appendix a - burlington, vermont
TRANSCRIPT
Appendix A:
Topographic Map of Project Area
VT Gas FacilitySite Location
Lake Champlain
ROSE ST
INTER
VALE
AVE
NORTH ST
PARK ST
N CHAMPLAIN ST
NORTH AVE
OAK ST
WALN
UT ST
WARD ST
WILLOW ST
STRONG ST
VOLZ ST
LAKEVIEW TER
BERRY ST
CANFIELD ST
MANHATTAN DRARCHIBALD ST
BLODGETT ST
CEDAR ST
CROMBIE ST
CROWLEY ST
POPLAR ST
MYRTLE ST
ELMWOOD AVE
LAFOUNTAIN ST
SAIN
T LOU
IS ST
SPRING ST
CONVENTSQ
DREW ST
ELMWOOD AV
PI TKI NST
SANITARY LANDFILL RD
VT ROUTE 127
New England Central Railroad Inc.
VCGI
Project Locus MapManhattan Drive and Convent Square Slope Improvements
Burlington, Vermont³0 400 800200 Feet
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Appendix B:
Natural Resources Map
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Observed Outfall Sediment Pile Extent
Vermont GasTransmission Main
Study AreaApprox. 6.2 acres44°29'10.239" N73°13'22.522" W
Surface Water Proection Area (SPA)WSID: VT0005053Burlington Dept. of Public Works, Water Division - Zone 3
NORTH AVE
SUNSET CT
MANHATTAN DR
WASHINGTON ST
VOLZ ST
BERRY ST
CONVENT SQ
VT ROUTE 127
AdE
AdA
AdD
AdB
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Fu
AdA
New En
gland
Centr
al Railr
oad I
nc.
Type = CState Rank = S4
State Listed = N/AFederal Rank =
2018-dp-2-2-wet
2018-2-1up2018-2-1wet
2018-dp-2-2-up
220
120
210
110
220
140
160150 170 18
0 190 20
0 210
110
120
110
130140150160
120
130
220
210
200 140
190
150
160
180
170
2018-TOB-1(Intermittent)
2018-SC-1(Intermittent)
2018-TOS-1(Intermittent)
2018-TOS-1(Intermittent)
2018-2(Proposed Class II)
2018-1(Proposed Class II)
VCGI
City of Burlington Manhattan Drive Stormwater Outfall Repairs Burlington, Vermont
Natural ResourcesSources:Background Imagery by VCGI (Collected in 2018)VCGI (Vermont Center for Geographic Information - Various Dates)ANR (Vermont Agency of Natural Resources - Various Dates)FWD (Vermont Department of Fish and Wildlife - 2018)VTrans (Vermont Agency of Transportation - 2017)VHB - 2018
i 0 120 24060 Feet
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Lake Champlain
Study Area
COLCHESTERBURLINGTON
NORTH ST
COLLEGE ST
MANHATTAN DR
NORTH AVE
N PROSPECT STLOOMIS ST
INTERVA
LE AV
E
ROUTE 127
SPRO
SPEC
TST
RIVERSIDE AVE
S WINOOSKI AVE
ARCHIBALD ST
LAKE ST
KING ST
N CHAMPLAIN ST
MAIN ST
SAINT PAUL STELMWOOD AVE
CHUR
CH ST
BUELL ST
MAPLE ST
CHERRY ST
PARK
ST
S UNION STN UNION ST
NWI
NOOS
K I AVE
INTERVALE RD
KILLARNEY DR
ROC K POINT RD
VT ROUTE 127
Winooski Rive r
300
200100
200
100
"!;Î Storm/Sewer Discharge Point"?B Catch Basin!!2 Manhole
Sewer LineStorm/Sewer Runoff
Study Area (VHB)! Delineation Data Point (VHB)
Delineated Stream Center (VHB)Delineated Top of Bank/Slope (VHB)Delineated Wetland (VHB)Proposed River Corridor - 50 Ft (VHB)
Class II Wetland Buffer - 50 Ft (VHB)Riparian Buffer - 50 Ft (VHB)NHI Element Occurrence (FWD)Deer Wintering Area (ANR)*FEMA 100 year Flood Zone (VCGI)River Corridor (ANR)*
Public Wells (ANR)*Private Wells (ANR)*
VSWIVSWI
VSWIVSWI
VSWI Wetland (ANR)GW Protection Area (ANR)*SW Protection Area (ANR)NRCS Soil Boundary (VCGI)
VHD Stream (VCGI)VHD Waterbody (VCGI)Parcel Boundary (VCGI)Railroad (VTrans)10 ft Contour (VCGI)2 ft Contour (VCGI)
Soil Abbreviation Soil Map Unit Vermont Farmland
Classification Erodibility Ranking Area (acres)
AdE Adams and Windsor loamy sands, 30 to 60 percent slopes NPSL Highly Erodible 2.52Fu Fill land NPSL Not Rated 0.02
Mp Muck and Peat NPSL Not Rated 3.66
NRCS Soils Information
OutfallIV8.0
OutfallIV10.0
OutfallIV9.0
Appendix C:
Resident Outreach Letter
Burlington Department of Public Works Water Resources Division
Stormwater Program (802) 863-4501
Dear Neighbor,
The Department of Public Works’ mission is to steward Burlington’s infrastructure and environment by
delivering efficient, effective and equitable public services. We are writing to let you know about a
project we are beginning this spring to improve long-term water quality, and help protect natural
resources and property.
Later this year, we will be hiring a contractor to complete repairs on three stormwater outfalls, as well as
stabilization work on the associated slope at the location shown in the attached map. This project is part
of the City’s larger effort to restore and protect our aging water infrastructure. You can find more
information on Burlington’s Clean Water Resiliency Plan and the various work we will be completing
under that effort by visiting: www.burlingtonvt.gov/DPW/CWRP
DETAILS: The project involves some limited vegetation clearing at the base of the slope, excavation and
grading to repair existing erosion, and the installation of a stone berm at the base of the slope to limit
downslope movement of the native soils. The project will also involve installation of ‘plunge pool’
structures at the existing stormwater outfalls to prevent any future erosion from those structures. Finally,
restoration work will be completed in the wetland and wetland buffers, to address sedimentation damage
and protect this resource area from future damage. While there may be some construction traffic along
Route 127 as part of this project, we do not anticipate any traffic disruptions to occur with this
work. We will provide additional notification once a schedule is established to ensure residents are
aware when work begins.
BACKGROUND: Due to the nature and location of this proposed project, the City will need to obtain
permits from the Vermont Department of Environmental Conservation, related to Wetlands, and
Construction-Phase Stormwater Management. If your property abuts the area where work is planned, you
will be receiving a notification as a requirement of those permitting processes.
ADDITIONAL INFORMATION:
To see the full extent of capital improvement work the City has planned for this year and over the
next several fiscal years, please visit our Capital Construction Portal at
www.burlingtonvt.gov/construction
If you have any questions about the proposed project, please contact Jenna Olson, Stormwater
Program Manager, at [email protected] or (802) 863-4501.
Sincerely,
Jenna Olson
Stormwater Program Manager
Appendix D:
Outfall Location Map
6/26/2019 BTV Collection System
burlingtonvt.maps.arcgis.com/home/webmap/print.html 1/1
Map data © OpenStreetMap contributors, CC-BY-SA
BTV Collection System
Burlington VT sewer and stormwater collection system mapping
BTV Collection System
Sewer/Stormwater Features
Discharge Point
Manhole
Access
Diversion
Overflow
Peak
Special_Structure
Weir
Inlet
Gravity Main
Abandoned
Combined WasteWater
Sewage
Storm Runoff
StormwaterCombined SewerSystem Relief
Unknown
Gravity Main (Abandoned)
Pressurized Main
300ft
Appendix E:
Preliminary Concept Designs –
Stantec Consulting
Appendix F:
Geotechnical Report –
S.W. Cole
R E P O R T 18-0764.1 S
January 4, 2019
Explorations and Geotechnical Engineering Services
BTV Outfalls IV8, IV9 & IV10 Manhattan Drive Burlington, Vermont
Prepared For:Vanasse Hangen Brustlin, Inc.Attention: Ms. Rachel Marvin, P.E.40 IDX Drive, Building 100South Burlington, Vermont 05403
Prepared By:S. W. Cole Engineering, Inc.55 Leroy Road, Suite 15Williston, Vermont 05495T: (802) 391-4542
TABLE OF CONTENTS
1.0 INTRODUCTION....................................................................................................... 1
1.1 Scope and Purpose ............................................................................................... 1
1.2 Site and Proposed Construction ............................................................................ 1
2.0 EXPLORATION AND TESTING................................................................................ 2
2.1 Explorations........................................................................................................... 2
2.2 Laboratory Testing................................................................................................. 3
3.0 SUBSURFACE CONDITIONS .................................................................................. 3
3.1 Soils....................................................................................................................... 3
3.2 Groundwater.......................................................................................................... 4
4.0 STABILITY EVALUATION AND RECOMMENDATIONS.......................................... 4
4.1 Stability Evaluation ................................................................................................ 4
4.2 Recommendations................................................................................................. 5
4.2.1 Remedial Measure 1 – Toe Berm................................................................ 6
4.2.2 Remedial Measure 2 – Sheet Piling ............................................................ 8
4.2.3 Remedial Measure 3 – Regrading ............................................................... 8
4.2.4 Remedial Measure 4 – Toe Berm with Surface Treatment.......................... 9
4.2.5 Summary ..................................................................................................... 9
4.3 Weather Considerations ...................................................................................... 11
4.4 Design Review and Construction Testing............................................................ 12
5.0 CLOSURE............................................................................................................... 12
Appendix A LimitationsAppendix B FiguresAppendix C Exploration Logs & KeyAppendix D Laboratory Test ResultsAppendix E Slope Stability Output
18-0764.1 S
January 4, 2019
Vanasse Hangen Brustlin, Inc.Attention: Ms. Rachel Marvin, P.E.40 IDX Drive, Building 100South Burlington, Vermont 05403
Subject: Explorations and Geotechnical Engineering Services BTV Outfalls IV8, IV9, & IV10 Manhattan Drive Burlington, Vermont
Dear Ms. Marvin:
In accordance with our Agreement, dated October 29, 2018, the following presents the results of our geotechnical evaluation for the above-referenced project. This report summarizes our findings and geotechnical recommendations and its contents are subject to the limitations set forth in Appendix A.
1.0 INTRODUCTION
1.1 Scope and PurposeThe purpose of our services was to obtain subsurface information at the site in order to develop geotechnical recommendations relative to stabilization of the existing slope along Manhattan Drive. Our scope of services included the advancement of test borings, a geotechnical analysis of the subsurface findings and preparation of this report.
1.2 Site and Proposed ConstructionThe slope of interest is located along Manhattan Drive and Convent Square in the Cityof Burlington, Vermont, beginning at the intersection of Manhattan Drive and Ward Street and extending north approximately one-quarter (1/4) of a mile to the Vermont Gas Company’s property on Convent Square. Immediately east of Manhattan Drive is
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the slope of interest, which is moderately to heavily wooded and descends to a large undeveloped area. As shown on the topographic survey provided to our office, portions of this area are mapped as being wetlands. An intermittent stream is present along the toe of slope and it is understood that portions of the City of Burlington stormwater system discharge into this area. Beyond the intersection of Manhattan Drive and Washington Street, residential structures are present along the crest of the slope.
The City of Burlington stormwater management system includes three (3) outfall locations along Manhattan Drive and Convent Square, progressing from the north to south, identified as Outfalls IV8, IV9, and IV10. Outfall IV8 is located immediately east of the Vermont Gas Company’s Convent Square substation, with Outfalls IV9 and IV10 located along the portion of slope adjacent to Manhattan Drive. As shown on the topographic survey provided to our office, elevations along the crest of the slope range from elevation 215 feet to 220 feet (project datum), while grades at the toe of slope range from elevations 120 feet to 140 feet. The existing slopes’ overall inclination vary from approximately 1.4:1 (Horizontal: Vertical) to 1.8:1 (H:V).
As we understand it, signs of local instability and surficial slope failure have been observed along the Manhattan Drive slope near Outfalls IV9 and IV10. In addition, it was observed in the Fall of 2018 that significant erosion had developed at Outfall IV8 when the existing corrugated metal stormwater pipe became disjointed, resulting in local oversteepening of the slope. It is understood that this erosion was addressed at that time through placement of crushed stone to infill the void and the City plans to install a cured-in-place (CIP) liner within Outfall IV8 to eliminate pipe joints.
2.0 EXPLORATION AND TESTING
2.1 ExplorationsThree (3) test borings were advanced at the site between December 7, 2018, and December 10, 2018, by S.W.COLE Explorations, a subsidiary of S. W. Cole Engineering, Inc. (S.W.COLE), using a Diedrich D-50 track-mounted drill rig. The approximate exploration locations, as established through conventional survey methods, are shown on the “Exploration Location Plan” included in Appendix B. An Exploration Log was prepared for each test boring to present the soil classifications and the records maintained in the
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field during advancement of the test borings. The logs and a key to the notes and symbols used on the Exploration Logs are presented in Appendix C.
Test borings SB-1 and SB-2 were advanced using 4-inch inside diameter flush-joint casing, while SB-3 was advanced using 2-¼-inch inside diameter hollow stem augers. As each of the test borings were advanced, the overburden was sampled and its penetration resistance determined in general accordance with the procedures of ASTM Designation D-1586, “Standard Method for Penetration Testing and Split-Barrel Sampling of Soils”. The sampling and penetration resistance testing was initiated at the ground surface and conducted at intervals of 5 feet or 10 feet until termination of the test borings.
A geotechnical engineer from our office observed the test borings, recorded the standard penetration resistances, field classified the samples, and placed representative portions of the same in jars. The samples were visually classified in our laboratory.
2.2 Laboratory TestingSoil samples obtained from the explorations were returned to our laboratory for further classification and basic geotechnical index property testing. Results of this testing are included in Appendix D.
3.0 SUBSURFACE CONDITIONS
3.1 Soils As indicated on the test boring logs, each of the test borings encountered a surficial course of topsoil, approximately 3 to 4 inches in thickness. At test boring SB-3, a thin sequence of miscellaneous fill was encountered underlying the topsoil. The fill was composed predominantly of sand and contained some to near equal amounts of silt. Occasional pieces of deleterious materials were also encountered throughout the deposit. Standard penetration resistances (N-values) within the fill indicate it is of a loose relative density. The fill was found to extend to approximately 1.5 feet below the existing ground surface.
Underlying the fill at SB-3 and the topsoil at test borings SB-1 and SB-2 was sand. The sand contained some to near equal amounts of gravel and trace to some amounts of silt. This sand deposit was fully penetrated at depths ranging from 33.5 feet to 56 feet below
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the existing ground surface. N-values within the sand indicate that it is of a loose to dense relative density.
Silt was encountered underlying the above described sand deposit and extends to depths ranging from 38.5 feet to 66 feet below the existing ground surface. Some to near equal amounts of sand were present within the silt and occasional to frequent partings of sand were also encountered. The silt was of a medium dense to dense relative density.
Each of the test borings was terminated within a second sand deposit at depths ranging from 77 feet to 92 feet below the crest of the slope. The sand contained some to near equal amounts of silt and occasional partings of coarser sand. This deposit was of a medium dense to very dense relative density as determined from standard penetration resistance testing.
3.2 GroundwaterGroundwater was not encountered during advancement of the test borings. Groundwater levels should be expected to fluctuate seasonally and in response to precipitation and snowmelt.
4.0 STABILITY EVALUATION AND RECOMMENDATIONS
4.1 Stability EvaluationA two-dimensional global stability analysis of the existing slope was performed using the computer program SLOPE/W. These analyses were performed along three (3)sections, with each taken perpendicular to the slope in close proximity to Outfalls IV9 and IV10 and one approximately midway between Outfalls IV9 and IV8. For this analysis, the following assumptions were made:
1) The limits of embankment stabilization will extend between Outfalls IV8 and IV10.
2) The analysis was performed assuming a generalized soil profile as determined from the subsurface conditions encountered at each of the test borings. Between Outfalls IV8 and IV9, the soil profile was assumed to be consistent with that encountered at SB-3.
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3) Soil strength parameters utilized in the stability analyses were estimated based upon empirical relationships relating Standard Penetration Resistances (N-values) to the internal angle of friction for granular soils. Although the underlying deposits were largely composed of a mixture of sand and silt, recovered samples were identified as being non-plastic. As such, it was assumed that the soils possess only a frictional component of strength and no cohesive component.
4) Seismic analyses were performed using two (2) peak ground accelerations. The first was performed in accordance with the International Building Code, 2015 Edition, which stipulates a design event having a return period of 2,475 years. Under this event, the peak ground acceleration for use in the analysis was estimated to be 0.2046g. A second analysis was performed using a modal design event with a return period of 475 years. For this event, the peak ground acceleration was estimated to be 0.070g.
Using the above stated assumptions, the analyses were performed and indicate that the existing slope has the following safety factors against a global rotational failure for the long-term and transient seismic cases:
Analysis Case
Safety Factor Against Global Rotational Failure
Static Case Seismic Case– IBC/ASCE 7
Seismic Case – 475 year
Return PeriodSection A 1.13 0.78 0.99
Section B 1.04 0.69 0.90
Section C 1.27 0.86 1.10
Safety factors of 1.3 are considered acceptable for slopes under long-term conditions and safety factors of 1.1 are considered acceptable for seismic loading conditions. Slope stability output graphics are attached in Appendix E.
4.2 RecommendationsBased on the global stability analyses performed for each of the sections, the calculated factors of safety for Sections ‘A’ or ‘B’ against a rotational failure are less than the minimum required factor of safety under both the static and seismic loading conditions. At
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Section ‘C’, the calculated factor of safety under the static and 475-year return period seismic loading conditions was approximately equal to the minimum considered acceptable, although under the IBC/ASCE 7 seismic loading condition, the calculated factor of safety was less than the minimum required.
Several remedial measures were considered for enhancing the global and/or surficial stability. A brief description of each of the measures considered are listed in the following subsections.
Regardless of the remedial measure selected, it is recommended that the height of slope face opened at any one time be limited to that which is being actively worked. This will mitigate the chance of local instability and failure of the slope. The installation of temporary excavation support methods such as steel sheet piling may be required to mitigate slope instability resulting from oversteepening of the slopes during remedial construction.
The soils exposed upon removal of the site’s surficial cover will be subject to erosion and an erosion control system will be required to protect drainage ways and areas outside the construction limits.
Groundwater may be encountered during excavation and preparation of subgrade elevations. Where encountered, interceptor drains should be installed parallel to the slope so as to collect and discharge the groundwater prior to its emergence from the face of the slope.
Precipitation which falls directly upon the slope enhances the potential for erosion if the slope has been cleared of its existing vegetative cover due to remedial construction efforts. This will require remedial measures to prevent development of erosive velocities. So as to reduce the erosive potential, it is recommended that drainage channels or check dams be temporarily installed along the slope. Collected surface runoff should be discharged to areas that will prevent flooding of adjacent properties.
4.2.1 Remedial Measure 1 – Toe BermThis measure considers construction of a toe berm along the entire length of slope. The intent would be to improve global stability against a rotational failure as well as protect
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the toe against potential for erosion due to intermittent stream flows. It should be noted however that construction of a toe berm does not address surficial instability which may be present along the upper portions of the slope.
At each section, the toe berm would be keyed several feet into the existing slope and the overall width of the toe berm would be built outward away from the toe until an adequate factor of safety is achieved. It should be noted that the toe berm would be continuous along the length of slope and would need to be keyed into the same along its entire length. The tables below present the sizes of the toe berm utilized in the analysis and the resulting calculated factors of safety.
Analysis Case Berm Base Width (feet)
Berm Top Width (feet)
Height of Berm (feet)
Section A 15 15 24
Section B 15 15 11
Section C 10 10 10
Analysis CaseSafety Factor Against Global Rotational Failure
Static Case Seismic Case – IBC/ASCE 7
Seismic Case – 475 year
Return PeriodSection A with Toe Berm 1.26 0.88 1.12
Section B with Toe Berm 1.25 0.85 1.09
Section C with Toe Berm 1.34 0.90 1.16
The stone fill used to construct the toe berm would need to be sized such that the individual stones possess a size and weight adequate to resist anticipated maximum flow velocities.
Due to the geometry of the toe berm required to satisfy the global stability requirements, costs are expected to be significant. The existing unimproved maintenance road will likely need to be extended for the length of the slope to be worked and may need to be improved/reconstructed to accommodate construction activity. Construction of a toe berm
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would encroach upon the existing mapped wetlands and may generate permitting issues. In addition, realignment of the existing stream channel that is to occur under this project would need to be placed at a sufficient distance so as to prevent potential damming of flows in the stream.
4.2.2 Remedial Measure 2 – Sheet PilingAs an alternative to a stone fill toe berm, installation of steel sheet piling along the toe of slope was also considered. Installation of the sheet piling would enhance the global stability against rotational failure. The presence of the steel sheet piling would also provide some degree of armoring for the slope of the toe against erosion resulting from high flows. It should be noted, however, that installation of sheet piling will not enhance the slope’s surficial stability unless regrading of the slope is performed in conjunction with installation of the sheeting. Based on preliminary analyses performed, sheet piling installed a limited distance above the current toe of slope would be required to have an approximate installed depth of 20 feet to 25 feet and a minimum section modulus of 6.6 square inches per lineal foot to provide a factor of safety in excess of 1.3.
Similar to construction of the toe berm, installation of steel sheet piling is likely to be costly due to the material expense and potential need to install the sheet piling with a crane. As a result of the slope height and inclination, the selected sheet pile is likely to require a relatively large cross-sectional area and tieback anchors may be required for its internal stability. Installation of sheet piling would require access to the toe of slope for an excavator or crane, which would likely require extension and/or improvements to the existing unimproved road present. Additionally, as vibratory methods are often utilized for installation of sheet piling, their installation may result in unpredictable local instability along the slope given the non-plastic nature of the soils.
4.2.3 Remedial Measure 3 – RegradingRegrading of the existing slope was evaluated assuming that imported granular soils could be utilized for bulk fill placement. Based on the results of our stability analysis, it was determined that the slope would need to be regraded to a maximum inclination no steeper than 2:1 (Horizontal: Vertical) to provide a factor of safety against failure of 1.3 or greater against both surficial and global failures.
It should be understood that this measure would require significant clearing of the existing
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slope. In addition, establishment of a 2:1 (H:V) slope would require significant amounts of imported fill. As the existing slopes range from inclinations of 1.4:1 to 1.8:1 (H:V), establishment of this flatter slope would shift the toe of slope approximately 35 feet to 60 feet east of its current location and would require significant filling of the existing mapped wetlands.
4.2.4 Remedial Measure 4 – Toe Berm with Surface TreatmentAnother remedial measure which would address both surficial and global instability of the slope would be construction of a toe berm along with placement of a surface course of stone. Similar to Remedial Measure 1, a toe berm would be constructed as previously discussed under that option. In order to achieve a factor of safety against global rotational failure in excess of 1.3, the size of the toe berm at Sections A & B would remain unchanged from that identified in the Table under Remedial Measure 1. The height of the toe berm at Section C could be decreased from 10 feet to 8 feet under this measure.
Additionally, the upper portion of the slope could be surfaced with a course of stone. This course of stone would help to mitigate erosion potential which may trigger surficial instability. It should be noted that this stone course will not address global stability issues. The surficial stability of the stone course could not be accurately modeled using the computer program SLOPE/W due to the relative thinness of the surficial course of stone with respect to the overburden. It is recommended that the stone course have a minimum thickness of 2 feet along the upper portions of the slope and become progressively thicker down to its base. Placement of the stone will require clearing of all trees and vegetation from along the length of slope. It is recommended that the crushed stone used for this purpose meet the requirements of Item 706.04 Type I stone filling as noted in the Vermont Agency of Transportation’s 2018 Standard Specifications for Construction.
4.2.5 SummaryThe remedial measures discussed above address the mechanisms that can potentially impact slope performance, those being specifically:
1) The potential for global rotational slope failure.2) The potential for near surface instability and erosion.3) Toe erosion due to intermittent stream flows.
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Based on our analyses, it is apparent that measures needed to address global rotational failure will require significant construction along the toe. A stone fill Toe Berm built out into the wetland area is likely to be subject to permitting issues as well as realigning the existing channel. Sheet piling driven along the toe will be less intrusive than a toe berm, but will likely be costly due to material and installation costs as well as the potential need to anchor sheeting into the existing slope. Additionally, as the soils are largely composedof granular soils, vibrations induced in the soils during installation of the sheet piling could cause local slope instability.
It should be noted that both of the above described measures (Toe Berm and Sheet Piling) are directed to improving global stability against rotational failure and do not address surficial instability along the length and width of the slope face. Under either of these remedial measures, periodic maintenance along the slope face should be anticipated to address ongoing surficial instability. Measures that would improve the surficial stability(Regrading) would require regrading of the slope to an inclination of 2:1 (Horizontal: Vertical) or placement of stone fill over the entire slope. Both of these surficial stability measures would involve clearing of the slopes’ vegetative cover as well as fill placement within the mapped wetlands, both of which we understand are undesirable to the City of Burlington.
Of the remedial measures outlined in this report, only two (2) of the remedial measures(Regrading & Toe Berm with Surface Treatment) would address both the global stability against rotational failure and surficial instability issues. However, as previously described, both of these measures would have potential impacts on the mapped wetlands as well as require clearing of the slopes’ vegetative cover.
A summary Table outlining the calculated factors of safety against global rotational failure at each Section for the various remedial measures discussed herein is provided on the following page.
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Section & ConditionSafety Factor Against Global Rotational Failure
Static CaseSeismic Case –IBC/ASCE 7
Seismic Case –Modal Event
Section AExisting Condition 1.13 0.78 0.99Remedial Measure 1 – Toe Berm 1.26 0.88 1.12Remedial Measure 2 – Sheet Piling
1.43 1.01 1.26
Remedial Measure 3 –Regrading at 2:1 (H:V)
1.35 0.86 1.14
Remedial Measure 4 – Toe Berm with Surface Treatment
1.29 0.89 1.12
Section BExisting Condition 1.04 0.69 0.90Remedial Measure 1 – Toe Berm 1.25 0.85 1.09Remedial Measure 2 – Sheet Piling
1.60 1.10 1.39
Remedial Measure 3 –Regrading at 2:1 (H:V)
1.65 0.88 1.18
Remedial Measure 4 – Toe Berm with Surface Treatment
1.37 0.94 1.19
Section CExisting Condition 1.27 0.86 1.10Remedial Measure 1 – Toe Berm 1.34 0.90 1.16Remedial Measure 2 – Sheet Piling
1.64 1.10 1.42
Remedial Measure 3 –Regrading at 2:1 (H:V)
1.28 0.82 1.09
Remedial Measure 4 – Toe Berm with Surface Treatment
1.41 0.95 1.22
4.3 Weather Considerations Construction activity should be limited during wet and freezing weather and the site soils may require drying or thawing before construction activities may continue. The contractor should anticipate the need for water to temper fills in order to facilitate compaction during
18-0764.1 S January 4, 2019
12
dry weather. If construction takes place during cold weather, subgrades must be protected during freezing conditions. Fill must not be placed on frozen soil; and once placed, the soil must be protected from freezing.
4.4 Design Review and Construction TestingS.W.COLE should be retained to review the construction documents prior to bidding to determine that our recommendations have been properly interpreted and implemented.
A soils testing program should be implemented during construction to observe compliance with the design concepts, plans, and specifications. S.W.COLE is available to observe earthwork activities as well as to provide testing and IBC Special Inspection services for soils.
5.0 CLOSUREIt has been a pleasure to be of assistance to you with this phase of your project. We look forward to working with you during the construction phase of the project.
Sincerely,
S. W. Cole Engineering, Inc.
Thomas J. Morgan, P.E.Senior Geotechnical Engineer
TJM:ajh
S. W. Cole Engineering,
Thomasas J.. MoMorgrgana , P.E.ESenioror Geeototecchnical Engin
Appendix ALimitations
This report has been prepared for the exclusive use of Vanasse Hangen Brustlin, Inc,for specific application to the proposed BTV Outfalls IV8, IV9, & IV10 in Burlington,Vermont. S. W. Cole Engineering, Inc. has endeavored to conduct the work in accordance with generally accepted soil and foundation engineering practices. No warranty, expressed or implied, is made.
The soil profiles described in the report are intended to convey general trends in subsurface conditions. The boundaries between strata are approximate and are based upon interpretation of exploration data and samples.
The analyses performed during this investigation and recommendations presented in this report are based in part upon the data obtained from subsurface explorations made at the site. Variations in subsurface conditions may occur between explorations and may not become evident until construction. If variations in subsurface conditions become evident after submission of this report, it will be necessary to evaluate their nature and to review the recommendations of this report.
Recommendations contained in this report are based substantially upon information provided by others regarding the proposed project. In the event that any changes are made in the design, nature, or location of the proposed project, S. W. Cole Engineering, Inc. should review such changes as they relate to analyses associated with this report. Recommendations contained in this report shall not be considered valid unless the changes are reviewed by S. W. Cole Engineering, Inc.
APPENDIX B
ROUTE 127
MANHATTAN DRIVE
SB-1
SB-2
SB-3
0+00
0+50
1+00
1+50
2+00
2+502+
57
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1+00
1+50
2+00
2+50
2+73
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1+00
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2+00
2+25
SEC
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N C
SEC
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N B
SECTION A
VANASSE HANGEN BRUSTLIN, INC.
BTV OUTFALLS IV8, IV9 & IV10MANHATTAN DRIVE
BURLINGTON, VERMONT
EXPLORATION LOCATION PLAN
Job No.:Date :
18-0764.101/08/2019
Scale:Sheet:
1" = 40'1
LEGEND:
APPROXIMATE BORING LOCATION
NOTES:
1. EXPLORATION LOCATION PLAN WAS PREPARED FROM ASCALE PLAN OF THE SITE PROVIDED BY VANASSEHANGEN BRUSTLIN, INC., RECEIVED VIA E-MAIL 12/12/2018IN AUTOCAD DWG FORMAT.
2. THE BORINGS WERE LOCATED IN THE FIELD BY SURVEYBY OTHERS AND PROVIDED ON THE ABOVE REFERENCEDPLAN.
3. THIS PLAN SHOULD BE USED IN CONJUNCTION WITH THEASSOCIATED S. W. COLE ENGINEERING, INC.GEOTECHNICAL REPORT.
4. THE PURPOSE OF THIS PLAN IS ONLY TO DEPICT THELOCATION OF THE EXPLORATIONS IN RELATION TO THEEXISTING CONDITIONS AND PROPOSED CONSTRUCTIONAND IS NOT TO BE USED FOR CONSTRUCTION.
Feet0 40 80
ELE
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TION
(FT.) ELE
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Section C
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(FT.) ELE
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Section A
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Section B
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0+00 1+00 2+00 2+73
SECTIONS
Job No.:Date :
Scale:Sheet:
1" = 20' H:V2
NOTES:
1. SECTIONS WERE PREPARED FROM EXISTING CIVIL 3DSURFACE PROVIDED IN BASE FILE (SEE NOTE 1, SHEET 1)AND ARE PRESENTED FOR THE PURPOSE OF INDICATINGTRENDS AND SHOULD BE USED IN CONJUNCTION WITHTHE ASSOCIATED S. W. COLE ENGINEERING, INC.GEOTECHNICAL REPORT.
2. THE PURPOSE OF THIS PLAN IS ONLY TO DEPICT THEEXISTING SLOPE AND IS NOT TO BE USED FORCONSTRUCTION.
VANASSE HANGEN BRUSTLIN, INC.
BTV OUTFALLS IV8, IV9 & IV10MANHATTAN DRIVE
BURLINGTON, VERMONT
18-0764.101/08/2019
APPENDIX C
KEY TO THE NOTES & SYMBOLSTest Boring and Test Pit Explorations
All stratification lines represent the approximate boundary between soil types and the transition may be gradual.
Key to Symbols Used:
w - water content, percent (dry weight basis)qu - unconfined compressive strength, kips/sq. ft. - laboratory testSv - field vane shear strength, kips/sq. ft.Lv - lab vane shear strength, kips/sq. ft.qp - unconfined compressive strength, kips/sq. ft. – pocket penetrometer testO - organic content, percent (dry weight basis)WL - liquid limit - Atterberg testWP - plastic limit - Atterberg testWOH - advance by weight of hammerWOM - advance by weight of manWOR - advance by weight of rodsHYD - advance by force of hydraulic piston on drillRQD - Rock Quality Designator - an index of the quality of a rock mass.
T - total soil weightB - buoyant soil weight
Description of Proportions: Description of Stratified Soils
Parting: 0 to 1/16” thicknessTrace: 0 to 5% Seam: 1/16” to ½” thicknessSome: 5 to 12% Layer: ½” to 12” thickness“Y” 12 to 35% Varved: Alternating seams or layersAnd 35+% Occasional: one or less per foot of thicknessWith Undifferentiated Frequent: more than one per foot of thickness
REFUSAL: Test Boring Explorations - Refusal depth indicates that depth at which, in the drill foreman's opinion, sufficient resistance to the advance of the casing, auger, probe rod or sampler was encountered to render further advance impossible or impracticable by the procedures and equipment being used.
REFUSAL: Test Pit Explorations - Refusal depth indicates that depth at which sufficient resistance to the advance of the backhoe bucket was encountered to render further advance impossible or impracticable by the procedures and equipment being used.
Although refusal may indicate the encountering of the bedrock surface, it may indicate the striking of large cobbles, boulders, very dense or cemented soil, or other buried natural or man-made objects or it may indicate the encountering of a harder zone after penetrating a considerable depth through a weathered or disintegrated zone of the bedrock.
9
APPENDIX D
Project Name BURLINGTON VT - MANHATTAN DRIVE CULVERTS IV 9.0 & 10.0 RECONSTRUCTION - GEOTECHNICAL ENGINEERING SERVICES
Project Number 18-0764.1Lab ID 555V
Material Source NATIVE SOILDate Completed 12/13/2018Tested By ETHAN THOMAS
Date Received 12/12/2018
ASTM C-117 & C-136
Client VANASSE HANGEN BRUSTLIN, INC.Exploration SB-2, S-2, 5'-7'
Report of Gradation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.00100.01000.10001.000010.0000100.0000
SIEVE SIZE - mm
AMO
UN
T PA
SSIN
G
3" 2" 1" #10 #20 #40 #100 #2001/2" #4
SIEVE SIZE AMOUNT PASSING (%)STANDARD DESIGNATION (mm/μm)
1" 10025.0 mm1/2" 9812.5 mm1/4" 936.3 mm
No. 4 11.6% Gravel884.75 mmNo. 10 672.00 mmNo. 20 44850 umNo. 40 82.3% Sand23425 umNo. 60 14250 um
No. 100 10150 umNo. 200 6.1% Fines6.175 um
Comments: Sheet
Project Name BURLINGTON VT - MANHATTAN DRIVE CULVERTS IV 9.0 & 10.0 RECONSTRUCTION - GEOTECHNICAL ENGINEERING SERVICES
Project Number 18-0764.1Lab ID 556V
Material Source NATIVE SOILDate Completed 12/13/2018Tested By ETHAN THOMAS
Date Received 12/12/2018
ASTM C-117 & C-136
Client VANASSE HANGEN BRUSTLIN, INC.Exploration SB-2, S-8, 35'-37'
Report of Gradation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.00100.01000.10001.000010.0000100.0000
SIEVE SIZE - mm
AMO
UN
T PA
SSIN
G
3" 2" 1" #10 #20 #40 #100 #2001/2" #4
SIEVE SIZE AMOUNT PASSING (%)STANDARD DESIGNATION (mm/μm)
1" 10025.0 mm1/2" 10012.5 mm1/4" 1006.3 mm
No. 4 0% Gravel1004.75 mmNo. 10 1002.00 mmNo. 20 100850 umNo. 40 10.2% Sand99425 umNo. 60 98250 um
No. 100 96150 umNo. 200 89.8% Fines89.875 um
Comments: Sheet
Project Name BURLINGTON VT - MANHATTAN DRIVE CULVERTS IV 9.0 & 10.0 RECONSTRUCTION - GEOTECHNICAL ENGINEERING SERVICES
Project Number 18-0764.1Lab ID 557V
Material Source NATIVE SOILDate Completed 12/13/2018Tested By ETHAN THOMAS
Date Received 12/12/2018
ASTM C-117 & C-136
Client VANASSE HANGEN BRUSTLIN, INC.Exploration SB-2,S-16, 75'-77
Report of Gradation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.00100.01000.10001.000010.0000100.0000
SIEVE SIZE - mm
AMO
UN
T PA
SSIN
G
3" 2" 1" #10 #20 #40 #100 #2001/2" #4
SIEVE SIZE AMOUNT PASSING (%)STANDARD DESIGNATION (mm/μm)
1" 10025.0 mm1/2" 10012.5 mm1/4" 1006.3 mm
No. 4 0% Gravel1004.75 mmNo. 10 992.00 mmNo. 20 99850 umNo. 40 20.3% Sand98425 umNo. 60 95250 um
No. 100 84150 umNo. 200 79.7% Fines79.775 um
Comments: Sheet
APPENDIX E
Section A – Existing Conditions
Section A – Existing Conditions under IBC Seismic Loading Condition
Section A – Existing Conditions under Modal Seismic Loading Conditions
Section B – Existing Conditions
Section B – Existing Conditions under IBC Seismic Loading Condition
Section B – Existing Conditions under Modal Seismic Loading Conditions
Section C – Existing Conditions
Section C – Existing Conditions under IBC Seismic Loading Condition
Section C – Existing Conditions under Modal Seismic Loading Conditions
Section A – Remedial Measure Toe Berm Option
Section A – Remedial Measure Toe Berm Option under IBC Seismic Loading Conditions
Section A – Remedial Measure Toe Berm Option under Modal Seismic Loading Conditions
Section B – Remedial Measure Toe Berm Option
Section B – Remedial Measure Toe Berm Option under IBC Seismic Loading Conditions
Section B – Remedial Measure Toe Berm Option under Modal Seismic Loading Conditions
Section C – Remedial Measure Toe Berm Option
Section C – Remedial Measure Toe Berm Option under IBC Seismic Loading Conditions
Section C – Remedial Measure Toe Berm Option under Modal Seismic Loading Conditions
Section A – Remedial Measure Sheet Piling Option
Section A – Remedial Measure Sheet Piling Option under IBCSeismic Loading Conditions
Section A – Remedial Measure Sheet Piling Option under Modal Seismic Loading Conditions
Section B – Remedial Measure Sheet Piling Option
Section B – Remedial Measure Sheet Piling Option under IBC Seismic Loading Conditions
Section B – Remedial Measure Sheet Piling Option under Modal Seismic Loading Conditions
Section C – Remedial Measure Sheet Piling Option
Section C – Remedial Measure Sheet Piling Option under IBCSeismic Loading Conditions
Section C – Remedial Measure Sheet Piling Option under Modal Seismic Loading Conditions
Section A – Remedial Measure Regraded Slope Option
Section A – Remedial Measure Regraded Slope under IBC Seismic Loading Conditions
Section A – Remedial Measure Regraded Slope under Modal Seismic Loading Conditions