HomeMy WebLinkAboutTIR.pdfP.O. Box 412
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City of Renton, King County, Washington
Technical Information Report
And Downstream Analysis
For:
521 SW 5th Pl, Renton, WA
“5th Place West” Townhouse Project
Prepared Bosha Group
521 SW 5th Pl (APN 2143702200)
Renton, WA 98056
Mark X. Plog, P.E.
Revisions:
Date Description
5/14/2020 Initial Application
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Table of Contents
SECTION 1 – PROJECT OVERVIEW .......................................................................................................................... 3
SECTION 2 – CONDITIONS AND REQUIREMENTS SUMMARY ................................................................................ 15
SECTION 3 – OFF-SITE ANALYSIS .......................................................................................................................... 16
SECTION 4 – FLOW CONTROL BMPS, FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ... 20
SECTION 5 – CONVEYANCE SYSTEM ANALYSIS AND DESIGN ................................................................................ 23
SECTION 6 – SPECIAL REPORTS AND STUDIES ...................................................................................................... 23
SECTION 7 – OTHER PERMITS ............................................................................................................................... 23
SECTION 8 – ESC ANALYSIS AND DESIGN .............................................................................................................. 23
SECTION 9 – BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .............................. 24
SECTION 10 – OPERATIONS AND MAINTENANCE MANUAL .................................................................................. 25
Exhibits and Figures
TECHNICAL INFORMATION WORKSHEET ................................................................................................................ 4
FIGURE 1 - VICINITY MAP ..................................................................................................................................... 10
FIGURE 2 - DRAINAGE BASIN MAP ....................................................................................................................... 11
FIGURE 3 – SOILS MAP ......................................................................................................................................... 12
FIGURE 4 – EXISTING SITE CONDITIONS ............................................................................................................... 13
FIGURE 5 – DEVELOPED SITE CONDITIONS ........................................................................................................... 14
FIGURE 4 – SENSITIVE AREAS MAP ....................................................................................................................... 16
FIGURE 5 – DOWNSTREAM MAP .......................................................................................................................... 17
PHOTO MAP ...................................................................................................... ERROR! BOOKMARK NOT DEFINED.
MAP KEY ............................................................................................................ ERROR! BOOKMARK NOT DEFINED.
Attachments
1) Infiltration Feasibility Report
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Section 1 – Project Overview
The proposed project is located in the southwest quarter of the southwest quarter of Section 18, Township 23 North, Range
5 East, Willamette Meridian, King County, Washington in the City of Renton, King County parcel number 2143702200. The
site is zoned RMF. The surrounding parcels are also zoned RMF with apartments to the west, a single family residence to
the east, SW 5th Pl along the north side of the property and a Burlington Northern Railroad Right of Way to the South. The
site address is 521 SW 5th Pl, Renton, WA. The site is located in the Peak Rate Flow Control Standard (Existing Conditions),
and Basic Water Quality Control. Total area of the site is 0.395 acres not including the access easement. The total project
basin including work in the easement is 0.433 acres.
The site is occupied by a single family residence in the middle of the site. The remainder of the property is undeveloped and
is mostly covered with grass and a couple of trees. The existing improvements will be demolished and removed and the
proposed project will construct a multifamily project with parking and paved access. In general, the property is sloped and
drains to the south. The road the north intercepts and diverts upstream flows into the right of way.
The site is underlain by the Renton Formation according to the soils report, King County Soils Map and City of Renton Soils
Map. This site has approximately 6 inches of topsoil and vegetation underlain by approximately 3.5 to 5 feet of loose to
medium dense, silty-fine to medium grained sand (Highly Weathered Siltstone). These materials were underlain by dense
to very dense, silt with fine grained sand (Weathered Siltstone). According to the “Stormwater Infiltration Feasibility
Evaluation” by Cobalt Geosciences, the site is underlain by very fine-grained weathered bedrock. These soils have a very
low permeability which decreases with depth. It is likely that there will be shallow perched groundwater throughout the
property that further limits infiltration suitability.
The proposed development will be comprised of 2 structures. One is a 2-unit townhome and the other a 5-unit
townhome. No frontage improvements are anticipated. Access to the project is via a recorded access and utility easement.
The site is exempt from flow control and water quality requirements. To mitigate potential drainage problems, the
proposed development will collect and discharge stormwater in the natural drainage location to the south. The proposed
development will not create negative effects to the downstream drainage system.
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Technical Information Worksheet
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Figure 1 - Vicinity Map
PROJECT SITE
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Figure 2 - Drainage Basin Map
SITE CURRENTLY SHEET FLOWS TO THE
RAILROAD RIGHT OF WAY WHERE FLOWS
TRAVEL TO THE EAST AND APPEAR TO
INFILTRATE OR MAKE THEIR WAY TO THE
DRAINAGE INFRASTRUCTURE TO THE EAST
SITE
DRAINAGE
BASIN
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Figure 3 – Soils Map
PROJECT SITE
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Figure 4 – Existing Site Conditions
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Figure 5 – Developed Site Conditions
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Section 2 – Conditions and Requirements Summary
1. Discharge at the natural location: This site currently discharges via surface sheet flow into the adjacent railroad
right of way. All surface flows collected on this site will continue to be conveyed to the railroad right of way.
Discharge to the natural location will be maintained.
2. Off-site Analysis: A Level 1 off-site analysis was completed for this project and is included in Section 3 of this
report.
3. Flow control: The site is exempt under the historical flow control analysis of the increase of the 100-yr flow from
the existing condition (pre-1979) to the proposed developed condition. The analysis yielded a value of an
increase of only xxxxx cfs which is less than the 0.15cfs allowed using the 15-munite time step. Flow control will
not be required for this project.
4. Conveyance system: Conveyance will be provided by the proposed new tight line to be discharged to the railroad
right of way using a rock splash pad.
5. Erosion and sedimentation control: An erosion and sediment control plan has been provided with the submittal.
6. Maintenance and Operations: The storm water facilities for this project shall be maintained in accordance with
the requirements of Appendix A of the 2016 KCSWDM.
7. Financial guarantees and liability: Financial guarantees and liability will be provided as required by the City of
Renton.
8. Water Quality: This project is adding less than 5000 sf (4,435 sf) of new plus replaced PGIS and less than 3/4 of
an acre of new pervious surface and is therefore exempt from Core Requirement #8.
9. Flow Control BMPs: Per the soils report, this site is not suitable for infiltration BMP’s.
Special Requirements
1. Other adopted area-specific requirements: None
2. Floodplain/Floodway delineation: None
3. Flood protection facilities: None
4. Source controls: None
5. Oil Control: None
you must connect
this flow to a public
system, ie storm
system on sw 5th pl.
the only way you can
disperse
concentrated flows
onto a neighboring
property is via an
easement from the
owner of the
neighboring
property.
there are other bmps
that the geotech
report recommends.
please go through
core requirement #9,
Section 1.2.9.2 in the
renton surface water
design manual.
Replace with
actual value
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Section 3 – Off-site Analysis
This Level 1 Downstream Analysis is submitted as required by Core Requirement #2, Section 1.2.2, of the 2016 KCSWDM.
Core Requirement #2 requires a qualitative analysis of upstream and downstream drainage conditions with an initial
project submittal.
The property receives very minimal sheet flow from the adjacent property to the northwest. Flow from the property exists
onto NE 13th St as sheet flow – there are no drainage ditches or other conveyance mechanisms. The sheet flow exits the
property towards the south and travels along the railroad right of way until it reaches conveyance at the Hardie Ave SW
underpass.
Task 1: Study Area Definition and Maps:
See Section-1 Project Overview of this report for a detailed Study Area Definition.
Task 2: Resource Review:
The City of Renton Sensitive Area Maps do not show any sensitive areas or hazard areas on the site.
Figure 4 – Sensitive Areas Map
SITE
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Task 3: Field Inspection:
A field observation of the site, upstream drainage area, and ¼ mile downstream drainage path conditions was performed
on July 12, 2018.
Task 4: Drainage System Description and Problem Descriptions:
Upstream:
There is not any significant upstream drainage area contributing to the site. Any drainage that comes on site is minimal
sheet flow from the property to the north.
Downstream:
Figure 5 – Downstream Map
SITE CURRENTLY SHEET FLOWS TO THE
RAILROAD RIGHT OF WAY WHERE FLOWS
TRAVEL TO THE EAST AND APPEAR TO
INFILTRATE OR MAKE THEIR WAY TO THE
DRAINAGE INFRASTRUCTURE TO THE EAST
SITE
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Location
#
Description Photo
1 Sheet flow from
property to the
railroad right of way
2 It appears the
majority if not all of
the runoff infiltrates
along the railroad.
Any flow that is not
infiltrated would
find it’s way to the
underpass.
3 Flow that makes it to
the underpass enters
the conveyance
system here.
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Task 5 – Mitigation of Existing or Potential Problems:
The field analysis did not identify any erosion or capacity problems along the downstream drainage corridor within ¼ mile
of the site. None of the drainage complaints near the site were relevant to the downstream conveyance system.
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Section 4 – Flow Control BMPs, Flow Control and Water Quality Facility Analysis and Design
FLOW CONTROL BMP’s
Projects that are subject to Core Requirement #9 must apply flow control BMPs to either supplement the flow mitigation
provided by required flow control facilities or provide flow mitigation where flow control facilities are not required.
For non-subdivision projects making improvements on an individual site/lot, implementation of this requirement shall be
in accordance with the "Individual Lot BMP Requirements" in Section 1.2.9.2, which specify the selection of BMPs and the
extent of their application on the site/lot. This required implementation of flow control BMPs must occur as part of the
proposed project and provisions must be made for their future maintenance as specified in Section 1.2.9.2.
This site is less than 22,000 SF. The project must be evaluated under the Small Lot BMP Requirements of Section C.1.3.2.
Full Dispersion is not applicable as there is not any forest area available within a threshold discharge area to meet
the 15% ratio of fully dispersed impervious area to native vegetated surface.
Full infiltration of roof runoff is not applicable as the underlying soils are not suitable for infiltration per the soils
report.
Limited infiltration is not applicable and will be utilized as the underlying soils are suitable for limited infiltration
per the soils report.
FLOW CONTROL
This project is in the peak flow control area and is exempt from flow control. The site is also exempt under the historical
flow control analysis of the increase of the 100-yr flow from the existing condition (pre-1979) to the proposed developed
condition. The analysis yielded a value of an increase of only 0.072 cfs which is less than the 0.15cfs allowed using the
15-munite time step. Flow control will not be required for this project.
The following is the analysis used to establish the exemption:
Fix conflicting
sentence.
Consider and evaluate BMPs as
recommended in geotechnical report,
see comment of page 15 of TIR.
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PRE-DEVELOPED EXISTING CONDITION ANALYSIS
For the Pre-1979 condition refer to the existing condition exhibit
The resulting flow frequency analysis:
Flow Frequency
Flow(cfs) 0501 15m
2 Year = 0.0634
5 Year = 0.0923
10 Year = 0.1137
25 Year = 0.1434
50 Year = 0.1675
100 Year = 0.1933
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DEVELOPED CONDITION ANALYSIS
The resulting flow frequency analysis:
Flow Frequency
Flow(cfs) 0801 15m
2 Year = 0.1220
5 Year = 0.1574
10 Year = 0.1820
25 Year = 0.2142
50 Year = 0.2392
100 Year = 0.2650
The resulting net increase in the 100yr flow from the historical condition to the developed condition is 0.265 cfs – 0.193 cfs
= 0.072 cfs < 0.15 cfs. Therefore, this project is exempt from the requirements for flow control.
WATER QUALITY
This project is adding less than 5000 sf (4,435 sf) of new plus replaced PGIS and less than 3/4 of an acre of new pervious
surface and is therefore exempt from the requirement for water quality treatment.
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Section 5 – Conveyance System Analysis and Design
The conveyance for this project is minimal and conservatively oversized. No specific analysis was performed.
Section 6 – Special Reports and Studies
A soils report from Cobalt Geosciences has been provided as an attachment. Section 7 – Other Permits
None. Section 8 – ESC Analysis and Design
Site is under 1 acres and less than half the site is being disturbed. ESC calculations are unnecessary and TESC plans are
provided using typical small site BMP’s
The proposed TESC plan will implement the following BMP techniques:
• Construction sequence
• Cover practices
• Stabilized construction entrance
• Siltation barriers
• Clearing limits
• Stockpile covering
• Street sweeping
• Inlet protection
• Site stabilization
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Section 9 – Bond Quantities, Facility Summaries, and Declaration of Covenant
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200••Section I: Project Information•••Section II: Bond Quantities Worksheets••Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC))•Section II.b TRANSPORTATION (Street and Site Improvements)•Section II.c DRAINAGE (Drainage and Stormwater Facilities): •Section II.d WATER ‐ ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON•Section II.e SANITARY SEWER ‐ ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON••••••Section III. Bond Worksheet•This section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close‐out submittals to release the permit bond on a project. All unit prices include labor, equipment, materials, overhead and profit. Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right‐of‐Way (ROW), Future Public Improvements and Private Improvements.The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the project with the exception of the maintenance period reduction.Excel will auto‐calculate and auto‐populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need completing.Additional items not included in the lists can be added under the "write‐in" sections. Provide a complete description, cost estimate and unit of measure for each write‐in item. Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the form. Stormwater facilities (public and private) are required to be included in the bond amount.BOND QUANTITY WORKSHEET INSTRUCTIONSThis worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial submittal to project close‐out approval. Submit this workbook, in its entirety, as follows:The following forms are to be completed by the engineer/developer/applicant as applicable to the project: The Bond Worksheet form will auto‐calculate and auto‐populate from the information provided in Section I and Section II.This section includes all pertinent information for the projectSection II contains a separate spreadsheet TAB for each of the following specialties: (1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for civil construction permit submittal. Hard copies are to be included as part of the Technical Information Report (TIR).(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for final close‐out submittal.This section must be completed in its entiretyInformation from this section auto‐populates to all other relevant areas of the workbookPage 1 of 14Ref 8‐H Bond Quantity WorksheetINSTRUCTIONSUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No.Email Address:Project Name: Project Owner:CED Plan # (LUA): Phone:CED Permit # (U):Address: Site Address:Street Intersection: Addt'l Project Owner:Parcel #(s): Phone:Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NOWater Service Provided by:If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATIONCITY OF RENTONCITY OF RENTON1 Select the current project status/phase from the following options: For Approval ‐ Preliminary Data Enclosed, pending approval from the City; For Construction ‐ Estimated Data Enclosed, Plans have been approved for contruction by the City; Project Closeout ‐ Final Costs and Quantities Enclosed for Project Close‐out SubmittalEngineer Stamp Required (all cost estimates must have original wet stamp and signature)Clearing and Grading Utility ProvidersN/AProject Location and Description Project Owner Information5th Place WestSeattle, WA 981152143702200Lee Property Investments, LLC##‐###### (206) 816‐50422/10/2020Prepared by:FOR APPROVALProject Phase 1mark@plogengineering.comMark X. Plog31976Plog Engineering, PLLCP.O. Box 412, Ravensdale, WA 98051(206) 420‐7130521 5th Pl, Renton, WA1037 NE 65th St, Unit 335Stevens Ave SW########Abbreviated Legal Description:Lots 13 & 14, Block 16, EarlingtonPage 2 of 14Ref 8‐H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########UnitReference # Price Unit Quantity CostBackfill & compaction‐embankmentESC‐16.50$ CY Check dams, 4" minus rockESC‐2SWDM 5.4.6.380.00$ Each Catch Basin ProtectionESC‐335.50$ Each 5177.50Crushed surfacing 1 1/4" minusESC‐4WSDOT 9‐03.9(3)95.00$ CY DitchingESC‐59.00$ CY Excavation‐bulkESC‐62.00$ CY Fence, siltESC‐7SWDM 5.4.3.11.50$ LF 328492.00Fence, Temporary (NGPE)ESC‐81.50$ LF 224336.00Geotextile FabricESC‐92.50$ SY Hay Bale Silt TrapESC‐100.50$ Each HydroseedingESC‐11SWDM 5.4.2.40.80$ SY Interceptor Swale / DikeESC‐121.00$ LF Jute MeshESC‐13SWDM 5.4.2.23.50$ SY Level SpreaderESC‐141.75$ LF Mulch, by hand, straw, 3" deepESC‐15SWDM 5.4.2.12.50$ SY 7501,875.00Mulch, by machine, straw, 2" deepESC‐16SWDM 5.4.2.12.00$ SY Piping, temporary, CPP, 6"ESC‐1712.00$ LF Piping, temporary, CPP, 8"ESC‐1814.00$ LF Piping, temporary, CPP, 12"ESC‐1918.00$ LF Plastic covering, 6mm thick, sandbaggedESC‐20SWDM 5.4.2.34.00$ SY 50200.00Rip Rap, machine placed; slopesESC‐21WSDOT 9‐13.1(2)45.00$ CY Rock Construction Entrance, 50'x15'x1'ESC‐22SWDM 5.4.4.11,800.00$ Each 11,800.00Rock Construction Entrance, 100'x15'x1'ESC‐23SWDM 5.4.4.13,200.00$ Each Sediment pond riser assemblyESC‐24SWDM 5.4.5.22,200.00$ Each Sediment trap, 5' high berm ESC‐25SWDM 5.4.5.119.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC‐26SWDM 5.4.5.170.00$ LF Seeding, by handESC‐27SWDM 5.4.2.41.00$ SY Sodding, 1" deep, level groundESC‐28SWDM 5.4.2.58.00$ SY Sodding, 1" deep, sloped groundESC‐29SWDM 5.4.2.510.00$ SY TESC SupervisorESC‐30110.00$ HR 242,640.00Water truck, dust controlESC‐31SWDM 5.4.7140.00$ HR 182,520.00UnitReference # Price Unit Quantity Cost EROSION/SEDIMENT SUBTOTAL: 10,040.50SALES TAX @ 10% 1,004.05EROSION/SEDIMENT TOTAL: 11,044.55(A)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR EROSION & SEDIMENT CONTROLDescription No.(A)WRITE‐IN‐ITEMS Page 3 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.a EROSION_CONTROLUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostGENERAL ITEMS Backfill & Compaction‐ embankment GI‐16.00$ CYBackfill & Compaction‐ trench GI‐29.00$ CYClear/Remove Brush, by hand (SY) GI‐31.00$ SYBollards ‐ fixed GI‐4 240.74$ EachBollards ‐ removable GI‐5 452.34$ EachClearing/Grubbing/Tree Removal GI‐6 10,000.00$ Acre 0.3953,950.00Excavation ‐ bulk GI‐72.00$ CY 249498.00Excavation ‐ Trench GI‐85.00$ CYFencing, cedar, 6' high GI‐9 20.00$ LFFencing, chain link, 4' GI‐10 38.31$ LFFencing, chain link, vinyl coated, 6' high GI‐11 20.00$ LFFencing, chain link, gate, vinyl coated, 20' GI‐12 1,400.00$ EachFill & compact ‐ common barrow GI‐13 25.00$ CY 2957,375.00Fill & compact ‐ gravel base GI‐14 27.00$ CYFill & compact ‐ screened topsoil GI‐15 39.00$ CYGabion, 12" deep, stone filled mesh GI‐16 65.00$ SYGabion, 18" deep, stone filled mesh GI‐17 90.00$ SYGabion, 36" deep, stone filled mesh GI‐18 150.00$ SYGrading, fine, by hand GI‐19 2.50$ SYGrading, fine, with grader GI‐20 2.00$ SYMonuments, 3' Long GI‐21 250.00$ EachSensitive Areas Sign GI‐22 7.00$ EachSodding, 1" deep, sloped ground GI‐23 8.00$ SYSurveying, line & grade GI‐24 850.00$ Day 54,250.00Surveying, lot location/lines GI‐25 1,800.00$ Acre 0.395711.00Topsoil Type A (imported) GI‐26 28.50$ CYTraffic control crew ( 2 flaggers )GI‐27 120.00$ HR 242,880.00Trail, 4" chipped wood GI‐28 8.00$ SYTrail, 4" crushed cinder GI‐29 9.00$ SYTrail, 4" top course GI‐30 12.00$ SYConduit, 2" GI‐31 5.00$ LFWall, retaining, concrete GI‐32 55.00$ SFWall, rockery GI‐33 15.00$ SFSUBTOTAL THIS PAGE:19,664.00(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)Page 4 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000sy RI‐1 30.00$ SY 1805,400.00AC Grinding, 4' wide machine 1000‐2000sy RI‐2 16.00$ SYAC Grinding, 4' wide machine > 2000sy RI‐3 10.00$ SYAC Removal/Disposal RI‐4 35.00$ SY 602,100.00Barricade, Type III ( Permanent )RI‐5 56.00$ LFGuard Rail RI‐6 30.00$ LFCurb & Gutter, rolled RI‐7 17.00$ LFCurb & Gutter, vertical RI‐8 12.50$ LF 14175.00Curb and Gutter, demolition and disposal RI‐9 18.00$ LF 14252.00Curb, extruded asphalt RI‐10 5.50$ LFCurb, extruded concrete RI‐11 7.00$ LFSawcut, asphalt, 3" depth RI‐12 1.85$ LF 80148.00Sawcut, concrete, per 1" depth RI‐13 3.00$ LFSealant, asphalt RI‐14 2.00$ LF 80160.00Shoulder, gravel, 4" thick RI‐15 15.00$ SYSidewalk, 4" thick RI‐16 38.00$ SY 702,660.001565,928.00Sidewalk, 4" thick, demolition and disposal RI‐17 32.00$ SY 702,240.00Sidewalk, 5" thick RI‐18 41.00$ SY 1144,674.00Sidewalk, 5" thick, demolition and disposal RI‐19 40.00$ SYSign, Handicap RI‐20 85.00$ EachStriping, per stall RI‐21 7.00$ EachStriping, thermoplastic, ( for crosswalk )RI‐22 3.00$ SFStriping, 4" reflectorized line RI‐23 0.50$ LFAdditional 2.5" Crushed Surfacing RI‐24 3.60$ SYHMA 1/2" Overlay 1.5" RI‐25 14.00$ SY 1802,520.00HMA 1/2" Overlay 2" RI‐26 18.00$ SYHMA Road, 2", 4" rock, First 2500 SY RI‐27 28.00$ SY 49313,804.00HMA Road, 2", 4" rock, Qty. over 2500SY RI‐28 21.00$ SYHMA Road, 4", 6" rock, First 2500 SY RI‐29 45.00$ SYHMA Road, 4", 6" rock, Qty. over 2500 SY RI‐30 37.00$ SYHMA Road, 4", 4.5" ATB RI‐31 38.00$ SYGravel Road, 4" rock, First 2500 SY RI‐32 15.00$ SYGravel Road, 4" rock, Qty. over 2500 SY RI‐33 10.00$ SYThickened Edge RI‐34 8.60$ LF 50430.00SUBTOTAL THIS PAGE:15,655.00 24,836.00(B)(C)(D)(E)Page 5 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrow PL‐1 21.00$ SY2" AC, 1.5" top course & 2.5" base course PL‐2 28.00$ SY4" select borrow PL‐35.00$ SY1.5" top course rock & 2.5" base course PL‐4 14.00$ SYSUBTOTAL PARKING LOT SURFACING:(B)(C)(D)(E)LANDSCAPING & VEGETATION No.Street Trees LA‐1Median Landscaping LA‐2Right‐of‐Way Landscaping LA‐3Wetland Landscaping LA‐4SUBTOTAL LANDSCAPING & VEGETATION:(B)(C)(D)(E)TRAFFIC & LIGHTING No.Signs TR‐1Street Light System ( # of Poles) TR‐2Traffic Signal TR‐3Traffic Signal Modification TR‐4SUBTOTAL TRAFFIC & LIGHTING:(B)(C)(D)(E)WRITE‐IN‐ITEMSSUBTOTAL WRITE‐IN ITEMS:STREET AND SITE IMPROVEMENTS SUBTOTAL: 15,655.00 44,500.00SALES TAX @ 10% 1,565.50 4,450.00STREET AND SITE IMPROVEMENTS TOTAL: 17,220.50 48,950.00(B)(C)(D)(E)Page 6 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostDRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D‐1 26.00$ SY* (CBs include frame and lid)Beehive D‐2 90.00$ EachThrough‐curb Inlet Framework D‐3 400.00$ EachCB Type ID‐4 1,500.00$ Each 46,000.00CB Type IL D‐5 1,750.00$ EachCB Type II, 48" diameter D‐6 2,300.00$ Each for additional depth over 4' D‐7 480.00$ FTCB Type II, 54" diameter D‐8 2,500.00$ Each for additional depth over 4' D‐9 495.00$ FTCB Type II, 60" diameter D‐10 2,800.00$ Each for additional depth over 4' D‐11 600.00$ FTCB Type II, 72" diameter D‐12 6,000.00$ Each for additional depth over 4' D‐13 850.00$ FTCB Type II, 96" diameter D‐14 14,000.00$ Each for additional depth over 4' D‐15 925.00$ FTTrash Rack, 12" D‐16 350.00$ EachTrash Rack, 15" D‐17 410.00$ EachTrash Rack, 18" D‐18 480.00$ EachTrash Rack, 21" D‐19 550.00$ EachCleanout, PVC, 4" D‐20 150.00$ Each 162,400.00Cleanout, PVC, 6" D‐21 170.00$ EachCleanout, PVC, 8" D‐22 200.00$ EachCulvert, PVC, 4" D‐23 10.00$ LF 9049,040.00Culvert, PVC, 6" D‐24 13.00$ LFCulvert, PVC, 8" D‐25 15.00$ LFCulvert, PVC, 12" D‐26 23.00$ LFCulvert, PVC, 15" D‐27 35.00$ LFCulvert, PVC, 18" D‐28 41.00$ LFCulvert, PVC, 24" D‐29 56.00$ LFCulvert, PVC, 30" D‐30 78.00$ LFCulvert, PVC, 36" D‐31 130.00$ LFCulvert, CMP, 8" D‐32 19.00$ LFCulvert, CMP, 12" D‐33 29.00$ LFSUBTOTAL THIS PAGE:17,440.00(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B) (C)Page 7 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B) (C)DRAINAGE (Continued)Culvert, CMP, 15" D‐34 35.00$ LFCulvert, CMP, 18" D‐35 41.00$ LFCulvert, CMP, 24" D‐36 56.00$ LFCulvert, CMP, 30" D‐37 78.00$ LFCulvert, CMP, 36" D‐38 130.00$ LFCulvert, CMP, 48" D‐39 190.00$ LFCulvert, CMP, 60" D‐40 270.00$ LFCulvert, CMP, 72" D‐41 350.00$ LFCulvert, Concrete, 8" D‐42 42.00$ LFCulvert, Concrete, 12" D‐43 48.00$ LFCulvert, Concrete, 15" D‐44 78.00$ LFCulvert, Concrete, 18" D‐45 48.00$ LFCulvert, Concrete, 24" D‐46 78.00$ LFCulvert, Concrete, 30" D‐47 125.00$ LFCulvert, Concrete, 36" D‐48 150.00$ LFCulvert, Concrete, 42" D‐49 175.00$ LFCulvert, Concrete, 48" D‐50 205.00$ LFCulvert, CPE Triple Wall, 6" D‐51 14.00$ LFCulvert, CPE Triple Wall, 8" D‐52 16.00$ LFCulvert, CPE Triple Wall, 12" D‐53 24.00$ LFCulvert, CPE Triple Wall, 15" D‐54 35.00$ LFCulvert, CPE Triple Wall, 18" D‐55 41.00$ LFCulvert, CPE Triple Wall, 24" D‐56 56.00$ LFCulvert, CPE Triple Wall, 30" D‐57 78.00$ LFCulvert, CPE Triple Wall, 36" D‐58 130.00$ LFCulvert, LCPE, 6" D‐59 60.00$ LFCulvert, LCPE, 8" D‐60 72.00$ LFCulvert, LCPE, 12" D‐61 84.00$ LFCulvert, LCPE, 15" D‐62 96.00$ LFCulvert, LCPE, 18" D‐63 108.00$ LFCulvert, LCPE, 24" D‐64 120.00$ LFCulvert, LCPE, 30" D‐65 132.00$ LFCulvert, LCPE, 36" D‐66 144.00$ LFCulvert, LCPE, 48" D‐67 156.00$ LFCulvert, LCPE, 54" D‐68 168.00$ LFSUBTOTAL THIS PAGE:(B) (C) (D) (E)Page 8 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B) (C)DRAINAGE (Continued)Culvert, LCPE, 60" D‐69 180.00$ LFCulvert, LCPE, 72" D‐70 192.00$ LFCulvert, HDPE, 6" D‐71 42.00$ LFCulvert, HDPE, 8" D‐72 42.00$ LFCulvert, HDPE, 12" D‐73 74.00$ LFCulvert, HDPE, 15" D‐74 106.00$ LFCulvert, HDPE, 18" D‐75 138.00$ LFCulvert, HDPE, 24" D‐76 221.00$ LFCulvert, HDPE, 30" D‐77 276.00$ LFCulvert, HDPE, 36" D‐78 331.00$ LFCulvert, HDPE, 48" D‐79 386.00$ LFCulvert, HDPE, 54" D‐80 441.00$ LFCulvert, HDPE, 60" D‐81 496.00$ LFCulvert, HDPE, 72" D‐82 551.00$ LFPipe, Polypropylene, 6" D‐83 84.00$ LFPipe, Polypropylene, 8" D‐84 89.00$ LFPipe, Polypropylene, 12" D‐85 95.00$ LFPipe, Polypropylene, 15" D‐86 100.00$ LFPipe, Polypropylene, 18" D‐87 106.00$ LFPipe, Polypropylene, 24" D‐88 111.00$ LFPipe, Polypropylene, 30" D‐89 119.00$ LFPipe, Polypropylene, 36" D‐90 154.00$ LFPipe, Polypropylene, 48" D‐91 226.00$ LFPipe, Polypropylene, 54" D‐92 332.00$ LFPipe, Polypropylene, 60" D‐93 439.00$ LFPipe, Polypropylene, 72" D‐94 545.00$ LFCulvert, DI, 6" D‐95 61.00$ LFCulvert, DI, 8" D‐96 84.00$ LFCulvert, DI, 12" D‐97 106.00$ LFCulvert, DI, 15" D‐98 129.00$ LFCulvert, DI, 18" D‐99 152.00$ LFCulvert, DI, 24" D‐100 175.00$ LFCulvert, DI, 30" D‐101 198.00$ LFCulvert, DI, 36" D‐102 220.00$ LFCulvert, DI, 48" D‐103 243.00$ LFCulvert, DI, 54" D‐104 266.00$ LFCulvert, DI, 60" D‐105 289.00$ LFCulvert, DI, 72" D‐106 311.00$ LFSUBTOTAL THIS PAGE:(B) (C) (D) (E)Page 9 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B) (C)Specialty Drainage ItemsDitching SD‐19.50$ CYFlow Dispersal Trench (1,436 base+) SD‐3 28.00$ LF French Drain (3' depth) SD‐4 26.00$ LFGeotextile, laid in trench, polypropylene SD‐53.00$ SYMid‐tank Access Riser, 48" dia, 6' deep SD‐6 2,000.00$ EachPond Overflow Spillway SD‐7 16.00$ SYRestrictor/Oil Separator, 12" SD‐8 1,150.00$ EachRestrictor/Oil Separator, 15" SD‐9 1,350.00$ EachRestrictor/Oil Separator, 18" SD‐10 1,700.00$ EachRiprap, placed SD‐11 42.00$ CYTank End Reducer (36" diameter) SD‐12 1,200.00$ EachInfiltration pond testing SD‐13 125.00$ HRPermeable Pavement SD‐14Permeable Concrete Sidewalk SD‐15Culvert, Box __ ft x __ ft SD‐16SUBTOTAL SPECIALTY DRAINAGE ITEMS:(B) (C) (D) (E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention Pond SF‐1Each Detention Tank SF‐2Each Detention Vault SF‐3Each Infiltration Pond SF‐4Each Infiltration Tank SF‐5Each Infiltration Vault SF‐6Each Infiltration Trenches SF‐7Each Basic Biofiltration Swale SF‐8Each Wet Biofiltration Swale SF‐9Each Wetpond SF‐10 Each Wetvault SF‐11 Each Sand Filter SF‐12 Each Sand Filter Vault SF‐13 Each Linear Sand Filter SF‐14 Each Proprietary Facility SF‐15 Each Bioretention Facility SF‐16 Each SUBTOTAL STORMWATER FACILITIES:(B) (C) (D) (E)Page 10 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B) (C)WRITE‐IN‐ITEMS (INCLUDE ON‐SITE BMPs)Linear Trench Drain WI‐1 50.00$ LF 1005,000.00Rock Splash Pad WI‐2 100.00$ EA 1100.00Brick Pavers WI‐3 30.00$ SF 601,800.00WI‐4WI‐5WI‐6WI‐7WI‐8WI‐9WI‐10WI‐11WI‐12WI‐13WI‐14WI‐15SUBTOTAL WRITE‐IN ITEMS:6,900.00DRAINAGE AND STORMWATER FACILITIES SUBTOTAL: 24,340.00SALES TAX @ 10% 2,434.00DRAINAGE AND STORMWATER FACILITIES TOTAL: 26,774.00(B) (C) (D) (E)Page 11 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostConnection to Existing Watermain W‐1 2,000.00$ EachDuctile Iron Watermain, CL 52, 4 Inch Diameter W‐2 50.00$ LFDuctile Iron Watermain, CL 52, 6 Inch Diameter W‐3 56.00$ LFDuctile Iron Watermain, CL 52, 8 Inch Diameter W‐4 60.00$ LFDuctile Iron Watermain, CL 52, 10 Inch Diameter W‐5 70.00$ LFDuctile Iron Watermain, CL 52, 12 Inch Diameter W‐6 80.00$ LFGate Valve, 4 inch Diameter W‐7 500.00$ EachGate Valve, 6 inch Diameter W‐8 700.00$ EachGate Valve, 8 Inch Diameter W‐9 800.00$ EachGate Valve, 10 Inch Diameter W‐10 1,000.00$ EachGate Valve, 12 Inch Diameter W‐11 1,200.00$ EachFire Hydrant Assembly W‐12 4,000.00$ Each 14,000.00Permanent Blow‐Off Assembly W‐13 1,800.00$ EachAir‐Vac Assembly, 2‐Inch Diameter W‐14 2,000.00$ EachAir‐Vac Assembly, 1‐Inch Diameter W‐15 1,500.00$ EachCompound Meter Assembly 3‐inch Diameter W‐16 8,000.00$ EachCompound Meter Assembly 4‐inch Diameter W‐17 9,000.00$ EachCompound Meter Assembly 6‐inch Diameter W‐18 10,000.00$ EachPressure Reducing Valve Station 8‐inch to 10‐inch W‐19 20,000.00$ EachWATER SUBTOTAL:4,000.00SALES TAX @ 10% 400.00WATER TOTAL: 4,400.00(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B) (C)Page 12 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostClean Outs SS‐1 1,000.00$ Each 11,000.00Grease Interceptor, 500 gallon SS‐2 8,000.00$ EachGrease Interceptor, 1000 gallon SS‐3 10,000.00$ EachGrease Interceptor, 1500 gallon SS‐4 15,000.00$ EachSide Sewer Pipe, PVC. 4 Inch Diameter SS‐5 80.00$ LFSide Sewer Pipe, PVC. 6 Inch Diameter SS‐6 95.00$ LF 343,230.00Sewer Pipe, PVC, 8 inch Diameter SS‐7 105.00$ LFSewer Pipe, PVC, 12 Inch Diameter SS‐8 120.00$ LFSewer Pipe, DI, 8 inch Diameter SS‐9 115.00$ LFSewer Pipe, DI, 12 Inch Diameter SS‐10 130.00$ LFManhole, 48 Inch Diameter SS‐11 6,000.00$ EachManhole, 54 Inch Diameter SS‐13 6,500.00$ EachManhole, 60 Inch Diameter SS‐15 7,500.00$ EachManhole, 72 Inch Diameter SS‐17 8,500.00$ EachManhole, 96 Inch Diameter SS‐19 14,000.00$ EachPipe, C‐900, 12 Inch Diameter SS‐21 180.00$ LFOutside Drop SS‐24 1,500.00$ LSInside Drop SS‐25 1,000.00$ LSSewer Pipe, PVC, 1 1/4 Inch Diameter SS‐26 35.00$ LF 1174,095.00Lift Station (Entire System) SS‐27 10,000.00$ LS 110,000.00SANITARY SEWER SUBTOTAL:3,230.00 15,095.00SALES TAX @ 10% 323.00 1,509.50SANITARY SEWER TOTAL: 3,553.00 16,604.50(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction) (B) (C)Page 13 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (U):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a)Existing Right‐of‐Way Improvements Subtotal (b) (b)25,173.50$ Future Public Improvements Subtotal(c)‐$ Stormwater & Drainage Facilities (Public & Private) Subtotal(d) (d)26,774.00$ (e)(f)Site RestorationCivil Construction PermitMaintenance Bond10,389.50$ Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only ‐ May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. (206) 420‐7130mark@plogengineering.com5th Place West##‐######521 5th Pl, Renton, WA2143702200FOR APPROVAL########P.O. Box 412, Ravensdale, WA 9805175,578.80$ P (a) x 100%SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS2/10/2020Mark X. Plog31976Plog Engineering, PLLCR((b x 150%) + (d x 100%))S(e) x 150% + (f) x 100%Bond Reduction: Existing Right‐of‐Way Improvements (Quantity Remaining)2Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2T(P +R ‐ S)Prepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)EST1((b) + (c) + (d)) x 20%‐$ MAINTENANCE BOND */**(after final acceptance of construction)11,044.55$ 25,173.50$ 64,534.25$ 11,044.55$ ‐$ 26,774.00$ ‐$ Page 14 of 14Ref 8‐H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 5/17/2020
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Section 10 – Operations and Maintenance Manual
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Geotechnical Investigation
Proposed Townhomes
521 SW 5th Place
Renton, Washington
September 20, 2018
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
i
Table of Contents
1.0 INTRODUCTION ............................................................................................................. 1
2.0 PROJECT DESCRIPTION .............................................................................................. 1
3.0 SITE DESCRIPTION ....................................................................................................... 1
4.0 FIELD INVESTIGATION ............................................................................................... 1
4.1.1 Site Investigation Program ................................................................................... 1
5.0 SOIL AND GROUNDWATER CONDITIONS .............................................................. 2
5.1.1 Area Geology ........................................................................................................ 2
5.1.2 Groundwater ........................................................................................................ 2
6.0 GEOLOGIC HAZARDS ................................................................................................... 3
6.1 Erosion Hazard .................................................................................................... 3
6.2 Seismic Hazard .................................................................................................... 3
7.0 DISCUSSION ................................................................................................................... 4
7.1.1 General................................................................................................................. 4
8.0 RECOMMENDATIONS .................................................................................................. 4
8.1.1 Site Preparation ................................................................................................... 4
8.1.2 Temporary Excavations ........................................................................................ 4
8.1.3 Erosion and Sediment Control.............................................................................. 5
8.1.4 Foundation Design ............................................................................................... 6
8.1.5 Stormwater Management ..................................................................................... 7
8.1.6 Slab-on-Grade ...................................................................................................... 7
8.1.7 Groundwater Influence on Construction .............................................................. 8
8.1.8 Utilities ................................................................................................................ 8
9.0 CONSTRUCTION FIELD REVIEWS ............................................................................ 8
10.0 CLOSURE .................................................................................................................... 9
LIST OF APPENDICES
Appendix A — Statement of General Conditions
Appendix B — Figures
Appendix C — Test Pit Logs
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
September 20, 2018
1
PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
1.0 Introduction
In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has completed a geotechnical
investigation for the proposed 8-unit townhouse building located in Renton, Washington (Figure 1).
The purpose of the geotechnical investigation was to identify subsurface conditions and to provide
geotechnical recommendations for foundation design, stormwater management, earthwork, soil
compaction, and suitability of the on-site soils for use as fill.
The scope of work for the geotechnical evaluation consisted of a site investigation followed by engineering
analyses to prepare this report. Recommendations presented herein pertain to various geotechnical
aspects of the proposed development, including foundation support of the new building.
2.0 Project Description
The project includes construction of a new multi-story, 8-unit townhouse building. Anticipated building
loads are expected to be light and site grading will include cuts and fills on the order of 4 feet or less.
Stormwater management may include infiltration devices (if feasible), detention, rain gardens, and/or
detention systems. We should be provided with the final plans to verify that the recommendations in this
report are valid.
3.0 Site Description
The site is located at 521 SW 5th Place in Renton, Washington (Figure 1). The property consists of one
irregularly shaped parcel (No. 2143702200) with a total area of about 17,200 square feet.
The north-central portion of the property is developed with a single-family residence. A driveway
accesses the property from the north and SW 5th Place. The remainder of the property is undeveloped and
vegetated with grasses, blackberry vines, ivy, and sparse trees.
The property is nearly level to gently sloping downward from northwest to southeast at magnitudes less
than 10 percent and topographic relief of about 10 feet.
The site is bordered to the west and east and residential developments, to the north by right -of-way and
SW 5th Place, and to the south by railroad tracks and right-of-way.
4.0 Field Investigation
4.1.1 Site Investigation Program
The geotechnical field investigation program was completed on September 6, 2018 and included
excavating and sampling three test pits within the property for subsurface analysis.
The soils encountered were logged in the field and are described in accordance with the Unified Soil
Classification System (USCS).
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
September 20, 2018
2
PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
A Cobalt Geosciences field representative conducted the explorations, collected disturbed soil samples,
classified the encountered soils, kept a detailed log of the explorations, and observed and recorded
pertinent site features.
The results of the test pit explorations are presented on the test pit logs enclosed in Appendix C.
5.0 Soil and Groundwater Conditions
5.1.1 Area Geology
The site lies within the Puget Lowland. The lowland is part of a regional north-south trending trough that
extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washingto n,
this lowland is glacially carved, with a depositional and erosional history including at least four separate
glacial advances/retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to
the east by the Cascade Range. The lowland is filled with glacial and non-glacial sediments consisting of
interbedded gravel, sand, silt, till, and peat lenses.
The Geologic Map of Washington – Northwest Quadrant, indicates that the site is underlain by Renton
Formation.
Renton Formation includes Tertiary-aged siltstone, sandstone, coal, and shale which locally outcrops in
the Renton area. These materials are variably weathered but are typically dense to very hard within about
10 feet of the ground surface.
Explorations
The test pits encountered approximately 6 inches of topsoil and vegetation underlain by approximately
3.5 to 5 feet of loose to medium dense, silty -fine to medium grained sand (Highly Weathered Siltstone).
These materials were underlain by dense to very dense, silt with fine grained sand (Weathered Siltstone),
which continued to the termination depths of the test pits.
5.1.2 Groundwater
Groundwater was not encountered in any of the test pits. We anticipate that perched groundwater will be
present at the site between about 3 and 6 feet below existing grades during the winter and early spring
months.
Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors
that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability.
Water levels at the time of the field investigation may be different from those encountered during the
construction phase of the project.
GEOTECHNICAL INVESTIGATION
RENTON, WASHINGTON
September 20, 2018
3
PO Box 82243
Kenmore, WA 98028
cobaltgeo@gmail.com
206-331-1097
6.0 Geologic Hazards
6.1 Erosion Hazard
The Natural Resources Conservation Services (NRCS) maps for King County indicate that the site is
underlain by Beausite gravelly sandy loam (6 to 15 percent slopes). In general, these soils have a slight
erosion potential in a disturbed state.
It is our opinion that soil erosion potential at this project site can be reduced through landscaping and
surface water runoff control. Typically erosion of exposed soils will be most noticeable during periods of
rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt
fences, hay bales, mulching, control ditches and diversion trenches. Th e typical wet weather season, with
regard to site grading, is from October 31st to April 1st. Erosion control measures should be in place before
the onset of wet weather.
6.2 Seismic Hazard
The overall subsurface profile corresponds to a Site Class C as defined by Table 1613.5.2 of the 2015
International Building Code (2015 IBC). A Site Class C corresponds to very dense soil and soft rock within
the upper 100 feet.
We referenced the U.S. Geological Survey (USGS) Earthquake Hazards Program Website to o btain values
for SS, S1, Fa, and Fv. The USGS website includes the most updated published data on seismic conditions.
The site specific seismic design parameters and adjusted maximum spectral response acceleration
parameters are as follows:
PGA (Peak Ground Acceleration, in percent of g)
SS 144.60% of g
S1 54.10% of g
FA 1.00
FV 1.30
Additional seismic considerations include liquefaction potential and amplification of ground motions by
soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table.
The relatively dense soil and weathered rock deposits that underlie the site have a low liquefaction
potential.
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7.0 DISCUSSION
7.1.1 General
The site is underlain by highly to slightly weathered siltstone of the Renton Formation. Medium dense or
firmer native soils are suitable to support the proposed townhouse building . In general, suitable bearing
soils were observed between 3 and 4 feet below existing site elevations in our test pits.
Infiltration of stormwater runoff is not feasible at this site. The shallow soil conditions and high
likelihood of shallow seasonal groundwater limit suitability of infiltration devices. We recommend
utilizing shallow systems that provide some detention and water quality function, such as bioswales or
rain gardens with overflow to stormwater infrastructure.
8.0 Recommendations
8.1.1 Site Preparation
Trees, shrubs and other vegetation should be removed prior to stripping of surficial organic -rich soil and
fill. Based on observations from the site investigation program, it is anticipated that the stripping depth
will be 6 to 18 inches. Deeper excavations will be necessary below large trees , existing buildings, and in
any areas underlain by undocumented fill materials.
The native soils consist of silty-sand with gravel. These soils may be used as structural fill provided they
achieve compaction requirements and are within 3 percent of the optimum moisture. These soils are
typically only suitable for use as fill during the summer months, as they will be above the optimum
moisture levels in their current state. These soils are variably moisture sensitive and may degrade during
periods of wet weather and under equipment traffic.
Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches
and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be
placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of
the modified proctor maximum dry density, as determined by the ASTM D 1557 test method.
8.1.2 Temporary Excavations
Based on our understanding of the project, we anticipate that the grading could include local cuts on the
order of approximately 4 feet or less for foundation and utility placement. If there are any excavations
deeper than four feet, they should be sloped no steeper than 1H:1V (Horizontal:Vertical) in medium dense
native soils and 3/4H:1V in dense to very dense native soils or weathered rock. If an excavation is subject
to heavy vibration or surcharge loads, we recommend that the excavatio ns be sloped no steeper than
1.5H:1V, where room permits.
Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N,
Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified
person during construction activities and the inspections should be documented in daily reports. The
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contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope
erosion during construction.
Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the
slopes should be closely monitored until the permanent retaining systems or slope configurations are
complete. Materials should not be stored or equipment operated within 10 feet of the top of any
temporary cut slope.
Soil conditions may not be completely known from the geotechnical investigation. In the case of
temporary cuts, the existing soil conditions may not be completely revealed until the excavation work
exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes
will need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be
made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be
adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines
can be met.
If any variations or undesirable conditions are encountered during construction, we should be notified so
that supplemental recommendations can be made. If room constraints or groundwater conditions do not
permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring
systems may be required. The contractor should be responsible for developing temporary shoring
systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review
temporary shoring designs prior to installation, to verify the suitability of the proposed systems.
8.1.3 Erosion and Sediment Control
Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands,
streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures
should be implemented and these measures should be in general accordance with local regulations. At a
minimum, the following basic recommendations should be incorporated into the design of the erosion
and sediment control features for the site:
Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the
site soils, to take place during the dry season (generally May through September). However, provided
precautions are taken using Best Management Practices (BMP’s), grading activities can be completed
during the wet season (generally October through April).
All site work should be completed and stabilized as quickly as possible.
Additional perimeter erosion and sediment control features may be required to reduce the possibility
of sediment entering the surface water. This may include additional silt fences, silt fences with a
higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems.
Any runoff generated by dewatering discharge should be treated through construction of a sediment
trap if there is sufficient space. If space is limited other filtration methods will need to be
incorporated.
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8.1.4 Foundation Design
The proposed townhouse building may be supported on a shallow spread footing foundation system
bearing on undisturbed medium dense or firmer native soils or on properly compacted structural fill
placed on the suitable native soils. If structural fill is used to support foundations, then the zone of
structural fill should extend beyond the faces of the footing a lateral distance at least equal to the
thickness of the structural fill.
For shallow foundation support, we recommend widths of at least 18 and 24 inches, respectively, for
continuous wall and isolated column footings supporting the proposed structures. Provided that the
footings are supported as recommended above, a net allowable bearing pressure of 3,000 pounds per
square foot (psf) may be used for design.
A 1/3 increase in the above value may be used for shor t duration loads, such as those imposed by wind
and seismic events. Structural fill placed on bearing, native subgrade should be compacted to at least 95
percent of the maximum dry density based on ASTM Test Method D1557. Footing excavations should be
inspected to verify that the foundations will bear on suitable material.
Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent
exterior grade, whichever is lower. Interior footings should have a minimum depth of 12 inches below pad
subgrade (soil grade) or adjacent exterior grade, whichever is lower.
If constructed as recommended, the total foundation settlement is not expected to exceed 1 inch.
Differential settlement, along a 25-foot exterior wall footing, or between adjoining column footings,
should be less than ½ inch. This translates to an angular distortion of 0.002. Most settlement is
expected to occur during construction, as the loads are applied. However, additional post -construction
settlement may occur if the foundation soils are flooded or saturated. All footing excavations should be
observed by a qualified geotechnical consultant.
Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40
acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can
also be developed using an allowable equivalent fluid passive pressure of 275 pounds per cubic foot (pcf)
acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior
areas).
The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of
safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in
determining the total lateral resistance. A 1/3 increase in the above values may be used for short duration
transient loads.
Care should be taken to prevent wetting or drying of the bearing materials during construction. Any
extremely wet or dry materials, or any loose or disturbed materials at the bottom of the footing
excavations, should be removed prior to placing concrete. The potential for wetting or drying of the
bearing materials can be reduced by pouring concrete as soon as possible after completing the footing
excavation and evaluating the bearing surface by the geotechnical engineer or his representative.
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8.1.5 Stormwater Management
The site is underlain by very fine-grained weathered bedrock. These soils have a very low permeability
which decreases with depth. It is likely that there will be shallow perched groundwater throughout the
property that further limits infiltration suitability.
We performed an in-situ infiltration test in TP-1 at a depth of 4 feet below grade. Following testing and
application of correction factors, the infiltration rate was 0.22 inches per hour, which is lower than what
the Department of Ecology considers to be feasible. We do not recommend utilizing infiltration systems
at the site.
We recommend utilizing shallow dispersion trenches, bio-swales, rain gardens, permeable pavements or
other shallow systems to manage runoff from new impervious surfaces. We can provide additional
information upon request. We should be provided with the final plans for review.
8.1.6 Slab-on-Grade
We recommend that the upper 12 inches of the existing fill and/or native soils within slab areas be re-
compacted to at least 95 percent of the modified proctor (ASTM D1557 Test Method).
Often, a vapor barrier is considered below concrete slab areas. However, the usage of a vapor barrier could
result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the
usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of
the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers.
The American Concrete Institutes ACI 360R-06 Design of Slabs on Grade and ACI 302.1R-04 Guide for
Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor
slab detailing.
Slabs on grade may be designed using a coefficient of subgrade reaction of 180 pounds per cubic inch (pci)
assuming the slab-on-grade base course is underlain by structural fill placed and compacted as outlined in
Section 8.1.
A perimeter drainage system is recommended unless interior slab areas are elevated a minimum of 12
inches above adjacent exterior grades. If installed, a perimeter drainage system should consist of a 4 inch
diameter perforated drain pipe surrounded by a minimum 6 inches of drain rock wrapped in a non-woven
geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The perimeter
drainage system should discharge by gravity flow to a suitable stormwater system.
Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface
water flow away from the building and preferably with a relatively impermeable surface cover
immediately adjacent to the building.
8.1.7 Groundwater Influence on Construction
Groundwater was not encountered in any of the test pits. We anticipate that perched groundwater
develops during the wetter months between highly weathered and slightly weathered siltstone. Mottled
soils were observed in all of the explorations between 3 and 6 feet below existing grades. Seasonal
groundwater will likely be encountered at these depths during the late winter and early spring.
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During the winter-spring months, we anticipate that sump excavations and small diameter pumps
systems will adequately de-water short-term excavations, if required. Any system should be designed by
the contractor. We can provide additional recommendations upon request.
8.1.8 Utilities
Utility trenches should be excavated according to accepted engineering practices fo llowing OSHA
(Occupational Safety and Health Administration) standards, by a contractor experienced in such work.
The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench
walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided.
Depending upon the location and depth of some utility trenches, groundwater flow into open excavations
could be experienced, especially during or shortly following periods of precipitation.
In general, silty soils were encountered at shallow depths in the explorations at this site. These soils have
variable cohesion and density and will have a tendency to cave or slough in excavations. Shoring or
sloping back trench sidewalls is required within these soils in excavations greater than 4 feet deep.
All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench
backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of
the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill
placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based
on ASTM Test Method D1557. Below 5 feet, utility trench backfill in pavement areas should be compacted
to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. Pipe bedding
should be in accordance with the pipe manufacturer's recommendations.
The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the
backfill location and compaction requirements. Depending on the depth and location of the proposed
utilities, we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The
contractor should use appropriate equipment and methods to avoid damage to the utilities and/or
structures during fill placement and compaction procedures.
9.0 Construction Field Reviews
Cobalt Geosciences should be retained to provide part time field review during construction in order to
verify that the soil conditions encountered are consistent wit h our design assumptions and that the intent
of our recommendations is being met. This will require field and engineering review to:
Monitor and test structural fill placement and soil compaction
Observe bearing capacity at foundation locations
Observe slab-on-grade preparation
Observe excavation stability
Geotechnical design services should also be anticipated during the subsequent final design phase to
support the structural design and address specific issues arising during this phase. Field and engineeri ng
review services will also be required during the construction phase in order to provide a Final Letter for
the project.
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10.0 Closure
This report was prepared for the exclusive use of The Bosha Group and their appointed consultants. Any
use of this report or the material contained herein by third parties, or for other than the intended purpose,
should first be approved in writing by Cobalt Geosciences, LLC.
The recommendations contained in this report are based on assumed continuity of soils with those of our
test holes, and assumed structural loads. Cobalt Geosciences should be provided with final architectural
and civil drawings when they become available in order that we may review our design recommendations
and advise of any revisions, if necessary.
Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the
responsibility of The Bosha Group who is identified as “the Client” within the Statement of General
Conditions, and its agents to review the conditions and to notify Cobalt Geosciences should any of these
not be satisfied.
Respectfully submitted,
Cobalt Geosciences, LLC
Original signed by:
Exp. 6/26/20
Phil Haberman, PE, LG, LEG
Principal
PH/sc
APPENDIX A
Statement of General Conditions
Statement of General Conditions
USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and
may not be used by any third party without the express written consent of Cobalt Geosciences and the
Client. Any use which a third party makes of this report is the responsibility of such third party.
BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are
in accordance with Cobalt Geosciences present understanding of the site specific project as described by
the Client. The applicability of these is restricted to the site conditions encountered at the time of the
investigation or study. If the proposed site specific project differs or is modified from what is described in
this report or if the site conditions are altered, this r eport is no longer valid unless Cobalt Geosciences is
requested by the Client to review and revise the report to reflect the differing or modified project specifics
and/or the altered site conditions.
STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in
accordance with the normally accepted standard of care in the state of execution for the specific
professional service provided to the Client. No other warranty is made.
INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and
statements regarding their condition, made in this report are based on site conditions encountered by
Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations.
Classifications and statements of condition have been made in accordance with normally accepted
practices which are judgmental in nature; no specific description should be considered exact, but rather
reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to
some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock
and groundwater conditions as influenced by geological processes, construction activity, and site use.
VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be
encountered that are different from those described in this report or encountered at the test locations,
Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are
substantial and if reassessments of the report conclusions or recommendations are required. Cobalt
Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt
Geosciences that differing site or sub-surface conditions are present upon becoming aware of such
conditions.
PLANNING, DESIGN, OR CONSTRUCTION: Development or design plans and specifications
should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property
acquisition, tender, construction, etc), to confirm that this report completely addresses the elaborated
project specifics and that the contents of this report have been properly interpreted. Specialty quality
assurance services (field observations and testing) during construction are a necessary part of the
evaluation of sub-subsurface conditions and site preparation works. Site work relating to the
recommendations included in this report should only be carried out in the presence of a qualified
geotechnical engineer; Cobalt Geosciences cannot be responsible for site work carried out without being
present.
10.2
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APPENDIX B
Figures: Vicinity Map, Site Plan
SITE
N
Project
Location
Renton
WASHINGTON
Proposed Townhomes
521 SW 5th Place
Renton, Washington
VICINITY
MAP
FIGURE 1
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
N
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
SITE PLAN
FIGURE 2
TP-1
TP-1
TP-2
TP-3
Proposed Townhomes
521 SW 5th Place
Renton, Washington
APPENDIX C
Test Pit Logs
TEST PIT
LOGS
Proposed Townhomes
521 SW 5th Place
Renton, Washington
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
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Test Pit TP-1
0-0.5’ Vegetation/Topsoil
0.5-5’ Silty Sand to Sandy Silt (SM-ML)
Loose to medium dense, silty-fine to medium grained sand,
mottled yellowish brown to tan, dry to moist.
(Highly Weathered Siltstone)
5-8’ Silt with Sand (ML)
Dense to very dense, silty-fine to fine grained sand,
yellowish brown to grayish brown, moist. (Weathered Siltstone)
End of Test Pit 8’
No Groundwater
No Caving
SM
Topsoil/Vegetation
Highly Weathered Siltstone
0.5’
USCS Graphic
5’
SM Weathered Siltstone
Test Pit TP-2
0-0.5’ Vegetation/Topsoil
0.5-5.5’ Silty Sand to Sandy Silt (SM-ML)
Loose to medium dense, silty-fine to medium grained sand,
mottled yellowish brown to tan, dry to moist.
(Highly Weathered Siltstone)
5.5-8’ Silt with Sand (ML)
Dense to very dense, silty-fine to fine grained sand,
yellowish brown to grayish brown, moist. (Weathered Siltstone)
End of Test Pit 8’
No Groundwater
No Caving
SM
Topsoil/Vegetation
Highly Weathered Siltstone
0.5’
USCS Graphic
5.5’
SM Weathered Siltstone
Test Pit TP-3
0-0.5’ Vegetation/Topsoil
0.5-4’ Silty Sand to Sandy Silt (SM-ML)
Loose to medium dense, silty-fine to medium grained sand,
mottled yellowish brown to tan, dry to moist.
(Highly Weathered Siltstone)
4-6’ Silt with Sand (ML)
Dense to very dense, silty-fine to fine grained sand,
yellowish brown to grayish brown, moist. (Weathered Siltstone)
End of Test Pit 6’
No Groundwater
No Caving
SM
Topsoil/Vegetation
Highly Weathered Siltstone
0.5’
USCS Graphic
4’
SM Weathered Siltstone