B08_Attach_06_Geotechnical_Report.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report

Rehabilitate Schoodic Water & Wastewater Systems

Acadia National Park, Winter Harbor, Maine

May 24, 2022

Terracon Project No. J1215067

VHB Project No. 34684.25

National Park Service (NPS) Contract No. 140P2021D0003

Prepared for:

Vanasse Hangen Brustlin, Inc.

South Portland, Maine

Prepared by:

Terracon Consultants, Inc.

Manchester, New Hampshire

Terracon Consultants, Inc. 77 Sundial Ave., Suite 401W Manchester, NH 03103

P (603) 647 9700 F (603) 647 4432 terracon.com

REPORT C OVER LETTER

Vanasse Hangen Brustlin, Inc.

500 Southborough Drive

South Portland, ME 04106

Attn: Mr. Timothy S. Bryant, PE

P: (207) 889 3103

E: tbryant@vhb.com

Re: Geotechnical Engineering Report

Rehabilitate Schoodic Water & Wastewater Systems

Mountain Road & Acadia Drive

Acadia National Park, Winter Harbor, Maine

Terracon Project No. J1215067

Dear Mr. Bryant:

We have completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with the NPS IDIQ Task Order Authorization No.

140P2021F0167 dated September 15, 2021. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

Michael A. Ciance, P.E. Joseph L. Robichaud, Jr., P.E. (NY)

Principal/Office Manager Principal

Cc: Mr. Edward Whatley, PE – Wright Pierce

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

SEISMIC CONSIDERATIONS

LIQUEFACTION

FLOOR SLABS

LATERAL EARTH PRESSURES

FROST CONSIDERATIONS

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

PHOTOGRAPHY LOG

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

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

http://client.terracon.com/

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INTRODUCTION

Geotechnical Engineering Report

Rehabilitate Schoodic Water & Wastewater Systems

Mountain Road & Acadia Drive

Acadia National Park, Winter Harbor, Maine Terracon Project No. J1215067

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed system improvements for the Schoodic Water and

Wastewater systems located at Mountain Road & Acadia Drive in Acadia National Park, Winter

Harbor, Maine. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Foundation design and construction

■ Groundwater conditions ■ Floor slab design and construction

■ Site preparation and earthwork ■ Seismic site classification

■ Demolition considerations ■ Frost considerations

■ Excavation considerations ■ Dewatering Considerations

■ Lateral earth pressures

The geotechnical field Scope of Services for this project included the advancement of one test boring (B-1) within the vicinity of the proposed pump house on Mountain Road, and three test borings (B-2 through B-4) near Eliot Hall on Acadia Drive. Test borings were advanced to refusal at depths ranging from approximately 1.7 to 9.0 feet below existing site grades.

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

Plan sections, respectively. The boring logs and laboratory results are shown 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 and our review of publicly available topographic maps.

Rehabilitate Schoodic Water & Wastewater Systems ■ Acadia National Park, Winter Harbor, Maine

May 24, 2022 ■ Terracon Project No. J1215067

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Item Description

Parcel Information

The project is located at the Schoodic Educational and Research Center

(SERC) within the Acadia National Park (site) which generally includes

Mountain Road & Acadia Drive in Acadia National Park, Winter Harbor, Maine. The site is considerably remote and is located approximately 60 miles from Bangor, Maine. For reference purposes, the existing Eliot Hall is located at the approximate coordinates of 44.3368°N, 68.0620°W. See

Site Location.

Existing Improvements

The site is predominantly wooded with the exception of Big Moose Island, located within the southwest portion of the site, where numerous buildings and associated paved roadways, parking areas, and sidewalks exist as part of the Schoodic Institute.

Current Ground Cover Predominately wooded, with areas of open grass lawn and asphalt roadways/pavement.

Existing Topography

(from site survey plans and online sources)

Site topography varies across the park. Within the two primary project areas, site topography is as follows:

Mountain Road well/pump house: Ground surface elevations generally slope gently downward from a high point at the existing transformer

(immediately north of the existing well house) from approximately elevation (El.) 149 feet to El. 147 feet at the access drive to the south of the well house.

Eliot Hall: Ground surface elevations in the vicinity of Eliot Hall are relatively level near El 92.0 feet.

We also collected photographs at the time of our field exploration program. Representative photos are provided in our Photography Log.

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PROJECT DESCRIPTION

Our understanding of the project, based on information included in the project documents and discussions during project planning, is as follows:

Item Description

Information Provided

Project information provided by the design team (VHB and/or Wright-

Pierce, Inc.) included the following:

■ “Acadia National Park, Schoodic Education and Research Center

National Park Service, Project Program” dated December 2021.

■ “Acadia Well House Boring” electronic file illustrating proposed boring location at well house on Mountain Road.

■ “Eliot Hall Probes” electronic file illustrating proposed boring locations at Eliot Hall site.

Project Description

The SERC is an existing facility within Acadia National Park. The scope of this project is to rehabilitate the SERC water supply and distribution system, sewer pumping stations, gravity and force main sewer distribution systems and associated appurtenances to address ongoing maintenance and service issues. As part of the rehabilitation project, and specific to the geotechnical investigation, the existing well house on Mountain Road will be demolished to construct a new well house building, electrical and instrumentation equipment, and a submersible pump and associated appurtenances. A portion of the raw water transmission main will be replaced with insulated pipe to improve winter operation conditions. In addition, a well house will also be constructed adjacent to Eliot Hall to relocate the pumps and instrumentation from the basement of Eliot Hall to the new well house structure.

Maximum Loads Structural loads associated with well houses and other ancillary structures are not known but anticipated to be less than 2,000 pounds per square foot (PSF).

Finished Floor Elevations Finished floor elevations for the proposed well houses on Mountain Road and near Eliot Hall are not known but anticipated to be near existing grade.

Grading/Slopes

We anticipate minimal cuts and fills will be required to construct new well houses, ancillary structures, and replace water and sewer lines throughout the campus.

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GEOTECHNICAL CHARACTERIZATION

Subsurface Conditions

Mountain Road Well House Site

Test borings generally encountered a surficial topsoil/subsoil layer underlain by a relatively thin glacial till deposit over bedrock. Test boring B-1 encountered auger and/or sampler refusal at a depth of approximately 5 feet below grade; however, a second offset location (approximately 5 feet south of B-1) encountered refusal at a depth of approximately 9 feet below existing grade.

The glacial till deposit is generally described as light brown, dense to very dense, silty sand with gravel. Based on our review of available bedrock maps, bedrock is expected to consist of hornblende-biotite granite.

Eliot Hall Site

Subsurface explorations within this portion of the project site generally encountered a surficial topsoil layer (approximately 2.5 to 5.0 inches thick) underlain by glacial till over relatively shallow bedrock. The glacial till deposit within this portion of the site is generally consistent with the deposition at Mountain Road, and is described as brown, sandy silt with gravel to silty sand with gravel. The relative density of the till generally increases with depth from loose to medium dense near the ground surface to very dense near the top of bedrock. Test borings B-2 through B-4 encountered sampler refusal at depths ranging from approximately 2.1 feet (B-4) to 5.6 feet (B-

2). Though not encountered in the test borings, existing fill should be expected on site based on previous development, particularly near existing structures and utilities. Consistent with the

Mountain Road site, bedrock is expected to consist of hornblende-biotite granite.

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.

Model Layer Layer Name General Description

1 Topsoil & Subsoil Up to 5 inches of topsoil over silty sand subsoil

2 Glacial Till Silty sand with gravel, brown to reddish brown, medium dense to very dense

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Groundwater Conditions

Groundwater was encountered at a depth of approximately 3.3 feet below existing grade (boring

B-1) during drilling at the proposed well house site at the top of Mountain Road. Groundwater was not observed within the test borings (B-2 through B-4) during drilling at the Eliot Hall site;

however, groundwater will likely be perched within the glacial till or near the top of bedrock during seasonally wet periods.

Groundwater level fluctuations will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

GEOTECHNICAL OVERVIEW

The project site appears suitable for the proposed development based upon the geotechnical conditions encountered in the borings provided the recommendations in this report are implemented during design and construction.

The project will require the demolition of the existing well house on Mountain Road, replacement of water lines (predominantly within existing water line trenches) throughout the entire water system upgrade, and partial demolition/renovation of the existing Eliot Hall to move the well/pump house outside the existing building. We recommend existing foundations, slabs, pavements, and utilities be removed from within the proposed well house/pump house and ancillary foundation footprints, and at least 5 feet beyond the outer edge of foundations. Additional demolition considerations are provided in the Earthwork section.

As mentioned in the Geotechnical Characterization section, existing fill may be encountered near existing structures. Supporting new foundations/floor slabs on existing unimproved fill may cause structures to settle beyond tolerable limits. Therefore, we recommend complete excavation and removal of undocumented fill (if encountered) and replacement with compacted Structural Fill within the foundation bearing zone and well house/structure footprint to mitigate the risk of post-construction settlement. Excavation is discussed further in the Earthwork section.

Bedrock will likely be encountered during excavation efforts. It is anticipated that blasting will not be permitted within the National Park; therefore, where rock excavation is required, it will likely need be performed using mechanical means such as the use of a pneumatic hammer and/or drilling with expansive chemical agents. Considerations for rock excavation are included in the

Earthwork section.

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Due to the elevated silt contents, subsoil and glacial till deposits will likely become unstable with typical earthwork and construction traffic, especially after precipitation events. Effective site drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If earthwork is performed during seasonally wet periods, an increased risk for possible undercutting and replacement of unstable subgrades will persist.

Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

The Shallow Foundations section addresses support of the well house buildings and ancillary structures bearing on a minimum 12-inch thick layer of compacted Structural Fill or Crushed Stone placed over proof-rolled glacial till or bedrock. In areas where foundation excavations encounter bedrock, the rock should be over-excavated to provide a minimum 12-inch thick layer of compacted Structural Fill or Crushed Stone between design footing elevation and the bedrock surface. The Floor Slabs section addresses slab-on-grade support on a minimum 12-inch thick layer of compacted Floor Slab Base Course over proof-rolled native soil. If slab excavations encounter bedrock, rock should be over-excavated to provide a minimum 12-inch thick layer of

Crushed Stone below the slab to provide a soil cushion between the slab and the bedrock surface.

New utility lines will typically be installed within existing utility line trenches (following excavation/removal of the existing utility). However, there will be area along the proposed alignments where new trenching is necessary. New water and sewer lines should be located at least 5 feet below finished grade to provide adequate frost protection. Alternatively, the use of insulation may be considered to provide an R-Value equal to or greater than the equivalent 5 feet of earthen cover. Recommendations related to utility lines are presented below.

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

EARTHWORK

Earthwork is anticipated to include demolition, clearing and grubbing, excavations, and fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Demolition

As part of the rehabilitation project, the existing water and sewer lines will be replaced and the existing well house at Mountain Road and in Eliot Hall will be demolished to construct new well houses. We recommend existing foundations, slabs, and utilities be removed from within proposed building footprints and at least 5 feet beyond the outer edge of new foundations.

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For areas outside the proposed building footprint and foundation bearing zones, existing foundations, floor slabs, and utilities should be removed where they conflict with proposed utilities and pavements. In such cases, existing foundations, floor slabs, and utilities should be removed to a depth of at least 2 feet below the affected utility or design pavement subgrade elevation.

Site and Subgrade Preparation

Demolition debris, pavements, vegetation, and root mat should be removed before placing new fill. Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

As noted in the Geotechnical Characterization section, existing fill (although not encountered within the test borings) may be encountered near existing structures. Supporting new foundations and floor/exterior slabs on existing unimproved fill material may cause structures to settle beyond tolerable limits. Therefore, we recommend complete excavation and removal of existing undocumented fill (if encountered) and replacement with compacted lifts of Structural Fill within the proposed building footprints and foundation bearing zones to mitigate the risk of post-construction settlement.

Following excavation and before placing new fill, native soil subgrades should be proof-rolled with at least six passes in perpendicular directions using a minimum 10-ton vibratory roller in open areas; or a minimum 1-ton self-propelled vibratory roller or large vibratory plate compactor in trenches. The proof-rolling should be performed under the direction of the Geotechnical Engineer.

Areas excessively deflecting under the proof-roll should be delineated and subsequently addressed by the Geotechnical Engineer. Soft or unstable areas should be over-excavated to more competent material and replaced with compacted Structural Fill or General Fill depending on the anticipated future use. Excessively wet or dry material should either be removed, or moisture conditioned and recompacted.

Weathered rock and potentially competent bedrock will likely be encountered during excavations for the well houses and along new utility alignments, particularly within the vicinity of Eliot Hall.

Where bedrock subgrades are encountered, the bedrock should be excavated to provide a minimum 12-inch-thick layer of compacted Structural Fill or Crushed Stone below foundations, a minimum 12-inch-thick layer of Crushed Stone below floor slabs, and a minimum 6-inch thick layer of suitable pipe bedding material below proposed utility pipes.

Bedrock subgrades should be observed for open joints, loose rock, and uneven surfaces. Loose rock pieces should be removed, and open bedrock joints should be choked with Crushed Stone or filled with lean concrete before placing fill. Bedrock subgrades steeper than 4H:1V should be benched. If required, the bedrock surface can be leveled to grade by placing lean concrete or by removing isolated higher areas of the bedrock. Bedrock subgrades will not require proof-rolling;

however, if loose rock is exposed it should be replaced with Crushed Stone or lean concrete.

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Fill Material Types

The following section presents material property requirements and suitable placement locations for various types of fill. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Reuse of On-site Soil: Excavated on-site soil (predominantly subsoil and glacial till) may be selectively reused as raise-in-grade fill (General Fill) at depths greater than 2 feet below planned pavements or within landscaping areas (if planned). Excavated on-site soil is not suitable for reuse as Structural Fill due to its elevated silt content and should not be placed beneath settlement sensitive structures and within foundation bearing zones.

Excavated on-site soil is expected to have an elevated fines content and will be sensitive to moisture conditions (particularly during seasonally wet periods) and may not be suitable for reuse when above optimum moisture content. On-site soil may be used as General Fill provided it has the following properties:

■ Free of deleterious materials

■ A maximum particle size equal to the lesser of 6 inches or 2/3 of the lift thickness

■ A suitable moisture content allowing for effective compaction

■ Compactive efforts yield a firm and stable surface

Imported Fill Materials: Imported fill materials should meet the material property requirements in the following table.

Fill Type Maine Department of

Transportation (MaineDOT) Item Acceptable Location for Placement

Imported General

Fill

703.18 – Common Borrow

General raise-in-grade fill within pavement and landscaping areas.

General Fill should not be placed beneath settlement sensitive structures and within foundation bearing zones.

Structural Fill 703.19 – Granular Borrow

Beneath foundations, within foundation bearing zones, and as backfill within 5 feet of exterior foundation walls. Structural Fill should also be used as raise-in-grade fill to achieve subgrade elevations beneath floor slabs and settlement sensitive structures.

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Fill Type Maine Department of

Transportation (MaineDOT) Item Acceptable Location for Placement

Crushed Stone

703.13 – Crushed Stone ¾-Inch

Backfill of underdrains, over wet subgrades or over bedrock subgrades, as needed. Crushed Stone may be substituted for Structural Fill when approved by the Geotechnical

Engineer.

Non-Frost

Susceptible Fill

703.22 – Underdrain Backfill Material, Type B or

703.13 – Crushed Stone ¾-Inch

Below exterior slabs, sidewalks, pavements, or other ancillary structures where frost heave may be a concern.

Floor Slab Base

Course

703.06 – Aggregate for Base, Type A

Below floor slabs as aggregate base course.

1. Crushed Stone should be separated from soil subgrades, excavation sidewalls, and backfill using a non-woven geotextile (such as Mirafi 140N or similar).

2. Non-Frost Susceptible (NFS) Fill should contain less than 5 percent material passing No. 200 sieve size.

Fill Compaction Requirements

Fill materials should meet the following compaction requirements.

Item Description

Maximum Lift Thickness

Vibratory Rollers: 12 inches or less in loose thickness

Plate Compactors: 6 inches or less in loose thickness when hand-guided equipment (i.e., jumping jack or plate compactor) is used

Minimum Compaction

Requirements 1, 2

General Fill: At least 92% of the material’s maximum dry density

Structural Fill: At least 95% of the material’s maximum dry density

Crushed Stone: Densified and compacted using at least six (6) passes of a vibratory roller or large vibratory plate compactor

Water Content Range ±3% of optimum water content

1. Maximum density and optimum water content as determined by the Modified Proctor test (ASTM D1557, Method C).

2. We recommend testing fill for moisture content and compaction during placement. If the results of in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested, as required, until the specified moisture and compaction requirements are achieved.

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Utility Trench Backfill

Trench excavations should be made with sufficient working space to permit construction including backfill placement and compaction. Trenches should be backfilled with material that approximately matches the permeability characteristics of the surrounding soil, to the extent practical. Fill placed as backfill for utilities located below settlement sensitive structures should consist of compacted Structural Fill or suitable bedding material as specified by the utility designer.

Grading and Drainage

All grades must provide effective drainage away from existing and proposed buildings/structures during and after construction and should be maintained throughout the life of the structures. Water retained next to buildings can result in soil movements greater than those discussed in this report.

Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks.

Exposed ground should be sloped and maintained at a minimum 5% away from buildings for at least 10 feet beyond the perimeter of the building (to the extent practical). Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. However, weathered, and competent bedrock, will likely be encountered during excavations for foundations and utilities. It is anticipated that blasting will not be allowed within the National Park; therefore, rock excavations will need to be performed using mechanical methods such as the use of a pneumatic hammer and/or the use of drilling with expansive chemical agents.

If blasting can be utilized to remove bedrock, a site-specific blasting plan should be prepared by the rock removal contractor prior to beginning construction. The plan should address contractor qualification; warning measures; safe transportation, handling, and storage of blasting materials;

use of blasting mats; coordination with local fire and EMS districts; pre-blasting condition surveys of nearby buildings; minimizing impacts to drinking water wells; notifications to nearby businesses and residential owners of 24-hour contact information for reporting well impacts occurring after blasting operations (if applicable), and specified vibration and air-blast overpressure limits along with whatever other considerations are required by local authorities. The blasting plan should also

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Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of footings and floor slabs. Construction traffic over the completed subgrades should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

Based on observed groundwater conditions at the time of our explorations, we do not anticipate significant construction impacts due to groundwater; however, water may be perched on the relatively low permeability soil or near the top of bedrock either seasonally or following precipitation. If dewatering becomes necessary, a temporary dewatering system could be necessary to achieve the required excavation depths. Dewatering is a means and methods consideration for the contractor.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local, and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer.

Monitoring should include documentation of adequate removal of demolition debris, vegetation, topsoil, and unsuitable fill. Foundation excavations and subgrade preparation should also be observed by the Geotechnical Engineer. If unanticipated conditions are encountered, the

Geotechnical Engineer should be notified to evaluate the need for supplemental mitigation recommendations.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

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SHALLOW FOUNDATIONS

If the site has been prepared in accordance with the requirements noted in the Earthwork section, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description

Maximum Net Allowable Bearing Pressure 1, 2

4,000 psf

Required Bearing Stratum

Minimum 12 inches of compacted Structural Fill (or

Crushed Stone) over proof-rolled glacial till or bedrock.

Where bedrock is encountered above design footing grade, it should be over-excavated to provide a minimum 12-inch thick layer of compacted Structural Fill or Crushed Stone.

Minimum Foundation Dimensions Columns: 30 inches

Continuous: 18 inches

Ultimate Passive Resistance

(Equivalent Fluid Pressures) 390 pcf (Structural Fill)

Ultimate Coefficient of Sliding Friction

0.5 (Cast-in-Place Concrete on Structural Fill or

Crushed Stone)

Minimum Embedment below Finished Grade

Exterior footings in unheated areas: 48 inches

Interior footings in heated areas: 18 inches

Estimated Total Settlement from Structural

Loads

Less than about 1 inch

Estimated Differential Settlement 2, 7

About 1/2 of total settlement

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Item Description

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. Values assume that exterior grades are no steeper than 2H:1V next to the structure.

2. Values provided are for maximum loads noted in the Project Description section.

3. Existing undocumented fill, unsuitable, and/or soft soils should be over-excavated and replaced per the recommendations presented in the Earthwork section.

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed, and compacted Structural Fill is placed against the vertical footing face.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. 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.

Interior footings in heated areas may be seated at the 18-inch depth if allowed by local building codes.

7. Differential settlements are as measured over a span of 40 feet.

Design Parameters - Uplift Loads

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils. As illustrated on the subsequent figure, the effective weight of the soil prism defined by diagonal planes extending up from the top of the perimeter of the foundation to the ground surface at an angle, , of 20 degrees from the vertical can be included in uplift resistance.

The maximum allowable uplift capacity should be taken as a sum of the effective weight of soil plus the dead weight of the foundation, divided by an appropriate factor of safety. A maximum total unit weight of 120 pcf should be used for the backfill. This unit weight should be reduced to

57.6 pcf for portions of the backfill or natural soils below the groundwater elevation.

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Foundation Construction Considerations

As noted in the Earthwork section, the foundation excavations should be evaluated under the direction of the Geotechnical Engineer. The base of all foundation excavations should be free of water, loose soil and loose bedrock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the foundation excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable material is encountered at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils. The over-excavation should be backfilled up to the footing base elevation with compacted Structural Fill as recommended in the Earthwork section.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design

Category. Site Classification is required to determine the Seismic Design Category for a structure.

The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the Maine State Building Code (MSBC), which references the International Building Code (IBC).

Based on the soil properties encountered at the site and as described on the exploration logs and results, it is our professional opinion that the Seismic Site Classification is C. Subsurface explorations at this site were extended to a maximum depth of 9.0 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area.

LIQUEFACTION

Based upon the soil composition, relative density, and groundwater conditions encountered in the test borings, it is our professional opinion that the project site is not susceptible to liquefaction during a design seismic event.

FLOOR SLABS

Design parameters for floor slabs assume the requirements in the Earthwork section have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the base course beneath the floor slab.

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Floor Slab Design Parameters

Item Description

Floor Slab Support 1, 2, 3

Minimum 12 inches of compacted Floor Slab Base

Course over proof-rolled glacial till or

Minimum 12 inches of compacted Crushed Stone over bedrock, if encountered

Estimated Modulus of Subgrade Reaction

200 pounds per square inch per inch (psi/in) for point loads

Modulus Correction Factor, Kc 𝐾𝑐 = 𝑘 ( 𝑏 + 1

2𝑏

1. Floor slabs should be structurally independent of building foundations or walls to reduce the possibility of floor slab distress caused by differential movements between the slab and foundation.

2. Other design considerations such as cold temperatures and condensation development could warrant a different base course material.

3. Existing undocumented fill, unsuitable, and/or soft soils should be over-excavated and replaced per the recommendations presented in the Earthwork section.

4. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in the Earthwork section, and the floor slab support as noted in this table. It is provided for point loads. It is common to reduce the k-value to account for dimensional effects of large, loaded areas using the modulus correction factor provided, where Kc is the corrected or design modulus value and b is the mat width (short dimension) or tributary loaded area. The native soil at subgrade is expected to develop a subgrade modulus value of 150 psi/in when combined with the base course. Soft or unstable subgrade will be remediated by scarifying and re-compacting or by over-excavation and replacement.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or cracks should be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks beyond the

Responsive ■ Resourceful ■ Reliable 16 length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of control joints, appropriate reinforcing, or other means.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed and compacted Structural Fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should approve the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

LATERAL EARTH PRESSURES

Although not anticipated, if site retaining walls or unbalanced foundation walls are planned, then these structures will need to be designed to accommodate lateral earth pressures. The following section presents lateral earth pressure parameters and recommendations for permanent earth retaining structures; they do not apply to design of temporary support-of-excavation structures or mechanically stabilized earth (MSE) retaining walls.

Design Parameters

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to the values indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The “at-rest” condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

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Lateral Earth

Pressure

Condition

Lateral Earth

Pressure

Coefficient

Surcharge Pressure, p1 (psf) 3, 4, 5

Effective Fluid Pressures (psf) 2, 4, 5

Unsaturated 6 Submerged

Active (Ka) 0.31 (0.31)S (40)H (80)H

At-Rest (Ko) 0.47 (0.47)S (55)H (90)H

Passive (Kp) 3.25 --- (390)H (250)H

1. For active earth pressure, wall must rotate about base, with top lateral movements 0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance.

2. Backfill placed against structures should consist of compacted Structural Fill. A maximum unit weight of

120 pcf is assumed for the values in this table. For the earth pressure coefficients to be valid, the Structural

Fill must extend out and up from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively.

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

5. No safety factor is included in these values.

6. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage for Below-Grade Walls below. “Submerged” conditions are recommended when drainage behind walls is not incorporated into the design.

Subsurface Drainage for Below-Grade Walls

Foundation perimeter drains and/or subsurface drains are recommended if below-grade occupied space or site retaining walls are planned as part of the project. Foundation perimeter/subsurface drains may consist of perforated rigid plastic drain lines (HDPE or PVC). Foundation perimeter drains should be installed behind the base of walls and extend below adjacent grade to prevent hydrostatic loading on the walls. Drain inverts should be placed near foundation bearing level.

The drain line should be sloped to provide positive gravity drainage to daylight or to a sump pit and pump. The drain line should be surrounded by Crushed Stone. The Crushed Stone should be encapsulated in a filter fabric. Wall backfill, consisting of compacted Structural Fill, should

Responsive ■ Resourceful ■ Reliable 18 extend to within 2 feet of final grade, where it should be capped with pavement or compacted cohesive fill to reduce infiltration of surface water into the drain system.

As an alternative to Crushed Stone, a prefabricated drainage structure may be considered. A prefabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion and is fastened to the wall prior to placing backfill. The drainage structure should be tied into the foundation drain.

FROST CONSIDERATIONS

The soils on this site are frost susceptible, and small amounts of water can affect the performance of the slabs-on-grade, sidewalks, and pavements. Exterior slabs and pavements should be anticipated to heave during winter months. If frost action needs to be eliminated in critical areas, we recommend the use of Non-Frost Susceptible (NFS) Fill. Placement of NFS Fill in large areas may not be feasible; however, the following recommendations are provided to help reduce potential frost heave:

■ Provide surface drainage away from the building and slabs, and toward the site storm drainage system.

■ Install drains around the perimeter of the building, stoops, below exterior slabs, and pavements, and connect them to the site storm drainage system.

■ Grade subgrades so groundwater potentially perched in overlying more permeable subgrades, such as sand or aggregate base, slope toward a site drainage system.

■ Place NFS Fill as backfill beneath sidewalks, exterior slabs, and pavements critical to the project.

■ Place a 3 horizontal to 1 vertical (3H:1V) transition zone between NFS Fill and other soils.

As an alternative to extending NFS Fill to the full frost depth, consideration can be made to placing extruded polystyrene or cellular concrete under a buffer of at least 2 feet of NFS Fill.

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

Responsive ■ Resourceful ■ Reliable 19 absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

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 express 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

-1

D E

P T

H B

E L

O W

G R

A D

E

F ee

t) Rehabilitate Schoodic Water & Wastewater Systems Winter Harbor, ME Terracon Project No. J1215067

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.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1 B-2 B-3 B-4

GEOMODEL

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

Groundwater levels are temporal. The 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.

First Water Observation

LEGEND

Topsoil

Silty Sand

Silty Sand with Gravel

Sandy Silt with Gravel

Poorly-graded Gravel with Silt and Sand

Model Layer General DescriptionLayer Name

2.5 to 4 inches ot topsoil over sandy silt and silty sand1

Silty sand with gravel, grayish brown to reddish brown, medium dense to very dense2

Topsoil / Subsoil

Glacial Till

3.3

5.6

2.5

4.3

2.1

ATTACHMENTS

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

EXPLORATION AND TESTING PROCEDURES

Field Exploration

Boring Nos. Boring Depth (feet) Location

B-1 5.0 to 9.0 Proposed Well House (Mountain

Road)

B-2 through B-4 2.1 to 5.6 Eliot Hall Area

Boring Layout and Elevations: Unless otherwise noted, Terracon personnel provided the boring layout. Coordinates were obtained with a handheld GPS unit (estimated horizontal accuracy of about ±10 feet) and approximate elevations were obtained by interpolation from partial site plans provided by Wright-Pierce, Inc. 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 track-mounted rotary drill rig using continuous flight hollow stem augers. Samples were generally obtained nearly continuously through the depth of each boring. Borings were terminated upon encountered auger or sampler refusal conditions. In the split-barrel sampling procedure, 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 last 12 inches of a normal 18-inch penetration was recorded as the Standard Penetration Test (SPT) resistance value.