DEWA_324741_US_209_Slope_Failure_-_Geotechnical_Report_FINAL_2023-06-28_0003.pdf

REPORT COVER PAGE

Geotechnical Engineering Report

DEWA 310424 Route 209 Potential Slope Failure

Delaware and Dingman Twps., Pennsylvania

June 29, 2023

Terracon Project No. J6215080

Prepared for:

Vanasse Hangen Brustlin, Inc.

Williamsburg, VA

Prepared by:

Terracon Consultants, Inc.

South Plainfield, New Jersey

Responsive ■ Resourceful ■ Reliable 1

REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT BACKGROUND

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

RETAINING WALLS

GENERAL COMMENTS

FIGURES

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the

GeoReport logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Responsive ■ Resourceful ■ Reliable 1

INTRODUC TION

Geotechnical Engineering Report

DEWA 310424 Route 209 Potential Slope Failure

Delaware Water Gap National Recreation Area

Delaware and Dingman Twps., Pennsylvania

June 29, 2023

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the repair of potential slope failures along Route 209 within the Delaware

Gap National Park between Delaware and Dingman Townships, Pennsylvania. The purposes of these services were to observe the condition of the slopes, investigate the subsurface soil conditions in specific area and provide potential recommendations for repairing the slopes. In addition, it is our understanding that the National Park Service (NPS) would also like to relocate portions of the McDade Trail closer to Route 209. Finally, there are several stormwater sewers culverts that traverse Route 209 and discharge on the east side of the road. The slope failures are generally located at the culvert discharge locations.

The field geotechnical engineering Scope of Services for this project included the advancement of eleven test borings (5 culvert borings and 6 wall borings) to depths ranging from approximately

18 to 50 feet below existing ground surface. Please note that culvert boring C-5 was eliminated based on discussion with the project team. However, NPS provided a geotechnical report that was prepared by the US Department of Transportation (USDOT) in February 2012 for a soldier pile wall that was installed in the area of Milepost 15.3 along Route 209 which is located immediately north of the proposed C-5 boring location. This report is included as part of this report.

Maps showing the site and boring locations are shown in the Site Location and Exploration

Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the boring logs and as separate graphs in the Exploration Results section.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration.

June 29, 2023 ■ Terracon Project No. J6215080

Responsive ■ Resourceful ■ Reliable 2

Item Description

Parcel Information The project is located within the Delaware Water Gap National Recreation

Area between Delaware and Dingman Twps., Pennsylvania.

Existing

Improvements Existing roadway and walking trail.

Current Ground Cover Asphalt within the roadway. The slopes generally consist of vegetation and various diameter trees.

Existing Topography

(from Google EarthTM)

The grades are variable ranging from elevation +380 feet to elevation +485 feet.

PROJECT BACKGROUND

The NPS has identified several areas of concern with respect to the stability of the slope along the east side of Route 209. The following is a list of areas provided by NPS.

■ Mile Post (MP)14.1 reinforced concrete pipe (RCP)

■ MP 15 RCP

■ MP 16.1 to 17.8 with specific slope failures at MP 16.8 – 18” RCP, MP 17.2 – 18” RCP and attention at 17.5 and 17.8. The Inlet at 17.5 does not appear to have an outfall and the slope is sluffing at 17.8.

On January 12, 2023, a site visit was performed with members of NPS, VHB and Terracon to observe the conditions and identify areas of concern where additional subsurface investigation consisting of test borings would be warranted.

GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs can be found in the

Exploration Results section and the GeoModel can be found in the Figures section of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Responsive ■ Resourceful ■ Reliable 3

Model Layer Layer Name General Description

Fill Silty sand with gravel to silty gravel with sand and poorly grade gravel with asphalt

2 Boulders Boulders

3 Gravel Clayey/silty gravel with sand to clayey gravel and poorly graded gravel with silt and sand

4 Sand Silty/clayey sand with gravel to silty sand and poorly graded sand with silt and gravel

Weathered Bedrock

Completely to highly weathered shale

6 Bedrock Shale

Special attention should be provided to the following specific conditions that were encountered in the borings.

■ Uncontrolled fill (Model Layer 1) was encountered in C-3, C-6, W-1 and W-3 through W-5 below the pavement and was approximately 1 to 4 feet thick.

■ A layer of loose sand (Model Layer 4) and loose gravel (Model Layer 3) was encountered in C-1, C-2, C-4, C-6 and W-4 at depths of approximately 4 to 10 feet below the top of pavement and was approximately 2 to 5 feet thick.

■ A layer of boulders (Model Layer 2) was encountered in W-4 at a depth of approximately

26.5 feet and was approximately 10 feet thick.

■ The weathered bedrock (Layer 5) was distinguished from Layer 6 in that the drillers were able to advance the borehole through this layer without coring.

Please note that not all model layers were encountered in each boring performed for this study, nor were they generally encountered in the same order.

Groundwater Conditions

Groundwater and/or water seepage was encountered in four of the explorations performed for this study. Observed groundwater depth below ground surface at these locations is summarized in the following table:

Exploration

Approximate Depth to Groundwater below existing surface grades (feet)

C-3 18

C-6 18.5

Responsive ■ Resourceful ■ Reliable 4

W-1 28

W-4 9

Please note, however, that water seepage levels in the borings where coring was performed were difficult to observe due to the use of water as drilling fluid while coring. Zones of perched or trapped seepage may be encountered seasonally at higher elevations, particularly at the soil-fill interface. Fluctuations in groundwater level may occur because of seasonal variations in the amount of rainfall, runoff, and other factors that may differ from those present at the time the explorations were performed. Additionally, grade adjustments on and around the site, as well as surrounding drainage improvements, may affect the water table. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

GEOTECHNICAL OVERVIEW

Summary of Site Visit

As previously discussed, a site visit was performed on January 12, 2023 with members of NPS, VHB and Terracon to observe the conditions of the slopes in the general area of the downslope discharge of the stormwater culverts. These culverts generally consist of 18-inch reinforced concrete pipe (RCP). At the time of the site visit, spillways and/or rip rap were not present. It is our understanding that rip rap was installed at each of the pipe discharge locations on the slope in 2012 and 2013. However, overtime erosion of the slopes in these areas has allowed the rip-rap to migrate down the slopes. Since the rip-rap is no longer present, soil erosion/scour has continued unabated and is exacerbated during heavy rain events. The erosion/scour has developed undermining of the soil beneath the lead section of RCP in each area. As the area of undermining increases, the remaining soils can no longer support the weight of the pipe section and as a result that section of pipe will fall down the slope. The erosion/scour then continues to undermine the pipe and eventually the next section of pipe is exposed/undermined. In addition to the undermining of each pipe section, the unabated water is saturating the surrounding soils, causing additional material to slough off the slope which is widening each area of concern. This erosion condition is also removing the adjacent vegetation and trees, which act to stabilize the surficial soils of the slope. Based on the current conditions, the unabated water flow will continue to erode the slope over time. Therefore, it will be critical that the culverts/pipes be repaired to their original condition, spillways and/or rip rap should be installed to protect the slopes, as well as to divert the water away from the slope, followed by the restoration of the slopes in these areas.

In the area of MP 17 to 17.2, the NPS was also concerned that a potential slope failure was developing in this general area. Approximately 300 feet west of the area, there is a small waterfall.

The water enters the ground from a short distance east of the waterfall. It is not known where

Responsive ■ Resourceful ■ Reliable 5 this water travels. There was no visual evidence of water discharge along the slope. However, NPS is not sure if this water source is affecting the slope in this area.

Finally, the NPS is concerned that there are other sections of the slope that are failing beyond the areas identified above. Based on available mapping, the slopes in various areas ranged from 1:2 to steeper than 1:1, with a majority of the areas 1:1 and greater. In the areas where slopes were

1:1 and greater there was no evidence of longitudinal cracking along the pavement surface which would be indicative of a potential slope failure condition. Based on visual observations only, any sloughing in these areas is most likely the result of the type of material that is present within the slope. The soils are naturally trying to achieve their natural angle of repose, which is most likely

32 to 45 degrees (1:1.5 to 1:1), depending on the type of soils.

Geotechnical Considerations

Culverts

A total of five culvert borings were performed at locations identified by the project team. The results of these borings indicated relatively stable soil conditions consisting of sand and gravel .

A layer of natural loose sand and/or gravel soils (relative density based on N-values) was observed in four of the borings (C-1, C-2, C-4 and C-6) at depths ranging from approximately 4 to 10 feet below the pavement surface and was approximately 2 to 5 feet thick. The soils beneath this loose layer consisted of natural medium dense to very dense sand and gravel soils (relative density based on N-values). Since the loose soils were only encountered in the culvert borings, these loose soils are possibly the result of previous construction activities to install the culverts/RCP and/or erosion/scour of the soils at the face of the slope and are not indicative of a slope failure. Please note that based on the encountered materials at these locations, it was difficult to differentiate between the fill and natural soils. Further recommendations related to the replacement of the culverts are provided in subsequent sections of this report. Please note that boring C-3 was performed in an area where a small waterfall is located. The water currently enters the ground surface however, a discharge location has not been able to be identified. At this location, we did encounter groundwater at a depth of approximately 18 feet below the existing ground surface.

As discussed above, a geotechnical investigation was performed by the USDOT in the area of the soldier pile wall located immediately north of the C-5 location. A total of 5 borings were performed as part of this investigation. The borings extended to depths ranging from approximately 27 to 92 feet below the existing ground surface. Subsurface conditions generally consisted of sand and gravel with occasional layers of silt and varying percentages of cobbles and boulders. In addition, occasional layers of loose sand were encountered in each of the borings at various depths. Finally, uncontrolled fill was encountered in four of the boring below the pavement section and extended to depths ranging from 5 to 7 feet below the existing

Responsive ■ Resourceful ■ Reliable 6 pavement surface. The fill soils and/or near surface loose sands will not be suitable for support of new culvert structures. Recommendations to address these materials is provided in subsequent sections of this report. A copy of the USDOT report is included in the Supporting

Information section of this report.

Slope Failures

Slope failures typically occur when driving forces overcome resisting forces. The driving force is typically gravity and the resisting force is the slope materials shear strength. Some reasons for failures are:

■ Raising groundwater levels within the slope, which could potentially reduce the shear strength of the soils.

■ Reduction in the tensile strength of the soils. This is evident by cracking of the surface soils in an area of concern.

■ Where highly plastic clay soils are present within a slope area, under sustained loading these soils undergo constant deformation such as during freeze/thaw cycles, shrink/swell cycles, etc.

■ Leaching groundwater through the slope face.

■ Significant increases of loads at the top of the slope.

Any one of these items identified above on their own and/or in combination can contribute to a slope failure. As discussed above, there was no visual evidence within the road pavement and/or along the slope that would indicate a possible slope failure is occurring. Please note that it is very difficult to see the face of the slope in general due to the presence of vegetation. The test borings that were performed in limited areas along the top of the slope did not encounter soils conditions that could lead to the development of a slope failure. However, in the areas where the slopes become very steep (greater than 1:1), the exposed soils generally consisted of sand soils with limit fines which can lead to surficial sloughing, especially when exposed to rain and snow. In addition, in some of these steep locations, surface water and/or water from the culverts has begun eroding the surface of the slopes. This has resulted in the loss of vegetation on the slope. The vegetation acts as a natural protection of the slope similar to synthetic and/or metal netting/mesh.

The exposed soils on the face of the slopes are subject to natural raveling due to the type of soils present at the site (generally sand and gravel soils, with low percentages of fines that were present in the borings). These materials generally have a natural repose of approximately 32 to

45 degrees depending on the relative density of the soil, as well as the percentage of coarse material within the soil matrix. In addition, the exposed soils are more easily susceptible to wash out as a result of rain events, especially when there is no vegetation present. This is more indicative of a surficial sloughing condition then a true slope failure condition.

The following are systems that can be utilized to address the surficial sloughing

Responsive ■ Resourceful ■ Reliable 7

Slopes of 1:2 to 1:1

■ SlopeGrid-Slope Stabilization Grid

■ Steep Slope Erosion Control Mat

■ Erosion Control Matting such as Coir Mat 70

Slopes Greater Than 1:1

■ Steep Slope Erosion Control Mats

■ Erosion Control Matting such as Coir Mat 90

■ Soil Nailing

All these stabilization blankets, matting and/or geogrid can be installed on slopes where retaining walls or the placement of additional fill material in front of the slopes or walls is not possible due to space constraints, costs, etc. These materials can generally be rolled and/or placed as mats down the exposed slope in the areas where there is no vegetation present. These systems are then anchored in place with pins down the face of the slope. These materials can provide the protection that is necessary to avoid further sloughing of the slope face, as well as promote the growth of new vegetation further stabilizing the face of the slope.

Soil nailing is also an option to address the surficial sloughing of the steep slopes. Soil nailing generally consists of drilling and installing grouted slender reinforcing elements at a slight downward inclination as a grid pattern within the slope. The nails strengthen and stabilize the slope. The nails are typically installed by a design-build contractor. It should be noted that depending on the quantity of nails required for the intended slope, the cost of installation can be extremely expensive. In addition, the soil nail heads would be exposed at the surface. As a result, additional measures would need to be installed to cover the nail heads.

Walls

A total of six borings (W-1 to W-6) were performed at locations identified by the project team. In general, relatively dense soil conditions were observed within these borings. A layer of loose sand was observed in W-4 at a depth of approximately 6 feet and was approximately 2 feet in thickness. In addition, weathered shale bedrock was encountered in four of the locations (W-1, W-3, W-5 and W-6) below the natural soils at depths ranging from approximately 8 to 43 feet below the existing ground surface.

Responsive ■ Resourceful ■ Reliable 8

Retaining Walls

It is our understanding that NPS is looking for specific options to address the surficial sloughing that is occurring at locations along the east side of Route 209. In addition to addressing the surficial sloughing, portions of the existing McDade Trail, which is located parallel to the Route

209, may be relocated to a higher elevation adjacent to the road. As discussed above, in the areas of steep slopes especially with limited space at the toe of slope, the use of either matting and/or geogrid would be a more appropriate option to address the surficial sloughing in lieu of very tall retaining walls, especially in areas of limited space at the toe of slope.

However, in areas with no space constraints, it may be possible to utilize a retaining wall to remediate the surficial sloughing, as well as accommodate the relocation of portions of the trail.

The following types of retaining walls could be considered to address the surficial slope sloughing, as well as support the relocated trail:

■ Cast-in-place gravity walls

■ MSE walls

■ Gabion basket walls

■ Soldier pile and lagging walls

A general description of each wall is provided in a subsequent section of this report. Please note that once a wall location and type are finalized, additional geotechnical investigation will most likely be warranted in order to develop a complete design of the wall.

The General Comments section provides an understanding of the report limitations.

EARTHWORK

In the event that NPS elects to replace each of the culverts, earthwork that is anticipated would include stripping, excavation and backfill of the new culverts. The following sections provide recommendations that should be included as part of the earthwork specification that is prepared for the project. The following recommendations include critical quality criteria, as necessary, for the installation of the new culverts.

Stripping and Loose/Soft Soil Removal

Prior to any earthwork operations, the pavement should be saw cut and removed, followed by the removal of the existing culvert structures. The asphalt will not be suitable for reuse as structural fill, therefore the asphalt will need to be disposed properly offsite.

Responsive ■ Resourceful ■ Reliable 9

Following the removal of the existing culverts, the loose sand and/or gravel encountered in C-1, C-2, C-4 and C-6, which was generally on the order of 2 to 5 feet in thickness, should then be removed in its entirety from within, as well as two feet beyond each side of the new culvert/pipe.

A Terracon geotechnical engineer should be present to confirm that the unsuitable materials have been removed, and to assist the Contractor in limiting the removal of suitable native materials.

Excavations

As a minimum, temporary excavations should be sloped or braced, as required by Occupational

Health and Safety Administration (OSHA) regulations, to provide stability and safe working conditions. The contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations, as required, to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, State and federal safety regulations, including the current OSHA

Excavation and Trench Safety Standards.

Reuse of Materials

Soil materials generated during the excavation for the replacement culverts are expected to consist of sand and gravel. These materials would be suitable for reuse as compacted structural fill, provided the material is at a moisture content suitable for compaction, free of any deleterious materials and generally has a maximum particle size of 6 inches.

Imported Fill Materials

In the event that imported fill is needed to complete the backfill of the culvert, we recommend that the material consist of inorganic, readily compactable, well-graded granular soils with no more than 15 percent fines (no more than 15 percent passing the No. 200 sieve). Additionally, we recommend excluding gradations greater than 6 inches. The moisture content of the fill material should be controlled by wetting, aeration, or blending, as necessary to achieve the required compaction. Typically, this requires maintaining moisture contents to within approximately 2 to 3 percent of the optimum moisture content.

Backfill Placement

Structural fill should be installed in controlled layers uniformly compacted to at least 95 percent of the fill material’s maximum dry density, as determined by ASTM D1557 Test Procedures. The layer thickness should be adjusted as needed depending on the type of compaction equipment used and the condition of the fill materials at the time of construction, but should be no greater than 12 inches in loose thickness. It should be expected that thinner lifts will be required to achieve the required compaction in confined areas where portable compaction equipment is used.

Responsive ■ Resourceful ■ Reliable 10

Groundwater

Groundwater and/or water seepage at the culvert locations was only encountered in C-3 at a depth of approximately 18 feet below the existing ground surface. Zones of perched or trapped seepage may be encountered at higher elevations, particularly at the soil-fill interface. The contractor should therefore be prepared to provide dewatering equipment as needed to maintain relatively dry excavations.

RETAINING WALLS

In general, most of the slopes along the road are at 1:1 and steeper, are on the order of 30 to 40 feet in height and have limited space at the toe of slope prior to reaching the Delaware River.

Retaining walls, such as cast-in-place gravity, MSE and gabion, are most likely not an option to address the surficial sloughing in these hill fill areas. In these areas, matting, geogrid, erosion blankets, etc. are most likely option to address the face of the slope. However, in areas where slope heights are on the order of 10 to 20 feet, as well as the presence of sufficient space at the toe of the slope (20 to 30 feet or more), the use of a retaining wall could be installed to address the surface of the slope. This is especially true in areas where the McDade Trail may be relocated to higher elevation adjacent to Route 209.

This report identifies wall alternatives that can be implemented in the study area based on the subsurface information identified in the limited borings that were conducted. The feasibility of implementing the wall alternatives identified below will be highly contingent on geometric space constraints and costs to construct these walls. If a retaining wall is deemed the best solution to address surficial sloughing of a specific section of slope and/or the relocation of the trail, additional subsurface investigations may be warranted, including additional topographic surveying to better define the geometry of the wall.

Cast-in-Place Concrete Gravity Walls

These walls consist of steel reinforced concrete that retains the soil by gravity. A typical wall contains large cantilever foundations that extend several feet behind the wall. These walls can be designed for heights ranging from 10 to 20 feet or greater. However, the higher the wall, the greater the length of the cantilever foundation. As a result, sections of Route 209 would need to be removed to facilitate construction. We have provided some preliminary design bearing pressures for this type of wall in the event that this type of wall addresses the needs of NPS.

Mechanically Stabilized Earth (MSE) Walls

MSE is a composite structure consisting of alternating layers of compacted backfill and soil reinforcement elements that are fixed to a wall face. The reinforcing elements typically consist of

Responsive ■ Resourceful ■ Reliable 11 soil reinforcement extending approximately 0.7H of the height of the wall. As an example, if the height of the wall is 20 feet, the reinforcement would extend a minimum of 14 feet behind the wall.

MSE walls are normally designed at the time of construction by the wall manufacturer or by an engineer retained by the earthwork contractor, since the various MSE wall system designs are proprietary. As discussed above, this type of wall would be best suited for slope areas where there is sufficient space at the bottom of the slope in order to facilitate the construction of this wall.

With this type of wall construction, removal of portions of Route 209 would be required to facilitate the construction of the wall elements.

Gabion Basket Walls

Gabion basket walls consist of metal wire baskets filled with varying sizes of broken rock. The walls should be designed in accordance with the manufacturers guidelines and should include appropriate filter fabric to prevent clogging of the baskets with backfill material, as well as a drainage system as discussed below for all wall types. This type of wall is best suited for wall heights on the order of 5 to 10 feet.

Soldier Pile and Lagging

This type of wall consists of either driven or drilled in steel I-beams with pre-cast concrete planks are installed within the webs of the I-beams. The embedment of the I-beams is dependent on the height of wall, but it is typically 1.3H to 1.5H of the exposed face. For wall faces greater than 15 feet, a tie-back and waler system will need to be installed. If tie-backs are required, sections of

Route 209 may need to be removed in order to facilitate the installation of the tie-backs. This type of wall could address most of the slope areas, however these walls can be costly and as result, may preclude their use for slope repair and/or the relocation of the trail.

Typical Wall Foundation Design Parameters

For the gravity, MSE and gabion walls, if the wall areas have been prepared in accordance with the requirements noted in Earthwork, the following preliminary design parameters are applicable for shallow foundations.

Shallow Foundation Design Recommendations

Maximum Net Allowable Bearing Pressure, Soil 1,2

4,000 psf

Maximum Net Allowable Bearing Pressure, Rock 10 tsf

Minimum Embedment below

Finished Grade for frost protection

42 inches

Estimated Total Settlement from Structural Loads 1 inch

Responsive ■ Resourceful ■ Reliable 12

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied.

2. Unsuitable or soft soils should be over-excavated and replaced per the recommendations presented in the Earthwork.

3. Rock bearing pressure must be field verified by a Terracon geotechnical engineer or geologist at all foundation locations. Localized areas of poor-quality rock that would not support a design bearing pressure of 10 tsf should be anticipated.

4. Foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footing, the thickness of compacted fill, and the quality of the earthwork operations.

5. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

Exterior foundations should be established a minimum of 42 inches below the proposed adjacent exterior grades, or deeper if required by the local building official, to provide protection from frost penetration.

Foundations should not be designed to bear partially on soil and partially on rock. Where this condition occurs, the rock should be over-excavated a minimum of 12-inches, backfilled with clean crushed stone (No. 57 stone or equivalent) and the soil bearing pressure utilized for design.

Shallow Foundation Construction Considerations

The base of foundation excavations should be free of water, loose soil, and loose or overblast rock materials before placing concrete. In addition, all foundations bearing in rock should be leveled to have no more than a 10 percent inclination. We recommend that the foundations bearing in soil be underlain by a layer of crushed stone (No. 57 stone or equivalent) or lean concrete approximately 6 inches in thickness to protect the native subgrade materials from disturbance. Concrete should be placed soon after excavating to reduce bearing soil disturbance.

Should the soils at the bearing level become wet, disturbed, or frozen prior to the placement of the crushed stone, or if unsuitable bearing soils are encountered at planned subgrade levels, the materials should be removed prior to placing concrete. As discussed above, a Terracon geotechnical engineer should be retained to observe the subgrade preparation activities, to provide guidance regarding any remedial earthwork required, and to evaluate the suitability of the subgrades to support the design foundation loads.

Lateral Earthwork Design Parameters

The following table provides preliminary design parameters that may be utilized for the design of the various walls. Please note that the excavation support systems should be designed by a professional engineer in the Commonwealth of Pennsylvania. The design should include an allowance for surcharge loads such as traffic, etc. Once the design is complete, Terracon should

Responsive ■ Resourceful ■ Reliable 13 be allowed to review the design to confirm that the appropriate design parameters have been utilized.

Description Value (at-rest condition)

Unit Weight – Fill (pcf) 115

Unit Weight – Loose Sand (pcf) 105

Unit Weight – Medium Dense to Dense Sand/Gravel

(pcf)

Unit Weight – Very dense Sand/Gravel (pcf) 130

Unit Weight – Weathered Shale (pcf) 140

Angle of Internal Friction, fill 28

Angle of Internal Friction, loose sand 28

Angel of Internal Friction, medium dense sand 32

Angel of Internal Friction, dense to very dense sand/gravel

Coefficient of Active Earth Pressure (Ka) 0.31

Coefficient of Passive Pressure Earth Pressure (Kp) 3.3

Coefficient of Earth Pressure At-rest (Ko) 0.47

Base Friction 0.5

Retaining Wall Drainage

The gravity walls and all MSE walls should be designed to include drainage (discussed below) so that hydrostatic pressure from precipitation and surface runoff is not permitted to develop behind the wall. In addition, all of the walls should also be designed to account for surcharge loads from traffic, landscaping, as well as temporary construction loads.

GENERAL COMMENTS

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration. Natural variations will occur between exploration point locations or due to the modifying effects of construction or weather.

The nature and extent of such variations may not become evident until during or after construction.

Terracon should be retained as the geotechnical engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Responsive ■ Resourceful ■ Reliable 14

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Our services and any correspondence or collaboration through this system are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client.

Reliance upon the services and any work product is limited to our client, and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either expressed or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly impact excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing.

Site safety, and cost estimating including, excavation support, and dewatering requirements/design are the responsibility of others. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

Responsive ■ Resourceful ■ Reliable

FIGURES

Contents:

GeoModel (2 pages)

ATTACHMENTS

E le va ti o n

M

S L

(f ee t)

NOTES:

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

C-1

C-2 C-3

C-4

C-6

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

4081 Hadley Rd, Ste B

Pavement Rehabilitation

Route 209 | Dingman and Delaware, PA

South Plainfield, NJ

Terracon Project No. J6215080

GeoModel

LEGEND

First Water Observation

The groundwater levels shown are representative of the date and time of our exploration. Significant changes are possible over time.

Water levels shown are as measured during and/or after drilling. In some cases, boring advancement methods mask the presence/absence of groundwater. See individual logs for details.

Clayey/Silty gravel with sand to clayey gravel and poorly graded gravel with silt and sand3

Silty/Clayey sand with gravel to silty sand and poorly graded sand with silt and gravel4

Completely to highly weathered shale5

Asphalt Aggregate Base Course

Silty Sand with Gravel

Silty Gravel with Sand

Poorly-graded Gravel with Silt and Sand

Poorly-graded Sand with Silt and Gravel

Highly Weathered Shale Weathered Rock

Silty Sand Boulders and Cobbles

Fill Clayey Sand

Well-graded Sand with Silt and Gravel

Clayey Sand with Gravel

Model Layer General DescriptionLayer Name

Silty sand with gravel to silty gravel with sand and poorly graded gravel with asphalt1

Boulders2

6 Shale

Gravel

Sand

Weathered Bedrock

Fill

Boulders

Bedrock

14.5

28.4

18.5

E le va ti o n

M

S L

(f ee t)

NOTES:

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

W-1

W-2

W-3

W-4

W-5

W-6

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

4081 Hadley Rd, Ste B

Pavement Rehabilitation

Route 209 | Dingman and Delaware, PA

South Plainfield, NJ

Terracon Project No. J6215080

GeoModel

LEGEND

First Water Observation

The groundwater levels shown are representative of the date and time of our exploration. Significant changes are possible over time.

Water levels shown are as measured during and/or after drilling. In some cases, boring advancement methods mask the presence/absence of groundwater. See individual logs for details.

Clayey/Silty gravel with sand to clayey gravel and poorly graded gravel with silt and sand3

Silty/Clayey sand with gravel to silty sand and poorly graded sand with silt and gravel4

Completely to highly weathered shale5

Asphalt Aggregate Base Course

Fill Silty Sand with Gravel

Sandy Silt Poorly-graded Sand

Silty Gravel with Sand Silty Sand

Weathered Rock Poorly-graded Gravel with Silt and Sand

Shale Concrete

Poorly-graded Gravel with Sand

Highly Weathered Shale

Model Layer General DescriptionLayer Name

Silty sand with gravel to silty gravel with sand and poorly graded gravel with asphalt1

Boulders2

6 Shale

Gravel

Sand

Weathered Bedrock

Fill

Boulders

Bedrock

9.5

36.5

2.5

9.5

9.5

Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2

EXPLORATION AND TESTING PROCEDURES

Field Exploration

Number of

Locations

Type of Exploration

(Borings/Test Pits) Explored Depth (feet)

Location

5 Borings 28 to 30 Culverts

6 Borings 18 to 50 Walls

1. Below pavement surface

Boring Layout and Elevations: The borings were located in the field by Terracon. Elevations were obtained from topographic plans provided by VHB. If elevations and a more precise boring layout are desired, we recommend borings be surveyed following completion of fieldwork.

Subsurface Exploration Procedures: We advanced the borings with a truck-mounted rotary drill rig using hollow stem continuous flight augers. Four samples were obtained within in the upper 10 feet of each boring. In the split barrel sampling procedure, used at the site, a standard 2-inch outer diameter split barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the middle 12 inches of a normal 24-inch penetration is recorded as the Standard Penetration Test

(SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. The rock core samples were obtained with a NQ-size rock coring equipment. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, all borings were backfilled after their completion. Pavements were patched with cold-mix asphalt.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a geotechnical engineer. Our exploration team prepared field boring logs as part of the drilling operations. Final boring logs were prepared from the field logs. The final boring logs represent the geotechnical engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests to understand the engineering properties of the various soil strata, as necessary, for this project. Procedural standards noted below are for reference to methodology in general. In some cases, variations to methods were applied because of local practice or professional judgment. Standards noted below include reference to other, related standards. Such references are not necessarily applicable to describe the specific test performed.

Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2

■ ASTM D2216 Standard Test Methods for Laboratory Determination of Water (Moisture)

Content of Soil and Rock by Mass

■ ASTM D422 Standard Test Method for Particle-Size Analysis of Soils

The laboratory testing program included examination of soil samples by an engineer. Based on the material’s texture and plasticity, we described and classified the soil samples in accordance with the Unified Soil Classification System.

SITE LOCATION AND EXPLORATION PLANS

Site Location (2 pages)

Exploration Plan (3 pages)

Note: All attachments are one page unless noted above.

SITE LOCATION

DEWA 310424- Pavement Rehabilitation of Highway 209 ■ Dingman and Delaware, PA June 29, 2023 ■ Terracon Project No. J6215080

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY

QUADRANGLES INCLUDE: EDGEMERE, PA (1/1/1992), MILFORD, PA (1/1/1995),

LAKE MASKENOZHA, PA (1/1/1995) and CULVERS GAP, NJ (1/1/1997).

SITE

SITE LOCATION

DEWA 310424- Pavement Rehabilitation of Highway 209 ■ Dingman and Delaware, PA June 29, 2023 ■ Terracon Project No. J6215080

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY

QUADRANGLES INCLUDE: MILFORD, PA (1/1/1995).

SITE

EXPLORATION PLAN

DEWA 310424- Pavement Preservation and Rehabilitation of Highway 209 ■ Dingman, PA June 29, 2023 ■ Terracon Project No. J6215080

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

AERIAL PHOTOGRAPHY PROVIDED

BY MICROSOFT BING MAPS

DEWA 310424- Pavement Preservation and Rehabilitation of Highway 209 ■ Dingman, PA

June 29, 2023 ■ Terracon Project No. J6215080

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

DEWA 310424- Pavement Preservation and Rehabilitation of Highway 209 ■ Dingman, PA June 29, 2023 ■ Terracon Project No. J6215080

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

0 2 4 6 8 10 12 14 16 18 20

0 2 4 6 8 10 12 14 16 18 20

N=42

N=53

N=45

N=7

N=8

N=21

AR-28.0 Ft.

5.1

4.8

C-1

%w

N=19

N=13

N=14

N=36

BT-18.0 Ft.

W-5

%w

W-5 to C-1

Subsurface Profile

X X

E le v a ti o n

F e e t)

Facilities | Environmental | Geotechnical | Materials

Asphalt Aggregate Base Course

Silty Sand with Gravel

Silty Gravel with Sand

Poorly-graded Gravel with Silt and Sand

Poorly-graded Sand with Silt and Gravel

Highly Weathered Shale

Weathered Rock Concrete Fill

South Plainfield, NJ

4081 Hadley Rd, Ste B

Pavement Rehabilitation

Route 209 | Dingman and Delaware, PA

Terracon Project No. J6215080

Notes

Sampling (See General Notes)

Distance Along Baseline - Feet

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

Water Level Reading at time of drilling.

Water Level Reading after drilling.

Water Level Observations

Moisture Content

%w

C-1

Borehole Lithology

Borehole Termination Type

Explanation

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PL

Material Legend

0 5 10 15 20 25 30 35 40 45

0 5 10 15 20 25 30 35 40 45

N=63

N=30

N=15

N=11

N=7

N=11

N=48

N=48

BT-30.0 Ft.

12.3

C-2 %w

N=9

N=10

N=5

N=16

N=26

N=31

N=40

N=17

AR-28.4 Ft.

6.5

C-3 %w

C-3 to C-2

Subsurface Profile

X X

E le v a ti o n

F e e t)

Facilities | Environmental | Geotechnical | Materials

Asphalt Aggregate Base Course

Silty Sand with Gravel

Silty Gravel with Sand Silty Sand

Boulders and Cobbles Fill Clayey Sand

South Plainfield, NJ

4081 Hadley Rd, Ste B

Pavement Rehabilitation

Route 209 | Dingman and Delaware, PA

Terracon Project No. J6215080

Notes

Sampling (See General Notes)

Distance Along Baseline - Feet

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

Water Level Reading at time of drilling.

Water Level Reading after drilling.

Water Level Observations

Moisture Content

%w

C-2

Borehole Lithology

Borehole Termination Type

Explanation

Borehole Number

Liquid and Plastic Limits

AR

BT

0 2 4 6 8 10 12 14 16 18 20 22 24

0 2 4 6 8 10 12 14 16 18 20 22 24

N=33

N=17

N=7

N=17

N=24

N=35

N=35

N=20

BT-30.0 Ft.

3.4

C-4 %w

N=25

N=20

N=12

N=24

BT-18.0 Ft.

13.6

W-6 %w

W-6 to C-4

Subsurface Profile

X X

E le v a ti o n

F e e t)

Facilities | Environmental | Geotechnical | Materials

Asphalt Aggregate Base Course

Silty Sand with Gravel

Well-graded Sand with Silt and Gravel

Silty Gravel with Sand

Silty Sand Highly Weathered Shale

Shale

South Plainfield, NJ

4081 Hadley Rd, Ste B

Pavement Rehabilitation

Route 209 | Dingman and Delaware, PA

Terracon Project No. J6215080

Notes

Sampling (See General Notes)

Distance Along Baseline - Feet

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

Water Level Reading at time of drilling.

Water Level Reading after drilling.

Water Level Observations

Moisture Content

%w

C-4

Borehole Lithology

Borehole Termination Type

Explanation

Borehole Number

Liquid and Plastic Limits

AR

BT

EXPLORATION RESULTS

Boring Logs (C-1 to C-4, C-6 and W-1 to W-6)

Grain Size Distribution (5 pages)

448.6

447.5

445.5

443.5

439.5

436.5

426.5

421.5

ASPHALT, 11"

DENSE GRADE AGGREGATE, 13"

SILTY SAND WITH GRAVEL (SM), gray, dense

SILTY GRAVEL WITH SAND (GM), gray, very dense

POORLY GRADED GRAVEL WITH SILT AND SAND (GP-GM), gray, loose to dense

POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), gray, loose

SILTY SAND WITH GRAVEL (SM), gray, medium dense

COMPLETELY WEATHERED SHALE, gray

HIGHLY WEATHERED SHALE, dark gray

Auger Refusal at 28 Feet

Boring Log No. C-1

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

M o d el

L ay er

5.1

4.8

0.9

2.0

4.0

6.0

10.0

13.0

14.5

23.0

28.0

19-20-22-21 N=42

16-20-33-34 N=53

34-21-24-16 N=45

8-3-4-3 N=7

6-3-5-8 N=8

9-9-12-35 N=21

41-17-28-50/4" N=45

50/1"

50/0"

Abandonment Method Boring backfilled with Auger Cuttings Surface capped with asphalt

Advancement Method

HSA

Hammer Type Automatic

Driller Nick P.

Logged by

NP

Boring Started 02-24-2023

Boring Completed 02-24-2023

4081 Hadley Rd, Ste B

Drill Rig Acker Rebel

Pavement Rehabilitation

South Plainfield, NJ

Route 209 | Dingman and Delaware, PA

Terracon Project No. J6215080

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Notes

Water Level Observations Groundwater not encountered

S am pl e

T yp e

W at er C o n te n t

Elevation: 449.5 (Ft.) +/-

See Exploration PlanLocation:

Latitude: 41.2750° Longitude: -74.8410°

Depth (Ft.)

R ec o ve ry

In

Fi el d T es t

R es u lt s

445.5

444.5

436.5

433.5

428.5

416.5

ASPHALT, 12"

DENSE GRADE AGGREGATE, 12"

SILTY SAND WITH GRAVEL (SM), brown, medium dense to very dense

SILTY GRAVEL WITH SAND (GM), brown, loose

SILTY SAND (SM), brown, medium dense

SILTY GRAVEL WITH SAND (GM), brown to gray, dense to very dense

Boring Terminated at 30 Feet

Boring Log No. C-2

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

M o d el

L ay er

12.3

1.0

2.0

10.0

13.0

18.0

30.0

25-32-31-27 N=63

13-18-12-11 N=30

9-10-5-7 N=15

2-2-9-5 N=11

2-5-2-3 N=7

5-4-7-6 N=11

50/5"

38-27-21-22 N=48

21-22-26-36 N=48

Abandonment Method Boring backfilled with Auger Cuttings Surface capped with asphalt

Advancement Method

HSA

Hammer Type Automatic

Driller Nick P.

Logged by

NP

Boring Started 02-23-2023

Boring Completed 02-23-2023

4081 Hadley Rd, Ste B

Drill Rig Acker Rebel

Pavement Rehabilitation

South Plainfield, NJ

Route 209 | Dingman and Delaware, PA

Terracon Project No. J6215080

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Notes

Water Level Observations Groundwater not encountered

S am pl e

T yp e

W at er C o n te n t

Elevation: 446.5 (Ft.) +/-

See Exploration PlanLocation:

Latitude: 41.2758° Longitude: -74.8407°

Depth (Ft.)

R ec o ve ry

In

Fi el d T es t

R es u lt s

446.7

418.6

GRAVEL, 4"

FILL - , silty sand with gravel, gray

CLAYEY SAND (SC), yellow brown, medium dense

SILTY SAND WITH GRAVEL (SM), gray, medium dense

SILTY GRAVEL WITH SAND (GM), gray to brown, medium dense

SILTY SAND WITH GRAVEL (SM), brown, dense

SILTY SAND (SM), gray, medium dense

SILTY GRAVEL WITH SAND (GM), with cobbles and boulders, gray

Spoon Refusal at 28.4 Feet

Boring Log No. C-3

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L…