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Home My WebLink AboutMISCEncompass~ ENGINEERING & SUtVEYING ~ PRELIMINARY TECHNICAL INFORMATION REPORT For Dylan Short Plat 1909 Jones Avenue NE Renton, WA 98056 September 2, 2016 Encompass Engineering Job No. 16576 Prepared For Neault Homes P.O. Box 2230 Issaquah, WA 98027 Western Washington Division Eastern Washington Division 165 NE Juniper St.. Ste 20 I, Issaquah, WA 98027 407 Swiftwater Blvd. , Cle Elum, WA 98922 Phone (425) 392-0250 Fax: (425) 391-3055 Phone (509) 674-7433 Fax (509) 674-7419 www.EncompassES.net r1gure l KING COUNTY, WASilINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner Neault Homes Phone-----------~ Address P.O. Box 2230 Issaquah, WA 98027 , Project Engineer Jae Kim PE Company Encompass Enginee1ing & Surveying Phone 425-392-0250 Part 3 TYPE OF PERMIT APPLICATION (SI Landuse.~ Subdivison /~ UPD 0 Building Services M/F / Commerical I SFR IEl Clearing and Grading 0 Right-of-Way Use 0 Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review (@; Targeted (circle): Large Site Date (include revision dates): I Date of Final: Part 6 ADJUSTMENT APPROVALS I Part 2 PROJECT LOCATION AND DESCRIPTION Project Name Dylan Short Plat DDES Permit# _________ _ Location Township ....c2:::3:..cN.:..._ __ _ Range 5E Section _ __:5:.._ ___ _ Site Address 1909 Jones Avenue NE Renton. WA 98056 Part 4 OTHER REVIEWS AND PERMITS D DFWHPA · 0 COE404 0 DOE Dam Safety 0 FEMA Floodplain D COE Wetlands 0 Other __ _ D Shoreline Management D Structural RockeryNault/ __ D ESA Section 7 Site Improvement Plan (Engr. Plans) Type (circle one): @1 Modified I Small Site Date (include revision dates): Date of Final: Type (circle one): ~ Complex I Preapplication / Experimental/ Blanket Description: (include conditions in Tl R Section 2) Date of Annroval: 2009 Surface Water Design Manual I 1/9/2009 I KING COUNTY, WASHINGTO"I, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT {TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes,® Describe: Start Date: NIA Completion Date: Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : Green River Valley Special District Overlays: __ N~/,A~--------------------- Drainage Basin: East Lake Washington -Renton Stormwater Requirements: ----------------------- Part 9 ONSITE AND ADJACENT SENSITIVE AREAS D River/Stream _________ _ D Lake . D Wetlands __________ _ D Closed Depression -------- D Floodplain __________ _ D Other ____________ _ Part 10 SOILS D Steep Slope ________ _ D Erosion Hazard _______ _ Iii Landslide Hazard very small portion on D Coal Mine Hazard northwest corner D Seismic Hazard _______ _ D Habitat Protection _______ _ D ___________ _ Soil Type QvT Slopes Erosion Potential Low to Moderate D High Groundwater Table (within 5 feet) D Other _________ _ D Additional Sheets Attached 2009 Surface Water Design Manual 5 to 10 percent 2 D Sole Source Aquifer D Seeps/Springs 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION/ SITE CONSTRAINT 0 Core 2-Offsite Analtsis lil Sensitive/Critical Areas Wellhead Protection Area (zone '.2) 0 SEPA 0 Other 0 0 Additional Sheets Attached Part 12 TIR SUMMARY SHEET /nrovide one TIR Summarv Sheet ner Threshold Discharae Areal Threshold Discharge Area: (name or description) ! Core Requirements (all 8 apply) Discharge at Natural Location Offsite Analysis Flow Control (incl. facility summary sheet) Conveyance System Erosion and Sediment Control Maintenance and Operation Financial Guarantees and Liabilit Water Quality (include facility summary sheet) Area Specific Drainage Re uirements licable Floodplain/Floodway Delineation Flood Protection Facilities Source Control (comm./industrial landuse) 2009 Surface Water Design Manual TDA-1 Number of Natural Discharae Locations: 2 Level: (__2J) 2 I 3 dated: Level: 1 / 2 / 3 or Exemption Number Small Site BMPsSolash blocks and Gravel Filled Trenches Spill containment located at: ESC Site Supervisor: TBD Contact Phone: After Hours Pho e n Responsibility: @§B5 t Public If Private, Maintenance L Re Yes Provided: Yes / No By Owner Type: Basic / Sens. Lake / Enhanced Basicm / Bog or Exemption No. ---------- No Type: CDA / SDO /MOP/ BP/ LMP I Shared Fae. / None Name: NA Type: Major / Minor / Exemption I None 100-year Base Flood Elevation (or range): Datum: Describe: N/A Describe landuse: "I/A Describe any structural controls: 3 NIA 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes /(No ) Treatment BMP: NIA - Maintenance Agreement: Yes /~ with whom? Other Draina11e Structures Describe: NIA Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION @ Clearing Limits ~ Stabilize Exposed Surfaces [8) Cover Measures lEI Remove and Restore Temporary ESC Facilities [8) Perimeter Protection D Clean and Remove All Silt and Debris, Ensure 0 Traffic Area Stabilization Operation of Permanent Facilities 1 0 Sediment Retention 0 Flag Limits of SAO and open space D Surface Water Collection preservation areas ! 0 Other D Dewatering Control ' I 0 Dust Control 0 Flow Control Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facilitv Summarv and Sketch) Flow Control Tvoe/Description Water Quality Type/Description 0 Detention 0 Biofiltration ! I D Infiltration 0 Wetpool ' 0 Regional Facility D Media Filtration 0 Shared Facility D Oil Control [8) Flow Control Splash Blocks and 0 Spill Control Gravel Filled trenches BMPs D Flow Control BMPs D Other D Other I i 2009 Surface Water Design Manual 4 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTSfTRACTS Part 16 STRUCTURAL ANALYSIS 0 Drainage Easement D Cast in Place Vault D Covenant D Retaining Wall D Native Growth Protection Covenant D Rockery > 4' High [I Tract D Structural on Steep Slope D Other D 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 inforr ation provided here is accurate. -A ' q.z..,i. --, . L...~ V Siqned!Date 2009 Surface Water Design Manual 1/9/2009 5 Dylan Short Plat Preliminary Technical Infonnation Report TABLE OF CONTENTS I. Project Overview ................................•.......•...•....•.................. Page l Location A1ap II. Conditions and Requirements Summary ....................................... Page 2 III. Off-Site Analysis .................................................................... Page 3-4 Do,.,rnslream Drainage l'vfap Sile Photos Phow Locatwn 1'vfap IV. Flow Control and Water Quality Facility Analysis and Design ........... Page 5 V. Conveyance System Analysis and Design .................•..................... Page 5 VI. Special Reports and Studies ...................................................... Page 6 VII. Other Permits ........................................................................ Page 6 VIII. TESC Analysis and Design ....................................................... Page 6-8 IX. Bond Quantities and Declaration of Covenant .................................. Page 8 X. Operation and Maintenance Manual. ............................................ Page 8 APPENDICES A. Drainage Area Calculations, KRCTS Input and Output B. Geotechnical Report .L- ·e 10 ( ()/7 The r,format1or ncUded on lhis Tap has b een ccmpled b,' Kng County staff from a vanetv of sources and iS subject to d'lange wU1out notice K1119 Cou nty makes no representatons or ,...,arra1t1es. e:ii;press or i moied, ffi to aa;uracy, completeness. tl'neli-iess. o r rghls to t h:! use o f suchinforrnat101 Tlis cbcvrner1t1s 10 1 inte nderJ br use as a survey oroouct. KJng Cownty soa l rt:lt be l iabl e fa an-,, general, special. ndired.. inadenta l. or co nseq uential oariagas 1ndudin9. ~ut na: limrnd 10. bst r1h'er,ues or bs1 ;:irons resJhi ng from !he use o~ misuse ct the nforma ltin ccnlained on this map. Ai1y sale of ths map or informalicn on thi s map is proh ibtec except by wnten pemi.1ss100 of K1rg County Date: 7129/20 16 Parcel 334450 -0120 l,'1 King County GISCENTER I I I I I I Dylan Short Plat Preliminary Technical Information Report Site Address King County Tax Parcel: I 909 Jones Avenue NE, Renton WA, 98056 334450-0120 I. PROJECT OVERVIEW This project proposes to subdivide a 0.53-acre parcel into two single-family residential lots and a shared driveway tract. The site is bound by single-family residential homes to the north, south, Jones Avenue to the east, and Interstate 405 to the west. Currently, there is an existing house on the site and the house will remain in the western lot (lot I) The site generally slopes to the south and southwest at approximately 5 to IO percent. There are rockery walls ranging from 2 to 4 feet along northern and southern property lines. The soil of the site is mapped as Glacial Till (Qvt) per the Preliminary Geotechnical Report by Ages Engineering, LLC. Proposed Drainage Controls The site storm drainage system has been designed according to the standards set forth by the 2009 King County Surface Water Design Manual (KCSWDM) and as amended by the City of Renton. The total impervious area created for Lot 2 and the shared driveway is approximately 6,185 sf (See Area Calculations in the Appendix A). Since the project creates more than 5,000 sf of impervious area, Full Drainage Review is required. Flow control facility will not be required since the project doesn't generate O 1-cfs increase in the existing site conditions I 00-year peak flow. Basic flow control BMP will be utilized for the proposed lot The project is exempt from the water quality requirement since it generates less than 5,000 sf of new pollution generating impervious surface (PGIS). II. CONDITIONS AND REQUIREMENTS SUMMARY CORE REQUIREMENTS Core Requirement #1: Discharge at the natural Location The western portion of the site drains to south and southwest comer of the property. The existing house and the frontage drains out to Jones Avenue NE. The development of proposed lot will follow the existing ground and will maintain the natural discharging location. Core Requirement #2: Offsite Analysis An offsite drainage analysis is provided in Section 3 of this TIR. Level I Drainage Analysis has been prepared and no problems identified. September 20 l 6 Pagel Dylan Short Plat Preliminary Technical Information Report Core Requirement #3: Flow Control Flow control facility is not required since the project does not generate 0.1-cfs increase in the existing site conditions 100-year peak flow per the City of Renton Amendments to the King County Surface Water Design Manual Section 1.23.1.A. Basic flow control BMP will be utilized for the proposed lot Core Requirement #4: Conveyance System Conveyance system analysis is not required for the project. Core Requirement #5: Erosion and Sediment Control A temporary erosion and sediment control (TESC) plan will be submitted in final engineering and those BMP' s will be implemented during construction. Core Requirement #6: Maintenance and Operations Operation and Maintenance Manual will be provided in final engineering. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. Core Requirement #8: Water Quality Water Quality is not required since the project creates less than 5,000 sfofPGIS. SPECIAL REQUIREMENTS: Special Requirement #1: Other Adopted Area-Specific Requirements Critical Drainage Area -N/ A Master Drainage Plan -NIA Basin Plan -N/A Lake management Plan -N/ A Shared Facility Drainage Plan -N/ A Special Requirement #2: Floodplain/Floodway Delineation The limits of this project do not lie in a I 00-year floodplain. September 2016 Page 2 Dylan Short Plat Preliminary Technical Information Report Special Requirement #3: Flood Protection Facilities This site does not contain any Class I or 2 streams; therefore, flood protection facilities are not applicable. Special Requirement #4: Source controls This project is a 2-lot single-family residential project and this requirement is not applicable. Special Requirement #5: Oil Control This project is not considered high-use in need of oil control. Special Requirement #6: Aquifer Protection Area This project is located in a Wellhead Protection Area Zone 2; therefore, for the proposed open facilities or conveyance system will require a liner per 1.3.6 of City of Renton Amendments to the 2009 King County Surface Water Design Manual. Ill. OFF-SITE ANALYSIS Existing Conditions: Runoff from the western portion of the site generally sheet flows to southwest corner of the property. The runoff eventually falls off steep embankment and enters the Highway 405 drainage system. Based on the King County aerial topography, the flow then travels down south along the east side of the Highway 405 and ends up in a wetland/pond located near the NE Park Drive Interchange. The runoff is eventually discharged to the Lake Washington via series of storm drain systems. (See Downstream Map) Runoff from the eastern portion of the site generally sheet flows to southern neighbor and Jones Avenue NE. There is a 12 storm system that begins with a Type I Catch Basin located near the southeast corner of the property, across the Jones Avenue NE. (Photo I) This system captures the developed street flows from the Jones Avenue NE and routes it down to NE 16th Street via series of storm drain system. (Photos 2-10) The existing system continues down south on Jones Avenue to the NE 12th Street where the runoff outfalls to a steep ravine. The runoff then ends up in a wetland/pond near Highway 405 and NE Park Drive Interchange and eventually routed to Lake Washington via series of storm systems in NE Park Drive and Lake Washington Blvd. (See Downstream Map) Developed Conditions Runoff from the proposed roof area of Lot I will be dispersed to the natural discharged points with the roof splash blocks and gravel filled trenches. Proposed access driveway runoff will be collected via private storm system, and routed to the existing storm system in Jones Avenue NE. September 2016 Page 3 I I I I I Downstream Map 1.1K F\4\ t \\JS , ;;;..._-I J 1 I , , I I <::> (J \ \ \ / \ , / "-, ) /r The n formal1on 1ncl.Jded on ths map has been compied b y K1nq Cou nt y stall frorn a variety <:J scu-ces an d 1s subJec l to change 'Mlh out n otice King County ma.es no representations o r wa rr an~es . expm ss o rompl 1ed. as lo accura cy, completeness, tmelness. or rg l11s to the use of such 1nforma t1on. l h sdocumenl ,s no11111e nded for u se as a survey prod uct. King County sha ll not be iable for any gen er ill . special, ildirect irci de nta l , or r.onsequenoal damages inc luding , b ut not lrn ited to . lost rev e nues or bst prnfits re sul ti ng from the use or misuse of the inform ation con t ained m this map . Any sae d this m.1p or 1nfCtmation on ths map is proh bited except bot w ri tten permssion al King Cou n,y Dale : 8/412016 No tes : N A tQ King County GISCENTER Dylan Short Plat Preliminary Technical Information Report Photo 1 -Existing Catch B asin # l on Jones Avenue NE N ear Southeast Corner o f the Site Photo 2 -Ex isting Catch Basin #2 on Jones Avenue NE September 20 16 Page -l Dylan Short Plat Preliminary Technical Information Report Photo 3 -Existing Catch Basin #3 on Jones Avenue NE Ph oto 4 -Existing Storm S ystem Outlet to a Ditch on Jones Avenue NE September 20 16 Page 5 Dylan Short Plat Preliminary Technical Information Report Photo 5 -Existing Ditch on Jones A ve nue NE Photo 6 -Existing Ditch to Storm S ystem on Jones Avenue NE Se ptember 20 16 Page 6 Dvlan Short Plat Preliminary Technical Information Report Photo 7 -Storm System Outlet to a Ditch on Jone s Avenue NE Ph oto 8 -Storm System Crossing at Intersecti on of Jo ne s Av enue and NE 16th Street September 201 6 Page 7 Dylan Short Plat Preliminary Technical Information Report Photo 9 -Crossing Outfall at Intersection of Jones Avenue NE and NE 161h Street Photo 10 -Ex isting Ditch on Jones A venue past NE 16th Street Septe mber 2016 Page 8 a.. <( ~ z 0 I- <( 0 0 .....J >-I- .....J 0 <( LL 0 z <( 0 l-o I a.. Basin· Symbol see map A B C D E F G H I J K L OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 Subbasin Name· Subbasin Number· Drainage Drainage Slope Distance Existing Potential Component Type, Name, Component Description from site Problems Problems and Size discharge Type: sheet flow, swale, drainage basin, % \/, ml = 1,320 ft. constrictions, under capacity, ponding, stream, channel, pipe, pond; vegetation, overtopplng, flooding, habitat or Size: diameter, surface area cover, depth, type of organism destruction, scouring, bank sensitive area, volume sloughing, sedimentation, incision, other erosion 12-in Concrete Pipe 3°/o 270' No None 12-in Concrete Pipe ] o;o 400' No None 12-in Concrete Pipe 1% 492' No None Roadside Ditch Vegetated and well maintained 2o/o 565' No None 12-in Concrete Culvert 2°/o 880' No None Roadside Ditch Vegetated and well maintained 2o/o 975' No None 12-in Concrete Culvert 2°/o 1025' No None Roadside Ditch w/Gravel Vegetated and well 2°/o l090' No None outfall maintained 12-in Concrete Culvert 2°/o 1140' No None Roadside Ditch Vegetated and well 2o/o 1265' No None maintained 12-in Concrete Pipe 2°/o 1615' No None 12-in Concrete Pipe 2°/o 1725 No None Observations of field inspector, resource reviewer, or resident tributary area, likelihood of problem, overflow pathways, potential impacts Pipe flows south Pipe flows south Pipe flows south Lined with vegetation. No sign of erosion Pipe nows south Lined with vegetation. No sign of erosion Pipe flows south Gravel outfall at the end of culvert. No sign of overtonning and erosion Pipe flows south Lined with vegetation. No sign of erosion Pipe nows south Pipe outfalls to existing channel Dylan Short Plat Preliminary Technical Information Report IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Flow Control BMPs Based on the geotechnical report, infiltration is not feasible for the site. Full dispersion BMPs are also not feasible due to the long native vegetated flow path requirements. Basic dispersion BMPs are only options for the site. Proposed Lot 1 : Flow control BMPs for the proposed lot will be with gravel-filled dispersion trenches and roof splash blocks. Two I 0-foot long trenches are proposed on southeast and southwest comers of proposed lot I. All trenches will be at least IO feet from the proposed building and 5 feet from the property line. Three roof splash blocks with 50' minimum vegetated flowpath segments are also proposed around the building area. For the proposed driveway in lot 2, basic sheet flow dispersion BMP will be utilized. A 2-foot- wide, 4-inch-deep strip of crushed rock along with I 0-foot vegetated flow path will be provided along the proposed driveway edge. Shared Driveway: Basic dispersion BMPs will not work due the location and size of the driveway. A private 6" PVC storm system is designed to collect the runoff from the shared driveway and route it to the existing catch basin in Jones Avenue NE near the southeast corner of the property. All flow control BMPs proposed above are conceptual options for the approval of short plat and they need to be finalized in the Building Permit/Construction Application Process. Water Quality BMPs Water quality BMPs are not required, since the overall pollution generating impervious area is less than 5,000 square feet. (Shared Driveway 2,187 sf+ Driveway for Lot 2 500 sf= 2,687 sf) V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN Since the storm drain system is private and only serves for the shared driveway, a conveyance system analysis is not required. VI. SPECIAL REPORTS AND STUDIES Geotechnical Engineering Report Arborist Report September 2016 Page 9 Dylan Short Plat Preliminary Technical Information Report VII. OTHER PERMITS Building permits will be required. VIII. CSWPPP ANALYSIS AND DESIGN The potential for erosion within the site will be mitigated by use of erosion control measures during clearing, grading, and site development activities. Filter fences will be installed along the downhill perimeter of the site to protect adjacent properties from sediment-laden water. Stockpiles and exposed disturbed areas will be covered to protect from erosion and sediment runoff Element I: Mark Clearing Limits. All clearing, grading, sensitive areas, and buffers will be clearly marked in the field prior to construction in accordance to the plans and specifications. Prior to beginning land disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. These shall be clearly marked, both in the field and on the plans, to prevent damage and offsite impacts. Plastic, metal, or stake wire fence may be used to mark the clearing limits. Element 2: Establish Construction Access. Construction access will be provided for the site. Driveway re-alignment should be completed after all other construction is complete. Stabilize the construction access with rock per the storm water plans if the driveway is disturbed. Access points shall be stabilized with a pad of quarry spalls, crushed rock, or equivalent BMP prior to traffic leaving the construction site to minimize the tracking of sediment onto all roads and accesses. Element 3: Control Flow Rates. Flow rates from the construction site are not expected to negatively impact the downstream corridor. At all times, flow rates shall be controlled for this project. Natural drainage patterns shall be protected as much as possible during construction, and concentrated flow should not be permitted. Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. Element 4: Install Sediment Controls. Silt fence should be used to protect all sensitive area slopes. Soils should be covered if not worked for 7 days during the dry season or 2 days during the wet season. The street should be swept each night or as required. If the minimum BMPs fail to retain sediment to the sight, additional BMPs will be used. September 2016 Page 10 Dylan Short Plat Preliminary Technical Information Report Element 5: Stabilize Soils. Soils shall be covered if not worked for 7 days during the dry season or 2 days during the wet season. Soil stockpiles will be covered unless worked. Soil stockpiles shall be located away from drain inlets and surface water discharge locations. Soil stockpiles shall be stabilized and covered as needed or removed to an approved disposal site. Soils shall be stabilized at the end of the shift before holidays or weekends if needed based on weather forecast. Element 6: Protect Slopes. The site does not contain any steep slope areas; however, it borders a steep slope to the west. (Highway 405 embankment) Flows are dispersed exiting the site to the west so no slope protection is anticipated. Element 7: Protect Drain Inlets. There are existing catch basins located downstream of the project. Filter fabric protection shall be used for sediment control. Element 8: Stabilize Channels and Outlets. Existing or proposed channels or drainage outlets are not components of this project, thus stabilization of these elements are not required. Element 9: Control Pollutants. Pollution generated from construction must be controlled at all times. Control of pollutants other than sediments include the following: • • • • All pollutants other than sediments shall be handled and disposed of in a manner that does not cause contamination of stormwater. Cover, containment and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and non-inert wastes present on the project site. Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system or to the sanitary sewer, if available. Element 10: Control De-Watering. De-watering is not anticipated for the site. In the event that dewatering is necessary, storm shall be treated such that sediment remains on site. This shall be done by routing the storm water through a straw filter, silt fence, and/or sediment trap. September 2016 Page l l Dylan Short Plat Preliminary Technical Information Report Element 11: Maintain BMPs. BMPs shall be inspected monthly and after every significant storm event, sediment shall be removed from the BMPs as necessary for them to continue operating at the required performance level. In the event that a BMPs has been damaged, it shall be replaced immediately. Element 12: Manage the Project. Construction activities shall be phased such that the impact to the area will be kept at a minimum. Coordination will occur with all utility agencies that are affected by this project. BMPs shall be inspected regularly and after each significant storm event. The Contractor will provide a Certified Erosion and Sediment Control Specialist. If for any reason a BMPs is not sufficient for the project, additional BMPs will be installed. IX. BOND QUANTITIES and DECLARATION of COVENANT Bond Quantities Not applicable. Facility Summaries Not applicable. Declaration of Covenant Declaration of Covenant for maintenance will have to be approved and recorded. X. OPERATION AND MAINTENANCE MANUAL Operation and maintenance manual will be provided in final engineering. September 2016 Page 12 Dylan Short Plat September 2016 Preliminary Technical Information Report Appendix A Drainage Area Calculations KCRTS Input/Output Page 13 Area Calculations: Area Breakdown: Lot 1-10,732, sf (0.25 ac) Lot 2-9,993 sf (0.23 ac) Shared Driveway-2,187 sf (0.05 ac) Impervious Area Calculation for KCRTS: • No improvements are proposed for Lot 1 so the area will be excluded from the KCRTS analysis Roof for Lot 2: 35% of Lot 2 = 0.35 x 9,993 sf= 3,498 sf Driveway for Lot 2: 16 ft x 30 ft= 480 sf (use 500 sf) Shared Driveway: 2,187 sf TOTAL IMPERVIOUS: 6,185 sf (0.14 ac) KCRTS Analysis Soil Type: Existing-Till (Forest) Developed -Impervious & Till (Grass) Rain Region: SeaTac-Scale Factor= 1.0 Total Area: 0.53 ac Area Analyzed: 0.28 ac 16576 Dylan Short Plat -KCRTS INPUT FILE KCRTS Program ... File Directory: C:\KC_SWDM\KC_DATA \ (CJ CREATE a new Time Series ST 0.28 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.00 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.00 0.00 0.000000 Impervious Existing.tsf T 1.00000 T [CJ CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.14 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.14 0.00 0.000000 Impervious Developed.tsf T 1.00000 T [Tl Enter the Analysis TOOLS Module [Pl Compute PEAKS and Flow Frequencies developed.tsf Dev.pks [R) RETURN to Previous Menu [Tl Enter the Analysis TOOLS Module [Pl Compute PEAKS and Flow Frequencies existing.tsf Ex.pks [RI RETURN to Previous Menu [XI eXit KCRTS Program Peak Output.pks 16576 DYLAN SHORT PLAT -KCRTS PEAK OUTPUT Flow Frequency Analysis Time Series File:existing.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak {CFS) 0.018 2 2/09/01 18:00 0.005 7 1/06/02 3:00 0.013 4 2/28/03 3:00 0.001 8 3/24/04 20:00 0.008 6 1/05/05 8:00 0.014 3 1/18/06 21:00 0.012 5 11/24/06 6:00 0.022 1 1/09/08 9:00 Computed Peaks Flow Frequency Analysis Time Series File:developed.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0.046 5 2/09/01 2:00 0.036 8 1/05/02 16:00 0.056 2 2/27/03 7:00 0.038 7 8/26/04 2:00 0.046 6 10/28/04 16:00 0.049 4 1/18/06 16:00 0.055 3 10/26/06 0:00 0.096 1 1/09/08 6:00 Computed Peaks -----Flow Frequency Analysis------- --Peaks --Rank Return Prob {CFS) Period t.1211 1 100.00 0.990 0.018 2 25.00 0.960 0.014 3 10.00 0.900 0.013 4 5.00 0.800 0.012 5 3.00 0.667 0.008 6 2.00 0.500 0.005 7 1.30 0.231 0.001 8 1.10 0.091 0.021 50.00 0.980 -----Flow Frequency Analysis------- --Peaks Rank Return Prob (CFS) Period ••• 1 100.00 0.990 0.056 2 25.00 0.960 0.055 3 10.00 0.900 0.049 4 5.00 0.800 0.046 5 3.00 0.667 0.046 6 2.00 0. 500 0.038 7 1.30 0.231 0.036 8 1.10 0.091 0.083 50.00 0.980 ::. () .()C\!o -0.022. : 0 ,014 "-0. I cts. ~QIDO Page 1 Dylan Short Plat September 20 16 Preliminary Technical Information Report Appendix B Geotechnical Report Page 14 Ages Engineering, LLC P<l BP_'{9)5 f'u'\aUup. \\ A 'JK.l ~ ! (25'":) 11.4)-7000 www age~cngmei::nng com A Geotechnical and Environmental Services, LLC PRELIMINARY GEOTECHNICAL REPORT Dylan Short Plat 1909 Jones A venue NE Renton, Washington Project No. A-1278 Prepared For: Ken Neault 1909 Jones Avenue NE Renton, \Vashington 98056 .July 6, 2016 Ages Engineering, LLC A Geotechnical and Environmental Services LLC Ken Neault l 909 Jones A venue NE Renton. WA. 98056 Subject: Prelimmary Geotechnical Report Dylan Short Plat l 909 Jones A venue NE Renton, Washington Parcel Number: 3344500120 Dear Mr. Neault P.O 13ox <.11.5 Puyallup. WA !)>n7\ www ai.zesei.uuneeruuz i.::nm July 6, 2016 Project No. A-1278 As requested, we have conducted a prehmmary geotechnical study for the sub_Ject project. The attached report presents our findmgs and recommendations for the geotechnical aspects of project design and construction. Our field exploration indicates the site is generally underlam by silty sand with gravel cons!Stent with glacial till. The 1111 became dense and unweathered at a depth of 4.0 feet below surface grades. We did not encounter groundwater seepage m any of the test holes excavated on site. In our opm10n, the soil and groundwater condltlons at the site are suitable for the planned development. The new structures can be supported on conventional spread fooung foundations bearing on the ex1stmg orgaruc-free nari ve soils observed at a depth of 1.5 feet below surface grades, or on structural fill placed above these native soils. Floor slabs and pavements can be ,1milarly supported. Due to the low permeability and relative density of the soils underlying the site. the development stom1 water should discharge off of the site. Detailed recommendations addressmg these issues and other geotechnical design considerations are presented in the attached report. We trust the mformat1on presented is sufficient for your current needs. If you have any questions or require additional information, please call. A!1,.e. En~un=nag._ I.LC ~:;'-""'--:'()(kl Pagel Respectfully Submmed. Ages Engineering, LLC Bernard P. Knoll. !I Principal BPK hpk Pn111;:.:T Numh<!'I" ,\-l 27k Pro1ect 1\/amt' Dylan <.;hPrt Pl<1t Oute July 6, 20l6 '\gL-:,, Engme~nn!?. LI_:.., P,1ge 2 2:.> L.''.\45--,!JOO TABLE OF CONTENTS 1.0 PROJECT DESCRIPTION 2.0 SCOPE ... 3.0 SITE CONDITIONS 3. I Surface .... . 3.2 Soils ..... . 3.3 Mapped Soils. 3 .4 Groundwater 4.0 CRITICAL AREAS 4.1 General ...... . 4.2 Steep Slope 4.3 Landslide ..... 4.4 Erosion ... 4.5 Seismic .. 5.0 CONCLUSIONS AND RECOMMENDATIONS 5.1 General ..... 5 .2 Site Preparation and Grading 5.3 Excavations ............ . 5.4 Foundations. 5 5 Slab-on-Grade Floors 5.6 Lower level Building and Concrete Retaining Wall 5.7 Storm Water. 5. 8 Drainage ... 6.0 ADDITIONAL SERVICES . i.O LIMITATIONS Site Vicinity Map Exploration Location Plan . Geologic Map . Site Exploration . . \g:t....., En~n.xnng. l LC ~)S-8..1'--7000 Figures Appendix ' ..... l . .............. I . .. 2 ...3 .3 ................ .3 .4 . ... .4 ......... 4 ...4 . ........ 5 .5 .6 .. ........................ 6 ....... 7 . .. 8 ..8 .. 9 ............... 9 . ........ 10 . ... II . ......... l l ..... II .............. Figure I . .Figure 2 ..Figure 3 ..Appendix A Page I Preliminary Geotechnical Report Dylan Short Plat 1909 Jones Avenue NE Renton, Washington 1.0 PROJECT DESCRIPTION The project will consist of dividing the existing residential lot into two residential lots. We discussed the project with the site owner, and were provided with a notice from the City of Renton that had a Storm Water Comments section indicating a geotechnical report is required to provide information on the water table and soil permeability, with recommendations of appropriate flow control BMP options with typical designs for the site. Based on our conversation and review of the notice provided to us, we understand the existing residence on the site will remain and a new single family residential lot will be established along the western end of the site. The eastern end of the site is currently occupied with an existing single-fam1ly residence. Access to the existing residence is currently provided by a driveway that enters the lot at the NE comer and curves back to exit the lot at the SE comer. We expect access to the new lot will be by a driveway constructed along the north property line. Detailed buildmg plans are currently not available. However. based on our experience with similar projects m the vicinity of the site, we expect the new residence will be a two-to three- story wood-framed structure with the main floor constructed with raised floors over a crawl space. The attached garage will likely have a slab-on-grade floor. Foundation loads should be relatively light on the order of l to 3 kips per lineal foot for connnuous footings, and up to 25 kips for column loads. Due to the site being underlam with dense, relatively impermeable glacial till, and with a steep slope immediately down gradient of the site. we expect the infiltration of the development storm water will not be possible. Therefore, development storm water will discharge off of the site. The conclusions and recommendations presented in this report are based on our understanding of the above stated site and the planned project design features. If actual site conditions differ, the planned project design features are different than we expect or if changes are made, we should review them in order to modify or supplement our conclusions and recommendations as necessary. 2.0 SCOPE On June 29, 2016, we advanced three hand-augured Test Holes to a maximum depth of 5.5 feet below surface grades. Using the information obtained from our subsurface exploration, we developed geotechnical desit,'11 and construction recommendations for the project. Specifically this Preliminary Geotechnical Report addresses the following: :\gt:S Engmec-nng:. LLC 2.5"<-845-7lJl)l) Pagel • Reviewing the available geologic. hydrogeologic and geotechnical data for the site area, and conducting a geologic reconnaissance of the site area. • Addressing the appropriate geotechnical regulatory requirements for the planned site development. including a Geologic Hazard evaluation. • Advancing three test holes in the planned new development area to a maximum depth of approximately 5.5 feet below surface grades. • Providing geotechnical recommendations for site grading including site preparation, subgrade preparation, fill placement criteria, suitability of on-site soils for use as structural filL temporary and permanent cut and fill slopes. and drainage and erosion control measures. • Providing geotechnical recommendations for design and construction of new foundations and tloor slabs. including allowable bearing capacity and estimates of settlement. • Providing geotechnical recommendations for lower level building or retaining walls, including backfill and drainage requirements, lateral design loads, and lateral resistance values. • Providing an evaluation of the steep slopes along the western end of the site. • Providing geotechnical recommendations for the development storm water system. • Providing recommendations for site drainage. It should be noted that our work does not include services related to environmental remediation or design and performance issues related to moisture intrusion through walls. An appropriate design professional or qualified contractor should be contacted to address these issues. 3.0 SITE CONDITIONS 3.1 Surface The sub1ect site is a residential parcel located at 1909 Jones Avenue '-IE m the Renton Highlands area of Renton, Washmgton. The site 1s currently occupied with a single-family residence located in the eastern end of the site. A driveway enters the lot at the NE corner and curves back to exit the lot at the SE comer A gravel parking area exists along the north side of the existing residence. A garden area has been delineated along the center of the sites' southern property line. A rockery ranging in height from 2.0 to 5.0 feet exists between the existing residence and the garden area. The site is bordered with existing residential lots to the north and south, Jones Avenue NE to the easl and a slope down to Interstate 405 to the west. Surface grades on the site slope down to the west at surface inclinations ranging from 5 to I 0 percent. There are flat areas along the eastern end of the site and in the garden area. .A slope down to Interstate 405 exists beyond the sites· western property line. The lower portions of the slope were graded during development of the interstate and were engineered to a surface inclination of 100 percent (also referred to as a l: l (Horizontal:Vertical) slope). The upper portions of the slope were graded to less steep mclmations. For a horizontal distance of 25 feeL surface grades slope down to the west from the sites' NW comer at surface mclinat1ons of approximately 62 percent. or a hotizontal distance of 25 feet. surtace grades slope down to the Aile-Enµ:mt't'rm!l, LLC ~:,1_q:,_ ..,non west from the sites· SW corner at surface inclinations of approximately 21 percent. Along the center of the sites· western margin. the surface is relatively flat for a horizontal distance of approximately 25 feet. Site vegetation consists of grass and typical landscape bushes and trees around the existing single-family residence. The location of the site is shown on the Site Vicinity Map provided in Figure l. 3.2 Soils The soils we observed in the test holes generally consist of a thin layer of topsoil overlying native silty sand with gravel consistent with glacial till. ln all three of the test holes excavated on the site, we encountered 6 inches of grass roots and topsoil overlying tan and orange, moist, medium dense silty sand with gravel to a depth of 1.5 feet below surface grades. Below 1.5 feet. the soils became tan. moist. and medium dense. At a depth of 4.0 feet below surface grades. the native silty sand with gravel became dense. These native soils are consistent with glacial till. Figures A-I and A-2 present more detailed descriptions of the subsurface conditions encountered in the test holes. The approximate test hole locations are shown on the Exploration Location Plan provided in Figure 2. 3.3 Mapped Soils According to the Geologic ,Hap of King Cmmfv. the soils in the vicinity of the site are mapped as Glacial Till (Qvt). The glacial till was deposited during the Vashon stade of the Fraser Glaciation approximately I 0.000 years ago. The glacial till was deposited along the base of the advancing glacial ice and was consequently overrun by the continental ice mass. The glacial till soils are described as a relatively impenneable well-graded mixture of sand, silt and gravel. The glacial till. and all units under the glacial till soils, will typically be found in a very dense condition, and will exhibit a high shear strength and low compressibility where undisturbed. The near surface soils at the site have been disturbed by natural weathering processes that have occurred since their deposition. No spnngs or grmmdwater seepage was observed on the surface of the site at the time of our site visit. A copy of the Geologic ~fap for the subject site is provided in Figure 3. 3.4 Groundwater We did not encounter groundwater seepage in any of the test holes excavated at the site. However. we expect a perched water table may develop above the dense glacial till soils duting the wet wmter months. The groundwater levels and flow rates will fluctuate seasonally and typically reach their highest levels dunng and shortly following the wet winter months (October through May). 1'\.ge-, [-n!?,m~nng_ LLC 2'i>-1W~--:'000 4.0 4.1 CRITICAL AREAS General According to Section 4-11-030 in the City of Renton Municipal Code (RMC). Critical Areas are defined as. ··wetlands. aquifer protection areas, fish and wildlife habitat, frequently flooded and geologically hazardous areas as defined by the Growth Management Act and RMC 4-3-050 ... According to Section 4-3-050 in the RMC. geologically hazardous areas that are considered Critical Areas include steep slopes. landslide hazards, erosion hazards. seismic hazards. andior coal mine hazards 4.2 Steep Slopes According to Section 4-3-050-G.Sa in the City of Renton Municipal Code ( RM('). Steep Slope Hazard Areas are defined according to two slope types. Sensitive Slopes and Protected Slopes. Specifically the RMC defines these two slope types as follows: "i. Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of twenty five percent {25%) to less than forty percent (40%) as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of forty percent (40%) or greater with a vertical rise of less than fifteen feet ( 15") as identified in the City of Renton Steep Slope Atlas or in a method approved by the City: (c) abutting an average slope of twenty five percent (25%) to forty percent (40%) as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. This definition exdudes engineered retaining walls. ii. Protected Slopes: A hillside, or portion thereof. characterized by an average slope of forty percent {40%) or greater grade and having a minimum vertical rise of fifteen feet (l S') as identified in the City of Renton Steep Slope Atlas or in a method approved by the City." Based on our site observations. the surface grades on the slope to the west of the site exceed 40 percent and therefore meet the critena for Protected Slopes. According to Section 4-3-050-G.2 in the RMC. Protected Slopes do not require a Cnncal Area Buffer. However, they do require a 15- foot strucn,ral setback. 4.3 Landslide According to Section 4-3-050-G.Sb in the City of Renton Municipal Code (RMC), Landslide Hazards are divided into four categories, Low, Medium, High, and Very High. Specifically the RMC defines these four categories as follows: "i. Low Landslide Hazard (LL): Areas with slopes Jess than fifteen percent ( 15%). ii. Medium Landslide Hazard (LM): Areas with slopes between fifteen percent ( 15%) and forty percent (40'!o) and underlain by soils that consist largely of sand. gravel or glacial tdl. iii. High Landslide Hazards (LH): Areas with slopes greater than forty percent (40°,o). and areas with slopes between fifteen percent ( 15°'0) and forty percent (40%) and underlain by soils consisting largely of silt and clay. Ag~ Engmt'>.!nng. LL( ~'.'1-845-7l)l)I) Page 4 iv. Very High Landdide Hazards (LV): Areas of known mapped or identified landshde deposits." Based on the current site grades, the subject site is classified as having a Low Landslide Hazard. The slope to the west of the subject site is classified as having a High Landsltde Hazard. According to Section 4-3-050-G.2 in the RMC, High Landslide Hazard areas may not require a Critical Area Buffer or Structural Setback, based on the results of a geotechnical report. In our opinion, due to the site being underlain with medium dense to dense silty sand with gravel consistent with glacial till. no Critical Area Setback or Structural Setback is necessary. Provided surface water is controlled on the site, and all structures are provided with proper subsurface drainage measures, the potential for a landslide to occur at this site should be considered low. 4.4 Erosion According to Section 4-3-050-G.5c m the City of Renton Mumcipal Code (RMC), Erosion Hazards are divided into two categories, Low and High. Specifically the RMC defines these two categones as follows: ··;. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential, and a slope less than fifteen percent ( 15%). ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conser,ation Service (formerly U.S. Soil Conservation Service) as having severe or very severe erosion potential, and a slope more than fifteen percent 115%)." According to the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service), the soils on the subject site have a slight erosion potential. The soils on the slope to the "est of the site will have a severe potential for erosion. No development 1s planned on the slope to the west oftbe site. Typical Temporary Erosion and Sediment Control (TESC) measures must be in place pnor to and maintained durmg construction activity at the slle. In our opmion, the potential for erosmn is not a lim1tmg factor in slle development. Erosion hazards can be mitigated by applying Best Management Practices (BMPs) outlined in the Washington State Department of Ecology·s (Ecology) Slonmmler Mana1<emenl Ham,a//ur Wes/em Washing/on. Temporary Erosion and Sediment Control (TESC) measures, as required by the City of Renton, should be in place prior to the start of construction activities at the site. 4.5 Seismic According to Section 4-3-050-G.5d in the City of Renton Municipal Code (RMC), Seismic Hazards are cti,~ded into two categories. Low and High. Specifically the R,'v!C defines these two categories as follows: '"i. Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils generally have site classifications of A through D. as defined in the lnternational Building Code, 2012 Ag¢-. Engmcxnng, I..LC 251-84~-700(! Page 5 ii. High Seismic Hazard (SH): Areas underlain by soft or loose. saturated soils. These soils generally have site classifications E or F. as defined in the International Building Code, 2012." Due to the site being underlain with medium dense to dense silty sand with gravel consistent with glacial till, according to the RMC, the site is considered a low Seismic Hazard Area. liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in pore water pressure. The increase in water pressure is typically induced by vibrations. liquefaction mainly affects geologically recent deposits of loose, fine-grained sands that are below the groundwater table. Based on the relative density and well-graded nature of the glacial till soils underlying the site, the risk for liquefaction to occur at the site should be considered negligible. The state of Washington has adopted the International Building Code (!BC). Based on the soil conditions encountered and the local geology, per chapter 16 of the (!BC) site class "C" can be used in structural design. This correlates to Soil Profile Type Sc in the older Uruform Building Code (l/BC). This is based on the inferred range of SPT (Standard Penetration Test) blow counts for the upper I 00 feet of the site relative to hand excavation progress and probing with a ,'.:-inch diameter steel probe rod. The presence of glacially consolidated soil conditions were assumed to be representative for the site conditions beyond the depths explored. 5.0 CONCLUSIONS Al'I/D RECOMMENDATIONS 5.1 General Based on our study. in our opinion, soil and groundwater conditions at the site are suitable for the proposed development The new structures can be supported on conventional spread footings beanng on the existing native orgamc-free soils observed below a depth of l .5 feet on the site, or on structural fill placed above these native soils. Floor slabs and pavements can be similarly supported. No buffer will be required along the western property margin. However, a structural setback of 15 feet will be necessary from the crest of the slopes to the west of the site that exceed 40 percent for a vertical height of 15 feet. Based on our site observations, the structural setback may encroach on the NW and SW site comers. Due to the low permeability and relative density of the native soils underlying the site, the development storm water should discharge off of the site. The native soils encountered at the site contain a high enough percentage of fines (silt and clay- size particles) that will make them difficult to compact as structural fill when too wet Accordingly. the ability to use the soils from site excavations as structural fill will depend on their moisnire content and the prevailing weather conditions at the time of construction. ff gradmg activities will take place during the winter season. the owner should be prepared to import free-<lraining granular matenal for use as structural fill and backfill. The following sections provide detailed recommendations regarding these issues and other geotcchnical design considerations. These recommendations should be incorporated into the final design drawings and construction specifications. Ag.i:..'!i EngUit.>t>mig. LLl ~51-845-7()()!1 Page h 5.2 Site Preparation and Grading To prepare the site for construction, all vegetation. organic surface soils, and other deleterious materials including any existing structures, foundations or abandoned utility lines should be stripped and removed from the new development areas. Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired grades. Io order to achieve proper compaction of structural fill. and to provide adequate foundation and floor slab suppot1, the native subgrade must be in a stable condition. Prior to placing structural fill, and to prepare the foundation subgrade, all exposed surfaces should be compacted with heavy vibratory compaction equipment to determine if any isolated soft and yielding areas are present If excessively soft or yielding areas are present and cannot be stabilized in place by compaction, they should be cut to firm bearing soil and filled to grade with structural fill. [f the depth to remove the unsuitable soil is excessive, using a geotextile fabric can be considered, such as Mirafi HP270 or an approved equivalent, in conjunction with strnctural fill. In general. a minimum of 18-inches of clean, granular strnctural fill over the geotextile fabric should establish a stable bearing surface. A representative of Ages Engineering, LLC should observe the foundation subgrade compaction operations to verify that stable subgrades are achieved for support of structural elements. Our study indicates the native surface soils encountered at the site contain a sufficient enough percentage of fines (silt and clay-size particles) that will make them difficult to compact as strnctural fill when too wet. Accordingly, the ability to use the soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions at the time of construction. If grading activities are planned during the wet winter months. or the on- site soils become too wet to achieve adequate compaction. the owner should be prepared to import a wet-weather structural fill. For wet weather structural till, we recommend importing a granular soil that meets the following gradation requirements: U. S. Sieve Size Percent Passing 6 inches 100 No. 4 75 maximum ~------_:_:c:__::.:.....:_ ______ -+ ____ _:_::....:. -------------J No. 200 5 maximum* . __________ L_ ___ .....c.--====-'-------------' *" Ba:-.t::d 11n the i,;, mch frad1<in Prior to use, Ages Engineering, LLC should examine and test all materials to be imported to the site for llSe as strnctural fill. Strnctural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of 95 percent of the soils' laboratory maximum d,y density as determined by American Society for Testing and Materials (ASTM) Test Designation D-1557 (Modified Proctor). The moisture content of the soil at the time of compaction should be within two percent Agt....., Eng.mei::nng. LLC 251-84:'i-11)00 Page'"' of its optimum, as detemuned by this same ASTM standard. In non-structural areas. the degree of compacuon can be reduced to 90 percent. 5.3 Excavations All excavations at the site associated with confined spaces, such as utility trenches and lower level building and retaining walls. must be completed in accordance with local, state, and/or federal requirements. Based on current Washington State Safety and Health Administration (WSHA) regulations. the existing near-surface loose to medium dense weathered soils are classified as Type C soils. The deeper unweathered dense to very dense soils would be classified as Type A soils. According to WSHA. for temporary excavations of less than 20 teet m depth, the side slopes in Type C soils should be laid back at a slope inclination of 1.5: I (Horizontal:Vertical) or flatter from the toe IO the crest of the slope and the side slopes in Type A soils should be laid back at a slope inclination of 0.75: l (Horizontal:Vertical) or flatter from the toe to the crest of the slope. All exposed slope faces should be covered with a durable reinforced plastic membrane during construction to prevent slope raveling and rutting during periods of precipitation. These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the excavation slope and that significant seepage is not present on the slope face. Flatter cut slopes will be necessary where significant raveling or seepage occurs, or if construction materials will be stockpiled along the slope crest. lf these safe temporary slope inclinations cannot be achieved due to property line constraints. shoring may be necessary. This information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Ages Engineering. LLC assumes responsibility for job site safety. It is understood that Job SJte safety 1s the sole respons1b1lity of the proJect contractor. 5.4 Foundations The new foundations may be supponed on convent10nal spread footing foundations bearing on the competent native organic-free native soils or on structural fills placed above these native soils. Foundation subgrades should be prepared as recommended in the "Site Preparation and Grading" section of this repon. Perimeter foundations exposed to the weather should bear at a minimum depth of 1.5 feet below final exterior grades for frost protection. Interior foundations can be constructed at any convement depth below the floor slab. We recommend designing new foundations for a net allowable bearing capacity of 2j00 pounds per square foot (psf). For short-term loads, such as wind and seismic. a one-third increase in this allowable capacity can be used. With the anticipated loads and this bearing stress applied, building settlements should be less than one-half inch rota] and one-quarter inch differential. For designing foundat,ons to resist lateral loads. a base friction coefficient of 0.35 can be used. Passive earth pressures acting on the sides of the footings can also be considered. We .'\~L-., Ellgmeermg. U.C Page~ ~51-.':IA5-7000 recommend calculating this lateral resistance using an equivalent fluid weight of 325 pounds per cubic foot (pct). We recommend not including the upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This value assumes the foundations will be constructed neat against competent soil and backfilled with structural fill, as described in the ··Site Preparation and Grading" section of this report. The values recommended include a safety factor of 1.5. Foundation Parameter Summarv ! -- Descrintion I *Desi!!n Value Net Allowable Bearing Capacity I 2,500 osf I Friction Coefficient I 0.35 Lateral Resistance i 325 ncf *Details regarding the us.I! ofth~ parnmeters .tre provided m the ;;c:ctinu above_ 5.5 Slab-On-Crade Slab-on-grade t1oors should be supported on subgrades prepared as recommended in the "Site Preparation and Grading" section of this report. Immediately below the floor slab, we recommend placing a four-,nch thick capillary break layer of clean, free-draining, coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slabs. The drainage material should be placed in one lift and compacted lO a firm and unyielding condition. The capillary break layer will not prevent moisrure intrusion through the slab caused by water vapor transmission. Where moisture by vapor ~-ansmission is undesirable, such as covered floor areas. a common practice is ro place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel ro protect it from damage during construction, and aid in uniform curing of the concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated piior to pouring the slab. it will not assist in unifom1 curing of the slab, and may serve as a water supply for moisture transmission through the slab and affecting floor covenngs. Additionally. if the sand is too dry, it can effectively drain the fresh concrete. thereby lowenng its strength. Therefore. ,n our opm10n, covering the membrane with a layer of sand or gravel should be avoided. 5.6 Lower Level Building and Concrete Retaining Walls The magnitude of earth pressure development on below-grade walls. such as basement or retaining walls. will greatly depend on the quality of the wall backfill and the wall drainage. We recommend placing and compact,ng wall backfill as structural fill. Wall backfill below structurally loaded areas. such as pavements or floor slabs, should be compacted to a minimum of Agt.--s EngmL>enng. 1..LC 2),1-:-{45-7000 95 percent of its maximum dry density, as detennined by ASTM Test Designation D-1557 (Modified Proctor). In unimproved areas, the relative compaction can be reduced to 90 percent. To guard against hydrostatic pressure development, drainage must be installed behind the wall. We recommend that wall drainage consist of a minimum 12 inches of clean sand and/or gravel with less than three percent fines placed against the back of the wall. In addition, a drainage collector system consisting of 4-inch perfurated PVC pipe should be placed behind the wall to p1mide an outlet for any accmnulated water. The drains should be provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once every year. The wall drainage material should be capped at the ground surface with I-foot of relatively impermeable soil to prevent surface intrusion into the dramage zone. Alternatively, the 12-inch wide drainage layer placed against the back of the wall can be replaced with a Mirafi GI OON Drainage Board, or an approved equivalent If drainage board is used, the 4-inch perforated PVC pipe should be covered with at least l 2 inches of clean washed gravel and the drainage board should be hydraulically connected to drainpipe and surrounding gravel. With wall backfill placed and compacted as recommended and the wall drainage properly installed, unrestrained walls can be designed for an active earth pressure equivalent to a fluid weighing 35 pcf. For restrained walls, an additional uniform lateral pressure of I 00 psf should be included. These values assume a horizontal backfill condition and that no orher surcharge loading, such as traffic, sloping embankments, or adjacent buildings, will act on the wall. If such conditions exist. then the imposed loading must be included in the wall design. Friction at the base of the wall foundation and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in the "Foundations" section of this report. Lower Level Building and Retaining Wall Parameter Summary ___J Description Condition *Design Value Earth Pressure Unrestrained 35 'f i Earth Pressure Restrained Additional l 00 sf ' __ " _______ _ --~E=a.J=th==P=re=s=s-=u=re'--__ L._ __ S=ur=c=h=ar=e'--_.....L~Dc..e=e=n=d=en__t upon magnitude 5.7 Storm Water According to the Core Requirements provided in Secnon4-6-030-E.3 in the RMC, the primary option for the discharge of the storm water collected in the roof downspouts and foundation drains is at its natural location. If the discharge cannot occur without impacting the downhill properties or drainage systems, the collected storm water should discharge off of the site. A downstream analysis and flow control will be needed pnor to approval from the City. Based on our evaluation, the site is underlain with medium dense to dense silty sand with gravel consistent with glacial till. Due to the low permeability and relative density of the native soils underlying the site. the infiltration of the collected storm water will not be feasible. If discharged Ag~ Engmeermg, LLC 2'.-~-1-l--l',-"Tnoo on site, we expect the slope to the west (downhill) of the site may be adversely impacted. Therefore. the development storm water should discharge off of the site. 5.8 Site Drainage Surface, Final exterior grades should promote free and positive drainage away from the building area. All ground surfaces. pavements, and sidewalks should be sloped away from the structure. We recommend providing a gradient of at least three percent for a minimum distance of ten feet from the building perimeter. except in paved locations. In paved locations. a minimum gradient of one percent should be provided. unless provisions are included for collection and disposal of surface water adjacent to the structure. Subsurface, We recommend installing a continuous drain along the lower outside edge of the perimeter building foundation. The fowidation drain should be tightlined to an approved point of conrrolled discharge. The roof drain should not be connected to the footing drains unless a backflow device will be installed, or an adequate gradient will prevent backflow into the footing drains. Subsurface drains must be laid with a gradient sufficient to promote positive flow to the point of discharge. All drains should be provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once every year. 6.0 ADDITIONAL SERVICES Ages Engineering, LLC should review the final pro3ect designs and specifications in order to verify that earthwork and foundation recomme.ndanons have been properly interpreted and incorporated into project design. If changes are made in the loads. grades. locations, configura· lions or types of facilities to be constructed. the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made. we should be given the opportunity to review our recommendations and provide written modifications or verifications. as necessary. We should also provide geotechnical services during construction to observe compliance with our design concepts, specifications. and recommendations. This will allow for expedient design changes if subsurface conditions differ from those anticipated prior to the start of construction. 7.0 Ll~ITATIONS We prepared this report in accordance with generally accepted geotechnical engineering practices. 'io other warranty. expressed or implied, is made This report is the copyrighted property of Ages Engineering. LLC and is intended for the exclusive use of Mr. Ken Neault and Ag.e;.. lngml~rmg. LLC 25•-8-n:-..,J)OO Page I! his authorized representatives for use in the design, permitting, and construction portions of this project. The analysis and recommendations presented in this report are based on data obtained from others and onr site explorations, and should not be construed as a warranty of the subsurface conditions, Variations in subsurface conditions are possible. The nature and extent of which may not become evident until the time of construction. If variations appear evident, Ages Engineering, LLC should be retJuested to reevaluate the recommendations in this report prior to proceeding with construction. A contingency for unanticipated subsurface conditions should be included in the budget and schedule. Sufficient monitoring, testing and consultation should be provided by onr firm during construction to confirm that the conditions encountered are consistent with those indicated during our exploration, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods. techmques, sequences or procedures, except a, specifically described in our report for consideration in design . . \gt>~ Engm~1::rn1~. LLL 25 ·q,:45_ ""000 Page 12 ,, , .. Re ntc.,11 ~lurnnp-'11 41 1 p0 1t • , I -~,u . , ' :, ., . . : 1l (>07 !192 44892 6 =- ::: ·< !l { . , = ... ~ = .. ·,.: :. Renton '.t I • .., ,. ., Approximate Site Location Ages Engineering, LLC ' p () 8oK 935 Pu ya llup. WA 98J 7 I Main \2 51) 1<45 -7000 W"'W ,1gt:Se0~1u..,er1ng i.;om Site Vicinity Map Dylan Short Plat I 909 Jones A venue NE Renton , Washington Project No.: A-12 78 July 2016 ., Figure I KEY: APPROXIMA IT l.CX.A noN OF [EST HOLES r t-r-t • Ag~s Engi ne~ring. ·LL(, P 0 Bo:\ 'IJ5 Puyallup. WA. 9&:ni Mam (25J J 845-7000 www.agcsengm....ruig.~-..,m E:xploratioo Location Plan Dylan Short Plat l 909 Jones A venue NE Renton, Washington ProJect No.: A-1278 July 2016 Figure 2 Q) 0,·1 -:::::. <( ' Approximate Site Location Ages Engineering, L LL' P O Bux 915 J>u y.lllup. WA 9f071 Mam (~53) 845-71)()0 v.·,,,w ae,t.-seogmeer:ug .c, .. n Geologic Map Dylan Short Plat 1909 Jones A venue NE Renton, Washington Project ~o.: A-1278 July20t6 .::::::: ~ ~ N 4tf Figure 3 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING Dylan Short Plat Renton~ Washington On June 29, 2016 we explored subsurface conditions at the site by excavating three hand-augured test holes to a maximum depth of 5.5 feet below surface grades. The approximate test hole locations are shown on the Exploration location Plan provided in Figure 2. The test hole logs are presented on Figure A-2. ' A geotechnical engineering representative from our office conducted the field exploration, maintained a log of each test hole and, classified the soils encountered, collected representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure A-1. Representative soil samples obtained from the test holes were placed in sealed containers and taken to our laboratory for further examination and testing. The moisture content of each sample was measured and is reported on the test hole logs. Project No . A-1278 UNIFIED SOIL CLASSIFICATION SYSTEM f GROUP --, MAJOR DMSIONS SYMBOL GROUP NAME GRAVEL GW Well-Graded GRAVEL WITH < 5 % FINES GP Poorly-Graded ORA VEL GRAVEL GRAVEL GW-GM Well-Graded GRAVEL with silt WlTH GW-GC Well-Graded GRAVEL with clay BETWEEN More than 50% 5 AND 15% GP-GM Poorly-Graded GRAVEL with silt Of Coarse Fraction FINES COARSE Retained on GP-GC Poorly-Graded GRAVEL with clay GRAINED No. 4 Sieve GRAVEL GM Silty GRAVEL SOILS \VITH > 15 % FINES GC Clayey GRAVEL SAND SW Well-Graded SAND WITH More than 500/o < S % FINES SP Poorly-Graded SAND Retained on I SAND \lo. 200 Sieve SAND SW-SM Well-Graded SAND with silt WITH SW-SC Well-Graded SAND with clay BETWEEN More than S• 1% SANDl5% SP-SM Poorly-Graded SAND with silt I 0 f Coarse Fract io n FINES Passes SP-SC Poorly-Graded SAND with clay No. 4 Sieve SAND SM Silty SAND WlTH >IS % FINES SC Clayey SA~ FINE ML Inorgaruc SCL T with low plasticity GRAINED L1qwd l1m1t Cl Lean morgamc CLAY with low plasticity Less than SO I SOILS I SILT A.i'fD i OL Organic SJL T with low plasticlly CLAY I I I MH Elasuc morganic SILT wnb moderate to high plasttcny More than SO% I Liquid Lumt • Fat inorganic CLAY with moderate to high plasticity I Passes I SO or more No . 200 Sieve Organic Sll Tor CLAY with moderate to h1gb plasticity HIGHLY ORGANIC SOILS PEAT NOTES: (1) Soil descriptions are based on visual field and laboratory observauons using the classification methods described in ASTM D-2488. Where laboratory dara are available, classifications are m accordanc.: with ASTM D-2487. (2) Solid lines between soil desi.-riptions indicate a change m the interpreted geologic unit. Dashed lines indicate stratigraphic change wnh in the unit. (3) Fines arc matertal passing the U.S ~o. 200 Sieve . Unified Soil Classification System ( USCS) Dylan Short Plat P O Box'H5 1 Puy,1llup. WA 9is:;11 1909 Jones Avenue NE I Renton , Washington j Mam (253) 845-7()1)0 LI _____ W\_=_·_.,g_~'s.!ll _ _. -g-in_e_er_m_g_c,_,m _____ ___,_~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-,J~~:~~~~~~~~~~~---Project Nv . A-12 78 I July 2016 Figure-A-1 Ages Engineering, L LC ~ I Ages Engineering, LLC DATE 5 DATE 5 DATI s Test Hole TH-1 June 29, 2016 LOGGED BY BPK Soil Description Tan and oranp lilly SAND wall gravel, medium dm&e, moist. (SM) (Weathered Glacial Til) Tan sihy SAND with grave~ medium deme. moist . (SM) (Weathered Glacial Till) Becomes dense below 4 .0 feet . Test hole terminated at 5.5 feet below surface grades. No groundwater seepage encountered. Test Hole TH-2 June 29, 2016 LOGC,EDBY BPK Soil Description Tao and orange siky SAND wilh grawl. medium denee, mont. (SM) (Weathered Gllcm Till) Tan silty sand with graveL Found a large obstructX>n. Test hole terminated at 3 0 feet due to obstruction. No groundwater seepage encountered. Test Hole TH-3 June 29, 2016 LOGGED BY BPK Soil Description Tao and orange silty SAND with gravel, medium dense, moet . (SM) (Weathered Glacial TiD) Tan silty SAND with gravel, medium dense, moist . (SM) (Weathered Glacial Till) Becomes dense below 4 .0 feet. Test hole terminated at 5.5 feet below surface grades No ~roundwater seepage encountered. FIGURE A-2 M% M% M% PO Rox (),5 Puvallup. WA. 9!1.171 Office (25J 1 845· 7000 El.(V Notes Other EI.EV Notes Other ELEV Notes Other