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TECHNICAL INFORMATION REPORT for THE ENCLAVE AT BRIDLE RIDGE Preliminary Plat 14038156 1h Avenue SE Renton, Washington A. WAS o� U 5232 � j R 15T�R' C3� 4 DRS Project No. 13117 Renton File No. Owner/Applicant PNW Holdings LLC 9675 SE 36t" Street, Suite 105 Mercer Island, WA 98040 E Report Prepared by C"I %ED FEB 2 7 2014 D. R. STRONG Consulting Engineers, Inc. C'TY " e;-FIVTOM 6207 th Avenue Kirkland WA 98033 (425) 827-3063 Report Issue Date February 19, 2014 ©2014 D. R. STRONG Consulting Engineers Inc. TECHNICAL INFORMATION REPORT THE ENCLAVE AT BRIDLE RIDGE Preliminary Plat TABLE OF CONTENTS SECTION1.......................................................................................................................1 ProjectOverview..........................................................................................................1 Predeveloped Site Conditions......................................................................................1 DevelopedSite Conditions...........................................................................................1 Natural Drainage System Functions ..................... SECTIONIi....................................................................................................................10 Conditions and Requirements Summary ....................................................................10 SECTIONIII...................................................................................................................12 Off -Site Analysis.........................................................................................................12 SECTIONIV..................................................................................................................13 Flow Control and Water Quality Facility Analysis and Design ....................................13 Existing Site Hydrology (Pari A)..............................................................................13 Pre -developed Hourly Time Step Modeling Input: .................................................. 14 Pre -developed Hourly Time Step Modeling Output:-. ... I ...... I .............................. 14 Developed Site Hydrology (Part B).........................................................................16 Developed Site Area Hydrology..............................................................................16 Developed Hourly Time Step Modeling Output: ...................................................... 17 BYPASS Hourly Time Step Modeling Input. - ...........................................................18 BYPASS Hourly Time Step Modeling Output: ......................................................... 18 Performance Standards (Part C)................................................................................20 Flow Control System (Part D).....................................................................................20 Flow Control BMP Selection...................................................................................20 Flow Control Facility Design Output........................................................................21 Water Quality Treatment System (Part E)..................................................................27 SECTIONV...................................................................................................................29 Conveyance System Analysis and Design.................................................................29 SECTIONVI..................................................................................................................31 Special Reports and Studies......................................................................................31 SECTIONVII.................................................................................................................32 Other Permits, Variances and Adjustments................................................................32 ©2014 D. R, STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page i of ii Technical Information Report City of Renton SECTIONVlll................................................................................................................33 ESC Plan Analysis and Design (Part A).....................................................................33 SWPPS Pian Design (Part B).....................................................................................34 SECTIONIX..................................................................................................................35 Bond Quantities, Facility Summaries, and Declaration of Covenant ..........................35 Stormwater Facility Summary Sheet..........................................................................36 SECTIONX...................................................................................................................38 Operations and Maintenance Manual........................................................................38 List of Figures Figure1 TIR Worksheet...................................................................................................3 Figure2 Vicinity Map............................................................ ...................... ............ 6 Figure 3 Drainage Basins, Suhbasins, and Site Characteristics......................................7 Figure4 Soils...................................................................................................................8 Figure 5 Predevelopment Area Map..............................................................................15 Figure 6 Post Development Area Map...........................................................................19 Figure 7 Detention & Water Quality Facility Details.......................................................28 ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page ii of ii Technical Information Report City of Renton SECTION I PROJECT OVERVIEW The Project is the subdivision of two existing parcels zoned R4 (8.8 ac. total) into 31 single-family residential lots, per the City of Renton's (City) subdivision process. The Tax Parcel Numbers are 1423059122 and 1423059023. The Project location (Site) fronts on the east side of 156th Avenue SE (156th). The Project will meet the drainage requirements of the 2009 King County Surface Water Design Manual (Manual), as adopted by the City. PREDEVELOPED SITE CONDITIONS Total existing Site area is approximately 383,129 s.f. (8.795 ac). Total proposed Project area is 390,841 s.f. (8.972 ac), which includes 7,712 s.f. (0.177 ac) for the right-of-way frontage improvements on 156th Avenue SE. The Parcels are currently developed with one single-family residence, out buildings and a gravel driveway. The remainder of the Site is pasture, scotch broom, and scattered trees. The 8.807 acre parcel is situated on a slope that discharges runoff into one Threshold Discharge Area (TDA). However, the Site appears to have two Natural Discharge Areas (NDA). See the Level One Downstream Analysis for more information. For the purpose of hydrologic calculations, the entire Site is modeled as till forest. DEVELOPED SITE CONDITIONS The applicant is seeking approval to create 31 lots with lot sizes ranging from approximately 8,050 s.f. to 12,566 s.f. All existing improvements will be demolished or removed during plat construction. The 31 single-family residences combined with their driveways will create approximately 124,000 s.f. (2.847 ac) of impervious area. The proposed 53 -foot right of way will be improved with 26 feet of pavement, vertical curb, gutter, 8 -foot planter strip and 5 -foot sidewalk. The half street frontage improvements on 156th will consist of 22 feet of pavement (6' new), vertical curb, gutter, 8 -foot planter strip and a 5 -foot sidewalk. The improvements from right -of ways will add approximately 63,825 s.f. (1.465 ac) of impervious surface. The Project will result in a total of 4.788 ac of new impervious surfaces. The remainder of the developed Site (4.154 ac) will consist of landscaping and lawns. The Project is required to provide Basic Water Quality treatment and Level 2 Flow Control, per the 2009 KCSWDM (Manual). All surface water runoff from impervious surfaces will be collected and conveyed to a storm detention/water quality pond located in Tract "A". NATURAL DRAINAGE SYSTEM FUNCTIONS The Site topography slopes from the northeast corner of the Site to the southwest. The vegetation consists of pasture, scotch broom, and scattered trees. Site runoff travels southwesterly and sheet flows off the Site to the conveyance system in 156th A review of the SCS soils map for the area (see Figure 4, Soils) indicates Alderwood gravelly sandy loam with 6 to 15 percent slopes (AgC). Per the Manual, this soil type is classified as "Till" material. The SCS Soil series descriptions follow Figure 4. ©2014 D, R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 1 Technical Information Report City of Renton In evaluating the upstream area, we reviewed King County iMAP aerial topography and imagery and conducted field reconnaissance to evaluate conditions and potential problems. The upstream area for the Site is approximately 3.35 acres, entering the Site in from the northern and eastern property lines. The upstream area appears to be forested and generating negligible runoff. The potential need for a bypass system will be assessed at final engineering. 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 2 Technical Information Report City of Renton FIGURE 1 T1R WORKSHEET King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner. PNW Holdings LLC Address/Phone: 9676 SE 36" Street, Suite 105 Mercer Island, WA 98040 Project Engineer: Maher A. Joudi, P.E. D. R. STRONG Consulting Engineers Inc. Address/Phone: 6207 th Avenue Kirkland WA 98033 (425) 827-3063 Part 3 TYPE OF PERMIT APPLICATION ® Subdivision ❑ Short Subdivision ® Clearing and Grading ❑ Commercial ❑ Other: Part 2 PROJECT LOCATION AND DESCRIPTION Project Name: The Enclave at Bridle Ridge Location: Township: 23 North Range: 05 East Section: 14 Part 4 OTHER REVIEWS AND PERMITS LJ DFW HPA U Management ❑ COE 404 ❑ ❑ DOE Dam Safety ❑ ❑ FEMA Floodplain ❑ ❑ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community: Newcastle Drainage Basin Lower Cedar River Shoreline Rockery Structural Vault Other: ©2094 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 3 Technical Information Report City of Renton Part 6 SITE CHARACTERISTICS ❑River: ❑ Floodplain ❑ Wetland ❑ Stream: ❑ Seeps/Springs ❑ Critical Stream Reach ❑ High Groundwater Table ❑ Depress ions/Swales ❑ Groundwater Recharge ❑ Lake: ❑ Other: ❑ Steep Slopes Part 7 SOILS Soil Type: Slopes: Erosion Potential: Erosive Velocities: Alderwood 6-15% Slight Slow (AgC) ®Additional Sheets Attached: SCS Map and Soil Description, Figure 4 Part 8 DEVELOPMENT LIMITATIONS REFERENCE ® Level 1 Downstream Analysis ® Geotechnical Engineering Study ❑ Environmentally Sensitive Areas ❑ Level 2 Off -Site Stormwater Analysis ® Level I Traffic Impact Analysis ❑ Structural Report ❑ Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION ®Sedimentation Facilities ®Stabilized Construction Entrance ®Perimeter Runoff Control ®Clearing and Grading Restrictions ®Cover Practices ®Construction Sequence ❑ Other LIMITATION/SITE CONSTRAINT None MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION ®Stabilize Exposed Surface ®Remove and Restore Temporary ESC Facilities ®Clean and Remove All Silt and Debris ®Ensure Operation of Permanent Facilities ❑Flag Limits of SAO and open space preservation areas ❑ Other ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat . Page 4 Technical Information Report City of Renton Part 1 D SURFACE WATER SYSTEM U Grass Lined Channel ® Pipe System ❑ Open Channel ❑ Dry Pond ® Wet Pond U Tank ❑ Vault ❑ Energy Dissipater ❑ Wetland ❑ Stream U Infiltration ❑ Depression ❑ Flow Dispersal ❑ Waiver ❑ Regional Detention Method of Analysis: KCRTS Compensation/Mitigatio In of Eliminated Site Storage N/A Brief Description of System Operation: Runoff from impervious surfaces will be collected and conveyed to the detention facility. From there it will be discharged to the conveyance system in 156th Avenue SE. Facility Related Site Limitations: Reference Facility Limitation Part 11 STRUCTURAL ANALYSIS U Cast in Place Vault ® Retaining Wall ❑ Rockery > 4' High ❑ Structural on Steep Slope ❑ Other: Part 12 EASEMENTS/TRACTS P9 Drainage Easement ❑ Access Easement ❑ Native Growth Protection Easement ® Tracts ❑ Other: Part 13 SIGNATURE OF PROFESSIONAL ENGINEER or a civil enineer under my supervision have visited the Site. Actual Site conditions as observed ere incorporated into this worksheet and the attachments. To the best of my know)�CI' information provided here is accurate. Sicined/Date ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 5 Technical Information Report City of Renton FIGURE 2 VICINITY MAP 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle fudge Preliminary Plat Page 6 Technical Information Report City of Renton 0 W-IRD PL SE 13MI FL 5E taaT#1 P �T#1 SE 4TH Sr ` SE R ` f" SE 5TH ST SE E39TFl PL SL 5TH ®L M t'idTkPL SITE . {� s l�rr�p st► SE 6TH sT ssIDST 1 sE 14+Tii sr sF S" SE 1�TH R. ifI Ki _ -$E 14TN PL SE 149T) Cedar River- { 3y FJ The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle fudge Preliminary Plat Page 6 Technical Information Report City of Renton FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS (�)2094 O, R. STRONG Consulting Engineers Inc, The Enclave at Bridle Ridge Preliminary Plat . Page 7 Technical Information Report City of Renton Ez6z'Lzmwpz p E9Qf'LZB'9z6 Q EE686 VM 'QNV7Narx 3nN3/I b U7L -W9 IHOd3N NOI1 VkVcYOdNI 7VOINHO31 5 ti 0. z SNOA AYnS Si3NNb7d Stf33N1JN3 dVPV SNISb$ 39VNIIVNO o aw w T z r, � 2 h � SN33NfVN-q VIV L 7nSNOO ONOWS WIO a 30OIhf 37QIbf31 d 3/1 V70N3 3H1 o ti r- o o 0 � C� R Q a U co IL F ti 0. z o � aw w T h � INZ L w Q a U co o ~ co 00 4 a C.7 ` o 0CL Nt Q Z N v Z� �J �n� � ,C rt a a �I a� Q � a a � 4i" is w h 4:'` :5'_;�rI� h F - FIGURE 4 SOILS -%iF ASap -King Cour' Area. 'Nashington i t h fUAJJ xiiGU 1 �3 �J'�ti'1: :f{'�V: !,Lb au fy. N, o -M 40 w EM F:a hL��l-r'j�5-�1:VM�hfd: tr Cul r�'�cucid =4'i v€-7 TLty ii, TM 7uo I Lgi Ve,77-1 4.1 2es]f y F4 i } a 4T1 3'3J 4 .)2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 8 Technical Information Report City of Renton AgC—Alderwood gravelly sandy loam, 6 to 15 percent slopes Map Unit Setting Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 48 to 52 degrees F Frost -free period: 180 to 220 days Map Unit Composition Alderwood and similar soils: 95 percent Minor components: 5 percent Description of Alderwood Setting Landform: Moraines, till plains Parent material. Basal till with some volcanic ash Properties and qualities' Slope: 6 to 15 percent Depth to restrictive feature: 24 to 40 inches to dense material Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0. 00 to 0.05 in/hr) Depth to water table: About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water capacity: Very low (about 2.5 inches) Interpretive groups Land capability (nonirrigated): 4s Typical profile 0 to 12 inches: Gravelly sandy loam 12 to 27 inches: Very gravelly sandy loam 27 to 60 inches: Very gravelly sandy loam Minor Components Norma Percent of map unit.- 1 percent Landform: Depressions Bellingham Percent of map unit: 1 percent Landform: Depressions Seattle Percent of map unit. 1 percent Landform: Depressions Tukwila Percent of map unit: 1 percent Landform: Depressions Shalcar Percent of map unit: 1 percent Landform: Depressions 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 9 Technical Information Report City of Renton SECTION li CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 — Discharge at the Natural Location: Runoff will discharge at the natural location. • C.R. #2 — Offsite Analysis: Analysis is included in Section III. The Analysis describes the Site's runoff patterns in detail. • C.R. #3 — The Project is located in the Level 2 Flow Control area. A detention pond will provide flow control as required. The Project is required to match durations for 50% of the two-year peak flow up to the full 50 -year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2 -year and 10 -year and 100 -year return periods (KCSWDM, Sec. 1.2.) Furthermore, the Project must meet the Flow Control BMP requirements as specified in Section 1.2.3.3 of the Manual. The project may utilize splash blocks for basic dispersion, pervious pavement, or other BMP's found in Appendix C of the Manual for a portion of the impervious area on each lot. • C.R. #4 -- Conveyance System: New pipe systems and ditches/channels are required to be designed with sufficient capacity to convey and contain (at minimum) the 25 -year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures and ditches/channels may overtop for runoff events that exceed the 25 -year design capacity, provided the overflow from a 100 -year runoff event does not create or aggravate a "severe floodingrp oblem" or "severe_ erosion -problem" as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100 - year event must discharge at the natural location for the project Site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. The proposed conveyance system was analyzed using the KCBW program, and is capable of con,7ing the 100 -year- 1L pea_ storm without overtopping any structures or channels: -This analysis will --be---- performed -b -_performed at time of construction plan preparation. • C.R. #5 — Erosion and Sediment Gon rro-F7 ie protect prov+�es-lie nine minimum ESC measures. • C.R. #6 — Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual will be included in Section X at the time of construction plan preparation. • C.R. #7 — Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and Site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 10 Technical Information Report City of Renton two-year period following posting of the drainage defect and maintenance financial guarantee. • C.R. #8 — The Project is located in the Basic Water Quality Treatment area. The combined detentionlwetpond facility will accommodate this requirement. • S.R. #`! — Other Adopted Area -Specific Requirements: Not applicable for this Project. • S.R. #2 — Floodplain/Floodway Delineation.- Not applicable for this Project. • S.R. #3 — Flood Protection Facilities: Not applicable for this Project. • S.R. #4 — Source Control: Not applicable for this Project. 02014 D. R. STRONG Consulting Engineers Inc_ The Enclave at Bridle Ridge Preliminary Plat Page 11 Technical Information Report City of Renton SECTION III OFF-SITE ANALYSIS An offsite Level One Downstream Analysis was prepared by D.R. STRONG Consulting Engineers Inc. and is included in this Section. 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 12 Technical Information Report City of Renton LEVEL ONE DOWNSTREAM ANALYSIS for THE ENCLAVE AT BRIDLE RIDGE Preliminary Plat 14038 16611 Avenue SE, Renton, Washington DRS Project No. 13117 Renton File No. LUA XXXXXX OwnedApplicant PNW Holdings LLC 9675 SE 36th Street, Suite 105 Mercer Island, WA 98040 Report Prepared by r� D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue NE Kirkland WA 98033 (425) 827-3063 Report Issue Date February 20, 2014 02014 D. R. STRONG Consulting Engineers Inc. LEVEL ONE DOWNSTREAM ANALYSIS THE ENCLAVE AT BRIDLE RIDGE TABLE OF CONTENTS TASK 1 DEFINE AND MAP THE STUDY AREA.........................................................2 TASK2 RESOURCE REVIEW.....................................................................................6 TASK 3 FIELD INSPECTION.....................................................................................16 Upstream Tributary Area............................................................................................16 General Onsite and Offsite Drainage Description......................................................16 8 TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS -117 Drainage System Description....................................................................................17 .............................................. Downstream Path TDA .............................................. ..17 TASK 5 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS .........................19 APPENDIXA.................................................................................................................21 APPENDIXB.................................................................................................................26 List of Figures Figure1. Vicinity Map......................................................................................................3 Figure2. Site Map...........................................................................................................4 Figure 3. King County iMap Topography.........................................................................5 Figure 4. Streams and 100 -Year Floodplains and Floodway...........................................7 Figure 5. King County iMap Wetlands. ............................................................................. 8 Figure 6. King County iMap Erosion Hazard Areasgs.....................................................9 Figure 7. King County iMap Landslide Hazard Areas....................................................10 Figure 8. King County iMap Seismic Hazard Areas.......................................................11 Figure 9. FEMA — Flood Insurance Rate Map................................................................12 Figure 10. King County iMap Drainage Complaints.......................................................13 Figure 11. USDA King County Soils Survey Map..........................................................14 Figure 12. Downstream Table........................................................................................22 Figure 13. Downstream Map..........................................................................................25 02414 U R. STRONG consulting Engineers Inc. Page 1 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton DISCLAIMER: THIS REPORT WAS PREPARED AT THE REQUEST OF PNW HOLDINGS, LLC FOR THE 8.807 ACRE PARCELS KNOWN AS A PORTION OF THE SOUTHEAST QUARTER OF SECTION 14, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, TAX PARCEL NUMBERS 1423059122, 1423059023 (SITE). D. R. STRONG CONSULTING ENGINEERS INC. (DRS) HAS PREPARED THIS REPORT FOR THE EXCLUSIVE USE OF DRS, THE OWNER, AND THEIR AGENTS, FOR SPECIFIC APPLICATION TO THE DEVELOPMENT PROJECT AS DESCRIBED HEREIN. USE OR RELIANCE ON THIS REPORT, OR ANY OF ITS CONTENTS FOR ANY REVISIONS OF THIS PROJECT, OR ANY OTHER PROJECT, OR BY OTHERS NOT DESCRIBED ABOVE, IS FORBIDDEN WITHOUT THE EXPRESSED PERMISSION BY DRS. TASK 1 DEFINE AND MAP THE STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2009 King County Surface Water Design Manual (Manual). The Site is located at 14038 156th Avenue SE in Renton, Washington, See Figure 1, Figure 2, and Figure 3 for maps of the study area. 02014 D. R. STRONG Consulting Engineers Inc. Page 2 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 1. VICINITY MAP g3FM Pi, ,xrt, SS st ot 'WIarpp*PL Site '% Lflixi t+r, # 3 ittl 'r •., a SE �fftf ST SR d S'+Nr1St F SF I�R45i �e SE 3A7iiCd %P; s t �' P•SE t* Th [v d S� 71HiM A4 '� w � J` e. erre ar h$? _ ,, wt The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information" King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Q2014 D. R. STRONG Consulting Engineers Inc, page 3 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 2, SITE MAP ©2014 D. R. STRONG Consulting Engineers Inc. page 4 Leve! One Downstream Analysis The Enclave at Bridle fudge City of Renton Uzre'[zeszr d caoetzasat o CUM V CNc-7xa1H 3nWAYWI - oas 69096 VM 'NO1N38 n sao c3nans Sa3NNtRd Sa33N1OV3 39 3nN3AV 141996 90kb o r o LO w J < O dVPV 31 IS = " O S833NION3 JNI17nSNOJ S a a 300I4Y 37014181 h'.9AV70N3 3H1 z r JN02l15 Wo O Q 4 Q 4 Li ti z_ O N N a � a z � w ILU r o z J < O i-- LL CDN O I 00 r V o� z Z Z � r n 0 a o Q a � Q V r7 Z _U r m � a V n f rl O N FIGURE 3. KING COUNTY EMAP TOPOGRAPHY Legend No Highlighted Feature Highways Lakes and Large Rivers _1 11— 1 County Boundary Streets r,;=' Streams X Mountain Peaks rflghvm Contours (5ftdark) w,t. 1en:�oa 1GD7 LocA other Parcels 02014 D. R. STRONG Consulting Engineers Inc. Page 5 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton TASK 2 RESOURCE REVIEW • Adopted Basin Plans: Lower Cedar River Basin and Nonpoint Pollution Action Plan was adopted in July 1998. • Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 9. • Other Offsite Anaiysis Reports: None available at this time. • Sensitive Areas Folio Maps: See Figures 4-8 for documentation of the distance downstream from the proposed project to the nearest critical areas. Included, are sections of the King County Sensitive Areas Folio which indicate the following. • Figure 4 Streams and 100 -Year Floodplains and Floodway: There is a Class 1 and Class 3 Stream within one mile of the Site along the downstream path. A 700 -year floodplain is within one mile of the Site. • Figure 5 Wetlands: There are no mapped Wetlands within one mile of the Site along the downstream path. • Figure 6 Erosion Hazard: There are mapped Erosion Hazard Areas within one mile of the Site along the downstream path. • Figure 7 Landslide Hazard: There are mapped Landslide Hazard Areas within one mile of the Site along the downstream path. • Figure 8 Seismic Hazard: There are mapped Seismic Hazard Areas within one mile of the Site along the downstream path. • DNRP Drainage Complaints and Studies: As shown in Figure 10, there are drainage complaints within 1 mile of the Site along the downstream path. • Road Drainage Problems: None noted. • USDA King County Soils Survey: See Figure 11. • Wetlands Inventory: The wetland inventory revealed no additional wetlands within the downstream path. • Migrating River Studies: None are applicable to the site. • Washington State Department of Ecology's latest published Clean Water Act Section 303d list of polluted waters: None listed along the downstream path. • King County Designated Water Quality Problems: None at this time. • Adopted Stormwater Compliance Plans: City of Renton Storm Water Management Plan, King County 2013 Stormwater Management Plan • Basin Reconnaissance Summary Reports: Cedar River Current and Future Conditions Report (April 1993) ©2014 D. R. STRONG Consulting Engineers Inc. Page 6 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 4. STREAMS AND 100 -YEAR FLOODPLAINS AND FLOODWAY �,v� PL -T ,� 9E •,,I L $"N ST 3E UTM w - .� t�'Y 3 SF Sp, R 5( IlR4 ✓� Site v W 4• Y -+a' J in ; . t�i, � / 3,' � fir' ry?t 1�Ce10 rl:r. } 1AS, Renton Le W nd Highlighted Feature SAO Straarn t _I County Boundary cum a X Mountain Peaks Cbn2p6'aRn a: Highways CIms3 b Streets Cltws 1 liaghyvar �Inc°>,rsiat,ad a,r1J Lakes and Large Revers Streams Parcels Floedwaiy 100 Year Floodplain Shaded ROO ©201417. R. STRONG Consulting Engineers Inc. Level One Downstream Analysis The Enclave at Bridle Ridge lz� r+TTl W tiF SxkTIe ST o� 3 9 RfNf': Page 7 City of Renton FIGURE 5. KING COUNTY IMAP WETLANDS Highlighted Feature County Boundary X Mountain Peaks Highways Streets Il ighway (Cont) Legend Ladd Pamals Lakes and Largo Rivers 5tre a ms SAO Wetland i r.` ss sm sr �19Itl PE � ����-1411+-�L scar« st L s' xi�n,R d k , frt,sr r d x 7 9 trscry sr 4 !r A - Y Y G � wrH0. L ... .... .. - —.. 3 *� � 1 x x Ott e� k w A V Sfi M'.11ti `aT R 'r��'. li%ff i3V4?I a ti ...- „Q Y �b �•,e�H$r SY AFJIf..yI.y+PiC'r; du.�LE � r _ � : z Highlighted Feature County Boundary X Mountain Peaks Highways Streets Il ighway (Cont) 02014 D. R. STRONG Consulting Engineers Inc. Page 8 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton Legend Ladd Pamals Lakes and Largo Rivers 5tre a ms SAO Wetland 02014 D. R. STRONG Consulting Engineers Inc. Page 8 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 6. KING COUNTY IMAP EROSION HAZARD AREAS on Highlighted Feature 11— 1 County Boundary X Nlountain Peaks Highways streets ki g war {cont) E 4� SER[Mi �vlin4 till q�C SE tNr>a �i IT i 3E 1Vf .� F A 31.31n y � d � � SE n1/1 ... d F A LClsrP., �- i 8 A sc�ga ri T =zrfosr a yen sr stu,pt 4 � uunr:r kY r x . � � e SIB. Np[- - y gS+51 T. ST Ho- - i� . c i C.e rlar River ' ly WMA" G i-...." A', Y i %E HEN row "A on Highlighted Feature 11— 1 County Boundary X Nlountain Peaks Highways streets ki g war {cont) Legend . Arfarufs Laval Parcels Lakes and Large Rivers Streams SAO Erosion ©2014 D. R. STRONG Consulting Engineers Inc. Page 9 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 7. KING COUNTY EMAP LANDSLIDE HAZARD AREAS ."��,,,, � a; ^meq E� .. .. _ . •' . - - Sqi � - �� r rIL t r l/ .O. %'�/ /� '/, /•. �`� k � � SEr � r / - 3k RLN r'vN-1JM Legend 99 Highlighted Feature Ailarmh 9m ST Wcal 1VRI Ot . p °.L 5m ft Rarcals Flighways ❑ Lakes and Large Rivers Streets r.,i Strearns IiNft xy O SALT Landslide f cont) ST p f� ,-eary�ST , Sy, ~a" a K= 1 SE taRa ST '9 Wam i+ �.. SC 45Th sT 40,'F ST r � r a 7 r, x � ."��,,,, � a; ^meq E� .. .. _ . •' . - - Sqi � - �� r rIL t r l/ .O. %'�/ /� '/, /•. �`� k � � SEr � r / - 3k RLN r'vN-1JM 02014 D. R. STRONG Consulting Engineers Inc. Page 10 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton Legend 99 Highlighted Feature Ailarmh ) County Boundary 11— Wcal x Mountain Freaks Rarcals Flighways ❑ Lakes and Large Rivers Streets r.,i Strearns IiNft xy O SALT Landslide f cont) 02014 D. R. STRONG Consulting Engineers Inc. Page 10 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 8. KING COUNTY [MAP SEISMIC HAZARD AREAS si�ral.3 sa rMn W IV} A a s _ H. w -4. A41 xerr ST .. IN N \ffln �1'•,� __ �.1�4,\\\\�\ w\� ♦w \ \ k ' iC '�C srr:.77 ie � ���\�\ ♦�'� ..._ ` s�x".,LC' i1A goHighlighted Feature i i County Boundary Mountain Peaks Highways Streets Higbycry (cont) 02014 D. R_ STRONG Consulting Engineers Inc. Page 11 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton Legend Aitarmis La.rN Parcels 1 Lakes and Large Rivers Streams SACS Seismic 02014 D. R_ STRONG Consulting Engineers Inc. Page 11 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton FIGURE 9. FEMA - FLOOD INSURANCE RATE MAP ONE A9 \F 1. ©2014 D. R. STRONG Consulting Engineers Inc. Page 12 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton r�c LEGEND SI'C(.M. 11001)) :i'.:�Zjlt �l ,�!tE�S »1L!rai2.)€Eil !n' 7!tiF�'6'.k iR(iCdJ 1 ZONE A �,..I.nr .1.::,1 ..,...q::•m d..•. rr_:.:t. ZONE AE ZONE AH :<7 4k-;nl+ . I i•r r.i{Ir ZONE AO II; ::I 4v:t, .N.-.nnr'i rr: •-.l. I'. -.r .'i.:li r;r elk Jilwv ZONE A99 r^ ;u-:iv':•:i !a .. ,..f ;• ZONE tit E»z,t-d .r.l::, r r�«:r,.+I :�]�,.:.: rr.•r.lr±sr r., '<I ZONE VE 1,.:.: r,:l rl.. Fi . W"— F!OOt)Lh':iY 1RC S IN 7()17 1C CTNER !"i V()D 4K -A5 ZONE % A'+: + ,•t u ii.:A� A L Arra ndn J: reh> al ,.. (J ER ai{E45 r :. ZOO NE K lxiµy�n. u ZONE A .re:4l•r.�::rr rw'rE ©2014 D. R. STRONG Consulting Engineers Inc. Page 12 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton r�c FIGURE 10. KING COUNTY IMAP DRAINAGE COMPLAINTS 02014 O. R. STRONG Consulting Engineers Inc. Page 13 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton ............ .•i SC (M Lt 4i IYfh 5 E6,NTiq � YAC �r3grrSR A ffi Irir si �:. �- z geaufsi SI ". S. LL Xtri,V ,,rs�rs a � � Y Rd _ 6 R i rp• aE resit. sr .. G C-IIJr Rivo, - M w I j rfgr,i� - Logend 84i�ctod Porcolls Virwxp t _j County Souridatsr aT+ X Mountain Paalca HI WAIYS Far�nfa Incarpnratod Area Li t.akos anif Largs lklvora Streets r, 5trearni Qre rnags Complaints (cont] 02014 O. R. STRONG Consulting Engineers Inc. Page 13 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton k:' .04TN ♦t" -e 7rT h FIGURE 11. USDA KING COUNTY SOILS SURVEY MAP x Sail Mag-4Cing Ccrun_y „r�EJ, Washingtw ra iy `y R.p SxAe: 1::,I X f p ku:] ❑ i A'N'4d ; z?.r z 13") :f+� 1-I N fi `_Ff fel Xt1 Xk A" M.}I Fr-,yLis)7 VOA, MOA- MGS&t f r A- J -,"A iare'CN '6 51 aP 29q7 v 4�', �e w, 3 (D2014 Q. R. STRONG Consulting Engineers Inc. Page 14 Level One downstream Analysis The Enclave at Bridle Ridge City of Renton AgC—Alderwood gravelly sandy loam, 6 to 15 percent slopes Map Unit Setting • Elevation: 50 to 800 feet • Mean annual precipitation: 25 to 60 inches • Mean annual air temperature: 48 to 52 degrees F • Frost -free period: 180 to 220 days Map knit Composition • Alderwood and similar soils: 95 percent • Minor components: 5 percent Description of Alderwood Setting • Landform: Moraines, till plains • Parent material: Basal till with some volcanic ash • Properties and qualities • Slope: 6 to 15 percent • Depth to restrictive feature: 24 to 40 inches to dense material • Drainage class: Moderately well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 18 to 37 inches • Frequency of flooding: None • Frequency of ponding: None • Available water capacity: Very low (about 2.5 inches) Interpretive groups • Land capability (nonirrigated): 4s Typical profile • 0 to 12 inches: Gravelly sandy loam • 12 to 27 inches: Very gravelly sandy loam • 27 to 60 inches: Very gravelly sandy loam Minor Components Norma • Percent of map unit: 1 percent • Landform: Depressions Bellingham • Percent of map unit, 1 percent • Landform: Depressions Seattle • Percent of map unit: 1 percent • Landform: Depressions Tukwila • Percent of map unit: 1 percent • Landform: Depressions Shalcar ■ Percent of map unit: 1 percent • Landform: Depressions 02014 D. R. STRONG Consulting Engineers Inc. Page 15 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton TASK 3 FIELD INSPECTION UPSTREAM TRIBUTARY AREA In evaluating the upstream area, we reviewed King County iMAP aerial topography and imagery and conducted field reconnaissance and have concluded that upstream tributary area for the Site is negligible. The areas north and east of the Site produce southwesterly flowing runoff that may enter the Site. This runoff flows over densely vegetated areas and is considered negligible. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTION The 8.81 acre parcel is encompassed within one Threshold Discharge Area (TDA) with two natural discharge areas (NDA 1, NDA 2). Runoff is conveyed as sheet flow southwest across the property through dense vegetation and pasture and is directed towards the southwest corner of the Site. From there a concrete pipe inlet conveys water west to a catch basin at the southwest corner of the Site on the east side of 156th Avenue SE. Runoff continues south in the conveyance system then flow is directed west as pipe flow at the intersection of 156th Avenue SE and SE 144th Street. Runoff continues west across 154th Place SE and outlets to Stewart Creek, a Class 3 stream. This creek outlets to the Cedar River which eventually outlets to Lake Washington approximately 5.5 miles northwest of the Site. The Site's second natural discharge point (NDP) is approximately 237' east of NDP 1. Runoff exits the Site as sheet flow and converges with NDA 1 at Point B. Runoff from the developed Site will be collected and conveyed by a typical catch basin/ pipe network to a detention pond in the southwest corner of the Site. The pond will discharge to the conveyance system in 156th Avenue SE. 02014 D. R. STRONG Consulting Engineers Inc. Page 16 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in the Downstream Map and Downstream Table located in Appendix A. The downstream area is located within the Cedar River basin; more specifically the Lower Cedar River sub basin. The downstream area was evaluated by reviewing available resources, and by conducting a field reconnaissance on January 16, 2014 under overcast/foggy conditions. Located within the TDA are two Natural Discharge Areas (NDA), NDA 1 and NDA 2. NDA 1 exits the Site approximately 230' east of the southwestern property corner. Runoff continues as sheet flow for approximately 230' over native vegetation and pasture until it enters a 12 -inch concrete pipe inlet where it continues as pipe flow into a catch basin in 156th Avenue SE. NDA 2 exits the Site approximately 150' west of the southeastern property corner. Runoff sheet flows west along the southern property line over native vegetation and pasture and converges with NDA 1 at the 12 -inch concrete pipe at the southwest corner of the Site. Downstream Path NDA 9 Point "Al" is the natural discharge point of NDA 1. Runoff is conveyed west across the southern property line as sheet flow and directed towards a concrete pipe inlet at the southwest corner of the Site (±D). From Point "Al" to Point "131", runoff heads west as sheet flow to a 12 -inch diameter concrete pipe (±0'-223'). Point "131 ", concrete pipe inlet at the southwest corner of the Site (±223'). From Point "131" to Point "Cl", runoff heads west as concentrated flow to a 12 -inch diameter concrete pipe (±223'-230'). Point "Cl", runoff enters a Type 1 catch basin located on the east side of 156th Avenue SE (±230'). From Point "Cl" to Point °D1", runoff heads south as pipe flow via an 18 -inch diameter plastic pipe. Trickle flow observed (±230'-475'). Point "Dl", runoff enters a Type 1 catch basin on the east side of 156th Avenue SE (±475'). From Point "D1" to Point "E1", runoff heads west as pipe flow via an 18 -inch plastic pipe. Trickle flow was observed (±475'-507'). Point "E1", runoff enters a Type 1 catch basin located on the west side of 156th Avenue SE (±507'). From Point "E1" to Point "F1", runoff heads south as pipe flow via an 18 -inch diameter plastic pipe. Trickle flow was observed (±507'-691'). 02014 D. R. STRONG Consulting Engineers Inc. Page 17 Level one Downstream Analysis The Enclave at Bridle Ridge City of Renton Point "171", runoff enters a Type 1 catch basin located on the west side of 156th Avenue SE (±691'). Runoff continues south as pipe flow via an 18 -inch diameter plastic pipe for approximately 192' where it enters either a buried catch basin or tees into another drainage pipe heading west at the intersection of 156th Avenue SE and SE 144th Street. Field investigation found no catch basin at this intersection, but according to City of Renton's GIS maps, stormwater runoff is directed west at this intersection. Runoff proceeds west as pipe flow for approximately 665' where it reaches the east side of 154th Place SE. It continues as pipe flow for approximately 55' across 154th Place SE. Then it heads southwest as pipe flow for approximately 157' where it outlets to Stewart Creek. Runoff continues approximately 2,470' south down this stream until it outlets to Cedar River, which eventually outlets to Lake Washington approximately 5.5 miles northwest of the Site. Downstream Patin NDA 2 Point °A2", is the natural discharge point of NDA 2 (±0'). From Point "A2" to Point "131", runoff heads west as sheet flow and converges with NDA 1 at Point °B1" (±0'-471'). ©2014 D. R. STRONG Consulting Engineers Inc. Page 18 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton TASK 5 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division — Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths revealed six complaints within the last ten years. Drainage investigation reports attached in Appendix B (see table on page 20). Project runoff from the TDA will be collected and released per the Manual's requirements to accommodate Level 2, Conservation Flow Control and Basic Water Quality requirements. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction. The project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. 02014 D. R. STRONG Consulting Engineers Inc. Page 19 Level one Downstream Analysis The Enclave at Bridle Ridge City of Renton Complaint Parcel Summary Recurring Type Required number Mitigation 2006-0069 2323059123 Ditch design No 1 None, property flaw causes is on opposite water to flow side of river upstream and back up, flooding pasture and outbuildings 2008-0507 2323059123 Fallen tree 2' No NIA None, property down of is on opposite Madsen creek side of river bypass drainage culverts catching and stopping debris, Will dam up and cause more flooding 2008-0700 2323059123 Over topping of Not since 1 None, property bypass channel 1212006 is on opposite and flooding analysis side of river onto property 2009-0071 2323059205 Flooding due to No 1 None an improperly installed culvert. 2009-0653 2323059133 Old water tank No NIA None in river emitting some fumes that is killing the vegetation above 2011-1008, 232305HYDR Illegal dumping No N/A None of two television sets at SE Jones Rd and 254'" PI 02014 D. R. STRONG Consulting Engineers Inc. Page 20 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton APPENDIX A. OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE & DOWNSTREAM MAP 42014 D. R. STRONG Consulting Engineers Inc. Page 21 Level One Downstream Analysis The Enclave at Bridle Ridge City of Renton J m a F- LU z a 7! A r_ V cc m L — E O C a Q7 -0 O` � N L _ o ow m w aj r o o ❑ ❑ w w ■ o > > m m Y 13� O 0 C m LU LU o 0 O L ,v 3 m m j LU U ��`p m O O LL LL-2 LJL O O w LU 0 o Y 7 u n m t u- � � 0 � ; §j /§ ■ ui - \ / 0 ± UJ \ \ j \ ] < z j > LL, m Lue § § z U) § 2 \ \ ƒ E \ I § j \ § r CL / § § z { LL § ° \ § ¥ e E) LL LL \\ §\§ z / §§qi } } \ u§ u 8 u e \ z k / z z S § j $ � 7 UJ LU k z \ z \ z + ) LO + %F \ z— w § ) L § \ z_ \ s ) 9 ) 9 L z z \ k a k = o / § $ 2 \ 0 0 \ Cf) E E 3 §j /§ ■ 7 2 Al k (D G2 2 \ 2 ) \\ /E 2 o \ . .E \ \ \ 4-- a = 0 k\ cnf § @ co v \k 0 // f § ) > a o § E ƒ k \ / / a = ƒ a- a_ 2 * ƒ_ § / IL _ z z oas\ k J z ¢ - � S / 0 ( / _ . _ 0 Ln \ § § LU > } 5\=f z§ ƒ§ \ 7 7 § z § _0 z o $ ® / / to & « - \ Lnk/ \ �¢� / o $ < , ®® < k /\ ) f } 2 LU J E c 2 E .9 \ o \ 2 e *§ E cu f / ] // 14 > j z \ / 03 § / § \ § { m a > \ j Cu i ? \ \ cl § a z \ \ / \ \ z CL m ( / w z e u w \ q-- a CD~ LLI \ � § § k f m \b % / di to \ / ƒ E o} 3: ® /E % f \P j « / m _ D < k FIGURE 13, DOWNSTREAM MAP ©2014 D. R. STRONG Consulting Engineers Inc. Page 25 Level One Downstream Analysis 156th Avenue Assemblage Preliminary Plat City of Renton APPENDIX B. DRAINAGE INVESTIGATION REPORTS 02014 D. R_ STRONG Consulting Engineers Inc. Page 26 Level One Downstream Analysis 1561h Avenue Assemblage Preliminary Plat City of Renton ©2014 D. R. STRONG Consulting Engineers Inc. Page 27 Level One Downstream Analysis 1561" Avenue Assemblage Preliminary Plat City of Renton U SF 4N rt sEm4sT 4 S i QE Sfa ST .g 13AT14 PL `e $E IATN a SE 7r.4 a ... .. L 5E HT" ST. y,7. ST . _ St 144M sr- j ... 2009-0653 SE 2009-0071 s SIP U S� F�Eir Cedar River__ 1f r 200670069 } Zoos-o5o7 2008-0700 I*r,,&,20.1-1008 ,, ©2014 D. R. STRONG Consulting Engineers Inc. Page 27 Level One Downstream Analysis 1561" Avenue Assemblage Preliminary Plat City of Renton King County Department of Natural Resources and Parks k1gWater and Land Resources Division DRAINAGE INVESTIGATION REPORT FIELD INVESTIGATION FILE NO.: 2091-1008 ADDRESS.SE Jones Roadand 254th Place, Renton, 98058 NAME: PHONE: Jennifer Vanderhoof 206.263.6533 DATE OF INVESTIGATION; 11-10-2011 INVESTIGATED BY: Virgil Pacampara I went to the site on 11/10/2011 at 1:00 PM and investigated an illegal dumping. The complaint was about dumping of two large television sets at the end of the roadway, right in front of a road block sign that says "No Dumping". saw the two television sets at the edge of a turn -around arealculdesac of 149'" Ave. SE. I spoke to Mr. Billy Emerson, the property owner of house # 1506 149`t' Ave. SE. about the alleged illegal dumping. He told me that the dumping appeared to have happened during late night, and noticed it the following day. That he installed the "No Dumping Sign' to eliminate the illegal dumping an the site, but it appears that people still dumped stuff on the site. It appeared that the spot of the dumping is located within the road right of way of King County. I gave him our business card to call us incase it happens again. He gave his and his wife's phone numbers (his 206.661.3432; Patti- 360-990-6617 ) for the records. I went to the other site as indicated an the complaint reportsle-mail. The second site is the location of a regional facility (DR0535). The site is along the paved walking trail that is parallel and north side of 1-169 (between 149th Ave. SE and 150'' Lane SE.). I did not see any illegal dumping on the site particularly along the north end of cross culvert (concrete box culvert) and on the Swale. spoke to Sandra of KC Roads emergency number (206.296.8100) on afternoon of 11118;2011 , and reported the result of the investigation. Sandra told me that the KC -Roads will take care of the complaints and will remove the televisions on the site. This is the first site where the two television was allegedly dumped illegally along the road right of way. A "No Dumping" sign was installed by Mr. Emerson to eliminate illegal dumping it stili re-occuring. This is the second site. I did not see any illegal dumping on the site. The site is a regional facility. w k King County Department of Natural Resources and Parks Water and Land Resources Division DRAINAGE INVESTIGATION REPORT FIELD INVESTIGATION FILE NO.:2009-0071 ......... . ADDRESS: 10646 2151 Ave. SW .......... NAME: _ Stuart. Soules.... PRONE: - -- 206.624.0740 DATE OF INVESTIGATION 1/2112009 INVESTIGATED BY: Ted Chrisite I arrived at the site of 15013 SE Janes Road 7:30 am to investigate a flooding ce prnt reported by Mr. Stuart Soules of the same address. I spoke with him via telephone. He stated that his property was high enough to onl flood d thdriv_ewwaa + but his neighbor's yard 15005 was flooded u to Floor lev 1 the house. He stated that he and his neighbor share a culvert which does not allow o -r down slope drainage as it was installed in a reverse manner with the flow going up slope. He request my speaking with the occupant of 15059 SE Jones Rd_ as he said she knew the history of the immediate area going back 50 years. I subsequently met with the occupant of this address, who identified herself as Liu Swenson. Ms. Swenson reitte rated the statement of Mr. Soules, stating, when the new Elliot Bridge and Stewart Creek work was done, the constructors failed to put the levee back that the Army Corps had put in years ago along the north shore of the river. During this most recent stone event the river had rose up and flowed around a cotton tree (as identified) around her house and neighboring properties. Ms. Swenson stated that she is awaiting a FEMA buy out for her property and that neighboring properties have been bought and demolished. She stated that she is waiting for a better offer. According to WP records the area is in a Flood Way. The most recent Flooding events indicated the water running consistent with this Flood Way indication of IMAP. This information is in this file. (stated) form 15059 -Ohio 7� foto 1 6 r� Photo 2 Shared Culvert 4 110 Photo 5 Stewart Creek Elliot Bridge "hoto s 154th Place SE Photo 3 KING COUNTY WATER AND LAND RESOURCES DivisioN DRAINAGE INVESTIGATION REPORT INVESTIGATION REQUEST PkobLw.,',- TANK IN RIVER RECEIVED BY: wkp Date: 07/14109 OK'd by: TYPe C File No . .. .... . ...... Reipi ejve roth,6 NAME: BILLIE EMERSON PHONE: 206.661.3432 Other: 2009-0653 Address: 15016 149'm AVE SE City RENTON State Zip 98058 - ... . ...... i. pren, . ... .... Access Permission Granted ❑ Call First (Would Like To Be Called andlor Present) F-1 REMARKS: TANK IN RIVER IS EMMITTING SOME SORT OF FUMES. AND IS KILLING VEGETATION ABOVE. TANK APPEARS TO BE SOME SORT OF OLD WATER TANK. Plat name: Other agencies involved: Lot No: Block No: No field investigation required El !NTFIRPORAN . . ... MPLETEM :jRyy-.4PffiF.XA 1/4 NW S 23 T 23 R 5 Parcel# 2323059133 Kroll: 816W TBros: 656,14 om— MD 1 2 3 Basin LCR "Council Dist 9 Charge #: Citizen notified on: Lj phone Lj letter [ I in person Lj email OR., No further action Turned to: on by recommended because: Ej Lead agency has been notified: ❑ Problem has been corrected. L] No problem has been Prior investigation identified. , addresses pro blern. SEE FILE 4 ❑ Private problem - NDAP will not consider because: El water originates onsite and/or on neighboring parcel. ❑ Location is outside WLRD Service Area. ❑ Other (Specify): ,G' err FS•+_f5 ! + ..Yf- } ��w� - -'+ . 1}t IM VA Ed uj X00 No ZR `y v7 Q ` e� ..:_, ,meq �'—, •�•�-w3-C i,_ ��� a. , ,. 'r+� CL r� i ' -r �' x S e - �a E g a 'W. ,Y• �1+ ,tea 1ti N F— f • On 'M .+ C _ R �•0 O-2 .%:sxt S" •}`,; .,jam L.. f� a 1L+ R9":, h 4: yt;= l._ �� �i y� }.- - N - 1 KJ r t m m1 c? a , ! Ski' Irv'• ,' r„' &' �'�ti1 «� E a i LL.LL N O O � Q. .F rlkY w K h ►.Jr = gC TN : .�, '.. y.: ,� � ]y—�Y P ZL 1 � 'J }jn .� a J'i' � ??. � C N•ti -i • � 1r{A°,, ��� - 1 ; 'v ' - �6' `�' '" ;s� '-. �.t `l � '� �. n.d., �A+'�+ ate' � _ �'� m' � Aqk ob _ G k i E _ 32 1 � � pRp 'Kk g � 7 k w- %t 1• - �r^�x 4 � m m t_ N F-N.G 4 24 D 0.25 0.1121, all 1 ......... ........ . I-------� mile- 1 in. - is" ft SEE , , MAP MAP 656 u m [3 E PI a 7 1/m%St NE7H7113�Fg U-11 �xN S�xa NEN h 114 1 6dr E:6iJt a�71ri r. 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P �:'z'�_i 4 F 0th 52 °► r Sk r S 1 0th �. j � •�'� . CO Ct, IJ 71 5 72nd5 i s xy0 PI _ N N r ` S' 1n "+{ sSE 172 v"',> rya � 6 174s-L, 751 7t 51715 4 �inp S < � p'; 1172nd tS2nd 172nd a r5t r fCa 5E1 ¢ o 50 S CREE7E T' ,kn - SE T 4 C7i FI 4Jv iv f PARK'ANtQ',' .. rn ^ haw t 75str Ln til TRAIL•...,. • 1i w ¢ pl w � �+ 3 143rd Av S Edi a' t3 t2tao�1;.J I r 6O0S CREEK' SE 1 f .��. s ;5 v 5E Jb St 750thCi. F th St. '. SE ~` c pls 33 1 SE 1 .st Ln «� AND TRAIL y ,, tt16q �n (SE airwp°d 61 ��-..:-SE c �.1 2 11 SE ?A�AK € 117thL"' mp1 -34 SE F >- 7 1 ft n5 SEE w MAP 2, 2008-0700 Brent Cawley Keith Dougherty January 13, 2009 TO: File FROM: Keith Dougherty RE: 2008-0700 Brent Cawiey BACKGROUND' FACILITY: DR0535 -- Madsen Creek Overflow Channel Site Visit Photographs December 8, 2008 The facility is located in Renton north of SE Renton Maple Valley Road between 1491' Ave SE and 154th Place SE. There was no letter of formal acceptance of the facility, but it appears it was required from a lawsuit judgment in 1974. The facility file states that Brent Cawley would like a hydraulic evaluation performed to determine if realigning the outlet culverts to be almost parallel to the flow of the Cedar River would increase the capacity of the bypass channel and prevent it from overtopping on to his property. His property is located just east of the overflow channel along the Cedar River (parcel 2323059123) Mr. Cawley has complained of trouble in the past with the facility. He stated that during the big storm of 2006, he had a significant amount of water flowing through his yard towards the Elliot Bridge Levy. He had also stated that he had dropped a leaf at the end of the pipes that convey water from the overflow channel to the Cedar River. According the Mr. Cawley, the leaf flowed backwards up the pipe rather than downstream in the river. He also dropped a leaf at the inlet of the pipe and said it did not move. Mr. Cawley has some engineering background and suggested to Rick Lowthian that the behavior of the leaf may possibly be due to a Venturi effect created by the river and the angle of the pipes inletting to the Cedar River. He would like an analysis done to determine if changing the angle of the pipes outlet to the river would reduce the head within the channel. His belief is that there is a drop in pressure at the outlet of the pipes and that because of this drop, water is being pushed up the pipe, or it is not allowing water to flow freely out of the pipes into the Cedar River. He thinks that changing the direction of the pipes (angling them more downstream, parallel to the river versus nearly perpendicular) may allow the water to flow freely from the pipes to the river and may even provide a suction action that would draw water out of the pipes. He believes the change would increase the capacity of the overflow channel and potentially prevent water from overflowing on to his property from the overflow channel. INVESTIGATION: 2008-0700 Brent Cawley Site Visit Photographs Keith Dougherty December 5, 2008 Initially I was asked to review the Venturi effect to determine how it applies to the overflow channel entering the Cedar River. The Venturi effect is used to determine. the change in pressure as an incompressible liquid flows through a constriction (usually in a pipe). Most often the Venturi effect appears to be applied to pressurized pipes with bend angles constricting the flow within system. The similarity could be made to the inlet pipes of the overflow channel acting as a constriction to the flow of the Cedar River. While the pipes of the inlet channel may act as a constriction to the flow of the river, it would seem reasonable that the effects of the pipes would be minor considering the size of the river versus the size of the pipes and how far the pipes extend into the river. Currently, I do not have access to any models to simulate the Venturi effect. As such, my investigation utilizes the stormwater models and information available to me. A quick document search on the properties near the channel showed no easements or tracts that define the drainage channel. It was observed on the Quarter Section map however that nearly the entire channel lies within the 100 -yr flood plain. Mr. Cawley's property is also within the Cedar River flood -way. The areas adjacent to the Cedar River at this location are protected from flooding by the Elliot Bridge Levy. Investigation of the DR facility file found that this channel has a lengthy past. It was originally constructed in the mid seventies as a result of a lawsuit in 1974 regarding increased runoff from the Fairfield development. At that time it appears that easements were obtained from at least 2 property owners by King County to maintain the channel. There have been several complaints/lawsuits following the original ruling as it appears this channel has had many instances of flooding. More issues arose when WSDOT widened highway 169. At that time, they replaced the three 36 -inch culverts across Hwy 169 with a single 8 -foot by 6 -foot box culvert. Based on simple calculations, it would appear that the box culvert has more capacity than the three 36 -inch pipes. The additional capacity would indicate the potential for increased flows to a channel that already has a history of problems. I did not find any documents of a redesign of the channel at the time of the culvert replacement. Brian Sleight and I visited the site on December 5, 2008. Mr. Cawley met us at on site and showed us the pipes of concern. He stated that he had seen the pipes running within 6 -inches of full. He also explained that during the large 2006 storm that a significant amount of water was running through his yard. He stated that King County maintenance/roads came out and added some fill to the berm on the east side of the. channel to reduce some of the water flowing through his property. He also believes that the west side of the channel is higher than the east side and would like them to be equal 2008-0700 Brent Cawley Site Visit Photographs Keith Dougherty December 5, 2008 (if not higher on the east side to prevent flows onto his property). Brian Sleight and X surveyed numerous points on the site. For more infonnation about the survey, please see the attached exhibit and summary table. 0 The analysis of the data involves several tasks. The primary task is the hydraulic analysis 0n the pipes and the different pipe discharge angles. Additional tasks include: • Determining if the east bank is lower than the west bank. 0 • Comparing the elevations of Mr. Cawley's property to the elevations of the channel and riverbank. 0 • Determining the Cedar River influence versus the Madsen Creek influence on flooding conditions. The hydraulic analysis was performed using the King County Backwater Program (KCBW) which models storm flows through channels and pipes. Background data was taken from several sources including the Madsen Creek Flood Plain Study performed for the Renton Assembly of God development and the WSDUT expansion of Highway 169. Additional numbers had to be determined or assumed before the hydraulic modeling could be performed. These numbers included: the tailwater elevation (96.Oft) which was based on descriptions/observations made by Mr. Cawley. The slope of the channel (between 0.23-0.44°/x), the slope of the pipes (approximately 1.0%) based on survey data, the Cedar River flow volume (-4800cfs) from Cedar River report and velocity of the flows entering the pipes from upstream (7.89ft/sec) based on the cross-section if the channel, the flows into the channel from upstream (261 cfs) from the Madsen Creek Flood Plain Study. Additionally, a range of flows was used to understand where flooding may occur at different levels. For the analysis, a range of 50-450cfs was used as a range of the channel running full with no tailwater elevation (-50efs) and the two 6ft pipes flowing at near capacity (-450cfs). Lastly, several angles were used to simulate the changes in alignment as Mr. Cawley requested. Four bend angles of 0, 30, 60 and 90 degrees were compared to determine how a change in pipe alignment would affect the water level within the pipes/channel. Note also that all elevations are relative elevations from the survey data, not actual elevations based upon a NAVD datum. RESULTS: The modeling of the conveyance in KCBW shows that there is not a significant change in water levels by changing the discharge angle of the pipes. Assuming a conservative scenario where 261cfs is coming into the two 6ft pipes, there would be approximately 130+cfs per pipe. The difference in elevation from 0 degrees to 90 degrees is only about 0.2ft (---2.5inches). A more severe case where all 261cfs was modeled flowing through a 2008-0700 Brent Cawley Site Visit Photographs Keith Dougherty December 5, 2008 single 6ft pipe shows a change in head of less than 0.69ft (-8inches). As mentioned before, the range of flows up to 450cfs was modeled which is much higher than expected. That data shows that a single 6ft pipe with 450cfs of flow would be in overflow conditions, but it would still only change the water level approximately 1.5ft. These results indicated that there would not be a significant gain to the water level if the pipes were realigned. A comparison of the survey points from the west bank and east bank shows varying results. For roughly the southern 400ft of the channel, the west bank is lower than the east bank. For approximately the northern 400ft of the channel, the west bank is higher than the east bank. This is the area more closely located near the Cawley residence. Other than a low spot in the channel's bank near Mr. Cawley's driveway, both banks along the northern 400ft generally have less than I -foot difference in elevation. The elevations of the overflow channel's east bank and the elevation of points near the Cawley home, driveway and well -house then compared. The elevations of the cast bank are generally higher than the elevations of the Cawley property indicating that water will flow towards their property if it overflows the east bank. The low point of the east bank (97.62ft) is lower than the house foundation (98.25ft) and the well house base (97.77ft) but it was higher than the driveway spot shot (97.54). The approximate low point on the Elliot Bridge Levy at Mr. Cawley's property was also found to be at 97.49ft. This is slightly lower (-1.5inches) than the low point along the east bank. Aside from comparing the low points of the east bank and the levy, the other elevation shots taken along the levy are generally lower than the elevations along the east bank of the channel. This would indicate that water is more likely to come from the levy overflowing before the east bank of the overflow channel. This is consistent with conversations with Mr. Cawley in January of 2009. I called Mr. Cawley on January 21, 2009 to find out if he had any flooding issues due to the storms over the week of 115-1/9. Mr. Cawley indicated during the phone call that he had significant flooding (within 4 -inches of this floor) but most of it was coming from the river's berm at the north side of his property, not the overflow channel. He also indicated that if there was water coming from the Fairmont development, that the channel would not have been able to handle the flows. However, other than the low spot elevation, the levy elevation is lower than and very near the elevation (within one inch) of the house foundation. It should also be noted that the elevation of the Cawley foundation is between 1-2ft above the tailwater of the river when it is running at the high levels reported by Mr. Cawley. Lastly a comparison was performed to determine the influence of the Madsen Creek overflow versus the Cedar River impact on the water level in the channel. Again, data for 2008-0700 Brent Cawley Keith Dougherty Site Visit Photographs December 5, 2008 the culverts as well as the channel were analyzed in the KCBW program. The low elevation taken at the bottom of the channel (while dry) was at 92.34ft. During the storms in January, Mr. Cawley indicated that water was overflowing from the Elliot Bridge Levy at the north of his property, which has a low elevation of 97.49ft. That means the tailwater elevation in the channel at that time would also be at least 97.49ft indicating that the river's influence on the water level may vary as much as 5.15ft or more. Using the 97.49ft as a tailwater elevation is a conservative scenario to model the channel/culverts to determine the influence of the 26lefs coming from the Madsen overflow. That modeling shows that the water level in the overflow channel would only rise to 98.33ft which is a difference of 0.84ft. The results indicate that the Cedar River's tailwater elevation has a more significant impact on the water level than the flow entering the overflow channel and the capacity of the channel or the culverts. DISCUSSION' Several factors were considered when analyzing the flooding issues at Mr. Cawley's property. The main task was to perform a hydraulic analysis to determine if changing the pipes angles inletting to the Cedar River would improve their performance and decrease flooding from the overflow channel onto Mr. Cawley's property. Other factors considered were the overflow channel's east and west bank elevations relative to each other, the elevation of Mr. Cawley's property relative to the channel and the river elevations, and the effect of the river versus the inflow to the channel on flooding conditions. The results of the hydraulic analysis on changing the pipe angles indicates that only a slight improvement (0.2ft or 2.5inches) may result by altering the pipe alignments as they inlet to the Cedar River. The elevations of the east and west banks vary based on location. Over the southern half of the channel, the west bank is lower than the east bank. But the northern portion of the channel, closer to Mr. Cawley's home and driveway, does show that the eastern bank is lower thank the western bank. At the low point in the east bank, it is almost 2ft lower than the west bank. The relative elevation of Mr. Cawley's property to the overflow channel and the Elliot Bridge Levy does indicate that his property will receive water that overflows either the east bank of the channel or the levy. The elevation of the Cedar River when it is running. at a high level indicates that flooding in the areas around the river would not be unusual during times of high flows in the river. Additionally, the Cawley property lies within the 2008-0700 Brent Cawley Site Visit Photographs Keith Dougherty December 5, 2008 100 -yr flood plain and the Cedar River flood -way, which is an indication that flooding during large storm events is not uncommon and may be an ongoing issue. Lastly, the impact of the Cedar River's water level seems to be a more significant influence on water overtopping the east bank of the channel rather than the upstream flows from the Madsen Creek overflow. That would lead to the conclusion that the flooding is less likely a capacity issue and more likely a result of a high tailwater condition from the river. In short, it appears that the issues are more likely related to the water level in the Cedar River and the elevations of the overflow channel and Elliot Bridge Levy and less dependant on the angle of the pipes inletting to the river. Reviewing the data shows that at an elevation of 98.5ft, flows that exceed the expected maximum 261cfs from the Madsen Creek overflow can be conveyed without flooding through the channel. The approximate amount of material needed to bring the low areas of the east bank up to 98.5ft is about 22 cubic -yards of fill. This would likely cost less than $1,000 based on the NDAP Construction spreadsheet. This would seem to be a more suitable and cost effective solution versus changing the pipe alignment and performing work along the Cedar River. RECOMMENDATION: I recommend raising the low areas along the overflow channel's east bank to the relative elevation of 98.5ft according to our survey data. This would be a more effective solution because the results show that flooding is more likely a result of the Cedar River water level and the elevations of the banks rather than an issue caused by the angle of the inlet pipes. It is also a more cost effective solution and could be implemented more quickly and with less impact to the Cedar River. 2008-0700 Brent Cawley Keith Dougherty Site Visit Photographs December 5, 2008 Aerial view of the channel and Brent Cawley's property. The Cawley property is outlined above in red. The channel runs the full length from the highway to the Cedar River is outlined in blue. J. -NG COUNTY WATER AND LAND RESOUTRCFs DIVISION DRAINAGE INXESTIGATION REPORT INVESTIGATION REQUEST P4 FALLEN TREEY. ..:° r` RECEIVED BY: wkp Date: 09109/08 OK'd by: File No. 2008-0507 ..... . NAN E: BRENT CAWLEY PHONE #: 425,761.4170 Other #: 42.5.965.5885 Address: 15247 155TH LANE SE City RENTON State ? ? oaf D A A�� .. ET..i.. Access Permission Granted ❑ Call First (Would Like To Be Called and/or Present) REMARKS Zip 98058 As of Sept 6th 2008 a freshly fallen tree has blocked the river just 2 feet down stream of the Madsen creek bypass drainage culverts. This end of the tree is already catching/ stopping debris coming down the river, and will eventually dam up and cause further back up of the Madsen creek by-pass during the rainy season. The Madsen creek by-pass already does not have enough flow capacity to handle the volume of water required during the rainy season. The current inadequate design has already repeatedly flooded my property causing damage. Any further impedance will only increase flood damage on my property that runs adjacent to Madsen creek by-pass. Please have somebody remove the tree in question. Plat name: _ Other agencies involved: Lot No: Black No: No field investigation required ❑ 1/$ NW S 23 T 23 R 5 Parcel # 2323059123 Kroll: 816W Th.Bros: 656f4 MD 1 2 3 4 Basin LCR Council Dist 9 Charge #: Citizen notified on ❑ phone ❑ letter U in person L email ❑ Private problem - NDAP will not consider because: ❑ Water originates onsite and/or on neighboring parcel. Location is outside WLRD Service Area. ❑ Other (Specify): �j SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) KCRTS was used to model the peak runoff from the Site. Per Table 3.2.2.b of the Manual the soil type is modeled as "Till" for the Alderwood gravelly sandy loam SCS classification as shown in Figure 4. Soils. The entire Site is modeled as "Forest." Results of the KCRTS analysis are included in this section. Area Breakdown Till Forest 390,841 s.f. X2014 D. R. STRONG Consulting Engineers Inc. Technical Information Report 8.972 acres The Enclave at Bridle Ridge Preliminary Plat Page 13 City of Renton PRE -DEVELOPED HOURLY TIME STEP MODELING INPUT: Land Use Summary Area ?� Till Forest 8.97 acres Till Pasture :. 0.00 acres Till'Grass 0.0U acres Outvwash Forest 0,00 acres buiwash Pasture ". 0.00 acres Outwash Grass 0.00 acres Wetiand 0.00 acres Impervious Ip.OQ.acres Natal ...�� 8.97 acres Scale Factor 1.00 Hourly Reduced Time Series:pr-dew ? Compute Time. Series Modify User Input 'File for computed Time Series [.TSF] PRE -DEVELOPED HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates --- Flow Rate Rank Time of Peak (CFS) (CFS) Period 0.566 2 2/09/01 18:00 0.154 7 1/06/02 3:00 0.419 4 2/28/03 3:00 0.015 8 3/24/04 20:00 0.249 6 1/05/05 8:00 0.435 3 1/18/06 21:00 0.366 5 11/24/06 4:00 0.724 1 1/09/08 9:00 Computed Peaks 0.671 02014 D. R. STRONG Consulting Engineers Inc. Technical Information Report -----Flow Frequency Analysis------- - - Peaks - Rank Return Prob (CFS) Period 0.724 1 100.00 0.990 0.566 2 25.00 0.960 0.435 3 10.00 0.900 0.419 4 5.00 0.800 0.366 5 3.00 0.667 0.249 6 2.00 0.500 0.154 7 1.30 0.231 0.015 8 1.10 0.091 0.671 50.00 0.980 The Enclave at Bridle Ridge Preliminary Plat Page 14 City of Renton FIGURE 5 PREDEVELOPMENT AREA MAP ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 15 Technical Information Report City of Renton DEVELOPED SITE HYDROLOGY (PART B) DEVELOPED SITE AREA HYDROLOGY KGRTS was used to model the developed peak runoff from the Site. The soil types are unchanged from the pre -developed conditions. The portions of the Site within the proposed clearing limits tributary to the proposed detention vault were modeled as "Till Grass" and Impervious as appropriate. Results of the KCRTS analysis are included in this section. Area Breakdown Predeveloped Till Forest 390840.7 8.972 Developed ROW Lots collected Tract A collected Frontage 79419 Imp 63825 Per 15130 bypass imp 464 271536 IM p 124000 Per 147536 Imp Per Imp Per bypass imp bypassper 32174 16087 16087 7712 4652 2215 249 596 1.823 1.465 0.347 0.011 6.234 2.847 3.387 0.739 0.369 0.369 0.177 0.107 0.051 0.006. 0.014 ©2014 D, R. STRONG consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 16 Technical Information Report City of Renton Developed Hourly Time Step Modeling Input: Land Use Summary L.o I :'''' l - Area---=-=---- Till Forest 0.00 acres Till Pasture 0.00 acres Till Crass 4,15 acres 0utwa9h Forest 0.00.acres Outwash Pasture 0.00 acres �}utwash Crass 0.00 acres Wl tland 0.00. acres Impervious 4.79 acres Total 8.94 acres " t Scale. Factor 1:00 Hourly . .,Reduced Time Series: rdin Compute Time Series Modify User lnpuf'. File for computed Time Series [.TSF] DEVELOPED HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:rdin.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates --- Flow Rate Rank Time of Peak (CFS) (CFS) Period 1.53 6 2/09/01 2:00 1.21 8 1/05/02 16:00 1.85 2 2/27/03 7:00 1.27 7 8/26/04 2:00 1.54 5 10/28/01 16:00 1.62 4 1/18/06 16:00 1.85 3 10/26/06 0:00 3.14 1 1/09/08 6:00 Computed Peaks 2.71 ©2014 D. R. STRONG Consulting Engineers Inc. Technical Information Report -----Flow Frequency Analysis-------- - - Peaks - - Rank Return Prob (CFS) Period 3.14 1 100.00 0.990 1.85 2 25.00 0.960 1.85 3 10.00 0.900 1.62 4 5.00 0.800 1.54 5 3.00 0.667 1.53 6 2.00 0.500 1.27 7 1.30 0.231 1.21 8 1.10 0.091 2.71 50.00 0.980 The Enclave at Bridle Ridge Preliminary Plat Page 17 City of Renton BYPASS HOURLY TIME STEP MODELING INPUT: Land Use Summary Till Forest 0.09 acres -Fill Pasture 0.00 acres Till Grass 0.01 acres . Outwash Forest OMO acres Outwash Pasture 0:00 acres .. Outwash Grass 0.00.acres Wetland 0.0U acres Impervious 9,02 acres 0.43 acres Scale Factor: 1.00: Hourly Reduced:.. Time Series:bypass J>>J. Compute Time Series' Modify User Input Retrieve runoff files and compute Time Series BYPASS HOURLY TIME STEP MODELING OUTPUT: Flow Frequency Analysis Time Series File:bypass.tst Project Location:Sea-Tac ---Annual Peak Flow Rates --- Flow Rate Rank Time of Peak (CFS) 0.011 1 100.00 0.005 5 2/09/01 2:00 0.004 8 1/05/02 16:00 0.006 2 12/08/02 18:00 0.004 7 8/26/04 2:00 0.005 6 10/28/04 16:00 0.005 4 1/18/06 16:00 0.006 3 10/26/06 0:00 0.011 1 1/09/08 6:00 Computed Peaks 02014 17, R. STRONG Consulting Engineers Inc. Technical Information Report -Flow Frequency Analysis - - Peaks - - Rank Return Prob (CFS) Period 0.011 1 100.00 0.990 0.006 2 25.00 0.960 0.006 3 10.00 0.900 0.005 4 5.00 0.800 0.005 5 3.00 0.667 0.005 6 2.00 0.500 0.004 7 1.30 0.231 0.004 8 1.10 0.091 0.009 50.00 0.980 The Enclave at Bridle Ridge Preliminary Plat Page 18 City of Renton FIGURE 6 POST DEVELOPMENT AREA MAP .Q2014 D. R. STRONG Consulting Engineers Inc.. The Enclave at Bridle Ridge Preliminary Plat Page 19. Technical Information Report City of Renton PERFORMANCE STANDARDS (PART C) The Project is required to adhere to Level 2 Flow Control criteria. The Level 2 performance criteria requires that the developed condition's durations must match the predeveloped durations ranging from 50% of the two-year peak flow up to the full 50 - year peak flow and also match developed peak discharge rates to predeveloped peak discharge rates for the 2 -year and 10 -year return periods (KCSVVDM, Sec. 1.2). The Basic Water Quality Treatment goal is to remove 80% of TSS for flows or volumes up to and including the WQ design flow or volume. Conveyance criteria for the Project require that all new pipes be designed to convey and contain (at minimum) the 25 -year peak flow. The conveyance system design will be analyzed at time of final engineering. FLOW CONTROL SYSTEM (PART D) The Site will utilize a detention pond meeting the Level 2 Flow Control Criteria. The King County Runoff Time Series (KCRTS) software was used to size the detention facility. The detention pond design information is included in this section. FLOW CONTROL BMP SELECTION Subdivision projects are required to mitigate for impervious surface equal to a minimum of 10% of each lot area by use of Flow Control Best Management Practices (BMP's). The project must analyze the feasibility of infiltration and dispersion of roof runoff. The project may utilize splash blocks meeting the requirements for basic dispersion. The project may also utilize pervious pavement or other BMP's as found in Appendix C of the Manual. Evaluation and inclusion of a BMP will be accomplished at final engineering. Q2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 20 Technical Information Report City of Renton FLOW CONTROL FACILITY DESIGN OUTPUT Retention/Detention Facility Type of Facility: Detention Pond T Effe Side Slope: Top cove 3.00 H:1V Pond Bottom Length: 152.32 ft Pond Bottom Width: '16.16 ft Pond Bottom Area: 11600. sq. ft Area at 1 £t. FB: 22960. sq. ft (in) 0.527 acres Storage Depth: 6.00 ft Stage U Elevation: 371.00 £t Storage Volume: 96867. cu. ft 2 2,224 ac -ft Riser Head: 6.00 ft Riser Diameter: 18.00 in Number of orifices: 2, Full Head Pipe Orifice # Height Diameter Discharge Diameter. {£t) (in) (CFS) (in) 1 0.00 1.50 0.149 2 4.10 2.65 0.262 6.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft} (ft} (cu. ft} (ac -ft} (cfs) (cfs) (sq. ft) 0,00 371.00 0. 0.000 0.000 0.00 11600. 0.02 371.02 232, 0.005 0.008 0.00 11627. 0.Q3 371.43 349. 0.008 0,011 0.00 11641. 0.05 371.05 582. 0.013 0,013 0.00 11669. 0.06 371.06 699. 0.016 0,015 0.00 11682, 0.48 371,08 932. 0.021 0.017 0.00 11710. 0.09 371.09 1050. 0.024 0.019 0,00 11724. 0.11 371.11 1284. 0.029 0.020 0.00 11751. 0.13 371.13 1520. 0.035 Q.022 0.00 11779, 0.23 371,23 2709. 0.062 0.029 0.00 11917. 0.33 371.33 3903. 0.090 0.035 0.00 12056. 0.43 371.43 5116. 0.117 0.040 0.00 12196, 0.52 371.52 6219, 0.143 0.044 0.00 12323, 0.63 371.63 7583. 0.174 0.042 0.00 12478. 0,73 371.73 8838. 0.203 0.052 0.00 12620. 0.83 371.83 10107, 0.232 0.055 0.00 12'763. 0.93 371,93 11390. 0.261 0.059 0.00 12906, 1,03 372.03 12688. 0.291 0.062 0.00 13050. 1.13 372,13 14001. 0.321 0.065 0.00 13195, 1.23 372,23 15327. 0.352 0.068 0.00 13341. 1.33 372.33 1b669. 0.383 0.070 0.00 13487. 1.43 372.43 18025. 0.414 0.073 0.00 13634, 1.53 372.53 19395. 0.445 0.075 0.00 1.3782. 1.63 372,63 20781. 0.477 0.078 0.00 13930. 1,73 372.'73 22182. 0.509 0.080 0.00 14079. 1.83 372.83 23597. O.S42 0.082 0,00 14229. 1.93 372.93 25027, 0.575 0.085 0.00 14320, 2.03 373.03 26413. 0.608 0.087 0.00 14531. 2.13 373.13 27934. 0.691 0.089 0.00 14683, 2.23 373.23 29410. 0.675 0.091 0.00 14836. 2.33 373.33 30901, 0.709 0.093 0.00 14989. 2.43 373.43 32908. 0.744 0.095 0.00 15144. ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 21 Technical Information Report City of Renton 2.52 373.52 33777. 0.775 0.097 0.00 15283. 2.62 373.62 35313. 0.811 0.099 0.00 15439. 2.72 373.72 36864. 0.846 0.101 0.00 15595, 2.82 373.82 38432. 0.882 0.103 0.00 15752. 2.92 373.92 40015. 0.919 0.104 0.00 15910. 3.02 3`14.02 41614. 0,955 0.106 0.00 16068. 3.12 374.12 43229. 0.992 0.108 0.00 16227. 3.22 374.22 44859. 1.030 0.110 0.00 1.6387. 3.32 374.32 46506. 1.068 0.111 0.00 16548. 3.42 374.42 48169. 1.106 0.113 0.00 16709. 3.52 374.52 49048. 1.144 0.115 0.00 16871. 3.62 374.62 51543. 1.183 0.116 0.00 17034. 3.72 374.72 53255. 1.223 0.118 0.00 17198. 3.82 374.82 54983. 1.262 0.119 0.00 17362. 3.92 374.92 56727. 1.302 0.121 0.00 17527. 4.02 375.02 58488. 1.343 0.122 0.00 17693. 4.10 375.10 59909. 1.375 0.124 0.00 17826. 4.13 375.13 60444. 1.368 0.126 0.00 17876. 4.16 375.16 60981. 1.400 0.131 0.00 17926. 4.18 375.18 61340. 1,408 0.141 0.00 17959, 4,21 375,21 61880. 1.421 0.154 0.00 18009. 4.24 375.24 62421. 1.433 0.169 0.00 18060. 4.27 375.27 62963. 1.445 0,188 0.00 18110. 4.29 375.29 63326. 1.454 0.210 0,00 18143. 4.32 375.32 63871. 1.466 0.216 0.00 18194. 4.35 375.35 64418. 1.479 0.222 0.00 18244. 4.45 375.45 66250, 1.521 0.241 ().CO 18413. 4.55 375.55 68100, 1.563 0.258 0.00 18583. 4.65 375.65 69967. 1.606 0.273 0.00 18753. 4.75 375.75 71851, 1.649 0.286 0.00 18924. 4.85 375.85 73752. 1.693 0.299 0.00 19095, 4.95 375.95 75670, 1.737 0.311 0.00 19268. 5.05 376.05 77605. 1.782 0.323 0.00 19441. 5.15 376.15 79558. 1.826 0.334 0.00 19615. 5.25 376.25 81528. 1.872 0.344 0.00 19789. 5.35 376.35 63516. 1.917 0.354 0.00 19964. 5.45 376.45 85521, 1.963 0.364 0.00 20140. 5.55 376.55 87544. 2.010 0.373 0.00 20317. 5.65 376.65 89585. 2.057 0.382 0.00 20494, 5.75 376.75 91643. 2.104 0.391 0.00 20673, 5.85 376.85 93719. 2.151 0.399 0.00 20851. 5.95 376.95 95813. 2.200 0.408 0.00 21031. 6.00 377.00 96867. 2.224 0.412 0.00 21121. 6.10 377.10 98988. 2.272 0.882 0.00 21302. 6.20 377,20 101127. 2.322 1.730 0.00 21483. 6.30 377.30 103285. 2.371 2.840 0.00 21665. 6.40 377.40 105460. 2.421 4.140 0.00 21848. 6.50 377.50 107654. 2.471 5.620 0.00 22031. 6.60 377.60 109867, 2.522 7.050 0.00 22216. 6.70 377.70 112098. 2.573 7.580 0.00 22401. 6.80 377.80 114347. 2.625 8.080 0.00 22586, 6.90 377.90 116615. 2.677 8.550 0.00 22773. 7.00 378.00 118902. 2.730 9.000 0.00 22960, 7.10 378.10 121207. 2,783 9.420 0.00 23148. 7.20 378.20 123531, 2.836 9.820 0.00 23336. 7.30 378.30 125874, 2.890 10.210 0.00 23526. 7.40 378.40 128236. 2.944 10.580 0.00 23716. 7.50 378.50 130617. 2.999 10.940 0.00 23906. 7.60 378.60 133018. 3.054 11.290 0.00 24098. 7.70 378.70 135437. 3.109 11.630 0.00 24290. 7.80 378.80 137876. 3.165 11.950 0.00 24483. 7.90 378.90 140333. 3.222 12.270 0.00 24676, 8.00 379.00 142811. 3.278 12.580 0.00 24871. p2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 22 Technical' Information Report City of Renton Hyd Inflow Outflow Peak Storage Stage Elev (Cu -Ft) {AC -Ft) 1 3.14 1.86 6.21 3,7.21. 7.01372. 2.32`1 2 1.53 0.57 6.03 3'77.03 9'1593, 2.240 3 1.85 0.35 5.35 376.35 83464. 1.916 4 1.85 0.35 5.30 376.30 82547, 1.895 5 1.62 0.26 4.58 375.58 68641. 1.576 6 1.01 0.15 4.21 375.21 61829, 1.419 7 1.21 0.12 3.64 374.64 51903. 1.192 8 1.27 0.10 2.51 373.51 33552. 0.770 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 1.86 0.01 ******** ******* 1.86 2 0.57 0.01 ******** 0.57 0.57 3 0.35 0.01 ******** ******* 0.36 4 0.35 0.01 ******** ******* 0.35 5 0.26 0.01 ******** ******* 0.26 6 0.15 0.00 ******** ******* 0.15 7 0.12 0.00 ****** ******* 0.12 8 0.10 0.00 ******** ******* 0.10 ---------------------------------- Route Time Series through Facility Inflow Time Series File:rdin.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 3.14 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 1.86 CFS at 10:00 on Jan 9 in Year 8 Peak Reservoir Stage: 6.21 Ft Peak Reservoir Elev: 377.21 Ft Peak Reservoir Storage: 101372. Cu -Ft 2.327 Ac -Ft Add Time Series:bypass.tsf Peak Summed Discharge: 1.86 CFS at 10:00 cn Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout,tsf Project Location:Sea-Tac ---Annual Peak Flow Rates --- Flow Rate Rank Time of Peak (CFS) 0.573 2 2/09/01 20:00 0.116 7 1/07/02 4:00 0.354 3 3/06/03 22:00 0.097 8 8/26/04 7:00 0.153 6 1/08/05 3:00 0.262 5 1/19/06 1:00 0.349 4 11/24/06 9:00 1.86 1 1/09/08 10:00 Computed Peaks Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates --- Flow Rate Rank Time of Peak (CFS) 02014 D. R. STRONG Consulting Engineers Inc. Technical Information Report -----Flow Frequency Analysis------- - - Peaks - - Rarik Return ?rob (CFS) (ft) Period 1.86 6.21 1 100.00 0.990 0.573 6.03 2 25.00 0.960 0.354 5.35 3 10.00 0.900 0.349 5.30 4 5.00 0.800 0.262 4.58 5 3.00 0.667 0.153 4.21 6 2.00 0.500 0.116 3.64 7 1.30 0.231 0.097 2.50 8 1.10 0.091 1.43 6.16 50.00 0.980 -----Flow Frequency Analysis ------- Peaks - - Rank Return Prob (CFS) Period The Enclave at Bridle Ridge Preliminary Plat Page 23 City of Renton 0.574 2 2/C9/01 20:00 1.86 1 100.00 0.990 0.117 7 1/07/02 5:00 0.574 2 25.00 0.960 0.355 3 3/06/03 22:00 0.355 3 10.00 0.900 0.097 8 8/26/04 7:00 0.350 4 5.00 0.800 0.1.53 6 1/08/05 3:00 0.263 5 3.00 0.667 0.263 5 1/19/06 0:00 0.153 6 2.00 0.500 0.350 4 11/24/06 9:00 0.117 7 1.30 0.231 1.86 1 1/09/08 10:00 0.097 8 1.10 0.091 Computed Peaks 1.43 50.00 0.980 Flow Duration from Time Series File:rdout.tst Cutoff Count Frequency CDF Exceedence_Probability CFS % s 0.008 33068 53.927 53.927 46.073 0.461E+00 0.024 6522 10.636 64.563 35.437 0.354E+00 0.040 5683 9.268 73.831 26.169 0.262E+00 0.056 5192 8.461 82.298 17.702 0.177E+00 0.073 4403 7.180 89.478 10.522 0.105E+00 0.089 2526 4.119 93.598 6.402 0.640E-01 0.105 1875 3.058 96.655 3.345 0.334E-01 0.121 1405 2.291 98.947 1.053 0.105E-01 0.137 262 0.427 99.374 0.626 0.626E-02 0.153 38 0.062 99.436 0.564 0.5641✓ -02 0.169 23 0.038 99.473 0.527 0.527F,-02 0.185 17 0.028 99.501. 0.499 0.499E-02 0.201 10 0.016 99.517 0.483 0.483E-02 0.218 29 0.047 99.565 0.435 0.435E -C2 0.234 40 0.065 99.630 0.370 0.370E-02 0.250 37 0.060 99.690 0.310 0.310E -C2 0.266 35 0.057 99.747 0.253 0.253E-02 0.282 25 0.041 99.788 0.212 0.212E-02 0.298 21 0.034 99.822 0.178 0.178E-02 0.314 17 0.028 99.850 0.150 0.150E-02 0.330 15 0.024 99.874 0.126 0.126E-02 0.346 23 0.038 99.912 0.088 0.881E-03 0.362 17 0.028 99.940 x.060 0.603E-03 0.379 8 0.013 99.953 0.047 0.473E--03 0.395 16 0.026 99.919 0.021 0.212E-03 0.411 8 0.013 99.992 0.008 0.815E-04 0.427 2 0.003 99.995 0.005 0.489E-04 0.443 0 0.000 99.995 0.005 0.489E-04 0.459 1 0.002 99.997 0.003 0.326E-04 0.475 0 0.000 99.997 0.003 0.326E-04 0.491 0 0.000 99.997 0.003 0.326E-04 0.507 0 0.000 99.997 0.003 0.326E-04 0.523 0 0.000 99.997 0.003 0.326E -U4 0.540 1 0.002 99.998 0.002 0.163E-04 0.556 0 0.000 99.998 0.002 0.163E--04 0.572 0 0.000 99.998 0.002 0.163E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS 1� q $ 0.008 33117 54.007 54.007 45.993 0.460E+00 0.024 6433 10.491 64.498 35.502 0.355E+00 0.040 5813 9.480 73.977 26.023 0.260E+00 0.057 5090 8.301 82.278 17.722 0.177Eao0 0.073 4390 7.159 89.437 10.563 0.106E+00 0.089 2562 4.178 93.615 6.385 0.638E-01 0.105 1870 3.050 96.665 3.335 0.333E-01 0.121 1422 2.319 98.984 1.016 0.102E--01 0.137 24C 0.391 99.375 0.625 0.6251;-02 0.154 37 0.060 99.436 0.564 0.564E-02 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 24 Technical Information Report City of Renton 0.170 24 0.039 0.186 16 0.026 0.2.02 10 0.016 0.218 30 0.049 0.234 36 0.059 0.250 39 0.064 0.267 36 0.059 0.283 24 0.039 0.299 21 0.034 0.315 18 0.02,9 0.331 15 0.024 0.347 22 0.036 0.363 17 0.028 0.380 9 0.015 0.396 15 0.024 0.412 9 0.015 0.428 2 0.003 0.444 0 0.000 0.460 1 0.002 0.477 0 0.000 0.493 0 0.000 0.509 0 0.000 0.525 0 0.000 0.541 1 0.002 0.557 0 0.000 0.573 0 0.000 Duration Comparison Anaylsis Base File: predev.tsf New File: dsaut.tsf 99.475 0.525 0.525E-02 99.501 0.499 0.499E-02 99.517 0.483 0.483E-02 99.566 0.434 0.434E-02 99.625 0.375 0.375E-02 99.689 0.311 0,311E-02 99.741 0.253 0.253E--02 99.786 0.214 0.214E-02 99.821 0.179 0.179E-02 99.850 0.150 0.150E-02 99.874 0.126 0.126E-02 99.910 0.090 0.897E-03 99.938 0.062 0.620E-03 99.953 0.047 0.473E-03 99.9'77 0.023 0.228E-03 99.992. 0.008 0.815E-04 99.995 0.005 0.489E-04 99.995 0.005 0.489E-04 99.997 0.003 0.326E-04 99.997 0.003 0.326E-04 99.997 0.003 0.326E-04 99.997 0.003 0.326E--04 99.997 0.003 0.326E-04 99.998 0.002 0.163E-04 99.998 0.002 0.163E-04 99.998 0.002 0.163E-04 Cutoff Units: Discharge in CFS Cutoff 0.124 0.158 0.192 0.226 0.260 0.294 0.328 0.362 0.396 0.430 0.464 0.498 0.532 0.566 -----Fraction of Time ----- Base New 6Change 0.95E-02 0.74E-02 -21.8 0.63E-02 0.55E-02 -11.9 0.49E-02 0.49E--02 -1.3 0.37E-02 0.40E-02 8.4 0.28E-02 0.28E-02 -0.6 0.22E-02 0.18E-02 -16.9 0.15E-02 0.13E-02 -12.2 0.10E-02 0.62E-03 -38.7 0.62E-03 0.23E-03 -63.2 0.34E-03 0.49E-04 --85.7 0.21E-03 0.33E-04 -84.6 0.16E-03 0.33E-04 -80.0 0.98E-04 0.16E-04 -83.3 0.16E-04 0.16E-04 0.0 ---------Check of Probability Base 0.95E-02 0.124 0.63E-02 0.158 0.49E-02 0.192 0.37E--02 0.226 0.28E-02 0.260 0.22E-02 0.294 0.15E-02 0.328 0.10E-02 0.362 0.62E-03 0.396 0.34E-03 0.430 0.21E-03 0.464 0.16E-03 0.498 0.98E-04 0.532 0.16E-04 0.566 Maximum positive excursion = 0.015 cfs ( 7.6%) occurring at 0.195 cfs on the Base Data:predev.tsf and at 0.210 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.133 cfs (-24.3) occurring at 0.547 cfs on the Base Data:predev.tsf and at 0.414 cf.s on the New Data:dsout.tsf Tolerance ------- New %Change 0.122 -2.0 0.136 -14.1 0.188 -2.2 0.234 3.6 0.260 -0.1 0.279 -5.1 0.318 -3.0 0.343 -5.3 0.364 -8.0 0.390 -9.4 0.398 -14.3 0.404 -18.8 0.411 --22.8 0.5'74 1.5 ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 25 Technical Information Report City of Renton PEAK PLOT DURATION ANALYSIS Return Period 2 5 10 20 50 100 10e , o rdouLps in Su-lzr + dsaul.pks FRED'V_yls rdout Cur o a 10° a sn LL V rn E � R v ♦ a U Q � aq 0 ] 0'2 _ o i 2 5 10 20 30 40 50 60 TO 80 90 95 98 99 Gumulaliw Pmbability DURATION ANALYSIS 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 26 Technical Information Report City of Renton rdout Cur o dsoul.dur a TARGET.dL+ o o b N R v Er �`♦.�� e. v � a l ty 00 =. r o � V]-� 10-y 10� X302 i0+ ' '10c Probabtr EeceadencB 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 26 Technical Information Report City of Renton WATER QUALITY TREATMENT SYSTEM (PART E) The Project is located in the Basic Water Quality Treatment area. The treatment goal is 80% removal of total suspend solids for a typical rainfall year, assuming typical pollutant concentrations in urban runoff. A combined detention/water quality pond will accommodate this requirement. Rainfall (R) of the mean annual storm = 0.47 in. Area of impervious surface (Ai) = 208,554 s.f. Area of till soil covered with till grass (Atg) = 180,968 s.f. Area of till soil covered with till forest (Atf) = 0 s.f. Area of outwash soil covered with grass or forest (Ao) = 0 s.f. Volume factor (f) = 3 IIA Calculations Units Volume of runoff from mean annual storm (Vr) = 9123.507 c.f. Minimum Wetpool volume required (Vb) = 27,371 c.f. The provided water quality volume is 35,071 c.f. From KCSWDM Fig. 6.4.1.A From KCSWDM Sec. 6.4.1.1 Notes =(0.9Ai + 0.25Atg + 0.10Atf + 0.01Ao) * R/12 =f * Vr ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 27 Technical Information Report City of Renton FIGURE 7 DETENTION & WATER QUALITY FACILITY DETAILS This will be provided at time of final engineering. ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 28 Technical Information Report City of Renton SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per C.R. #4 of the KCSWDM, the conveyance system must be analyzed and designed for existing tributary and developed onsite runoff from the proposed project. Pipe systems shall be designed to convey the 100 -year design storm. The Rational Method will be used to calculate the Q -Ratio for each pipe node. Analysis will be performed at final engineering. 02014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 29 Technical Information Report City of Renton BACKWATER ANALYSIS A backwater analysis will be provided at time of final engineering. ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 30 Technical Information Report City of Renton SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies have been provided with this submittal. 1. Traffic Impact Analysis — TraffEx, Inc., December 27, 2013 2. Critical Areas Study — Sewall Wetland Consulting, Inc., February 3, 2014 3. Geotechnical Engineering Study — Earth Solutions NW LLC, February b, 2014 4. Arborist Report — Green Forest, Inc., February 18, 2014 ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 31 Technical Information Report City of Renton SECTION Vil OTHER PERMITS, VARIANCES AND ADJUSTMENTS Boundary Line Adjustment — City of Renton ©2094 D, R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 32 Technical Information Report City of Renton SECTION VIII ESC PLAN ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design meets the nine minimum requirements: 1. Clearing Limits — Areas to remain undisturbed shall be delineated with a high - visibility plastic fence prior to any Site clearing or grading. 2. Cover Measures — Disturbed Site areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection — Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. Traffic Area Stabilization -- A stabilized construction entrance will be located at the point of ingress/egress. 5. Sediment Retention — Surface water collected from disturbed areas of the Site shall be routed through a sediment vault or sediment traps prior to release from the Site. The sediment vault or traps will be installed prior to grading of any contributing area. 6. Surface Water Control —Interceptor berms or swales shall be installed to control and intercept all surface water from disturbed areas. Surface water controls shall be installed concurrently with and/or immediately following rough grading. 7. Dewatering Control — Will be provided as needed. 8. Dust Control -- Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. 9. Flow Control — Runoff collected in the sediment vault will discharge to the permanent detention pond outfall system. ©2094 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 33 Technical Information Report City of Renton SWPPS PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP's listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash-up waters from water-based paints in sanitary sewer; disposing of wastes from oil-based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 3. Building demolition: Protect stormwater drainage system from sediment -laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the Site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP will be submitted at the time of final engineering. Q2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 34 Technical Information Report City of Renton SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet —will be submitted at final engineering 2. The Stormwater Facility Summary Sheet is included in this section 3. Declaration of Covenant— will be provided prior to final engineering approval. ©2514 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 35 Technical Information Report City of Renton STORMWATER FACILITY SUMMARY SHEET Development The Enclave at Bridle Ridge Date February 13, 2014 Location 14038 156th Avenue SE. Renton. Washington ENGINEER DEVELOPER Name Maher A. Joudi, P.E. Name Firm D. R. STRONG Consulting Engineers, Inc. Firm PNW Holdings LLC Address 620 7 Avenue Address 9675 SE 36 Street, #105 Kirkland, WA 98033 Mercer Island, WA 98040 Phone (425) 827-3063 Phone (206) 588-1147 Developed Site: 6.981 acres Number of lots 31 Number of detention facilities on Site: Number of infiltration facilities on Site: vaults vaults 1 pond vaults tanks tanks Flow control provided in regional facility (give location) No flow control required Exemption number uownsiream urama a basins Immediate Major Basin Basin Lower Cedar River Cedar River Number & type of water quality facilities on Site: biofiltration swale (regular/wet/ or continuous inflow?) sand filter (basic or large?) large?) combined detention/WQ vault X combined detention/wetpond compost filter filter strip flow dispersion farm management plan landscape management plan oil/water separator (baffle or coalescing plate?) sand filter, linear (basic or CONTECH Stormfilter sand filter vault (basic or large?) stormwater wetland wetvault (basic or large?) Wetvault pre -settling pond flow -splitter catchbasin 02414 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 36 Technical Information Report City of Renton catch basin inserts: Manufacturer pre -settling structure: Manufacturer DESIGN INFORMATION INDIVIDUAL BASIN Water Quality design flow Water Quality treated volume Drainage basin(s) Onsite area (includes frontage) 8.942 Offsite area Type of Storage Facility Pond Live Storage Volume (rec uired 96,867 Predev Runoff Rate 2 -year 0.249 10 -year 0.435 100- ear 0.724 Developed Runoff Rate -2-year 0.153 includes bypass)____10-year 0.354 100 -year 1.860 Type of Restrictor Frop-Tee Size of orifice/restriction No. 1 1.50 No. 2 2.65 ©2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 37 Technical Information Report City of Renton SECTION K OPERATIONS AND MAINTENANCE MANUAL Excerpts from the 2009 KCSWDM will be provided at final engineering. O2014 D. R. STRONG Consulting Engineers Inc. The Enclave at Bridle Ridge Preliminary Plat Page 38 Technical Information Report City of Renton D.R. STRC CONSULTIN 10604 NE 38th Place Suite 101 Kirkland, WA 98033-7903 Ph: 425.827.3063 Fx: 425.827.2423 TF: 800.962.1402 www.drstrong.com s PREPARED FOR AMERICAN CLASSIC HOMES February 5, 2014 IL 0 iV - -kpf� Q" Ste en H. Air S Geologist ALS Kyle R. Campbell, P.E. Principal GEOTECHNICAL ENGINEERING STUDY THE ENCLAVE AT BRIDLE RIDGE RESIDENTIAL DEVELOPMENT 14038�ENTON, WASHINGTON 156th AVENUE EAST ������� ES -3220 FEB 2 7 2014 CITY MJF RMTON Earth Solutions NW, LLC 1805 - 136th Place Northeast, Suite 201 Bellevue, Washington 98005 Phone: 425-449-4704 Fax: 425-449-4711 Toll Free: 866-336-8710 r- Geotechnical Engineering Report --, Geotechnical Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi- neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnicai engineering study is unique, each geotechnical engineering report is unique, prepared solelytor the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one — not even you —should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary Do not read selected elements only. A Geotechnical Engineering Report Is Based on A Unique Set of Project -Specific Factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that was: • not prepared for you, • not prepared for your project, • not prepared for the specific site explored, or • completed before important project changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: • the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, • elevation, configuration, location, orientation, or weight of the proposed structure, • composition of the design team, or • project ownership. As a general rule, always inform your geotechnical engineer of project changes --even minor ones—and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineer- ing reportwhose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctua- tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ—sometimes significantly— from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. A Report's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those recommendations are notfinal, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. The geotechnical engineer who developed your report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation. A Geotechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Engineer's Logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, butpreface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac- tors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognize that geotechnical engineering is far less exact than other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvlronmental Concerns Are Not Covered The equipment, techniques, and personnel used to perform a geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenviron mental findings, conclusions, or recommendations-, e.g., about the likelihood of encountering underground storage tanks or regulated contaminants, Unanticipated environmental problems have led to numerous project failures. If you have not yet obtained your own geoen- vironmental information, ask your geotechnical consultant for risk man- agement guidance. Do not rely on an environmental report prepared for someone else. Obtain Professional Assistance To Deal with Mold Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the express purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in -this report, the geotechnical engineer in charge of this project is not a mold prevention consultant-, none of the services per- formed in connection with the geotechnical engineer's study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself he sufficient to prevent mold from growing in or on the structure involved. Rely, on Your, ASFE-Member Geoteclmcial Engineer for Additional Assistance Membership in ASFEfThe Best People on Earth exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more information. ASFE The 9031 F119116 t■ Egli 8811 Colesville Road/Suite G106, Silver Spring, MD 20910 Telephone: 301/565-2733 Facsimile: 301/589-2017 e-mail: info@asfe.org www.aste.org Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, in whole or in part by arry means whatsoever, is strictly prohibited, except with ASFE's specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of ASFE, and only for purposes of scholarly research or book review Only members of ASFE may use this document as a complement to or as an eiement of a geotechnical engineering report. Any other firm, individual, or other entity that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. I IGER06W.OM February 5, 2014 ES -3220 American Classic Homes 9675 - 36th Street, Suite 105 Mercer Island, Washington 98040 Attention: Mr. Justin Lagers Dear Mr. Lagers: Earth Solutions NWE« Earth Solutions NW LLC ' Geotechni( d En-1rieeihig • (._onstr�,( i i( )n Mi )nit(-)ri n + En�irunnunLil 5cicn<<'s Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, The Enclave at Bridle Ridge, Residential Development, 14038 - 156th Avenue Southeast, Renton, Washington". In general, the site is underlain by a weathered soil zone grading to very dense sandy glacial till deposits. In our opinion, the proposed residential buildings can be supported on conventional continuous and spread footing foundations bearing on competent native soils, re -compacted native soils, or structural fill. Competent soils suitable for support of foundations should be encountered at depths of between two to four feet below existing grades at most locations. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material will be necessary. Groundwater seepage was observed at three of the test pit locations. The groundwater seepage can be characterized as a perched condition and was observed at an average of approximately three feet in depth. Seepage should be expected during grading activities, particularly during winter, spring and early summer months. Recommendations for foundation design, site preparation, drainage, and other pertinent recommendations are provided in this study. We appreciate the opportunity to be of service to you on this project. If you have questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC Step n H. Avril Staff eologist 1805 - 1 hth H,we N.E.. Sui<<' 201 • 6010Vue, AVA 98005 • (4251 449-470.4 0 FAX f425j 449-4711 Table of Contents ES -3220 PAGE INTRODUCTION ........ General Prosect Description ....................................................... SITE CONDITIONS ................................ 2 Surface .............. 2 Subsurface 2 Fill. 2 Topsoil............................................................... 2 Native Soil 3 Geologic Setting .................................................. 3 Groundwater 3 DISCUSSION AND RECOMMENDATIONS .................................. 4 General 4 Site Preparation and General Earthwork ........................... 4 Wet Season Grading ............................................. 5 In-situ Soils 5 ImportedSoils ..... ........................ .................. ............. 6 Structural Fill 6 Foundations 6 Seismic Design Considerations ...................................... 7 Slab -On -Grade Floors 7 RetainingWalls ............................................................ 7 Drainage................................................................................... 8 Excavations and Slopes, ..................................... _ .................. 8 Utility Trench Backfill ................. I ................................... 9 Pavement Sections 9 LIMITATIONS.............................................. ......................... 10 Additional Services .......... ....... .................................... 10 Earth Solutions NW, LLC Table of Contents Cont'd ES -3220 GRAPHICS Plate 1 Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Retaining Wall Drainage Detail Plate 4 Footing Drain Detail APPENDICES Appendix A Subsurface Exploration Test Pit Logs Appendix B Laboratory Testing Results Earth Solutions NW LLC GEOTECHNICAL ENGINEERING STUDY THE ENCLAVE AT BRIDLE RIDGE RESIDENTIAL DEVELOPMENT 14038 - 156th AVENUE SOUTHEAST RENTON, WASHINGTON ES -3220 INTRODUCTION General This geotechnical engineering study was prepared for the proposed residential development to be constructed south of the intersection between 156th Avenue Southeast and Southeast 5th Place in Renton, Washington. The site is located on the east side of 156th Avenue Southeast; and is comprised of a large residential parcel currently developed with single-family residential structure and outbuildings. A large portion of the site is occupied by now un -used pastures, and livestock paddocks. The purpose of this study was to explore subsurface conditions across the site and develop geotechnical recommendations for the proposed development. Our scope of services for completing this geotechnical engineering study included the following: • Excavation, logging and sampling of six test pits on the site; • Laboratory testing of soil samples obtained from the test pits; • Engineering analyses, and; • Preparation of this report. The following documents/maps were reviewed as part of our report preparation: Proposed Site Plan for 156th Avenue Assemblage, Sheet SP1, dated January 7, 2014, provided by D.R. Strong Consulting Engineers; • Geologic Map of Washington, Northwest Quadrant, Dragovich, Logan, et al, 2002, and, • Washington State USDA Soil Conservation Survey (SCS). Project Description We understand the site will be developed with 31 residential lots, access roads, a drainage tract located within the southern portion of the site, and associated improvements. The remainder of the site will be developed with general landscaping and paved driveways. Given the topographic change across the site, grading activities will likely involve cuts and fills on the order of ten feet or less to establish the final design grades. American Classic Homes ES -3220 February 5, 2014 Page 2 Building construction is anticipated to consist of relatively lightly loaded wood framing and slab - ort -grade floors. Perimeter foundation loading is expected to range from approximately one to two kips per foot. Slab -on -grade loading is expected to be on the order of 150 psf. If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to confirm that the geotechnical recommendations included in this report have been incorporated into the project plans. SITE CONDITIONS Surface The site is located on the east side of 156th Avenue Southeast south of the intersection with Southeast 5th Place in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map) included in this study. The site is irregular in shape and consists of a single residential parcel. The site is currently developed with single-family residence and out buildings. The majority, however, of each parcel is occupied by green space. The existing site topography descends from the north towards the south; with elevation change on the order of 20 feet. Vegetation on the subject site consisted primarily of field grass, cedar and fir trees, and blackberries during our fieldwork (January 2014). Subsurface ESNW representatives observed, logged and sampled six test pits excavated with a trackhoe and operator provided by the client across the accessible portions of the site. The approximate locations of the test pits are depicted on the Test Pit Location Plan (Plate 2). Please refer to the test pit logs provided in Appendix A for a more detailed description of the subsurface conditions. Fill Fill was not encountered at any of the test pit locations. There is the potential for limited amounts of fill surrounding the existing residential structure; and along road alignments and existing utility trenches. If fill is encountered it may be suitable for support of foundations; however a representative of ESNW should be retained during the construction phases of the site development to evaluate the suitability of any on-site soils for use as structural fill or bearing of foundations. Topsoil Topsoil was encountered at all test pit locations ranging in thickness of six to ten inches below existing grade. Topsoil is not suitable for use as structural fill nor should it be mixed with material to be used as structural fill. Topsoil or otherwise unsuitable material can be used in landscaping areas if desired. Earth Solutions NW, LLC American Classic Homes February 5, 2014 Native Soil ES -3220 Page 3 Underlying the topsoil, native soils consisting primarily of loose to medium dense weathered glacial deposits transitioning to very dense unweathered glacial till were encountered extending to the maximum exploration depth of eight feet below existing grades. The glacial till soil consisted of silty sand with gravel (Unified Soil Classification, SM); and soil relative density generally increased in depth, from loose in the weathered zone to very dense within the unweathered glacial till. The weathered glacial till was generally observed extending to an average depth of three feet; where it transitioned to an unweathered dense condition. Geologic Setting The referenced geologic map resource identifies glacial till (Qgt) deposits across the site and surrounding areas. The referenced SCS soil survey identifies Alderwood series soils across the entirety of the site. Alderwood soils formed in glacial till and typically present a slight to moderate erosion hazard and slow to medium runoff; and are comprised of gravelly ashy sandy loam transitioning to very gravelly sandy loam at depth_ ESNW did not observe the presence of volcanic ash in any of the test locations; but the presence of gravelly loam and sandy loam was observed at all of the test pit locations. The soil conditions observed at the test pit locations are generally consistent with glacial till deposits. Groundwater Perched groundwater was observed at several of the test pits during the fieldwork (January 2014). The groundwater was observed at an average depth of three feet. Based on our experience, groundwater seepage on till sites will typically be perched at variable depths within the substrata of glacial till soil near the contact between weathered and unweathered material; therefore, seepage should be expected in all grading activities at this site, particularly during the winter, spring and early summer months. Our fieldwork occurred during an atypically dry winter period; as such we anticipate groundwater volumes to normally exhibit higher volumes than what was observed during the fieldwork. The seepage was present at the base of the weathered native soil and where soil conditions became dense. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the wetter, winter months. Earth Solutions NW LLC American Classic Homes February 5, 2014 DISCUSSION AND RECOMMENDATIONS General ES -3220 Page 4 In our opinion, construction of the proposed residential development is feasible from a geotechnical standpoint. The proposed residential buildings can be supported on conventional continuous and spread footing foundations bearing on competent native soils, re -compacted native soils, or structural fill. Slab -on -grade floors should be supported on dense native soil or structural fill. Competent soils suitable for support of foundations should be encountered at depths of between two to four feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material will be necessary. Recommendations for foundation design, site preparation, drainage, and other pertinent geotechnical recommendations are provided in the following sections of this study. This study has been prepared for the exclusive use of American Classic Homes and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Site preparation activities will involve removal of existing structures, site clearing and stripping, and implementation of temporary erosion control measures. The primary geotechnical considerations associated with site preparation activities include building pad subgrade preparation, stormwater pond construction, underground utility installations, and preparation of pavement subgrade areas. Temporary construction entrances and drive lanes, consisting of at least 12 inches of quarry spalls can be considered in order to minimize off-site soil tracking and to provide a stable access entrance surface. Erosion control measures should consist of silt fencing placed along the down gradient side of the site. Soil stockpiles should be covered or otherwise protected to reduce soil erosion. Temporary sedimentation ponds or other approaches for controlling surface water runoff should be in place prior to beginning earthwork activities. Topsoil and organic -rich soil was encountered generally within the upper six to ten inches at the test pit locations_ Topsoil and organic -rich soil is not suitable for foundation support, nor is it suitable for use as structural fill. Topsoil or organic -rich soil can be used in non-structural areas if desired. Over -stripping of the site, however, should be avoided. A representative of ESNW should observe the initial stripping operations, to provide recommendations for stripping depths based on the soil conditions exposed during stripping. Earth Solutions NW. LLC American Classic Homes ES -3220 February 5, 2014 Page b Subgrade conditions expected to be exposed throughout the proposed building and pavement areas will likely be comprised of silty sand deposits. After the completion of site stripping and rough grading activities ESNW recommends a proofroll utilizing a fully loaded solo dump truck in order to determine the suitability of the exposed native soils for support of foundations and roadways. ESNW should be retained during this phase of earthwork to observe the proofroll and other earthwork activities. The soils exposed throughout subgrade areas should be compacted to structural fill specifications prior to constructing the foundation, slab, and pavement elements. The subgrade throughout pavement areas should be compacted as necessary and exhibit a firm and unyielding condition when subjected to the proofrolling with a loaded solo dump truck. Structural fill soils placed throughout foundation, slab, and pavement areas should be placed over a firm base. Loose or otherwise unsuitable areas of native soil exposed at subgrade elevations should be compacted to structural fill requirements or overexcavated and replaced with a suitable structural fill material. Where structural fill soils are used to construct foundation subgrade areas, the soil should be compacted to the requirements of structural fill described in the following section. Foundation subgrade areas should be protected from disturbance, construction traffic, and excessive moisture. Where instability develops below structural fill areas, use of a woven geotextile below the structural fill areas may be required. A representative of ESNW should observe structural fill placement in foundation, slab, and pavement areas, Wet Season Grading Perched groundwater was present at a number of the test pits near the contact between the weathered soil and underlying unweathered glacial till soil. This condition coupled with the moderate to high moisture sensitivity of the soil will make grading during periods of rain moderately difficult. Mass grading should take place during the late summer months when conditions are more favorable. if grading takes place during the wetter winter or spring months, a contingency in the project budget should be included to allow for export of native soil and import of structural fill as described below. In-situ Soils The soils encountered throughout the majority of the test sites have a moderate sensitivity to moisture and were generally in a moist to wet condition at the time of the exploration (January 2014). In this respect, the in-situ soils may not be suitable for use as structural fill if the soil moisture content is more than 2 to 3 percent above the optimum level at the time of construction. In general, soils encountered during the site excavations that are excessively over the optimum moisture content will require moisture conditioning prior to placement and compaction. Conversely, soils that are below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. If the in-situ soils are determined to not be suitable for use as structural fill, then use of a suitable imported soil may be necessary. Earth Solutions NW. LLC American Classic Homes February 5, 2014 Imported Soils ES -3220 Page 6 Imported soil intended for use as structural fill should consist of a well graded granular soil with a moisture content that is at or near the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well graded granular soil with a fines content of 5 percent or less defined as the percent passing the #200 sieve, based on the minus three-quarter inch fraction. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D-1557). Soil placed in utility trenches, pavement areas and in the upper 12 inches of slab -on -grade areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones, depending on the responsible utility district or jurisdiction. Foundations Based on the results of our study, the proposed residential structures can be supported on conventional spread and continuous footings bearing on competent native soils, re -compacted native soils, or structural fill. Based on the soil conditions encountered at the test pit locations, competent native soils suitable for support of foundations should be encountered at depths of between two to four feet below existing grades. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill, may be necessary. Provided foundations will be supported as described above, the following parameters can be used for design of new foundations: a Allowable soil bearing capacity 2,500 psf • Passive earth pressure 300 pcf (equivalent fluid) • Coefficient of friction 0.40 A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor -of -safety of 1.5. With structural loading as expected, total settlement in the range of one inch and differential settlement of about one-half inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Earth solutions NVV LLC American Classic Homes February 5, 2014 Seismic Desiqn Considerations ES -3220 Page 7 The 2012 IBC recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. In accordance with Table 20.1-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class C should be used for design. The referenced liquefaction susceptibility map indicates the site and surrounding areas maintain very low liquefaction susceptibility. Liquefaction is a phenomenon where saturated or loose soils suddenly lose internal strength in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. In our opinion, site susceptibility to liquefaction can be characterized as low. The relative density of the native soils, as well as the absence of a uniformly established groundwater table, were the primary bases for this characterization. Slab -On -Grade Floors Slab -on -grade floors for residential buildings constructed at this site should be supported on a firm and unyielding subgrade. Where feasible, the existing native soils exposed at the slab -on - grade subgrade level can be compacted in place to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. A capillary break consisting of a minimum of four inches of free draining crushed rock or gravel should be placed below the slab. The free draining material should have a fines content of 5 percent or less (percent passing the #200 sieve, based on the minus three-quarter inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If a vapor barrier is to be utilized it should be a material specifically designed for use as a vapor barrier and should be installed in accordance with the manufacturer's specifications, Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters can be used for retaining wall design: • Active earth pressure (yielding condition) • At -rest earth pressure (restrained condition) • Traffic surcharge for passenger vehicles (where applicable) • Passive resistance • Coefficient of friction • Seismic surcharge (active condition) 35 pcf (equivalent fluid) 55 pcf 70 psf (rectangular distribution) 300 pcf (equivalent fluid) 0.40 6H* • Seismic surcharge (restrained condition) 14H* " where H equals retained height Earth Solutions NW. LLC American Classic Homes ES -3220 February 5, 2014 Page 8 Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should be included in the retaining wall design. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. if drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with free draining material that extends along the height of the wall, and a distance of at least 18 inches behind the wall. The upper one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall, and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. Drainage Perched groundwater was observed during the fieldwork (January 2014). As such, groundwater should be anticipated in site excavations. Temporary measures to control surface water runoff and groundwater during construction would likely involve interceptor trenches and sumps. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide recommendations to reduce the potential for instability related to seepage effects. Final surface grades should slope away from structures at a gradient of at least 2 percent for a distance of ten feet. In our opinion, foundation drains should be installed along building perimeter footings. A typical foundation drain detail is provided as Plate 4. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (W1SHA) provide soil classification in terms of temporary slope inclinations. Based on the soil conditions encountered at the test pit locations, the weathered native soils encountered in the upper approximately three to four feet of the test pit locations, and where groundwater seepage is exposed, are classified as Type C by OSHANVISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.5H,1V (Horizontal:Vertical). Dense to very dense native soils encountered below about three to four feet where no groundwater seepage is exposed would be classified as Type A by OSHANVISHA. Temporary slopes over four feet in height in Type A soils must be sloped no steeper than 0.75H:1V. The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. ESNW should observe site excavations to confirm the soil type and allowable slope inclination. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should maintain a gradient of 2HAV, or flatter, and should be planted with vegetation to enhance stability and to minimize erosion. A representative of ESNW should observe temporary and permanent slopes to confirm the slope inclinations, and to provide additional excavation and slope recommendations, as necessary. Earth solutions NVV LLC American Classic Homes February 5, 2014 Utility Support and Trench Backfill ES -3220 Page 9 In our opinion, the soils anticipated to be exposed in utility excavations should generally be suitable for support of utilities. Organic or highly compressible soils encountered in the trench excavations should not be used for supporting utilities_ The native soils are moisture sensitive and will therefore be difficult to use as structural trench backfill if the moisture content of the soil is high. Moisture conditioning of the soils will likely be necessary prior to use as structural backfill. Utifity trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable City of Renton specifications. Seepage should be anticipated within utility trench excavations. Caving of the trench sidewails due to hydrostatic pressure should be anticipated by the contractor. Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To provide adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted as recommended in the "Site Preparation and Earthwork" section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade conditions will require remedial measures such as overexcavation, cement treatment, placement of a geotextile and thicker crushed rock or structural fill sections prior to pavement. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections can be considered: + Two inches of hot -mix asphalt (HMA) placed over four inches of crushed rock base (CRB), or; • Two inches of HMA placed over three inches of asphalt treated base (ATB). For relatively high volume, heavily loaded pavements subjected to moderate to high, loaded truck traffic, the following preliminary pavement sections can be considered: • Three inches of hot -mix asphalt (HMA) placed over six inches of crushed rock base (CRB), or; • Three inches of HMA placed over four and one half inches of asphalt treated base (ATB)_ The HMA, ATB and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to at least 95 percent of the maximum dry density. Final pavement design recommendations can be provided once final traffic loading has been determined. Earth Solutions NVV. LLC American Classic Homes ES -3220 February 5, 2014 Page 10 Given the presence of shallow perched groundwater, in our opinion, additional drainage measures should be considered for pavement subgrade areas. Such drainage measures could include the installation of drainlines along the sides of crowned roadways and along the centerline for roadways with inverted crowns. If areas of seepage are exposed in roadway excavations, drains should be installed in these areas to allow removal of the water. Specific recommendations and details for roadway drainage can be provided upon request. LIMITATIONS The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the test locations may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction_ Earth Solutions NW. LLC 1247h' : E STH STz i %Jf 114 7PL ?,,E AE 4 �t NE' aR 5E �'• 128TH `A 5T ei 4TH ST- I I NE IST Sr o ` ✓• - ;9 _ - � = � 'ino ' ,, f r 5E 128TH . ST� Y; P ' � JL' SiV ' Si-M r N!SE �.0 !NG Si 3 1NL 5� } ?15 Itch r -�• F "I _ sr} SE 13�RD - 5T SE 133RPI Si K PL - w T is s1 r ew u2 �j 134TH Pt SE 135-H"�, ate„ SF :.4 13ITI. �` :. r �F 133R7.PL,. 4. a' SE 13C'h c' x �. c- •. i41H a�., ¢ SF'341H 51 r T «-I STS s --_T _� SE ..a13ffTH.__ S- iE oc 's S7 SE 135"H S' x> 1F'+. 136TH ST- ���. 1 I t _ .. 1.'1� x m — •x - C tfu iSf 13 5E 1a�rxy� � - `" `�' SF w 13GTn m 57 —; _ ri3iN ,� X d•y� ��q, _737T_EI LIBER, T 137TH PL 9 H5 T!I PL _ SE 135TF! Sr sE SE t 3l7>S g SL 138TH 1 S�_ LrS I 13BYffH"- SES,a1 :3T'Y.57s ST H SF 13nTH . SE 13�FFI�-�' Pi C > '7H St 149TH s Pt R` a' WT E �' MAPLFWQOD Sf '4DiH i 'r SE ,G 'q si 'z•.Th SE '.4}Sr PL s TA15f3T� r' HEIGHTS ■ STy - 0.., 106T,15.tx s"'', 5# 14:Hi. - SE 142ND PARK _ z r " n IT Y ST SE 142ND Pt $ yl SE ti Q 5 SE 133RD S' - SE W c 144T,! vl 5f ;� SE 14331P $T cz• ,pb ~ST �. SfP14}N .� 51 4 t43RD __ crur SF 144TH'a; s ` a ri la's E ! H Sr _ MIH �E Si. �` SE 144TR SC jH4TH_ a �w SE ; 145TH 57 =- 0 x ,.. .. SF 51 145"Ht 5E W ¢ a .. Y 145TH ¢57h 7r J.y 5c s ,� SE 146TH G PI `�,� � 1597" Zt tr s4 ae•a � rt �. SE ld71N S7� � St 1�0?H v' w=y�i?H� Si h1?r '_ — �d t49,H ,,7,E ,S. SL -r. Z °.D �Q a '� IRCTsi Pt iE tifl S E �O a v e ' 16A3G _a _AY SE .. _ 'R!rp CAVANAU6H F a��tv 169 z, Q la' 9. »� POND -F ^ Y e NATURAL AREA ^3 'r,............. :.. �� _ , .SE RENTON �K , .. .IYIA.-'- MAPLE VALLEY 5E s, 5€ lSn7i+ .P1 y •b�sr .n 5L' b ST - 0 x � SE c '- - 5E 6arH .55. x MCGARVEYPARK OPENSPACE �� 'b3R7 s' _x 5E 1647H 165TH y " E VALLEY LU t HFlGNiS �: y FF E 557 S ., ' r. PARK NORTH Reference: King County, Washington Map 657 i� E G By The Thomas Guide Vicinity Map Rand McNally The Enclave at Bridal Ridge j 32nd Edition Renton, Washington NOTE: This plate may contain areas of color. ESNW cannot be Drwn_ GLS Date 02/03/2014 Proj. No- 3220 responsible for any subsequent misinterpretation of the information Checked SHA Date Feb. 2014 Plate 1 resulting from black & white reproductions of this plate. TP -2 TP -3 1 r— z E TP -1 TP -61 —7— LEGEND TP-1—I—Approximate Location of ESNW Test Pit, Proj. No. ES -3220, Jan. 2014 Subject Site Proposed Lot Number NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and 1 or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. TP -4 ETP -5 NORTH .1 120 240 1" 120' - in Feet Earth Solutions r N W r It ccion r ;sciences Test Pit Location Plan The Enclave at Bridal Ridge Renton, Washington Drwn. GLS Date 02/0312014 Proj. No. 3220 Checked SHA Date Feb. 2014 Plate 2 18" Min. p 0 p 0 p O O o uo 9 p O O jlp Oo Op �4 © �pO O 0. V o 0 0 0p°9 0� p0 pp O p � o O o opo 00 0 o a h a pQ o 0 4 0 0 oa� a p po 00 o Q p Oo oo �0b 0 0p o 0 p o0 V a o � o o Q � QO a lJ p p p9 O 0 pp p g �0� �p 0 Qo 0 0p o 0 .0 l o o 4� O (} 0.. 0 o . 0 o p o p Qo o p p O o O O p 0 O 0a 0 Q 0 O p o 8 o Q Ooao o d O 0 p .0 a 0 NOTES: • Free Draining Backfill should consist of soil hawing less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. • Sheet Drain may be feasible in lieu of Free Draining Backfill, per ESNW recommendations. • Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. Structural Fill \ Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING LEGEND: 17T =1 0 op Free Draining Structural Backfin 'rti ti ,.:ti 1 inch Drain Rock RETAINING WALL DRAINAGE DETAIL j .r.f.f.{. The Enclave at Bridal Ridge Renton, Washington Drwn. GLS Date 02103/2014 Proj. No. 3220 Checked SHA Date Feb. 2014 Plate 3 Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • Do NOT tie roof downspouts to Footing Drain. SCHEMATIC ONLY - NOT TO SCALE • Surface Seal to consist of NOTA CONSTRUCTION DRAWING 12" of less permeable, suitable soil. Slope away from building. LEGEND: Surface Seal; native soil or other law permeability material. r•r•r=r•r� 1.1.1.1• 1" Drain Rock 1111111111111114011 ra =1t r•r•r•r•r ti•4'ti'ti' - - FOOTING DRAIN DETAIL The Enclave at Bridal Ridge Renton, Washington Drwn. GLS Date 02/03/2014 Proj. No. 3220 Checked SHA Date Feb. 2014 Plate 4 J Appendix A Subsurface Exploration ES -3220 The subsurface conditions at the site were explored by excavating a total of six test pits excavated with a track -hoe across accessible portions of the property. The subsurface explorations were completed in January of 2014. The approximate test pit locations are illustrated on Plate 2 of this report. Logs of the test pits are provided in this Appendix. The test pits were excavated to a maximum depth of eight feet below existing grades. Earth Solutions NW, LLC Earth Solutions NWLLC SOIL CLASSIFICATION CHART DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. SYMBOLS TYPICAL MAJOR DIVISIONS DESCRIPTIONS GRAPH LETTER CLEAN G WELL -GRADED GRAVELS, GRAVEL - LITTLE OR NO GRAVEL GRAVELS FINES AND ° POORLY -GRADED GRAVELS, GRAVELLY SOILS (LITTLE OR NO FINES) d Q a GP GRAVEL - SAND MIXTURES. LITTLE Q °Q OR NO FINES COARSE ° 4d �° GRAINED GRAVELS WITH O GM SILTY GRAVELS, GRAVEL -SAND- SOILS MORE THAN 50% FINES SILT MIXTURES OF COARSE ° FRACTION RETAINED ON NO. 4 SIEVE (APPRECIABLEG+L+ CLAYEY GRAVELS, GRAVEL - SAND - AMOUNT OF FINES] CLAY MIXTURES SAN CLEAN SANDSSW WELL- GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES MORE THAN 50% AND - OF MATERIAL IS POORLY -GRADED SANDS, LARGER THAN SANDY ND.SIEVE SITE SI SOILS ( LITTLE OR NO FINES) SP GRAVELLY SAND, LITTLE OR NO FINES SANDS WITH [x! SM SILTY SANDS, SAND - SILT MORE THAN 50% FINES MIXTURES OF COARSE: FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE sc CLAYEY SANDS, SAND - CLAY AMOUNT OF FINES) •7L MIXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY SILTS INORGANIC CLAYS OF LOW TO FINE AND LIQUID LIMIT CL V MEDIUM PLASTICITY, GRAVELLY LESS THAN 50 CLAYS, SANDY CLAYS, SILTY GRAINED CLAYS CLAYS, LEAN CLAYS SOILS —_ OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO. 200 SIEVE SIZE SILTS LIQUID LIMITINORGANIC CH CLAYS OF HIGH THAN 50 PLASTICITY CLADS GREATER OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS " ' PEAT, HUMUS, SWAMP SOILS WITH HIGHLY ORGANIC SOILS PT HIGH ORGANIC CONTENTS < „ DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. Earth Solutions NW TEST PIT NUMBER TP -1 1805 - 136th Place N.E., Suite 201 PAGE 1 OF 1 t Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT American Classic Homes PROJECT NAME The Enclave at Bridal Ridge _ PROJECT NUMBER 3220 PROJECT LOCATION Renton, Washington DATE STARTED 1117/14 COMPLETED 1117114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION — NOTES Depth of Topsoil R Sod 8": field grass_ AFTER EXCAVATION -- w } 0' "jU Q_r v 0° TESTS U a 0 MATERIAL DESCRIPTION O d _j z C7 0 PSL '= `` 0.5 TOPSOIL Brown silty SAND with gravel, medium dense, moist (Weathered Till) �I -seepage, moderate to heavy j i -becomes unweathered and very dense MC = 16.00% I! SM f 5 I' 1 I 8. D Test pit terminated at 8.0 feet below existing grade. Groundwater seepage encountered at 2.0 feet during excavation. Bottom of test pit at 8.0 feet. Earth Solutions NW TEST PIT NUMBER TP -2 1805 - 136th Place N.E., Suite 201 PAGE 1 OF 1 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT American Classic Homes _ PROJECT NAME The Enclave at Bridal _Ridge PROJECT NUMBER 3220 PROJECT LOCATION Renton, Washington DATE STARTED 1117114 COMPLETED _1117114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION — NOTES Depth of Topsoil & Sod 6" _ AFTER EXCAVATION –_ W a. W TESTS U 0.O MATERIAL DESCRIPTION w _ M Zco U' a 0 TPSL '= 0.5 TOPSOIL Brown silty SAND with gravel, loose to medium dense, moist (Weathered Till) ii -becomes very dense and unweathered SNI I' I rJ MC = 11.90° I I 7.0 _ Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 7.0 feet. Earth Solutions NW TEST PIT NUMBER TP -3 1805 - 136th Place N.E., Suite 201 PAGE 1 OF 1 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT American Classic Homes PROJECT NAME The Enclave at Bridal Ridge PROJECT NUMBER 3220 PROJECT LOCATION Renton, Washington DATE STARTED 1117114 COMPLETED 1117114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION NOTES Depth of Topsoil & Sod 10": field grass AFTER EXCAVATION ul _ Uj U IL W m U 0_0 MATERIAL DESCRIPTION Lu� ¢z 0 PSL 0.5 TOPSOIL i i Brown silty SAND with gravel, loose to medium dense, moist (Weathered Till) ii i { -light seepage SM i� ? 1 l -becomes very dense and unweathered 5 I� i 17.0 Test pit terminated at 7.0 feet below existing grade. Groundwater seepage encountered at 3.0 feet during excavation. Bottom of test pit at 7.0 feet. Earth Solutions NW TEST PIT NUMBER TP -4 Ea, rth 1805 - 136th Place N.E , Suite 201 PAGE 1 OF i 'SolutionBellevue, Washington 98005 NwItE Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT American Classic Homes PROJECT NAME The Enclave at Bridal Ridge PROJECT NUMBER 3224 PROJECT LOCATION Renton, Washington DATE STARTED 1117/14 COMPLETED -ill 7114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION - NOTES Depth of Topsoil & Sod 6" _ AFTER EXCAVATION — u1 Lu � u! uJ U S TESTS U O MATERIAL DESCRIPTION Lu ~ a - m m z c� a 0 TPSL = 0.5 TOPSOIL i Brown silty SAND with gravel, medium dense, moist (Weathered Till) ,i I -becomes very dense and unweathered SM i 5 MC = 10.50% I 3 I �I 8.0 Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during excavation. Bottom of test pit at 8.0 feet. Earth Solutions NW TEST PIT NUMBER TP -5 1805 - 136th Place N.E., Suite 201 PAGE f OF 1 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 426-449-4711 CLIENT American Classic Homes PROJECT NAME The Enclave at Bridal Ridge ---- PROJECT NUMBER 3220 PROJECT LOCATION Renton, Washington DATE STARTED 1117114 COMPLETED 1117114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD AT TIME OF EXCAVATION — LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION — NOTES Depth of Topsoil & Sod_ 8": field grass _ AFTER EXCAVATION — LU Hw U wLU M TESTS ¢ MATERIAL DESCRIPTION Z C�7 0 TPSL ` ` '` n.5 TOPSOIL i i Brown silty SAND with gravel, medium dense, moist (Weathered Till) SM i; -becomes very dense and unweathered 5 i 15.0 -increased sand and gravel content Brown gray silty GRAVEL, very dense, moist GM (:j MC 11.10% 7.0 Test pit terminated at 7.0 feet below existing grade. No groundwater encountered during Fines = 16.10% excavation. Bottom of test pit at 7.0 feet. Earth Solutions NW TEST PIT NUMBER TP -6 1805 - 136th Place N.E., Suite 201 PAGE 1 OF 1 Bellevue, Washington 98005 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT American Classic Homes PROJECT NAME The Enclave at Bridal Ridge PROJECT NUMBER 3220 PROJECT LOCATION Renton, Washingon - DATE STARTED 1/17114 COMPLETED 1117114 GROUND ELEVATION TEST PIT SIZE EXCAVATION CONTRACTOR Client Provided GROUND WATER LEVELS: EXCAVATION METHOD _ AT TIME OF EXCAVATION _- LOGGED BY SHA CHECKED BY SHA AT END OF EXCAVATION NOTES Depth of Topsoil & Sod 6": blackberry bushes _ AFTER EXCAVATION — w _ �W U E CL � U g TESTS a p MATERIAL DESCRIPTION 0 0-7) o[[ 2 Z f7 Q Q TPSL -' o g TOPSOIL I I I Brown silty SAND with gravel, medium dense, moist (Weathered Till) I -moderate perched seepage j i -becomes very dense and unweathered SM j MC = 8.40% i i 8.0 _ Test pit terminated at 8.0 feet below existing grade. Groundwater seepage encountered at 2.5 feet during excavation. Bottom of test pit at 8.0 feet. Appendix B Grain Size Distribution ES -3220 Earth Solutions NW. LLC Report Distribution ES -3220 EMAIL ONLY American Classic Homes 9575 - 35th Street, Suite 105 Mercer Island, Washington 98040 Attention: Mr. Justin Lagers Earth Solutions NW, LLC Mw PROVIDE INNOVATIVE SOLUTIONS I HAT (;REATE VALUE ' ® RECOGNIZE THAT OUR POWER AND EFFECTIVENESS LIES WITH OUR PEOPLE ® TREAT ALL FAIRLY AND HONESTLY a ® DEDICATE OURSELVES TO BRINGING OUT THE BEST IN EVERYONE ® MAINTAIN AN ATMOSPHERE ' t OF PROFESSIONAL, FRIENDLY CUSTOMER ,RELATIONS ® CONTINUE TO SEEK OPPORTUNITIES FOR LEARNING AND GROWTH :.. ® MAINTAIN A CLEAN, WELL ORGANIZED WORK ENVIRONMENT ® IMPLEMENT CONSISTENT, RELIABLE ACCOUNTING PROCEDURES BE A RESOURCE TO THE COMMUNITY