140P2022R0045-0003_Att01a-Q03_ACAD151309B_GeotechnicalFinalDesignReport_211201_0003.pdf

Prepared for the

NATIONAL PARK SERVICE

Denver Service Center

12795 W. Alameda Parkway, Lakewood CO 80225

GEOTECHNICAL FINAL DESIGN REPORT FOR THE

PROPOSED MAINTENANCE FACILITIES AND THE NEW

HQ/ADMINISTRATIVE FEATURES AT MCFARLAND HILL

HQ, APPA-151309B, BAR HARBOR, MAINE

Prepared by

412 Mt. Kemble Avenue, PO Box 1946 Morristown, New Jersey 07962-1946

December 2021

Geotechnical Final Design Report for the Maintenance Building and HQ/Administrative Facilities, Bar Harbor, ME

TABLE OF CONTENTS

Page

Executive Summary

1.0 Introduction

1.1 Project Description

1.3 Scope of Work

2.0 Subsurface Investigation and Testing

2.4 Laboratory Testing Program

2.5 Regional Geology of the Project Area

2.6 Site Specific Subsurface Conditions

2.7 Groundwater

3.0 Geotechnical Evaluations and Engineering Analysis

3.1 Foundations

3.2 Floor Slab

3.3 Retaining Walls

3.2.1 Geogrid Supported Retaining Wall

3.2.2 Gabion Walls

3.4 Utility Trench

3.5 Parking Area Pavement

3.6 Site Infiltration Characterizations

3.7 Seismic Considerations

3.8 Evaluations of Corrosion and Sulfate attack Potential

3.9 Construction Considerations

4.0 Conclusions and Recommendations

5.0 Limitations

6.0 References

TABLE OF CONTENTS (CONTINUED)

Figures Figure 1 Site Location Plan Figure 2 Boring and Infiltration Tests Location Plan Figure 3 Geogrid Supported Wall – Typical Section

Appendices Appendix A Boring Logs Appendix B Phase 1 Boring Logs and Lab Results Appendix C Laboratory Test Results Appendix D Geotechnical Design Calculations and Evaluations Appendix E USDA NRCS Site Soil Map Appendix F USGS Seismic Design Site Specific Map

Tables Table 1 Coordinates and Elevations of Boreholes Drilled During this Investigation Table 2 Laboratory Testing Assignment Table 3 Geotechnical Design Parameters Table 4 Top of bedrock elevations within the maintenance building footprint Table 5 Permeable (Porous) Pavement Section Table 6 Conventional Pavement Section Table 7 USGS Seismic Report for Seismic Design Parameters

WSP USA 1 December 2021

Executive Summary National Park Service (NPS) requested WSP to conduct a geotechnical investigation, evaluate the data, and conduct geotechnical design services, for the proposed New Maintenance Facility, and New Headquarters/Administrative facilities at McFarland Hill Headquarters in Bar Harbor, Maine.

This report presents a factual account of the subsurface conditions based on 23 boreholes (11 conducted during this investigation and 12 borings conducted during Phase 1 activities), laboratory test results, and our geotechnical analysis and geotechnical evaluations, including conclusions and recommendations. The proposed improvements will include an approximate 25,000 square foot new maintenance building, parking lots, and approximately 1,800 linear feet of retaining walls with heights that range from five to fifteen feet. Existing site elevations range from +385 (near Carriage road on the bottom of the western slope of the Site) to +435 ft amsl (near the existing maintenance building).

Geologic units observed within the project area consist of bedrock granite overlain by glacial deposits and locally, fill material. Data collected during this investigation indicates four (4) different strata with different depths/elevations below the existing ground surface, which were described as 1) Fill, A discontinuous layer consisting of sand, silt, gravels and locally boulders to an average depth of 4 feet below the existing grade (Stratum 1), underlain by 2) Sand, Silty/Clayey Sand, Gravels and Cobbles (Stratum 2), underlain by, or horizontally and vertically transmitting into 3) Silty Clay and Clayey Silt, (Stratum 3), over bedrock Granite, massive, strong to very strong hard and sound (Stratum 4). Characteristics of these geotechnical/geological units are discussed in Section 2.6.

Based on the wetness of the samples and observations during drilling, groundwater, in the form of perched water, is anticipated to be between four (4) feet and greater than 18 feet below the existing grade corresponding to an approximate elevation between El. +405 and El. +425 feet. However, some boreholes were dry. Groundwater is in the form of storm water due to relatively impervious or low infiltration rates. Therefore, it is strongly controlled by storm events and is expected to fluctuate depending on climatic factors, surface drainage conditions, as well as storm influences and other factors.

Based on the data collected during this exploration and evaluations, we recommend a shallow foundation system consisting of spread footings, or continuous wall foundations for the proposed new buildings. The foundations could rest on Stratum 2 and Stratum 3 soils and bedrock granite (Stratum 4), a minimum four (4) feet below the existing grade. Depending on the foundation depth and subgrade, the recommended allowable bearing capacities range between 3.0 and 6.0 tons per square foot (tsf). Settlements under these magnitudes of stress would be negligible. In Section 3.2, recommended foundation depths/elevations were provided for feasible foundation construction and for selecting future building locations/heights.

This study recommended a slab-on-grade floor support for all new structures and under-slab drainage, as well as subgrade preparations (see Section 3.3) for the satisfactory performance of the structures’ floors. For the design of the floor slab a modulus of subgrade reaction of 130 pounds per cubic inch (pci) (using 1-foot by 1-foot plate) is recommended.

The proposed improvements at MacFarland Hill will include retaining walls to accommodate new Site grading. Geogrid supported, mechanically stabilized earth (MSE) style with heights between 5

WSP USA 2 December 2021 and 15 feet, and gabion basket walls (for wall heights less than 5 feet), are proposed and evaluated in this report. Geogrid supported MSE walls are recommended to accommodate proposed fill areas located on the western slope of the project Site. Wall heights here will range between 5 and 15 feet and will support BMP drainage basins and parking areas. The proposed geogrid supported wall should be supported on a gravel leveling pad bearing on compacted Stratum 2 or 3 soil. An embedded depth of four feet is recommended to accommodate frost penetration depths in Mount Desert, Maine (MaineDOT 2003). Subgrade below the wall should be proof rolled to 95% of the soil’s dry density as observed in ASTM D 1557. If bedrock is encountered during retaining wall excavation, a levelling course of gravel fill (3/4 inch stone) may be placed to create a platform and the wall may rest on this fill (i.e. bedrock does not need to be excavated to achieve a four foot embedment depth).

The reinforced zone of the Geogrid Supported wall should be 0.7 H or a minimum eight feet (based on AASHTO LFRD) and constructed using select granular backfill material (USCS symbols GP, GW, SP, or SW) with a maximum geogrid spacing of 1.5 feet. Excavated material can be reused as backfill in the reinforced zone, provided that fines content (silt and clay) is no greater than 10%.

Backfill material should be placed and compacted in 9-inch lifts and compacted to 95% of the soil’s dry density (ASTM D 1557). Excavated fill should not be wet or saturated. If saturated material is encountered, the material should be dried or mixed with dry granular material to achieve the desired compaction density.

Gabion basket retaining walls, less than 5 feet in height, are proposed on the east side of the Site.

Gabion baskets should be embedded at least 1 foot below ground surface and consist of wire mesh gabion baskets, battered 6 degrees from vertical, leaning towards the top of the wall. The gabion wall shall consist of two courses of gabion baskets. The baskets should have a minimum base width if on the order of minimum 70% the wall height (minimum 3.5 feet for five foot high wall, or two 3x3x3 foot baskets, providing a six foot base width). Rock fill in the baskets will between 4 and 8 inches in diameter with a D50 of 6 inches and geotextile fabric should be placed directly behind the gabion basket.

The baskets should bear on compacted foundation soil (Stratum 2 or 3) below a leveling course of gravel or crushed stone. Foundation soil should be proof rolled to minimum 95% of the soil’s dry density (as in ASTM D 1557).

Four borings (TR-1 and TR-4) were conducted to evaluate the depth to bedrock and characteristics of the overlaying subsurface soils that may be excavated for a proposed utility trench alignment, located from Rt 233 to the proposed new headquarters building. Material encountered in these borings is considered excavatable up to depths of 10.8 feet below existing ground surface.

New parking pavement was designed using “permeable pavement design” and conventional pavement sections. The following pavement box section was evaluated and recommended for porous (permeable Pavement).

WSP USA 3 December 2021

And a pavement design for the new pavement for a heavy duty parking lot and access road was developed and recommended as follows:

Field infiltration tests showed all potential development sites, belong to Hydrological Soil Group (HSG) “D”. With a coefficient of infiltration being less than 0.05 inches per hour (in/hr.), The Site displays poor infiltration characteristics and should be considered during BMP design.

Depending on the selected locations, the area restrictions, and utilities surrounding the site, sheeting and shoring would be required for excavation safety and stability. Soldier piles with timber lagging may be used as a feasible excavation support system. Depending on the height of the excavation and the difficulties in drilling into bedrock granite, it is likely tie-back/ground anchors would be required to maintain stability and to control lateral movements. Design parameters for the excavation support system were provided in Table 5. For development at or near the existing Headquarters/Administrative Facilities, for the safety of the adjacent structures and utilities, underpinning would be required if the excavation is below the existing foundation area and if the distance is less than 20 feet. An economical underpinning can be designed and incorporated using vertical or raked micro piles penetrating into bedrock granite or reinforced concrete panels with a maximum opening length of 8 feet constructed in alternating segments.

The excavated soils will include clay, silt, fill, as well as sand. Silt and clay in fill (Stratum 3) are present in layers and both are unsatisfactory soils for structural and common fill use. Therefore, they may be separated during excavation and be disposed of or used for landscaping. The sand fraction of the fill can be used for common fill purposes. The suitability of the excavated material for utilities backfill will need to be checked against the manufacturer’s or utility’s specifications.

Bedrock granite cannot be removed by conventional excavation tools and requires blasting or the use of similar volume expansion agents. Therefore, costly and time-consuming bedrock excavation should be avoided.

Material Thickness (inches) Superpave-HMA 4 Open graded friction course Aggregate Base 12 Total Thickness 16 Existing subgrade Uncompacted

Material Thickness (inches)

Superpave-HMA 4 Surface course, 12.5mm

Aggregate Base 8 Total Thickness 12 Existing subgrade Compacted to 92% (ASTM D 698)

WSP USA 4 December 2021

1.0 Introduction

On behalf of the National Park Service (NPS), WSP USA conducted a geotechnical investigation for new facilities at the McFarland Hill Headquarters in Acadia National Park, Bar Harbor, Maine. The following report provides the results of a geotechnical subsurface investigation program and geotechnical design recommendations for new foundations, retaining walls, pavement, a utility trench, and soil infiltration.

Geotechnical recommendations in this report are based on subsurface conditions observed in 11 boreholes, conducted in September 2021, and 12 boreholes drilled during Phase 1 geotechnical activities in June 2019 (Louis Berger 2019). Borings were inspected and logged by WSP USA and geotechnical laboratory testing was conducted on representative soil samples by Terrasense Inc. in Totowa NJ. Design recommendations in this report include recommendations for new retaining walls and foundations, recommendations for subgrade preparations, earthwork preparation, pavement layer thicknesses, foundation design recommendations, as well as construction considerations for earthwork.

1.1 Project Description

MacFarland Hill in Acadia National Park is located off State Route 233, approximately two (2) miles west of Bar Harbor, in Hancock County, Maine (Figure 1). The existing facilities at MacFarland Hill consist of a Park Headquarters, housing, and maintenance facilities.

The proposed improvements will include an approximate 25,000 square foot new maintenance building, parking lots, and approximately 1,800 linear feet of retaining walls with heights that range from five to fifteen feet.

1.3 Scope of Work

The scope of work for this project included conducting geotechnical borings and laboratory testing of soil, a review of Phase 1 borings, laboratory tests, and geotechnical evaluations (Louis Berger 2019), a review of available geologic maps and information, develop subsurface stratification, depth to bedrock, depth to groundwater, geotechnical recommendations for foundations, retaining walls, floor support and subgrade preparations. In order to achieve these objectives, the following work was performed:

1. Retained a drilling contractor for 11 borings, collection of representative soil and rock samples, groundwater observations, and field testing (Standard Penetration Tests).

2. Provided full time field inspection services by a Professional Geologist for the borings, sampling and field tests.

3. Performed a laboratory testing program on representative soil samples obtained from the borings; consisting of grain size analysis, Atterberg limits tests, moisture content, and preliminary sulfate attack and corrosion assessment tests

Prepared this geotechnical report that includes the following:

a. A description of the regional geologic features of the project site and subsurface investigation performed for this project;

b. Estimated depths/elevations to bedrock which is hard and sound, and hard to remove

c. Engineering analysis and preliminary foundation recommendations for the new

Maintenance Building and Headquarters/Administrative facilities and parking areas.

WSP USA 5 December 2021

d. The results of the engineering evaluations and recommendations regarding the excavation, fill and earthwork, including:

· Generalized subsurface conditions, including depths to groundwater;

· Estimated settlements due to the new structure;

· Subgrade preparations for the foundations, and floor support;

· Recommended soil parameters for earthwork.

e. A discussion of construction-related issues, including:

· Excavation considerations, including the use of excavated materials;

· Subgrade preparation and backfill requirements;

· Protection of adjacent structures and utilities; and

f. Appendices that include, test boring logs, and laboratory test results.

WSP USA 6 Decmber 2021

2.0 Subsurface Investigation and Testing

A geotechnical exploration program, consisting of 11 boreholes to depths between 4.8 and 20.5 feet below ground, was implemented in September 2021. Results from these borings were combined with the 12 Phase 1 boring records (conducted by WSP in June 2019), and used to characterize the soil, depth to bedrock, and groundwater conditions around the Site.

Soil borings were performed by New England Boring Contractors using a Mobile B-53 rubber track drilling machine. Soil samples were obtained using techniques and equipment in general accordance with the American Society for Testing and Materials (ASTM) Standard Specifications, ASTM D6151-15: Standard Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil Sampling, and D1586 – Test Method for Penetration Test (SPT) and Split-barrel Sampling of Soils.

Representative samples were collected using a 1.5-inch inner diameter (I.D.) split-spoon SPT sampler driven with a 140 pound automatic hammer with a 30-inch drop. Blow counts were recorded in accordance with ASTM D1586 to determine the SPT resistance “N” values. Continuous representative soil samples were collected from ground surface to a depth of 12 feet, and then after every five (5) foot interval after. Borings conducted for the proposed utility alignment were conducted to at five foot intervals to 15 feet below ground or auger refusal.

The recovered split-spoon soil samples were visually classified and placed in protective glass jars, which were labeled with the project name and number, boring number, sample number, depth, and SPT blow counts. Boreholes were terminated at the interpreted top of bedrock elevation (determined based on drilling conditions and SPT).

A WSP Professional Geologist inspected the boring operations, logged the subsurface, and selected and collected samples for laboratory testing. Borehole coordinates and total drilling depths are presented in the below Tables 1 and locations are presented in Figure 2. Boring logs for the 11 boreholes drilled for this investigation are included in Appendix A and Phase 1 boring logs with laboratory results are included in Appendix B.

WSP USA 7 Decmber 2021

Table 1: Coordinates and Elevations of Boreholes Drilled During this Investigation

Borehole Date

Drilled Latitude Longitude Elevation (ft amsl)

Total Depth

(ft) B1-21 9/8/2021 44.373528° -68.259223° +432 4.8 B2-21 9/8/2021 44.373101° -68.259118° +433 8.3 B3-21 9/8/2021 44.372878° -68.258990° +434 8.8 B4-21 9/8/2021 44.372593° -68.259083° +428 7.5 B5-21 9/8/2021 44.373178° -68.259523° +432 8.5 B6-21 9/8/2021 44.374039° -68.260414° +410 20.5

TR-1 9/9/2021 44.375184° -68.260662° +443 17.0

TR-2 9/9/2021 44.374894° -68.260403° +437 17.0

TR-3 9/9/2021 44.374663° -68.260170° +435 17.0

TR-4 9/9/2021 44.374158° -68.259695° +433 17.0

TR-5 9/9/2021 44.373878° -68.259413° +431 10.8

B1 6/17/2019 44.374874 -68.260656 433 32.0 B2 6/18/2021 44.374356 -68.260239 424 27.0 B3 6/18/2021 44.373949 -68.260009 418 9.5 B4 6/18/2021 44.374257 -68.259909 433 22.8 B5 6/19/2021 44.373514 -68.259571 430 13.6 B6 6/19/2021 44.373249 -68.259179 433 8.6 B7 6/21/2021 44.374531 -68.258631 420 19.8 B8 6/21/2021 44.374652 -68.259601 437 20.2 B9 6/21/2021 44.374196 -68.258935 432 17.5 B10 6/20/2021 44.373087 -68.25938 433 12.0 B11 6/17/2021 44.37477 -68.258528 418 15.5 B12 6/20/2021 44.373679 -68.260162 410 13.3

2.4 Laboratory Testing Program

Representative soil samples were selected for laboratory analysis, including: sieve analyses (per ASTM D422), Atterberg limit testing (per ASTM D4318), moisture content (per ASTM D2216), soluble sulfate (per AASHTO T 290), chloride (per AASHTO T 291) and pH (per ASTM G 51).

Testing was conducted at TerraSense, LLC laboratories in Totowa, New Jersey.

Specifically, the following representative samples, listed in Table 2, were tested. Test results were combined with results from Phase 1 investigations conducted in 2019 and used to evaluate subsurface conditions at the Site. Lab results are included in Appendix C and results from 2019 are included with 2019 boring logs in Appendix B.

WSP USA 8 Decmber 2021

Table 2: Laboratory Testing Assignment Boring Sample Depth Atterberg Limit Testing

BH-1 S1 0-2

BH-2 S2 2-4

pH, Sulfate, Chloride

BH-2 S3 4-6

BH-3 S3 3-5

BH-3 S4 5-7

BH-4 S2 2-4

Sieve Analysis

BH-4 S4 6-8

BH-5 S4 6-8

BH-6 S2 2-4

BH-6 S3 5-7

BH-6 S5 9-11

BH-6 S6 15-17

TR-1 S3 10-12

TR-2 S2 5-7

TR-3 S3 10-12

TR-4 S2 5-7

2.5 Regional Geology of the Project Area

Acadia National Park is located on Mount Desert Island, the largest of several thousand islands along the New England coast. The island rises 1528 feet (466 meters) above a rocky shoreline with lakes and cliffs that attract many visitors. The oldest rocks on Mount Desert Island date to about 500 million years ago and were formed during the Cambrian Period, when sediments and volcanic ash piled up on the seafloor of the Iapetus Ocean. Over time, pressure transformed the buried sediment into mudstones interbedded with ash layers. During the plate collisions and mountain-building events of the early Paleozoic that began raising the Appalachians, high temperatures and pressures recrystallized and folded these mudstones into the Ellsworth Schist, a metamorphic rock with wavy layers of minerals, including dark green chlorite and lighter layers of quartz and feldspar.

Eventually, the Ellsworth Schist was brought to the surface by further tectonic activity through the Ordovician period. The next oldest are the sandstones and siltstones of the Bar Harbor Formation.

(Kaiser 2018).

According to Gilman, et all (1988), the youngest rocks include myriad granites and other igneous rocks between about 360 million and 420 million years old. The predominant granites, the Cadillac Granite and the Somesville Granite, exhibit rich pink hues due to an abundance of orthoclase feldspar. Some are more fine-grained, having cooled quickly, while others are larger-grained with

WSP USA 9 Decmber 2021 quarter-sized crystals, having cooled more slowly. There is also an igneous rock that has been described as “chocolate chip cookie dough-like” for its chunky appearance. This rock formed in a shatter zone, where the heat from intruding magma fractured the existing rock above, creating chunks that were encased in an igneous matrix. Those chunks are pieces of Ellsworth Schist and Bar Harbor sedimentary rocks. Around the same time, large volcanic dikes formed in the area, leaving telltale dark bands of diabase protruding through the lighter-colored granites. Extrusive volcanism, likely resulting from the ongoing collisions and subduction in the area at the time also spewed ash and lava, which became the rocks of the Cranberry Island Series.

During the Pleistocene glacial advances, the area was covered by enormous ice sheets: Wisconsin Glaciation. Most recently, the 1.5- to 3-kilometer (km) (.93 to 1.86 miles)thick Laurentide Ice Sheet expanded from Canada to cover the entire state and extended more than 450 km (279 miles) out on the then-exposed continental shelf. The glaciers eroded the mountains and cut broad U-shaped valleys. Materials carried at the base of the ice polished the mountains and left long scratches (striations) and crescent-shaped gouges (crescentic gouges) in many places. This episode, called the reached its maximum extent 18,000 years ago with its terminus far to the south of Maine. As the climate warmed, more ice melted in the warmer months than accumulated in the winter. Although ice continually flowed south from more northern portions of the ice sheet, the southern edge of the glacier began to recede, depositing material carried by the glacier. Accumulations of rock, gravel, and sand dammed valleys. Boulders carried 20 miles (32.19 km), or more were left behind by the melting ice. These glacial erratics are found in valleys and on mountaintops. A carpet of glacial debris was spread out upon the landscape.

Geologic units observed within the project area formed as a result of above summarized geologic processes are the glacial deposits over granitic rocks. Local fill, as discussed below was also observed as a result of relatively recent site development activities.

2.6 Site Specific Subsurface Conditions

Based on the information collected from 23 boreholes with laboratory testing, the Site consists of four (4) different strata at different depths/elevations below the existing ground surface. These strata are as follows:

Stratum 1- Fill, A discontinuous layer consisting of sand, silt, gravels and locally boulders to an average depth of 4 feet below the existing grade, Stratum 2 – Sand and Gravel

Stratum 3 - Clayey Sand and Sandy Clay with variable amount of gravels and cobbles

Stratum 4 - Bedrock Granite, massive, strong to very strong, hard and sound.

Depth to bedrock varies from as low to 4.8 feet below ground at the top of MacFarland Hill near the new proposed maintenance building and as deep as greater than 20 feet on the western slope. A summary of the subsurface conditions, including a brief description of the earth materials and geologic units identified in the record of borings, is presented below.

Stratum 1 Fill (Mostly granular, Sand, Gravels and Silt): A discontinuous layer of fill was observed in borings conducted in parking areas and near access roads. The Fill consisted of brown to gray to dark brown sand and gravel, lesser fractions of clay

WSP USA 10 Decmber 2021 and silt, and generally some gravels and occasional cobbles, and moist. The observed thickness of the fill is less than 5 feet, where present. The SPT resistance “N” values (ASTM Standard D1586) in this stratum ranged from 4 blows/foot to 12 blows/foot indicating generally loose compactness.

Laboratory tests conducted on selected representative fill sample indicated the following preliminary corrosivity data:

· Sulfate Content: <10 ppm

· Chloride Content: 33 ppm

· pH: 7.0

Stratum 2 Sand and Gravel (SM, SC, GM): Below fill (or below a thin layer of topsoil in areas not paved), a soil stratum, consisting of mostly granular soils of light to dark brown, olive brown sand (SM, less SP and SC) and gravel (GM); mixed with variable amounts of silt and clay was encountered in most boreholes. The observed thickness of this stratum is in the order of 10 feet, however it transits into the underlying silt and clay both horizontally and vertically. The SPT resistance “N” values (ASTM Standard D1586) in this stratum ranged from 18 blows/foot to more than 100 blows/foot with an average over 35 blows foot, indicating very dense compactness.

Laboratory tests conducted on selected representative sand and gravel soils indicated the following index, classification limits, and preliminary corrosivity data:

· Gravel Content (%): 20.4

· Sand Content (%): 42.9

· Fines Content (%): 36.7 to 37.9

· Sulfate Content: < 10ppm

· Chloride Content: < 10ppm

· pH: 7.3.

Stratum 3 Clayey Sand, Clay and Silt (SC, CL, ML): This stratum was observed in most boreholes underlying, or in between sand and gravel layers above granite bedrock. It has a thickness ranging from five (5) feet to 15 feet with an average 10 feet. This stratum is described as light brown, olive brown lean clay with transitions to sandy clay, silty clay or clayey silt, and moist. The SPT resistance “N” values (ASTM Standard D1586) in this stratum ranged from 22 blows/foot to more than 100 blows/foot with an average more than 30 blows/foot indicating very stiff-hard consistency. Clay/Silt generally transits into sand and gravel, likely representing the bottom of the glacial sediments.

Laboratory tests conducted on selected representative soils indicated the following index and classification limits:

· Moisture Content: 9.1 to 14.6

· Liquid Limit: 18 to 24

· Plastic Limit: 12 to 15

· Plasticity Index: 4 to 11

· Minimum Resistivity (k-Ohm): 10.1.

WSP USA 11 Decmber 2021

Stratum 4 Bedrock Granite: Approximately between 4.8 feet and 32 feet below the existing grade, bedrock granite was observed in most boreholes. Bedrock was cored during the Phase 1 investigation, and described as pink-white, light gray with back specks (i.e. biotite), upper parts fractured and jointed, slightly weathered, hard and sound granite. Core samples collected from representative boreholes indicated the Total Core Recovery (TCR) ranged from 83 to 100 percent. The Rock Quality Designation (RQD) ranged from 70 to 87 percent. These values indicate relative massive, sound rock with a “good” rock quality. Bedrock was encountered at the following elevations:

Boring ID Depth to Bedrock (ft bgs) Top of Bedrock Elevation (ft amsl) B1-21 4.8 +427.2 B2-21 8.3 +424.7 B3-21 8.8 +425.2 B4-21 7.5 +420.5 B5-21 8.5 +423.5 B6-21 9.7 +400.3

TR-5 10.8 +420.2

B3 9.5 +408.5 B4 22.8 +410.2 B5 13.6 +416.4 B6 8.5 +424.5 B7 19.75 +400.3 B8 21.2 +415.8 B9 17.5 +414.5 B10 5.5 +427.5 B12 13.35 +396.8

2.7 Groundwater

Site groundwater conditions were evaluated based on observations during drilling, the moisture content (wetness) of samples collected, and the water level measured inside the hollow stem augers during and after drilling. Groundwater, in the form of perched water, is anticipated to be between 4 feet and 18 feet below the existing grade, corresponding to approximate elevations between El.

+400.3 and El. +423.5 feet, with many boreholes not encountering groundwater (dry).

Groundwater was encountered in 2 of the 11 recently drilled borings in September 2021 at the following depths and elevations:

B6-21 at 9.7 feet bgs, El +400.3 B5-21 at 8.0 feet bgs, El. +424.0

Groundwater was encountered during June 2019 site investigations at the follow depths and elevations:

B1 at 15.0 feet bgs, El. +418.0 B2 at 18.5 feet bgs, El. +405.5 B3 at 9.0 feet bgs, El. +409.0 B5 at 6.5 feet bgs, El. +423.5

WSP USA 12 Decmber 2021

B11 at 9.4 feet bgs, El. +408.6 B12 at 5.0 feet bgs, El. +405.0

Groundwater is in the form of perched storm water due to relatively impervious or low infiltration rates. Therefore, it is strongly controlled by storm events and it should be noted that the groundwater is expected to fluctuate depending on climatic factors, surface drainage conditions, as well as storm influences and other factors.

WSP USA 13 Decmber 2021

3.0 Geotechnical Evaluations and Engineering Analysis

As discussed in Section 2.6, the subsurface below asphalt or topsoil consists of between 4.8 feet and in excess of 32 feet of glacial soils that mostly consist of very dense sand and gravel with alternating layers of very stiff-hard Clay and Silt (Stratum 2 and 3), and is underlain by bedrock Granite (Stratum 4).

The following subsections provide geotechnical design recommendations for the approximate 25,000 square foot maintenance building foundations, approximately 1,800 linear feet of retaining walls with heights that range from less than five to fifteen feet, a proposed utility trench from Rt 233 and the new building structure, new parking pavement, and soil properties that can be used for drainage basin design.

For Site geotechnical designs, the following design parameters were assigned.

Table 3: Geotechnical Design Parameters

Soil/Parameters Stratum 1 Fill

Stratum 2 Sand & Gravel

Stratum 3 Clay & Silt

Stratum Granite

Approximate depth below grade, ft. 0-4 4-14 14-22 >20

Angle of internal friction (f0) 30 36 - 40

Cohesion (ksf) - - 3.0 6.0 Unit weight (pcf) 110 125 125 160 Coefficient of passive resistance Kp

3.00 3.83 1.50 4.59

Coefficient of active pressure, Ka

0.33 0.26 0.40 0.21

Coefficient of at-rest earth pressure K0

0.50 0.41 0.50 0.35

Lateral bearing Pressure, ksf/ft. - 0.30 0.13 1.2

Coefficient of interface friction-ultimate 0.35 0.35 0.25 0.70

3.1 Foundations

Data obtained from this investigation indicate that the proposed new maintenance building may be supported on a shallow foundation system resting on Stratum 2, 3, or 4. The uppermost soil stratum, undocumented fill (Stratum 1) is in thickness generally less than 4 feet, is discontinuous and consists of very dense gray and brown sand and gravel; is not a bearing stratum. The underlying natural soil, Sand (Stratum 2), and Clay Silt (Stratum 3) are glacial soils, intermixed and transit one from another both in vertical and horizontal direction. Both Sand and Clay/Silt have relatively high bearing characteristics and below sand, clay and silt is bedrock granite which has excellent bearing characteristics but is very hard to remove and may require blasting.

WSP USA 14 Decmber 2021

Based on the Site soils, a shallow foundation system consisting of spread footings, or continuous wall foundations resting on Stratum 2 and Stratum 3 soils and bedrock granite (Stratum 4), minimum 4 feet below the existing grade can be designed using an allowable bearing capacity of 3.0 tsf. The allowable bearing capacity can be increased to 4.0 tsf in seismic design. If the foundations rest on bedrock granite, design to an allowable bearing capacity of 6.0 tsf. The allowable bearing capacity on granite can be increased to 8.0 tsf in seismic design. Settlements under these magnitudes of stress would be negligible.

The below Table 4 displays the top of bedrock elevations that can be used to evaluate footing depths in shallow foundation design.

Table 4: Top of bedrock elevations within the maintenance building footprint

Boring ID Depth to Bedrock (ft bgs) Top of Bedrock Elevation (ft amsl)

B1-21 4.8 +427.2

B2-21 8.3 +424.7

B3-21 8.8 +425.2

B-6 8.5 +424.5

3.2 Floor Slab

A slab-on-grade floor support is evaluated and recommended for all new structures. As noted in Section 3.8 and discussed below, the subgrade has poor infiltration characteristics. To avoid the slab subjected to freezing and thawing condition cycles and thereby reducing damage potential, under-slab drainage would be required. The following subgrade preparations will be needed in an effort to control settlements and early slab distress:

1. Excavate to 12 inches below the bottom elevation of the floor slab, crown and provide a minimum two (2) percent pitch to the sides which needs to be connected to a storm drain, or drain outside;

2. Do not expose subgrade into atmospheric conditions for more than a day, and do not allow subgrade to get wet;

3. Compact the entire floor slab area using a smooth roller with a maximum contact pressure of 80 pounds per square inch (psi), to obtain a minimum of 95 percent of the on-site soils dry density as observed in ASTM D 1557;

4. Place a separation fabric, Typar 3201, or equivalent;

5. Place 12 inches of ¾ inch size washed crushed stone;

6. Place vapor barrier; and,

7. Construct slab-on-grade as designed by others.

The floor slab prepared as recommended above can be designed using a modulus of subgrade reaction of 130 pci (using 1-foot by 1-foot plate).

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3.3 Retaining Walls

The proposed improvements at MacFarland Hill will include retaining walls to accommodate new Site grading. Geogrid supported, mechanically stabilized earth (MSE) style walls with heights between 5 and 15 feet, and gabion basket walls (for wall heights less than 5 feet), are proposed and evaluated in this report. Design was conducted in accordance with AASHTO LRFD, (AASHTO 2010) and MaineDOT Bridge Design Guide, 2003. Design analysis included evaluating factor of safety against sliding, overturning, global stability, and settlement.

3.2.1 Geogrid Supported Retaining Wall

Geogrid supported MSE walls are recommended to accommodate proposed fill areas located on the western slope of the project Site. Wall heights here will range between 5 and 15 feet and will support proposed parking areas. A typical geogrid supported wall section with facing elements consisting of welded galvanized steel bars filled with 2 to 4 inch diameter drainage stone is provided in Figure 3.

The proposed geogrid supported wall should be supported on a gravel or crushed stone leveling pad bearing on compacted Stratum 2 or 3 soil. An embedded depth of four feet is recommended to accommodate frost penetration depths in Mount Desert, Maine (MaineDOT 2003). Subgrade below the wall should be proof rolled to 95% of the soil’s dry density as observed in ASTM D 1557. If bedrock is encountered during retaining wall excavation, a levelling course of gravel fill (3/4 inch stone) may be placed to create a platform and the wall may rest on this fill (i.e. bedrock does not need to be excavated to achieve a four foot embedment depth).

The reinforced zone of the Geogrid Supported wall should be minimum 70% of the wall height, or a minimum eight feet (based on AASHTO LFRD), whichever is greater, and should be constructed using select granular backfill material (USCS symbols GP, GW, SP, or SW) with a maximum vertical geogrid spacing of 1.5 feet. Excavated material can be reused as backfill in the reinforced zone, provided that fines content (silt and clay) is no greater than 10%. Backfill material should be placed and compacted in 9-inch lifts and compacted to 95% of the soil’s dry density (ASTM D 1557).

Excavated fill should not be wet or saturated. If saturated material is encountered, the material should be dried or mixed with dry granular material to achieve the desired compaction density.

Other construction considerations are as follows:

1. Six-inch diameter drainage pipes should be installed every 25 linear feet of wall. The drainage pipes should penetrate the wall face, and be allowed to freely discharge onto the forest surface.

2. Light Posts and other vertical obstructions within the Geogrid Supported Wall reinforced zone, should be placed during the wall construction, with geogrid installed around the obstruction. Light posts should be installed in 30-inch (inner diameter) pipe, embedded the full depth of the wall and guiderails should be installed in 24-inch inner diameter pipe embedded 2.5 feet below ground.

3. An outside drain, consisting of ¾ inch diameter stone (or equivalate drainage material approved by the EOR) is recommended outside of the reinforced zone. The angle and size of this drain can be constructed as shown in Figure 3, or adjusted to accommodate BMP and / or parking area drainage needs.

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4. When possible, utilities should not be located within the reinforcement limits of the Geogrid Supported Wall, as the geogrid would have to be removed to access the utilities.

Geotechnical analysis, including sliding, overturning, global stability, and settlement were performed and calculations are presented in Appendix D. Boring logs indicate bearing soils at foundation depths within the proposed retaining wall areas, consist of dense clayey sandy soil (Stratums 2 and 3). The following geotechnical design parameters were used for retaining wall design analysis.

Backfill friction angle (Phi), degrees 30 Backfill cohesion, psi 0 Backfill Unit Weight, pcf 120 Active Earth Pressure Coef. (kA) 0.33 Passive Earth Pressure Coef. (kp) 3.00

Bearing Soil friction angle (Phi), degrees 32 Bearing Soil Cohesion, psi 0 Bearing Soil Unit Weight (ϒ), pcf 118 Bearing Soil Effective (saturated) unit weight 64 Active Earth Pressure Coef. of Bearing Soil (kA) 0.26 Passive Earth Pressure Coef. of Bearing Soil

(kp) 3.850 Friction Angle Between Bottom of Footing and bearing soil (δ) degrees 24

Based on the above design parameters and wall geometry, the geogrid supported wall has the following safety factors:

15 foot high wall 10 foot high wall 5 foot high wall Factor of Safety for Sliding

1.70 2.09 3.90

Factor of Safety for Overturning

2.62 2.21 3.56

Bearing shall not exceed 17.4 kips for a 15 foot wall and 15 kips for 10 and 5 foot high walls.

3.2.2 Gabion Walls

Gabion basket retaining walls, less than 5 feet in height, are proposed on the east side of the Site.

Gabion baskets should be embedded at least 1 foot below ground surface and consist of wire mesh gabion baskets, battered 6 degrees from vertical, leaning towards the top of the wall. The gabion wall shall consist of two courses of gabion baskets. The baskets should have a minimum base width of minimum 70% the wall height. Rock fill in the baskets will between 4 and 8 inches in diameter with a D50 of 6 inches. Geotextile fabric should be placed directly behind the back face of each gabion basket to prevent sediment from entering the stone.

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The baskets should bear on compacted foundation soil (Stratum 2 or 3) below a leveling course of gravel or crushed stone. Foundation soil should be proof rolled to minimum 95% of the soil’s dry density (as in ASTM D 1557).

3.4 Utility Trench

Borings TR-1 through TR-4 were conducted to evaluate the depth to bedrock and characteristics of the overburden soils that may be encountered while excavating for a proposed utility trench alignment, located from Rt 233 to the proposed new headquarters building.

Bedrock was encountered in one boring (TR-5), 10.8 feet below the surface (El. +420.2), and was greater than 17 feet below the surface (limits of boring), in the other borings (TR-1 through TR-4).

Overburden soils mostly consisted of dense to very dense, clayey sand with variable amounts of gravel and cobbles. Material encountered in these borings is considered excavatable up to depths of

10.8 feet below existing ground surface.

3.5 Parking Area Pavement

Considering that the new parking area as well as its connections will serve light vehicles (FHWA Class 1 through Class 3), the pavement can be designed using “permeable pavement design” principles, after partially removing clay and silt rich parts of the Stratum 2, and replacing the volume with crushed stone to serve as a “reservoir” and “choking” course, which would facilitate infiltration into subgrade and the soils below.

The following pavement box section was evaluated and recommended for porous (permeable Pavement).

Table 5: Permeable (Porous) Pavement Section

Aggregate base will need to be wrapped in separation geotextile to disallow mixing with subgrade and also the asphalt friction course.

A pavement design for the new pavement for a heavy duty parking lot and access road was developed and recommended as follows:

Material Thickness (inches) Superpave-HMA 4 Open graded friction course Aggregate Base 12 Total Thickness 16 Existing subgrade Uncompacted

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Table 6: Conventional Pavement Section

3.6 Site Infiltration Characterizations

The drainage characteristics of the Site soils was evaluated for the design of stormwater management drainage basins proposed throughout the Site. Based on the United States Department of Agriculture (USDA), National Resources Conservation Service (NRCS) maps (Appendix E), the Site is mapped as Marlow fine sandy loam (hydrologic soil group C). Phase 1 geotechnical activities included borehole infiltration testing conducted in five (5) boreholes (B-1, B2, B3, B4, and B5).

Borehole hydraulic conductivity calculations are provided in the Phase 1 report and indicate Stratum 2 and 3 soils (between 9.3 and 20.5 feet below existing ground) are part of hydrologic soil group D with hydraulic conductivity values less than 0.005 inch / hour. Based on these results, a Hydraulic Soil Group D is recommended.

Groundwater throughout the Site (when encountered) was observed between 4 and 18 feet below ground corresponding to +400.3 and El. +423.5 feet, with many boreholes not encountering groundwater (dry). Due to the variability in groundwater elevations, and presence of low permeability, restrictive soils (Silt and Clay), the groundwater is interpreted to be perched water and is related to surface/storm water activities and events. The seasonal high water table (SHWT) is determined to be below the boring limits in this investigation (greater than 20 feet).

3.7 Seismic Considerations

The proposed structure should be designed with seismic considerations according to the State Board of Building Regulations and Standards, which has been modified from International Building Code (IBC, 2012). From a probabilistic standpoint, the Maximum Considered Earthquake ground motion (per NEHRP 2000) is defined as the ground motion having a two (2) percent probability of exceedance in 50 years (an approximately 2,500-year return period). It is defined by the spectral accelerations at a 0.2-second period (Ss) and at a one (1)-second period (S1). Based on the national seismic hazard maps prepared by the United States Geological Survey (USGS, 2002), as well as the site location in Acadia National Park, Bar Harbor, Maine, the potential for damage due to seismic effect is low. For the seismic design, site class “Type D: Stiff Soil” with the following parameters obtained from USGS seismic design output (Appendix F) can be used.

Material Thickness (inches)

Superpave-HMA 4 Surface course, 12.5mm

Aggregate Base 8

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Table 7: USGS Seismic Report for Seismic Design Parameters

Factor/Class Value Site Class D Ss, Short Period Spectral Acceleration 0.182g S1, 1-Second Period Spectral Acceleration 0.068g Fa 1.6 Fv 2.4

The site does not have a potential for liquefaction in a seismic event.

3.8 Evaluations of Corrosion and Sulfate attack Potential

Preliminary chemical analysis on soil samples indicate sulfate (as SO4) concentrations in soil is less than 10 parts per million (ppm) and chloride (Cl) concentrations range from 10 ppm to 33 ppm. pH ranged between 4.3 to 7.3 and the minimum resistivity ranged from 9.2 k.ohm-cm to 10.9 k.ohm-

cm. As a result, sulfate, chloride, pH and resistivity values indicate negligible potential for sulfate attack to concrete, and negligible potential for corrosion to uncoated ferrous metals. Accordingly, Type IP(MS), I(MS)P,(MS) or Type II portland cement can be used in all foundation concrete and concrete in contact with soil and water (see ASTM C 595). Buried concrete should be dense and fully compacted, and the minimum cement content requirements of ACI should be observed. To mitigate against corrosion of uncoated ferrous metals, such as reinforcing bars, steel pipes or other steel members of the structure in contact with the soil, a minimal cover for reinforcement steel in accordance with ACI requirements should be observed. Steel and other metallic pipes in contact with soil should also be protected in accordance with the manufacturer’s recommendations.

3.9 Construction Considerations

For development at or near the existing Headquarters/Administrative Facilities, for safety of the adjacent structures and utilities, underpinning would be required if the excavation is below the existing foundation and if the distance is less than 10 feet. An economical underpinning can be designed and incorporated using vertical or raked micro piles penetrating into bedrock granite, or reinforced concrete panels with a maximum opening length of 8 feet to be constructed in alternating segments. Any underpinning support must be designed by a Maine Registered Professional Engineer and be approved by NPS.

The excavated soils would include clay, silt, fill as well as sand. Silt and clay in fill (Stratum 3) are present in layers and both are unsatisfactory soils for structural and common fill use. Therefore, they may be separated during excavation and be disposed of or used for landscaping. The sand fraction of the fill can be used for common fill purposes. The suitability of the excavated material for utilities backfill will need to be checked against the manufacturer’s or utility’s specifications. Silt and clay should not be left to atmospheric conditions for extended periods as they are moisture sensitive and are prone to deteriorations. The final 12 inches of the excavation should be completed within 24 hours of concreting or otherwise covering the site.

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Groundwater is mot expected within the excavation limits. However, perched water related to rainfall and storm events can possibly be encountered due to relatively impervious subsoil and shallow bedrock.

Bedrock granite cannot be removed by conventional excavation tools and requires blasting or the use of similar volume expansion agents. Therefore, costly and time-consuming bedrock excavation should be avoided.

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4.0 Conclusions and Recommendations

1. This report presents a factual account of the subsurface conditions based on 23 boreholes, laboratory test results, and our geotechnical analysis and geotechnical evaluations, for new foundations, retaining walls, pavement, a utility trench, and soil infiltration, for the new facilities at the McFarland Hill Headquarters in Acadia National Park, Bar Harbor, Maine.

2. The proposed improvements will include an approximate 25,000 square foot new maintenance building, parking lots, and approximately 1,800 linear feet of retaining walls with heights that range from five to fifteen feet.

3. Acadia National Park is located mainly on Mount Desert Island, the largest of several thousand islands along the New England coast with an elevation of approximately 1,500 feet (466 meters). Geologic units observed within the project area consist of bedrock granite overlain by glacial deposits. Local fill, also observed and as discussed in Section 2.6, are resultant of relatively recent site development activities.

4. Data collected during this investigation showed there are four (4) different strata with different depths/elevations below the existing ground surface which were described as 1) Fill, A discontinuous layer consisting of sand, silt, gravels and locally boulders to an average depth of 4 feet below the existing grade (Stratum 1), underlain by 2) Sand, Silty/Clayey Sand, Gravels and Cobbles (Stratum 2), underlain by, or horizontally and vertically transmitting into 3) Silty Clay and Clayey Silt, (Stratum 3), over bedrock Granite, massive, strong to very strong hard and sound (Stratum 4). Characteristics of these geotechnical./geological units were discussed in Section 2.6.

5. Groundwater throughout the Site (when encountered) was observed between 4 and 18 feet below ground corresponding to +400.3 and El. +423.5 feet, with many boreholes not encountering groundwater (dry). Due to the variability in groundwater elevations, and presence of low permeability, restrictive soils (Silt and Clay), the groundwater is interpreted to be perched groundwater and the seasonal high water table (SHWT) is determined to be below the boring limits in this investigation (greater than 20 feet).

6. A shallow foundation system consisting of spread footings, or continuous wall foundations resting on Stratum 2 and Stratum 3 soils and bedrock granite (Stratum 4), minimum 4 feet below the existing grade is recommended for the new structures. Depending on the foundation depth and subgrade, the report recommended allowable bearing capacities ranging between 3.0 and 6.0 tsf. Settlements under these magnitudes of stress would be negligible. In Section 3.2, recommended foundation depths/elevations were provided for feasible foundation construction and for selecting future building locations/heights.

7. This study recommended a slab-on-grade floor…