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GEOTECHNICAL DESIGN REPORT ROUTE 191 EMBANKMENT STABILIZATION NEWPORT, VERMONT VTRANS NEWPORT STP 1343(22) CONTRACT PS0475 Submitted To: Vermont Agency of Transportation Construction and Materials Bureau 2178 Airport Road, Unit-B Berlin, VT 05641-8628 Attention: Callie Ewald, PE Submitted By: Golder Associates Inc. 670 North Commercial Street, Suite 103 Manchester, NH 03101 USA Distribution: E-file – Vermont Agency of Transportation 1 Copy – Golder Associates Inc. November 2017 Project No. 1668897

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November 8, 2017 Project No.: 1668897

Callie Ewald, PE Vermont Agency of Transportation Construction and Materials Bureau 2178 Airport Road, Unit-B Berlin, VT 05641-8628

RE: GEOTECHNICAL DESIGN REPORT ROUTE 191 ROADWAY EMBANKMENT NEWPORT, VERMONT VTRANS NEWPORT STP 1343(22) CONTRACT NUMBER PS0475

Dear Ms. Ewald:

Golder Associates Inc. (Golder) is pleased to submit to the Vermont Agency of Transportation (VTrans) this Geotechnical Design Report for the embankment slide stabilization on Route 191 in Newport, Vermont. Golder has been working on the final design elements for the slide stabilization since August 2015. This report provides a brief summary of background project information and focuses on final design elements for: the groundwater extraction system for the deep slide stabilization; regrading and drainage provisions for the upper embankment slope shallow stabilization; slide headscarp sealing; and, our evaluations of the stability of a new proposed access road to the extraction well site area.

Our work was conducted in accordance with the scope, schedule, and budget described in our proposal dated January 27, 2017, and your Notice to Proceed dated February 2, 2017. The terms and conditions governing the work are stated in our On-Call Geotechnical Services agreement with VTrans (Contact No.: PS0475). It has been a pleasure working with VTrans on this project. Please contact us if you have any questions concerning our report or require additional information.

Sincerely,

GOLDER ASSOCIATES INC. Jeffrey D. Lloyd, PE Kevin Killoran, PE Senior Project Engineer Senior Engineer Jay R. Smerekanicz, PG Christopher C. Benda, PE Associate and Senior Consultant Practice Leader Mark S. Peterson, PE Principal

JDL/drb

November 2017 i Project No.: 1668897

171108 final newport design report.docx

Table of Contents

EXECUTIVE SUMMARY ........................................................................................................................ ES-1 1.0 INTRODUCTION .............................................................................................................................. 1

1.1 Site Conditions ............................................................................................................................. 1 1.2 Site and Project History ................................................................................................................ 2

2.0 SUBSURFACE EXPLORATIONS ................................................................................................... 5 2.1 Previous Explorations .................................................................................................................. 5 2.2 2017 Access Road Explorations .................................................................................................. 5

2.2.1 Test Boring Explorations .......................................................................................................... 6 2.2.2 DCP Probes ............................................................................................................................. 6

3.0 LABORATORY TESTING ................................................................................................................ 7 3.1 Prior Laboratory Testing ............................................................................................................... 7 3.2 2017 Testing................................................................................................................................. 8

4.0 SUBSURFACE CONDITIONS ......................................................................................................... 9 4.1 Summary of Sitewide Subsurface Condition ................................................................................ 9

4.1.1 Soil Conditions ......................................................................................................................... 9 4.1.2 Bedrock Conditions ................................................................................................................ 10 4.1.3 Groundwater Conditions ........................................................................................................ 11

4.2 Conditions at Proposed Access Road ....................................................................................... 11 5.0 GROUNDWATER MODELING ...................................................................................................... 13 6.0 FINAL DESIGN EVALUATIONS .................................................................................................... 15

6.1 General ....................................................................................................................................... 15 6.2 Deep-Seated Slide Stabilization – Groundwater Extraction System ......................................... 15

6.2.1 Extraction Well Design ........................................................................................................... 18 6.2.2 Well Screen Filter Pack .......................................................................................................... 20 6.2.3 Entrance, Approach and Uphole Velocity Estimates ............................................................. 21 6.2.4 Pump and Pump Controls ...................................................................................................... 22

6.3 Upper Embankment Slope Stabilization .................................................................................... 24 6.3.1 Slope Flattening ..................................................................................................................... 24 6.3.2 Toe Drain ............................................................................................................................... 24 6.3.3 Existing Drainage Systems in Stability Berm Area ................................................................ 25

6.4 Headscarp Seal .......................................................................................................................... 26 6.5 Cutoff Trench Drain .................................................................................................................... 27 6.6 Access Road Stability ................................................................................................................ 28

6.6.1 Stability Analysis .................................................................................................................... 28 6.6.2 Stabilization Provisions .......................................................................................................... 29

7.0 CONSTRUCTION AND POST-CONSTRUCTION CONSIDERATIONS ....................................... 30 7.1 Deep-Seated Slide Extraction Well Construction Considerations ............................................. 30

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7.2 Upper Embankment Slope and General Site Construction Considerations .............................. 30 7.3 Geotechnical Instrumentation .................................................................................................... 31 7.4 Post-Construction Groundwater Sampling and Analysis ........................................................... 31

8.0 CLOSING AND LIMITATIONS ....................................................................................................... 32

List of Tables Table 1 Chronology of Key Project Events Table 2 400-Series Boring and Piezometer Summary Table 3 DCP Test Results Summary Table 4 Soil Testing Results Summary Table 5 (in text) Well Construction Details and Projected Pumping Water Levels Table 6 (in text) Extraction Well Screen Design Criteria Table 7 (in text Estimated Total Dynamic Head (TDH) and Pump Design Parameters

List of Figures Figure 1 Site Location Map Figure 2 Existing Conditions (2012) and Locations of Borings and Instrumentation

Installed from 1966 to 2013 Figure 3 Recommended Stabilization Features and Locations of 2017 Explorations Figure 4 Cross Section A-A’ Geotechnical Data Figure 5 (in text) Extraction Well Stratigraphic Cross Section Figure 6 (in text) Selection of Filter Pack and Well Screen Slot Size Figure 7 Potential Trenching Impact on Horizontal Drains Figure 8 Typical Headscarp Seal Section & Geomembrane Tie-In Underdrain Detail

List of Appendices Appendix A 400 Series Boring Logs Appendix B Laboratory Test Results

B-1 - From 400-Series Boring Samples B-2 - 200- and 300-series Boring Sieve Analyses Used for Extraction Well Design

Appendix C Groundwater Modeling Appendix D Total Dynamic Head Worksheets Appendix E Manufacturer’s Pump Curve and Performance Specifications Appendix F Specifications Appendix G Access Road Global Stability Results

November 2017 ES-1 Project No.: 1668897


EXECUTIVE SUMMARY Slope movements at an embankment fill constructed for Route 191 connecting Interstate 91 and Newport,

Vermont have been the subject of investigations, mitigation construction and monitoring by the Vermont

Agency of Transportation (VTrans) for over 45 years since 1971. Mitigation measures, subsurface

investigations and stability analyses in 1971-1991 concluded that continuous slope movements resulted

from embankment fill loads and groundwater pressure effects on a circular slip surface extending from the

uphill side of the roadway to the downslope toe of the embankment fill. Mitigation measures constructed in

1991 based on this hypothesis were ineffective. Based on monitoring data, additional subsurface

investigations, and stability analyses completed 1991 to present, VTrans concluded roadway slope

movements are part of a much larger non-circular slide mass extending up to 120 feet below ground surface

These later studies indicate a complex combination of geology, groundwater conditions, creep behavior,

and soil strength characteristics are causing the slope movements, all of which directly bear on an effective

mitigation plan to monitor and preferably arrest future slope movements.

In 2011 VTrans evaluated mitigation alternatives including stability berm removal; embankment

replacement; pile or drilled shaft reinforcement; and drainage of groundwater pressure. VTrans concluded

reduction of groundwater pressures would probably be the most effective stabilization method; however,

developing cost effective measures to sufficiently reduce groundwater pressures would require further

evaluation, and additional laboratory testing was warranted to better understand the creep behavior of the

site soils and related risks to long term roadway stability.

In 2012 Golder assisted VTrans in developing a plan to manage future slope movements. Following a

review of the extensive records of site and project information, and performing a preliminary reassessment

of slide mass stability, Golder developed a long-term, sustainable monitoring plan coupled with

recommendations for additional site investigations and testing to fill data gaps, develop design plans to

mitigate slope movements, and manage risk.

In 2013, VTrans requested Golder conduct an extensive geotechnical and hydrogeologic investigation,

including the installation of remote instrumentation to monitor slope movements and groundwater levels.

Twenty-two (22) additional investigation locations were included in the program, including borings advanced

using both sonic and conventional drive and wash drilling techniques, to depths up to 183 feet. The drilling

program augmented existing geologic, geotechnical, and hydrogeologic knowledge, and included additional

monitoring wells, piezometers and inclinometers to further monitor site conditions.

In 2014 – 2015, following completion of the field program, Golder refined the geologic, geotechnical and

hydrogeological conceptual models of the site to evaluate potential remedial options to slow landslide

movement. Based on the importance of groundwater pressures directly bearing on landslide movement, a

calibrated numerical groundwater flow model, based on the refined conceptual geologic/

November 2017 ES-2 Project No.: 1668897


geotechnical/hydrogeologic models, was used to simulate the reduction in pore pressure under various

groundwater withdrawal scenarios, which were used in slope stability models to evaluate the reduction in

sliding. The ultimate remedial design approach included active groundwater extraction wells placed on

VTrans property.

In 2016 - 2017, Golder conducted additional evaluations to support the final remedial design. These tasks

included: groundwater testing; extraction well system design; upgradient impact evaluation; headscarp

infiltration reduction design; cutoff trench design; upper slope surficial improvements; trench drain design;

and existing drainage design improvements.

This report provides documentation of these evaluations not presented previously, including field

investigations conducted in 2017, results of the groundwater modeling, geotechnical design, and

construction considerations.

November 2017 1 Project No.: 1668897


1.0 INTRODUCTION This report summarizes the basis and recommendations for final design of landslide stabilization systems

for embankment fills forming a portion of Route 191 in Newport, Vermont approximately 1.2 miles northwest

of Interstate I-91 as shown on Figure 1. The design represents the culmination of investigations, attempted

mitigation construction, and evaluations of slope movement stabilization alternatives that have been

ongoing at this site since the roadway was constructed in 1971. Since 2008 a large slide mass has been

known to be present along a non-circular slide plane extending about 120 feet (ft) below ground surface

and 600 ft long between Route 191 and the Clyde River to the north. Subsequent monitoring of slope

movements and groundwater pressures combined with detailed field investigations and testing led to the

development of alternative conceptual stabilization plans for the deep-seated slide mass as well as for

shallow slide areas on the upper embankment fill slopes. Working in collaboration with VTrans and their

civil design consultant Stantec of South Burlington, Vermont, Golder completed a preliminary design

process and then a final design for an extraction well stabilization system for the deep-seated slide mass

and a slope reconstruction and drainage design for the shallow upper slope area. This report briefly

summarizes the history of work leading to the development of the stabilization alternatives considered

during preliminary design, and then describes the rationale, supporting analytical methods and details for

the recommended final stabilization design.

1.1 Site Conditions Existing site conditions in the general area of the Route 191 embankment slope movements are shown on

Figure 2 and include the following primary features:

Route 191 roadway settlements have occurred since 1971 primarily in the section between Stations 111+00 and 119+00. The road grade drops about 45 ft downhill to the west within the subject area.

The approximate location of a landslide headscarp (apparent upslope boundary based on abrupt ground displacement) of the slide mass observed in March 2012 is shown on Figure 2. The headscarp passes roughly along the toe of the uphill embankment fill slope at about Station 115+00, crossing the roadway at about Station 112+50 to the east and Station 117+50 to the west, and extends east and west on the downslope north of the roadway where the edges of the headscarp are not evident.

The slope on which the fill embankment is located extends about 500 ft uphill from Route 191 and about 600 ft downhill.

The upslope topography is believed to be unchanged since original road construction and includes wooded slopes typically at about 2.5H:1V. A narrow ravine provides surface water drainage for the eastern portion of the slope drainage and carries flow to a 30-inch diameter culvert headwall located at about Station 112+00 on the south side of the roadway embankment.

Site conditions downslope of Route 191 include the slide mass area and slopes, benches and waterways extending down from the edge of road pavement including:

The grass covered embankment fill slope.



A grass covered horizontal bench about 40 ft wide forming the crest of a stabilizing berm placed in 1991.

An abandoned power canal (partially filled with water) that previously carried water from the Great Bay Hydro Dam (previously the Citizen’s Canal Dam) east of the site to a penstock and turbine located west of the site.

Wooded and undulating flatter terrain dropping about 30 ft in elevation over roughly a 200 ft distance to the Clyde River at the base of the slope.

The ground surface topography shown on Figure 2 is based on survey information provided by VTrans1

and reflects cut/fill slopes and natural slopes. The extent of the slide mass directly beneath the roadway is

evident from the sag (settlement) of the roadway surface grade and the downward warp of the guardrail

along the north edge of pavement. The fill slopes of the roadway embankment are generally at 2H:1V, with

localized areas as steep as about 1.4H:1V. Secondary surficial scarp features (indicative of shallow

sloughs or slides) are present within the western portion of the embankment fill slope (approximately Station

116+00 to 119+00). Natural slopes above the abandoned power canal are generally much steeper than

the terrain below the Great Bay Hydro access road. Above the canal, natural slopes typically vary from

about 1.6H:1V to 6H:1V, with occasional areas showing signs of shallow instability and surface creep

(tilting trees, bowed tree trunks, slumps). Below the Great Bay Hydro access road the ground surface is

relatively flat (generally about 10H:1V), undulating and wet.

1.2 Site and Project History Slope movements of the embankment have been the subject of geotechnical investigations, slide repairs

and monitoring by VTrans for over 45 years since the roadway was constructed in 19712. The history of

construction, slope movements, road repairs, investigations and mitigation activities has previously been

summarized by VTrans3,4 and Civil Engineering Associates (CEA)5. A chronology of key project events is

listed in Table 1.

Mitigation measures, subsurface investigations and stability analyses completed over the 20 year period

from 1971 to about 1991 concluded that continuous slope movements were relatively shallow and the result

of embankment fill loads. A stability berm constructed in 1991 at the toe of the embankment fill proved to

be ineffective. Based on monitoring data, additional subsurface investigations and stability analyses

completed from 1991 to 2011, the roadway slope movements were concluded to be part of a much larger

non-circular slide mass extending up to 120 ft below ground surface and affect an overall slope length of

1 VTrans (2012). Base map titled “Newport VT 191 Revised Bore Plan 020409.DGN”, dated March 20, 2012. 2 Golder Associates Inc.(2012). “Review of Landslide Records and Analyses, Route 191 Embankment, Newport, Vermont”, VTrans Newport STP 1343(22), Contract PS0172, Project No. 123-87445, November 29, 2012. 3 A-Baki, S. and Batchelder-Adams, C. (1989). Slide Remediation Report for Derby-Newport F134-3(19), Materials and Research Division, Vermont Agency of Transportation, November 1989. 4 Allen, C. and Benda, C., VTrans (2011). VT-191 in Newport, VT – A Landslide Case History, presented at American Society of Civil Engineers (ASCE) Geo-Institute Landslide Conference, Norwich University, Norwich, VT, April 23, 2011. 5 Civil Engineering Associates, Inc. (2011). Geotechnical Report, “Creep Deformation Analysis, Slope Movements on Vermont Route 191 – Newport, Vermont”. Prepared for Vermont Agency of Transportation, Newport City STP 134-3(22), Contract No. PS0077. December 1, 2011.



roughly 600 ft. The mechanisms causing the deep seated slope movements include a complex combination

of geologic stratigraphy, groundwater conditions, and soil strength characteristics.

In 2012 Golder reviewed the body of investigative work completed for the site and identified several data

gaps to be addressed before mitigation design could be undertaken. The findings from that review are

presented in our 2012 report2. To address the data gaps Golder completed a series of site investigations,

field and laboratory testing, and installed in-situ instrumentation systems in 2013 and 2014. The data

produced from this work are summarized in our Geotechnical Data Report (GDR) dated August 22, 20146.

In 2014 and 2015 Golder completed groundwater modeling and stability analyses using the new data and

evaluated slide stabilization alternatives for the deep-seated slide mass. At our February 12, 2015 meeting

with VTrans we described the revised analyses of the deep-seated slide mass and assessments of

stabilization alternatives. The tasks involved with the revised analyses included refinement of the site

geologic model, creation of groundwater 3D numerical model using MODFLOW software, and updating the

slope stability model for the deep-seated slide mass using updated stratigraphy and pore water pressure

inputs from MODFLOW. The combined groundwater and stability models were then used to evaluate four

potential stabilization alternatives for lowering groundwater pressures on the deep slide plane with passive

and/or active groundwater extraction systems. In July 2015 VTrans selected the alternative with three

active extraction wells located on the stability berm below Route 191, and requested Golder to proceed

with preliminary and final design for the well system to stabilize the deep-seated slide. Preliminary design

plans were presented to VTrans in December 2015, and work on the final design was performed in 2016

and 2017.

In addition to the deep-seated slide movements Golder identified surficial slope displacements occurring at

the western portion of the upper embankment slope adjacent to the north side of Route 191. Although

these movements were located within the boundaries of the larger slide area, the mechanisms causing the

movements are separate from those affecting the deep-seated slide and a different set of stabilization

alternatives were evaluated for the upper slope slide areas. A summary of the analyses of the upper slope

stability and stabilization alternatives is discussed in Golder’s 20157 letter report. In July 2015 VTrans

selected an upper slope stabilization plan including the installation of an 8-ft deep trench drain along the

toe of the upper slope at the level of the stability berm and flattening the upper slope by placing additional

fill above the stability berm to achieve a 2.1H:1V slope. Golder was requested to proceed with preliminary

and final design of the plan to stabilize the upper slope. Preliminary design plans were presented to VTrans

in June 2016, and work on the final design was performed in 2016 and 2017.

6 Golder Associates Inc. (2014). “Geotechnical Data Report, Route 191 Embankment, Newport, Vermont”, VTrans Newport STP 1343(22), Contract PS0172, Project No. 133-87312, August 22, 2014. 7 Golder Associates Inc. (2015). “Summary of Deep-Seated and Upper Slope Stability Analyses”. July 14, 2015.



In 2015 VTrans engaged Stantec to provide civil design services for the reconstruction of Route 191 as part

of the stabilization work and to work together with Golder to provide preliminary and final design drawings

and specifications for the project. Stantec developed conceptual drawings in August 2016 and preliminary

drawings in April 20178 that included input from Golder for the geotechnical aspects of the work including

preliminary plans and details for the extraction well system, the upper slope stabilization, sealing the slide

headscarp, and installation of a groundwater cutoff trench across Route 191 upgradient of the slide area.

As part of this plan development Stantec developed preliminary plans and profiles for a new permanent

access road located from Route 191 to the extraction well system to be installed on the stability berm as

shown on Figure 3. Due to concerns for the stability of cuts and fills required to construct the access road,

Golder completed an additional field investigation in early 2017 in this area of the site and evaluated the

global stability of the access road fills.

8 Stantec (2017). Drawings titled “Preliminary Plans, Proposed Improvement, Newport City, County of Orleans, VT Route 191 (Principal Arterial)”, State of Vermont, Agency of Transportation, Project No. STP 134-3(22), February 10, 2017, provided to Golder April 5, 2017.



2.0 SUBSURFACE EXPLORATIONS Several subsurface exploration and testing programs have been completed at the site to assess soil,

bedrock and groundwater conditions and to install instrumentation systems over the past 45 years and are

described in detail in Golder’s 20121 and 20146 reports. Section 2.1 briefly describes the investigations

completed prior to 2017. Section 2.2 describes the exploration program completed in early 2017 for the

stability assessment of the new gravel roadway planned to provide access to the extraction well area on

the stability berm.

2.1 Previous Explorations VTrans completed subsurface explorations at the site in 1966 prior to embankment construction and during

three periods after construction: 1971 to 1974; 1989; and 2006 to 2009. As part of the 2006 to 2009

investigations VTrans installed initial instrumentation systems to monitor the behavior of the deep-seated

slide mass. During installation of two inclinometers adjacent to the Clyde River in late 2009, significant

artesian water pressures were encountered in confined sand layers at depth. The relief of artesian

pressures at the inclinometer boreholes resulted in lower hydraulic heads in monitoring wells near the

roadway, indicating hydraulic connectivity within confined hydraulic layers across the site.

Based on the data gaps identified in Golder’s 2012 report2, an extensive site investigation was completed

in 2013 that included twenty two (22) borings advanced using sonic and conventional cased-wash borings.

These explorations were conducted to better assess the complex site stratigraphy, obtain undisturbed

samples for laboratory testing, and to install piezometer and inclinometer instruments. To study the

hydrogeologic nature of the coarser sediment layers, eight open-standpipe piezometers were installed at

within three layers of interest, seven borings contained multilevel vibrating-wire piezometers grouted in

place, and three 4-inch pumping test wells were installed through the stability berm and screened in the

three coarsest layers. The 4-inch wells were used during a series of pumping tests conducted in August

2013 to assess hydraulic characteristics. Additional instrumentation installed in 2013 included two In-Place-

Inclinometer (IPI) arrays, and two ShapeAccelArray™ (SAA) inclinometers installed along the shoulder of

Route 191. Details of the 2013 investigation and laboratory testing are included in Golder’s 2014 data

report6 and details about the series of pumping tests are included in Golder’s pumping test report9.

2.2 2017 Access Road Explorations In March and April 2017 three borings and 20 Dynamic Cone Penetrometer (DCP) probes were made at

the locations shown on Figure 3 in the western portion of the planned access road to the extraction well

area and in the eastern upper embankment slope area. The explorations were made to assess the stability

of cut and fill sections of the access road where subsurface conditions had not previously been investigated

9 Golder Associates, Inc. (2014). “Pumping Test Investigation, Route 191 Embankment Slide, Newport, Vermont”, Project No. 133-87312, August 22, 2014. Included as Appendix G in Golder’s Geotechnical Data Report dated August 22, 2014 (Ref 2).



and to confirm existing surficial conditions assumed for the eastern upper slope stabilization area. The

exploration locations shown on Figure 3 were approximated from measurements to existing site features

and ground surface elevations at the explorations were estimated based on the topographic contours shown

on Figure 3.

2.2.1 Test Boring Explorations In March 2017 a VTrans drilling crew completed three borings (B-401, B-402, and B-403) at the locations

shown on Figure 3 with a CME-55 track rig. The borings were advanced using wash boring methods to

depths of 30 to 50 ft below ground surface. A Golder geotechnical engineer was on site during the

advancement of the test borings to monitor drilling activities, log the borings, and obtain soil samples.

Details of the sampling methods used, field data obtained, and soil conditions encountered are presented

on the boring logs included in Appendix A. A description of the boring log symbols and terms used for the

soil and rock descriptions is provided on Table A-1 preceding the logs. A summary of the boring location

and depth information is provided on Table 2.

Standard Penetration Test (SPT) sampling was conducted in all test borings at approximately 5-ft

increments using a standard 2 inch split spoon sampler with an automatic hammer system in accordance

with ASTM D1586. All borings were terminated in soil and no rock coring was performed.

A temporary open standpipe piezometer was installed in boring B-401 located near the shoulder of Route

191 to assess local groundwater conditions in the area of the proposed access road. Details of the

piezometer installation are provided on the log for B-401 and on Table 2. The piezometer borehole was

backfilled with sand and capped with a road box mounted just below the asphalt road surface. The road

box was cemented in place with Speed Crete™.

2.2.2 DCP Probes A total of 20 of DCP probes were completed at the locations shown in Figure 3 on April 5, 2017. The testing

was conducted in accordance with ASTM D695, Standard Test Method for Use of the Dynamic Cone

Penetrometer in Shallow Pavement Applications. The DCP apparatus consists of a sacrificial 60° cone 20

millimeter (mm) in diameter connected to a 16 mm diameter steel rod. The cone is advanced using a 17.6

pound hammer dropped 575 mm and the depth of penetration caused by the blows (i.e. hammer drops) is

recorded. DCP-1 through DCP-5 were performed below the proposed access road, DCP-6 through DCP-

13 were performed between the proposed access road and Route 191, and DCP-14 through DCP-20 were

performed in eastern upper slope areas where surficial stabilization re-grading is planned. A summary of

the DCP test results is provided in Table 3.



3.0 LABORATORY TESTING Extensive geotechnical laboratory testing of soil samples has been completed during previous

investigations to assess index and engineering properties and is presented, discussed and/or summarized

in our 20121 and 20146 reports. A limited groundwater analysis program was performed in 2015 on

groundwater samples collected from selected monitoring wells on the site. These prior testing programs

are discussed in Section 3.1. Section 3.2 discusses additional soil testing performed in 2017 on samples

collected as part of the access road investigation.

3.1 Prior Laboratory Testing As discussed in our 2012 report1, VTrans performed index and classification testing on soil samples

obtained from the 1966 to 1989 explorations, and more extensive index and engineering property testing

was performed on samples from the 2006 to 2009 explorations. Additional index and engineering property

tests were completed on soil samples collected during Golder’s 2013 field investigations. The 2013 testing

was conducted by VTrans (Construction and Materials Bureau Central Laboratory in Berlin, Vermont) and

the University of Massachusetts at Amherst under the direction of Dr. Don DeGroot, and testing results are

presented in Golder’s 2014 report6. The interpretation of these data provides the primary basis for soil

parameters used for the global stability analyses and groundwater modeling employed for the embankment

stabilization final design.

To assess the impacts of groundwater quality, if any, on the extraction well system design, Golder

completed a round of groundwater sampling from six site monitoring wells/inclinometers in 2015. The

sampling, analyses, results and interpretation are discussed in Golder’s 2015 letter report10. Each

groundwater sample was analyzed for major cation/anion species, and for Resource Conservation and

Recovery Act (RCRA) 8 metals that the United States Environmental Protection Agency (USEPA) uses for

primary and secondary drinking water standards. In general, the analytical results show that the inorganic

groundwater parameters sampled from monitoring wells and inclinometers screened within the lower sands

and gravels exist at concentrations below the standard limits of the Vermont Groundwater Quality

Standards (VGQS) and the United States Environmental Protection Agency’s Maximum Contaminant

Levels (USEPA MCLs). As presented in email correspondence between Rick Levey of the Vermont

Department of Environmental Conservation (DEC), Watershed Management Division, and Bruce Martin of

VTrans dated June 12, 2015, Golder understands that groundwater discharge from the groundwater

extraction system discussed herein would not violate water quality standards or pose a risk to aquatic biota

in the Clyde River. Furthermore, Golder understands that the DEC approves of the discharge and has

requested VTrans perform post-construction groundwater sampling to further document iron and

manganese concentrations. In additions to iron and manganese testing, Golder recommends testing the

10 Golder Associates Inc. (2015). Letter report titled “Groundwater Sampling and Analysis, Route 191 Embankment Slide, Newport, Vermont, VTrans Newport STP 1342(22)”. April 27, 2015.



groundwater for standard field chemistry parameters including temperature, pH, specific conductance,

Eh/redox potential, dissolved oxygen, and salinity.

The potential presence of deicing compounds at one of the wells may indicate runoff from Route 191 is

migrating down the failure scarp and entering the lower sand and gravel unit. To preclude this possibility

and to enhance stability, the final slide stabilization design includes a surface seal on the slide headscarp

to limit surface water infiltration into the lower sand and gravel unit (discussed in Section 6.2.2).

3.2 2017 Testing As part of the 2017 field investigation to support design for the proposed access road, geotechnical

laboratory tests were performed by VTrans on soil samples collected to assist in soil classification. The

testing was performed in accordance with applicable AASHTO and American Society for Testing Materials

(ASTM) testing procedures and is summarized below.

Soil Laboratory Test Testing Procedure Number of Tests Completed

Grain Size Analysis, sieve only AASHTO T88, ASTM D422 20

Natural Moisture Content AASHTO T265, ASTM D2216 20

Atterberg Limits AASHTO T89 & T90, ASTM D4318 6

Direct Shear AASHTO T236, ASTM D3080 3

The three direct shear tests were run on a single composite sample collected from boring B-401 using

material collected between 15 and 27 feet below ground surface. These tests were used to evaluate the

strength of the fill material in the existing embankment in the area of the proposed access road, and the

results were compared with three direct shear tests of the fill material obtained from the center of the

embankment during the 2013 investigation.

Selected soil testing results are included on the boring logs in Appendix A and summarized on Table 4.

Complete laboratory testing results are provided in Appendix B.



4.0 SUBSURFACE CONDITIONS The regional surficial geology and bedrock geology are described in detail in Golder’s 20121 and 20146

reports. A detailed description of soil, bedrock and groundwater conditions for the overall slide site area is

provided in Golder’s 20146 report, and a brief review of the major stratigraphic units is presented below in

Section 4.1. Boring logs providing detailed information on the conditions encountered at all project

explorations are either referenced in Golder’s 20121 report or included in in our 20146 report. Conditions

specific to the localized 2017 investigation for the proposed access road are discussed in Section 4.2.

4.1 Summary of Sitewide Subsurface Condition Evaluation of borehole log data and an assessment of bedrock surface contours indicate the bedrock

surface in the landslide area generally dips to the north, parallel to regional strike, and not parallel to the

northeasterly sloping topographic surface. Considering the bedrock slope and the similar orientation of

inclinometer displacements, the preferred direction of slide movement is interpreted to be to the north in

the general alignment of Subsurface Profile A-A’ shown on Figure 2. Profile A-A’ is shown on Figure 4 and

illustrates the major stratigraphic units interpreted to be present at the site.

4.1.1 Soil Conditions Soil deposits include a complex stratigraphy of fills and glaciolacustrine deposits consisting of interbedded

silts, fine sands, sands and gravels, silty clays and clays. The total soil thickness overlying bedrock is

interpreted to vary from roughly 172 ft at Route 191 to about 78 ft at the Clyde River. Dropstones, consisting

of ice-rafted cobbles and boulders, occur within all units, and are ubiquitous in the wooded surface areas

of the slide not affected by roadway and development construction activities. The boulders observed on

the surface are up to 6 ft or more in longest dimension.

The changes in soil layers were interpreted to generally be gradual and grade into and out of coarser

material, consistent with glaciolacustrine and fluvial deposits. Golder grouped the soil units into

distinguishable subsurface layers taking into account geological origin and engineering behavior; not all soil

layers were encountered in all of the borings. The interpreted stratigraphy is shown on Section A-A’ (Figure

4) and includes the following soil layers (in descending order):

Fill: Embankment fill was encountered under Route 191 (up to about 30 ft thick), at the stability berm (up to about 20 ft thick), and at the Great Bay Hydro Road area (about 15 ft thick). The fill material was observed to be reworked native material, probably from the roadway cuts immediately uphill and downhill of the site along Route 191. The fill is generally described as gray brown to dark gray brown, moist to wet, loose to dense, fine to coarse sand, some to trace silt, little to trace gravel, with layers of silt throughout (AASHTO: A-1-b to A-2-4 to A-4, USCS: SM).

Upper Silts and Sands: Starting at the ground surface, or at original grade in boring locations with embankment fill, is a layer of gray brown to dark brown, moist, medium dense to dense, layered fine to medium sand, fine sand, and silt, with trace fine gravel and coarse sand throughout (AASHTO: A-2-4 to A-4, USCS: SM to ML). Total thickness of this layer



ranges from about 10 ft at to 75 ft. This layer terminates at a point above the abandoned power canal.

Upper Silts and Clays: Below the upper silts and sands is a potentially continuous layer of stiff to hard, low plasticity varved silty clay (AASHTO: A-6 to A-7-6, UCSC: CL), ranging in thickness from about 3 to 15 feet and extending from uphill of B-302 above the roadway and terminating downhill at a point around B-311.

Middle Silts and Sands: Underlying the upper silts and clays is a layer of gray, dry to moist, very dense, layered silt, silty fine to medium sand, and clayey silt, with little to trace rounded gravel throughout (AASHTO: A-4, USCS: SM to ML). Occasional layers of dark gray, fine to medium sand were also encountered in this stratigraphy. Total thickness ranges from about 15 ft to 40 ft before tapering off between the canal and B-311.

Middle Sands and Gravels: Below the middle silts and sands is a separate layer of medium brown and orange brown, moist, very dense, silts, some fine sand, and some gravel, with pockets of gray, moist, very dense, fine to medium sand (AASHTO: A-1-b to A-2-4, USCS: SM). The thickness of this layer ranges from about 10 to 15 ft before it also tapers off between the canal and B-311.

Lower Clay: Underlying the middle silts, sands, and gravels is a continuous layer of layered, dry to moist, very stiff to hard, generally high plasticity varved clayey silt and silty clay (AASHTO: A-6 to A-7-5 to A-7-6, USCS: MH, CH, and MH-CH). This lower clay layer was observed in all of the borings, ranging in thickness from about 32 ft upslope from Route 191 to about 20 ft at the stability berm to about 50 ft at the base of the slope near the Clyde River. Zones of disturbance and slickensides were noted throughout. Folded varves and reworked zones were observed in the sonic borings at the approximate depth of the failure surface identified in the historic inclinometers. Varve thickness ranges from about 0.1 inches up to 2 inches. Zones of non-varved clay up to 5 ft thick were also encountered.

Lower Sands and Gravels: Beneath the lower clay a layer of brown and gray, medium dense to very dense, fine to coarse sand, with some to little gravel and little silt (AASHTO: A-1-b to A-3, USCS: GM to SM) was encountered in all of the boring locations. Thickness of this layer ranges from 20 to 30 ft. Occasional cobbles were noted throughout.

Lower Silts and Weathered Bedrock: Directly above the bedrock surface a layer of dark brown, moist to wet, dense, silts and silty fine sands (AASHTO: A-4, USCS: ML) was encountered. The thickness of this layer is fairly consistent at 10 to 15 ft. Fractured and weathered bedrock was encountered along the bottom of the deposit immediately above intact bedrock.

4.1.2 Bedrock Conditions Bedrock was cored at the sonic borings to verify the top elevation of unweathered bedrock and diamond-

coring using an NQ sized rock core barrel was completed in boring B-305b at the edge of Route 191. The

core recovered was a medium dark to dark grey, very fine grained, fresh, strong to very strong, weakly

foliated to massive, strongly calcareous, muscovite-quartz metalimestone, with trace pyrite. Discontinuities

are mostly parallel with foliation, dipping 10-20 degrees, planar, rough, spaced 4-26 centimeters (cm; very

close to moderately spaced) with rare coatings of iron oxide. This lithology is consistent with the Waits

River formation.

Saprolite was noted in a VTrans core log for boring B-205 (115 to 141.6 ft [26.6 ft thick]). Saprolite, often

called residual soil, is defined as soft, thoroughly decomposed rock formed in place by chemical weathering,

and is characterized by preservation of structures present in the unweathered rock (e.g., bedding and



foliation). The lower silt and weathered bedrock layer is generally consistent with the presence of saprolite.

As saprolite is generally clay rich, groundwater flow is generally restricted in saprolites.

4.1.3 Groundwater Conditions Groundwater conditions at the site were evaluated based on an interpretation of piezometer data from

boreholes located across the site and with a series of pumping tests performed from the three PTW wells

constructed on the stability berm. The results of the pumping tests and conclusions about the site

hydrogeologic properties and system related to extraction well remedial design are presented in Golder’s

pumping test report9.

Groundwater conditions as measured by piezometers indicate that groundwater appears to react quickly to

heavy rainfall events although the rise in pore pressure is slight, generally less than 1-2 ft. The piezometer

data indicate there is a noticeable downward vertical gradient in water pressures on the uphill side of the

abandoned power canal bisecting the site, and an upward vertical gradient in water pressures at and below

(north of) the canal. Artesian pressures, where the measured piezometric head elevation is above the

ground surface, range from about 10 ft at B-311 to about 20 ft at B-313 for the deep piezometers and about

0.5 ft for the shallow piezometer at B-311. The shallow piezometer at B-313 appears to react to changes

in the elevation of the Clyde River. B-316 adjacent to the power canal also shows a very strong upward

vertical gradient where the deep piezometer has a piezometric head elevation about 6 ft bgs.

4.2 Conditions at Proposed Access Road Conditions at the proposed access road on the east end of the Route 191 embankment are generally similar

to conditions encountered beneath the embankment fill in earlier investigations. Although the borings were

of limited depth (52 ft in B-401 and 32 ft in B-402 and B-403), embankment fill, upper silts and sands, upper

silts and clays, and middle silts and sands were all encountered. The upper silts and sand, upper silts and

clays, and middle silts and sands were largely as described in Section 4.1. The upper silt and clay layer

was approximately 5 ft thick and at a higher elevation than in the earlier borings, indicating that it and the

upper silts and sand layer above it rise and thin out moving towards the east.

The upper 29 ft of material encountered in in B-401 and the upper 12 ft in B-402 was embankment fill

material from the original embankment construction. This material tended to have a higher silt component

than the material tested elsewhere in the embankment (see the earlier VTrans investigations and Golder’s

2013 investigation). Similar to the earlier investigations, the fill material was observed to be reworked native

material. The fill is generally described as gray brown to tan gray, moist to wet, loose to dense, silt to silty

fine to coarse sand, little to trace gravel (AASHTO: A-1-b to A-4, USCS: SM to ML). Boring B-401 had a

zone from 20 to 29 ft bgs that was looser than embankment fill material elsewhere, and had a higher silt

content, likely due to variations in the material used to construct the embankment rather than deliberate

placement.



DCP test results correlated to STP N-values (summarized in Table 3) were factored into an estimate of the

friction angle of the surficial soil below the vegetated mat to 3 ft bgs. The overall average STP N-value

calculated from the DCP testing in the area of the proposed access road (DCP tests DCP-1 through DCP-

13) after adjusting for obstructions encountered during the testing was equal to 24. Based on this N-value

and SPT N-values from borings B-402 and B-403, a friction angle of 35 degrees was estimated and used

in Golder’s evaluation of the access road impacts on slope stability summarized in section 6.6.

In comparison, the overall average N-value calculated from the DCP test results in the area of the proposed

upper embankment slope stabilization area (DCP-14 through DCP-20) after adjusting for obstructions

encountered during the testing was equal to 14.

Groundwater encountered in boring B-401 measured immediately after well construction was 10.7 ft bgs.

The groundwater measured at the end of drilling in borings B-402 and B-403 was 0.9 ft and 1.3 ft,

respectively.



5.0 GROUNDWATER MODELING The conceptual hydrogeologic model of the Newport Landslide Site is controlled by recharge areas, varying

lithologies and regional discharge. In general, percolating precipitation becomes groundwater in recharge

areas south and southwest of the site and moves northeast, discharging to the Clyde River and the

abandoned power canal through the glacial sediments. The bulk of the groundwater movement occurs

predominantly in the open, interconnected pores within the coarser glacial sediments, which dip gently to

the northeast. Some groundwater recharges the underlying bedrock from the glacial sediments in the

recharge areas, which also moves to the northeast. The groundwater within the bedrock flows through a

secondary porosity developed from the joints, fractures and foliation plane openings present within the

bedrock. Primary porosity is likely not an important factor in groundwater flow in bedrock as the spaces

between primary grains have been filled with precipitated cement through the processes of diagenesis and

low-grade metamorphism. Precipitation is also collected and stored by embankment fills associated with

construction of Route 191.

Golder compiled a computer numerical groundwater model based on the conceptual hydrogeologic model

briefly described above. The numerical groundwater model was used to evaluate the following:

The overall groundwater flow directions, and the importance of the coarser grained sediments in controlling groundwater flow;

The relationship between horizontal and vertical groundwater gradients;

The effect of relieving groundwater pressure at depth;

Alternative landslide stabilization approaches using groundwater withdrawal; and

The potential effects of the selected stabilization plan on nearby, upgradient water supply wells.

Golder initially constructed the numerical groundwater model using three-dimensional geologic surface

kriging software (EVS/MVS11), employing the geologic and geotechnical boring log data, as well as surficial

geologic mapping data, to develop a model using eight (8) separate, distinct hydrogeologic layers. The

groundwater model was then developed using the three-dimensional model MODFLOW12,13. Using

observed field hydrogeologic, surface hydrology, remote instrumentation, geotechnical laboratory, and

precipitation data, we assigned model characteristics to mimic observed conditions. These characteristics

included estimates of hydraulic conductivity, anisotropy, and boundary condition values to simulate

horizontal and vertical groundwater flow, and water balance input and output. Golder then conducted a

calibration exercise to refine these values to obtain a reasonable match between observed and simulated

11 C Tech Development Corporation (2008). EVS/MVS Mining Visualization System, Vers. 9.6. 12 McDonald, M.G., and Harbaugh, A.W. (1988). A Modular Three-Dimensional Finite-Difference Groundwater Flow Model. Techniques of Water-Resources Investigations of the United States Geological Survey, Book 6, Chapter A1, U.S. Government Printing Office, Washington D.C. 13 Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G. (2000). MODFLOW-2000, The U.S. Geological Survey Modular Ground-Water Model - User guide to modularization concepts and the ground-water flow process: U.S. Geological Survey Open-File Report 00-92, 121 p.

http://pubs.er.usgs.gov/usgspubs/ofr/ofr200092

http://pubs.er.usgs.gov/usgspubs/ofr/ofr200092



conditions to compile a steady-state model for use in developing alternative extraction well stabilization

approaches. This included mimicking the results of a transient variant of the model to the observations of

the 24-hour pumping test at PTWa to further calibrate the model.

Following calibration, Golder then evaluated four groundwater extraction scenarios, including passive

pressure relief wells near the Clyde River, and three active groundwater extraction wells placed at varying

locations between the Clyde River and Route 191. For each scenario, the potential increase in the factor-

of-safety against further sliding was analyzed by taking the reduced groundwater pressures from the

groundwater model runs and incorporating them into global slope stability models. Due to access, right-of-

way and permitting issues, VTrans selected the existing stability berm for the location of three active

groundwater extraction wells for the final design. Evaluation of this scenario indicates that it likely will not

reduce the reported static groundwater elevations of water supply wells with open intervals in bedrock

located upgradient of the landslide site.

Appendix C contains a detailed description of the numerical groundwater model compilation, results, and

extraction system scenarios.



6.0 FINAL DESIGN EVALUATIONS 6.1 General From site observations made in 20122 and the 2013 field program6, two different slope failure mechanisms

of concern were identified: 1) the deep-seated slide mass extending up to 120 ft deep with an overall slope

length of roughly 600 ft that is causing the most visible impact to the stability of Route 191; and 2), a shallow

upper slope slide mass within the embankment materials adjacent to Route 191. Final design development

for the deep-seated and shallow upper slides were based on the results of global stability analyses

discussed in detail in Golder’s 20157 letter report.

The selected design for the deep-seated slide stabilization is described as Alternative D in the 20157 letter

report, and includes the installation of three active groundwater extraction wells in the area of the stability

berm shown on Figure 3. The wells are planned to extend 146 to 180 ft bgs. The calculated global stability

factor of safety for the deep-seated slide after implementation of the groundwater extraction wells varies

from 1.27 to 1.42 for three slope cross sections (Section A-A’ shown on Figure 2 and two parallel sections

150 ft right and left of Section A-A’). The shape of the calculated potential failure surface corresponding to

the stability analysis for Section A-A’ is shown on Figure 7 of the 20157 letter report.

The selected design for the shallow upper embankment slope area is described as Alternative US-2 in the

20157 letter report. The design includes adding structural fill to flatten the slope to 2.1H:1V in the area

shown on Figure 3, and adding an 8 foot deep toe drain at the area shown on Figure 3 to lower the

groundwater level at the toe of the upper slope. The calculated global factor of safety for the upper slope

mitigation design is 1.31 as shown on Figure 13 of the 20157 letter report.

The groundwater extraction system stabilization design for the deep-seated slide mass is discussed in

Section 6.2 and the design recommendations for the shallow upper embankment slide is discussed in

Section 6.3. Additional stabilization recommendations beneficial for both the deep and shallow slide

mechanisms include headscarp sealing (discussed in Section 6.4), and a cutoff trench drain upgradient of

the slide across Route 191 (discussed in Section 6.5). Section 6.6 summarizes our evaluation of the

stability of the permanent access road planned to connect Route 191 to the extraction well and control

building area on the stability berm.

6.2 Deep-Seated Slide Stabilization – Groundwater Extraction System The Route 191 embankment is underlain by several glaciolacustrine sand/gravel/silt/clay units and overlies

embankment and fill materials placed for construction and slope stabilization. Groundwater is present in

these sediments under confining pressures. Previous VTrans field studies indicate that depressurizing

artesian conditions in the lower portion of the slide mass reduced the rate of slide mass movement. Golder’s

geotechnical and hydrogeological modeling confirmed the results of these studies2,6,7. The selected

stabilization design for the deep-seated slide uses extraction wells to reduce excess groundwater pressures



acting on the slide plane. Design included refinement of the site geologic model; creation of a groundwater

3D numerical model using MODFLOW software; developing a slope stability model for the slide mass using

stratigraphy identified in the 2013 investigation and pore water pressure inputs from MODFLOW, and

calibration analyses to assess the behavior of the integrated model inputs. The combined groundwater and

stability models were then used to evaluate the mitigation design.

The selected mitigation design includes installation of three new groundwater extraction wells at the

locations shown on Figure 3, referred to as AW-1, AW-2, and AW-3 within the Lower Sand and Gravel unit.

This stratum exists between 120 and 175 ft bgs along the stability berm. The design incorporates existing

pumping test well PTWa, installed as part of the 2013 field investigation, as a backup extraction well. A

stratigraphic cross section illustrating the depth and location of the extraction wells is provided in Figure 5

below. In 2013, Golder completed a pumping test of well PTWa, near the proposed location of AW-1 and

AW-2. PTWa was drilled using sonic drilling techniques and was completed as a 4-inch diameter polyvinyl

chloride (PVC) well with a 5-ft screen interval between 135 and 140 ft bgs. For the pumping test, the well

was pumped for 24 hours at a constant rate of 6 gallons per minute (gpm). The static and pumping water

levels were 38.9 and 126.4 ft bgs, respectively resulting in a drawdown of 87.5 ft and a well specific capacity

of 0.07 gpm/ft. Based on the hydrogeologic testing, the estimated average transmissivity for the Lower

Sand and Gravel unit is 42.8 ft2/day and the average hydraulic conductivity is 1.65 ft/day based on a

thickness of 26 ft. The average calculated (geometric mean) storage coefficient is 4.5E-049.

Figure 5 - Stratigraphic cross section showing the extraction wells screened in the Lower

Sand and Gravel unit.



Water quality can greatly affect the long-term operation and maintenance costs of a groundwater pumping

system due to precipitation of dissolved minerals and the formation of iron-precipitating bacteria, which can

plug the gravel pack, the well screen, pump intake screens, the pump column pipe, and associated

distribution piping. Mineral precipitation and iron-precipitating bacteria were observed at the horizontal

drain outlets in 2012 (see Section 6.3.3). Water quality sampling results of the Lower Sand and Gravel unit

indicate that the groundwater contains concentrations of dissolved iron (up to 3.1 milligrams per liter [mg/L]),

total iron (up to 18 mg/L), total manganese (up to 0.88 mg/L), and total dissolved solids in excess of 500

mg/L10. These concentrations are considered highly elevated for drinking water standards but do not

necessarily indicate the potential for well plugging. The fine-grained matrix of the Lower Sand and Gravel

unit may cause entrainment of fine silt and clay particles, which could plug the gravel pack and well screen,

or ultimately plug the pump intake and column pipe. Golder's design includes several features to reduce

the potential for and frequency of plugging, but periodic well redevelopment is expected to be required.

Design features to reduce plugging include using a 6 inch diameter well instead of a 4 inch well. The larger

diameter well provides for lower flow velocity through the filter pack that reduces turbulence and results in

less fine grained particles being carried towards the wells and potentially plugging the filter pack. In

addition, the well screen will be a stainless steel wedge wire screen which is designed to resist corrosion

and to hold the filter pack material back while maximizing the percent open area of the screen, further

reducing screen entrance velocities and potential plugging. The design also specifies a variable-frequency

pump which can maintain constant flow velocity into the well as opposed to cyclic pumping (where a fixed

flow rate pump turns on and off in response to water elevation), thus reducing the potential for over pumping

which can increase plugging from sediment transport into the gravel pack or well screen. Lastly, the design

includes placing the pump's intake above the screen to reduce the potential to draw the water level down

too low which could expose the screen to air which, in turn, could generate biological growth (e.g. iron

fouling).

The well redevelopment process itself involves pulling the pump out of the well, wire brushing the pump

screen, and cleaning the filter pack and well screen. The cleaning process will depend on what the nature

of the plugging is found to be and typically includes surge block development and airlift pumping

(mechanically pushing water in and out of the well screen then removing particulates via pumping).

Depending on conditions observed during cleaning, additional development techniques employed may

include high pressure jetting, impulse generation using nitrogen bursts (i.e., Hydropuls®), and possibly

chemical (biocide or acid) development techniques (if biofouling is observed).

The frequency of required well redevelopment is difficult to predict. Golder’s experience in public water

supply wells suggests it can range from 3 to 10 years in shallow gravel-packed wells, and from 10 to 30

years in deep sand aquifers. Contaminant recovery well systems typically require redevelopment every 1



to 3 years. For the Newport well system, Golder estimates a required redevelopment frequency between

3 to 10 years. The longer frequency is possible considering that steady water levels should prevail using

the variable-frequency pump, the wells are moderately deep, and the pumping water levels will remain

above the well screen.

6.2.1 Extraction Well Design Based on the groundwater modeling results and stability analyses, a design pumping rate per well of 6.0

gpm is required to maintain sufficient depressurization in the Lower Sands and Gravels to reduce movement

of the landslide, provide a satisfactory global stability factor of safety, and provide redundancy and resiliency

in the pumping system. Stability analyses indicate all three wells operating at a lower steady state flow of

4.5 gpm results in a calculated FS of 1.32 for the deep-seated slide mass. All three wells pumping at 6.0

gpm results in a calculated FS of 1.40. If one well shuts down leaving two wells pumping at 6.0 gpm, the

calculated FS is 1.25. Analyses also indicate that if two wells shut down leaving the last well pumping at

6.0 gpm, the calculated FS reduces to 1.12. Considering these scenarios, Golder concluded that a design

pumping rate of 6.0 gpm was appropriate along with a minimum long-term pumping rate of 4.5 gpm.

It is important that the extraction wells be designed to operate as efficiently as possible to sustain these

pumping rates. Well efficiency is the measure of the theoretical drawdown in a well from laminar-flow losses

divided by the measured total drawdown in the well, which includes head losses from turbulent flow

generated as groundwater enters the well screen and gravel pack. The available drawdown in the well may

be a limiting factor on the pumping rates that can be achieved and maintained if the wells have an initially

low efficiency or if the efficiency deteriorates over time. Poorly designed and constructed wells and wells

that become plugged over time will typically generate greater turbulent head losses and therefore will have

a lower well efficiency. For example, the well efficiency of PTWa at the end of the 24-hour test is estimated

to have been 34%. This is derived by dividing the calculated theoretical drawdown of 30 ft by the measured

drawdown within the well at the end of the test of 87.5 ft. The theoretical drawdown was estimated using

the Theis non-equilibrium equation and the parameters derived from the 2013 pumping test.

During the 2013 test, the pumping water level in the PTWa drew down to within less than 10 ft above the

top of the screen, suggesting that this pumping rate in PTWa is not sustainable primarily due to the low

efficiency of the well. Therefore, it is important that the new extraction wells be drilled, constructed, and

developed in a manner to produce highly efficient wells. In addition, the wells should be placed on a regular

pump and well rehabilitation schedule to maintain high well and system efficiencies so that the minimum

pumping rate of 4.5 gpm from all three proposed wells can be achieved. Table 5 below provides a summary

of final design well construction and projected pumping water levels under anticipated well efficiency and

well interference conditions.



Table 5. Well Construction Details and Projected Pumping Water Levels

Well AW-1 Well AW-2 Well AW-3 Well PTWa Ground Elevation (ft amsl) 782 793 802 792 Well Depth1 (ft bgs) 146 154 180 171 Well Diameter (in) 6 6 6 4 Water Table2 (ft bgs) 22 33 42 32 Top of Screen (ft bgs) 121 129 155 135 Bottom of Screen (ft bgs) 141 149 175 140 Pump Intake3 (ft bgs) 111 119 145 125 Available Drawdown4 (ft) 89 86 103 93 Predicted Drawdown5 (ft) 42 42 42 42 Predicted Well Losses6 (ft) 13 13 13 13 Predicted Interference7 (ft) 21 24 21 25 Total Projected Drawdown (ft) 76 79 76 80 Projected Water Level above Pump8 (ft) 13 7 27 13

Notes: Elevation given in feet above mean sea level (ft amsl); depth is given in feet below ground surface (ft bgs)

1. Well depth is 5 ft below the bottom of the screen to allow for a sump to collect sediment. 2. Water table elevation is assumed to be approximately 760 ft amsl based on PTWa hydrogeologic testing. 3. The pump intake is placed 10 ft above the top of the well screen to improve long-term well operations. 4. Available drawdown is calculated by subtracting the depth to water from the pump intake depth. 5. The predicted drawdown is estimated using the Theis non-equilibrium equation and assuming a transmissivity

of 42.8 ft2/day, a storage coefficient of 4.5E-04, a continuous pumping rate of 6 gpm, and a pumping duration of one year.

6. The predicted well losses assume a well efficiency of 70% and are estimated by multiplying 42 ft by 0.30. 7. The predicted drawdown interference is estimated using the Theis non-equilibrium equation and the distances

between each well. For PTWa, the estimate assumes that well AW-2 is off. 8. The projected water level above the pump is calculated by subtracting the projected drawdown from the

available drawdown.

There is some uncertainty related to the desired screen interval for the design of extraction well AW-3 due

to the lack of subsurface information in the area of this well as noted in the stratigraphic cross section shown

on Figure 5. Boring B-202 (drilled by VTrans in 2008) is the only boring previously drilled in the area of

proposed well AW-3 and it was terminated at El. 662, above the Lower Sand and Gravel strata where the

AW-3 well screen is proposed to be located. Golder recommends advancing an additional boring in the

vicinity of AW-3 to further characterize the soil strata below El 662 and confirm the planned well design is

appropriate for this location. Golder also believes the addition of a piezometer at this location would benefit

our understanding of the deep well system performance in this site area after installation. The findings from

the additional boring and conclusions regarding the well AW-3 design would be summarized in a letter

report.



6.2.2 Well Screen Filter Pack As part of the 2013 investigation, grain size analyses were completed for five (5) formation samples from

monitoring wells B-204 (130-131 ft bgs, 135-136.5 ft bgs, and 140-141 ft bgs), B-305 (165-170.5 ft bgs),

and B-306 (140-152 ft bgs) following AASHTO Standards R58 and T882. These data were used to help

select the appropriate size of the screen openings and the surrounding filter sand pack. These sieve

samples were collected from the Lower Sand and Gravel unit.

Analyses indicate that the formation is comprised primarily of silt and clay size particles. Most of the

samples with the exception of B-204 (130-131 ft bgs) consisted primarily of silt and clay with 60 to 92

percent of the samples finer than the No. 200 sieve (0.075 mm) and a median (50% passing) grain size of

0.04 mm. B-204 (130-131 ft bgs) consists primarily of sand with a median particle size of 1.16 mm (coarse

sand) and only 8% silt passing the 200 sieve. The grain-size distribution data and graphs of cumulative

percent retained versus grain size for the samples used for extraction well design are provided in Appendix

B-2. Typically, a sand filter for a well screen is sized to be 4 to 6 times the 30% and 50% finer particle size

(D30 and D50) of the surrounding formation. In this case, the filter pack would be too fine-grained and

restrictive to the flow of water into the well if it were based on the D30 silt/clay particle size of most of the

samples. If an overly fine grained filter pack is used the resulting decrease in well yield could jeopardize

the groundwater pressure reduction objectives of the deep well extraction system. Therefore, we have

based our filter pack design on the coarsest sample from B-204, i.e. - 130-131 ft bgs. To help form a natural

filter within the native formation soils surrounding the well screen we recommend that the extraction wells

be aggressively developed with pumping and surging during installation. With this procedure we expect

that the amount of any fine grained silt or clay sized particles that penetrate through the filter pack will be

minor and should not affect pump performance.

Golder used standard well filter pack design standards to select the filter pack and screen size 14,15. Criteria

for standard filter pack design includes evaluation of the soil sample particle gradation, selection of the D60,

D30 and D10 particle sizes, selection of the filter/gravel pack ratio (GPR) based on the uniformity coefficient

(Cu), selection of the filter pack particle size; and selection of the well screen slot size. The procedure

includes the following:

1) Plot the grain size distribution of the formation materials on a percent retained basis.

2) Establish the D60, D50 and D10 passing grain size values of the formation, and the D10 passing grain size value for the filter pack.

3) Establish the uniformity coefficient (Cu = D60/D10 [dim]) of the formation.

4) Choose a gravel pack ratio (GPR) based on Cu (GPR=4 if Cu<3; GPR=5 if Cu is 4-5; and GPR=6 if Cu>6).

14 Williams, E.B., 1981. Fundamental Concepts of Well Design. Ground Water, Vol. 19, No. 5, September-October, p. 527-542. 15 Driscoll, F.G., 1986. Groundwater and Wells (2nd ed.), Johnson Filtration Systems, Inc., St. Paul, Minnesota, 1089 p.



5) Choose gravel pack based on the formation D30, and D50 x GPR to establish the D30 of the filter pack.

6) Choose a uniform filter pack gradation that passes through the established D30 filter pack point, and has a Cu < 2, preferably around 1.5.

7) Select screen slot size to retain 90 – 95% of the filter pack, corresponding to the D10 – D5 passing grain size.

8) Confirm approach, entrance and uphole velocities meet standard well design criteria.

Based on the B-204 130-131 ft bgs sample, the filter pack should have a D30 grain size of approximately

0.64 mm assuming a GPR of 6. This equates approximately to a #0 filter sand manufactured by U.S. Silica

Filpro®. A screen with 0.020-inch slot openings was selected to retain 95-100% of the Filpro #0 filter pack

as shown below in Figure 6. The other four samples of formation material are considered too fine grained

for conventional well design parameters to be applied effectively for this system. Accordingly, the final filter

pack design is based on Golder’s best judgement considering our interpretation of the subsurface

conditions and the objectives of the well system.

Figure 6 - Selection of Filter Pack and Well Screen Slot Size

6.2.3 Entrance, Approach and Uphole Velocity Estimates Golder recommends that high-efficiency, 6-inch diameter stainless steel (Type 304), continuous wire-

wrapped water well screens be used for the extraction wells. The stainless steel provides greater long-

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1

Cum

ulat

ive

% R

etai

ned

Grain Size (inches)

GRAIN SIZE DISTRIBUTION FOR US Silica FilPro# 00 FilPro #0 FilPro # 1 FilPro# 2 FilPro # 3 FilPro B-204 130-131', GPR=6B-204 130-131'

Choose 20 Slot Screen

Choose Filpro #0



term resistance to electrochemical corrosion. These well screens provide a large percentage of open area

decreasing entrance velocities. The large diameter of the screen and surrounding filter pack decreases

approach and entrance velocities of radial groundwater flow towards the gravel pack and well screen.

Lower approach and entrance velocities reduces turbulent flow losses and will reduce the potential plugging

of the filter pack and well screen from mineral precipitation, iron bacteria encrustation, and entrainment of

fine silt and clay particles from the surrounding formation. These well design measures will increase the

efficiency of the well and will decrease long-term well maintenance and rehabilitation costs. The 6-inch

well casing diameter also accommodates a 4-inch diameter submersible pumps.

The calculated open area of the screen with 0.020-inch slot openings is 40 square inches per linear foot

(in2/ft), equating to a percent open area of 16%. The average entrance velocity of water moving into the

well screen should not exceed 0.1 feet per second (ft/sec). At this velocity, the amount of turbulent flow

and friction losses through the screen opening will be negligible and the rates of sediment plugging, mineral

incrustation and corrosion will be minimal. The calculated entrance velocity for these wells at the design

pumping rate of 6 gpm is 0.0024 ft/sec. The well should also be designed to limit the approach velocity into

the surrounding gravel pack to 0.02 ft/sec. The calculated approach velocity in this case is 0.0003 ft/sec.

Lastly, the uphole velocity inside the screen and well casing should be less than 5 ft/sec. In this case, the

estimated uphole velocity is 0.07 ft/sec. Well design criteria are summarized in Table 6.

Table 6. Well Screen Design Criteria

Well Design Parameter Design Limit Actual

Screen Open Area - 40 in2/ft Screen Open Area - 16% Screen Transmitting Capacity - 12.45 gpm/ft Entrance Velocity 0.1 ft/sec 0.0024 ft/sec Approach Velocity 0.02 ft/sec 0.0003 ft/sec Uphole Velocity 5 ft/sec 0.07 ft/sec

6.2.4 Pump and Pump Controls The pump intake will be set at a maximum depth of 10 feet above the top of the well screen. This will

reduce the potential introduction of oxygen into the well screen which may promote bacteria growth and

formation of iron bacteria, and will reduce turbulent flow and degassing of carbon dioxide which may

promote mineralization including the precipitation of calcium carbonate and iron oxyhydroxides. For the

purpose of conservatively estimating the total dynamic head (TDH) for each well, the depth of pump intake

is used to calculate friction losses in the pump column pipe and the vertical head of the system. Friction

losses are relatively minimal within high-density polyethylene (HDPE) pipe and pipeline components (e.g.,

flow meter, check valves, gate valves, pipe elbows, etc.) primarily due to the low design flow from the wells.



However, friction losses are excessive when it is assumed that 50% of the initially evaluated 1.25-inch

diameter HDPE pump column pipe and the 2-inch diameter HDPE distribution pipeline are plugged by iron

bacteria and mineral encrustation. For this reason, the pipeline diameters were increased to 2-inch for the

column pipe and 3-inch for the distribution pipe. Well AW-3 has the greatest TDH primarily due to its deeper

screen and pump intake setting. The estimated TDH for AW-3 is 149 feet at a maximum pumping rate of

10 gpm. If it is assumed that the column pipe and pipeline are 50% blocked, then the maximum design

TDH is 174 feet. Table 7 summarizes the static and dynamic head calculations for all four wells. TDH

worksheets are provided as Appendix D.

Table 7. Estimated Total Dynamic Head (TDH) and Pump Design Parameters

AW-1 AW-2 AW-3 PTWa Design

Maximum Friction Losses (feet) 2 2 1 2 28 Vertical Head (feet) 134 131 148 138 146 TDH (feet) 136 133 149 140 174 Pumping Rate (gpm) 10 10 10 10 10 Minimum Horsepower (hp) 0.5 0.5 0.6 0.5 0.7

Based on these head and flow requirements, a Goulds Model 10GS07 electric submersible pump with a

0.75 horsepower motor was selected for the extraction wells. This pump has seven stages and is rated at

13.4 gpm at a TDH of 180 feet. The actual flow from the well will depend on the level of water in the well

and friction losses throughout the distribution system. The manufacturer’s pump curve and performance

specifications are provided in Appendix E.

The pump will be controlled using Goulds’ Smart Pump Technology system, which uses a variable speed

drive and pressure transducer to maintain a relatively constant water level in each well. This control system

will protect the pump and the well from over pumping while allowing pumping rates to be automatically

adjusted to maintain a minimum water level in the well. The controls will be housed in an onsite concrete

building as shown on Figure 3. All piping will remain below the 72-inch frost depth. Wireless communication

will allow remote monitoring on a web-based application.

Golder’s final extraction system design components are included in Sheets 61 – 65 of Stantec’s preliminary

plans8. These include:

Extracted groundwater piping plan and profile

Extraction well details

Extraction system trench and flow meter vault details

Pump house building plan, elevations and details

Piping and instrumentation plan



A draft Special Provision for the Groundwater Deep Well Pumping System materials, installation,

submittals, and method of measurement is included in Appendix F.

6.3 Upper Embankment Slope Stabilization The stability of upper embankment slope areas between Stations 116+00 and 119+00 (see Figure 2) was

assessed using soil profiles, soil strength parameters and groundwater conditions developed based on the

information presented in our 20146 report and confirmed by the DCP testing conducted in 2017. Where the

analyses indicated marginal stability conditions, analyses of stabilization alternatives were performed to

provide the most efficient methods for stabilization. A detailed summary of our stabilization alternatives

analyses were summarized in our 20157 letter report. The chosen stabilization method was slope flattening

and improved drainage and is described as Alternative US-2 in the report. The area of stabilization is

shown on Figure 3 and is shown on sheets 6, 29, 38, and 90 to 93 of Stantec’s preliminary plans8.

6.3.1 Slope Flattening The selected stabilization alternative includes flattening the embankment slope above the stability berm

with a controlled structural fill. The western part of the embankment appears to be over steepened relative

to the rest of the embankment. Existing slopes in this western slope area vary between about 1.4H:1V to

1.9H:1V. Within the area planned for upper slope stabilization shown on Figure 3 additional engineered fill

is planned to be placed to flatten the final grade to a 2.1H:1V slope. The existing topsoil should be stripped

prior to regrading activities and the new fill benched into the existing slope. The new fill material should

conform to the gradation requirements outlined in VTrans specification 704.18 (i.e., the electrochemical

requirements are not necessary for this application), Select Backfill for Mechanically Stabilized Earth (MSE)

Walls, and be compacted to 95 percent of modified proctor as detailed in 900.608 Special Provision (Select

Backfill) a copy of which is provided in Appendix F. Refer to “Upper Slope Mitigation Profile” detail on sheet

6 of Stantec’s preliminary plans8. The slope flattening should be constructed after the installation of the toe

drain.

6.3.2 Toe Drain In conjunction with slope flattening, the final design for upper slope stabilization includes the installation of

a toe drain along the stability berm. The existing western portion of the stability berm below the upper slope

slide is overgrown with vegetation indicating a shallow water table. During Golder’s previous site

investigations, this area has also been observed to be wetter than other areas of the stability berm. The

elevated water table in this area is believed to partially contribute to the current slide in the upper slope.

The intent of the toe trench drain is to lower the groundwater table at the toe of slope and increase the

stability of the upper slope. The proposed toe drain should include a 6 inch diameter HDPE underdrain

pipe founded approximately 8 ft below the existing stability berm ground surface at the toe of the slope, and

installed at the grades shown on sheet 38 of Stantec’s preliminary plans8 to allow for the drain to daylight.



The toe drain trench should be lined with geotextile for underdrain trench lining and backfilled with peastone

or crushed stone conforming to VTrans specification 704.16, Drainage Aggregate to promote drainage

through the trench, as shown in the “Toe Drain Detail” on sheet 68. Since the toe drain will be buried in the

new embankment fill for the flatted upper slope, it should be installed prior to the slope fill.

Excavation of a trench across the toe of an already unstable slope could cause further slope instability.

Methods to prevent the movement of the slope into the open trench will be required of the contractor.

Temporary shoring that is in intimate contact with the trench walls, such as a slide-rail type shoring system,

could be acceptable while the use of standard trench boxes that are narrower than the excavated trench

should not be allowed as they will not prevent slope movement. Care will also be required to limit the depth

of trench excavation support systems to the bottom of the toe drain trench elevation to avoid damaging

underlying existing horizontal drains as discussed in Section 6.3.3. We recommend that the length of open

and unsupported toe drain trench be limited to 25 ft during toe drain excavation and installation. This will

require the contractor to work in short segments or work continuously with excavation and backfilling

occurring simultaneously.

6.3.3 Existing Drainage Systems in Stability Berm Area Two previously installed drainage systems are present in the stability berm area as shown on Figure 2 and

may be encountered during the planned mitigation construction. The existing drains include: 1) a series of

parallel 2-inch PVC horizontal drains installed in a northeasterly orientation; and 2) 6 inch corrugated HDPE

underdrains installed in an east-west orientation along nearly the full length of the stability berm. Both

drainage system are currently active and providing a positive effect on embankment stability, and should

be repaired in place if encountered during construction.

The horizontal drains were initially installed in 1971 shortly after construction of the embankment fill and

were extended in 1991 during the construction of the stability berm. These drains run from under the upper

slope and daylight at the base of the stability berm and are constructed out of solid 2-inch PVC pipe. The

approximate locations of these drains are shown on sheets 28 and 29 of Stantec’s preliminary plans8, but

construction records of these drains are approximate and may vary from the locations shown in the design

drawings. The proposed orientation of the toe drain is located across (transverse to) the alignment of the

horizontal drains. Based on our interpretation of the drain elevations shown in Figure 7, we anticipate the

bottom of the toe drain trench will be above the horizontal drains, but the interpreted separation distance is

small, less than 24 inches at horizontal drain numbers HD-3 and HD-13. Since the actual horizontal drain

locations and elevations are uncertain the contractor should take extra caution when excavating the toe

drain trench. Should any horizontal drains be intercepted during construction of the toe drain, the drain

should be repaired using like material to maintain drainage and serviceability of the drain through the

original outlet.



The 6” corrugated HDPE underdrains shown on Figure 2 were installed with the stability berm as shown on

sheets 9 and 11 in the 1991 construction plans16. While these plans show the approximate horizontal

locations of these drains, no information is available regarding the drain elevations. Construction of the

proposed toe drain and/or the extraction well discharge header pipe may intercept one or two of these

existing underdrains. Flushing basins for the drain that outlets in the center of the berm at approximately

Station 116+25 are visible on both ends of the stability berm. The flushing basin on the west end is

approximately at Station 119+00, 100 ft right. If this drain is intercepted it should be repaired using like

materials such that it maintains drainage. If drainage is unable to be maintained due to the location of the

new toe drain, the existing drain should be cut short and a new flushing basing installed. A second

underdrain was installed along the existing slope during construction of the stability berm and outlets at

approximately Station 119+00, 119 ft right. This drain runs approximately parallel to the proposed new toe

drain. If this drain is intercepted during construction it should be repaired using like materials such that

drainage is maintained. If drainage cannot be maintained due to the location of the new trench drain, the

existing drain should be spliced into the new drain using a “Y” fitting. As noted in Section 7.2, a pay item

should be included in the contract documents for drain repair to address these concerns.

6.4 Headscarp Seal Long term displacements of the deep-seated slide mass along the slide plane described in Golder’s 2015

letter report7 provide a potentially preferential pathway for surface runoff and groundwater to travel from the

ground surface and/or surficial soil strata to the Lower Sand and Gravel unit. Reducing the ability for surface

water in the area of the headscarp to replenish the groundwater at depth will increase the efficiency of the

extraction wells at depressurizing the Lower Sand and Gravel unit and improve stability. Additionally, as

noted in the groundwater analysis10, the potential presence of deicing compounds in one of the wells

suggests that surface water may currently be migrating down the failure scarp and entering the Lower Sand

and Gravel unit.

Golder assessed options for sealing the headscarp. The asphalt pavement of the Route 191 roadway seals

the headscarp in the areas where the scarp crosses the road and needs no further treatment. The area

uphill (south) of Route 191 has experienced deformation from the movement of the slide and currently

allows surface water to pond on the headscarp area in several locations. Sealing the headscarp area uphill

of Route 191 with either a layer of low permeability clay or a geomembrane liner material (HDPE or PVC)

were considered. Headscarp areas downhill (north) of Route 191, roughly from Sta. 110+00 to 112+00 are

planned to be regraded and resurfaced as part of the proposed new access road construction. Considering

the regraded final slopes in these areas and related reduced potential for runoff infiltration, as well as the

16 VTrans (1991). Drawings titled “Proposed Improvement, Town of Newport, County of Orleans, VT Route 191 (F.A.P.)”, State of Vermont, Agency of Transportation, Project Derby-Newport F 134-3(17) C/I, May 9, 1991, with edits as record plans, dated April 24, 1992.



drainage improvements planned for the Route 191 roadway reconstruction, we do not believe additional

headscarp sealing in this area is warranted.

The clay seal option has the advantage of lower installation and construction QA/QC cost, however, suitable

clay borrow materials are not available in the Newport region and substantial hauling costs were concluded

to render this option economically impractical. Accordingly, a 30 mil geomembrane liner is recommended

to seal the headscarp south of Route 191, including the area between the edge of pavement and the existing

underdrain located along the south side of the roadway as shown on Figure 3. The intent of lining this area

is to collect and properly discharge rainfall and snowmelt occurring over the headscarp area as well as to

prevent surface water runoff from the roadway from seeping into the headscarp void. We recommend a

high-density polyethylene (HDPE) or polyvinyl chloride (PVC) geomembrane be selected for this

application. HDPE is commonly used for landfill liner and cover systems, and VTrans has experience with

PVC geomembranes for MSE wall applications. The geomembrane should be placed over a 6-inch “lower”

sand cushion to protect it from punctures from deleterious materials in the subgrade soils. A 9-inch “upper”

sand cushion should be placed above the geomembrane to provide protection and a drainage media to

convey surface water infiltration to an underdrain pipe. A minimum of 9 inches of overlying fill and topsoil

should be placed to maintain the geomembrane at least 18 inches below ground surface. A recommended

headscarp seal section and geomembrane tie-in underdrain detail is shown on Figure 8. A Special

Provision for geomembrane and sand cushion materials, installation, QA/QC, submittals and basis of

payment is provided in Appendix F.

During headscarp sealing construction a portion of the existing corrugated metal underdrain in this area will

need to be relocated to the south boundary of the geomembrane liner as shown on Figure 3. The condition

of the existing underdrain pipe and suitability for reuse could be evaluated during construction: however,

as discussed in Section 7.2 we recommend that this entire section of underdrain be replaced with new pipe

due to the age of the existing pipe.

Additional underdrain in the area of the headscarp seal, approximately 10 ft off the edge of pavement and

running parallel to Route 191, is shown on the 1991 stability berm construction plans16.and on Figure 2.

We believe these are 6 inch corrugated HDPE underdrains. If these underdrains are encountered during

construction they should be repaired in place or spliced into the recommended replacement 8-inch

underdrain system using a “Y” fitting. As noted in Section 7.2, a pay item should be included in the contract

documents for drain repair to address these concerns.

6.5 Cutoff Trench Drain Observations made in 2012 and 2013 on site indicate that vegetation growing on the sides of the existing

embankment in the area of the 30-inch culvert is consistent with the presence of shallow groundwater within

the embankment. We assume that groundwater flowing down the roadway alignment to the northwest in



the pavement subbase and subgrade is intercepted by the culvert backfill material from the 1996 culvert

repair and daylights on the slope of the embankment.

To further reduce the amount of groundwater available in the area of the headscarp and embankment slide,

a cutoff trench drain extending across the width of Route 191 should be installed on the east end of the

project in the vicinity of Station 109+00 as shown on Figure 3. The cut-off trench drain should consist of a

6 inch perforated underdrain pipe located in a geotextile lined trench a least 30 inches wide and filled with

Drainage Aggregate meeting the requirements of VTrans 704.16. The underdrain pipe invert should be

located at least 5 ft below the pavement surface of the reconstructed roadway, which should locate the

invert at least 4 in. below the base of the Sand Borrow layer in the planned pavement section shown on

sheet 4 of Stantec’s preliminary plans8. Based on the existing grading, it is anticipated that the cut-off

trench drain pipe should drain towards the southwest and tie into the existing roadside underdrain on the

uphill side of the road.

6.6 Access Road Stability Following discussions with Stantec and a review of the access road alignment proposed in the VTrans

conceptual phase drawings dated August 4, 2016, Golder recommended that the project team consider

alternative access road alignments to reduce the volume of fill being placed on the side slopes of the

existing Route 191 embankment. The project team then proposed a revised access road alignment (shown

on Figure 3) with less fill than presented in the conceptual plan set and Golder proceeded with the

exploration program described in Section 2.2 in support of a slope stability analysis for the revised access

road configuration.

6.6.1 Stability Analysis Global stability was evaluated for transverse sections through the Route 191 embankment at revised

access road stations 53+00 and 54+00 using the computer model Slide17. These stations were selected

as they represent the sections where the construction of the proposed access road will result in the

placement of fill on the existing Route 191 embankment (53+00) and removal of material from the existing

embankment slope (54+00). Subsurface conditions used in the models were interpreted based on the soil

stratigraphy and ground water conditions encountered during our 2017 exploration program and soil

properties corresponding to STP blow counts in the borings, DCP testing and direct shear testing performed

on reconstituted soil samples. Results of the direct shear tests were further tempered with the results of

historic direct shear testing conducted on embankment material in 2013. An analysis of interpreted existing

conditions at these sections indicated the existing Route 191 embankment has a calculated factor of safety

(FS) of about 1.2.

17 Rocscience, Inc. (2017). Slide – 2D Limit Equilibrium Slope Stability and Groundwater Analysis for Rock and Soil, Version 7.024, build date May 4, 2017, Toronto, Ontario, Canada.



Following construction of the proposed access road, the FS at station 53+00 is calculated to be 1.4. This

increase in FS from the existing conditions is the result of fill being placed on the embankment which

provides a stabilizing force helping to prevent sliding. The FS at section 54+00 is not impacted by

construction of the new access road.

Our analysis of the impacts of the access road construction was limited to the Route 191 embankment and

a detailed analysis of the lower stability berm was not conducted due to the lack of detailed soil and ground

water information in that area. However, based on field observations there is no evidence of instability

along the lower stability berm and Golder believes that factors of safety will increase once the improvements

recommended in this report are completed.

Assumed geometries, configurations, subsurface conditions, and stability analyses results are presented

in Appendix G.

6.6.2 Stabilization Provisions Local slope stability in the area of the new access road appears to be improved by the construction of the

access road and the associated addition of fill placed on the embankment slope. The use of the extraction

wells increases the FS of the larger slide to the degree that a minimal amount of additional load at the head

of the slide, such as fill placed for construction of the access road, is acceptable. However, such fill should

be kept to the minimum necessary and no wasting of excavation material in this area should be permitted.



7.0 CONSTRUCTION AND POST-CONSTRUCTION CONSIDERATIONS To ensure the successful construction and implementation of the slope stabilization provisions outlined in

this geotechnical design report, Golder recommends the following construction considerations be

incorporated into the contract documents.

7.1 Deep-Seated Slide Extraction Well Construction Considerations A hydrogeologist should be present full-time during extraction well drilling & installation to

log the holes & well construction, confirm anticipated conditions, select ultimate screen locations/depths, observe pumping tests, and collect water levels.

A water-systems type engineer should be present during the extraction system construction & commissioning to help troubleshoot items, assist the contractor, and make field changes to the design as needed. In our experience, the availability of such an engineer greatly adds to the success of the project.

7.2 Upper Embankment Slope and General Site Construction Considerations New fill material should be placed on embankment side slopes after the slope has been

benched and prepared accordance with VTrans standard drawing B-5.

The final design for upper slope stabilization includes the installation of a toe drain along the stability berm. Construction considerations for the sequencing and bracing of the toe drain excavation are discussed in Section 6.3.2 and should be highlighted in the contract documents.

Additional fill placed onto the stability berm, the embankment slopes, and the area of Route 191 between the headscarps is effectively loading the deep-seated landslide. Stockpiling of material should not be allowed in these areas, and placement of fill greater than the limits shown on the contract documents should also not be allowed.

The contract documents should include a pay item for drain repair to include the repair of existing 2 inch PVC horizontal drains and/or 6 inch corrugated HDPE drains if encountered and damaged during installation of the toe drain for the upper slope stabilization work, the discharge header pipe for the deep extraction well system, or the headscarp seal.

A geotechnical engineer should be present on site to confirm encountered conditions during culvert replacement, underdrain replacement, access road construction, embankment grading, and trenching. Additionally, the geotechnical engineer should be consulted during excavation of the toe drain for any interception and repair of horizontal drains and underdrains.

Due to the age of the existing corrugated metal underdrain pipe and to help limit shallow ground water and surface water infiltration into the ground on the south side of Route 191, Golder recommends the existing underdrain above the head scarp be replaced during this construction project as noted on Figure 3. Additionally, this drain would need to be incorporated into the head scarp seal (Section 6.4) and will be daylighted already during that work.

We recommend the underground telephone line shown at approximate station 111+00 on sheet 177 of 263 of the 1971 as-built plans18 be noted on the new construction drawings with a note stating it has been abandoned to avoid confusion during construction. The

18 State of Vermont, Department of Highways City of Newport, County of Orleans, Interstate Connection (1971). Sheet 177 of 263. Drawing titled “Stage 2 Construction, Derby-Newport F 341-5(4)”.



depth that the line is buried beneath Route 191 is unknown. It is likely that the presence of this utility will not impact any planned work for this project.

7.3 Geotechnical Instrumentation Golder recommends maintaining the existing piezometers to monitor the performance of

the deep groundwater extraction system in addition to the pressure transducers that are being installed with the well pumps. All existing cables, conduits and data loggers should be protected during construction to ensure full functionality at the conclusion of the project. Golder personnel should be on site to verify equipment operation after construction. The full instrumentation system needs to be operable prior to commissioning of the deep extraction wells to log the groundwater response to the initial startup of the well pumps.

We recommend VTrans continue to monitor slope performance with the SAAs installed along the shoulder of Route 191 following the completion of construction. All existing cables, conduits and data loggers should be protected during construction to ensure full functionality at the conclusion of the project.

Monitoring of the two existing IPI arrays (B-306 and B-311) should be terminated and the arrays removed for beneficial reuse by VTrans. Golder should be on site during removal to ensure equipment is properly decommissioned for reuse. Both arrays were installed in standard inclinometer casing so the casings should remain for future monitoring (as needed) using a manual inclinometer probe.

The existing datalogger is located adjacent to B306 and has several sets of communication cables crossing the stability berm and running up the face of the embankment towards B305. At B305, the cables split in multiple directions. Two sets of cables run parallel to Route 191 to B318. One cable runs in a 1.5” PVC electrical conduit buried in a shallow trench under Route 191 towards B302. Two sets of cables run to B305 itself. The Contractor can be allowed to cut and temporarily remove communication cables as needed to allow for construction activities provided it is repaired with proper splices rated for underground work. The conduit running under Route 191 should be retained and the communication cable reinstalled as part of the reconstruction of the subbase.

As outlined in our January 27, 2017 proposal, Golder will be providing an instrumentation plan that is expected to include the continued monitoring of the previously installed vibrating wire piezometers and the two SAAs. The instrumentation plan will also address the impact of the proposed works on the main datalogger and solar panel associated communication wiring to the sensors, including sensors located across VT 191.

7.4 Post-Construction Groundwater Sampling and Analysis We recommend that VTrans perform post-construction groundwater sampling of extraction well discharge

water to document iron and manganese concentrations. In addition to iron and manganese testing, Golder

recommends testing the groundwater for standard field chemistry parameters including temperature, pH,

specific conductance, Eh/redox potential, dissolved oxygen, and salinity. A post-construction groundwater

sampling and analysis plan should be developed outlining a frequency for sampling, sampling requirements,

and groundwater analyses requirements.



8.0 CLOSING AND LIMITATIONS The geotechnical information, test results, design recommendations, and construction considerations

included in this report are provided for the exclusive use of VTrans for development of final landslide

mitigation design for Route 191 in Newport, Vermont. This report was prepared in accordance with

generally accepted soil, foundation engineering and hydrogeologic practices conducted in this geographical

area and under similar financial and time constraints. Golder makes no other warranty, either express or

implied. In the event that any changes in the nature, design, or location of the proposed project are planned,

Golder should be notified to review the appropriateness of our conclusions and recommendations and to

modify the recommendations as appropriate to reflect the changes in design. Further, our analyses, and

recommendations are based in part on the subsurface explorations completed. Golder should be notified

if conditions encountered during construction vary from those described in this report so that we may re-

evaluate, and if necessary, revise the recommendations made in this report.

The professional services provided by Golder for this project included only the geotechnical and

hydrogeologic aspects of the subsurface conditions at this site. The presence or implications of possible

surface and/or subsurface contamination resulting from previous activities or uses of the site and/or

resulting from the introduction onto the site of materials from off-site sources are outside the terms of

reference for this report and have not been investigated or addressed.

TABLES

November 2017 1 of 1 Project No.: 1668897

Date

1969-1971

1971

1973

1974

1971-1976

1986

1989

1991

1996

1996-2011

2006-2009

2006-2011

2011

2012

2013

2013 - current

2014

2015-2016

2016-2017

2017

Stantec preliminary design of VT Route 191 improvements including civil design support for deep and shallow fill embankment stabilization systems.

Golder investigation of stability of proposed access road to extraction well site area, final design of deep extraction well stabilization system, final design of upper slope stabilization, final design of headscarp seal.

Golder remote & on-site monitoring of precipitation, piezometric heads and slope movements

VTrans evaluations of stability and mitigation alternatives presented at ASCE conference3. Groundwater lowering identified as preferred mitigation alternative

Inclinometer data indicates base of slide mass located up to 120 ft below ground surface (bgs) at counterbalancing berm and extends to base of slope near Clyde River

Sinkhole developed at 30-inch diameter culvert due to 8 ft of vertical separation. Culvert was replaced.

Golder geologic, hydrogeologic and geotechnical subsurface investigation, remote instrumentation installation, and detailed geotechnical laboratory testing.

Inspection of 30-inch diameter culvert indicates additional deformation.

Golder deep slide mitigation alternatives study and preliminary design, upper slope stabilization preliminary design, headscarp seal preliminary design

Golder Geotechnical Data Report (August)

Numerous pavement leveling operations. Culvert location still experiencing significant deformation.

VTrans subsurface investigations including additional borings, instrumentation, laboratory testing and a culvert inspection survey. Culvert deformation measured at about 8 inches.

1.5 ft of settlement measured since 1971 construction (average of 6 in/yr).

Roadway pavement settlements average 4 inches per year

Operations removed 4 ft of pavement (average = 3.2 in/yr for 15 year period 1971-1986).

VTrans subsurface investigation, evaluation and report2. Failure surface identified about 10 to 25 ft below original ground surface beneath embankment fill.

Counterberm construction and more horizontal drains added.

Table 1: Chronology of Key Project Events Geotechnical Design Report VT Route 191 Embankment Slide Newport, Vermont

Event Description

Original embankment construction

April: first sign of slope movement; 5 inches of separation at 30-inch diameter culvert traversing beneath roadway within embankment fill. June: installed underdrain system at toe of upslope embankment slope.

Installed 17 horizontal drains

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November 2017 Page 1 of 1 Project No.: 1668897

Table 2:

Station Offset Upper Lower

111 + 40 17.2' RT 854 52.0 1.5 30 10 40 25 03/20/17 Silt and Silty Sand

111 + 40 103' RT 820 32.0

109 + 18 55' RT 862 32.0

Notes: 1.2.3.4.5. Prepared By: LLM6. Checked By: CJS

Reviewed By: CCB

Geotechnical Boring and Piezometer Summary Geotechnical Design Report VT Route 191 Embankment Slide Newport, Vermont

Test boring locations are shown in Figure 3 "2017 Boring Location Map and Final Design Elements."

B-401

B-402

B-403

Test Boring Designation1,2

As-Drilled Locations3Existing

Ground SurfaceElevation4

(ft)

Boring Depth5

(ft bgs)

Piezometer Installation Information

Screen Interval

(ft bgs)5

Nominal

PVC Casing

Diameter

(in)

Screen

Length

(ft)

Boring logs and piezometer logs presented in Appendix A.

All borings were performed by VTrans in March, 2016.As-drilled locations from field measurements.As-drilled elevations are derived from topographic map shown in Figure 3. Depth below ground surface.

Piezometer Not Installed

Piezometer Not Installed

Midpoint

Depth

(ft bgs)

Installation

Date

(mm/dd/yr)

Well and

Piezometer Screen

Location

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November 2017 1 Project No.1668897

Table 3:

Exploration ID Location(1) BlowsPenetration

(mm)

DCP Penetration

Index (mm/blow)

Cumulative

Penetration (ft)

Calculated SPT

N Value(2)

Average Calculated

SPT N Value(3) Assumed Phi Notes

2 188 94 0.62 102 92 46 0.92 142 197 99 1.56 102 70 35 1.79 162 95 48 2.11 142 56 28 2.29 182 83 42 2.56 155 48 10 0.16 305 24 5 0.24 435 25 5 0.32 425 10 2 0.35 661 1 1 0.35 932 9 4 0.38 441 164 164 0.54 82 71 36 0.77 16

2 32 16 0.88 242 29 15 0.97 252 24 12 1.05 272 11 6 1.09 405 20 4 1.15 475 22 4 1.22 455 11 2 1.26 63

10 10 1 1.29 9310 10 1 1.33 932 42 21 0.14 212 66 33 0.35 171 90 90 0.65 101 48 48 0.81 141 55 55 0.99 132 49 25 1.15 192 45 23 1.30 201 69 69 1.52 122 66 33 1.74 172 71 36 1.97 162 71 36 2.20 162 95 48 2.52 141 151 151 3.01 83 56 19 0.18 222 16 8 0.24 332 14 7 0.28 362 8 4 0.31 473 18 6 0.37 383 21 7 0.44 363 23 8 0.51 343 31 10 0.61 292 21 11 0.68 292 17 9 0.74 323 18 6 0.80 383 10 3 0.83 513 9 3 0.86 545 14 3 0.91 565 16 3 0.96 525 13 3 1.00 58

10 28 3 1.09 5610 37 4 1.21 4910 58 6 1.40 3910 57 6 1.59 3910 47 5 1.75 4310 43 4 1.89 4510 48 5 2.04 4310 63 6 2.25 3710 69 7 2.48 3610 89 9 2.77 32

16

53

18

58

15

39

47

37

35

35

35

35

35

-

- Drove through some shale

over first interval.

- Hole terminated for excessive

top deflection.(4)

- Snow on ground; frozen on

top.

- Not frozen very far into ground

(soft below surface)

- Off vertical at end of test; cone

hitting something hard, possible

rock.

-

Below

Proposed

Access Road

DCP-2

DCP-4

Below

Proposed

Access Road

-

13

17

Dynamic Cone Penetrometer Test Results Geotechnical Design Recommendation Report VT Route 191 Embankment Slide Newport, Vermont

DCP-3

Below

Proposed

Access Road

DCP-1

Below

Proposed

Access Road

12

13

Below

Proposed

Access Road

DCP-5

P:\Projects\2016\1668897 VTrans Newport Supplemental Design\700 Reports\Final Report\Tables\Tbl 3 DCP testing summary.xlsx


Table 3:


(mm)

DCP Penetration

Index (mm/blow)

Cumulative

Penetration (ft)

Calculated SPT

N Value(2)

Average Calculated


35 -


DCP-1

Below

Proposed

Access Road

122 46 23 0.15 201 67 67 0.37 122 39 20 0.50 215 12 2 0.54 604 8 2 0.56 664 2 1 0.57 1305 5 1 0.59 935 7 1 0.61 795 1 0 0.61 2055 1 0 0.62 205

10 8 1 0.64 10310 2 0 0.65 20510 10 1 0.68 930 136 - - -1 112 112 0.81 95 46 9 0.96 312 78 39 1.22 151 64 64 1.43 121 79 79 1.69 111 90 90 1.98 101 92 92 2.29 101 71 71 2.52 111 64 64 2.73 121 56 56 2.91 132 41 21 0.13 212 17 9 0.19 323 25 8 0.27 333 36 12 0.39 273 132 44 0.82 141 171 171 1.38 71 44 44 1.53 143 62 21 1.73 212 66 33 1.95 172 104 52 0.34 132 29 15 0.44 255 37 7 0.56 353 48 16 0.72 245 57 11 0.90 285 211 42 1.59 155 79 16 1.85 245 32 6 1.96 375 46 9 2.11 315 49 10 2.27 305 41 8 2.40 335 41 8 2.54 335 35 7 2.65 365 42 8 2.79 322 51 26 0.17 19 19 352 304 152 1.16 8 82 256 128 2.00 81 57 57 2.19 131 63 63 2.40 121 109 109 2.76 92 242 121 0.79 9 91 89 89 1.09 101 46 46 1.24 142 50 25 1.40 192 74 37 1.64 162 69 35 1.87 162 60 30 2.07 172 79 40 2.33 151 55 55 2.51 13

15

11

15

99

12

12

25

15

25

25

30

30

35

35 -

-

- Snow on ground.

35

- Rod deflecting pretty far from

vertical towards the end of test .

35

32

35

32

35

DCP-11

DCP-10

Between

Proposed

Access Road

& Route

191

Between

Proposed

Access Road

& Route

191

DCP-8

Between

Proposed

Access Road

& Route

191

- Rod deflecting pretty far from

vertical towards the end of test.

- Rod sunk from 0.1' (3.3 cm) to

0.6' (16.9 cm) before first blow.

- Possible gravel between 1.0'

(32.7 cm) and 1.3' (40.5 cm)

penetration.

32

Between

Proposed

Access Road

& Route

191

DCP-7

20

Between

Proposed

Access Road

& Route

191

Between

Proposed

Access Road

& Route

191

DCP-9

DCP-6



Table 3:


(mm)

DCP Penetration

Index (mm/blow)

Cumulative

Penetration (ft)

Calculated SPT

N Value(2)

Average Calculated


35 -


DCP-1

Below

Proposed

Access Road

123 77 26 0.25 193 42 14 0.39 253 91 30 0.69 171 60 60 0.89 121 75 75 1.13 111 55 55 1.31 132 101 51 1.64 132 81 41 1.91 152 91 46 2.21 145 23 5 2.28 44

10 57 6 2.47 3910 58 6 2.66 392 36 18 0.12 222 28 14 0.21 252 57 29 0.40 185 39 8 0.52 343 84 28 0.80 182 31 16 0.90 243 68 23 1.13 202 51 26 1.29 193 46 15 1.44 243 23 8 1.52 343 28 9 1.61 313 24 8 1.69 335 51 10 1.86 304 52 13 2.03 263 45 15 2.18 243 54 18 2.35 223 62 21 2.56 213 71 24 2.79 203 61 20 2.99 211 101 101 0.33 105 46 9 0.48 311 91 91 0.30 101 86 86 0.58 101 79 79 0.84 111 52 52 1.01 131 26 26 1.10 195 81 16 1.36 245 17 3 1.42 515 15 3 1.47 545 38 8 1.59 345 126 25 2.00 191 63 63 2.21 121 77 77 2.46 115 151 30 2.96 171 309 309 1.01 61 126 126 1.43 91 54 54 1.60 132 86 43 1.89 152 88 44 2.18 143 130 43 2.60 143 104 35 2.94 161 114 114 0.37 9 91 270 270 1.26 63 131 44 1.69 143 92 31 1.99 173 72 24 2.23 192 93 47 2.53 143 90 30 2.83 171 164 164 0.54 83 115 38 0.92 152 61 31 1.12 173 85 28 1.39 182 87 44 1.68 143 69 23 1.91 203 86 29 2.19 183 84 28 2.46 182 105 53 2.81 13

18

13

34

24

27

22

35

32

35

35

35

32

32

32

32

- Snow on ground

DCP-14Upper Slide

Slope

Between

Proposed

Access Road

& Route

191,

4.5' from

B-402

DCP-13

DCP-17Upper Slide

Slope

DCP-16Upper Slide

Slope

DCP-12

Between

Proposed

Access Road

& Route

191

Upper Slide

SlopeDCP-15

DCP-14aUpper Slide

Slope

- Snow on ground

- Offset by rock / roots/ something hard;

moved rod over a bit and tried again.

- Snow on ground

- Harder section between 1.46'

(44.4 cm) and 1.51' (46.1 cm)

penetration; possibly wood.

-

-

-

20

10

32

11

15

10

15

12

17

17

16



Table 3:


(mm)

DCP Penetration

Index (mm/blow)

Cumulative

Penetration (ft)

Calculated SPT

N Value(2)

Average Calculated


35 -


DCP-1

Below

Proposed

Access Road

122 43 22 0.14 202 194 97 0.78 101 81 81 1.04 111 59 59 1.24 121 43 43 1.38 151 120 120 1.77 91 69 69 2.00 121 56 56 2.18 131 70 70 2.41 111 53 53 2.59 131 63 63 2.79 122 55 28 2.97 181 114 114 0.37 9 91 283 283 1.30 61 83 83 1.57 111 48 48 1.73 141 88 88 2.02 101 49 49 2.18 141 59 59 2.38 121 52 52 2.55 133 103 34 2.88 165 51 10 0.17 305 39 8 0.30 345 49 10 0.46 305 34 7 0.57 36

Notes:

Made By: LLMChecked By: CJSReviewed By: CCB

4) Per ASTM D6951/D6951M - 09 (Reapproved 2015) DCP tests are not valid once the top of the rod has deflected 3" from plumb.

1) Approximate location of DCP locations and are shown on Figure 3 "2017 Boring Location Map and Final Design Elements."

3) The average calculated SPT N value is an average of the calculated SPT N values over approximately 1 ft of penetration.

DCP-20Upper Slide

Slope

Upper Slide

SlopeDCP-19

DCP-18Upper Slide

Slope

12

13

10

13

32

2) DCP Penetration Index correlated to SPT N-value using Figure 11 in the MinnesotaDOT User Guide to the Dynamic Cone Penetrometer

(1996). This value was then converted from the SPT mm/blow value to an SPT N-value by dividing 305mm(1ft) by the SPT mm/blow value.

15

35

32

32 -

- Deflection issue.

-


November 2017 Page 1 of 1 Project No: 1668897

Gravel (%)

Sand (%)

Silt(%)

1D 1.0 - 3.0 853.0 - 851.0 - 16.5 12.8 - - NP - 53.3 30.2 16.5 A-1-b SM Broken rock within sample.2D 5.0 - 7.0 849.0 - 847.0 - 58.3 13.5 - - NP - 10.9 30.8 58.3 A-4 ML -3D 10.0 - 12.0 844.0 842.0 - 49.0 11.5 - - NP - 13.1 38.0 49.0 A-4 SM -4D 15.0 - 17.0 839.0 - 837.0 45.9 11.8 - - NP - 23.3 30.8 45.9 A-4 SM -5D 20.0 - 22.0 834.0 832.0 64.8 14.4 - - NP - 10.0 25.2 64.8 A-4 ML Some clay within sample.6D 25.0 - 27.0 829.0 827.0 53.6 14.0 - - NP - 11.0 35.4 53.6 A-4 ML -

8D 30.0 - 32.0 824.0 822.0 - 46.8 33.9 - - NP - 10.3 43.0 46.8 A-4 SM A small amount of organic material within sample.

9D 40.0 - 42.0 814.0 812.0 - 82.8 23.6 41 24 17 0.0 5.7 11.5 82.8 A-7-6 CL -10D 45.0 - 46.3 809.0 807.7 - 70.9 16.1 - - NP - 10.9 18.2 70.9 A-4 ML -11D 50.0 - 52.0 804.0 - 802.0 - 88.2 22.9 - - NP - 5.9 5.9 88.2 A-4 ML -

1D 0.0 - 2.0 820.0 - 818.0 - 19.6 19.9 - - NP - 38.7 41.7 19.6 A-1-b SM Asphalt pavement and plant material within sample.

5D 17.0 - 19.0 803.0 801.0 - 49.0 13.9 - - NP - 16.8 34.2 49.0 A-4 SM -7D 25.0 - 27.0 795.0 793.0 - 96.6 26.9 35 24 11 0.3 1.6 1.8 96.6 A-6 ML -

8D 30.0 - 32.0 790.0 - 788.0 - 71.8 16.3 - - NP - 9.8 18.4 71.8 A-4 ML Some cohesion observed in field sample

1D 0.0 - 2.0 862.0 - 860.0 - 24.1 13.1 - - NP - 46.9 28.9 24.1 A-1-b GM Broken rock, grass, grass roots, and plant material within sample.

2D 5.0 - 7.0 857.0 - 855.0 - 33.6 9.3 - - NP - 31.5 34.9 33.6 A-2-4 SM Broken rock within sample.3D 10.0 - 12.0 852.0 - 850.0 - 9.9 5.1 - - NP - 73.9 16.2 9.9 A-1-a GP-GM Broken rock within sample.4D 15.0 - 17.0 847.0 - 845.0 - 13.6 8.2 - - NP - 64.1 22.3 13.6 A-1-a GM Broken rock within sample.6D 25.0 - 27.0 837.0 - 835.0 - 90.8 21.2 32 20 12 0.1 5.2 3.9 90.8 A-6 CL -7D 30.0 - 32.0 832.0 - 830.0 - 91.8 23.2 37 22 15 0.1 2.6 5.6 91.8 A-6 CL -

Notes:

Prepared By: LLM

Checked By: CJS

Reviewed By: CCB

Liquidity Index

AASHTOAASHTO Soil

Classification4,5USCS Soil

Classification4,5 Comments

Table 4: Summary of Laboratory Soil Testing Results Geotechnical Design Report Route 191 Landslide Newport, Vermont

Test Boring Designation1

Existing Ground Surface Elevation 2

(ft)

Sample Number

Sample Depth Below Ground

Surface (ft)

Approximate Sample Elevation

(ft)

Sieve Minus No. 200 (%):

Natural Moisture

Content (%)

Liquid Limit (%)

Plastic Limit (%)

Plasticity Index (%)

B-401 854

Direct Shear Friction

Angle (°)3

27.1

5. Laboratory testing and material classification for split spoon samples was performed by VTrans. Complete laboratory test results for soil testing are provided in Appendix B-1. 4. AASHTO and USCS symbols assigned based on interpretation of laboratory test results.

1. Test boring locations are shown in Figure 3 "2017 Boring Location Map and Final Design Elements."

820B-402

B-403 862

2. Boring locations were not surveyed. As-drilled elevations are derived from electronic site plan in Note 1.

3. Direct shear sample was reconstituted from three samples in boring B-401 (4D,5D,6D).

P:\Projects\2016\1668897 VTrans Newport Supplemental Design\700 Reports\Final Report\Tables\Tbl 4 Soil Index Tests.xlsx

FIGURES

SITE LOCATION

REFERENCES

SITE LOCATION MAP

GEOTECHNICAL DESIGN REPORTROUTE 191 EMBANKMENT, NEWPORT, VERMONT 1

710

710

720

730

740

740

740

750

760

770

780

790

800

810

820

830

840850

850

850

860

730

740

740

740

750

760

770

780

810

820

740

750

760

770

780

790

800

810

810810

820

830

840

850

860

ABANDONED POWER CANAL

CLYDE RIVER

GREAT BAY HYDRO ROAD

UNDERDRAINSYSTEM

A' 4

A4

110+00111+00112+00113+00114+00115+00116+00117+00118+00119+00

120+00VERMONTROUTE 191

B-205 / MW-3 30-INCH DIA.CMP CULVERT

WIRELESSMULTIPLEXER

APPROXIMATEHEAD SCARP OF

DEEP-SEATEDSLIDE

B-209

MW1

I-1

I-2

B-1

B-2

B-3

B-5

B-6

B-7

B-8

B-201

B-202

B-203

B-213

B-214

B-215

B-216

B-302a

B-304a

PTWa

B-316aB-316b

B-311a

B-311b

B-313a

B-313bB-212

CULVERT HEADWALL(FAILED AS OF 2017)

(NOT FUNCTIONAL)

CLAY EXPOSED IN STREAM BANKS(LOCATION APPROXIMATE

CLAY OUTCROP WITH SMALLSCALE SLOPE FAILURES(LOCATION APPROXIMATE)

B-318b

SECONDARY SURFICIALSCARP FEATURES (SHALLOWSLOUGHS OR SLIDES) NOTED

IN THIS AREA

B-4

B-204

MW2B-305b

B-304b

B-304c

PTWbPTWc

B-306a

B-306b

B-307aDATA LOGGER


DEEP-SEATEDSLIDE

B-307cB-307b

EXISTING CONDITIONS (2012) AND LOCATIONSOF BORINGS AND INSTRUMENTATION

INSTALLED FROM 1966 TO 2013

2

GEOTECHNICAL DESIGN REPORTROUTE 191 EMBANKMENT STABILIZATION

NEWPORT, VERMONTTITLE

PROJECT

SCALEDESIGN

PROJECT No. FILE No.

CADD

CHECKREVIEW

J:\D

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2017

3:4

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| Pl

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07/

27/2

017

166-8897

FIGURE

1668897A002.dwg

1:50JRS 2017/07/14

RWC 2017/07/14

JRS 2017/07/14MSP 2017/07/14

GOLDER BORINGS AND REMOTE MONITORING EQUIPMENT INSTALLED JUNE / JULY 2013

NOTES

LEGEND

VTRANS BORINGS INSTALLED 1966 TO 1989

0

FEET

50 100 150

SCALE

LOCAL STATION (FEET)114+00

10 - FOOT CONTOUR AND ELEVATION (FEET MEAN SEA LEVEL) 740

A4

CROSS SECTION LOCATION, DIRECTION AND FIGURE WHEREPRESENTED

APPROXIMATE LOCATION OF HEAD SCARP OF DEEP SEATEDSLIDE (NOT SURVEYED) OBSERVED BY GOLDER MARCH 2012

UNDERDRAIN SYSTEM INSTALLED 1971 AND FLOW DIRECTION(LOCATION APPROXIMATE)

CMP CULVERT

1. BASEMAP PROVIDED BY VTRANS DRAWING FILE TITLED, "NEWPORT VT 191 REVISEDBORE PLAN 020409.DGN". DATED MARCH 20, 2012.

2. INSTALLED LOCATIONS AND ELEVATIONS SURVEYED BY CLD CONSULTINGENGINEERS, INC. 07/24/13. COORDINATES REFERENCE THE NAD83(96) VERMONTSTATE PLANE. ELEVATIONS REFERENCE THE NORTH AMERICAN VERTICAL DATUMOF 1988 (NAVD88).

3. INCLINOMETERS I-1 AND I-2 NO LONGER FUNCTIONAL

4. INCLINOMETER DISPLACEMENT NOT WELL DEFINED AT B-212 AND B-215,THEREFORE NO ARROW IS SHOWN.

5. HORIZONTAL DRAIN LOCATIONS FROM VTRANS MAP TITLED "LOCATION OFHORIZONTAL DRAINS, INSTALLED MAY-JUNE 1973", FIGURE 2, SCALE 1"=100'.

WIRELESS MULTIPLEXER

DATA LOGGER

PUMPING TEST WELL

BORING AND CLUSTER OF 3 OPEN STANDPIPE PIEZOMETERS

BORING, MANUALLY READ INCLINOMETER AND AUTOMATEDGROUTED IN-PLACE VIBRATING WIRE (VW) PRESSURETRANSDUCERS (2 TO 3 PER BORING)

BORING, AUTOMATED SHAPE ACCELARRAY INCLINOMETER ANDGROUTED IN-PLACE VW PRESSURE TRANSDUCERS (2 TO 3 PERBORING)

BORING, AUTOMATED IN-PLACE VW INCLINOMETER ANDGROUTED IN-PLACE VW PRESSURE TRANSDUCERS (2 TO 3 PERBORING)

MONITORING WELL WITH VW PIEZOMETER

PTWa

B-304a

B-302a

B-305b

B-306a

B-316a

BORINGS DRILLED 2006 - 2009

BORINGS AND INCLINOMETERS INSTALLED 2006 - 2009, ARROWINDICATES APPROXIMATE HORIZONTAL DISPLACEMENT DIRECTION

MONITORING WELLS INSTALLED 2008

INCLINOMETER INSTALLED 1989

AUGER BORINGS 1971 - 1974

CASED BORINGS 1966 - 1974

2 - FOOT CONTOUR AND ELEVATION (FEET MEAN SEA LEVEL)

B-209

B-201

MW-1

I-1

B-5

APPROXIMATE EXTENT OF COUNTER BERM INSTALLED 1991

APPROXIMATE EXTENT OF CLAY OUTCROP MAPPED IN 2012

HORIZONTAL DRAINS AS INSTALLED 1973

1991 UNDERDRAIN

1991 UNDERDRAIN


CLYDE RIVER

710

710

720

730

740

740

740

750

760

770

780

790

800

810

820

830

840850

850

850

860

870

880

890

900

730

740

740

740

750

760

770

780

810

820

GREAT BAY HYDRO ROAD

UNDERDRAIN SYSTEM

740

750

760

770

780

790

800

810

810810

820

830

840

850

860

107+00108+00109+00110+00111+00112+00113+00114+00115+00116+00117+00118+00119+00

120+00

VERMONTROUTE 191

EXISTING30-INCHDIA. CMPCULVERT


DEEP-SEATEDSLIDE

B-209

DCP-1DCP-12

DCP-11

DCP-10

DCP-20

DCP-19DCP-18

DCP-17

DCP-15

B-401

CULVERTHEADWALL(FAILED ASOF 2017)

DCP-16

DCP-14

PROPOSEDTOE DRAINOUTLET

PROPOSEDTOE DRAIN

PROPOSEDTOE DRAININLET

PROPOSED SLOPESTABILIZATION LIMITPROPOSED SLOPE

STABILIZATION LIMIT

ACCESS ROAD(EXISTING)

AW-3

PROPOSEDDISCHARGEHEADER PIPE

PROPOSED PRECASTCONCRETE BUILDING

AW-1

PROPOSED ELECTRIC /CONTROL CONDUIT (TYP)

PROPOSEDFLOW METERVAULT (TYP)

C C C C C C CC

U

PWTa(EXISTING)

AW-2


DEEP-SEATEDSLIDE

PROPOSEDDISCHARGEHEADERPIPE

PROPOSEDGROUNDWATEROUTFALL

PROPOSEDHEADSCARPSEAL AREA

B-403

DCP-2

DCP-3DCP-4

DCP-5

DCP-9DCP-8

DCP-7

DCP-6

DCP-13 B-402

50+00

51+00DCP-1

52+00

53+00

54+0055+00

56+00

PROPOSED42-INCHCULVERT

PROPOSEDCUT OFFTRENCHDRAIN

49+0

0

EXISTING18 INCHCULVERT

PROPOSEDACCESSROAD

2017 BORING LOCATION MAP ANDPROPOSED FINAL DESIGN ELEMENTS

3



PROJECT

SCALEDESIGN


CADD

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out:

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17 B

OR

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LO

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ION

MAP

| M

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/17/

2017

11:

00 A

M |

Plot

ted:

rcla

rk 0

7/18

/201

7

166-8897

FIGURE

1668897A003

1:50CJS 2017/07/14

RWC 2017/07/14

JRS 2017/07/14MSP 2017/07/14

NOTES

LEGEND

0

FEET

50 100 150

SCALE

LOCAL STATION (FEET)114+00

10 - FOOT CONTOUR AND ELEVATION (FEET MEAN SEA LEVEL) 740

APPROXIMATE LOCATION OF HEAD SCARP OF SLIDE (NOTSURVEYED) OBSERVED BY GOLDER MARCH 2012

UNDERDRAIN SYSTEM INSTALLED 1971 AND FLOW DIRECTION(LOCATION APPROXIMATE)

CMP CULVERT

1. BASEMAP PROVIDED BY VTRANS DRAWING FILE TITLED, "NEWPORT VT 191 REVISEDBORE PLAN 020409.DGN". DATED MARCH 20, 2012.

2. LOCATIONS OF DCP AND 400 SERIES BORINGS ARE BASED ON FIELDMEASUREMENT. ACTUAL LOCATIONS MAY VARY FROM THOSE SHOWN.

3. PROPOSED STABILIZATION FEATURES BASED, IN PART, ON PRELIMINARY PLANSPROPOSED BY STANTEC AND GOLDER TITLED "PROPOSED IMPROVEMENT,NEWPORT CITY, COUNTY OF ORLEANS, VT ROUTE 191 (PRINCIPAL ARTERIAL)",FEBRUARY 10, 2017.

2 - FOOT CONTOUR AND ELEVATION (FEET MEAN SEA LEVEL)

DCP-1

B-401

GOLDER EXPLORATIONS 2017

GOLDER APRIL 2017 DYNAMIC CONE PENTROMETER PROBELOCATION

GOLDER MARCH 2017 BORINGS

PROPOSED HEADSCARP SEALING CONSTRUCTION (SEE FIGURE 7 FOR DESIGN DETAIL)

PROPOSED HEADSCARP SEAL AREA

RELOCATE AND REPLACE UNDERDRAIN SECTION

DISCHARGE HEADER PIPE

ELECTRIC / CONTROL CONDUIT, UNDERGROUNDC

PROPOSED GROUNDWATER EXTRACTION WELL

EXISTING GROUNDWATER EXTRACTION WELL

15'15'

1'(TYP.)

N

17

600

650

700

750

800

850

0 100 200 300 400 500 600 700

600

650

700

750

800

850

ELEV

ATIO

N (F

T-M

SL)

ELEV

ATIO

N (F

T-M

SL)

HORIZONTAL SCALE (FT)

-100

EOB

B-302AO/L

B-20120 FT (W)

B-4

B-305 A,B12 FT (E)

EOB

EOB

EOB

B-306A,B2 FT (W)

EOB

EOB

B-21369 FT (E)

EOB

B-316 A,BO/L

EOB

B-311A,B63 FT (W)GSE @ BORING = 721 FT

EOB

B-215 B-313A,B43 FT (W)

EOB

N

2435953738655116254325758357

80RR12395R

117*

49

34 R*93*81*

R*R*R*R*R152

R*R*R

7

N124012302229151834169312883123R*R*R*R*

R* R*R*76*52*

80*R*R*R*R*

N

4

105

95

789

4722

73R9384

66

117605249

40

N762222622 3335

2728

29

274042

53 46

7585

41

152

1918

59

1816

53

20

2127

26

24

42

50

28

R

-140


CLYDE RIVER

EXISTING GROUND SURFACE


A'NORTH

ASOUTH

EMBANKMENT FILL

UPPER SILTS AND CLAYS

LOWER CLAY

LOWER SANDS AND GRAVELS

750

LOWER SILTS / WEATHERED BEDROCK

?

LOWER SILTS / WEATHERED BEDROCK

MIDDLE SILTS AND SANDS

MIDDLE SANDS AND GRAVELS

BEDROCK

UPPER SILTS AND SANDS

LOWER CLAY

UPPER SILTS AND CLAYS

?

MIDDLE SANDS AND GRAVELS

MIDDLE SILTS AND SANDS

?

BEDROCK

ROAD FILL

VERMONT ROUTE 191℄

PTW A,B,CAPPROXIMATE CL

EOB

CROSS SECTION A - A'GEOTECHNICAL DATA

4

GEOTECHNICAL DESIGN REPORTROUTE 191 EMBANKMENT


PROJECT

SCALEDESIGN


CADD

CHECKREVIEW

REVISION DESCRIPTION CADD CHK RVWDESDATEREV

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166-8897

FIGURE

1668897A004.dwg

AS SHOWNNSC 2014-06-16

RWC 2017/07/14

JRS 2017/07/14MSP 2017/07/14

0

FEET

30 60 90

SCALE

SOIL CLASSIFICATIONS

NOTES

LEGEND

1. SEE BORING LOCATION PLAN FOR BORING LOCATIONS.

2. SEE BORING LOGS FOR SOIL LITHOLOGIC DESCRIPTIONS.

3. SEE LABORATORY TEST REPORTS FOR COMPLETE LABORATORY DATA.

4. GROUNDWATER ELEVATION ESTIMATES BASED ON MEASUREMENTS TAKEN AT THETIME OF SUBSURFACE EXPLORATIONS.

5. BEDROCK CONTOURS INTERPRETED FROM BOREHOLE DATA (GOLDER 2014). ACTUALENCOUNTERED BEDROCK SURFACE ELEVATIONS WILL VARY AND BE MORE ERRATICTHAN SHOWN.

6. THIS GENERALIZED SUBSURFACE PROFILE IS INTENDED TO CONVEY TRENDS INSUBSURFACE CONDITIONS. THE BOUNDARIES BETWEEN STRATA ARE APPROXIMATEAND IDEALIZED, AND HAVE BEEN DEVELOPED BY INTERPRETATIONS OF WIDELYSPACED EXPLORATIONS AND EXAMPLES. ACTUAL SOIL AND ROCK TRANSITIONS MAYVARY AND ARE PROBABLY MORE ERRATIC. FOR MORE SPECIFIC INFORMATION REFERTO EXPLORATION LOGS.

7. HORIZONTAL DATUM IS VERMONT STATE PLANE NAD83 (96). VERTICAL DATUM ISNAVD88.

BR638

24

B-307

EOB

= BORING LOCATION - 300 SERIES = GOLDER OTHER = VTRANS

= END OF BORING

= OBSERVED GROUNDWATER ELEVATION (FT)

= BEDROCK ELEVATION (FT-MSL)

= N - VALUE

EL.758.4 = GROUND SURFACE ELEVATION

* = SAMPLED WITH A 3" SPLIT SPOON

EMBANKMENT FILL: A-1-B/A-2-4/A-4, GRAY BROWN TO DARK GRAY BROWN, MOIST TO WET, LOOSE TO DENSE, FINETO COARSE SAND, TRACE TO SOME SILT, TRACE TO LITTLE GRAVEL, LAYERS OF GRAY SILT THROUGHOUT.

UPPER SILTS AND SANDS: A-2-4/A-4, GRAY BROWN TO DARK BROWN, MOIST, MEDIUM DENSE TO DENSE, LAYERS OFFINE TO MEDIUM SAND, FINE SAND, AND SILT, TRACE COARSE SAND AND FINE GRAVEL THROUGHOUT.

UPPER SILTS AND CLAYS: A-4/A-6, DARK GRAY, MOIST TO WET, STIFF TO VERY STIFF, LAYERS OF SILTY CLAY,CLAYEY SILT, AND SILTY FINE SAND.

MIDDLE SILTS AND SANDS: A-4, GRAY, DRY TO MOIST, VERY DENSE, LAYERS OF SILT, SILTY FINE TO MEDIUM SAND,AND CLAYEY SILT, TRACE TO LITTLE ROUNDED GRAVEL THROUGHOUT. OCCASIONAL LAYERS OF DARK GRAY FINETO MEDIUM SAND ENCOUNTERED.

MIDDLE SANDS AND GRAVELS: A-1-B/A-2-4, MEDIUM BROWN AND ORANGE BROWN, MOIST, VERY DENSE, SILT, SOMEFINE SAND, SOME GRAVEL. POCKETS OF GRAY, MOIST, VERY DENSE, FINE TO MEDIUM SAND ENCOUNTERED.

LOWER CLAYS: A-7-5/A-7-6, LAYERED ORANGE BROWN AND GRAY CHANGING TO BROWN AND GRAY TOWARDS THERIVER, DRY TO MOIST, HARD, VARVED SILTY CLAY AND SILTY FINE SAND. ZONES OF DISTURBANCE ANDSLICKENSIDES ENCOUNTERED THROUGHOUT DEPOSIT. SEAMS CONTAINING SAND AND GRAVEL ENCOUNTEREDWITHIN DEPOSIT SOUTH OF B-306. VARVE THICKNESS RANGES FROM 0.1 INCHES UP TO 2 INCHES. DEPOSITS OFNON-VARVED CLAY UP TO 5 FEET THICK ENCOUNTERED.

LOWER SANDS AND GRAVELS: A-1-B, BROWN AND GRAY, MOIST, MEDIUM DENSE TO VERY DENSE, FINE TO COARSESAND, SOME TO LITTLE GRAVEL, LITTLE SILT.

LOWER SILTS / WEATHERED BEDROCK: A-4, DARK BROWN, MOIST TO WET, DENSE, SILTS AND SILTY FINE SANDS.FRACTURED BEDROCK ENCOUNTERED ALONG BOTTOM OF DEPOSIT PRIOR TO REACHING BEDROCK.

REFERENCES1.) BASEMAP PROVIDED BY VTRANS DRAWING FILE TITLED, "NEWPORT VT 191

REVISED BORE PLAN 020409.DGN". DATED MARCH 20, 2012.2.) TOE DRAIN ELEVATIONS BASED ON THE STANTEC DRAWING "TOE DRAIN PROFILE

PRO-8" DATED 02/10/2017.3.) HORIZONTAL DRAIN ALIGNMENT CONSTRUCTED USING STANTEC DRAWING

"ALIGNMENT PLAN AP-2" DATED 02/10/2017.

POTENTIAL TRENCHINGIMPACT ON HORIZONTAL DRAINS


NEWPORT, VERMONT

FIGURE 7

1.) LOCATIONS OF HORIZONTAL DRAINS ARE APPROXIMATE AND ARE BASED OFF OFHISTORICAL CONSTRUCTION RECORDS AND DRAWINGS PRIOR TO COUNTERBERMCONSTRUCITON. ACTUAL FIELD CONDTIONS MAY VARY.

2.) TOE DRAIN TRENCH LAYOUT SCALED BY HAND FROM STANTEC DRAWING INREFERENCE 3 AND SHOWN IN FIGURE 3.

3.) THE SCALE OF THE HORIZONTAL DRAINS IN THIS FIGURE ARE EXAGGERATED FORCLARITY.

NOTES

TOE DRAIN TRENCH PROFILESCALE: 1" = 20'

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HD-14

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HD-3

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HD-12

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HD-13

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PROPOSED GROUND SURFACE

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EXISTING 2" DIAMETER HORIZONTAL DRAIN (TYP.)

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200+00

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6" HDPE CORREGATED DOUBLE WALL PERFORATED PIPE

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DRAINAGE STONE

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GEOTEXTILE FOR UNDER DRAIN TRENCH LINING

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CLEANOUT

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-3.36%

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-7.73%

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-2.92%

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166-8897

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1668897A008

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AS SHOWN

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0

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CJS

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08/07/17

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RWC

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CCB

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08/08/17

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MSP

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08/09/17

EDGE OF PAVEMENT

ROAD SUBBASE

ITEM 649.11 GEOTEXTILESEPERATION

9" (MIN.) UPPER SANDCUSHION LAYER

MODIFIED 703.03 (1" MINUS)

30 mil (TYP) GEOMEMBRANE LINER

6" (MIN.) LOWER SAND CUSHION LAYERMODIFIED 703.03 (1" MINUS)

GRADE AND PROOFROLL NATIVESUBGRADE SOIL AT A MINIMUM 2%

SLOPE TO PROMOTE DRAINAGE

REMOVE AND REPLACE EXISTING TOPSOIL &EMBANKMENT MATERIAL (EARTH BORROW 703.02)

(DEPTH VARIES TO MATCH EXISTING GRADE)(9" MIN THICKNESS REQUIRED)

NOTES:1) DRAWING IS NOT TO SCALE AND IS EXAGGERATED TO SHOW DETAIL.2) GEOMEMBRANE LINER SHALL EXTEND INTO DRAINAGE MATERIAL

SURROUNDING THE EXISTING UNDERDRAIN.3) GEOMEMBRANE LINER SHALL EXTEND UNDER ROADWAY A MINIMUM OF

1FT (12") BEYOND THE EDGE OF PAVEMENT.4) REFER TO FIGURE 3 FOR HEADSCARP SEAL LOCATION.5) REFER TO GEOMEMBRANE LINER SPECIAL PROVISION FOR

INSTALLATION REQUIREMENTS.

xxxx

xxxx

xxxx

xxxx

xxxx

xxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

xxxx

xxxx

xxx

18"

18"

12"(MIN.)EXISTING UNDERDRAIN

(REMOVE & REPLACE IN KIND)

704.16 DRAINAGE AGGREGATE(3/4" STONE)

01

in

166-8897SUBTITLEA

FIGURE

80

2017/07/14

CJS

RWC

MCM

CCB

GEOTECHNICAL DESIGN REPORTROUTE 191 EMBANKMENT STABILIZATIONNEWPORT, VERMONT

VERMONT AGENCY OF TRANSPORTATION2178 AIRPORT ROAD, UNIT BBERLIN, VT 05641-8628

TYPICAL HEADSCARP SEAL SECTION &GEOMEMBRANE TIE-IN UNDERDRAIN DETAIL

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Path: \\manchester\cadd\Drawings\2016\1668897 VTRANS Newport, VT\PRODUCTION\ | File Name: 1668897A005.dwg

APPENDIX A 400 SERIES BORING LOGS

Table A-1

TERMS DESCRIBING

UNIFIED SOIL CLASSIFICATION SYSTEM DENSITY/CONSISTENCY

MAJOR DIVISIONSGROUP

SYMBOLS TYPICAL NAMES

Coarse-grained soils (more than half of material is larger than No. 200

COARSE- CLEAN GW Well-graded gravels, gravel- sieve): Includes (1) clean gravels; (2) silty or clayey gravels; and (3) silty,

GRAINED GRAVELS GRAVELS sand mixtures, little or no fines. clayey or gravelly sands. Consistency is rated according to standard

SOILS penetration resistance.

(little or no GP Poorly-graded gravels, gravel Modified Burmister System

fines) sand mixtures, little or no fines. Descriptive Term Portion of Total

trace 0% - 10%

little 11% - 20%

GRAVEL GM Silty gravels, gravel-sand-silt some 21% - 35%

WITH mixtures. adjective (e.g. sandy, clayey) 36% - 50%

FINES

(Appreciable GC Clayey gravels, gravel-sand-clay Density of Standard Penetration Resistance

amount of mixtures. Cohesionless Soils N-Value (blows per foot)

fines) Very loose 0 - 4

Loose 5 - 10

CLEAN SW Well-graded sands, gravelly Medium Dense 11 - 30

SANDS SANDS sands, little or no fines Dense 31 - 50

Very Dense > 50

(little or no SP Poorly-graded sands, gravelly

fines) sand, little or no fines.

Fine-grained soils (more than half of material is smaller than No. 200

sieve): Includes (1) inorganic and organic silts and clays; (2) gravelly, sandy

SANDS SM Silty sands, sand-silt mixtures or silty clays; and (3) clayey silts. Consistency is rated according to shear

WITH strength as indicated.

FINES Approximate

(Appreciable SC Clayey sands, sand-clay Undrained

amount of mixtures. Consistency of SPT N-Value Shear Field

fines) Cohesive soils blows per foot Strength (psf) Guidelines

WOH, WOR,

ML Inorganic silts and very fine WOP, <2

sands, rock flour, silty or clayey Soft 2 - 4 250 - 500 Thumb easily penetrates

fine sands, or clayey silts with Medium Stiff 5 - 8 500 - 1000 Thumb penetrates with

SILTS AND CLAYS slight plasticity. moderate effort

Stiff 9 - 15 1000 - 2000 Indented by thumb with

FINE- CL Inorganic clays of low to medium great effort

GRAINED plasticity, gravelly clays, sandy Very Stiff 16 - 30 2000 - 4000 Indented by thumbnail

SOILS clays, silty clays, lean clays. Hard >30 over 4000 Indented by thumbnail

(liquid limit less than 50) with difficulty

OL Organic silts and organic silty Rock Quality Designation (RQD):

clays of low plasticity. RQD = sum of the lengths of intact pieces of core* > 100 mm

length of core advance *Minimum NQ rock core (1.88 in. OD of core)

MH Inorganic silts, micaceous or

diatomaceous fine sandy or Correlation of RQD to Rock Mass Quality

SILTS AND CLAYS silty soils, elastic silts. Rock Mass Quality RQD

Very Poor <25%

CH Inorganic clays of high Poor 26% - 50%

plasticity, fat clays. Fair 51% - 75%

Good 76% - 90%

(liquid limit greater than 50) OH Organic clays of medium to Excellent 91% - 100%

high plasticity, organic silts. Desired Rock Observations: (in this order)

Color (Geological Society of America Rock Color Chart)

Texture (aphanitic, fine-grained, etc.)

HIGHLY ORGANIC Pt Peat and other highly organic Strength (ISRM Classification per Table A-2)SOILS soils. Lithology (igneous, sedimentary, metamorphic, etc.)

Hardness (very hard, hard, mod. hard, etc.)

Desired Soil Observations: (in this order) Weathering (fresh, very slight, slight, moderate, mod. severe,

Color (Munsell color chart) severe, etc.)

Moisture (dry, damp, moist, wet, saturated) Geologic discontinuities/jointing:

Density/Consistency (from above right hand side) -dip (horiz - 0-5, low angle - 5-35, mod. dipping -

Name (sand, silty sand, clay, etc., including portions - trace, little, etc.) 35-55, steep - 55-85, vertical - 85-90)

Gradation (well-graded, poorly-graded, uniform, etc.) -spacing (very close - <5 cm, close - 5-30 cm, mod.

Plasticity (non-plastic, slightly plastic, moderately plastic, highly plastic) close 30-100 cm, wide - 1-3 m, very wide >3 m)

Structure (layering, fractures, cracks, etc.) -tightness (tight, open or healed)

Bonding (well, moderately, loosely, etc., if applicable) -infilling (grain size, color, etc.)

Cementation (weak, moderate, or strong, if applicable, ASTM D 2488) Formation (Waterville, Ellsworth, Cape Elizabeth, etc.)

Geologic Origin (till, marine clay, alluvium, etc.) RQD and correlation to rock mass quality (very poor, poor, etc.)

Unified Soil Classification Designation ref: AASHTO Standard Specification for Highway Bridges

Groundwater level 17th Ed. Table 4.4.8.1.2A

Recovery

Sample Container Labeling Requirements:

Project Name / Town Blow Counts Boring Number Sample Recovery Sample Number Date Sample Depth Personnel Initials

0 - 250 Fist easily PenetratesVery Soft

(mo

re t

ha

n h

alf o

f m

ate

ria

l is

sm

alle

r th

an N

o. 2

00

sie

ve

siz

e)

(mo

re t

ha

n h

alf o

f m

ate

ria

l is

la

rge

r th

an N

o. 2

00

sie

ve

siz

e)

(mo

re t

ha

n h

alf o

f co

ars

e

fra

ctio

n is la

rge

r th

an N

o.

4

sie

ve

siz

e)

(mo

re t

ha

n h

alf o

f co

ars

e

fra

ctio

n is s

ma

ller

tha

n N

o. 4

sie

ve

siz

e)

Key to Soil and Rock Descriptions Including Boring Log Terms and Field Identification Information

September 2012

Table A-2

Classification of Rock Material Strengths1

Grade Description Field Identification

Approx. Range of Uniaxial Compressive Strength

MPa psi

S1 Very soft clay Easily penetrated several inches by fist

<0.025 <4

S2 Soft clay Easily penetrated several inches by thumb

0.025-0.05 4-7

S3 Firm clay Can be penetrated several inches by thumb with moderate effort

0.05-0.10 7-15

S4 Stiff clay Readily indented by thumb but penetrated only with great effort

0.10-0.25 15-35

S5 Very stiff clay Readily indented by thumbnail 0.25-0.50 35-70

S6 Hard clay Indented with difficulty by thumbnail >0.50 >70

R0 Extremely weak rock Indented by thumbnail 0.25-1.0 35-150

R1 Very weak rock Crumbles under firm blows with point of geological hammer; can be peeled by a pocket knife

1-5 150-725

R2 Weak rock

Can be peeled by a pocket knife with difficulty; shallow indentations made by firm blow with point of geological hammer

5-25 725-3,500

R3 Medium strong rock

Cannot be scraped or peeled with a pocket knife; specimen can be fractured with single firm blow of geological hammer

25-50 3,500-7,000

R4 Strong rock Specimen requires more than one blow of geological hammer to fracture it

50-100 7,000-15,000

R5 Very strong rock Specimen requires many blows of geological hammer to fracture it

100-250 15,000-36,000

R6 Extremely strong rock

Specimen can only be chipped with geological hammer

>250 >36,000

Note: Grades S1 to S6 apply to cohesive soils, for example clays, silty clays, and combinations of silts and clays with

sand, generally slow draining. Discontinuity wall strength will generally be characterized by grades R0-R6 (rock) while S1-S6 (clay) will generally apply to filled discontinuities.

1 International Society for Rock Mechanics (ISRM), Commission on standardization of laboratory and field tests (1978): Suggested

methods for the quantitative description of discontinuities in rock masses. Int. J. Rock Mech. Min. Sci. & Geomech. Abstr., Vol. 15, No. 6, pp. 319-368.

S1: 1.0 ft - 3.0 ft, A-1-b, Top 4": Wet GRAVEL.Bottom 11.5": Grey-brown, wet, very dense, gravelly, fine tocoarse SAND, little silt, (SM), (FILL), Rec. = 1.3 ft

S2: 5.0 ft - 7.0 ft, A-4, Grey-brown, wet, medium dense, SILT,some fine to coarse sand, trace gravel towards top of sample,(ML), (FILL), Rec. = 0.75 ft

S3: 10.0 ft - 12.0 ft, A-4, Tan/grey, wet, medium dense, silty,fine to coarse SAND, trace gravel. Grey silt concentrated inpockets within the tan silty sand, (SM), (FILL). PP: 2.0 TSF,Rec. = 1.5 ft

S4: 15.0 ft - 17.0 ft, A-4, Tan-grey, some mottling, wet, verystiff, silty fine to coarse SAND, little gravel. Sample is sandierat top than bottom, (SM), (FILL), Rec. = 1.1 ft

S5: 20.0 ft - 22.0 ft, A-4, Light grey with pockets of darker greymaterial, moist, stiff, SILT, some fine to coarse sand, someclay, trace gravel, (ML), (FILL)., Rec. = 1.0 ft

12.8

13.5

11.5

11.8

14.4

30.2

30.8

37.9

30.8

25.2

16.5

58.3

49.0

45.9

64.8

35-34-19-20

(53)

9-10-7-10(17)

11-13-12-10

(25)

5-9-7-9(16)

8-7-6-7(13)

53.3

10.9

13.1

23.3

10.0

STATE OF VERMONTAGENCY OF TRANSPORTATION

MATERIALS & RESEARCH SECTIONSUBSURFACE INFORMATION

DEPTH(ft)

BORING NUMBER: B-401SHEET 1 of 3DATE STARTED: 3/08/17DATE COMPLETED: 3/20/17

SYMBOL

BORING TYPE: WASH BORESAMPLE TYPE: SPLIT BARRELHAMMER TYPE: AUTOCHECKED BY: JDL

PROJECT NUMBER: GAI 1668897SITE NUMBER: -GROUND ELEVATION: 854'GROUNDWATER DEPTH: 10.7' 3/20/17PROJECT PIN NUMBER: -

PROJECT NAME: Newport City STP 134-3(22)SITE NAME: Route 191 LandslideSTATION: 111 + 40OFFSET: 17.2' RTVTSPG:

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

BORING CREW: VTransDRILLER: Harold GarrowLOGGER: Laura McKeownBORING RIG: CME-55 Track

CLASSIFICATION OF MATERIALS(Description)

LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

Top of Well Elevation: 854.0 ft

WELLDIAGRAM

S6: 25.0 ft - 27.0 ft, A-4, Tan with pockets of dark greymaterial, some mottling, wet, stiff, fine to coarse sandy SILT,trace gravel, (ML), Rec. = 1.2 ft

S7: 30.0 ft - 32.0 ft, A-4, Tan with dark brown seams, wet,medium stiff, silty fine to coarse SAND, trace gravel, traceorganic wood fibres in dark brown seams, (SM). PP: 2.0 TSF,Rec. = 1.2 ft

S8: 35.0 ft - 37.0 ft, No recovery, Rec. = 0.0 ft

S9: 40.0 ft - 42.0 ft, A-7-6, Grey, moist, very stiff, silty CLAY,little fine to coarse sand, trace gravel, (CL). PP: 4.5, 4.5 TSF,Rec. = 1.4 ft

S10: 45.0 ft - 47.0 ft, A-4, Grey with pockets of tan material,moist, hard, SILT, little fine to coarse sand, trace gravel, (ML).PP > 4.5 TSF; TV: 2.4 TSF, Rec. = 1.1 ft

14.0

33.9

23.6

16.1

35.4

42.9

11.5

18.2

53.6

46.8

82.8

70.9

8-5-6-7(11)

5-3-3-4(6)

11-4-3-4(7)

6-6-10-28(16)

12-41-50/3"(R)

11.0

10.3

5.7

10.9



DEPTH(ft)


SYMBOL




27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

47.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

WELLDIAGRAM

S11: 50.0 ft - 52.0 ft, A-4, Grey, moist, hard, SILT, little clay,trace gravel, trace fine to coarse sand, (ML). PP: 4.0 TSF; TV:4.0 TSF, Rec. = 1.9 ft

Hole stopped @ 52.0 ft

Notes:- Pavement thickness: 0.45'.- Driller noted cobbles/boulders from 43.5' to 45'.- Drilling of B-401 completed 3:15 on 03/08/2017. Wellinstalled from 10:50 AM to 3:40 PM on 03/20/2017.- Water Levels: - 3.4' b.g.s. at 3:22 PM on 03/08/2017. - 32.1' b.g.s. at 11:02 AM on 03/20/2017. - 10.7' b.g.s. in well at 3:20 PM on 03/20/2017; Water rightbelow pavement around well.- Location approximate. Boring not surveyed. Ground surfaceelevation estimated from contours on plan.

22.9 5.9 88.28-18-20-26

(38)

5.9



DEPTH(ft)


SYMBOL




52.5

55.0

57.5

60.0

62.5

65.0

67.5

70.0

72.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

WELLDIAGRAM

S1: 0.0 ft - 2.0 ft, A-1-b, SS, Brown, stiff, fine to coarse SAND, somegravel, little silt, trace organics, (SM), (FILL). Sample frozen, Rec. = 1.3ft

S2: 5.0 ft - 7.0 ft, SS, No recovery, Rec. = 0.0 ft



S5: 17.0 ft - 19.0 ft, A-4, SS, Brown with some mottling, stiff, silty, fine tocoarse SAND, little gravel, (SM), Rec. = 1.1 ft


19.9

13.9

41.7

34.2

19.6

49.0

6-3-6-4(9)

3-5-4-4(9)

9-16-13-14

(29)

6-7-11-6(18)

12-10-3-4(13)

5-6-8-11(14)

38.7

16.8



DEPTH(ft)


SYMBOL



PROJECT NAME: Newport City STP 134-3(22)SITE NAME: Route 191 LandslideSTATION: 111 + 40OFFSET: 103' RTVTSPG:

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

S7: 25.0 ft - 27.0 ft, A-6, SS, Grey, moist, very stiff, silty CLAY, tracegravel, trace fine to coarse sand, (CL-ML). PP: 1.25, 3.75 TSF, Rec. =1.4 ft

S8: 30.0 ft - 32.0 ft, A-4, SS, Grey, wet, very stiff, SILT, little fine tocoarse sand, little clay, trace gravel, (ML), Rec. = 1.6 ft


Notes:- Water at 0.9' b.g.s. in casing at 2:05 PM 03/13/2017. Water at sufacewhen casing removed.- Collapse back to 14.2' when casing removed.- Location approximate. Boring not surveyed. Ground surface elevationestimated from contours on plan.

26.9

16.3

1.8

18.4

96.6

71.8

5-9-17-15(26)

6-16-14-16

(30)

1.6

9.8



DEPTH(ft)


SYMBOL




27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

47.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

S1: 0.0 ft - 2.0 ft, A-1-b, SS, Brown, moist, medium dense, fine to coarsesandy GRAVEL, some silt, trace organic material, (GM), (FILL), Rec. =1.0 ft

S2: 5.0 ft - 7.0 ft, A-2-4, SS, Top 0.2': Dark grey rock fragments,probable cobble.Bottom 0.9': Tan with some mottling, very dense, fine to medium SAND,some gravel, some silt, (SM), Rec. = 1.1 ft

S3: 10.0 ft - 12.0 ft, A-1-a, SS, Dark grey, wet, GRAVEL, some fine tocoarse sand, trace silt in spoon tip, (GP-GM). Probably broken upcobble/boulder, Rec. = 0.3 ft

S4: 15.0 ft - 17.0 ft, A-1-a, SS, Dark grey, dense, GRAVEL, some brownfine to coarse sand, little silt, (GM), Rec. = 0.7 ft


13.1

9.3

5.1

8.2

29.0

34.9

16.2

22.3

24.1

33.6

9.9

13.6

6-8-7-7(15)

14-43-29-20

(72)

50/5"(R)

24-18-21-22

(39)

20-15-21-27

(36)

46.9

31.5

73.9

64.1



DEPTH(ft)


SYMBOL




2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

S6: 25.0 ft - 27.0 ft, A-6, SS, Grey , wet, hard, silty CLAY, trace gravel,trace sand, (CL). PP: 2.25, 4.25, >4.5 TSF; TV: 1.5, Rec. = 1.9 ft

S7: 30.0 ft - 32.0 ft, A-6, SS, Grey, wet, hard, silty CLAY, trace gravel,trace sand, (CL). PP: 3.25, 3.25, 3.75 TSF; TV: 4.5, Rec. = 2.0 ft


Notes:- Water at 1.3' b.g.s. in casing at 11:45 AM 03/10/2017.- Collapse back to 8.2' when casing removed.- Location approximate. Boring not surveyed. Ground surface elevationestimated from contours on plan.

21.2

23.2

4.0

5.6

90.8

91.8

14-21-24-28

(45)

11-18-26-31

(44)

5.2

2.6



DEPTH(ft)


SYMBOL




27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

47.5



LOG

OF

BO

RIN

G &

WE

LL 2

017

NE

WP

OR

T.G

PJ

VT

AO

T.G

DT

7/

25/1

7

AASHTOGRAVEL

(%)

AASHTOSAND

(%)

AASHTOFINES

(%)

M.C.(%)

BLOWSPER 6 IN

(N VALUE)

APPENDIX B LABORATORY TEST RESULTS

APPENDIX B-1 FROM 400-SERIES BORING SAMPLES

State of VermontAgency of Transportation

Construction and Materials BureauCentral Laboratory

Report on Soil Sample

Distribution list

Lab number: E170202 Corrected copy: N/A 4/12/2017 2:33:44 PReport Date:

Site: VT 191 SLIDEProject: NEWPORT Number: STP 1343(22)

Quantity:

Comment: Sample 1D

Received: 3/10/2017

Submitted by: Golder

Tested by: J. Daigneault

Station: 111+40 Offset: 18.0

Date sampled: 3/8/2017 Tested: 3/10/2017

Hole: B-401 Depth: 1 to: 3FT FT

Field description: Si Gr Sa, gry-brn, Moist

Address:

Sample type: Split Barrel

Sample source/Outside agency name:

Location used: Examined for: MC, GS

Test Results

Gr: 53.3%

Sa: 30.2%

Si: 16.5%

D2487: SM

M145: A-1-b

Reviewed by: Marcy L. Montague, PE, Senior Geotechnical Engineer

Sandy Gravel

Comments: Lab Note: Broken rock was within sample.

75 mm (3.0"):

37.5 mm (1.5"):

19 mm (3/4"): 94.9%

9.5 mm (3/8"): 74.3%

4.75 mm (#4): 61.7%

2.00 mm (#10): 46.7%

850 µm (#20): 35.3%

425 µm (#40): 27.6%

250 µm (#60): 23.0%

150 µm (#100): 20.5%

75 µm (#200): 16.5%

T-88 % Passing

Sieve Analysis

Total Sample

Hydrometer Analysis

Particles smaller % total sample

0.05 mm:

0.02 mm:

0.005 mm:

0.002 mm:

0.001 mm:

T-265 Moisture content: 12.8%

T-89 Liquid Limit:

T-90 Plastic Limit:

T-90 Plasticity Index: NP

Maximum density:

Optimum moisture:

Method:Test method: T-180

Limits

Moisture Density

pcf

T-100 Specific Gravity:




Distribution list



Hole: B-401 Depth: 1 3FT FT-

T-88 Particle size analysis

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.010.1110100Particle size, mm

Pct smaller




Distribution list



Quantity:

Comment: Sample 2D

Received: 3/10/2017






Field description: Gr Si Sa, gry, M

Address:




Test Results

Gr: 10.9%

Sa: 30.8%

Si: 58.3%

D2487: ML

M145: A-4


Sandy Silt

Comments:

75 mm (3.0"):

37.5 mm (1.5"):

19 mm (3/4"):

9.5 mm (3/8"): 95.9%

4.75 mm (#4): 93.3%

2.00 mm (#10): 89.1%

850 µm (#20): 84.5%

425 µm (#40): 79.6%

250 µm (#60): 74.6%

150 µm (#100): 69.1%

75 µm (#200): 58.3%

T-88 % Passing

Sieve Analysis

Total Sample

Hydrometer Analysis


0.05 mm:

0.02 mm:

0.005 mm:

0.002 mm:

0.001 mm:


T-89 Liquid Limit:

T-90 Plastic Limit:


Maximum density:

Optimum moisture:


Limits

Moisture Density

pcf
