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AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT Submitted by: PERTEET.COM 505 FIFTH AVENUE S, SUITE 300 SEATTLE, WA 98104 206.436.0515 Draft Stormwater Technical Information Report City of Renton, Washington August 2019 PARK AVENUE N EXTENS ION AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT TABLE OF CONTENTS 1.0 PROJECT OVERVIEW ....................................................................................................................................................................................... 1 PROJECT OVERVIEW............................................................................................................................................................................................. 1 1.1 EXISTING CONDITIONS ..................................................................................................................................................................................... 1 1.2 PROPOSED CONDITIONS ................................................................................................................................................................................ 2 1.3 SITE SOILS ...................................................................................................................................................................................................... 3 2.0 CONDITIONS AND REQUIREMENTS SUMMARY ................................................................................................................................... 4 3.0 OFFSITE ANALYSIS ........................................................................................................................................................................................6 3.1 UPSTREAM ANALYSIS .....................................................................................................................................................................................6 3.2 DOWNSTREAM ANALYSIS ..............................................................................................................................................................................6 4.0 FLOW CONTROL AND WATER QUALITY AND FLOW CONTROL BMPS ANALYSIS AND DESIGN .............................................. 7 4.1 EXISTING SITE HYDROLOGY ........................................................................................................................................................................... 7 4.2 PROPOSED SITE HYDROLOGY ...................................................................................................................................................................... 8 4.3 FLOW CONTROL AND WATER QUALITY THRESHOLD ANALYSIS SUMMARY ................................................................................................ 8 4.4 FLOW CONTROL IMPLEMENTATION ............................................................................................................................................................ 10 4.5 WATER QUALITY IMPLEMENTATION..............................................................................................................................................................11 4.6 FLOW CONTROL BMPS ................................................................................................................................................................................11 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................................................................................................. 12 6.0 SPECIAL REPORTS AND STUDIES.............................................................................................................................................................. 12 7.0 OTHER PERMITS ............................................................................................................................................................................................ 12 8.0 CSWPPP ANALYSIS AND DESIGN .............................................................................................................................................................. 12 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ..................................................................... 13 10.0 OPERATIONS AND MAINTENANCE MANUAL ..................................................................................................................................... 13 LIST OF TABLES TABLE 2.1 – EXPLANATION OF CORE REQUIREMENTS ................................................................................................................................................ 5 TABLE 4.3.1: FLOW CONTROL AND WATER QUALITY THRESHOLDS .........................................................................................................................9 TABLE 4.3.2: FLOW CONTROL AND WATER QUALITY THRESHOLDS ...................................................................................................................... 10 TABLE 4.6.1 – FLOW CONTROL BMP FEASIBILITY ......................................................................................................................................................11 TABLE 8.1 – SUMMARY OF ESC MEASURES ............................................................................................................................................................. 13 LIST OF APPENDICES Appendix A: -Total Information Report (TIR) Worksheets - TDA Key Map: Figures A-1 and A-2 -Existing Drainage Conditions: Figures A-3 and A-4 -Existing Land Use Map: Figures A-5 and A-6 -Upstream Basin Map: Figures A-7 and A-8 -TDA Downstream Route Map: Figure A-9 -City of Renton Record Drawings Appendix B: -Proposed Drainage Conditions: Figures B-1 and B-2 -Proposed Land Use Map: Figures B-3 and B-4 AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 1 Appendix C: -Catch Basin Catchment Areas: Figures C-1, C-2 and C-3 -Backwater Analysis Spreadsheets -Basin Flow Rates Appendix D: -Drainage Plan Sheets -Drainage Profile Sheets Appendix E: -Draft Geotechnical Report Appendix F: -Operations and Maintenance AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 1 1.0 PROJECT OVERVIEW The Park Avenue N Extension Project is the first step in creating a connection to the Southport development in order to relieve congestion at the intersection of Lake Washington Boulevard and the entrance to Gene Coulon Park. The project is located within the City of Renton just north of the intersection of Logan Avenue N and Park Avenue N and will connect the Southport Business Park with Logan Avenue N. The project is intended to enhance traffic operations and roadway conditions. Improvements include new landscaping, sidewalk, signal, and railroad crossing improvements. A Technical Information Report (TIR) Worksheet has been included in Appendix A. See the Vicinity map, below, for project location. Figure 1. Vicinity Map 1.1 Existing Conditions In the existing condition, Park Avenue N at the intersection with Logan Ave N is a five-lane roadway (two southeast-bound lanes and three northwest-bound lanes). It has an approximate width of 65 feet and is located southeast of the three-leg intersection of Park Avenue N and 757th Avenue. At the intersection of Park Avenue N and 757th Avenue, the traveled lanes transition into four lanes, heading southeast towards the intersection of AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 2 Park Avenue N and Logan Avenue N (three southeast bound lanes and one northwest bound lane with a designated buffer) as well as a two-lane bi-directional roadway traveling northeast of the project site. A curb and gutter section along the pavement improvements separates the roadway pavement from the landscaped area from the southwest corner, a small-scaled substation at the southeast corner and a graveled area located north of the project limits. This area is all part of Threshold Discharge Area (TDA) 1 Sub Basin 1. Immediately to the north and adjacent to TDA 1 is TDA 2, consisting of gravel material that is used as the primary foundation for the BNSF’s railroad tracks. Runoff landing on the railroad tracks will either infiltrate or sheet flow down the steep slope towards the northeast as it does currently (TDA 2). There is also a driveway located at the northeast corner of the intersection near the substation with a surrounding landscaped area. There is also a 12-foot sidewalk section on both the northwest and northeast corners of the intersection of Park Avenue N and Logan Avenue N marks the start of the existing sidewalk pavement. Finally, TDA 1 also contains Sub Basin 2, located approximately 550 feet to the east and downstream of the outlet for Sub Basin 1. This work consists of installing a pedestrian path beneath the train tracks near the intersection of Lake Washington Boulevard and N Southport Drive (see Appendix B). Runoff from this area will join runoff from Sub Basin 1 within ¼ mile from when the runoff discharges from Sub Basin 1. Private (Boeing owned) and public runoff has been separated within the project sites (see Appendix D). The runoff along the existing 757th Avenue roadway sheet flows longitudinally at approximately 0.4 percent from the southwest end and 0.5 percent from the northeast end. Both slope downhill towards the intersection nearest to the BNSF railway tracks. A majority of the runoff is then driven in a lateral direction towards the southeast segment of the roadway at approximately 2.0 and 2.1 percent grade, respectively. Runoff from the southwest portion of 757th Avenue then enters an existing flow control vault, located to the southeast of the intersection with Park Avenue N. Runoff exits the vault and routes towards the northeast into the existing conveyance system in Park Avenue N. On Park Avenue N, the consistent crown in the center of the roadway will have runoff converging into two low points located between 757th Avenue and Logan Avenue N. Runoff flowing from both the northwest intersection and southeast intersection will be collected by existing catch basins at those low points. From there, runoff is routed to the north and east before its outfall into Lake Washington. See Figure A-1 through A-6 for TDA layouts and existing conditions. 1.2 Proposed Conditions The proposed roadway improvements will construct a new at-grade crossing with the BNSF railroad tracks for a second access to the Southport development, while maintaining the access between the two legs of 757th Avenue. There will be three southeast bound and one northwest bound travel lanes on Park Avenue N heading towards the railroad crossing. On both sides of the roadway, there will be an eight-foot wide planter, as well as a 6-foot wide sidewalk. Curb ramps will be constructed to allow pedestrians to cross at the intersection. On the northeast leg of 757th Avenue, the 12-foot wide travel lane in each direction will be maintained and a retaining wall will be constructed at the southeast side of the intersection with Park Avenue N. This retaining wall is to minimize the impacts on the substation. At the southwest leg of 757th Avenue, there are two proposed northeast travel lanes and one southwest travel lane. At the southeast side of the intersection of Park Avenue N and 757th Avenue there is an existing substation. It is proposed to replace the existing driveway into the substation in order for vehicles to easily enter. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 3 Longitudinal slopes will become steeper at all legs of the intersection of Park Avenue N and 757th Avenue and will flatten out as it reaches the end of the project limits, where the proposed pavement will match in with the existing. Sheet flow patterns and approximate locations of low and high points will have changed throughout the entire project due to the at-grade railroad crossing. The grade change will have the proposed roadway elevation increase between 0.5 feet to 3 feet. A crown at the center of the roadway will be implemented for all legs of the project, excluding the southwest leg. For the southwest leg a transverse slope will drive runoff to sheet flow to the southeast gutter line along 757th Avenue. In the proposed condition, runoff from the entire roadway will sheet flow to gutters and be collected by a series of catch basins. The existing flow control vault located to the southwest of the intersection of Park Avenue N and 757th Avenue will not be affected as a part of this design. The design separates runoff from privately owned facilities and publicly owned. Further discussion on flow control and water quality requirements are detailed in Section 4.0 of this report. Note that the proposed improvements northwest of the BNSF railroad tracks and the proposed driveway at N 7th Street southwest along Logan Avenue N are within the project scope, but are not directly connected to the TDA boundaries. The improvements northwest of the project site are along the BNSF right-of way and sheet flows into private property (SECO). This TDA will include new train tracks and a partial road crossing over the tracks into the SECO property. The stormwater design for this private property is to be completed by others at a later date. The driveway at N 7th Street and Logan Avenue N will have a portion of runoff distributed into private property (Boeing) and the other portion will sheet flow into public property on Logan Avenue N. The generated runoff will be captured in the current existing piped conveyance system that will outfall into Lake Washington. The new driveway at N 7th Street has approximately 1,770 square feet of impervious area. In addition, a pedestrian path will be added near the intersection of Lake Washington Boulevard N and North Southport Drive. This path will allow pedestrians to cross under near the train tracks. It will connect onto the north side of Lake Washington Boulevard North. See Figures B-1 through B-4 in Appendix B of this report for proposed roadway conditions and drainage patterns. 1.3 Site Soils Based on the Natural Resources Conservation Service (NRCS) Web Soil Survey, the soils within the project area are urban land (Ur). These soils include: (1) soils that are composed of a mixture of materials differing from those in adjacent agricultural or forest areas, and that may present a surface layer greater than 50 cm, highly transformed by human activity through mixing, importing, and exporting material, and by contamination; (2) soils in parks and gardens that are closer to agricultural soils but offer different composition, use, and management than agricultural soils; and (3) soils that result from various construction activities in urban areas and that are often sealed. According to this definition, urban soils are essentially under strong human influence in urban and suburban environments; they may exert a strong effect on human health, on plants and soil organisms, and on water infiltration. They are differentiated from other strongly influenced soils such as those found in quarries, mines, and mine tailings, and airfields away from cities. However, it is sometimes difficult to set a clear boundary between urban soils and agricultural soils. The Soil Map from the NRCS Web Soil Survey is illustrated in Figure 2. A geotechnical evaluation has been completed by HWA GeoSciences, Inc (see Appendix E). The investigation performed found that topsoil was encountered within Boring Hole (BH) BH-1 and BH-2. This material was dark olive-brown and consisted of silty sand with rootlets. This layer was approximately 1 foot thick. Below the topsoil, fill was encountered in BH-1, BH-2, BH-3, and BH-5. In BH-1 and BH-2, the fill extended from the base of the AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 4 topsoil to a depth of approximately 7 feet. In BH-3 and BH-5, the fill extended to the base of the pavement section to a depth of approximately 7 feet below grade. This fill material was dark yellow-brown to olive-gray and consisted of silty sand with gravel. Alluvium was found beneath the fill in all five borings. This soil consisted of olive-gray to grayish-brown, very soft to stiff silts, and very loose to medium dense silty sands. The seasonal high groundwater table appears to be as high as 4-feet below ground surface. In addition, the site history is such that contaminated soils could be present across portions or all of the project alignment. Based on the high groundwater levels and the potential for existing contaminated soils, onsite infiltration was not recommended. Figure 2. NCRS Web Soil Survey Map 2.0 CONDITIONS AND REQUIREMENTS SUMMARY The Park Avenue N Extension Project will be designed to meet the requirements outlined in the 2016 King County Surface Water Design Manual (2016 KCSWDM), as well as the 2017 City of Renton Surface Water Design Manual (2017 CORSWDM). This project will be subject to a full drainage review to identify any requirements needed. Typically, in a full drainage review, core requirements 1 through 9 apply, including 6 special requirements. This project will be exempt from some of the core requirements and special requirements. A summary of which requirements will be required or exempt and why is provided below. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 5 Table 2.1 – Explanation of Core Requirements Core Requirement (CR) / Special Requirement (SR) Required or Exempt? Explanation CR #1 – Discharge at Natural Location Required No Exemptions to this requirement CR #2 – Offsite Analysis Required Project does create more than 2,000 square feet new impervious surface. The project is also removing 39,221 square feet of impervious surface area. It also adds less than ¾ acre of new pervious surface. However, the project does construct or modify a drainage pipe/ditch that is 12 inches or more in size/depth. CR #3 – Flow Control Exempt The project results in a reduction in impervious surface area. This reduction in impervious surface area makes this project exempt from flow control because it causes less than a 0.1 cfs increase from the existing condition to the proposed during a 100-year storm event. CR #4 – Conveyance System Required Roadway construction will make all existing conveyance ineffective; therefore, new conveyance systems will be constructed. CR #5 – Erosion and Sediment Control (ESC) Required No exemptions to this requirement CR #6 – Maintenance and Operations Required No exemptions to this requirement CR #7 – Financial Guarantees and Liability Exempt Stormwater facilities collecting runoff from privately owned sites (Boeing) will be maintained by the private entity. Stormwater facilities collecting runoff from publicly owned area will be owned and maintained by the City of Renton. CR #8 – Water Quality Facilities Exempt Project is exempt from water quality requirement because of the following: A) Total New Impervious surface is less than 50% of the existing, and B) B) Less than 5,000 square feet of new PGIS (per TDA) is proposed, and C) C) Les than ¾ acre of new PGPS is proposed. CR #9 – Flow Control BMPs Required More then 2,000 square feet of new plus replaced impervious surface is created and more than 7,000 square feet of land disturbing activity will occur. However, this project still cannot meet this requirement due to site characteristics. A majority of the site is in an area of fill. The only area within the right of way (located to the southwest of the proposed intersection) that could fit a Flow Control BMP has a high groundwater table and trace soil contaminants, based on conversations with the geotechnical engineer. Refer to the geotechnical report in Appendix E of this report for more information. These two items prohibit use of Flow Control BMPs. SR #1 – Other Adopted Area-Specific Requirements Exempt Project is not designated as an area-specific basis for any applied requirements or regulations. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 6 SR #2 – Flood Hazard Area Delineation Exempt The project is not located in a flood hazard area. SR #3 – Flood Protection Facilities Exempt Project does not rely on an existing or construct a new flood protection facility SR #4 – Source Controls Exempt Boeing improvements must comply with source control requirements of the Industrial Permit. The project is a roadway project with no proposed commercial buildings. SR #5 – Oil Control Exempt This roadway redevelopment project does not meet the 25,000 (Main Streets) and 15,000 (Intersections) traffic threshold for the High-Use menu, as estimated from Trip Generation, published by the Institute of Transportation Engineers. The project has a projected ADT of 4,450 on Park Avenue N and an ADT of 500 for 757th Avenue. SR #6 – Aquifer Protection Area (APA) Exempt The project is not located within Zone 1 or Zone 2 of the Aquifer Protection APAs (Reference Section 15-B). 3.0 OFFSITE ANALYSIS 3.1 Upstream Analysis The Park Avenue N Extension project is located at a low point of a small basin area. Runoff from 757th Ave is considered private runoff currently, as it is privately owned by Boeing. Runoff from the west side of the intersection with Park Avenue N is routed to a private Boeing Vault. This existing vault was approved under a previous design. No additional impervious area will be routed to this vault as part of this project. The current design is to protect the vault as it is and capture runoff from this vault downstream of it when it is routed into an existing catch basin in Park Avenue N. Currently, all information on this vault is solely based on limited record drawings as shown in Appendix A, existing contours, and City of Renton online GIS mapping. Flow control is provided in this vault before runoff is routed to the east in a 30-inch storm drain pipe and into an existing catch basin in Park Avenue N. It is proposed to replace this catch basin and continue routing runoff to the east and into the current outfall location for TDA 1. There is an upstream basin along 757th Avenue that is approximately 0.37 acres in size draining into the western portion of TDA 1. There is an additional basin to the east of the site that has an approximate area of 0.16 acres of offsite runoff draining onto the eastern portion of 757th Avenue. Finally, on the south side of the site there is an upstream basin of approximately 0.75 acres draining onto N Park Avenue and the landscape areas adjacent to the roadway. There is no upstream offsite runoff draining onto TDA 2. Refer to Figures A-7 and A-8 in Appendix A of this report to see locations of upstream areas which enter the Park Avenue N Extension project limits. 3.2 Downstream Analysis The downstream analysis was based upon a site visit, relative record maps and GIS provided by the City of Renton and the conducted project survey. Runoff from TDA 1 is collected by a piped conveyance system which conveys runoff to the northeast. The conveyance system leaves the project site at the eastern project limit on 757th Avenue and continues to the northeast where it outfalls into a man-made ditch immediately downstream of the ¼ mile downstream point. Runoff then routes in a northerly direction within Gene Coulon Memorial Beach Park and discharges into Lake Washington. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 7 The downstream analysis for TDA 2 is unknown as this TDA drains to the north onto private property owned by SECO. This property site has not yet been developed. Once the site is developed, the runoff will route to Lake Washington as well. Refer to Figure A-9 in Appendix A for the Downstream Route Map. 4.0 FLOW CONTROL AND WATER QUALITY AND FLOW CONTROL BMP S ANALYSIS AND DESIGN 4.1 Existing Site Hydrology There are two threshold discharge areas within the limits of the project and one discharge point per TDA. Figure A-1 and A-2 in Appendix A shows the location of the TDAs and discharge points. The TDA ownership is a combination of Boeing Company (Boeing), Burlington Northern Santa Fe (BNSF) railroad, and City of Renton right-of-way. The discharge point within TDA 1 is located at the northeast leg of 757th Avenue. For TDA 2, the runoff will sheet flow to the north onto the private property owned by SECO. See the TDA Key Map in Appendix A, Figures A-1 and A-2. Runoff contributing to the TDA 1 discharge point sheet flows to the south across the existing roadway and is collected by a series of catch basins, and then conveyed through a series of 12-inch diameter pipe segments. The collected runoff from the 757th Avenue southwest leg routes to the existing Boeing treatment vault. However, the team has been unable to find documentation of the existing stormwater system and is currently in contact with Boeing to confirm the outfall location and the purpose of the vault. Based on limited record drawings that were received (see Appendix A) it appears the treatment vault outfalls into a 36-inch diameter detention tank. The detention tank outfalls into a closed 30-inch diameter pipe. The runoff that is captured at the points along Park Avenue N is also directly connected to the 30-inch diameter pipe by a 12-inch diameter pipe coming in from the south. The conveyance system increases to a 42-inch diameter pipe before discharging into a 96-inch type 2 catch basin and continuing through the existing 42-inch piped system to a ditch before draining into Lake Washington. The project results in a loss of impervious area, resulting in less than 0.1 cfs increase of runoff from the existing condition to the proposed for the 100-year storm event. This result makes the project flow control exempt. The existing site hydrology for TDA 2 is simply runoff sheet flowing from the BNSF tracks. See Figures A-3 and A- 4 in Appendix A for existing drainage patterns, conveyance systems, and the outfall location. See Figures A-5 and A-6 in Appendix A for existing land use types. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 8 4.2 Proposed Site Hydrology The Park Avenue N Extension project is proposed to raise and rebuild the entire roadway section to match elevations at the railroad crossing, as described in the section 1.2 of this report. The proposed high point is located several feet southeast of the railroad tracks and the low points will be located near the project limits on the southwest and southeast segments near Logan Avenue N. The low points are found at STA 102+10 on the southwest segment and at the wings of both curb ramps and the refuge island at the southeast segment. There are no low points located in the northeast segment. All runoff will flow to the curb and gutters and be captured by a series of catch basins, where runoff will travel through the proposed conveyance system and discharge toward the north and east. The existing discharge location at the northeast side of the intersection will remain unchanged and the proposed pipe design will be connected to an existing 96-inch diameter type 2 catch basin. However, approximately 740 square feet of remaining runoff will sheet flow into the landscape and graveled areas where it will infiltrate. This is the same condition that exists today. The proposed site hydrology for TDA 2 will be the same as the existing condition. Runoff sheet flows from the proposed roadway crossing the tracks and from the tracks itself to the north and onto the privately owned SECO property. See Appendix B, Figures B-1 and B-2 for sheet flow characteristics, conveyance locations and outfalls. See Figures B-3 and B-4 for proposed land use types. 4.3 Flow Control and Water Quality Threshold Analysis Summary Tables 4.3.1 and 4.3.2 below summarize the existing and proposed land use areas as well as flow control and water quality thresholds for each TDA within the project (see figures A-3/A-4 and B-3/B-4 in Appendices A and B, respectively). AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 9 Table 4.3.1: Flow Control and Water Quality Thresholds TDA 1 TDA 1 Existing Condition (SF) Proposed Condition (SF) Existing PGIS to Remain 40,583 0 Existing Gravel 2,471 0 Replaced PGIS 0 33,324 New PGIS (previously Pervious or Gravel) 0 2,319 Converted PGIS (previously NPGIS) 0 482 New PGIS from Gravel 0 523 Existing NPGIS 3,844 0 Replaced NPGIS 0 3,596 New NPGIS 0 2,764 Pervious 10,421 14,311 Total TDA Area 57,319 57,319 Total Impervious 46,898 43,008 Total New Impervious* N/A 5,606 Net New Impervious** N/A -3,890 Total Replaced Impervious*** N/A 35,276 Flow Control Required? N/A No FC Amount N/A 0 SF / 0 Acres Water Quality Required? N/A No WQ Amount N/A 0 SF / 0 Acres *Sum of the all new impervious surfaces listed above (locations that will be impervious that are not in the existing condition). **Change in impervious surface (different than total new impervious because pervious surface is being placed in some locations that are currently impervious). ***Difference between the total new impervious and the net new impervious added to the replaced impervious surface rows above. PGIS – Pollution Generating Impervious Surface NPGIS – Non-Pollution Generating Impervious Surface As previously mentioned in the Core Requirements discussion and the table above, flow control and water quality will not be required. Flow control is not required because the project drains directly to Lake Washington, a flow control exempt water body. Water quality is not required because the TDA creates less than 5,000 square feet of new PGIS. Further discussion of flow control, water quality, and flow control BMPs is provided in the following sections. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 10 Table 4.3.2: Flow Control and Water Quality Thresholds TDA 2 TDA 2 Existing Condition (SF) Proposed Condition (SF) Existing PGIS to Remain 0 0 Existing Gravel 8,833 2,380 Replaced PGIS 0 0 New PGIS (previously Pervious or Gravel) 0 0 Converted PGIS (previously NPGIS) 0 0 New PGIS from Gravel 0 2,969 Existing NPGIS 0 0 Replaced NPGIS 0 0 New NPGIS 0 547 Pervious 0 2,937 Total TDA Area 8,833 8,833 Total Impervious 8,833 5,896 Total New Impervious* N/A 3,516 Net New Impervious** N/A -2,937 Total Replaced Impervious*** N/A 0 Flow Control Required? N/A No FC Amount N/A 0 SF / 0 Acres Water Quality Required? N/A No WQ Amount N/A 0 SF / 0 Acres *Sum of the all new impervious surfaces listed above (locations that will be impervious that are not in the existing condition). **Change in impervious surface (different than total new impervious because pervious surface is being placed in some locations that are currently impervious). ***Difference between the total new impervious and the net new impervious added to the replaced impervious surface rows above. PGIS – Pollution Generating Impervious Surface NPGIS – Non-Pollution Generating Impervious Surface As previously mentioned in the Core Requirements discussion and the table above, flow control and water quality will not be required. Flow control is not required because the project drains directly to Lake Washington, a flow control exempt water body. Water quality is not required because the TDA creates less than 5,000 square feet of new PGIS. Further discussion of flow control, water quality, and flow control BMPs is provided in the following sections. 4.4 Flow Control Implementation The Park Avenue N Extension project does not require any flow control facilities. The project causes a reduction in imperious area, causing the runoff from the developed conditions to have less than a 0.1 cfs increase for the 100- year storm event. The project also drains to Lake Washington, a flow control exempt water body. Therefore, the project will be exempt from implementing any flow control structures. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 11 4.5 Water Quality Implementation The Park Avenue N Extension project does not require any water quality treatment facilities. The exemption stated in the 2017 CORSWDM under Surface Exemption for Transportation Redevelopment Projects (Section 1.2.8) is that a transportation redevelopment project is exempt from water quality if the total new impervious surface within the project limits is less than 50% of the existing impervious surface AND if there is less than 5,000 square feet of new PGIS AND if less than ¾ acre of new PGPS will be added. The project is below all three of these thresholds. 4.6 Flow Control BMPs As stated in the 2016 KCSWDM, Section 1.2.9, the intent of Core Requirement #9 is “to provide mitigation of hydrologic impacts that are not possible/practical to mitigate with a flow control facility.” The project is not exempt from this requirement as more than 2,000 square feet of new plus replaced impervious surface will be created AND more than 7,000 square feet of land disturbing activity will occur. Therefore, the project should evaluate feasibility of the flow control BMP list for any replaced and existing impervious surface. Table 4.6.1 summarizes the feasibility of each BMP on the list and gives a simple explanation. Table 4.6.1 – Flow Control BMP Feasibility BMP Is it feasible? Explanation Full Dispersion No The entire site within right-of-way will be developed, leaving no native vegetation to disperse runoff to. Also, there would not be any available area to implement an onsite or offsite tract or easement area. Full Infiltration No The seasonal high groundwater table appears to be as high as 4-feet below ground surface. In addition, the site history is such that contaminated soils could be present across portions or all of the project alignment. Based on the high groundwater levels and the potential for existing contaminated soils, onsite infiltration was not recommended (see the Draft Geotechnical Report in Appendix E). Limited Infiltration No Not applicable for pollution generating impervious surfaces. It is not possible to separate out the pollution generating impervious surfaces with the non-pollution generating pervious surfaces prior to routing to a limited infiltration BMP. Basic Dispersion No The minimum vegetated flow path cannot be met. Bioretention The seasonal high groundwater table appears to be as high as 4-feet below ground surface. In addition, the site history is such that contaminated soils could be present across portions or all of the project alignment. Based on the high groundwater levels and the potential for existing contaminated soils, onsite infiltration was not recommended (see the Draft Geotechnical Report in Appendix E). Permeable Pavement No The roadway is being raised so it will be sitting on an area of fill. Rainwater Harvesting No This BMP is for roof surfaces only. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 12 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN Throughout the entire project corridor, a series of catch basins within the roadway gutter and storm pipe will collect and convey runoff. A backwater analysis of each conveyance system has been performed as part of this project to ensure that all pipes have adequate capacity and that no catch basins will overtop during the 25-year storm event. The backwater analysis has been provided in Appendix C of this report. See Figures C-1, C-2 and C-3 for catchment areas for each structure. Note that due to the limited information provided in the record drawings, the flow control vault in the southwest corner of the intersection of Park Avenue N and 757th Avenue will remain in place as shown in the proposed drainage plans (See Appendix A for the City of Renton Record Drawings and see Appendix D for the Plan and Profiles Sheets). There are no impacts anticipated to this vault. The project in fact slightly decreases the total impervious area routing to the vault. 6.0 SPECIAL REPORTS AND STUDIES A geotechnical investigation has been completed and is included in Appendix E of this TIR. 7.0 OTHER PERMITS The 2016 KCSWDM does not require any other permits for this project. 8.0 CSWPPP ANALYSIS AND DESIGN The project plans will include site preparation and erosion control plans which will show erosion and water pollution control elements. The longitudinal slope of this roadway is moderate to steep. Slopes adjacent to the project site are relatively flat with little erosion potential. Table 8.1 below summarizes how erosion and sediment control will likely be addressed during construction of this project, however, it will be up to the Contractor’s Erosion and Sediment Control (ESC) Lead to determine the most appropriate BMPs and to ensure they are installed correctly and maintained. AUGUST 2019 | STORMWATER TECHNICAL INFORMATION REPORT 13 Table 8.1 – Summary of ESC Measures ESC Category Proposed Measures Clearing Limits Silt fencing or high visibility fencing will be placed around the entire project clearing limits depending on if the grading is a cut or fill condition. Cover Measures The only steep exposed soils anticipated will be the cut/fill slopes behind the sidewalk. Seeding and mulching will likely be used to maintain these areas. Perimeter Protection Silt fence will be installed in all locations where the project site is at a higher elevation than the adjacent properties. Traffic Area Stabilization Stabilized construction entrances will be installed at all locations where construction vehicles will be entering and exiting the project site. Sediment Retention Storm drain inlet protection will be used at all new and existing catch basins and culverts to protect downstream water. Surface Water Collection No surface water collection measures are proposed at this time. Dewatering Control Dewatering may be necessary if groundwater is encountered during construction of detention facilities. Dust Control If dust becomes an issue, the contractor will spray water on exposed soils without creating runoff. Flow Control There will not be any flow control facilities constructed within the project site, since flow control is exempt from the project as mentioned in table 2.1. Control Pollutants The contractor will be required to have a certified erosion and sediment control lead on site. This person will be required to prepare a project Stormwater Pollution Prevention Plan which will address how pollutants will be controlled. Protect existing and Proposed Flow Control BMPs There is an existing flow control vault located south of the intersection of Park Avenue N and 757th Avenue. This vault is treating runoff from the Boeing facility and from 757th Avenue. This project provides a net decrease in overall impervious area and therefore is not expected to negatively impact the vault. The vault is to be protected in place during construction. Maintain BMPs No proposed flow control BMPs will be installed within the project site. Manage the Project The project specifications will call for a certified erosion and sediment control lead to be onsite. 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT The bond quantities worksheet is not required for this project because it is entirely owned and will be entirely maintained by the City of Renton. 10.0 OPERATIONS AND MAINTENANCE MANUAL Maintenance requirements for all proposed stormwater related facilities are included in Appendix F including manufacturer’s maintenance recommendations. At a minimum, all stormwater facilities should be inspected annually using the checklists included. Appendix A TIR Worksheets TDA Key Map: Figures A-1 and A-2 Existing Drainage Conditions: Figures A-3 and A-4 Existing Land Use Map: Figures A-5 and A-6 Upstream Basin Map: Figures A-7 and A-8 TDA Downstream Route Map: Figure A-9 City of Renton Record Drawings Appendix B Proposed Drainage Conditions: Figures B-1 and B-2 Proposed Land Use Map: Figures B-3 and B-4 Appendix C Catch Basin Catchment Areas: Figures C-1, C-2 and C-3 Backwater Analysis SpreadsheetsA Basin Flow Rates Backwater Analysis SpreadsheetProject Name: Park Ave N ExtensionConveyance System:Park Ave N Conveyance System :Cells will auto-calculateProject #: 20160266Designed By: Daniel RosalesDate: 7/17/2019Down CB Up CBOutfall 1-18 35.159 322 48 0.012 17.57 18.23 12.566 2.798 0.122 24.880 0.164 25.044 0.500 0.061 0.122 25.226 1.399 0.0020.4401.760 0.333 5.325 1.863 No 20.165 0.120 0.000 0.000 0.000 0.00125.10729.28 Yes1-18 1-19 0.279 46 12 0.012 18.23 21.35 0.785 0.355 0.002 25.107 0.000 25.107 0.500 0.001 0.002 25.110 0.355 0.0680.2200.220 0.128 0.128 0.254 No 21.571 0.000 90.000 1.300 0.003 0.00025.11222.68 No1-18 Detention Tank 34.534 132 48 0.012 18.23 18.49 12.566 2.748 0.117 25.107 0.065 25.171 0.500 0.059 0.117 25.347 1.374 0.0020.4401.760 0.333 5.325 1.861 No 20.421 0.116 0.000 0.000 0.000 0.00125.23328.00 YesDetention Tank EX-12 0.346 53 18 0.012 21.61 21.87 1.767 0.196 0.001 25.233 0.000 25.233 0.500 0.000 0.001 25.234 0.160 0.0050.1400.210 0.069 0.155 0.245 No 22.111 0.003 95.000 1.300 0.001 0.00025.23228.00 YesEX-12 EX-11 0.346 84 12 0.012 21.87 22.46 0.785 0.441 0.003 25.232 0.000 25.232 0.500 0.002 0.003 25.236 0.441 0.0070.2400.240 0.145 0.145 0.277 No 22.735 0.002 90.000 1.300 0.004 0.00125.23829.04 YesEX-11 1-17 0.215 56 12 0.012 22.46 25.78 0.785 0.274 0.001 25.238 0.000 25.238 0.500 0.001 0.001 25.240 0.274 0.0590.1900.190 0.104 0.104 0.222 No 25.973 0.000 45.000 0.400 0.000 0.00025.97428.78 YesEX-11 EX-13 0.102 10 8 0.012 25.31 27.05 0.349 0.292 0.001 25.238 0.000 25.238 0.500 0.001 0.001 25.240 0.358 0.1740.1900.127 0.104 0.046 0.161 No 27.154 0.000 135.000 1.300 0.002 0.00027.15629.10 YesDetention Tank EX-1 34.188 262 48 0.012 18.49 19.01 12.566 2.721 0.115 25.233 0.126 25.359 0.500 0.057 0.115 25.531 1.360 0.0020.4301.720 0.323 5.166 1.823 No 20.901 0.046 0.000 0.000 0.000 0.00225.48630.00 YesEX-1 EX-2 1.437 52 24 0.012 19.01 19.23 3.142 0.457 0.003 25.486 0.000 24.880 0.500 0.002 0.003 24.885 0.323 0.0040.2100.420 0.120 0.480 0.467 No 19.694 0.000 50.000 0.450 0.001 0.00024.88628.84 YesEX-2 1-2 1.437 36 42 0.012 19.16 19.19 9.621 0.149 0.000 24.886 0.000 24.886 0.500 0.000 0.000 24.887 0.080 0.0010.0700.245 0.024 0.296 0.320 No 19.509 0.005 50.000 0.450 0.000 0.00124.88329.14 Yes1-2 1-3 0.365 23 12 0.012 20.70 24.25 0.785 0.465 0.003 24.8830.000 24.883 0.500 0.002 0.003 24.888 0.465 0.1540.2500.250 0.154 0.154 0.287 No 24.462 0.000 90.000 1.300 0.004 0.00024.89329.17 Yes1-2 1-1 0.203 6 12 0.012 25.46 25.78 0.785 0.258 0.001 24.883 0.000 24.883 0.500 0.001 0.001 24.885 0.258 0.0530.1800.180 0.096 0.096 0.213 No 25.967 0.000 95.000 1.300 0.001 0.00025.96828.94 Yes1-2 EX-3 0.869 142 42 0.012 19.19 19.47 9.621 0.090 0.000 24.883 0.000 24.883 0.500 0.000 0.000 24.884 0.048 0.0020.0400.140 0.011 0.129 0.245 No 19.712 0.000 0.000 0.000 0.000 0.00024.88328.03 YesEX-3 EX-4 0.869 75 36 0.012 19.47 19.62 7.069 0.123 0.000 24.883 0.000 24.883 0.500 0.000 0.000 24.884 0.071 0.0020.0800.240 0.029 0.265 0.291 No 19.908 0.000 50.000 0.450 0.000 0.00024.88427.08 YesEX-4 EX-5 0.869 39 36 0.012 19.62 19.70 7.069 0.123 0.000 24.884 0.000 24.884 0.500 0.000 0.000 24.884 0.071 0.0020.0800.240 0.029 0.265 0.291 No 19.988 0.000 50.000 0.450 0.000 0.00024.88427.09 YesEX-5 EX-VAULT 0.869 67 30 0.012 19.80 20.70 4.909 0.177 0.00024.884 0.000 24.884 0.500 0.000 0.000 24.884 0.112 0.0130.1000.250 0.041 0.256 0.303 No 20.986 0.019 10.000 0.050 0.000 0.00024.86528.38 YesEX-VAULT EX-6 0.869 15 12 0.012 20.70 21.90 0.785 1.106 0.01924.865 0.000 24.866 0.500 0.010 0.019 24.894 1.106 0.0800.3900.390 0.284 0.284 0.438 No 22.310 0.019 95.000 1.300 0.025 0.00024.90026.99 YesEX-6 EX-7 0.869 123 12 0.012 21.80 21.90 0.785 1.106 0.019 24.900 0.002 24.901 0.500 0.010 0.019 24.930 1.106 0.0010.3900.390 0.284 0.284 0.438 No 22.349 0.014 90.000 1.300 0.025 0.00224.94328.03 YesEX-7 1-15 0.136 11 12 0.012 21.90 23.59 0.785 0.173 0.000 24.943 0.000 24.943 0.500 0.000 0.000 24.943 0.173 0.1540.1400.140 0.069 0.069 0.171 No 23.684 0.000 65.000 0.750 0.000 0.00024.94428.49 YesEX-7 EX-8 0.733 98 12 0.012 21.90 22.30 0.785 0.933 0.014 24.943 0.001 24.943 0.500 0.007 0.014 24.964 0.933 0.0040.3400.340 0.236 0.236 0.388 No 22.695 0.007 5.000 0.020 0.000 0.00024.95728.77 YesEX-8 EX-9 0.242 141 8 0.012 22.30 22.55 0.349 0.693 0.007 24.957 0.000 24.957 0.500 0.004 0.007 24.968 0.849 0.0020.2900.193 0.189 0.084 0.238 No 22.792 0.000 10.000 0.050 0.000 0.00024.96928.00 YesEX-1 EX-10 32.751 127 60 0.012 19.01 19.63 19.635 1.668 0.04325.486 0.031 25.517 0.500 0.022 0.043 25.582 0.746 0.0050.3101.550 0.207 5.185 1.648 No 21.293 0.042 0.000 0.000 0.000 0.00025.54028.39 YesEX-10 1-14 32.382 25 60 0.012 19.63 19.65 19.635 1.649 0.042 25.540 0.006 25.546 0.500 0.021 0.042 25.609 0.738 0.0010.3201.600 0.217 5.418 1.693 No 21.367 20.420 30.000 0.200 0.008 1.6016.79929.10 YesEX-10 Offsite 1 0.369 137 30 0.012 19.63 19.45 4.909 0.075 0.000 25.540 0.000 25.540 0.500 0.000 0.000 25.540 0.048 -0.0010.0400.100 0.011 0.066 0.187 No 19.639 0.000 95.000 1.300 0.000 0.00025.54027.83 Yes1-14 Offsite 2 28.547 115 60 0.012 19.65 19.74 19.635 1.454 0.033 6.799 0.021 6.820 0.500 0.016 0.033 6.869 0.650 0.0010.2901.450 0.189 4.725 1.544 No 21.303 0.000 0.000 0.000 0.000 0.00021.30328.61 Yes1-14 1-11 2.779 147 12 0.012 22.65 23.39 0.785 3.538 0.194 6.799 0.019 6.818 0.500 0.097 0.194 7.109 3.538 0.0050.7500.750 0.632 0.632 0.818 No 24.328 1.571 40.000 0.330 0.064 0.68523.50727.86 Yes1-11 1-13 1.582 42 12 0.012 23.39 23.92 0.785 2.014 0.063 23.507 0.002 23.508 0.500 0.032 0.063 23.603 2.014 0.0130.5300.530 0.423 0.423 0.588 No 24.542 0.785 145.000 1.300 0.082 0.00023.83827.52 Yes1-13 1-12 0.791 25 12 0.012 23.92 24.05 0.785 1.007 0.016 23.838 0.000 23.838 0.500 0.008 0.016 23.862 1.007 0.0050.2400.240 0.145 0.145 0.325 No 24.382 0.000 90.000 1.300 0.020 0.00024.40326.97 Yes1-11 1-10 1.122 48 12 0.012 23.39 23.63 0.785 1.429 0.032 23.507 0.001 23.508 0.500 0.016 0.032 23.555 1.429 0.0050.4500.450 0.343 0.343 0.501 No 24.148 1.571 15.000 0.070 0.002 0.53923.11827.66 Yes1-10 1-16 0.405 20 12 0.012 23.63 24.77 0.785 0.516 0.004 23.118 0.000 23.118 0.500 0.002 0.004 23.125 0.516 0.0570.2600.260 0.162 0.162 0.299 No 25.043 0.000 70.000 0.850 0.004 0.00025.04627.77 Yes1-10 1-7 0.209 64 12 0.012 23.63 25.32 0.785 0.266 0.001 23.118 0.000 23.118 0.500 0.001 0.001 23.120 0.266 0.0260.1900.190 0.104 0.104 0.221 No 25.529 1.571 110.000 1.300 0.001 0.00023.95929.53 Yes1-7 1-8 0.145 87 12 0.012 25.32 26.91 0.785 0.185 0.001 23.9590.000 23.959 0.500 0.000 0.001 23.960 0.185 0.0180.1500.150 0.074 0.074 0.180 No 27.082 0.000 100.000 1.300 0.001 0.00027.08229.75 Yes1-7 1-6 0.064 86 12 0.012 25.32 25.98 0.785 0.081 0.000 23.9590.000 23.959 0.500 0.000 0.000 23.960 0.081 0.0080.1000.100 0.041 0.041 0.124 No 26.101 0.785 40.000 0.330 0.000 0.00025.31532.17 Yes1-6 1-5 0.064 85 12 0.012 26.91 27.99 0.785 0.081 0.000 25.3150.000 25.315 0.500 0.000 0.000 25.315 0.081 0.0130.1000.100 0.041 0.041 0.124 No 28.108 0.785 95.000 1.300 0.000 0.00027.32332.31 Yes1-51-40.06446120.01227.9928.390.7850.0810.00027.3230.00027.3230.5000.0000.00027.3230.0810.0090.1000.1000.0410.0410.124No28.5100.00035.0000.2700.0000.00028.51031.06Yes*Flow Rates are referenced from the "Basin Flow Rates" Sheet following this spreadsheet.**Tailwater elevation in the top row is the Normal Depth of the runoff in the pipe added to the outlet invert elevation, unless pipe is partially or entirely submerged, in which case the design water surface or ordinary high water elevation should be used.***Flow area at critical depth is from the "Flow Area Chart" tab following the "Basin Flow Rates"****Determined from Figure 4.2.1.K (page 4-27) of the 2009 King County Surface Water Design Manual.Outlet Invert ElevPipe Segmant*Q (cfs)Pipe Length (ft)Pipe size (inch)Mannings "n"Inlet Submerged?Flow Area at Critical DepthQ/AD^.5Inlet Invert ElevPipe cross section (SF)Pipe Velocity (ft/s)Pipe Velocity Head**Tailwater ElevFriction Loss HGLEntrance Loss CoeficientEntrance Head LossExit Head LossOutlet Control Elev:Cells to be filled in by engineerUp CB Rim ElevationIs 6" head at the CB or Manhole? ***Flow area at critical depth/D2Inlet Control ElevApproach Velocity Head****Bend loss coeficientBend Head LossJunction Head LossHeadwater Elev.Deflection Angle (degrees)Pipe SlopeCritical Height Ratio++Critical DepthSpecific HeadX:\Renton, City of\Projects\20160266 - N Park Ave Extension\Design\Drainage\Calculations\Backwater Analysis Spreadsheet (Park Ave N) Tab: Backwater Analysis Modified King County Backwater Spreadsheet1 of 1 Basin Flow Rates Design Year Storm (2, 10, 25, or 100)?25 Ar=2.66 Br=0.65 Pr=3.4 Catch Basin Rainfall intensity Impervious C value Impervious Area (Acres) Landscaped C Value Landscaped Area (Acres) Rational Method Flow Rate (cfs) Continuous model or SBUH Flow Rate (cfs) 1-1 2.73394137 0.9 0.08230028 0.25 0 0.203 1-2 2.73394137 0.9 0 0.25 0 0 1-3 2.73394137 0.9 0.12646924 0.25 0.0780303 0.365 1-4 2.73394137 0.9 0.02596419 0.25 0 0.064 1-5 2.73394137 0.9 0 0.25 0 0 1-6 2.73394137 0.9 0 0.25 0 0 1-7 2.73394137 0.9 0 0.25 0 0 1-8 2.73394137 0.9 0.04876033 0.25 0.03636364 0.145 1-9 2.73394137 0.9 0 0.25 0 0 1-10 2.73394137 0.9 0.19908173 0.25 0.02623967 0.508 1-11 2.73394137 0.9 0.03032599 0.25 0 0.075 1-12 2.73394137 0.9 0.30879247 0.25 0.04536272 0.791 1-13 2.73394137 0.9 0.30879247 0.25 0.04536272 0.791 1-14 2.73394137 0.9 0.34777319 0.25 0.29230946 1.056 1-15 2.73394137 0.9 0.04818641 0.25 0.02522957 0.136 1-16 2.73394137 0.9 0.13471074 0.25 0.106382 0.405 1-17 2.73394137 0.9 0.08737374 0.25 0 0.215 1-18 2.73394137 0.9 0 0.25 0 0 1-19 2.73394137 0.9 0.06473829 0.25 0.17454086 0.279 EX-1 2.73394137 0.9 0 0.25 0 0 EX-2 2.73394137 0.9 0 0.25 0 0 EX-3 2.73394137 0.9 0 0.25 0 0 EX-4 2.73394137 0.9 0 0.25 0 0 EX-5 2.73394137 0.9 0 0.25 0 0 EX-VAULT 2.73394137 0.9 0 0.25 0 0 EX-6 2.73394137 0.9 0 0.25 0 0 EX-7 2.73394137 0.9 0 0.25 0 0 EX-8 2.73394137 0.9 0.19065657 0.25 0.03112948 0.491 EX-9 2.73394137 0.9 0.08684573 0.25 0.04044995 0.242 EX-10 2.73394137 0.9 0 0.25 0 0 EX-11 2.73394137 0.9 0 0.25 0 0.029 EX-12 2.73394137 0.9 0 0.25 0 0 EX-13 2.73394137 0.9 0.04116162 0.25 0 0.102 Detention Tank 2.73394137 0.9 0 0.25 0 0 Outfall 2.73394137 0.9 0 0.25 0 0 Contributing Areas to Conveyance System X:\Renton, City of\Projects\20160266 - N Park Ave Extension\Design\Drainage\Calculations\Backwater Analysis Spreadsheet (Park Ave N) Tab: Basin Flow Rates1 of 2 Basin Flow Rates Catch Basin Basin Name (if applicable) Rainfall intensity Impervious C value Impervious Area (Acres) Landscaped C Value Landscaped Area (Acres) Rational Method Flow Rate (cfs) Continuous Model or SBUH Flow Rate (cfs) Offsite 1 0.369 Offsite 2 28.547 Offsite Contributing Basins X:\Renton, City of\Projects\20160266 - N Park Ave Extension\Design\Drainage\Calculations\Backwater Analysis Spreadsheet (Park Ave N) Tab: Basin Flow Rates2 of 2 Appendix D Drainage Plan Sheets Drainage Profile Sheets 17-170 PARK AVE N EXTENSION Existing Conditions SurveyTHIS SURVEY IS IN THE CITY OF RENTON COORDINATE SYSTEMSSCOPPPJBJBJBSSCOSSCOSSCOPSDJBPJBJBJBJBJBJBICBICBICBICVJBICVJBICVXXXXXXXXXXXXJBJBTPPJBXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX X X X X XXXXXXXXXXGRAVELGRAVELPSESUBSTATIONEOTEOT4" MPE6" M P E SSCOSSCOXXCONCCONCASPHALTASPHALTASPHALTASPHALT242530262728293124302627282930313129 282827 2828293028292828900THIS SURVEY IS IN THE CITY OF RENTON COORDINATE SYSTEMSSCOPPPJBJBJBSSCOSSCOSSCOPSDJBPJBJBJBJBJBJBICBICBICBICVJBICVJBICVXXXXXXXXXXJBJBPJBXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX X X X X XXXXXXXXXXPSESUBSTATIONEOTEOT6" M P E SSCOSSCOCONCASPHALTASPHALTASPHALTASPHALT900 Aug 05, 2019 - 3:38pm rodolfo.dominguez X:\Renton, City of\Projects\20160266 - N Park Ave Extension\CADD\Plan Sheets\20160266 DR.dwg Layout Name: DR1 CITY OF RENTONPARK AVENUE N EXTENSIONDRAINAGE PLAN90% SUBMITTALPRELIMINARYNOT FOR CONSTRUCTIONCITY OFRENTON Aug 05, 2019 - 3:38pm rodolfo.dominguez X:\Renton, City of\Projects\20160266 - N Park Ave Extension\CADD\Plan Sheets\20160266 DR.dwg Layout Name: DR2 CITY OF RENTONPARK AVENUE N EXTENSIONDRAINAGE PROFILE90% SUBMITTALPRELIMINARYNOT FOR CONSTRUCTIONCITY OFRENTON Aug 05, 2019 - 3:38pm rodolfo.dominguez X:\Renton, City of\Projects\20160266 - N Park Ave Extension\CADD\Plan Sheets\20160266 DR.dwg Layout Name: DR3 CITY OF RENTONPARK AVENUE N EXTENSIONDRAINAGE PROFILE90% SUBMITTALPRELIMINARYNOT FOR CONSTRUCTIONCITY OFRENTON 121JB12324"M SD JB1241339113392OOOOOP P P PWWWW W W W W W WWWWWWWWWWWX X X X XX X X X X G G G G G G G G T T T TTTTTTT T T T T T T T T TTTTTTTTTTTT T T T TTT T T T T T G G G G GGGGGGGGGGGTTTTTTTTTTTTTTTTTP P P P W W W W W W PPPPPPPPPPPPP P P P PPP"QUEST"CONC WALKCONC WALK2530303030313232313029243132333231292928 29 293333303029232 3 29SD SD SDSDSDSDSDS D S D S D S S S S SSSSSSSSSSSSSSSSSSSSSSSSSSS S S SSSSSSSSD 121JB24" M JB12413392OOOOP PW W W W WG G G G G G G G T T T TTTTTT T T T T T T T TTT T T T TTT T T T T G G GGTTTTTTTP P P P W W W W W W PPPP P P P PPP"QUEST"CONC WALKSDSDSDS D S D S D S S S S SSSSSSSSSSS SSS Aug 05, 2019 - 12:14pm rodolfo.dominguez X:\renton, city of\Projects\20160266 - n park ave extension\CADD\plan sheets\20160266 DR.dwg Layout Name: DR490% SUBMITTALPRELIMINARYNOT FOR CONSTRUCTIONCITY OFRENTONCITY OF RENTONPARK AVENUE N EXTENSIONTRESTLE PEDESTRIAN UNDERCROSSINGDRAINAGE PLAN Aug 05, 2019 - 12:15pm rodolfo.dominguez X:\renton, city of\Projects\20160266 - n park ave extension\CADD\plan sheets\20160266 DR.dwg Layout Name: DR5 CITY OF RENTONPARK AVENUE N EXTENSIONTRESTLE PEDESTRIAN UNDERCROSSINGDRAINAGE PROFILE90% SUBMITTALPRELIMINARYNOT FOR CONSTRUCTIONCITY OFRENTON Appendix E Draft Geotechnical Report DRAFT GEOTECHNICAL REPORT PARK AVENUE N EXTENSION RENTON, WASHINGTON HWA Project No. 2017-147-21 February 22, 2019 Prepared for: Perteet, Inc. & City of Renton by: February 22, 2019 HWA Project No. 2017-147-21 Perteet, Inc. 505 Fifth Avenue S, Suite 300 Seattle, Washington 98104 Attention: Marcus Elliott, P.E. Subject: DRAFT GEOTECHNICAL REPORT Park Avenue N Extension Renton, Washington Dear Marcus; As requested, HWA GeoSciences Inc. (HWA) has performed geotechnical engineering evaluations for the proposed Park Avenue N Extension Project in the City of Renton, Washington. This draft report includes the results of our field explorations, laboratory testing, and our geotechnical engineering analysis and recommendations completed to date. This report will be finalized upon receipt of your review comments. We appreciate the opportunity to provide geotechnical engineering services for this project. If you have any questions regarding this report or require additional information or services, please contact the undersigned at your convenience. Sincerely, HWA GEOSCIENCES INC. Donald J. Huling, P.E. Principal Geotechnical Engineer Enclosure: Draft Geotechnical Report Draft Geotechnical Report i HWA GeoSciences Inc. TABLE OF CONTENTS 1. INTRODUCTION..............................................................................................................1 1.1 GENERAL .......................................................................................................1 1.2 PROJECT UNDERSTANDING ............................................................................1 1.3 SURFACE CONDITIONS ...................................................................................1 2. FIELD INVESTIGATION AND LABORATORY TESTING ......................................................2 2.1 GEOTECHNICAL SUBSURFACE EXPLORATIONS ..............................................2 2.2 GROUNDWATER PUMPING TESTS ..................................................................2 2.3 LABORATORY TESTING .................................................................................2 3. SITE CONDITIONS ..........................................................................................................3 3.1 GENERAL GEOLOGIC CONDITIONS ................................................................3 3.2 SUBSURFACE SOIL CONDITIONS ....................................................................3 3.3 GROUND WATER CONDITIONS ......................................................................4 4. CONCLUSIONS AND RECOMMENDATIONS ......................................................................4 4.1 GENERAL .......................................................................................................4 4.2 SEISMIC CONSIDERATIONS ............................................................................5 4.2.1 Seismic Design Parameters ...........................................................5 4.2.2 Soil Liquefaction ...........................................................................6 4.2.3 Liquefaction-Induced Settlement ..................................................7 4.2.4 Post Liquefaction Residual Shear Strength ...................................7 4.3 EMBANKMENT SETTLEMENT .........................................................................8 4.4 SETTLEMENT MITIGATION OPTIONS ..............................................................9 4.4.1 Over-Excavation and Replacement with Structural Fill ................10 4.4.2 Preloading ......................................................................................10 4.4.3 Lightweight Backfill ......................................................................10 4.5 SETTLEMENT MITIGATION RECOMMENDATIONS ...........................................11 4.6 SEWER AND WATER MAIN RAIL UNDERCROSSING OPTIONS .........................12 4.6.1 Open Cut Construction versus Trenchless Technology ................12 4.6.2 Anticipated Ground Conditions .....................................................13 4.6.3 Potential Trenchless Methods .......................................................13 4.6.4 Trenchless Technology Selection ..................................................14 4.6.5 Temporary Shoring for Trenchless Technology ...........................14 4.6.6 Dewatering ....................................................................................15 4.6.7 Hydraulic Conductivity Estimates .................................................16 4.6.8 Settlement Monitoring ...................................................................17 4.7 RETAINING WALL .........................................................................................17 4.7.1 Retaining Wall Design Parameter Recommendations ..................17 4.7.2 Retaining Wall Global Stability ....................................................18 4.7.3 General Retaining Wall Subgrade Preparation .............................18 4.7.4 Retaining Wall Drainage ...............................................................19 4.8 CONVENTIONAL UTILITIES ............................................................................19 4.8.1 Open-cut Excavations ....................................................................19 4.8.2 Trench Subgrade Preparation ........................................................19 4.8.3 Pipe Bedding .................................................................................20 Draft Geotechnical Report ii HWA GeoSciences Inc. 4.9 LUMINAIRE AND SIGNAL POLE FOUNDATIONS ...............................................20 4.9.1 Luminaire and Signal Pole Construction Considerations ..............22 4.10 STORMWATER MANAGEMENT .......................................................................22 4.11 PAVEMENT DESIGN .......................................................................................22 4.12 GENERAL EARTHWORK .................................................................................22 4.12.1 Structural Fill .................................................................................22 4.12.2 Trench Backfill ..............................................................................23 4.12.3 Temporary Excavations .................................................................24 4.12.4 Wet Weather Earthwork ................................................................24 5. CONDITIONS AND LIMITATIONS .....................................................................................25 6. REFERENCES .................................................................................................................27 FIGURES (Following Text) Figure 1. Site Vicinity Map Figure 2. Site and Exploration Plan Figure 3. Geologic Profile A-A’ Figure 4A. BH-4 Water Level Data Figure 4B. BH-5 Water Level Data Figure 5. Settlement Analysis – Traditional Fill Figure 6A. Limits of Cellular Concrete Placement Along Centerline Figure 6B. Limits of Cellular Concrete Placement West of Tracks Figure 7. Settlements Analysis – Cellular Concrete Figure 8. Lateral Earth Pressures for Internally Braced Temp Shoring Figure 9. Boring BH-4 Pumping Test Results Figure 10. Boring BH-5 Pumping Test Results Appendix A: Logs of HWA Explorations Figure A-1 Legend of Terms and Symbols Used on Exploration Logs Figure A-2 to A-6 Logs of Borings BH-1 to BH-5 Appendix B: Laboratory Test Results Figure B-1 to B-4 Summary of Material Properties Figures B-5 to B-20 Grain Size Distributions Figure B-21 to B-22 Atterberg Limits February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 1 HWA GeoSciences Inc. DRAFT GEOTECHNICAL REPORT PARK AVENUE N EXTENSION RENTON, WASHINGTON 1. INTRODUCTION 1.1 GENERAL This report summarizes the results of the geotechnical engineering study performed by HWA GeoSciences Inc. (HWA) for the proposed Park Avenue N Extension Project in Renton, Washington. Figure 1, Site Vicinity Map, and Figure 2, Site and Exploration Plan, show the approximate location of the project alignment just north of Logan Avenue N and Park Avenue N. Our field work included drilling five (5) machine-drilled borings. Appropriate laboratory tests were conducted on selected soil samples to determine relevant engineering properties of the subsurface soils. Engineering analyses were conducted to develop recommendations for proposed retaining walls, signal pole foundations, luminaire foundations, railroad crossing arm foundations, stormwater facilities and launching and receiving pits for sanitary sewer extension. 1.2 PROJECT UNDERSTANDING It is our understanding that the City of Renton would like to implement street improvements to accommodate the Landing and the Southport residential and office development. The improvements would extend Park Avenue North to provide access to Southport, Puget Sound Energy (PSE) property, and The Boeing Company. Sewer and water main extensions will also be implemented to tie the proposed development into existing systems which may require a trenchless excavation method, such as pipe jacking, to limit impact on the overlying railway track. The improvements will include increasing the grade along the proposed roadway; curb, gutter and pedestrian and bicycle facility; illumination, landscaping, irrigation, storm drainage and water quality treatment, and intersection and signal system improvements. 1.3 SURFACE CONDITIONS The Park Avenue N alignment runs north-northwest to south-southeast and is predominantly flat at an elevation of about 28 feet above mean sea level (AMSL). It extends from the intersection with Logan Avenue North, where Park Avenue N turns into 757th Avenue on Boeing’s right of way to the BNSF railway to the north. The existing railroad tracks cross the alignment and are elevated on a mound of railroad ballast with an elevation of about 32 feet AMSL. The PSE property is at an elevation of approximately 24 feet AMSL. The existing roadway is surfaced with Hot Mix Asphalt (HMA) pavement except at the intersection with Logan Avenue North and pedestrian crossings which are surfaced with concrete. Development along the alignment consists of heavy-industrial, residential and commercial properties. A PSE-owned electrical substation is located to the northeast of the intersection on Boeing property. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 2 HWA GeoSciences Inc. 2. FIELD INVESTIGATION AND LABORATORY TESTING 2.1 GEOTECHNICAL SUBSURFACE EXPLORATIONS Our geotechnical exploration program included surface reconnaissance of the alignment and drilling five (5) machine-drilled borings, designated BH-1 through BH-5. Boring locations were determined based on the locations of proposed improvements and are indicated on the Site and Exploration Plan, Figure 2. Three of these borings (BH-1, BH-2, and BH-3) were drilled by Geologic Drilling, Inc. of Bellevue, Washington, under subcontract to HWA. The remaining two borings (BH-4 and BH-5) were drilled by Holocene Drilling of Puyallup, Washington, under subcontract to HWA. Logs for borings BH-1 through BH-5 are presented in Appendix A of this report. In each boring, Standard Penetration Test (SPT) sampling was performed at selected intervals and the SPT resistance (“N-value”) of the soil was logged. This resistance, or N-value, provides an indication of relative density of granular soils and the relative consistency of cohesive soils. A geotechnical engineer from HWA logged the explorations and recorded pertinent information, including sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence. Soil samples obtained from the explorations were classified in the field and representative portions were placed in plastic bags. These soil samples were then taken to our Bothell, Washington, laboratory for further examination and testing. The stratigraphic contacts shown on the exploration logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and groundwater conditions depicted are only for the specific date and location reported and, therefore, are not necessarily representative of other locations and times. 2.2 GROUNDWATER PUMPING TESTS HWA completed groundwater pumping tests at the two ground monitoring wells (BH-4 and BH-5). Data collected from short-term pumping tests and grain size laboratory test results on selected soil samples were used along with applicable analytical methods to estimate hydraulic conductivity values for the subsurface soils within the project alignment. The hydraulic conductivity values are meant to be used to estimate the range of dewatering flowrates for anticipated dewatering activities associated with construction of the proposed improvements. 2.3 LABORATORY TESTING Laboratory tests were conducted at HWA’s Bothell, Washington laboratory, on selected samples retrieved from the borings to determine relevant index and engineering properties of the soils encountered at the site. The tests included visual classifications, natural moisture content, Atterberg Limits and grain size distribution. The tests were conducted in general accordance with appropriate American Society of Testing and Materials (ASTM) standards. The test results February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 3 HWA GeoSciences Inc. and a discussion of laboratory test methodology are presented in Appendix B, and/or displayed on the exploration logs in Appendix A, as appropriate. 3. SITE CONDITIONS 3.1 GENERAL GEOLOGIC CONDITIONS The project alignment is located within the Puget Lowland. The Puget Lowland has repeatedly been occupied by a portion of the continental glaciers that developed during the ice ages of the Quaternary period. During at least four periods, portions of the ice sheet advanced south from British Columbia into the lowlands of Western Washington. The southern extent of these glacial advances was near Olympia, Washington. Each major advance included numerous local advances and retreats, and each advance and retreat resulted in its own sequence of erosion and deposition of glacial lacustrine, outwash, till, and drift deposits. Between and following these glacial advances, sediments from the Olympic and Cascade Mountains accumulated in the Puget Lowland. According to the Geologic Map of King County, the project alignment is underlain by Holocene aged fill soils which are noted as being undocumented and may consist of a wide range of materials. This unit is shown to be underlain by Quaternary alluvium soils consisting of unconsolidated alluvial clay, silt, sand, gravel and cobbles. 3.2 SUBSURFACE SOIL CONDITIONS The soils encountered in our explorations consist of topsoil, fill material, and alluvial deposits. Multiple layers of alluvial material were noted alternating between silty sand and silt units. Further descriptions of soils encountered in our explorations are presented below in order of deposition, beginning with the most recently deposited. A general cross section along the project alignment is shown in Figure 3. The exploration logs in Appendix A provide more detail of subsurface conditions observed at specific locations and depths. • Topsoil: Topsoil was encountered in borings BH-1 and BH-2. This material was dark olive-brown and consisted of silty sand with rootlets. The topsoil layer extended from ground surface to a depth of approximately foot below ground surface (bgs). • Fill: Fill was encountered in borings BH-1, BH-2, BH-3, and BH-5. In BH-1 and BH-2, the fill extended from the base of the topsoil to a depth of approximately 7 feet bgs. In BH-3 and BH-5, the fill extended from the base of the pavement section to a depth of approximately 7 feet bgs. The fill material was dark yellow-brown to olive-gray and consisted of silty sand with gravel. Fill soils were likely placed during construction of the original roadway. • Alluvium: Alluvium was encountered in all five borings extending beneath the fill soils, where present, to the final depth of each boring. These soil deposits consisted of olive- gray to grayish-brown, very soft to stiff silts, and very loose to medium dense silty sands. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 4 HWA GeoSciences Inc. Alluvial deposits are often deposited as fan structures that decrease in grain size from the source stream and overlap with multiple depositional generations resulting in interbedding. 3.3 GROUND WATER CONDITIONS Ground water seepage was observed in each boring. The depth to ground water was about 5 feet bgs in BH-2, BH-3 and BH-4, about 8 feet bgs in BH-5, and about 12 feet bgs in BH-1. This seepage was observed within both the fill soils and alluvial deposits. Groundwater monitoring wells were installed at the location of borings BH-4 and BH-5. Groundwater monitoring transducers were installed in each well to monitor groundwater fluctuations over time at each location. Plots of groundwater data collected between December 21st, 2018 and January 10th, 2019 are presented in Figures 4A and 4B for borings BH-4 and BH-5, respectively. Additional groundwater information will be included in future versions of this report, or addendums, as it is collected. Prospective contractors should be prepared to encounter and manage seasonally varying ground water conditions and in response to significant precipitation events that may develop above the low permeability silt layers encountered in the alluvial deposits. Increase in volume of ground water should be expected wherever excavations bisect existing utility trenches. Existing utility trench backfill is expected to be significantly more permeable than the fine-grained alluvial deposits. Therefore, perched ground water may collect and flow along the alignment of existing utility trenches. 4. CONCLUSIONS AND RECOMMENDATIONS 4.1 GENERAL The subsurface soils along the alignment generally consist of fill underlain by alluvial deposits. The compressible layers of organic rich soils were encountered and are anticipated to be interbedded with the alluvial soils. These deposits are anticipated to undergo consolidation settlement upon the application of load and are likely liquefaction susceptible at a saturated condition when placed under the influence of the design earthquake. The nature of the alluvial soils is such that some mitigation measures will need to be implemented to support the proposed improvements such as the introduction of cellular concrete in place of traditional fill. The subsurface soils along the project alignment consist of fill and alluvial soils with varying amounts of fines. The seasonal high groundwater appears to be as high as 4-feet below ground surface in some areas. The site history is such that contaminated soils could be present across portions or all of the project alignment. Based on the high groundwater levels and the potential for existing contaminated soils, we do not recommend the use of onsite infiltration as a means of stormwater management for this site February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 5 HWA GeoSciences Inc. We understand that proposed improvements will include installation of steel casings for future water and sewer main expansion across the BNSF railroad right-of-way. We understand that the casing for the water line will be relatively shallow and installed by BNSF. We understand that the casing for the sewer would be significant deeper. In order avoid significant dewatering and shoring costs, we recommend that trenchless construction techniques be used to install the deeper sewer casing. It is our understanding that proposed improvements will require construction of a retaining wall within the project alignment. The wall is proposed to be constructed as a modular block retaining wall. The subgrade soil conditions in the vicinity of this wall appear to be adequate to provide support for the wall. However, some scarifying and re-compaction of the disturbed medium dense to dense near-surface fill materials will be required and if soft spots are encountered additional remedial measures may be required. We understand that proposed improvements include installation of luminaire structures and signal poles. The subgrade soils along the alignment are such that nonstandard foundation design for lateral bearing capacity of the associated foundations is anticipated at all proposed locations. 4.2 SEISMIC CONSIDERATIONS 4.2.1 Seismic Design Parameters Earthquake loading for the proposed improvements was developed in accordance with Section 3.4 of the AASHTO Guide Specifications for LRFD Bridge Design, 2nd Edition, 2011 (AASHTO, 2011 with 2012, 2014 and 2015 Interim Revisions) and the Washington State Department of Transportation (WSDOT) amendments to the AASHTO Guide Specifications provided in the Bridge Design Manual (WSDOT, 2017). For seismic analysis, the Site Class is required to be established and is determined based on the average soil properties in the upper 100 feet below the ground surface. Based on our characterization of the subsurface conditions, the site class designation has been determined based on the principle that the consistency of the soils below the maximum depth of the borings are consistent or denser than the soil within the 61½ feet of depth explored. For this project, SPT blow counts obtained from our borings were utilized to classify the subject site as Seismic Site Class D. Therefore, Site Class D should be used with AASHTO seismic evaluations for this project. Table 1 presents recommended seismic coefficients for use with the General Procedure described in AASHTO (2011), which is based upon a design event with a 7 percent probability of exceedance in 75 years (equal to a return period of 1,033 years). February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 6 HWA GeoSciences Inc. Table 1. Seismic Coefficients for Evaluation Using AASHTO Guide Specifications calculated by USGS Seismic Hazard Map Site Class Peak Horizontal Bedrock Acceleration PBA, (g) Spectral Bedrock Acceleration at 0.2 sec Ss, (g) Spectral Bedrock Acceleration at 1.0 sec S1, (g) Site Coefficients Peak Horizontal Acceleration PGA, (g) Fpga Fa Fv D 0.434 0.989 0.283 1.166 1.104 2.033 0.506 Based on the above parameters the Peak Ground Acceleration, PGA (As) for Site Class D at the project site is 0.506 g. 4.2.2 Soil Liquefaction Liquefaction is a temporary loss of soil shear strength due to earthquake shaking. Loose, saturated cohesionless soils are the most susceptible to earthquake-induced liquefaction; however, recent experience and research has shown that certain silts and low-plasticity clays are also susceptible. Primary factors controlling the development of liquefaction include the intensity and duration of strong ground motions, the characteristics of subsurface soils, in-situ stress conditions and the depth to ground water. Based on the WSDOT Geotechnical Design Manual (GDM), the liquefaction susceptibility of the soils along the project alignment was determined utilizing the simplified procedure originally developed by Seed and Idriss (1971), updated by Youd et al (2001) and Idriss and Boulanger (2004, 2006). The simplified procedure is a semi-empirical approach which compares the cyclic resistance ratio (CRR) required to initiate liquefaction of the material to the cyclic shear stress ratio (CSR) induced by the design earthquake. The factor of safety relative to liquefaction is the ratio of the CRR to the CSR; where this ratio is computed to be less than one, the analysis would indicate that liquefaction is likely to occur during the design earthquake. The CRR is primarily dependent on soil density, with the current practice being to base it on the Standard Penetration Test (SPT) N-value, corrected for energy consideration, fines content and earthquake magnitude. CSR is generally determined by the formulation developed by Seed and Idriss (1971) and relates equivalent shear stress caused in the soil at any depth to the effective stress at that depth and the peak ground acceleration at the surface. Ground water elevations were approximately 5 feet bgs at the site. Our explorations encountered fill soils underlain by interbedded alluvial sands, alluvial silts, and organic silts across the site. Based on the subsurface conditions encountered at the site, the potential for liquefaction is February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 7 HWA GeoSciences Inc. considered to be high at the site during a seismic event due to very shallow groundwater and loose liquefaction susceptible soils. Liquefaction analysis was completed utilizing LiquefyPro v5.9a. Results of our studies indicate that most of the encountered alluvial soils beneath the approximate 7 feet of fill soils would liquefy under a strong earthquake of magnitude 6.96 with a PGAm of 0.506g. Our analyses indicate that the loose to medium dense saturated fill and alluvial soil deposits, encountered below the project alignment, will liquefy during the 1,033-year design earthquake. As the alluvial soils extend past the termination depth of our geotechnical borings, we expect that potentially liquefiable soils will extend to great depths below the alignment, assuming the layers are fully saturated. 4.2.3 Liquefaction-Induced Settlement Unsaturated loose sand deposits tend to densify when they are subject to earthquake shaking. For saturated sand deposits, excess pore water pressure builds up during the earthquake excitation, leading to loss of strength or liquefaction. After the shaking stops, excess pore water pressures dissipate toward a zone where water pressure is relatively lower, usually the ground surface. The dissipation is accompanied by a reconsolidation of the loose sand (Ishihara and Yoshimine, 1992 & Tokimatsu and Seed, 1987). The reconsolidation is manifested at the ground surface as vertical settlement, usually termed as liquefaction-induced settlement or seismic settlement. The potential for liquefaction-induced settlement was evaluated at the railroad crossing. The methodologies used were developed by Idriss and Boulanger (2008) and are generally based on the relationship between cyclic stress ratio, corrected SPT blow counts, and volumetric strain. Using these methods, liquefaction-induced settlement at railroad crossing was estimated to be between 7 to 12 inches. We expect that the liquefaction-induced settlement will be differential in nature between the approaches on either side and the railroad crossing. The proposed railroad crossing should be designed to be able to handle these liquefaction-induced settlements and associated differential settlements between crossing and the adjacent road approaches on either side. Some proposed improvements may require reconstruction as a result of liquefaction induced settlements. Based on our analysis of liquefaction within observed soils in the borings we calculate that up to 14 inches of total liquefaction induced settlement may occur at this site. Differential settlements are difficult to determine but are anticipated to be as high as 7 inches over a 50 foot span. 4.2.4 Post Liquefaction Residual Shear Strength Upon initiation of liquefaction and the completion of earthquake shaking, the shear strength of the liquefiable soils may reduce to a residual shear strength. Residual shear strengths for the liquefiable soils encountered within the project alignment were determined using a weighted average of the results of the Seed (1987), Seed and Harder (1990), Olson and Stark (2002), Idriss February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 8 HWA GeoSciences Inc. and Boulanger (2007) and Kramer (2008) relationships. The residual shear strengths assigned are a function of the equivalent clean sand SPT value, (N1)60cs, the potential for void redistribution, and the initial effective overburden stress. Given the permeable nature of the overlying fill soils, we assumed void redistribution effects we be negligible when determining an estimate of residual shear strength. Post liquefaction residual shear strengths were used to evaluate retaining wall stability and non-standard signal pole foundations 4.3 EMBANKMENT SETTLEMENT It is our understanding that the proposed improvements will include raising the site grades to facilitate the proposed railroad crossing. These grade increases will result in increased load applied to the subsurface soils. As compressible soils are present across the site, we expect that prosed grade increases will result in consolidation settlements. Consolidation settlement results from the application of static loading on compressible soil deposits that are saturated and have not previously experienced similar loading conditions. Consolidation settlement occurs as both primary consolidation (short term consolidation) and secondary consolidation (long term consolidation). Both of these mechanisms are described below. Primary consolidation occurs immediately upon the application of load and is a result of pore water being expelled from the void space within the soil unit. As load is applied, the pore water pressure increases within the soil unit and slowly decreases as the pore water is expelled from the soil. As this process continues the void space is reduced and the volume of the soil deposit decreases. This decrease in the volume results in a reduction in the thickness of the soil unit which manifests as settlement at the ground surface. The magnitude of primary consolidation is dependent on the geometry of the compressible soil unit, with respect to the applied load, and the compressibility properties of the subject soil. Secondary compression is a settlement phenomenon that occurs in soil deposits on completion of the primary consolidation stage and can continue for many years. The magnitude of the secondary compression settlement is difficult to predict but is typically a small fraction (5 to 10%) of the settlement that occurs as primary consolidation for most mineral soils. Our primary settlement estimates are based on the results of Atterberg limit correlations for soils in which undisturbed samples were not obtained. A tabulation of primary consolidation properties for the underlying compressible soils is provided in Table 2. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 9 HWA GeoSciences Inc. Table 2 Soil Properties Used to Calculate Primary Consolidation Settlement Soil Type Laboratory Test Soil Boring Sample Number Depth of Sample (ft) Compression Index Cc Initial Void Ratio (eo) Compression Ratio (Ccε) Silt (ML) Atterberg Limits BH-1 S-4 10 to 11.5 0.29 1.2* 0.13 Silt (OH) Atterberg Limits BH-4 S-12 40 to 41.5 1.8 4.6 0.32 *Initial void ratio estimated from Atterberg Limit test results. We evaluated the anticipated consolidation settlements across the site based on the assumption that proposed fill area was constructed with conventional fill soils. The results of this analysis indicate that the use of conventional fill to construct the proposed improvements would result in settlement of both the proposed roadway and the existing railroad tracks. The settlement would be largest on the west side of the tracks, where the fill thickness is greatest. Static (non-seismic) settlements as great as 2 inches could occur along the railroad tracks due to construction of the roadway in this manner. Figure 5 shows anticipated primary settlement magnitudes across the site with call outs along the centerline of the road and along the centerline of the railroad tracks. It should be noted that secondary static settlement, roughly equal to 10 percent of the primary settlements shown in Figure 5, should also be expected. Constructing the proposed roadway with conventional fill would result in a localized sag in the rail line. We expect that this sag will not be acceptable by BNSF. Therefore, we recommend that settlement mitigation be implemented to minimize impacts to the roadway and railroad tracks. 4.4 SETTLEMENT MITIGATION OPTIONS The magnitude of anticipated primary and secondary settlement associated with the proposed site grading is sufficient to induce damage to the proposed improvements and existing railroad tracks. Therefore, we recommend that settlement mitigation measures be implemented to protect the existing railroad, proposed roadway and utilities. There are several settlement mitigation measures that could be implemented to reduce or eliminate potential settlements associated with the compressible soils below the site. These mitigation February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 10 HWA GeoSciences Inc. options include over-excavation and replacement, lightweight fill, preloading and pile supporting improvements. A description of each of these propped options is provided below. 4.4.1 Over-Excavation and Replacement with Structural Fill Where compressible soils are located near the ground surface over-excavated and replaced with compacted structural fill could be implemented to eliminate the potential of future settlements. However, subsurface investigations indicate that compressible soils were observed to extend to great depths across the site. Therefore, over-excavation and replacement would require very deep exactions that would require significant shoring. Additionally, the groundwater level along the project site is such that over-excavation and replacement would most likely require dewatering. Due to the anticipated cost of over-excavation and replacement, we do not believe that it is a viable settlement mitigation option for the entire project area. 4.4.2 Preloading Preloading the road site would also be a viable way to reduce future settlements of the underlying compressible soils. Preloading involves placing a specified amount of soil or weight over a given area and allowing the weight to consolidate the underlying compressible soils prior to construction of the proposed improvements. Preloading has been used successfully on similar projects in the past. However, the viability of preloading requires time and space. We would expect the silt to take between 6 to 12 months to complete primary settlement. Therefore, a preload would need to be in place for at least 6 months to 1 year in order to successfully eliminate future settlements. We would expect that the placement of a preload would cause significant disruptions to Puget Sound Energy (PSE) and Boeing operations due to its required size and location. Additionally, preloading would require the existing utilities to be diverted during the preload operation to prevent damage. Preloading would also result in a significant sag in the BNSF tracks. Based on the time requirements, the anticipated disruption, damage to the BNSF tracks, necessity to relocate the utilities during preloading, we do not believe that preloading the compressible soils is a viable option for this project. 4.4.3 Lightweight Backfill Lightweight material could be used to offset the load of proposed fill in order to eliminate the application of additional load on the underlying compressible soils. Several lightweight fill materials are available and have been used on past projects with success. These materials include Geofoam, bottom ash, light weight volcanic rock, glass cutlet and lightweight cellular concrete. Geofoam consists of proprietary light weight Styrofoam blocks that are readily available to contractors and have been used successfully on numerous road projects. Geofoam can be obtained in a variety of unit weights. However, geofoam requires encapsulation in a sealed geomembrane to protect against degradation due to exposure to hydrocarbons. Additionally, geofoam would require the construction of a load distribution slab to allow for traffic loads over the foam. Therefore, given the cost associated with these items, geofoam may not be suitable for this project. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 11 HWA GeoSciences Inc. Bottom Ash is a byproduct of coal fired power plants and weighs between 45 and 75 pounds per cubic foot. Bottom ash has been used on several road projects but is becoming hard to obtain. Light weight volcanic rock has been used as light weight fill in the past. Light weight volcanic rock generally weights approximately 45 to 60 pounds per cubic foot. However, there are no readily available sources of light weight volcanic rock in Washington State. Therefore, the cost associated with importing the material would be prohibitive for this project. Lightweight cellular concrete is a proprietary product that can be manufactured onsite to a wide range of unit weights (27 pcf to 120 pcf) and compressive strengths to match project requirements. Cellular concrete is widely available in Washington State and has been used successfully on road projects. Cellular concrete does not require encapsulation within a geomembrane and would not require a load distribution slab. Although it is not recommended, cellular concrete can be excavated for future utility needs if required. Additionally, the use of cellular concrete does not require the use of heavy compaction and vibration equipment which could lead to the deformation of soils around and below the railroad. We have received cost estimates ranging from $55 to $100 per cubic yard for cellular concrete on past projects. We believe that light weight cellular concrete would be a viable settlement mitigation measure for this project. 4.5 SETTLEMENT MITIGATION RECOMMENDATIONS Given the soil geometry and location of the project site, most of the above described settlement mitigation options present significant challenges that make them less favorable for this project. We recommend that cellular concrete be utilized as a settlement mitigation measure for this project. Cellular concrete should be used to offset the dead loads associated with the proposed grade increases, resulting in a no-load increase scenario. This will require excavation and removal of 4 to 5 feet, depending on location, of existing soils and replacement with cellular concrete that will extend to the roadway subgrade elevation. HWA has conducted settlement analysis to determine the lateral extent of the cellular concrete that would be required to limit settlement of the BNSF railroad tracks to no more than 1/4 -inch. Our analysis indicates that cellular concrete must extend a minimum of 30 feet from the centerline of the railroad tracks to limit track settlement to ¼-inch. The cellular concrete geometry utilized in this analysis is provided in Figure 6A and Figure 6B. The orientation of the cross section provided in Figures 6A and 6B is shown in Figure 2. Anticipated site settlements, based on this geometry of cellular concrete, are provided in Figure 7. As shown in Figure 7, some roadway settlement is expected to occur outside of the cellular concrete placement area. If these settlements are not desirable, additional cellular concrete placement would be required to further reduce roadway settlements. Where placed, cellular concrete should consist of Type II cellular concrete, possessing a cast density ranging from 27 to 30 pounds per cubic foot and a minimum compressive strength of 40 to 50 pounds per square inch. The cellular concrete should be placed in a maximum 4-foot thick layers. Cellular concrete does not require the installation of a gasoline resistant geomembrane. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 12 HWA GeoSciences Inc. The cellular concrete should be installed with a cover of at least 2 feet of compacted structural fill to offset buoyancy forces in the event of seasonally high ground water levels. 4.6 SEWER AND WATER MAIN RAIL UNDERCROSSING OPTIONS We understand the City plans to install a new sewer and water line under the railroad tracks as part of this project. All installed underground utilities crossing the railroad right of way should be installed in accordance with BNSF’s Utility Accommodation policy, dated May 18, 2011. It is our understanding that the team is considering trenchless excavation methods for installation of the deep sewer extension across the BNSF right-of-way. It is also our understanding that a sleeve for the proposed the water main will be installed at a shallow depth by BNSF prior to construction of the city project. Further discussion related to the use of trenchless technology versus open cut methods are discussed below. 4.6.1 Open Cut Construction versus Trenchless Technology We understand the use of standard cut and cover trenching methods are being considered for installation of the proposed sewer and water lines under the BNSF rail corridor. We expect that standard cut and cover trenching methods would be the best option for installation of the shallow water line. We understand that the City is currently in communications with BNSF to install a casing at the proposed water line alignment and depth, as part of a BNSF planned track regrading effort. If the water line casing is to be installed at depths less than approximately 4-5 feet below ground surface, we expect that installation, with standard trenching techniques, will be feasible and dewatering will not be required. If the water lien casing is deeper than 4-5 feet, standard trenching will likely still be feasible, however, some dewatering with sumps and pumps will be required. Unlike the water line, the proposed sewer undercrossing is to be installed at a depth of 10 to 15 feet below existing ground surface. Installation of the sewer undercrossing with conventional cut and cover techniques would result in several challenges. The proposed sewer alignment is located below the groundwater table. Therefore, significant dewatering would be required to install the proposed utility in the dry. Given the sandy nature of the near surface soils, dewatering would be costly and could result in settlement of the compressible soils in the area. Additionally, the past uses of the site suggest that contaminated soils and groundwater may be present across the site. Pumping large volumes of potentially contaminated groundwater would be challenging from a treatment and discharge prospective. Sheet pile shoring and a mud seal could be sued to open cut and install the sewer line. However, this method of installation would likely require more time than BNSF is willing to provide. Based on these challenges, we would not recommend the use of conventional cut and cover installation methods for the sewer undercrossing. We would recommend that the sewer undercrossing be constructed with trenchless technologies. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 13 HWA GeoSciences Inc. 4.6.2 Anticipated Ground Conditions Ground conditions along the proposed trenchless alignment are anticipated to consist of fill and relatively loose alluvial soil deposits, with a ground water level near the existing ground surface. The anticipated ground conditions along the trenchless crossing are depicted in the Geologic Profile, Figure 3. The alluvial deposits are expected to vary significantly in composition from location to location. The silt and organic silt layers encountered in the geotechnical borings should not be assumed to be connected or uniform from location to location. Although not encountered in our borings, the alluvial soils could contain large woody debris or other objects that could result in obstructions to various construction activities. 4.6.3 Potential Trenchless Methods Given the currently proposed geometry of the sewer undercrossing, we recommend that the undercrossing be installed using trenchless installation techniques. Several methods of trenchless construction are available to install the proposed sewer under the existing railroad tracks. HWA recommends that a jack and bore method be applied utilizing either an auger boring or microtunnelling procedure. A description of each of these methods is provided below. Pipe Jacking The pipe jacking method is a trenchless method which involves hydraulically-jacking a prefabricated steel or equivalent jackable pipe, such as reinforced concrete pipe, from a jacking pit to a receiving shaft through the subsurface soils. After each segment of pipe has been installed, the rams of the jack are retracted, and another pipe segment is placed in the jacking pit and attached to the previous pipe segment. Spoils are removed from the face of the bore using an auger or, in the case of micro- tunneling, a circulating slurry. Auger Boring Auger borings involve excavation at the face using a cutting head attached to an auger. In general, auger boring is not considered a “steerable” trenchless method and pipeline segments between the jacking and receiving pits are straight. However rudimentary steering capability is available with a steering head in front of the first pipe section. In loose, soft, or wet soils, the auger and cutting head are generally kept inside the leading edge of the casing to help control raveling into the face of the bore. If obstructions are encountered, the augers can be retracted to allow manned access to the face for obstruction removal by manual methods such as jackhammering or drilling and splitting. Microtunneling Microtunnelling is a jack and bore method that involves the use of a steerable closed-face rotating excavator in front of the first pipe section. A circulating slurry of drilling fluid is pumped through the face of the bore, with the exiting slurry carrying out the excavated soil. Unlike auger boring, microtunnelling uses a remote- controlled tunneling machine that is laser guided and is a steerable method, though it is February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 14 HWA GeoSciences Inc. generally used for straight pipe alignments. If obstructions are encountered, the obstruction cannot generally be accessed from the excavation, but rather rescue shafts must be excavated. Microtunnelling provides continuous support to the excavation face of the bore by controlling the pressure of the circulating slurry. This method is especially effective when shallow groundwater conditions and loose soils are anticipated as the pipeline alignment does not usually need to be dewatered, except at the jacking and receiving pits. 4.6.4 Trenchless Technology Selection Bidding contractors should be allowed to select the means and methods for trenchless construction, including the diameter of the casing pipe. We recommend a minimum bore-and- jack casing diameter of 36 inches and a maximum diameter of 60 inches. In our experience, BNSF will require the jacked casing pipe to be steel having a minimum wall thickness of 1.5 inches. They are likely to require the casing pipe be backfilled after installation of the carrier pipes. Given the shallow groundwater conditions encountered on site at the time of our explorations, we anticipate the utilization of micro-tunneling will be most suitable. Trenchless construction by bore and jack methods should proceed up-slope so that water entering the bore will drain to the jacking pit for removal. We expect the Contractor’s jacking pit to be a steel sheet pile enclosure about 20 feet wide and 30 feet long. A concrete floor would be cast in the bottom of the jacking pit to provide a firm base for the jacking equipment. The receiving pit would typically be somewhat smaller and may or may not be enclosed with sheet piles. 4.6.5 Temporary Shoring for Trenchless Technology For excavation and construction of the receiving and jacking pits, for trenchless construction, we recommend temporary shoring consisting of internally braced sheet piles to provide a relatively water tight shoring enclosure. Once the sheet piles are installed, soils inside the shoring can be excavated to the desired depth. The embedment depth of the sheet piles below the base of the excavation should be designed by the Contractor to adequately cutoff underground water seepage for stability of the subgrade soils at the base of the excavation. Recommended design earth pressures for temporary sheet pile shoring are shown on Figure 8. Shoring should be designed and constructed to support lateral loads exerted by the soil mass. In addition, any surcharge from construction equipment, construction materials, excavated soils, or vehicular traffic on adjacent roadways should be included in the shoring design. However, we recommend that the contractor be required to submit a shoring/excavation plan for review prior to construction. The plan should be required to contain specific measures for temporary support and protection of all existing utilities and structures. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 15 HWA GeoSciences Inc. Precautions should be taken during removal of the shoring to minimize disturbance of the pipe, underlying bedding materials, and native subgrade soils. The contractor should be responsible for control of ground and surface water and should employ sloping, slope protection, ditching, sumps, dewatering, and other measures as necessary to prevent sloughing of soils. 4.6.6 Dewatering Ground water levels measured at the time of our exploration program indicate the local ground water table is as shallow as 5 feet below existing ground surface. It is our understanding that the exact location and extents of the launching and receiving pits and the final depth of the sewer main have not been determined at this time. We anticipate trench depths of up to 15 feet below grade. Jacking/receiving pit excavations will therefore extend below the ground water table. The contractor should be prepared to deal with shoring and ground water during construction. The contractor should anticipate that they will have to lower the water table 8 to 13 feet within the jacking/receiving pit excavations in order to construct the pipeline under relatively dry conditions. Limited information on seasonal changes in ground water level or surface water flows was available at the time this report was prepared; however, dewatering requirements and associated costs will be minimized if construction is performed during periods of seasonal low ground water levels and surface water flows. Extended dewatering with deep wells resulting in water lowering over a large area, could cause consolidation of the underlying alluvial soils, particularly in highly organic soils. The magnitude of the settlement and its areal extent would depend on the amount of change in the water level, the length of time the water level was lowered, and the compressibility and thickness of the underlying soils. Therefore, we recommend that dewatering wells be installed inside the sheet pile enclosures of the jacking/receiving pits. We recommend that the dewatering well screens and the sheet pile embedment depths be designed to limit drawdown of the groundwater outside of the sheet pile enclosures. In the vicinity of settlement-sensitive structures, such as the railroad tracks, ground water monitoring wells should be established between the excavation and the structure to observe changes. The City and/or Contractor should survey the elevation of settlement sensitive structures prior to dewatering and monitor for settlement during construction. We recommend the contractor be required to submit a dewatering plan for review by HWA to evaluate other potential impacts. We recommend the plans and specifications include provisions requiring contractors to maintain a minimum and maximum draw-down from dewatering. The contractor could use existing monitoring wells to aid in the determination of the effectiveness of the dewatering system. However, design and implementation of any dewatering system remains the responsibility of the contractor. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 16 HWA GeoSciences Inc. 4.6.7 Hydraulic Conductivity Estimates We expect that some form of dewatering will be required to construct the proposed improvements. In order quantify the magnitude of anticipated dewatering, HWA completed both grain size analysis and single well pump tests to estimate the hydraulic conductivity of the subsurface soils underlaying the project site. Grain Size Analysis HWA estimated the saturated hydraulic conductivity (K) of selected soil samples using equations presented in Vukovic and Soro (1992) that calculate hydraulic conductivity from the particle size distribution of the soil. These methods were modified and adapted to a spreadsheet-based tool by Devlin (2015). Each of 15 analytical methods developed by various authors to estimate K from grain size data is limited in applicability to certain soil characteristics such as the range of particle sizes or the largest or smallest particle size. HWA selected the most permeable samples in the depth ranges of anticipated excavation (5-20 feet) for estimation of K. HWA input soil particle size distribution data to the program HydrogeoSieveXL (Devlin, 2015), which estimated K for all methods, but only selects those that meet the suitability criteria for each method. Pump Test Analysis Short term, single well, pumping tests were conducted at BH-4 and BH-5 using a 12 volt electrical submersible pump. Response to pumping, and recovery after pumping, were measured using datalogging pressure transducers. BH-4 was pumped at a rate of 0.32 gallons per minute (gpm) for 30 minutes and exhibited a maximum of 0.4 feet drawdown. BH-5 was pumped at a rate of 1.7 gpm for 40 minutes and exhibited a maximum of 1.4 feet drawdown. Results of these pumping tests are provided in Figures 9 and 10 for borings BH-4 and BH-5, respectively. We used several methods to analyze the pumping and recovery test results. HWA analyzed the results of the pumping tests with the Aquifer Test for Windows software (Rohrich, 1996). Overall, estimated hydraulic conductivities obtained from the pump tests were lower than those estimated from grain size testing, possibly due to the relatively low achievable flow rates in two- inch diameter wells, and the use of bentonite during drilling to control heave. However, based on the results of both analyses, we estimate that the Hydraulic conductivity of the subsurface soils range from 10 in/hr to 288 in/hr. As water is expected to find the path of least resistance (most permeable layers) during dewatering, assuming a design hydraulic conductivity of 288 in/hr would be prudent based on available data. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 17 HWA GeoSciences Inc. 4.6.8 Settlement Monitoring As the proposed trenchless alignment passes under an existing railroad, settlement monitoring of the ground surface and railroad tracks will be required. Settlement monument points should be installed at the ground surface along the proposed alignment and monitored during trenchless construction on a daily basis. 4.7 RETAINING WALL The proposed improvements will require construction of a gravity retaining wall, designated as Wall No. 1, as shown on the Site and Exploration Plan, Figure 2. The wall will consist of a modular block retaining wall between 2 – 5 feet tall. Specifics associated with the proposed wall are indicated in Table 3. Table 3. Summary of Proposed Wall Type and Location Wall Designation Side of 757th Avenue Wall Application Max Wall Height (ft) Proposed Wall Type Relevant Exploration Wall No. 1 South Fill Wall 5 Gravity Block Boring BH-3 (Figure 2) 4.7.1 Retaining Wall Design Parameter Recommendations We assume that retaining wall No. 1 will consist of a gravity block wall system. The wall will consist of a proprietary wall system that the wall supplier will design for internal stability. The wall should be designed in accordance with AASHTO Standard Specifications for Highway Bridges. We recommend the wall be designed using the parameters presented in Table 4. For the Extreme Event I Limit State, the wall shall be designed for a horizontal seismic acceleration coefficient kh of one-half the peak ground acceleration or 0.253 g and a vertical seismic acceleration coefficient kv of 0.0 g (assuming the wall is free to move during a seismic event). Extreme Event I Limit State is defined in the AASHTO Standard Specifications as a safety check involving an extreme load event resulting from an earthquake in combination with the dead load and a fraction of live loads. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 18 HWA GeoSciences Inc. Table 4. Recommended Gravity Block Wall Design Parameters Parameters to be Used for the Gravity Block Wall Soil Properties Wall Backfill* Retained Soil* Foundation Soil Unit Weight (pcf) 135 135 120 Friction Angle (deg) 36 35 32 Cohesion (psf) 0 0 0 AASHTO Load Group 1 AASHTO Load Group II Allowable Bearing Capacity (ksf) 3.0 4.5 Horizontal Seismic Acceleration Coefficient, kh (g) 0.253 * Gravel Borrow, as specified in Section 9-03.14(1) of WSDOT Standard Specifications * If geogrid reinforcing is to be used the gravel borrow should be limited to a maximum particle size of 1¼ inches. 4.7.2 Retaining Wall Global Stability Using the computer program SLIDE 5.0, we evaluated static, seismic and post liquefaction global stability of the proposed gravity block wall. Analyses were completed utilizing site topography determined in the field and wall geometry provided by Perteet. Factors of safety for static global stability in excess of 1.5 were calculated given the geologic conditions and a minimum wall embedment of 2 feet. Seismic stability was evaluated using a pseudo-static horizontal acceleration of 0.253 g, which is ½ of the peak ground acceleration (PGA) associated with the 1:1033-ye ar design earthquake for this site location, as is standard of practice for yielding walls. From our analyses, we conclude that, under a design earthquake, a factor of safety for global stability greater than 1.1 will exist. Post liquefaction stability was evaluated using static loading condition and residual shear strengths for the liquefiable soils. From our analyses, we conclude that, under post liquefaction conditions, a factor of safety for global stability greater than 1.1 will exist. Based on our analysis we conclude that the global stability of the wall will be adequate under static, seismic, and loading conditions if wall embedment of at least 2 feet is maintained for the wall. 4.7.3 General Retaining Wall Subgrade Preparation Subgrade preparation is important to limit differential settlement of the wall and maintain global stability. Disturbed, loose or soft soil conditions, as determined by HWA, should be removed and replaced with “Structural Backfill” in accordance with Section 4.12.1 of this report or be compacted to a firm and unyielding state as determined by HWA. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 19 HWA GeoSciences Inc. All areas on which the wall will bear should be graded level perpendicular to the wall face and compacted in accordance with Section 2-03.3(14)D of the WSDOT Standard Specifications (WSDOT, 2018). We recommend an HWA geotechnical engineer, or their representative, be present during construction to verify the foundation of the wall requirements provided in this report are met. We recommend the bottom of the retaining wall be placed on a 1-foot-thick leveling pad consisting of crushed surfacing base course (CSBC) compacted to 95 percent of Modified Proctor Maximum Dry Density, as determined by ASTM D 1557. This leveling pad should be graded to establish the proper wall batter. 4.7.4 Retaining Wall Drainage Proper wall construction and drainage is essential to prevent premature failure of the wall system. We recommend installing a 6-inch-diameter perforated drain pipe behind the wall to convey all collected water to a suitable outlet. The pipe should be bedded and backfilled with Gravel Backfill for Drains, as specified in Section 9-03.12(4) of the WSDOT Standard Specifications (WSDOT, 2018). The drain pipe should be sloped to drain and routed to an appropriate discharge location. 4.8 CONVENTIONAL UTILITIES 4.8.1 Open-cut Excavations We understand open-cut trenching will be used for all other utility improvements aside from being considered for the sewer main crossing under the BNSF right-of-way. Trench excavations for the pipelines can be accomplished with conventional excavation equipment such as backhoes and trackhoes. Trench excavation should be made with a smooth-edge (toothless) bucket or a bucket with a plate welded over the teeth to minimize disturbance to the pipe subgrade. Although not reported on the exploration logs, there is a potential for oversize objects, such as boulders or buried logs, to be encountered in the excavations. All open-cut excavations should be completed in accordance with Section 4.12.3 of this report. 4.8.2 Trench Subgrade Preparation Subgrade preparation and verification should be performed at the base of all excavations. This work should be observed by the geotechnical consultant. Any soft or yielding materials identified at the base of the excavation should be removed and replaced with trench backfill as directed by the geotechnical consultant in the field. Any loose materials should be compacted prior to placement of pipe bedding or foundation pad for manhole structures. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 20 HWA GeoSciences Inc. 4.8.3 Pipe Bedding The soils at, or near, the bottom of the proposed sewer line and manhole excavations are expected to consist of slightly silty to silty sand. We do not recommend pea gravel for use as pipe bedding material or backfill. To provide suitable support and bedding, we recommend the pipes be founded on suitable bedding material, such as Gravel Backfill for Pipe Zone Bedding meeting the requirements of Section 9-03.12(3) of the Standard Specifications (WSDOT, 2018). Pipe bedding should provide a firm uniform cradle for support of the pipes. A minimum 4-inch thickness of bedding material beneath the pipe should be provided. Prior to installation of the pipe, the pipe bedding should be shaped to fit the lower part of the pipe exterior with reasonable closeness to provide uniform support along the pipe. Pipe bedding material should be used as pipe zone backfill and placed in layers and tamped around the pipe to obtain complete contact. To protect the pipe, bedding material should extend at least 12 inches above the top of the pipe. 4.9 LUMINAIRE AND SIGNAL POLE FOUNDATIONS We understand the proposed improvements include installation of luminaire and signal poles along the project alignment. Based on subsurface soil conditions encountered during our explorations, non-standard foundation designs will be required for both luminaire and signal pole foundations. Since a non-standard design is recommended, the estimated friction angle and the passive pressure to assume when using the Brom’s method recommended in the Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (AASHTO, 2013) are provided below in Table 5 & 6. Table 5 illustrates the design properties that should be utilized for the proposed structural fill that will be used to regrade the project site. Given the soil variability observed across the site, Table 6 illustrates the recommended design parameters, based on the soil conditions encountered in each of our subsurface explorations. The recommended parameters provided in Tables 5 and 6 should be used for non-standard foundation designs across the project site. We recommend that the design of specific foundations be based on the parameters associated with the nearest geotechnical boring to the subject foundation. It should be noted that liquefiable soils exist at each proposed foundation location. The onset of liquefaction will result in the reduction in the shear strength of the potentially liquefiable soils. Therefore, additional parameters are proved at each boring location for the post liquefaction condition. These parameters should be considered for the liquefaction condition. Table 5 Recommended Design Parameters for Signal Pole and Luminaire Foundations for Proposed Fill Soils Soil Type Ф (deg) Kp Moist Unit Weight (pcf) Buoyant Unit Weight (pcf) Factor of Safety Structural Fill 36 3.9 140 NA 3 February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 21 HWA GeoSciences Inc. Table 6: Recommended Design Parameters for Signal Pole and Luminaire Foundations for Existing Soils Boring Condition Soil Type Saturated Depth (ft) Ф (deg) Kp Moist Unit Weight (pcf) Buoyant Unit Weight (pcf) Factor of Safety BH-1 Static/Pseudo-Static Fill Unsaturated 0’ - 7’ 36 3.9 125 NA 3 Alluvium Unsaturated 7’ - 12' 26 2.5 120 NA 3 Alluvium Saturated 12' - Bottom 28 2.8 110 47.6 3 Post LQ Alluvium Saturated 12' - Bottom 10 1.4 110 47.6 3 BH-2 Static/Pseudo-Static Fill Unsaturated 0’ - 5’ 29 2.9 125 NA 3 Fill Saturated 5’ - 7' 36 3.8 125 62.6 3 Alluvium Saturated 7' - Bottom 27 2.6 110 47.6 3 Post LQ Fill/Alluvium Saturated 5' - Bottom 5 1.2 110 47.6 3 BH-3 Static/Pseudo-Static Fill Unsaturated 0’ - 5’ 36 3.9 125 NA 3 Fill Saturated 5’ - 7' 35 3.7 120 62.6 3 Alluvium Saturated 7' - Bottom 31 3.1 135 72.6 3 Post LQ Alluvium Saturated 7' - Bottom 5 1.2 135 72.6 3 BH-4 Static/Pseudo-Static Alluvium Unsaturated 0' - 5' 27 2.6 135 NA 3 Alluvium Saturated 5’ - 7 27 2.6 135 72.6 3 Alluvium Saturated 7 - Bottom 30 3.0 130 67.6 3 Post LQ Alluvium Saturated 5' - Bottom' 8 1.3 130 67.6 3 BH-5 Static/Pseudo-Static Fill Unsaturated 0’ - 7’ 38 4.2 125 NA 3 Alluvium Unsaturated 7’ - 9' 32 3.3 120 NA 3 Alluvium Saturated 9' - Bottom 32 3.3 110 47.6 3 Post LQ Alluvium Saturated 9' - Bottom 10 1.4 110 47.6 3 February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 22 HWA GeoSciences Inc. 4.9.1 Luminaire and Signal Pole Construction Considerations While not encountered in any of our explorations, the contractor should anticipate and make allowance for potential obstructions during advancement of the shaft excavations. Obstructions could be encountered in both the fill and the alluvial soil deposits. The shaft excavations for the proposed luminaire and signal pole locations will extend through loose and sometimes saturated fill and alluvial soils for the various proposed locations across the project. The contractor should, therefore, be prepared to case the shaft excavations. Without careful casing placement and soil excavation, the loose to medium dense fill and alluvial soils are susceptible to caving resulting in detrimental loss of ground. Should this occur, it may be necessary to recover ground loss through immediate backfilling of the caved areas with controlled density fill (CDF), followed by re-drilling of the shaft(s) after the CDF has set sufficiently. Ground water was encountered in all the exploration borings. Therefore, ground water seepage into shaft excavations is expected to occur throughout the project alignment. Where ground water seepage is encountered and standing water is present at the base of the excavation, concrete should be pumped to the base of the excavation rather than end-dumped from the surface, to facilitate displacement of the standing water. 4.10 STORMWATER MANAGEMENT It is our understanding that onsite infiltration is a desirable means of stormwater management for this site. However, the relatively shallow nature of the groundwater across the site, presence of near surface fine grained soils and the potential for soils and groundwater contamination across the site are such that the use of onsite infiltration is not recommended. WE recommend that other means of stormwater management be implemented for this site. 4.11 PAVEMENT DESIGN It is our understanding that pavement design for the project will be completed by Perteet. Therefore, no pavement design evaluations or recommendations have been completed by HWA. 4.12 GENERAL EARTHWORK 4.12.1 Structural Fill The site soils have a high fines content and are expected to be highly moisture sensitive. Therefore, we do not recommend that the site soils be reused as structural fill for this project. We recommend that structural fill for this project consist of imported clean, free-draining, granular soils free from organic matter or other deleterious materials. The structural fill material should be less than 4 inches in maximum particle dimension, with less than 7 percent fines (portion passing the U. S. Standard No. 200 sieve), as specified for “Gravel Borrow” in Section February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 23 HWA GeoSciences Inc. 9-03.14(1) of the WSDOT Standard Specifications (WSDOT, 2018). The fine-grained portion of structural fill soils should be non-plastic. Structural fill soils should be moisture conditioned and compacted to the requirements specified in Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications (WSDOT, 2018); except the standard of compaction achieved shall not be less than 95% of the Maximum Dry Density (MDD) determined for the fill material by test method ASTM D1557 (Modified Proctor). Subgrade compaction in road bed areas should conform to the requirements of Section 2-06.3(1) of the WSDOT Standard Specifications (WSDOT, 2018). Achievement of proper density of a compacted fill depends on the size and type of compaction equipment, the number of passes, thickness of the layer being compacted, and soil moisture- density properties. In areas where limited space restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required relative compaction. Generally, loosely compacted soils result from poor construction technique and/or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet, and coarse-grained materials easily become too dry, for proper compaction. 4.12.2 Trench Backfill Existing materials along the alignment are anticipated to consist of silty sand and silt. Where these materials are encountered below the ground water table, they are likely to be too wet for compaction; however, these materials may be suitable for re-use as trench backfill if they can be properly moisture conditioned and placed within 3 percent of the optimum moisture content and meet the required compaction standard of 95 percent of maximum dry density as determined by ASTM D1557 (Modified Proctor). If import materials are needed we recommend using clean, free-draining, granular such as Gravel Borrow as specified in Section 9-03.14(1) of the Standard Specifications (WSDOT, 2018) or Bank Run Gravel for Trench Backfill as specified in Section 9-03.19 of the Standard Specifications (WSDOT, 2018). As with the native materials, import materials should be placed within 3 percent of their optimum water content and compacted to 95 percent of their maximum dry density as determined by ASTM D1557. Trench backfill should be placed in lifts with a maximum uncompacted thickness of 8 to 12 inches (depending upon the nature of the fill material and the compaction equipment used) and densely compacted in a systematic manner. The contractor should develop compaction methods that consistently produce adequate compaction levels. All backfilling operations should be monitored full-time by a qualified inspector and a sufficient number of in-place density tests should be performed as the fill is placed to determine that the required compaction is being achieved. During placement of the initial lifts, the trench backfill material should not be bulldozed into the excavation or dropped directly on the pipe. Furthermore, heavy vibratory equipment should not February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 24 HWA GeoSciences Inc. be permitted to operate directly over the pipe until a minimum of 2 feet of backfill has been placed over the pipe bedding. A significant cause of trench settlement is inadequate shoring practices and inadequate compaction during shoring removal and backfilling. Special care must be taken to obtain good compaction up to the edges of the excavation as the shoring is removed. Moreover, attention must be paid to ensure good compaction around manholes. 4.12.3 Temporary Excavations Excavations on site can be accomplished with conventional excavating equipment such as backhoes and trackhoes. Because of the nature of the alluvial soils, the high ground water table, potential for flowing sands, and the depths of excavation, some excavations may require advance dewatering and shoring. Maintenance of safe working conditions, including temporary excavation stability, is the responsibility of the contractor. In accordance with Part N of WAC (Washington Administrative Code) 296-155, latest revisions, all temporary cuts in excess of 4 feet in height should be sloped or shored. The existing native soils generally consist of very loose to loose sands and silty sands. These sand deposits, when de-watered, generally classify as Type C soil, per WAC 296-155, and, if no trench box is used, should be sloped no steeper than 1½H:1V (Horizontal:Vertical). Flatter side slopes will be required where ground water seepage is encountered. Lateral support for the trench walls should be provided by the contractor to prevent loss of ground and possible distress to nearby ditches or roads. General recommendations for design and implementation of shoring and bracing systems are presented below. • Trench boxes should provide suitable support for trench excavations in native sandy soils provided the ground water level is lowered to at least 3 feet below the base of the excavation and settlement sensitive structures or utilities are not situated near the excavation. • Where a trench box is used to support an excavation in the alluvial soils, one or both sides of the trench are likely to cave against the box. The caving may extend out on either or both sides of the trench for a distance approximately equal to the depth of the trench. As a result, we recommend any excavations be positioned such that the nearest side of the trench box is at a distance no less than the depth of the excavation plus 10 feet from the nearest edge of the ditch. 4.12.4 Wet Weather Earthwork General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. These recommendations should be incorporated into the contract specifications. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 25 HWA GeoSciences Inc. • Earthwork should be performed in small areas to minimize exposure to wet weather. Excavation of unsuitable and/or softened soil should be followed promptly by placement and compaction of clean structural fill. The size and type of construction equipment used may need to be limited to prevent soil disturbance. Under some circumstances, it may be necessary to excavate soils with a backhoe to minimize subgrade disturbance caused by equipment traffic. • For wet weather conditions, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight of the portion of the fill material passing the ¾-inch sieve. The fines should be non-plastic. It should be noted this is an additional restriction on the structural fill materials specified. • The ground surface within the construction area should be graded to promote surface water run-off and to prevent ponding. • Within the construction area, the ground surface should be sealed on completion of each shift by a smooth drum vibratory roller, or equivalent, and under no circumstances should soil be left uncompacted and exposed to moisture infiltration. • Bales of straw and/or geotextile silt fences should be strategically located to control erosion and the movement of soil. 5. CONDITIONS AND LIMITATIONS We have prepared this report for the City of Renton and Perteet, Inc. for use in design of this project. This report should be provided in its entirety to prospective contractors for bidding and estimating purposes; however, the conclusions and interpretations presented in this report should not be construed as our warranty of the subsurface conditions. Experience has shown that soil and ground water conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations and may not be detected by a geotechnical study. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, HWA should be notified for review of the recommendations of this report, and revision of such if necessary. We recommend HWA be retained to review the plans and specifications to verify that our recommendations have been interpreted and implemented as intended. Sufficient geotechnical monitoring, testing, and consultation should be provided during construction to confirm the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should conditions revealed during construction differ from those anticipated, and to verify that the geotechnical aspects of construction comply with the contract plans and specifications. Within the limitations of scope, schedule and budget, HWA attempted to execute these services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology in the area at the time the report was prepared. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 26 HWA GeoSciences Inc. No warranty, express or implied, is made. The scope of our work included environmental assessments or evaluations regarding the presence or absence of hazardous substances in the soil or ground water at this site. Our findings are presented in the Soil Characterization Report. HWA does not practice or consult in the field of safety engineering. We do not direct the contractor’s operations and cannot be responsible for the safety of personnel other than our own on the site. As such, the safety of others is the responsibility of the contractor(s). The contractor(s) should notify the owner if it is considered that any of the recommended actions presented herein are unsafe. We appreciate the opportunity to provide geotechnical services on this project. Should you have any questions or comments, or if we may be of further service, please do not hesitate to call. Sincerely, HWA GEOSCIENCES INC. Zakeyo Ngoma, P.E. Donald J. Huling, P.E. Geotechnical Engineer Principal Geotechnical Engineer February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 27 HWA GeoSciences Inc. 6. REFERENCES American Association of State Highway and Transportation Officials, 2011, AASHTO guide specifications for LRFD seismic bridge design. Washington, DC: American Association of State Highway and Transportation Officials. Booth, D.B., Cox, B.F., Troost, K.A. and Wisher, A.P. 2007. Geologic Map of King County. University of Washington. Seattle, Washington. Scale 1:100,000. Burlington Northern Santa Fe, 2011, Utility Accommodation Policy, Engineering Services, BNSF Railway. Devlin, J.F., 2015, HydrogeoSieveXL: an Excel-Based Tool to Estimate Hydraulic Conductivity From Grain-Size Analysis, Hydrogeology Journal, DOI 10.1007/s10040- 015-1255-0. Idriss, I.M, and Boulanger, RW, 2004, Semi-Empirical Procedures for Evaluating Liquefaction Potential During Earthquakes, presented at the Joint 11th ISCDEE & 3rd ICEGE, January, 2004. Idriss, I.M. and Boulanger, R.W., 2007, SPT- and CPT-Based Relationships for the Residual Shear Strength of Liquefied Soils, Earthquake Geotechnical Engineering, 4th International Conference on Earthquake Geotechnical Engineering, K. D. Pitilakis, ed., Springer, The Netherlands, 1-22. Idriss, I.M. and Boulanger, R.W., 2008, Soil Liquefaction During Earthquakes, Earthquake Engineering Research Institute, Oakland, California, MNO-12. Idriss, I.M., and Boulanger, R.W., 2006, “Semi-empirical procedures for evaluating liquefaction potential during earthquakes”, Soil Dynamics and Earthquake Engineering, 11th International Conference on Soil Dynamics and Earthquake Engineering (ICSDEE): Part II, Volume 26, Issues 2–4, February–April 2006, Pages 115–130. Idriss, I.M., and Boulanger, R.W., 2007, Residual Shear Strength of Liquefied Soils, Proceedings of the 27th USSD Annual Meeting and Conference, Modernization and Optimization of Existing Dams and Reservoirs. Ishihara, K., and M. Yoshimine, 1992, Evaluation of settlements in sand deposits following liquefaction during earthquakes, Soils and Foundations 32(1), 173–188. Kramer, S.L., 2008, Evaluation of Liquefaction Hazards in Washington State, Washington State Department of Transportation, Report WA-RD. Olson, S.M. and Stark, T.D., 2002. Liquefied Strength Ratio from Liquefied Flow Failure Case Histories, Canadian Geotechnical Journal, Vol. 39, June, PP629-647.3 Powers, J. Patrick, 1992. Construction Dewatering, New Methods and Applications, John Wiley & Sons, Inc. Seed, H.B. and Idriss, I.M., 1971, Simplified Procedure for Evaluating Soil Liquefaction Potential. Journal of Soil Mechanics Foundation Division, ASCE, Vol. 97, No. SM9, pp. 1249-1273. Seed, R.B. and Harder, L.F. (1990) SPT-Based Analysis of Cyclic Pore Pressure Generation and Undrained Residual Strength. In: Duncan, J.M., Ed., Proceedings of the H.B. Seed Memorial Symposium, Vol. 2, BiTech Publishers, Richmond, 351-376. February 22, 2019 HWA Project No. 2017-147-21 Draft Geotechnical Report 28 HWA GeoSciences Inc. Tokimatsu, K., and H.B. Seed, 1987, Evaluation of Settlements in Sands Due to Earthquake Shaking, Journal of Geotechnical Engineering Volume 113, Issue 8. Vukovic, M., Soro, A., 1992, Determination of Hydraulic Conductivity of Porous Media From Grain-Size Composition. Miladinov, D., translator, Water Resources Publications, Littleton, Colorado, USA. Wiley & Sons, Inc. WSDOT, 2015, Geotechnical Design Manual, Washington State Department of Transportation. WSDOT, 2018, BridgeLink, Version 1.1.8, Computer Software. WSDOT, 2018, Standard Specifications for Road, Bridge, and Municipal Construction, Washington State Department of Transportation. Youd, T.L., Idriss, I.M, et al., 2001, Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils, Journal of Geotechnical and Geoenvironmental Engineering, Geo-Institute of the American Society of Civil Engineers (ASCE), Vol. 127, No. 10, October, 2001. © 2019 Microsoft Corporation © 2019 DigitalGlobe ©CNES (2019) Distribution Airbus DS © 2019 Microsoft Corporation © 2019 HERE HWA GEOSCIENCES INC. DRAWN BYCHECK BY DATE: ZN BFM 01.21.2019 FIGURE #1 PROJECT # 2017-147-21 VICINITY MAP S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\2017-147-21 SITE PLAN.DWG <Fig 1> Plotted: 2/19/2019 1:48 PM PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON 0 200 400 600 800 SCALE: 1" = 400' VICINITY MAP SITE MAP 0 1000 2000 3000 4000 SCALE: 1" = 2000' SITE PROJECT AREA 17+0016+0015+00SITE AND EXPLORATION PLAN 2 FIGURE NO. PROJECT NO. 2017-147-21 DRAWN BY BFM CHECK BY ZN DATE 01.21.2019 S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\2017-147-21 SITE PLAN.DWG <Fig 2> Plotted: 2/22/2019 10:55 AM PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON BASE MAP PROVIDED BY: PERTEET 0 20 40 60 80 SCALE: 1" = 40' PARK AVENUE NORTH EXTENSION Scale: 1" = 40'-0"SOUTHPORT DR. N.EXPLORATION LEGEND BH-1 APPROXIMATE LOCATION AND DESIGNATION OF GEOTECHNICAL BORINGS BH-1 BH-2 BH-3 BH-4 BH-5 PARK AVE . N . LOGA N A V E NA A' CROSS SECTIONA'A BB' C C' A A' ? ?? ? ?? ? ?????? EXISTING GRADE PROPOSED GRADE BH-4(STA. 14+98.03, 24.46'RT)BH-3(STA. 15+88.66, 23.23'LT)BH-5(STA. 16+06.31, 91.70'RT)BH-1(STA. 16+92.71, 47.80'LT)BH-2(STA. 17+03.44, 43.77'RT)3 FIGURE NO. PROJECT NO. 2017-147-21 DRAWN BY BFM CHECK BY ZN DATE 01.21.2019 S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\2017-147-21 SITE PLAN.DWG <Fig 3> Plotted: 2/19/2019 3:26 PM PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON GEOLOGIC CROSS-SECTION A-A' 14+00 14+20 14+40 14+60 14+80 15+00 -45' INFERRED GEOLOGIC CONTACT EXPLORATION DESIGNATION BOTTOM OF EXPLORATION WATER LEVEL IN WELL AND DATE BLOW COUNT "N-VALUE "BH-3LEGEND ELEVATIONSOILS LEGEND ALLUVIUM FILL 15+20 15+40 15+60 15+80 16+00 16+20 16+40 16+60 16+80 17+00 17+20 17+40 -50' -40' -35' -25' -20' -15' -10' -5' 0' 5' 10' 15' 20' 25' 30' 35' 40' 45' -30' STATION FILL ALLUVIUM The subsurface conditions shown are based on widely spaced borings and should be considered approximate. Furthermore the contact lines shown between units are interpretive in nature and may vary laterally or vertically over relatively short distances on site. A A' BNSF R/W 4.1 4.2 4.3 4.4 4.5 4.6 4.7Ground Water Level Below Ground Surface(ft)Date and Time BH-4 Ground Water Elevation BH-4 WATER LEVEL DATA 2017-147-21 FIGURE NO. PROJECT NO. North Park Avenue Extension Renton, Washington 4A 8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8Ground Water Level Below Ground Surface(ft)Date and Time BH-5 Ground Water Elevation BH-5 WATER LEVEL DATA 2017-147-21 FIGURE NO. PROJECT NO. North Park Avenue Extension Renton, Washington 4B Park Avenue N Extension - 60% Plans Page 004.pdn SETTLEMENT ANALYSIS – TRADITIONAL FILL PARK AVENUE NORTH EXTENSION SEATTLE, WASHINGTON 5 2017-147 FIGURE NO. PROJECT NO. NOTES • Settlements are presented in inches and distances are in feet. • Settlement analysis was performed assuming fill heights acquired by comparing the existing topographic profiles to the proposed fill grades provided by Perteet. • Conventional fill material was assumed for this analysis (unit weight of 140 pcf). Settlements Observed along the railway tracks. Settlements observed along roadway alignment. Maximum Settlement of 8.67 inches. Proposed Grade Light Weight Cellular Concrete Type II Structural Fill 1.5 1 No Excavation Permitted by BNSF Zone C Shoring Zone A Shoring Zone B Shoring Zone C ShoringZone A Shoring Zone B Shoring Light Weight Cellular Concrete Type II Structural Fill 2 1 1.5 1 Existing Railway ~3.4 Feet 7 Feet 6 Inches 30 Feet 12 Feet 6 Inches 12 Feet 12 Feet 6 Inches Excavation Permitted by BNSF 7 Feet 6 Inches ~3.4 Feet Offset required of Cellular Concrete 12 Feet Excavation Permitted by BNSF ~1.8 Feet Existing Grade ~5.0 Feet ~3.8 Feet ~2.0 Feet ~2.0 Feet 1 Traditional Fill 1.5 6A FIGURE NO. PROJECT NO. 2017-147-21 DRAWN BY SKS CHECK BY DJH DATE 02.06.2019 S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\EXCAVATION DETAILS\2018-147-021 EXCAVATION DETAILS.DWG <Parallel> Plotted: 2/22/2019 11:56 AM LIMITS OF CELLULAR CONCRETE PLACEMENT ALONG CENTERLINE PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON NTS B B' 4 1 Proposed Roadway Light Weight Cellular Concrete Structural Fill ~3.0 Feet ~ 69 Feet ~5.0 Feet ~3.0 Feet ~2.0 Feet 1.5 1 HWA GEOSCIENCES INC. DRAWN BYCHECK BY DATE: DJH SKS 02.06.2019 FIGURE #6B PROJECT # 2017-147-21 LIMITS OF CELLULAR CONCRETE PLACEMENT ALONG CENTERLINE S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\EXCAVATION DETAILS\2018-147-021 EXCAVATION DETAILS.DWG <Perpendicular> Plotted: 2/22/2019 11:56 AM PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON NTS C C' Park Avenue N Extension - 60% Plans Page 004.pdn SETTLEMENT ANALYSIS – CELLULAR CONCRETE PARK AVENUE NORTH EXTENSION SEATTLE, WASHINGTON 7 2017-147 FIGURE NO. PROJECT NO. NOTES • Settlements are presented in inches and distances are in feet. • Settlement analysis was performed assuming fill heights acquired by comparing the existing topographic profiles to the proposed fill grades provided by Perteet. • Conventional fill material was assumed for this analysis (unit weight of 140 pcf). Distances from railway tracks to placement of traditional fill at the base (30 feet) and the top (37 feet) of the fill. Settlements observed along the railway tracks. Settlements observed along roadway alignment. DRAWN BY CHECK BY DATE: FIGURE # PROJECT # SKS 8HWA GEOSCIENCES INC. S:\2017 PROJECTS\2017-147-21 PARK AVE N EXTENSION\CAD\HWA 2017-147-21 (FIG 6).DWG <Fig 3> Plotted: 2/19/2019 2:40 PM LATERAL EARTH PRESSURES FOR INTERNALLY BRACED TEMPORARY SHORING ZN 01.24.2019 2017-147-21 NOTES: 1.Ground water outside shoring assumed to be at elevation = 5 feet. 2.Design pressures are in units of psf; distances units of feet. 3.Surcharge load should be adjusted based on the anticipated traffic surcharge. Additional surcharge loads including construction equipment should be included, where appropriate. 4.Embedment (D) should be determined by summation of moments below base of the excavation and to cut off underground seepage to provide a stable bottom. 5.The upper two feet beneath the excavation subgrade should be ignored for the purpose of passive pressure resistance (DF). 6.A factor of safety has not been applied to the recommended passive earth pressure values. PARK AVENUE NORTH EXTENSION RENTON, WASHINGTON INTERNALLY BRACED SHEET PILE WALL 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3Ground Water Level Below Ground Surface (ft)Date and Time BH-4 Pump Test BH-4 WATER LEVEL DATA 2017-147-21 FIGURE NO. PROJECT NO. North Park Avenue Extension Renton, Washington Start pumping (11:08 AM) 9 Stopped pumping (11:38 AM) 8.4 8.5 8.6 8.7 8.8 8.9 9 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 10 10.1 10.2Ground Water Level Below Ground Surface (ft)Date and Time BH-5 Pump Test BH-5 WATER LEVEL DATA 2017-147-21 FIGURE NO. PROJECT NO. North Park Avenue Extension Renton, Washington Start pumping (1:06 PM) 10 Stopped pumping (1:46 PM) APPENDIX A HWA EXPLORATION LOGS HWA EXPLORATIONS HWA GeoSciences Inc. (HWA) conducted five (5) geotechnical borings in support of the design of the proposed Park Avenue North Extension Project in Renton, Washington. The five (5) borings were conducted on The Boeing Company and Puget Sound Energy properties. Three of these borings (BH-1 through BH-3) were advanced by Geologic Drill Partners, Inc. of Bellevue, Washington on December 20, 2018. BH-4 and BH-5 were advanced by Holocene Drilling, Inc. of Puyallup, Washington on December 21, 2018 and January 4, 2019. Geologic Drill Partners, Inc. used a limited access Mini Bobcat Drill Rig equipped for hollow stem auger drilling and a cathead hammer to advance the three borings. Holocene Drilling, Inc. used a Diedrich D-120 truck-mounted drill rig equipped for hollow stem auger and mud rotary drilling with an automatic hammer to advance the two borings. Standard Penetration Test (SPT) sampling was performed using a 2-inch outside diameter split- spoon sampler driven by a 140-pound manual rope and cathead hammer. During the SPT, samples were obtained by driving the sampler 18 inches into the soil with the hammer free-falling 30 inches. The numbers of blows required for each 6 inches of penetration were recorded. The Standard Penetration Resistance (“N-value”) of the soil is calculated as the number of blows required for the final 12 inches of penetration. This resistance, or N-value, provides an indication of relative density of granular soils and the relative consistency of cohesive soils; both indicators of soil strength and foundation bearing capacity. The locations of the boreholes were determined approximately in the field by pacing and taping distances from existing site features and are shown on the Site and Exploration Plan, Figure 2. A geotechnical engineer from HWA logged each exploration and recorded all pertinent information. Soil samples obtained from the boreholes were classified in the field and representative portions were sealed in plastic bags. These soil samples were then returned to our Bothell, Washington, laboratory for further examination and testing. Pertinent information including soil sample depths, stratigraphy, soil engineering characteristics, and ground water occurrence was recorded. The stratigraphic contacts shown on the individual exploration logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and ground water conditions depicted are only for the specific date and locations reported and, therefore, are not necessarily representative of other locations and times. A legend of the terms and symbols used on the exploration logs is presented in Figure A-1. Summary logs of the borehole explorations are presented in Figures A-2 through A-6. A-12017-147-21 PARK AVENUE N EXTENSION RENTON, WASHINGTON SYMBOLS USED ON EXPLORATION LOGS LEGEND OF TERMS AND Clean Gravel (little or no fines) More than 50% of Coarse Fraction Retained on No. 4 Sieve Gravel with SM SC ML MH CH OH RELATIVE DENSITY OR CONSISTENCY VERSUS SPT N-VALUE Very Loose Loose Medium Dense Very Dense Dense N (blows/ft) 0 to 4 4 to 10 10 to 30 30 to 50 over 50 Approximate Relative Density(%) 0 -15 15 -35 35 -65 65 -85 85 -100 COHESIVE SOILS Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard N (blows/ft) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 over 30 Approximate Undrained Shear Strength (psf) <250 250 - No. 4 Sieve Sand with Fines (appreciable amount of fines) amount of fines) More than 50% Retained on No. 200 Sieve Size Sand and Sandy Soils Clean Sand (little or no fines) 50% or More of Coarse Fraction Passing Fine Grained Soils Silt and Clay Liquid Limit Less than 50% 50% or More Passing No. 200 Sieve Size Silt and Clay Liquid Limit 50% or More 500 500 -1000 1000 -2000 2000 -4000 >4000 DensityDensity USCS SOIL CLASSIFICATION SYSTEM Coarse Grained Soils Gravel and Gravelly Soils Highly Organic Soils GROUP DESCRIPTIONS Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT/Organic CLAY Elastic SILT Fat CLAY Organic SILT/Organic CLAY PEAT MAJOR DIVISIONS GW SP CL OL PT GP GM GC SW COHESIONLESS SOILS Fines (appreciable LEGEND 2017-147-21.GPJ 2/22/19 PROJECT NO.:FIGURE: Coarse sand Medium sand SIZE RANGE Larger than 12 in Smaller than No. 200 (0.074mm) Gravel time of drilling) Groundwater Level (measured in well or AL CBR CN Atterberg Limits: LL = Liquid Limit California Bearing Ratio Consolidation Resilient Modulus Photoionization Device Reading Pocket Penetrometer Specific Gravity Triaxial Compression Torvane 3 in to 12 in 3 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 200 (0.074 mm) COMPONENT DRY Absence of moisture, dusty, dry to the touch. MOIST Damp but no visible water. WET Visible free water, usually soil is below water table. Boulders Cobbles Coarse gravel Fine gravel Sand MOISTURE CONTENT COMPONENT PROPORTIONS Fine sand Silt and Clay 5 - 12% PROPORTION RANGE DESCRIPTIVE TERMS Clean Slightly (Clayey, Silty, Sandy) 30 - 50% Components are arranged in order of increasing quantities. Very (Clayey, Silty, Sandy, Gravelly) 12 - 30%Clayey, Silty, Sandy, Gravelly open hole after water level stabilized) Groundwater Level (measured at 3 in to 3/4 in 3/4 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 10 (2.0 mm) No. 10 (2.0 mm) to No. 40 (0.42 mm) No. 40 (0.42 mm) to No. 200 (0.074 mm) PL = Plastic Limit DD DS GS K MD MR PID PP SG TC TV Dry Density (pcf) Direct Shear Grain Size Distribution Permeability Approx. Shear Strength (tsf) Percent Fines%F Moisture/Density Relationship (Proctor) Approx. Compressive Strength (tsf) Unconfined CompressionUC (140 lb. hammer with 30 in. drop) Shelby Tube Small Bag Sample Large Bag (Bulk) Sample Core Run Non-standard Penetration Test 2.0" OD Split Spoon (SPT) NOTES: Soil classifications presented on exploration logs are based on visual and laboratory observation. Density/consistency, color, modifier (if any) GROUP NAME, additions to group name (if any), moisture content. Proportion, gradation, and angularity of constituents, additional comments. (GEOLOGIC INTERPRETATION) Please refer to the discussion in the report text as well as the exploration logs for a more complete description of subsurface conditions. Soil descriptions are presented in the following general order: < 5% 3-1/4" OD Split Spoon with Brass Rings (3.0" OD split spoon) TEST SYMBOLS SAMPLE TYPE SYMBOLS GROUNDWATER SYMBOLS COMPONENT DEFINITIONS GS GS AL GS AL GS GS GS GS S-1 S-2 S-3 S-4 S-5 NR S-6a S-6b S-7 S-8 S-9 Dark olive-brown, silty SAND, moist. Rootlets. (TOPSOIL) Medium dense, rust-mottled, olive-gray, gravelly, silty SAND, moist. (FILL) Becomes dark gray. Very soft, dark grayish-brown, sandy SILT, moist. 2 inch layer of decomposed wood at approximately 8.5 feet. (ALLUVIUM) Driller added bentonite slurry to boring. Becomes olive-brown. Soft, dark olive-brown, slightly sandy SILT, moist. Low Plasticity. 2 inch layer of decomposed wood at 13 feet. No recovery. Very stiff, brown, organic SILT, wet. High plasticity. Medium dense, dark gray, very silty SAND, wet. Minor organics. Becomes slightly silty. 1 inch layer of decomposed wood at 21 feet. Medium stiff, dark gray, very sandy SILT, wet. Non-plastic. Medium dense, olive-brown, slightly silty SAND, wet. Driller reports 2 feet of heave. Borehole terminated 31.5 feet below ground surface (bgs). Ground water seepage encountered at approximately 12 feet bgs during drilling. Borehole abandoned with 3/8 inch bentonite chips. 4-7-9 6-5-13 1-1-1 1-1-0 2-2-1 1-1-2 3-9-10 9-13-15 2-2-2 6-12-15 SM SM ML ML OH SM ML SW SM BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)0 5 10 15 20 25 30 35 25 20 15 10 5 0 -5ELEVATION (feet)BH-1 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-2 Standard Penetration Test DATE COMPLETED: 12/20/2018 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 12/20/2018 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma >>>>165 SURFACE ELEVATION: 28.0 feet GS AL GS GS GS AL GS S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10 Dark olive-brown, silty SAND, moist. Rootlets. (TOPSOIL) Loose, rust-mottled, olive-gray, gravelly, silty SAND, moist. (FILL) Medium dense, rust-mottled, olive-gray, gravelly, silty SAND, wet. Soft, olive-gray, SILT, moist. Minor organics. Low plasticity. (ALLUVIUM) Becomes dark grayish-brown. Abundant organics. Soft, olive-brown, sandy SILT, moist. Abundant organics. Low plasticity. Becomes dark grayish-brown. Increasing sand content. Added bentonite slurry to boring. Stiff, olive-gray, very sandy SILT, moist. Decomposed wood fragment at 18.5 feet. Medium dense, dark gray, silty SAND, wet. Medium stiff, dark gray, SILT, wet. Minor organics. Low plasticity. Medium dense, dark gray, slightly silty SAND, wet. Borehole terminated 31.5 feet below ground surface (bgs). Ground water seepage encountered at approximately 5 feet bgs during drilling. Borehole abandoned with 3/8 inch bentonite chips. 3-2-3 8-8-8 2-1-2 1-1-1 2-2-2 1-2-1 1-3-8 7-8-7 2-3-4 1-2-6 SM ML ML SM ML SP SM BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)0 5 10 15 20 25 30 35 25 20 15 10 5 0 -5ELEVATION (feet)BH-2 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-3 Standard Penetration Test DATE COMPLETED: 12/20/2018 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 12/20/2018 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma SURFACE ELEVATION: 28.0 feet GS GS HYD GS GS GS HYD GS GS GS GS GS HYD S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10 S-11a S-11b Medium dense, dark yellowish-brown, gravelly, slightly silty SAND, moist. (FILL) Medium dense, rust-mottled, olive-gray, gravelly, silty SAND, moist. Becomes gray, wet. Very loose, dark olive-brown, gravelly, silty SAND, moist. Abundant organics. (ALLUVIUM) Becomes wet. Minor organics. Loose, dark gray, SAND, wet. Added bentonite slurry to boring. Loose, dark gray-brown, silty SAND, wet. Minor organics. With a 4 inch silt lens at 16 feet. Loose, dark gray-brown, very gravelly SAND, wet. Becomes dark olive-brown. Loose, rust-mottled, olive-gray, gravelly, very silty SAND, wet. Medium stiff, dark gray-brown, very sandy SILT, wet. Loose, dark gray, silty SAND, wet. Borehole terminated 31.5 feet below ground surface (bgs). Ground water seepage encountered at approximately 5 feet bgs during drilling. Borehole abandoned with 3/8 inch bentonite chips. 28-12-15 10-13-13 7-7-11 1-1-2 1-1-1 3-2-2 1-1-6 3-3-5 1-3-5 4-4-2 2-3-4 SP SM SM SM SP SM SP SM ML SM BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)0 5 10 15 20 25 30 35 25 20 15 10 5 0 -5ELEVATION (feet)BH-3 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-4 Standard Penetration Test DATE COMPLETED: 12/20/2018 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Mini Bobcat Drill Rig, 2.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 12/20/2018 SAMPLING METHOD: SPT w/ Cathead LOGGED BY: Z. Ngoma 122 SURFACE ELEVATION: 28.0 feet AL GS GS GS GS HYD GS GS GS S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10 Soft, rust-mottled olive-gray, very sandy SILT, moist. Low plasticity. (ALLUVIUM) Becomes dark yellow-brown. Non-plastic. Very loose, rust-mottled, yellow-brown, very silty SAND, wet. Grades to dark gray. Becomes loose, dark gray. Becomes slightly gravelly. Becomes medium dense. Very loose, dark gray, slightly gravelly, slightly silty SAND, wet. Piece of decomposed wood in tip of sampler. Driller reports encountering decomposed wood from 20 feet to 23 feet. Medium dense, dark gray, silty SAND, wet. Driller reports drilling action at 27 feet. Medium dense dark gray, very gravelly, slightly silty SAND, wet. Driller reports drilling action ends at 32 feet. 1-1-2 1-2-2 1-1-1 2-3-5 2-3-4 2-2-2 7-6-5 1-1-1 6-4-4 12-9-9 ML SM SP SM SM SP SM SM BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)0 5 10 15 20 25 30 35 25 20 15 10 5 0 -5ELEVATION (feet)BH-4 PAGE: 1 of 2(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-5 Standard Penetration Test DATE COMPLETED: 1/4/2019 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Diedrich D-120 Truck Rig, 4.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 1/4/2019 SAMPLING METHOD: SPT w/ Autohammer LOGGED BY: Z. Ngoma SURFACE ELEVATION: 27.0 feet GS HYD AL GS GS HYD GS HYD GS S-11 S-12 S-13 S-14 S-15 S-15 Medium dense, dark gray, silty SAND, wet. Very soft, olive-brown, organic SILT, moist. High plasticity. Drove Shelby Tube at 50 feet and it was advanced 13 inches. Medium Dense, gray, silty SAND, moist. Driller reports gravelly drilling action at 51 feet. Becomes dark gray. Minor organics. Very stiff, dark olive-brown, sandy organic SILT, moist. High plasticity. Borehole terminated 61.5 feet below ground surface (bgs). Ground water seepage encountered at approximately 5 feet bgs during drilling. Borehole completed as a 2-inch PVC well (DOE # BKC 472). 8-10-12 0-0-0 1-1-1 13-11-13 11-10-14 OH SM OH BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)35 40 45 50 55 60 65 70 -10 -15 -20 -25 -30 -35 -40ELEVATION(feet)BH-4 PAGE: 2 of 2(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-5 Standard Penetration Test DATE COMPLETED: 1/4/2019 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Diedrich D-120 Truck Rig, 4.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 1/4/2019 SAMPLING METHOD: SPT w/ Autohammer LOGGED BY: Z. Ngoma >>128 SURFACE ELEVATION: 27.0 feet GS GS GS GS HYD GS GS HYD GS S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10 S-11 Dense, olive-brown, gravelly, silty SAND, moist. (FILL) Becomes medium dense. Becomes dark gray-brown. Medium dense, olive-brown, silty SAND, moist. (ALLUVIUM) Becomes loose. Abundant organics. Stiff, dark gray, very sandy SILT, moist. Minor organics. Loose, dark gray, slightly gravelly, slightly silty SAND, wet. Medium dense, dark gray, SAND, wet. Becomes loose. Driller reports 8 inches of heave. Medium dense, dark gray, slightly silty SAND, wet. Driller reports 1 foot of heave. 8-14-22 10-11-12 7-8-9 4-5-5 2-3-5 3-3-6 1-1-5 7-9-10 5-5-7 2-2-6 7-7-8 SM SM ML SP SM SP SW SM SP BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)0 5 10 15 20 25 30 35 25 20 15 10 5 0 -5ELEVATION (feet)BH-5 PAGE: 1 of 2(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-6 Standard Penetration Test DATE COMPLETED: 12/21/2018 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Diedrich D-120 Truck Rig, 4.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 12/21/2018 SAMPLING METHOD: SPT w/ Autohammer LOGGED BY: Z. Ngoma SURFACE ELEVATION: 28.0 feet GS GS HYD GS GS HYD GS GS S-12 S-13 S-14 S-15 S-16 S-17 Medium dense, dark gray, slightly gravelly, slightly silty SAND, wet. Driller reports 6 inches of heave. Hard, dark gray, slightly gravelly, very sandy SILT, moist. Minor organics. Blow counts may be exaggerated possibly due to obstruction (e.g., piece of wood). Medium dense, olive-brown, very silty SAND, moist. Minor organics. Very stiff, dark brown, sandy SILT, moist. Minor organics. Medium dense, dark gray, silty SAND, wet. Becomes rust-mottled, dark gray, very sandy. Minor organics. Borehole terminated at 61.5 feet below ground surface (bgs). Ground water seepage encountered at approximately 8 feet bgs during drilling. Borehole completed as a 2-inch PVC well (DOE # BLI 700). Ground water level measured at 9 feet bgs on 12/27/18. 7-9-14 6-18-38 3-4-9 4-6-10 12-14-15 9-9-16 SM ML SM ML SM BORING-DSM 2017-147-21.GPJ 2/22/19 FIGURE:PROJECT NO.:2017-147-21 RENTON, WASHINGTON PARK AVENUE N EXTENSIONDEPTH(feet)35 40 45 50 55 60 65 70 -10 -15 -20 -25 -30 -35 -40ELEVATION(feet)BH-5 PAGE: 2 of 2(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL010203040 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBERNatural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION OTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot A-6 Standard Penetration Test DATE COMPLETED: 12/21/2018 DRILLING COMPANY: Geologic Drill Partners, Inc. DRILLING METHOD: Diedrich D-120 Truck Rig, 4.25" ID HSA LOCATION: See Figure 2 DATE STARTED: 12/21/2018 SAMPLING METHOD: SPT w/ Autohammer LOGGED BY: Z. Ngoma >> SURFACE ELEVATION: 28.0 feet APPENDIX B LABORATORY TEST RESULTS LABORATORY INVESTIGATION Representative soil samples obtained from the explorations were placed in plastic bags to prevent loss of moisture and transported to our Bothell, Washington, laboratory for further examination and testing. Laboratory tests were conducted on selected soil samples to characterize relevant engineering and index properties of the site soils. The laboratory testing program was performed in general accordance with appropriate ASTM Standards, as outlined below. MOISTURE CONTENT OF SOIL: The moisture content of selected soil samples (percent by dry mass) was determined in general accordance with ASTM D 2216. The results are shown at the sampled intervals on the appropriate summary logs in Appendix A. PARTICLE SIZE ANALYSIS OF SOILS: Selected granular samples were tested to determine the particle size distribution of material in accordance with ASTM D 422 (wash sieve or wash sieve and hydrometer methods). The results are summarized on the attached Particle-Size Distribution reports (Figures B-1 through B-16, Appendix B), which also provide information regarding the classification of the samples and the moisture content at the time of testing. LIQUID LIMIT, PLASTIC LIMIT, AND PLASTICITY INDEX OF SOILS (ATTERBERG LIMITS): Selected sample was tested using method ASTM D 4318, multi-point method. The results are reported on the attached Liquid Limit, Plastic Limit, and Plasticity Index reports found in Figure B-6. BH-1,S-1 2.5 4.0 11.2 SM Olive-brown, silty SAND with gravel BH-1,S-2 5.0 6.5 10.8 25.8 51.3 23.0 SM Dark gray, silty SAND with gravel BH-1,S-3 7.5 9.0 57.1 0.4 16.4 83.1 ML Dark grayish-brown, SILT with sand and organics BH-1,S-4 10.0 11.5 41.9 41 27 14 ML Olive-brown, SILT BH-1,S-5 12.5 14.0 60.5 0.1 9.0 90.9 ML Dark olive-brown, SILT with organics BH-1,S-6a 17.5 18.3 165.4 217 163 54 OH Brown, organic SILT BH-1,S-6b 18.3 19.0 28.6 0.1 63.5 36.4 SM Dark gray, silty SAND BH-1,S-7 20.0 21.5 29.4 0.8 87.2 12.1 SM Dark gray, silty SAND BH-1,S-8 25.0 26.5 33.7 41.8 58.2 ML Dark gray, sandy SILT BH-1,S-9 30.0 31.5 24.0 0.7 88.4 10.9 SW-SM Olive-brown, well-graded SAND with silt BH-2,S-1 2.5 4.0 12.1 23.7 51.8 24.5 SM Light olive-brown, silty SAND with gravel BH-2,S-2 5.0 6.5 10.9 SM Light olive-brown, silty SAND with gravel BH-2,S-3 7.5 9.0 40.2 34 26 8 ML Olive-gray, SILT BH-2,S-4 10.0 11.5 58.6 2.9 20.1 77.0 ML Dark grayish-brown, SILT with sand and organics BH-2,S-5 12.5 14.0 52.2 ML Olive-brown, sandy SILT BH-2,S-6 15.0 16.5 45.7 43.7 56.3 ML Dark grayish-brown, sandy SILT BH-2,S-7 17.5 19.0 75.4 ML Light olive-brown, sandy SILT BH-2,S-8 20.0 21.5 28.5 86.9 13.1 SM Dark gray, silty SAND BH-2,S-9 25.0 26.5 45.4 27 23 4 ML Dark gray, SILT BH-2,S-10 30.0 31.5 31.0 90.1 9.9 SP-SM Dark gray, poorly graded SAND with silt(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-1 PAGE: 1 of 4 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2017-147-21PROJECT NO.: INDEX MATSUM 2 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON BH-3,S-1 0.0 1.5 12.5 29.1 60.7 10.3 SP-SM Dark yellowish-brown, poorly graded SAND with silt and gravel BH-3,S-2 2.5 4.0 13.9 SM Light olive-brown, silty SAND BH-3,S-3 5.0 6.5 11.9 21.7 52.7 25.6 SM Gray, silty SAND with gravel BH-3,S-4 7.5 9.0 122.4 28.8 49.1 22.1 SM Dark olive-brown, silty SAND with gravel and organics BH-3,S-5 10.0 11.5 50.2 0.6 80.9 18.5 SM Dark olive-brown, silty SAND with organics BH-3,S-6 12.5 14.0 23.6 97.0 3.0 SP Dark gray, poorly graded SAND BH-3,S-7 15.0 16.5 39.0 0.6 70.8 28.6 SM Dark grayish-brown, silty SAND with organics BH-3,S-8 17.5 19.0 12.9 37.3 60.5 2.1 SP Dark grayish-brown, poorly graded SAND with gravel BH-3,S-9 20.0 21.5 21.9 SP Olive-brown, poorly graded SAND with gravel BH-3,S-10 25.0 26.5 40.9 16.1 42.1 41.7 SM Olive-brown, silty SAND with gravel BH-3,S-11a 30.0 30.5 34.8 43.7 56.3 ML Dark grayish-brown, sandy SILT BH-3,S-11b 30.5 31.5 28.5 0.7 80.0 19.3 SM Dark gray, silty SAND BH-4,S-1 2.5 4.0 45.0 38 29 9 ML Grayish-brown, SILT BH-4,S-2 5.0 6.5 42.3 1.6 39.0 59.4 ML Dark yellowish-brown, sandy SILT BH-4,S-3 7.5 9.0 41.9 62.8 37.2 SM Very dark grayish-brown, silty SAND BH-4,S-4 10.0 11.5 34.7 75.6 24.4 SM Dark gray, silty SAND BH-4,S-5 12.5 14.0 37.6 SM Dark grayish-brown, silty SAND BH-4,S-6 15.0 16.5 29.7 7.6 68.5 24.0 SM Dark gray, silty SAND BH-4,S-7 17.5 19.0 34.7 SM Very dark grayish-brown, silty SAND(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-2 PAGE: 2 of 4 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2017-147-21PROJECT NO.: INDEX MATSUM 2 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON BH-4,S-8 20.0 21.5 35.6 9.6 78.8 11.7 SP-SM Dark gray, poorly graded SAND with silt BH-4,S-9 25.0 26.5 30.0 1.1 72.7 26.2 SM Dark gray, silty SAND BH-4,S-10 30.0 31.5 14.6 41.9 52.2 6.0 SP-SM Dark gray, poorly graded SAND with silt and gravel BH-4,S-11 35.0 36.5 28.7 5.0 73.3 21.7 SM Dark gray, silty SAND BH-4,S-12 40.0 41.5 127.6 134 87 47 OH Olive-brown, organic SILT BH-4,S-13 45.0 46.5 77.6 11.4 88.6 OH Olive-brown, organic SILT BH-4,S-14 50.0 51.1 22.1 86.9 13.1 SM Gray, silty SAND BH-4,S-15 55.0 56.5 26.5 3.3 81.1 15.6 SM Dark gray, silty SAND BH-4,S-15 60.0 61.5 83.9 1.7 22.6 75.7 OH Very dark grayish-brown, organic SILT BH-5,S-1 0.0 1.5 11.1 17.6 64.1 18.3 SM Olive-brown, silty SAND with gravel BH-5,S-2 2.5 4.0 8.9 SM Olive-brown, silty SAND with gravel BH-5,S-3 5.0 6.5 12.4 14.6 59.3 26.0 SM Dark grayish-brown, silty SAND BH-5,S-4 7.5 9.0 21.7 SM Olive-brown, silty SAND BH-5,S-5 10.0 11.5 37.9 0.7 61.1 38.2 SM Olive-brown, silty SAND BH-5,S-6 12.5 14.0 42.9 0.1 33.4 66.5 ML Dark gray, sandy SILT BH-5,S-7 15.0 16.5 29.8 7.3 83.7 9.0 SP-SM Very dark grayish-brown, poorly graded SAND with silt BH-5,S-8 17.5 19.0 20.5 SP Very dark gray, poorly graded SAND with gravel BH-5,S-9 20.0 21.5 18.5 2.3 93.4 4.3 SP Dark gray, poorly graded SAND BH-5,S-10 25.0 26.5 20.6 SP Very dark gray, poorly graded SAND with gravel BH-5,S-11 30.0 31.5 19.8 3.0 87.0 10.0 SW-SM Very dark grayish-brown, well-graded SAND with silt(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-3 PAGE: 3 of 4 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2017-147-21PROJECT NO.: INDEX MATSUM 2 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON BH-5,S-12 35.0 36.5 18.9 7.2 85.7 7.1 SP-SM Dark grayish-brown, poorly graded SAND with silt BH-5,S-13 40.0 41.5 43.7 10.2 30.4 59.4 ML Very dark gray, sandy SILT BH-5,S-14 45.0 46.5 71.9 0.1 57.1 42.8 SM Olive-brown, silty SAND BH-5,S-15 50.0 51.5 47.9 0.1 16.9 83.0 ML Dark brown, SILT with sand BH-5,S-16 55.0 56.5 27.3 0.2 82.3 17.5 SM Dark grayish-brown, silty SAND BH-5,S-17 60.0 61.5 36.5 52.5 47.5 SM Dark grayish-brown, silty SAND(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-4 PAGE: 4 of 4 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2017-147-21PROJECT NO.: INDEX MATSUM 2 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-2 S-3 S-5 5.0 - 6.5 7.5 - 9.0 12.5 - 14.0 #10 51.3 16.4 9.0 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-5 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 25.8 0.4 0.1 Sand % (SM) Dark gray, silty SAND with gravel (ML) Dark grayish-brown, SILT with sand and organics (ML) Dark olive-brown, SILT with organics Fines % 0.00050.005 CLAY BH-1 BH-1 BH-1 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 11 57 61 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 23.0 83.1 90.9 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-6b S-7 S-8 18.3 - 19.0 20.0 - 21.5 25.0 - 26.5 #10 63.5 87.2 41.8 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-6 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.1 0.8 Sand % (SM) Dark gray, silty SAND (SM) Dark gray, silty SAND (ML) Dark gray, sandy SILT Fines % 0.00050.005 CLAY BH-1 BH-1 BH-1 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 29 29 34 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 36.4 12.1 58.2 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-9 S-1 S-4 30.0 - 31.5 2.5 - 4.0 10.0 - 11.5 #10 88.4 51.8 20.1 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-7 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.7 23.7 2.9 Sand % (SW-SM) Olive-brown, well-graded SAND with silt (SM) Light olive-brown, silty SAND with gravel (ML) Dark grayish-brown, SILT with sand and organics Fines % 0.00050.005 CLAY BH-1 BH-2 BH-2 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 24 12 59 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 10.9 24.5 77.0 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-6 S-8 S-10 15.0 - 16.5 20.0 - 21.5 30.0 - 31.5 #10 43.7 86.9 90.1 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-8 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 Sand % (ML) Dark grayish-brown, sandy SILT (SM) Dark gray, silty SAND (SP-SM) Dark gray, poorly graded SAND with silt Fines % 0.00050.005 CLAY BH-2 BH-2 BH-2 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 46 28 31 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 56.3 13.1 9.9 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-1 S-3 S-4 0.0 - 1.5 5.0 - 6.5 7.5 - 9.0 #10 60.7 52.7 49.1 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-9 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 29.1 21.7 28.8 Sand % (SP-SM) Dark yellowish-brown, poorly graded SAND with silt and gravel (SM) Gray, silty SAND with gravel (SM) Dark olive-brown, silty SAND with gravel and organics Fines % 0.00050.005 CLAY BH-3 BH-3 BH-3 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 12 12 122 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 10.3 25.6 22.1 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-5 S-6 S-7 10.0 - 11.5 12.5 - 14.0 15.0 - 16.5 #10 80.9 97.0 70.8 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-10 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.6 0.6 Sand % (SM) Dark olive-brown, silty SAND with organics (SP) Dark gray, poorly graded SAND (SM) Dark grayish-brown, silty SAND with organics Fines % 0.00050.005 CLAY BH-3 BH-3 BH-3 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 50 24 39 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 18.5 3.0 28.6 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-8 S-10 S-11a 17.5 - 19.0 25.0 - 26.5 30.0 - 30.5 #10 60.5 42.1 43.7 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-11 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 37.3 16.1 Sand % (SP) Dark grayish-brown, poorly graded SAND with gravel (SM) Olive-brown, silty SAND with gravel (ML) Dark grayish-brown, sandy SILT Fines % 0.00050.005 CLAY BH-3 BH-3 BH-3 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 13 41 35 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 2.1 41.7 56.3 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-11b S-2 S-3 30.5 - 31.5 5.0 - 6.5 7.5 - 9.0 #10 80.0 39.0 62.8 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-12 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.7 1.6 Sand % (SM) Dark gray, silty SAND (ML) Dark yellowish-brown, sandy SILT (SM) Very dark grayish-brown, silty SAND Fines % 0.00050.005 CLAY BH-3 BH-4 BH-4 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 29 42 42 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 19.3 59.4 37.2 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-4 S-6 S-8 10.0 - 11.5 15.0 - 16.5 20.0 - 21.5 #10 75.6 68.5 78.8 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-13 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 7.6 9.6 Sand % (SM) Dark gray, silty SAND (SM) Dark gray, silty SAND (SP-SM) Dark gray, poorly graded SAND with silt Fines % 0.00050.005 CLAY BH-4 BH-4 BH-4 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 35 30 36 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 24.4 24.0 11.7 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-9 S-10 S-11 25.0 - 26.5 30.0 - 31.5 35.0 - 36.5 #10 72.7 52.2 73.3 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-14 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 1.1 41.9 5.0 Sand % (SM) Dark gray, silty SAND (SP-SM) Dark gray, poorly graded SAND with silt and gravel (SM) Dark gray, silty SAND Fines % 0.00050.005 CLAY BH-4 BH-4 BH-4 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 30 15 29 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 26.2 6.0 21.7 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-13 S-14 S-15 45.0 - 46.5 50.0 - 51.1 55.0 - 56.5 #10 11.4 86.9 81.1 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-15 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 3.3 Sand % (OH) Olive-brown, organic SILT (SM) Gray, silty SAND (SM) Dark gray, silty SAND Fines % 0.00050.005 CLAY BH-4 BH-4 BH-4 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 78 22 27 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 88.6 13.1 15.6 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-15 S-1 S-3 60.0 - 61.5 0.0 - 1.5 5.0 - 6.5 #10 22.6 64.1 59.3 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-16 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 1.7 17.6 14.6 Sand % (OH) Very dark grayish-brown, organic SILT (SM) Olive-brown, silty SAND with gravel (SM) Dark grayish-brown, silty SAND Fines % 0.00050.005 CLAY BH-4 BH-5 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 84 11 12 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 75.7 18.3 26.0 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-5 S-6 S-7 10.0 - 11.5 12.5 - 14.0 15.0 - 16.5 #10 61.1 33.4 83.7 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-17 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.7 0.1 7.3 Sand % (SM) Olive-brown, silty SAND (ML) Dark gray, sandy SILT (SP-SM) Very dark grayish-brown, poorly graded SAND with silt Fines % 0.00050.005 CLAY BH-5 BH-5 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 38 43 30 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 38.2 66.5 9.0 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-9 S-11 S-12 20.0 - 21.5 30.0 - 31.5 35.0 - 36.5 #10 93.4 87.0 85.7 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-18 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 2.3 3.0 7.2 Sand % (SP) Dark gray, poorly graded SAND (SW-SM) Very dark grayish-brown, well-graded SAND with silt (SP-SM) Dark grayish-brown, poorly graded SAND with silt Fines % 0.00050.005 CLAY BH-5 BH-5 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 19 20 19 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 4.3 10.0 7.1 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-13 S-14 S-15 40.0 - 41.5 45.0 - 46.5 50.0 - 51.5 #10 30.4 57.1 16.9 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-19 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 10.2 0.1 0.1 Sand % (ML) Very dark gray, sandy SILT (SM) Olive-brown, silty SAND (ML) Dark brown, SILT with sand Fines % 0.00050.005 CLAY BH-5 BH-5 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 44 72 48 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 59.4 42.8 83.0 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-16 S-17 55.0 - 56.5 60.0 - 61.5 #10 82.3 52.5 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-20 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 0.2 Sand % (SM) Dark grayish-brown, silty SAND (SM) Dark grayish-brown, silty SAND Fines % 0.00050.005 CLAY BH-5 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 27 36 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 17.5 47.5 2017-147-21PROJECT NO.: HWAGRSZ 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 10 20 30 40 50 60 0 20 40 60 80 100 % MC LL CL-ML MH SAMPLEPLASTICITY INDEX (PI)SYMBOL PL PI S-4 S-3 S-9 S-1 10.0 - 11.5 7.5 - 9.0 25.0 - 26.5 2.5 - 4.0 27 26 23 29 42 40 45 45 LIQUID LIMIT, PLASTIC LIMIT AND PLASTICITY INDEX OF SOILS METHOD ASTM D4318 CL (ML) Olive-brown, SILT (ML) Olive-gray, SILT (ML) Dark gray, SILT (ML) Grayish-brown, SILT B-21 14 8 4 9 CH CLASSIFICATION % Fines LIQUID LIMIT (LL) BH-1 BH-2 BH-2 BH-4 ML 41 34 27 38 DEPTH (ft) 2017-147-21PROJECT NO.: HWAATTB 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON 0 50 100 150 200 250 0 40 80 120 160 200 240 280 320 360 DEPTH (ft) 17.5 - 18.3 40.0 - 41.5 (OH) Brown, organic SILT (OH) Olive-brown, organic SILT 163 87 BH-1 BH-4 S-6a S-12 CH MH B-22 LIQUID LIMIT (LL)PLASTICITY INDEX (PI)SYMBOL SAMPLE LIQUID LIMIT, PLASTIC LIMIT AND PLASTICITY INDEX OF SOILS METHOD ASTM D4318 CLASSIFICATION % MC LL PL PI % Fines 217 134 54 47 165 128 CL-ML ML CL 2017-147-21PROJECT NO.: HWAATTB7 2017-147-21.GPJ 01/28/19 FIGURE: PARK AVENUE N EXTENSION RENTON, WASHINGTON Appendix F Operations and Maintenance APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-9 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Trash and debris Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Damage to frame and/or top slab Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and structurally sound. Cracks in walls or bottom Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Structure Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipe Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-10 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Metal Grates (Catch Basins) Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Manhole Cover/Lid Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-11 NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Pipes Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Ditches Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards.