery >4' High ❑ Tract ❑ Structural on Steep Slope ❑ Other ❑ Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civii engineer under my supervision, have visited the site. Actual site conditions as observed were incor orated int is w rksheet and the attached Technical Information Report. To the best of my kno le ge the � rmati n pro�ed here is accurate. �, j,' 11-16-2015 Si ned/Date 2009 Surface Water Design Manual 1%9,'2009 5 . , TIR Section l: Project Over��ie�� The project is located in the City of Renton and is zoned R\�1-�. The l��t size is 6,0O(l SF and an existing house exists on the lot The existing house is prop��sed te, h� clem�,lishecl ancl four new attached apartment t��nh��mc� huilt. The lot front� ��'illiam� _1��nuc So�ith ��n tllc ��cst. �I�h�� l��t i� ��ei�v tlat. :��ordin�� t�� 1:�• King County I-Maps, the general slope of the property is fn� � �' , � �! � � � . ..� :�! � � All existing impervious areas will be removed and replaced The townhomes will be on the south side of the lot with the drive��ay on the north side. Th�� driveway will be approximately 1,638 square feet of impervious surface, the building with overhangs will be 2,863 square feet and a sidewalk in the front will be 65 square feet. The tu�..` proposed impervious surface is 4,566 square feet. The total proposed clearing for the buildin�i _ 1 , _ , _ - _ _ � � -- and feasibility of full dispersion was considered tirst. It was determined full dispersion was n� feasible due to the small site. Full infiltration was considered next, but the soils report states tl,: water table could be high and the soils are not compatible with infiltration. Basic dispersion � considered next and dismissed since we cannot guarantee the discharge will flow over the neighbor's yard. We are planting several trees on the site that will collect any discharge comi� from upstream. The onsite discharge, however, will be collected and tightlined to the existin� storm drain on Williams Avenue. . , TIR Scction ?: Conclitions and Rc�luirements Summary Density- the minimum density in RVI-�� zone is 2� dwelling units per net acre (dw'ac) and the maximum density permitted is 75 dwelling units per net acre. —Based on a lot size of 6,000 square feet, the proposal of 4 units would result in a net densit�- �f 2R.�7 clti!ac. The pr�jc�c•r site falls within the density range permitted for the R1�7-U zon� Minimum Lot Size, Width and Depth—There is no minimum lot �.. _ :�.i..,:_.. :.; :.:_ !:'.: zone. The minimum width required in the RM-U zone is 50 feet and the minimum depth reqtu � - a� . , �. �. , . _., �� .. .. ..� .. � �,,� r a � . .. ..: ... . . . ... . . ._. size. Lot Lu��ra��- iilc ic��i-i. zua� p�rni�t� a �11u�unum �uiluiil� .;u��rabc ot ;�� p�r��i�t a��. maximum impervious surface coverage of 85 percent of the total lot area. —The proposeci lot building coverage is 47.7%. The proposed impervious surface coverage is 76.1%. Setbacks- Setbacks are the distance between the building and the property line or any private access easement. Setback requirements in the RM-U zone are as follows: 5-foot minimum front yard setback, provided the garage maintains a 20-foot front yard setback; a minimum 5 foot side yard setback for lots with a width equal to or less than 50 feet, for structures over 30 feet in height the structure shall be setback 1 additional foot from side property lines for each 10 feet of height in excess of 30 feet to a maximum setback of 20 feet; and a minimum 5-foot rear yard setback. Front and rear setbacks in the RM-U Zone may be reduced to zero (0') during the site development plan review process provided the applicant demonstrates that the project will provide a compensatory amenity such as an entryway courtyard, private balconies or enhanced landscaping. —The proposed project meets these setbacks. Buildin Heigl t- The maximum building height permitted in the RM-U zone is 30 feet per the interim zoning standards. —The proposed building height is 30 feet. Landscapin�— Except for critical areas, all portions of the development area not covered by structures, required parking, access, circulation or service areas, must be landscaped with native, drought-resistant vegetation cover. The minimum on-site landscape width required along street frontages is 10 feet. —A landscape plan is being submitted. Tree Preservation- There are no significant trees on this propert,y. . , TIR Section 3: Offsite Analysis Level 1 Downstream Analysis Task 1: Define and map the study area The Liedolo Apartments occupies 6,000 square feet on the east side of Williams Avenue South in the City of Renton, Washington. The project lies in the SW%of Section 17,Township 23, Range 5. The property address is 520 Williams Avenue South. The property is rectangular in shape and is accessed from the west off Williams Avenue South. The general slope of the property is from northeast to southwest. The project includes the installation of four new attached townhome apartments. Currently there is a single family home on the property. Figures 2 and 3 of this report show the hydrologic study area for this project. Figure 2 shows the upstream boundary, while Figure 3 shows the downstream flow path for%-mile from the site. There is storm drain for the entire downstream flow length. The storm drain eventually outfalls to Black River. Figure 4 shows all the utilities and the locations of the three fire hydrants within 30�feet of the site. Task 2: Review all available information on the study area To assist the design engineer in preparing an offsite analysis, King County has gathered information regarding existing and potential flooding, erosion,and water quality problems. For all levels of the analysis, all of the resources described below shall be reviewed for existing/potential problems in the study area (upstream and one mile downstream of the project site): - Adopted basin plans—No adopted basin plans were discovered. - Floodplain/Floodway(FEMA) maps—See Figure 5 There is a mapped floodplain to the northeast of this site on the Cedar River. There is no floodplain on this site. The Black River is also has mapped floodplain, but since it was so far downstream and does not affect this project it was not included. - Offsite analysis reposts in the same subbasin—No other downstream analysis were obtained. - Sensitive Areas Folio— a. According to the Renton soils in,this parcel is within a Groundwater Protection Area. b. This project is in a Seismic Hazard Area. - Drainage Complaints and studies—There were no drainage complaints found in the area. - Road Drainage problems—No roadway drainage problems were noted. - King County Soils Survey—The Web Soil Survey from the USDA was used to determine the soils. The Soils Maps can be found in Figure 6. Urban Soils were the only soils present. - Wetland Inventory Maps—There are no wetlands in the vicinity of this project. - Migration River Studies—There are no streams in the vicinity of the project. - Section 303d list of polluted waters—There are no streams near the property or with the downstream limits of this study. Task 3: Field inspect the study area The downstream study limit is all urban streets with storm drains. This engineer walked the% mile downstream. There was nothing unusual found except that the manhole and inlet on Grady Way were not visible. The inlet c�uld have been covered by high brush, but the manhole was not found. It should be in the driveway, but maybe more brush has grown and I just didn't see it. I did look around and then went back on google earth and didn't see it either. Task 4: Describe the drainage system, its existing and predicted drainage and water quality problems The existing drainage system flows south on Williams,turns to the southwest along Grady and then turns west onto 7t''Ave. The storm drain continues on 7th well past the% mile and the 1 mile downstream limits. It turns north on Naches and then discharges to the Black River. By the time the storm drain reaches Naches, it is a 60 inch pipe. 1:„ ,. 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S�. . . . � ^ �'� it 1 �? 9�i �� j a yy� ��• ��{ � ��it ��'��.. t�� . �•�1�. ?aF" e'- r �t �"�"�' ` "�^'� � .'�, �^"a � �� ^��'r kp . �. °"� � ��r�'�z�� ¢�� °�� ° � ,�,�j $�'��(��' �'� � � �~�'� � �� u»k.w . WI< .di1"P rr„,W� „� i . „ k H�d.� . . TIR Section 4: Flow Control and Water Quality Facility Analysis Design No flow control is required since we do not increase the discharge by more than 0.1 cfs. KCRTS was run to check for the .1 cfs requirement KCRTS Output Storm Pre Post 2 0.011 0.024 10 0.016 0.029 25 0.017 0.034 100 0.027 0.047 No water quality is required since we are not installing more than 5000 sq ft of pollution generating impervious area. KCRTS Command CREATE a new Time Series ------------------------ Production of Runoff Time Series Project Location : Sea-Tac Computing Series : Pre.tsf Regional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time Series File Loading Time Series Fi1e:C:\KC SWDM\KC DATA\STOG60R.rnf Outwash Grass 0.09 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STEI60R.rnf Impervious 0.04 acres -------------- Total Area : 0.14 acres Peak Discharge: 0.027 CFS at 6:00 on Jan 9 in Year 8 Storing Time Series File:Pre.tsf Time Series Computed KCRTS Command CREATE a new Time Series ------------------------ Production of Runoff Time Series ' Project Location : Sea-Tac , Computing Series : Post.tsf Regional Sca1e Factor : 1.00 Data Type : Reduced , Creating Hourly Time Series File � Loading Time Series File:C:\KC_SWDM\KC_DATA\STOG60R.rnf �, Outwash Grass 0.05 acres i Loading Time Series File:C:\KC_SWDM\KC_DATA\STEI60R.rnf �� Impervious 0.09 acres Total Area : 0.14 acres Peak Discharge: 0.047 CFS at 6:00 on Jan 9 in Year 8 Storir_g Tim.e SeYies Fi=e:Post.�sf Time Series Computed KCRTS Command Enter the Analysis TOCLS Nlodule Analysis Tools Command ---------------------- Compute PEAKS and Flow Frequer_cie� ' ----- ---------- --- ---------------- Loading Time Series File:pre.tsf Flow Frequency Analysis -------------------------------------------------------- Time Series File:pre.tsf Project Location:Sea-Tac Frequencies & Peaks saved to File:Pre.pks Analysis Tools Command ---------------------- Compute PEAKS and Flow Frequencies Loading Time Series File:post.tsf Flow Frequency Analysis -------------------------------------------------------- Time Series File:post.tsf Project Location:Sea-Tac Frequencies & Peaks saved to File:post.pks Analysis Tools Command ---------------------- RETURN to Previous Menu ----------------------- KCRTS Command , ------------- �I eXit KCRTS Program ------------------ � i Flow Frequency Analysis Time Series File:pre.tsf II Project Location:Sea Tac , ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- !, Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.013 4 2/09/01 2:00 0.027 1 100.00 0.990 0.009 8 1/05/0216:00 0.017 2 25.00 0.960 0.017 2 2/27/03 7:00 0.016 3 10.00 0.900 0.011 7 8/26/04 2:00 0.013 4 5.00 0.800 0.013 5 10/28J0416:00 0.013 5 3.00 0.667 0.011 6 1/18/0616:00 0.011 6 2.00 0.500 0.016 3 10/26/06 0:00 0.011 7 1.30 0.231 0.027 1 1/09/08 6:00 0.009 8 1.10 0.091 Computed Peaks 0.023 50.00 0.980 Flow Frequency Analysis Time Series File:post.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 0.024 6 2/09/01 2:00 0.047 1 100.00 0.990 0.020 8 1/05/0216:00 0.034 2 25.00 0.960 0.029 3 2/27/03 7:00 0.029 3 10.00 0.900 0.023 7 8/26/04 2:00 0.028 4 5.00 0.800 0.028 4 10/28/0416:00 0.024 5 3.00 0.667 0.024 5 1/18/0616:00 0.024 6 2.00 0.500 0.034 2 10/26/06 0:00 0.023 7 1.30 0.231 0.047 1 1/09/08 6:00 0.020 8 1.10 0.091 Computed Peaks 0.043 50.00 0.980 TIR Section 5: Conveyance System Analysis and Design Lot area is 6000 sq ft Rational Method: existing grass 4106 0.094261 impervious 1894 0.04348 0.137741 proposed C grass 1944 0.044628 0.25 486 impervious 4056 0.093113 0.9 3650.4 6000 0.137741 4136.4 0.6894 ' Therefor C= .69 i= 3.4 A= .138 Acres Tc=6.3 minutes Q=0.32 cfs KCRTS: Results Pre Post 2 0.011 0.024 10 0.016 0.029 100 0.027 0.047 �ither ��-ay the �� minin�um pipe is rnore than �ui�iicient to handle the discl�ar�� Two catch basins are being installed within the driv��vay c..c capture the runoff from the driveway. The roof drains will also be connected to the catch basins. � . TIR Section 6: Special Reports and Studies There is a Geotechnical Report being submitted in a separate document. No other special reports were done. � ' ' I TIR Section 7: Other Permits � No other permits are being obtained. . r f fK �.�ti��,�, �. �'��1�f'f'f' .�n�,�,�.�i� �.�n�l [)��:_n Draiiia�c: ��ssc:ssln�nt ; S11'YPE' William Avenue Apartments 520Wil1iamsAvenueSouth, R��:�t��, ��.� �>ti'�� The project is located in the City of Renton and is zoned RNI-U. The lot size is 6,000 S} and an existing house exists on the lot. The existing house is proposed to be demolished and four new attached apartment townhomes built. The lot fronts Williams Avenue South on the west. The lot is very flat. According to the King County I-Maps,the general slope of the property is from the northeast to the southwest. All existing impervious areas will be removed and replaced. The townhomes will be on the south side of the lot with the driveway on the north side. The driveway will be approximately 1,638 square feet of impervious surface, the building with overhangs will be 2,863 square feet and a sidewalk in the front will be 65 square feet. The total proposed impervious surface is 4,566 square feet. The total proposed clearing for the house, yard, and driveway is the fu116,000 square feet. To address the requirements for mitigation of target impervious surface, the applicability and feasibility of full dispersion was considered first. It was determined full dispersion was not feasible due to the small site. Full infiltration was considered next,but the soils report states the water table could be high and the soils are not compatible with infiltration. Basic dispersion was considered next and dismissed since we cannot guarantee the discharge will flow over the neighbor's yard. We are planting several trees on the site that will collect any discharge coming from upstream. The onsite discharge, however, will be collected and tightlined to the existing storm drain on Williams Avenue. We are installing two catch basins to collect the water on site. The downspouts will be connected to the catch basins. In order to prevent erosion and trap sediments within the project site, the following BMP's will be used as shown on the Site P1an/Stormwater Pollution Prevention Plan: • Clearing limits are identified by existing fencing on the north and south sides. Also, filter fabric fence/straw wattles are proposed to be installed on the perimeter of the site. • A construction entrance will be installed where the proposed driveway is to be installed. • Mulch will be spread over the cleared areas and soil stockpiles will be covered within 24- hours with visqueen or mulch. � T m r i e Plans I 1VLmmum Requirement 1: Preparatton of Stor wate S t Step 1: Collect and Analyze Information on Existing Conditions. • This engineer, Lisa A. Harbert, PE, visited the site on May 24, 2015. o A land survey was done by Encompass on May 5, 2015 and provided to this engineer. o A geotechnical engineering study was completed by GeoResources, LLC on April 30, 2015. o The aerial view of the site in Google Earth was consistent with the Site Visit except that the garage and shed have been removed. o Existing features and proposed development was provided to this engineer by the designer, Bill Bertch. o The site slopes from the northeast to the southwest at a very gradual slope. Step 2: Prepare Preliminary Development Layout � The Stormwater Pollution Prevention Plan serves as the site plan. The proposed townhome apartments will be located on the south side of the lot and the driveway will be on the north side of the lot. Step 3: Preform Off-site Analysis (at local go��ernment's option) • A downstream analysis is included in Section 3 of this document. Step 4: Determine applicable minimum requirements. There is approximately 4,566 square feet of new impervious area proposed. Because the project proposes more than 2,000 square feet of new impervious area,but less than 1-acre of land disturbing activity, small lot requirements MR#1-9 apply. Step 5: Prepare a Permanent Stormwater Control Plan • A Permanent Stormwater Control Plan is included with this submittal and is titled Site P1an/Stormwater Pollution Prevention Plan. Step 6: Prepare a Construction Stormwater Pollution Prevention Plan (SR'PPP) • This Section of the report serves as the SWPPP. Step 7: Complete the Stormwater Site Plan: • The Stormwater Pollution Prevention Plan serves as the site plan. Step 8: Check Compliance �rith All Applicable �Iinimum Requirements: � The Storm��-ater Pollution Prevention Plan meets all minimum requirements. Dlinimum Requirement 2: CS��'PPP This report serves as the SWPPP. • Elements #1-13 are as shown below: Element#1— Preserve Vegetation/Nlark Clearinb Limits To protect adjacent properties and to reduce the area of soil exposed, the limits of constructic�r. will be clearly marked before land-disturbing activities begin. Native topsoil shall be retaine�! ��. an undisturbed state to the maximum extent possible. The BMPs relevant to markin�the clearing limits that will be applied for this pr�j�.�� . _ ..,._ • BMP C233: Filter Fabric F� � . e P.�TP ('1Z�• CtT..�� \'��ttl�� LIcllllili N' — L�I�iI)11J11 1�U11�1['Ul[lUll �1l'l'l�'� Construction access or activities occurring on unpaved ai�eas shall be minimized, yet �� necessary, access points shall be stabilized to minimize the tracking of sediment onto pul� roads, and wheel washing, street sweeping, and street cleaning shall be employed to pre�� sediment from entering state waters. All wash wastewater shall be controlled on site. Th specific BMPs related to establishing construction access that will be used on this project include: � BMP C105: Stabilized Construction Entrance The entrance to the site will be off of Williams Avenue S. A construction entrance will be established as shown on the plans. Element#3—Control Flow Rates In order to protect the properties and watenvays downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: • BMP C233: Filter Fabric Fence • BMP C235: Straw Wattles � BMP C120: Temporary or Permanent Seeding Element #-1— I►istall Sediment Controls All stormwater runoff from disturbed area5 shall pass tfu�ou�h au appi�opriate sediment remo�al BMP before leaving the construction site or prior to being discharged to an infiltration facility. The specific BMPs to be used for controlling sediment on this project include: • BMP C233: Filter Fabric Fence • BMP C235: Stra�v R'attles • BVIP C220: Storm Drain Inlet Protection Stoim Drain Inlet Protection�vill be used on the inlet adjacent to the property and the one immediately downstream. In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires a�ray from the site and to minimize«rash off of sediments from adjacent streets in runoff. Element#5—Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: • BMP C120: Temporary and Permanent Seeding • BMP C121: 1�lulching • BMP C123: Plastic Covering The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and unworked for more than 7 days during the dry season(May 1 to September 30) and 2 days during the wet season(October 1 to Apri130). Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. Element#6—Protect Slopes There are no slopes on this project. Element#7— Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. Element#8—Stabilize Channels and Outlets Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. However, there are no critical channels or outlets on-site, thei•efore there in no BMPs need to be implemented. F:Ic�i>>cnt �=�) — (��intr�il Nollutant� All pollutants, including waste mat�i�ial� ai1�i ucm��iitiun debi�i�, tl�at u��ur ui�sitc sliall b�� handled and disposed of in a manner that does not cause contamination of stormwater. G��. housekeeping and preventative measures will be taken to ensure that the site will be kept cle�,�:, well-organized, and free of debris. Element#10—Control Dewatering We don't expect to run into any water on this project. If water is encountered a dewatering plan shall be submitted to the City of Renton for approval prior to any dewatering activities. Element#11—Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance �vith each particular BMP's specifications. Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall event that causes a discharge from the site. If the site becomes inactive, and is temporarily stabilized,the inspection frequency will be reduced to once every month. All temporary erosion and sediment control BMPs shall be removed within 30 days after the final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. Silt Barriers shall be inspected immediately after each rainfall and at least daily during prolonged rainfall. Necessary repairs to barriers or replacement shall be done promptly. Sediment deposits should be removed after each rainfall,they must be removed when the level of deposition reach approximately one-half of the height of the barrier. Any sediment deposits remaining in place after the barrier is no longer required shall be dressed to conform to the existing grade,prepared and seeded. Element#12—Manage the Project This SWPPP shall be retained on-site or within reasonable access to the site. The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a si�ificant effect on the discharge of pollutants to waters of the state. The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven(7) days following the inspection. Element#13—Protect Low Impact Development BMPs Due to the limitations of the site, no LIDs are being proposed. 1��Tinimum Requirement 3: Source Control of Pollution BMP's are shown on the Site P1an/Stormwater Pollution Pre�-ention Plan and include silt fence or straw wattles surrounding the limits of disturbance, as to protect the surrounding properties of I the site. The disturbed soils will be replaced with amended soils as required. The contractor !� should not disturb areas outside the limits of the silt fence or the trees on this property. I�i A construction entrance should be installed at the beginning of the project. All stockpiled soils II left onsite during construction should be covered with visqueen. ', 1��Tinimum Requirement 4: Preservation of l�atural Drainage Svstems and Outfalls `Ve are proposing to connect the do«�nspouts and drive�-ay runoff to the inlet in the street. 1��7inimum Requirement 5: On-site Storm `�'ater Mana�ement Due to site limitations, all stormwater�vill be collected on site and discharge to the storm drain along Williams Avenue S. l�'Iinimum Requirement 6: Runoff Treatment Since the PGIS area is less than 5,000 square feet there is no water quality proposed for said runoff. Minimum Requirement 7: Flow Control The proposed discharge increases the discharge by less than 0.1 cfs and therefore no flow control is required. We will be installing a storm drain system with two catch basins onsite and connecting to the catch basin in the street. Minimum Requirement 8: Wetlands Protection There are no��etlands on-site. Minimum Requirement 9: Operations and Maintenance This project proposes the installation of two catch basins. Maintenance sheets for this item is included in TIR Sectionl0 of this report. BMP List for Contractor C105—Stabilized Construction Entrance 'I C123—Plastic Covering I C233—Filter Fabric Fence C235—Straw Wattles C120—Temporary or Permanent Seeding C121—Mulching C125—Topsoiling C 220—Storm Drain Inlet Protection C151—Concrete Handling C152—Sawcutting and surface Pollution Prevention C153—Material Delivery,Storage Containment Other methods can and should be used if these methods are sufficient. It is the contractors responsibility to ensure the site is maintained, kept clean and does not allow any turbid or contaminated runoff leaves the site. Web date: 12/02/2008 Site Improvement Bond Quantity Worksheet • Existing Future Public Private Quantity Completed Right-of-Way Right of Way Improvements (Bond Reduction)* i &Drainage Facilities Quant. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost GENERALITEMS No. Backfill&Com action-embankment GI-1 $ 5.62 CY Backfill 8 Com action-trench GI-2 $ 8.53 CY Clear/Remove Brush,b hand GI-3 $ 0.36 SY Clearin /Grubbin /Tree Removal GI-4 $ 8,876.16 Acre 0.01 88.76 Excavation-bulk GI-5 $ 1.50 CY Excavation-Trench GI-6 $ 4.06 CY Fencin ,cedar 6'hi h GI-7 $ 18.55 LF Fencin ,chain link,vin coated, 6'hi h GI-8 $ 13.44 LF Fencin ,chain link, ate,vin coated, 2 GI-9 $ 1 271.81 Each Fencin ,s lit rail,3'hi h GI-10 $ 12.12 LF Fill&com act-common barrow GI-11 $ 22.57 CY Fill&com act- ravel base GI-12 $ 25.48 CY Fill&com act-screened to soil GI-13 $ 37.85 CY Gabion, 12"dee ,stone filled mesh GI-14 $ 54.31 SY Gabion, 18"dee ,stone filled mesh GI-15 $ 74.85 SY Gabion,36"dee ,stone filled mesh GI-16 $ 132.48 SY Gradin ,fine,b hand GI-17 $ 2.02 SY Gradin ,fine,with rader GI-18 $ 0.95 SY Monuments,3'lon GI-19 $ 135.13 Each Sensitive Areas Si n GI-20 $ 2.88 Each Soddin , 1"dee ,slo ed round GI-21 $ 7.46 SY Surve in ,line& rade GI-22 $ 788.26 Da Surve in ,lot location/lines GI-23 $ 1,556.64 Acre Traffic control crew 2 fla ers GI-24 $ 85.18 HR Trail,4"chi ed wood GI-25 $ 7.59 SY Trail,4"crushed cinder GI-26 $ 8.33 SY Trail,4"to course GI-27 $ 8.19 SY Wall,retainin ,concrete GI-28 $ 44.16 SF Wall,rocke GI-29 $ 9.49 SF Page 3 of 9 SUBTOTAL 88.76 Unit prices updated: 02/12/02 'KCC 27A authorizes only one bond reduction. Version: 11/26/08 li-wks-sbq.xlsx Report Date: 11/17/2015 Site Improvement Bond Quantity Worksheet Webdate: 12/02/2008, Existing Future Public Private Bond Reduction* , Right-of-way Right of Way Improvements ' &Drainage Facilities Quant. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost ROADIMPROVEMENT No. AC Grindin ,4'wide machine<1000s RI-1 $ 28.00 SY AC Grindin ,4'wide machine 1000-200 RI-2 $ 15.00 SY AC Grindin ,4'wide machine>2000s RI-3 $ 7.00 SY AC Removal/Dis osal/Re air RI-4 $ 67.50 SY Barricade,t e I RI-5 $ 30.03 LF Barricade,t e III Permanent RI-6 $ 45.05 LF Curb&Gutter,rolled RI-7 $ 17.00 LF Curb&Gutter,vertical RI-8 $ 12.50 LF 24 300.00 Curb and Gutter,demolition and dis osal RI-9 $ 18.00 LF 24 432.00 Curb,e�ruded as halt RI-10 $ 5.50 LF Curb,extruded concrete RI-11 $ 7.00 LF Sawcut,as halt,3"de th RI-12 $ 1.85 LF Sawcut,concrete, er 1"de th RI-13 $ 1.69 LF Sealant,as halt RI-14 $ 1.25 LF Shoulder,AC, see AC road unit rice RI-15 $ - SY Shoulder, ravel,4"thick RI-16 $ 15.00 SY Sidewalk,4"thick RI-17 $ 35.00 SY 228 7,980.00 Sidewalk,4"thick,demolition and dis os RI-18 $ 29.50 SY 300 8,850.00 Sidewalk,5"thick RI-19 $ 38.50 SY Sidewalk,5"thick,demolition and dis os RI-20 $ 37.50 SY Si n,handica RI-21 $ 85.28 Each Stri in , er stall RI-22 $ 5.82 Each Stri in ,thermo lastic, for crosswalk RI-23 $ 2.38 SF Stri in ,4"reflectorized line RI-24 $ 0.25 LF Page 4 of 9 SUBTOTAL 17,562.00 Unit prices updated: 02/12/02 'KCC 27A authorizes only one bond reduction. Version: 11/26/08 li-wks-sbq.xlsx Report Date: 11/17/2015� Site Improvement Bond Quantity Worksheet Webdate: 12/02/2008. , Existing Future Public Private Bond Reduction* I Right-of-way Right of Way Improvements I &Drainage Facilities Quant. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost ROAD SURFACING (4"Rock=2.5 base 8�1.5"top course) For'93 KCRS(6.5"Rock=5"base 8�1.5"top course) For KCRS'93, additional 2.5"base add RS-1 $ 3.60 SY AC Overla , 1.5"AC RS-2 $ 11.25 SY AC Overla ,2"AC RS-3 $ 15.00 SY AC Road,2",4"rock,First 2500 SY RS-4 $ 21.00 SY AC Road,2",4"rock,Qt .over 2500SY RS-5 $ 19.00 SY AC Road,3" 4"rock,First 2500 SY RS-6 $ 23.30 SY AC Road,3",4"rock,Qt .over 2500 SY RS-7 $ 21.00 SY AC Road,5",First 2500 SY RS-8 $ 27.60 SY AC Road,5",Qt .Over 2500 SY RS-9 $ 25.00 SY AC Road,6",First 2500 SY S-1 $ 33.10 SY AC Road,6",Qt .Over 2500 SY S-1 $ 30.00 SY As halt Treated Base,4"thick S-1 $ 20.00 SY Gravel Road,4"rock,First 2500 SY S-1 $ 15.00 SY Gravel Road,4"rock,Qt .over 2500 SY S-1 $ 8.50 SY PCC Road,5",no base,over 2500 SY S-1 $ 27.00 SY 120 3,240.00 PCC Road, 6" no base,over 2500 SY S-1 $ 25.50 SY Thickened Ed e S-1 $ 8.60 LF Page 5 of 9 SUBTOTAL 3,240.00 Unit prices updated: 02/12/02 "KCC 27A authorizes only one bond reduction. VersiOn: 11/26/08 li-wks-sbq.xlsx Report Date: 11/17/2015 Site Improvement Bond Quantity Worksheet Webdate 12/02I2008. , Existing Future Public Private Bond Reduction* Right-of-way Right of Way Improvements 8�Draina e Facilities Quant. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost DRAINAGE (CPP=Corrugated Plastic Pipe,N12 or Equivalent) For Culvert rices, Avera e of 4'cover was assumed.Assume erforated PVC is same rice as solid i e. Access Road,R/D D-1 $ 21.00 SY Bollards-fixed D-2 $ 240.74 Each Bollards-removable D-3 $ 452.34 Each " CBs include frame and lid CB T e I D-4 $ 1,257.64 Each CB T e IL D-5 $ 1,433.59 Each CB T e II,48"diameter D-6 $ 2,033.57 Each for additional de th over 4' D-7 $ 436.52 FT CB T e II,54"diameter D-8 $ 2,192.54 Each for additional de th over 4' D-9 $ 486.53 FT CB T e II,60"diameter D-10 $ 2,351.52 Each for additional de th over 4' D-11 $ 536.54 FT ; CB T e II,72"diameter D-12 $ 3,212.64 Each for additional de th over 4' D-13 $ 692.21 FT Throu h-curb Inlet Framework Add D-14 $ 366.09 Each Cleanout,PVC 4" D-15 $ 130.55 Each Cleanout,PVC,6" D-16 $ 174.90 Each Cleanout,PVC,8" D-17 $ 224.19 Each Culvert,PVC,4" D-18 $ 8.64 LF Culvert,PVC,6" D-19 $ 12.60 LF Culvert,PVC, 8" D-20 $ 13.33 LF Culvert, PVC, 12" D-21 $ 21.77 LF Culvert,CMP,8" D-22 $ 17.25 LF Culvert,CMP, 12" D-23 $ 26.45 LF Culvert,CMP, 15" D-24 $ 32.73 LF Culvert,CMP, 18" D-25 $ 37.74 LF Culvert,CMP,24" D-26 $ 53.33 LF Culvert,CMP,30" D-27 $ 71.45 LF Culvert,CMP,36" D-28 $ 112.11 LF Culvert,CMP,48" D-29 $ 140.83 LF Culvert,CMP,60" D-30 $ 235.45 LF Culvert,CMP,72" D-31 $ 302.58 LF Page 6 of 9 SUBTOTAL Unit prices updated: 02/12/02 `KCC 27A authorizes only one bond reduclion. Version: 11/26/08 li-wks-sbq.xlsx Report Date: 11/17/2015 _ — —� Site Improvement Bond Quantity Worksheet Webdate: 12/02/200II, Existing Future Public Private Bond Reduction* Right-of-way Right of Way Improvements DRAINAGE CONTINUED 8�Drainage Facilities Quant. No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost Culvert,Concrete,8" D-32 $ 21.02 LF 10 210.2 Culvert,Concrete, 12" D-33 $ 30.05 LF Culvert,Concrete, 15" D-34 $ 37.34 LF Culvert,Concrete, 18" D-35 $ 44.51 LF Culvert,Concrete,24" D-36 $ 61.07 LF Culvert,Concrete,30" D-37 $ 104.18 LF Culvert,Concrete,36" D-38 $ 137.63 LF Culvert,Concrete,42" D-39 $ 158.42 LF Culvert,Concrete,48" D-40 $ 175.94 LF Culvert,CPP,6" D-41 $ 10.70 LF Culvert,CPP,8" D-42 $ 16.10 LF Culvert,CPP, 12" D-43 $ 20.70 LF Culvert,CPP, 15" D-44 $ 23.00 LF Culvert,CPP, 18" D-45 $ 27.60 LF Culvert,CPP,24" D-46 $ 36.80 LF Culvert,CPP,30" D-47 $ 48.30 LF Culvert,CPP,36" D-48 $ 55.20 LF Ditchin D-49 $ 8.08 CY Flow Dis ersal Trench 1,436 base+ D-50 $ 25.99 LF French Drain 3'de th D-51 $ 22.60 LF Geotextile,laid in trench, ol ro lene D-52 $ 2.40 SY Infiltration ond testin D-53 $ 74.75 HR Mid-tank Access Riser,48"dia, 6'dee D-54 $ 1,605.40 Each Pond Overflow S illwa D-55 $ 14.01 SY Restrictor/Oil Se arator, 12" D-56 $ 1,045.19 Each Restrictor/Oil Se arator, 15" D-57 $ 1,095.56 Each Restrictor/Oil Se arator, 18" D-58 $ 1,146.16 Each Ri ra , laced D-59 $ 39.08 CY Tank End Reducer 36"diameter D-60 $ 1,000.50 Each Trash Rack, 12" D-61 $ 211.97 Each Trash Rack, 15" D-62 $ 237.27 Each Trash Rack, 18" D-63 $ 268.89 Each Trash Rack,21" D-64 $ 306.84 Each Page 7 of 9 SUBTOTAL 210.2 Unit prices updated: 02/12/02 *KCC 27A authorizes only one bond reduction. Version: 11/26/08 li-wks-sbq.xlsx Report Date: 11/17/2015 Site Improvement Bond Quantity Worksheet Webdate: 12/02/2008. , Existing Future Public Private Bond Reduction* Right-of-way Right of Way Improvements &Drainage Facilities Quant. Unit Price Unit Quant. Price Quant. Cost Quant. Cost Complete Cost PARKING LOT SURFACING No. 2"AC,2"to course rock&4"borrow PL-1 $ 21.00 SY 2"AC, 1.5" to course&2.5"base cou PL-2 $ 28.00 SY 4"select borrow PL-3 $ 4.55 SY 1.5"to course rock 8�2.5"base course PL-4 $ 11.41 SY UTILITY POLES & STREET LIGHTING Utility pole relocation costs must be accompanied by Franchise Utility's Cost Statement Utility Pole(s)Relocation UP-1 Lum Sum Street Li ht Poles w/Luminaires UP-2 Each WRITE-IN-ITEMS Such as detention/water ualit vaults. No• Culvert, DI,6" WI-1 $ 29.90 LF 19 568.1 Reducer, DI, 10"x 6" W I-2 $ 129.89 Each 1 129.89 Gate Valve,6" WI-3 $ 861.61 Each 1 861.61 22 1/2 De ree Bend, DI,6" WI-4 $ 88.56 Each 1 88.56 Gland Packs, 10" WI-5 $ 27.54 Each 1 27.54 Gland Packs,6" WI-6 $ 27.36 Each 5 136.8 WI-7 WI-8 WI-9 wi-io SUBTOTAL 1,812.50 SUBTOTAL(SUM ALL PAGES): 22,913.46 30%CONTINGENCY 8�MOBILIZATION: 6,874.04 GRANDTOTAL: 29,787.50 COLUMN: B C D E Page 8 of 9 Unit prices updated: 02/12/02 *KCC 27A authorizes only one bond reduction. Version: 11/26/08 li-wks-sbq.xisx Report Date: 11/17/2015 � TIR Section 10: Operations and Maintenance Manual Operations and Maintenance for the two catch basins in the driveway shall follow the procedures outlined in the King County Surface Water Deign Manual for catch basins and manholes. Section No. 5 for catch basins and manholes and Section No. 6 for conveyance pipes have been included. APPEI�DIl A MAINTENAI�CE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 5-CATCH BASINS AND MANHOLES Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Stn�cture Sediment Sediment exceeds 60°�of the depth from the Sump of catch basin contains no bottom of the catch basin to the invert of the sediment. lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Trash and debris Trash or debris of more than%cubic foot which No Trash or debris blocking or is located immediately in front of the catch basin potentially blocking entrance to opening or is blocking capacity of the catch basin catch basin. by more than 10%. Trash or debris in the catch basin that exceeds No trash or debris in the catch basin. '!3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. Dead animals or vegetation that could generate No dead animals or vegetation odors that could cause complaints or dangerous present within catch basin. gases(e.g.,methane). Deposits of garbage exceeding 1 cubic foot in No condition present which would �olume. attract or support the breeding of insects or rodents. Damage to frame Corner of frame extends more than'/.inch past Frame is even with curb. and/or top siab 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. I cracks wider than'/.inch. ; Frame not sitting flush on top slab,i.e., Frame is sitting flush on top slab. separation of more than'/<inch of the frame from the top slab. � Cracks in walls or Cracks wider than Yz inch and longer than 3 feet, Catch basin is sealed and bottom any evidence of soil particles entering catch structurally sound. basin through cracks,or maintenance person judges that catch basin is unsound. Cracks wider than Y=inch and longer than 1 foot No cracks more than'/4 inch wide at at the joint of any inleUoutlet pipe or any evidence the joint of inleUoutlet pipe. of soil particles entering catch basin through cracks. ' SettlemenU Catch basin has settled more than 1 inch or has Basin replaced or repaired to design , misalignment rotated more than 2 inches out of alignment. standards. Damaged pipe joints Cracks wider than Yz-inch at the joint of the No cracks more than'/.-inch wide at inleUoutlet pipes or any evidence of soil entering the joint of inleUoutlet pipes. the catch basin at the joint of the inlet/outlet pipes. Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil,gasoline,concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. InIeUOutlet Pipe Sediment Sediment filling 20%or more of the pipe. InleUoutlet pipes clear of sediment. accumulation Trash and debris Trash and debris accumulated in inleUoutlet No trash or debris in pipes. pipes(includes floatables and non-floatables). Damaged Cracks wider than'/rinch at the joint of the No cracks more than Y.-inch wide at inleUoutlet pipes or any evidence of soil entering the joint of the inleUoutlet pipe. at the joints of the inleUoutlet pipes. 2009 Surface`�'ater Design 1�lanual—Appendix A 1!9�'2009 A-9 APPENDIX A MAINTENANCE REQUIREMENTS FLOVJ COIvTTROL,CONVEYANCE,AND WQ FACILITIES Y NO. 5-CATCH BASINS AND MANHOLES I�� Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Metal Grates Unsafe grate opening Grate with opening wider than'/8 inch. Grate opening meets design (Catch Basins) standards. Trash and debris Trash and debris that is blocking more than 20% Grate free of trash and debris. of grate surFace. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s)of the grate. Grate is in place and meets design Any open structure requires urgent standards. maintenance. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Coverllid protects opening to Any open structure requires urgent structure. maintenance. Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. Not Working maintenance person with proper tools.Bolts cannot be seated. Self-locking covedlid does not work. Cover/lid difficult to One maintenance person cannot remove Coverllid can be removed and Remove covedlid after applying 80 Ibs.of lift. reinstalled by one maintenance person. 1/9i2009 2009 Surface��`ater Desian Manual—Appendix A '' A-10 � APPEtiDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES ' � NO. 6-CONVEYANCE PIPES AND DITCHES Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed ' Pipes Sediment&debris Accumulated sediment or debris that exceeds Water flows freely through pipes. accumulation 20%of the diameter of the pipe. Vegetation/roots Vegetation/roots that reduce free movement of Water flows freely through pipes. water through pipes. I Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of I pollution as oil,gasoline,concrete slurries or paint. according to applicable regulations. I Source control BMPs implemented if I appropriate. No contaminants � present other than a surface oil film. li Damage to protective Protective coating is damaged;rust or corrosion Pipe repaired or replaced. �', coating or corrosion is weakening the structural integrity of any part of ' pipe. Damaged Any dent that decreases the cross section area of Pipe repaired or replaced. I pipe by more than 20%or is determined to have �, weakened structural integnty of the pipe. I Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris Geared from ! square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20%of the Ditch cleaned/flushed of all sediment accumulation design depth. and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation constitute a hazard to County personnel or the removed according to applicable public. regulations. No danger of noxious vegetation where County personnel or the public might normally be, i Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of pollution as oil,gasoline,concrete slurries or paint. according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water Water flows freely through ditches. through ditches. Erosion damage to Any erosion observed on a ditch slope. Slopes are not eroding. slopes Rock lining out of One layer or less of rock exists above native soil Replace rocks to design standards. place or missing(If area 5 square feet or more,any exposed native Applicable) soil. 2009 Surface Water Design I�lanual—Appendix A 1/9/2009 A-11 r � 1 GeoResources, LLC Ph 2�3-896-1011 5007 Pacific H�vy E.,Ste. 16 Fx 2�3-896-2633 Fife, Washington 98424 April 30, 2015 Mr. Joe Bernasconi (253) 740-2119 joebC�3windermere.com Geotechnical Infiltration Letter Proposed Residential Develop 520 Williams Ave S Renton, Washington 98057 R��iv�d P b No 52ow�4amsaves. J�N �8 2015 �v� � la�m��t S��'Ice INTRODUCTION & SCOPE S This letter provides the results of our subsurface explorations and geotechnical analysis regarding potential stormwater infiltration for the residence to be located at 520 Williams Avenue South in Renton, Washington (the City) as shown in Figure 1. We understand that you plan to infiltrate the collected stormwater from proposed impervious areas, where feasible. The City uses the 2009 King County Stormwater Design Manual (KCSDM), which requires soil logs to confirm subsurface conditions and to determine the feasibility of stormwater infiltration at the site. On April 27, 2015, we excavated two hand auger explorations and logged the subsurface conditions encountered. Representative soil samples were collected and transported to our laboratory for further testing as required. The purpose of our services was to evaluate the surface and subsurface conditions at the site as a basis for developing and providing geotechnical stormwater recommendations for the proposed development. Specifically, our scope of services for the project included the following: 1. Visiting the site and conducting a geologic reconnaissance to assess the site's soil, groundwater and slope conditions; 2. Exploring the subsurface conditions across the site by excavating hand auger holes at the locations of the proposed infiltration areas; 3. Providing infiltration rates for the proposed stormwater facilities, as appropriate. SITE CONDITIONS Surface Conditions The site is located in an area of existing residential development in the downtown portion of Renton, Washington. The site is currently developed with a single family residence, partial concrete driveway, and existing foundations and piping from previous onsite structures. The site is generally rectangular in shape, measuring approximately 120 feet east to west by 50 feet north to south and encompassing approximately 0.14 acres. The ground surface on most of the site is flat with areas east of the residence having slightly lower elevations due to previous construction and demolition on site. The existing site layout is provided in Figure 2. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey for King County maps the soils in the area of the site as Urban Land (Ur). These soils are t � II 520WilliamsAveS.RH I� April 30,2015 � Page 2 characterized by alterations from human activity. Urban land soils are associated with built environments of urban areas, encompassing large areas completely covered by ' impervious surfaces such as asphalt, concrete, or rooftop. An excerpt from the map is included as Figure 3. Site Geology The Geotogic Map of the Renton 7.5-minute Quadrangle, King County, Washington by D.R, Mullineaux, 1965 indicates the site is situated in an area of urban or industrial land modified by widespread or discontinuous artificial fill (afm). These soils were generally reworked and artificially backfilled during the urbanization of the area. An excerpt from the geologic map is included at Figure 4. Subsurface Conditions Subsurface conditions were evafuated by advancing two hand augers across the site. Our explorations generalfy encountered 0.5 foot of topsoil over various layers af ' brown sand with silt in a loose or medium dense condition to full depth explored. We interpret these soils to represent the modified fill. HA-2 encountered red coarse sand with heavy oxidation at approximatedly 5 feet. Below a depth of 4.5 to 5 feet, our explorations encountered wet soil conditions and groundwater seepage. The locations of our explorations are included on the Site Plan as Figure 2. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS), a copy of which is included as Figure 5. The Hand Auger Logs are included as Figure 6. Groundwater Conditions Groundwater was encountered in all of the hand augers at a depth of about 4.5 feet below the existing grades. Based on the nature of the near surface soils, and evidence of mottled zones in the soils representative of seasonal perched groundwater, we anticipate fluctuations in the local groundwater levels will occur in response to precipitation patterns, �I general development in the area and site utilization. I CONCLUSIONS AND RECOMMENDATIONS I�I Based on soil and groundwater conditions encountered in our subsurface ', exploration, it is our opinion that infiltration of stormwater is not feasible in the shallow on- ', site soils per the 2009 KCSDM. It is not typically appropriate to infiltrate stormwater in fill. i We recommend that the stormwater from impervious surfaces on the site be collected and conveyed to an appropriate discharge point, such as the City's storm system. Specific geotechnical recommendations for earthwork and building development may be provided upon request. ♦ ♦ ♦ � 520WilliamsAveS.RH April 30,2015 Page 3 We trust this is sufficient for your current needs. Should you have any questions, or require additional information, please contact us at your earliest convenience. Respectfully submitted, GeoResources, LLC / ��iZ�� `�'`� Dustin R. Taylor, EIT Engineer-in-Training h q �ppHER 8l i ��o��cCC� C �b�'� �c zzze �, •� p,, �PE,��g �,�v� � e e eo �fOlyAI, E�� BRA EY P.BIGGERSTAFF 3`� ��30��r S Brad P. Biggerstaff, LHG Dana C. Biggerstaff, PE Principal Senior Geotechnical Engineer DRT$PB.stm OocID�520V'1dLamsAveS IR Attachmenis Figure 1.Site Location A�lap Figure 2 Site and E:ploraaon Plar Fiyure 3:NRCS SCS Sals Map Figwe 4:USGS Geologic Map Figure 5:Unified Soi passificauo�,Sysie�•�. F�gure 6�Nand Auger Excavaua��s s��z„�u rrro i�a x � s r�i��:�„� o u y�a� N 2M St - - - � J a ,�, �� j v� �'9� � Qd�f i �;v: sJ. ' Renton � �� a JYtcr.��Z � ion_. ,2ty�� ._ St3.1�pi . �� ; F�ar^ •J� Llterty $s �cd3 �� .. - � � ��v: $: a 'n � Park. 4 �kr:�r F . . 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I << �, /" - `— . i� _ �' i � :.,-- u: • . -_ 1� _ !` `. �• .r � i � Q � —�� .�' : � ' / ' . � ! 1 �r�F� ��, .' .�,i�f��-4' � '.a� � t� � ' _ t ��,y.``�."G�';..�� z-�_,f-"''� + t s\- •>:„� I� Y' l� .�r� j�• � ��> ��L`�: :-'�ii,_ . �`�- t ' . . - , , ' `}}� ,� .�_ � �� \i�y c _ . .J 'l� � y \� ��i� # ;� r � ` � � 1....�, i %k;r ., ..--� �, t ,.�_ ' . \ .8M - I' � ' S'�n'1� �� t •� __- • � af � � ;� .� - �:i=�JJ, y , - �,�. .i -_ � . � . _ /� �- �(.s' __._� - � .�- - >. _ � _ _" _ � ' .. _ ._. ` _�`-y --- 1 � ;," —;' /J�� "' �, :� / �_ �� . . .F i- �� : r ,},/ Ji'�I K •�• • • / —` /�� --�-- -`� _' • ... .♦ �t��''y':i�-,-r �,� ... �-_X, - ) � f�� 5 � :.. l��') •,� l'' �+�� .� ��\•��•-- -�. �� '' . �i � 1 i� �. .� — \ 8C - -�-. �`: � . � ��F,.. _ _ � �"��,��,�;'':�.1 ��'�i��i . Qik ; g =. � � _ �� ,; . . -- f-�, '1 �!]�1' �\-._ '_ � _ ^ �_ �.. . - ___=-�. - : ��:�� ' �,.a �i � •�• -- Approximate Site Location Excerpt of Geologic Map of the Renton 7.5-minute Quadrangle,King County, Washington by D.R. Mullineaux 1965 afm Urban or industrial land modified by widespread or discontinuous artificial fill �� .��.��t: � Not to Scale GeoResources, LLC USGS Geologic Map 5007 Pacific Highway East, Suite 16 Single Family ReSidenCe Fife, Washington 98424 520 Williams Ave S Phone: 253-896-1011 Renton, WA Fax: 253-896-2633 Job:520WilliamsAveS.F April 2015 Figure 4 � • , SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP GROUP NAME SYMB�L GRAVEL CLEAN GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL GRAVEL COARSE GP POORLY-GRADED GRAVEL GRAINED More than 50% SOILS Of Coarse Fraction GRAVEL GM SILTY GRAVEL Retained on WITH FINES j No.4 Sieve � GC CLAYEY GRAVEL IMore than 50% SAND CLEAN SAND SW WELL-GRADED SAND,FINE TO COARSE SAND Retained on No.200 Sieve SP POORLY-GRADED SAND More than 50°/a Of Coarse Fraction SAND SM SILTY SAND Passes W1TH FINES No.4 Sieve SC CLAYEY SAND SILT AND CLAY INORGANIC ML SILT FINE I GRAINED CL CLAY SOILS Liquid Limit ' Less than 50 ORGANIC OL ORGANIC SILT,ORGANIC CLAY SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY,ELASTIC SILT More than 50% Passes CH CLAY OF HIGH PLASTICITY,FAT CLAY No.200 Sieve Liquid Limit 50 or more ORGANIC OH ORGANIC CLAY,ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS: 1. Field classification is based on visual examination of soil Dry- Absence of moisture,dry to the touch in general accordance with ASTM D248&90. Moist• Damp,but no visible water 2. Soil class'rfica!ion using laboratory tests is based on ASTM D2487-90. Wet- Visible free water or saturated,usually soii is obtained from below water table 3. Description of soil density or consistency are based on interpretation of blow count data,visual appearance of soils,and or test data. GeoResources, LLC Soil Classification System 5007 Pacific Highway East, Suite 16 Single Family Residence Fife, Washington 98424 520 WilliamS Ave S Phone: 253-896-1011 Renton, WA Fax: 253-896-2633 DocID:EvansR.SESedgewickRd.F Aprll 2015 Figure 5 � I Hand A r HA-1 II uge , Location: NE portion of site i Depth (feet) Soil Type Soil Description II 0 - 0.5 Grass roots,Topsoil 0.5 - 1.5 SM Brown SAND with silt and organics(loose, moist) 1.5 - 2,0 SM Brown/light brown SAND with silt (loose, moist} 2.0 - 3.0 SM Brown silty SAND lightly oxidized (medium dense, moist} 3.0 - 3,5 ML Brown fine silty SAND with clay, oxidized (medium dense, moist) 3.5 - 5.5 ML Brown fine silty SAND with clay and tan mottled zone, oxidized (medium dense, wet) No caving observed. Groundwater seepage observed at 4�h feet. Hand Auger HA-2 Location:Western Center portion of site Depth (feet) Soil Type Soil Description 0 - 0.5 Grass roots,Topsoil 0.5 - 1.3 SP Brown SAND with roots and organics {loose,moist) 1.3 - 2.5 SP Brown coarse SAND(loose, moist) 2.5 - 4.0 SM Brown SAND with silt(medium dense, moist) 4.0 - 4.5 ML Brown SAND with silt, lightly oxidized (medium dense,wet) 4.5 - 5.5 ML Brown SAND grading to red coarse sand, heavily oxidized(medium dense, wet) No caving observed. Groundwater seepage observed at 4��z feet. Lo ed b : DRT Excavated on:A ril 27,2015 GeoResources, LLC Hand Auger Excavations 5007 Pacific Highway East, Suite 16 Single Family ResidenCe Fife,Washington 98424 520 WilliamS Ave S Phone: 253-896-1011 Renton,WA Fax: 253-896-2633 DocID:520WIIIIamsAveS.F April 2015 Figure 6