New Comfort Station File No. 751/17146.TAP Mackinac Island State Harbor Index No. 53250 Mackinac Island, Michigan PSC Project No. 2018060

GEOTECHNICAL DATA 003132 - 1

DOCUMENT 003132 - GEOTECHNICAL DATA

1.1 GEOTECHNICAL DATA

A. This Document with its referenced attachments is part of the Procurement and Contracting Requirements for Project. They provide Owner's information for Bidders' convenience and are intended to supplement rather than serve in lieu of Bidders' own investigations. They are made available for Bidders' convenience and information, but are not a warranty of existing conditions. This Document and its attachments are not part of the Contract Documents.

B. A geotechnical investigation report for Project, prepared by SME, dated December 28, 2018, is available for viewing as appended to this Document.

C. RelatedRequirements:

1. Document 003126 "Existing Hazardous Material Information" for hazardous materials reports that are made available to bidders.

END OF DOCUMENT 003132

GEOTECHNICAL EVALUATION REPORT

MACKINAC ISLAND COMFORT STATION

MACKINAC ISLAND STATE HARBOR, MICHIGAN

SME Project No. 080599.00

December 28, 2018

856 E. Eighth Street, Suite 1 Traverse City, MI 49686-2784

T (231) 941-5200 www.sme-usa.com

© 2018 SME

080599.00+122818+GER

December 28, 2018

Mr. Jason Goff WTA Architects 100 South Jefferson Avenue Suite 601 Saginaw, Michigan 48607

Via E-mail: jgoff@wtaarch.com (PDF file)

RE: Geotechnical Evaluation Mackinac Island Comfort Station

Mackinac Island State Harbor, Michigan SME Project No. 080599.00

Dear Mr. Goff:

We have completed our geotechnical evaluation for the proposed Mackinac Island Comfort Station in Mackinac Island State Harbor, Michigan. This report presents the results of our observations and analyses, and our geotechnical recommendations based on the information disclosed by the boring.

We appreciate the opportunity to be of service. If you have questions or require additional information, please contact me.

Sincerely, SME

Paul E. Anderson, PE Project Manager / Project Engineer

Prepared by: Reviewed by:

Paul E. Anderson, PE Jeffery M. Krusinga, PE, GE Project Engineer Senior Consultant

TABLE OF CONTENTS

1. INTRODUCTION

1.1 SITE CONDITIONS

1.2 PROJECT DESCRIPTION

2. EVALUATION PROCEDURES

2.1 FIELD EXPLORATION

2.2 LABORATORY TESTING

3. SUBSURFACE CONDITIONS

3.1 SOIL CONDITIONS

3.2 GROUNDWATER CONDITIONS

4. ANALYSIS AND RECOMMENDATIONS

4.1 SITE PREPARATION AND EARTHWORK

4.1.1 EXISTING FILL CONSIDERATIONS

4.1.2 ROCK ELEVATION CONSIDERATIONS

4.1.3 SITE SUBGRADE PREPARATION

4.1.4 ENGINEERED FILL REQUIREMENTS

4.2 FOUNDATIONS

4.3 BELOW-GRADE WALLS AND DRAINAGE

4.4 SEISMIC SITE CLASS

4.5 TEMPORARY EARTH RETENTION

4.6 CONSTRUCTION CONSIDERATIONS

APPENDIX A

BORING LOCATION DIAGRAM (FIGURE NO. 1)

BORING LOG TERMINOLOGY

BORING LOG (B1)

APPENDIX B

IMPORTANT INFORMATION ABOUT THIS GEOTECHNICAL ENGINEERING REPORT

GENERAL COMMENTS

LABORATORY TESTING PROCEDURES

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1. INTRODUCTION

This report presents the results of the geotechnical evaluation performed by SME for the proposed Mackinac Island Comfort Station in Mackinac Island State Harbor, Michigan. This evaluation was conducted in general accordance with the scope of services outlined in SME Proposal No. P03490.18, dated October 23, 2018. However, one of the planned borings was not performed since the west side of the site could not be accessed with our drilling equipment, and the depth of the one boring was reduced to 10 feet from the planned depth of 20 feet due to the presence of shallow rock. WTA Architects authorized SME’s services for this project.

To assist SME with our evaluation and preparation of this report, WTA provided SME with the following documents:

A drawing titled “Existing Site Survey” dated November 27, 2018, prepared by WTA

A drawing titled “Existing Floor Plan” dated November 27, 2018, prepared by WTA

A drawing titled “Proposed Floor Plan” dated November 27, 2018, prepared by WTA

A historic plan set titled “State of Michigan Department of Natural Resources Parks and Recreation Division Mackinaw Island State Harbor of Refuge Repairs/Renovations Mackinaw Island, Michigan 49757” (Sheets 1 through 51) with a latest revision date of July 2006, prepared by United Design Associates.

1.1 SITE CONDITIONS

The project site is located at the existing comfort station that is located on the south side of Main Street (M-185), at the Mackinac Island State Harbor on the south side of the island. The location of the site is depicted on the Location Map inset on the Boring Location Diagram (Figure No. 1) included in Appendix A of this report.

The existing comfort station building contains toilet and shower facilities. The existing wood-framed building covers a footprint of about 1,187 square-feet and has a finish floor elevation (FFE) of 588.2 feet, which approximately matches the elevation of the sidewalk north of the building along Main Street.

Ground surface elevations adjacent to the building descend from about 588 feet north of the building to about 582.5 feet at the concrete walkway south of the building. The water level of Lake Huron was 579.8 feet when surveyed for the Existing Site Survey plan dated November 27, 2018. The record Lake Huron water level was recorded as 582.3 feet in 1985.

1.2 PROJECT DESCRIPTION

The project consists of demolishing the existing comfort station building and designing and constructing a new (replacement) comfort station building. The new building will be located in the same general location of the existing building, but will be larger than the existing building. The new building will cover a footprint of 1,898 square-feet.

The new building will be a single-story, slab-on-grade building consisting of load-bearing masonry walls.

The FFE of the new building will be situated at about elevation 583 feet, which is about 5.2 feet lower than the FFE of the existing comfort station building. Based on existing site topography, we anticipate excavations to construct the footings along the north wall of the new building will extend about 8 feet below the adjacent sidewalk and road. The required cut depths will decrease from north to south across the new building footprint since existing surface elevations descend from north to south.

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2. EVALUATION PROCEDURES

2.1 FIELD EXPLORATION

SME completed one boring (B1) at the site on December 13, 2018. The boring was located east of the proposed comfort station building and extended to 10 feet beneath the existing ground surface. The boring was terminated at a depth of 10 feet due to hard drilling conditions in limestone rock. The approximate as-drilled location of the boring is depicted on Figure No. 1.

SME and WTA jointly determined the planned number and general locations of the borings. The boring planned to be located west of the proposed building could not be performed since that area was not accessible with our drilling equipment. SME located boring B1 in the field by measuring from existing site features, and SME estimated the existing ground surface elevation at the boring location to the nearest 1-foot using the topographic information included on the referenced Existing Site Survey drawing.

The boring was drilled using a rotary-type drill rig mounted on an ATV. The boring was advanced to the sampling depths using continuous-flight, hollow-stem augers. The boring included soil sampling based upon the Split-Barrel Sampling procedure. The driller sealed recovered split-barrel samples in glass jars.

The driller recorded groundwater observations in the borehole during and after completion of the boring.

Upon completion of drilling and recording groundwater observations, the borehole was backfilled with auger cuttings.

Soil samples recovered from the field exploration were delivered to our laboratory for further observation and testing.

2.2 LABORATORY TESTING

The laboratory testing program consisted of performing visual soil classification on recovered samples in general accordance with ASTM D2488. Since cohesive soils were not encountered, additional laboratory testing was not performed. The Laboratory Testing Procedures in Appendix B, provides laboratory test descriptions. Based on the laboratory testing, we developed a soil description and assigned a Unified Soil Classification System (USCS) group symbol to each of the various soil strata encountered.

Upon completion of the laboratory testing, SME prepared a boring log that includes information on materials encountered, penetration resistances, pertinent field observations made during the drilling operations, the results of the laboratory tests, and the existing ground surface elevation as estimated by SME. The boring log is included in Appendix A. Explanations of symbols and terms used on the boring log are provided on the Boring Log Terminology sheet included in Appendix A.

Soil samples are normally retained in our laboratory for 60 days and then disposed, unless instructed otherwise.

3. SUBSURFACE CONDITIONS

3.1 SOIL CONDITIONS

The conditions encountered at the boring generally consisted of existing brick pavers at the ground surface, overlying about 6 inches of sand fill. The sand fill was underlain by fill material consisting primarily of limestone fragments and pieces. The limestone fill was underlain by weathered limestone that extended to the explored depth (10 feet) of the boring.

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The fill material consisting of primarily limestone fragments and pieces extended to about 6 feet beneath the ground surface (or to approximate elevation 580 feet). The limestone fill was in a medium dense condition based on Standard Penetration Test (SPT) resistances (N-Values) of 16 to 19 blows per foot of penetration (bpf).

The weathered limestone beneath the fill was encountered beginning at approximate elevation 580 feet.

The weathered limestone was penetrated about 4 feet to the explored depth of the boring. SPT resistances in the limestone increased with depth and varied from 15 blows per 6 inches of penetration to 100 blows per 4 inches of penetration.

The soil profile described above and included on the appended boring log is a generalized description of the conditions encountered. The stratification depths described above and shown on the boring log indicate a zone of transition from one soil type to another. They do not show exact depths of change from one soil type to another. Soil conditions and the depths to rock may vary away from the boring location.

Please refer to the boring log for the soil descriptions and results of field and laboratory tests at the specific boring location.

3.2 GROUNDWATER CONDITIONS

Groundwater was not observed in the borehole during or upon completion of drilling. However, we anticipate the groundwater level at the site will be at or slightly above the surface water level of Lake Huron. Therefore, at the one boring performed for this evaluation, we anticipate the groundwater to be present at about the top of rock. It is our opinion that groundwater was not observed at the boring since it can take some time for groundwater to infiltrate into a borehole in weathered limestone rock.

Groundwater levels, perched groundwater conditions, and the rate of infiltration into excavations should be expected to fluctuate throughout the year, based on variations in precipitation, evaporation, and the surface water level of Lake Huron, run-off, and other factors. The groundwater observations indicated on the boring log represent conditions at the time the readings were taken. The groundwater levels at the time of construction and at future times may vary from those conditions noted on the boring log.

4. ANALYSIS AND RECOMMENDATIONS

4.1 SITE PREPARATION AND EARTHWORK

4.1.1 EXISTING FILL CONSIDERATIONS

For fill material to be considered as engineered fill, the fill would need to be:

Composed of an approved soil or aggregate material that is free of frozen soil, excessive organics, excessive oversize material that would hinder compaction, and other deleterious materials.

Spread in relatively level layers or lifts, with the lift thickness limited to the thickness that can be suitably compacted with the compaction equipment being used.

Compacted at a suitable moisture content and to a minimum specified dry density under the observation and testing of a geotechnical engineer.

Based on the boring, it is our opinion that some deliberate level of compaction effort was applied when the existing fill was placed, and the existing fill could have been placed as engineered fill. However, since we were not provided records that document the fill placement and compaction operations during placement, the existing fill is considered undocumented or uncontrolled and is not considered engineered fill.

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Based on the inherent variability within undocumented fill, grade-slabs and foundations which are constructed on or above undocumented fill are at a risk for unsuitable performance such as excessive settlements and cracking. Based on the boring, the existing fill can be considered for floor slab support, provided SME is retained to provide construction materials testing, and the additional risks described below are acceptable to the owner. Foundations should extend through the existing fill to bear on limestone rock or natural soils underlying the existing fill. Foundations may also bear on engineered fill placed over rock or suitable natural soils once any existing fill is removed (i.e., undercut).

There are additional risks of settlement and cracking of grade slabs placed on or above undocumented fill. However, based on the conditions encountered within the boring, and provided the subgrade is prepared as indicated in the following sections, we believe these risks are relatively low. If this risk is not considered acceptable, the existing fill should be removed to expose limestone rock or suitable natural soils and then the undercut excavation backfilled with engineered fill.

SME must be present during site preparation and construction to observe the condition of the existing fill, and to probe and test areas of existing fill with hand-operated equipment, if necessary. If SME is not present during site preparation and construction, we recommend the existing fill be completely removed and replaced with engineered fill. Existing fill to be left in-place for support of pavements, floor slabs, and engineered fill should be of sufficient strength and free of deleterious materials such as excessive debris or organics. Existing fill that is not suitable for support of grade-slabs should be improved by compaction-in-place, or undercut and replaced with engineered fill.

4.1.2 ROCK ELEVATION CONSIDERATIONS

Weathered limestone rock was encountered at the boring location beginning at about elevation 580 feet.

Due to site access constraints, only one boring was performed for this evaluation. Therefore, we could not verify potential variations in the top of rock elevation across the site. However, top of rock elevations should be expected to vary across the proposed building footprint. Based on the referenced historic plan set, top of rock was encountered at about elevations 568 to 572 feet at borings performed along the lake shore, just south of the proposed comfort station building. These top of rock elevations are 8 to 12 feet lower than the top of rock encountered in the one boring performed for this evaluation. However, it is possible rock was previously removed in the area of the historic borings during previous construction at the marina.

Since the proposed FFE of the new building will be about 583 feet, the bearing elevation for new shallow spread footings will be close to the top of rock elevation encountered at the boring. Since the top of rock elevation should be expected to vary across the site, the contractor should be prepared to perform rock excavation to construction foundations. Provisions should be included in the project specifications for rock excavation.

SME recommends performing a series of test pits at the site after demolishing of the existing building to further evaluate variations in rock elevations across the footprint of the planned comfort station. The information from the test pits can be used to estimate rock excavation quantities.

4.1.3 SITE SUBGRADE PREPARATION

The proposed FFE of the new comfort station building is about 583 feet, and the record water level (according to our review of USACE records) of Lake Huron is about 582.3 feet, which was observed in 1985. Therefore, the proposed FFE is about 8 inches above the record water level of the adjacent lake.

In the event the water level of Lake Huron rises above the record water level, or to even near the record water level, we believe there is a potential for groundwater to enter the new comfort station. Also, the comfort station would likely not be accessible in the event of record high water levels since the access walkway along the south side of the building would be under water. Therefore, we believe consideration should be given to raising the comfort station FFE to reduce the risks of flood damage in the event that record high water levels are observed on the lake in the future.

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The existing comfort station building and associated foundations, grade slabs, and pavements should be completely removed across the site. Existing utilities within the proposed building footprint should also be completely removed and the rerouted around the structure. Care should be exercised when excavating near existing utilities to protect them from damage.

After building demolition, any remaining pavements, concrete, topsoil, trees, shrubs, unsuitable fill, and other surface materials should be removed to expose the underlying subgrade soils within the new building area and within areas to receive engineered fill. Since the proposed building FFE is about 5 feet lower than the existing building FFE, we anticipate cuts of as much as 8 feet will be required along the north side of the proposed building, adjacent to the sidewalk along Main Street, to construct new shallow spread foundations. Temporary earth retention will be required to protect the existing sidewalk and roadway during construction. Feasible types of temporary earth retention are discussed in Section 4.5.

After clearing in the proposed building area, the test pit exploration outlined above in Section 4.1.2 should be implemented to further evaluate the top of rock elevations across the site and the extent and condition of the existing fill. As indicated above, existing fill should be completely removed (i.e., undercut) from below proposed foundations. We anticipate most of the existing fill may be able to remain below grade slab areas, provided the existing fill is further evaluated and improved as necessary and unsuitable areas of existing fill are undercut and backfilled with engineered fill. If SME is not retained to evaluate the existing fill during site preparation, we recommend all existing undocumented fill be removed and replaced with engineered fill.

After building demolition, stripping and removal of deleterious materials, and after cuts are made to design subgrade levels, we recommend the exposed subgrade soils be observed and testing to verify suitability for support of proposed improvements. Based on the tight site constraints, we do not think the exposed subgrade will be accessible for evaluation with large proofrolling equipment. Therefore, we anticipate the suitability of the exposed subgrade will need to be evaluated with hand-operated equipment such as a dynamic cone penetrometer (DCP) and hand augers. Areas of unsuitable subgrade revealed during this evaluation should be mechanically improved (compacted) in-place. If it is not possible to compact the unsuitable subgrade, it may be necessary to remove the unsuitable soils and replace them with engineered fill. Special attention should be directed to areas of existing fill (if any) during evaluation of the exposed subgrade. Suspect areas of existing fill revealed by testing with hand-operated equipment should be further evaluated by extending shallow test pits into the fill.

After the exposed subgrade is further evaluated and improved as necessary, engineered fill may be placed on the prepared subgrade to establish final design subgrade levels. Section 4.1.4 of this report presents materials and compaction requirements for engineered fill used to backfill undercuts in the building area, and for engineered fill to raise existing site grades as needed.

We recommend providing a minimum 6-inch-thick slab subbase consisting of an approved MDOT Class II granular material, to provide a leveling surface for construction of the slab, and a moisture capillary break between the slab and the underlying soils. MDOT 21AA dense-graded aggregate can be used as subbase material, instead of the Class II granular material, for improved stability and greater resistance to disturbance due to construction traffic. However, the thickness of dense-graded aggregate needed to protect the subgrade will depend on the time of year, the condition of subgrade soils during construction, and the type and volume of construction equipment to traffic the prepared subgrade. The granular material (or aggregate material if used) must also be compacted per Section 4.1.4 of this report.

We also recommend a vapor retarder be provided below floor slabs that are to receive an impermeable floor finish/seal or a floor covering that would retard vapor transmission. The location of the vapor retarder (relative to the subbase) should be determined by the Architect/Engineer based on the intended floor usage, planned finishes, and ACI recommendations. Floor slabs should also be separated by isolation joints from structural walls to permit relative movement. A minimum of 6 inches of engineered fill between the bottom of the slab and the top of the shallow foundations below is recommended.

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4.1.4 ENGINEERED FILL REQUIREMENTS

Fill placed within the construction area, including utility trench backfill, should be an approved material, free of frozen soil or other deleterious materials. The fill should be spread in level layers not exceeding 9 inches in loose thickness and be compacted to a minimum of 95 percent of the maximum dry density as determined in accordance with the Modified Proctor test. Sand fill should be compacted with a smooth drum vibratory roller or vibratory plate compactor including either a walk-behind type compactor, or a plate compactor mounted on a backhoe or excavator (hoe-pac). Based on the granular nature of the upper site soils, the use of imported clay fill is not recommended for use at this site.

The existing fill encountered in the boring is generally considered suitable for reuse as engineered fill. If the proposed fill contains more than 4 percent organics, or excessive limestone pieces greater than about 4 inches in diameter, we recommend such soils not be used for engineered fill. In the case where oversize pieces of limestone are present in the proposed fill material, a screen may be used to separate the oversize materials from the remainder of the fill so that the processed material may be used for engineered fill. For relatively dry granular material, water may need to be added to allow for proper compaction. We recommend imported fill meet MDOT Class II granular material requirements.

In confined areas (e.g., utility trenches) and other areas where compaction is accomplished primarily by hand-operated equipment, or where drainage is required, an approved MDOT Class II granular material should be used as backfill. Thinner lifts will be required to achieve suitable compaction of the backfill in areas where smaller walk-behind type compactors are used.

Coarse crushed aggregate used to backfill undercuts or to stabilize subgrades should consist of a well-graded crushed natural aggregate or crushed concrete ranging from 1 to 3 inches in size with no more than 7 percent by weight passing the No. 200 sieve. In cases where granular engineered fill will be placed over the coarse crushed aggregate with a thickness of more than 1-foot, the surface of the coarse crushed material should be choked with a layer of at least 6 inches of MDOT 21AA dense-graded aggregate or covered with a suitable non-woven geotextile fabric to mitigate the potential for migration of the granular engineered fill into the coarser crushed material.

4.2 FOUNDATIONS

Shallow spread foundations bearing on suitable limestone or natural soils are recommended to support the proposed structures. Shallow foundations may also bear on engineered fill placed over suitable natural soils or limestone. For shallow spread foundations bearing on these materials, a maximum net allowable soil bearing pressure of 3,000 pounds per square-foot (psf) may be used for design. Although a higher net allowable soil bearing pressure could be used to design shallow foundations bearing directly on the limestone, it is likely soil will be encountered at the design bearing level in some areas due to variations in the rock elevation across the site. This design bearing pressure is based on providing a global safety factor of three or more.

Suitable limestone was encountered about 6 feet beneath the ground surface at the boring, which corresponds to approximate elevation 580 feet. For constructability, we recommend the design bearing elevation be situated no lower than the Lake Huron water level.

To verify suitable subgrade is exposed at the bearing surface of shallow spread foundations, SME should evaluate foundation subgrades during construction. Existing fill encountered at the design bearing level should be undercut and replaced with engineered fill. Unsuitable natural soils encountered at the design bearing level should be either improved by compaction-in-place or undercut to expose suitable soils below. Since we anticipate the design bearing level will not be significantly higher than the water level of Lake Huron, undercutting of unsuitably natural soils could be difficult due to the presence of groundwater.

Recommendations for undercutting and/or subgrade improvement should be provided by SME on a case by case basis. We recommend a coarse crushed aggregate as described in Section 4.1.4 be available at the site to backfill undercuts that may extend below the site groundwater level.

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Once each foundation area is exposed, foundation subgrade conditions should be observed and tested by SME to verify suitable soils are encountered or improvements are performed as needed prior to backfilling and foundation construction. SME should be at the construction site to perform tests at foundation locations to observe the condition of the subgrade and verify the bearing pressure prior to constructing the foundations.

The 2015 Michigan Building Code (MBC) does not indicate a minimum footing depth below final site grade for frost protection where shallow foundations bear directly on rock. However, due to the potential for variation in rock elevations across the site, it is likely shallow foundations will bear on natural soils or on engineered fill in some areas. On that basis, we recommend shallow spread foundations be situated a minimum of 42 inches below final site grades for protection from frost action in normal winters. To reduce forces on the sides of shallow spread foundations from frost heave, the foundations must be constructed with vertical sides. If vertical excavation sidewalls cannot be maintained in foundation excavations, it will be necessary to slope back the excavations and use concrete formwork used to construct the foundations.

For bearing capacity and settlement considerations, continuous (wall) foundations should have a minimum width of 18 inches and isolated spread (column) foundations should have a minimum dimension of 30 inches. In some cases, the minimum foundation size criteria may govern the size of the shallow spread foundation and not the allowable soil bearing pressure.

Total settlements for shallow spread foundations bearing directly on limestone are estimated to be negligible. However, some total foundation settlement should be expected for foundations bearing on natural soils or engineered fill overlying the limestone. Natural soils were not encountered above the limestone in the boring. However, assuming foundations may bear on no more than about 5 feet of engineered fill or natural soils overlying rock and provided SME is present on site to test foundation subgrades, we anticipate total foundation settlement can be limited to about ½-inch, or less. Therefore, where footings transition from bearing on rock to bearing on soil, differential settlements could approach ½-inch. The settlement estimate provided is based on the boring information, maximum net allowable soil bearing pressure, our experience with similar structures and soil conditions, and field verification of suitable bearing soils by SME.

4.3 BELOW-GRADE WALLS AND DRAINAGE

The northern portion of the proposed building will extend as much as about 5 feet below grade.

Therefore, the north wall of the building and portions of the east and west walls will serve as below-grade walls to provide grade separation between the building FFE and higher grades on the building exterior.

We recommend the below-grade walls are backfilled with MDOT Class II granular material extending a minimum of two feet horizontally from the backside of the walls. Wall backfill should be compacted to a minimum of 95 percent of the maximum dry density as determined by the Modified Proctor test. Care should be exercised during compaction of the wall backfill to avoid overstressing the walls. The soil pressure below is based on properly placed and compacted backfill that meets the gradational requirements of MDOT Class II granular material. For purposes of design, we recommend using a unit weight of 115 pounds per cubic-foot (pcf) and a friction angle of 32 degrees for the compacted backfill.

For a drained granular backfill and a level finish surface behind the wall, an at-rest equivalent fluid pressure of 55 pcf should be used for the design of rigid walls. Additional lateral pressures due to surcharge loading, such as adjacent floor or column loads, stored materials, or traffic loads, should be added to the above lateral earth pressure for design. We recommend using a horizontal coefficient of 0.5 for at-rest conditions to calculate loads on walls due to surcharges. Use of this value requires a granular wall backfill. Surcharge loads should be modeled as a uniform pressure distribution applied to the entire wall height.

The earth pressure presented above is for a drained backfill. To reduce the potential for the build-up of hydrostatic pressure behind the walls, we recommend drains be installed along the base of the retained soil side of the walls. The drains should consist of a minimum 6-inch-diameter perforated plastic drain pipe, wrapped with a filter fabric and surrounded by six inches of a filter material, such as pea gravel

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(MDOT 34G or MDOT 34R), wrapped with a filter fabric. The drains should be discharged to a gravity drainage outlet, if feasible. We recommend surface water be directed away from wall backfill areas, and that roof downspouts not be allowed to discharge onto the ground surface behind below-grade walls. We also recommend the use of a waterproofing material on the backfill side of the below-grade walls rather than a dampproofing material. The waterproofing material will provide for less potential for moisture-vapor transmission through the walls and into the building compared to the use of a dampproofing material. The waterproofing will also mitigate the risk of leakage into the building if there are localized areas in the backfill where water ponds temporarily before being collected and drained by the recommended drainage system.

4.4 SEISMIC SITE CLASS

Section 1613.3.1 of the 2015 MBC states, “The parameters Ss and S1 shall be determined from the 0.2 and 1-second spectral response accelerations shown on Figures 1613.3.1(1) through 1613.3.1(8).

Where S1 is less than or equal to 0.04g and SS is less than or equal to 0.15g, the structure is permitted to be assigned to Seismic Design Category A.”

For this site location, the mapped short-period spectral response acceleration, SS, and mapped spectral response acceleration at 1-second period, S1, is 0.051g (less than or equal to 0.15g) and 0.023g (less than or equal to 0.04g), respectively. Therefore, a seismic Site Class does not need to be provided for this site and a Seismic Design Category A structure can be designed for this project according to the 2015 MBC note above.

4.5 TEMPORARY EARTH RETENTION

A temporary earth retention system (TERS) will be required along the north side of the side to protect the adjacent sidewalk and Main Street during construction. We anticipate the excavation for construction of the new comfort station will extend about 8 feet below the adjacent sidewalk. Several types of TERS’s could be considered for use at this site. Based on the boring, we anticipate either a soil nail wall or a soldier pile and lagging system are feasible.

Soil nail walls consist of a series of steel anchors or “nails” that are inserted into holes extending from the wall face into the retained soil zone and then grouted in place. The exposed soil at the wall face is than covered with a reinforced shotcrete skin, and the soil nails locked-off onto this skin. This type of wall is constructed from the top down in stages. Enough soil is excavated in each stage to allow for installation of soil nails and placement of shotcrete before additional soil is excavated. This installation process is repeated until the design wall depth is reached. Soil nailing equipment is relatively small which would be a benefit due to site constraints and logistics of getting equipment on and off the island. Since the soil nails would extend beneath the roadway, a permit from MDOT would be required. In addition, the location and depth of underground utilities in the design reinforcement zone must be accurately determined to avoid conflict with the soil nails. Soil nail walls are installed by specialty contractors.

Soldier pile and lagging walls typically consist of vertical H-piles that are drilled or driven at regular intervals along the edge of the planned excavation. Lagging consisting of wood, steel or precast concrete panels is inserted behind the front pile flanges as the excavation proceeds downward. The lagging resists the load of the retained soil and transfers it to the soldier piles. The walls can be designed as cantilever walls or receive additional lateral support from anchors or bracing. Based on the shallow limestone depth at the site, we anticipate relatively large pile driving or drilling equipment will be required to obtain sufficient embedment of the soldier piles into the limestone. Pile driving is noisy and generates vibrations that can cause settlement of nearby structures. Therefore, for this project, driving of soldier piles should be prohibited and soldier piles should be installed by drilling methods.

The TERS selected for this project must be designed by a licensed engineer with experience in TERS design. The TERS must be constructed by a contractor with experience in similar TERS construction.

Typically, a TERS is procured by issuing a performance specification for the work, and contractors submit proposals for a TERS that is geared to their expertise. The design for a TERS is also typically prepared by an engineer that is retained directly by the selected TERS contractor.

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4.6 CONSTRUCTION CONSIDERATIONS

We do not expect significant groundwater seepage into excavations that remain above the water level of Lake Huron. However, seepage from perched sources and runoff could be encountered at higher elevations. We anticipate standard sump pit and pumping procedures will be adequate to control these accumulations, on a localized basis. Higher-capacity dewatering techniques will be required to control groundwater accumulations in excavations in sands that extend more than about one foot below the groundwater level. A working surface of crushed aggregate or crushed concrete may be required to protect the exposed subgrade where groundwater is present.

As indicated in Section 4.1.2, the contractor should be prepared to perform rock excavation due to the potential variation in rock elevations across the site.

The contractor must provide a safely sloped excavation or an adequately constructed and braced shoring system in accordance with federal, state and local safety regulations for individuals working in an excavation that may expose them to the danger of moving ground. If material is stored or heavy equipment is operated near an excavation, use appropriate shoring to resist the extra pressure due to the superimposed loads.

The contractor must take precautions to protect adjacent improvements during construction for this project. Care must be exercised during the excavating and compacting operations so that excessive vibrations do not cause settlement of existing utilities or other improvements, and to avoid undermining existing improvements during site excavations. The temporary earth retention along the north side of the site must be design by a licensed engineer that is experienced with earth retention design.

Handling, transportation and disposal of excavated materials and groundwater should be performed in accordance with applicable regulatory requirements.

APPENDIX A

BORING LOCATION DIAGRAM (FIGURE NO. 1)

BORING LOG TERMINOLOGY

BORING LOG (B1)

B1

Project

Project Location

Sheet Name www.sme-usa.com

CADD

Scale

Project

No.

Revision Date

Designer

Date

S m e i n c p z W

I P

C

A D

D

W G

S B

L D r e v

B

L D d w g

NO REPRODUCTION SHALL BE MADE WITHOUT THE PRIOR

CONSENT OF SME

c

DRAWING NOTE: SCALE DEPICTED IS MEANT FOR 11" X 17"

AND WILL SCALE INCORRECTLY IF PRINTED ON ANY

OTHER SIZE MEDIA

Figure No.

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D

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D e c p m r i o s

MACKINAC ISLAND

COMFORT STATION

MACKINAC ISLAND

STATE HARBOR,

MICHIGAN

BORING LOCATION

DIAGRAM

12/20/2018

JGR

PEA

1" = 10'

080599.00

0'

GRAPHIC SCALE: 1" = 10'

10' 20'

LOCATION MAP

NOT TO SCALE

APPROXIMATE BORING LOCATION

LEGEND

NOTE:

BASE DRAWING INFORMATION WAS TAKEN FROM THE

DRAWING TITLED “EXISTING FLOOR PLAN” DATED

NOVEMBER 27, 2018, PREPARED BY WTA ARCHITECTS FOR

THE MACKINAC ISLAND STATE HARBOR PROPOSED NEW

COMFORT STATION.

SITE

M

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IN

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F

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S

EXISTING COMFORT STATION

AutoCAD SHX Text

NORTH

AutoCAD SHX Text

NORTH

Determine percentages of sand and gravel from grain-size curve.

Depending on percentage of fines (fraction smaller than No. 200 sieve size), coarse-grained soils are classified as follows:

Less than 5 percent……………………..……...GW, GP, SW, SP More than 12 percent……………………..…….GM, GC, SM, SC 5 to 12 percent……………...……..Cases requiring dual symbols

SP-SM or SW-SM (SAND with Silt or SAND with Silt and Grav-

el) SP-SC or SW-SC (SAND with Clay or SAND with Clay and

Gravel) GP-GM or GW-GM (GRAVEL with Silt or GRAVEL with Silt and

Sand) GP-GC or GW-GC (GRAVEL with Clay or GRAVEL with Clay and Sand)

If the fines are CL-ML:

SC-SM (SILTY CLAYEY SAND or SILTY CLAYEY SAND with Gravel)

SM-SC (CLAYEY SILTY SAND or CLAYEY SILTY SAND with Gravel)

GC-GM (SILTY CLAYEY GRAVEL or SILTY CLAYEY GRAVEL with Sand)

GM-GC (CLAYEY SILTY GRAVEL or CLAYEY SILTY GRAVEL with Sand)

UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART

COARSE-GRAINED SOIL

(more than 50% of material is larger than No. 200 sieve size.)

GRAVEL

More than 50% of coarse fraction larger than No. 4 sieve size

Clean Gravel (Less than 5% fines)

GW

Well-graded gravel;

gravel-sand mixtures, little or no fines

GP

Poorly-graded gravel;

gravel-sand mixtures, little or no fines

Gravel with fines (More than 12% fines)

GM

Silty gravel; gravel-sand-silt mixtures

GC

Clayey gravel; gravel-sand-clay mixtures

SAND

50% or more of coarse fraction smaller than No. 4 sieve size

Clean Sand (Less than 5% fines)

SW

Well-graded sand; sand-gravel mixtures, little or no fines

SP

Poorly graded sand;

sand-gravel mixtures, little or no fines

Sand with fines (More than 12% fines)

SM

Silty sand; sand-silt-gravel mixtures

SC

Clayey sand; sand–clay-gravel mixtures

FINE-GRAINED SOIL

(50% or more of material is smaller than No. 200 sieve size)

SILT

AND

CLAY

Liquid limit less than

50%

ML

Inorganic silt; sandy silt or gravelly silt with slight plasticity

CL

Inorganic clay of low plasticity; lean clay, sandy clay, gravelly clay

OL

Organic silt and organic clay of low plasticity

SILT

AND

CLAY

Liquid limit

50% or greater

MH

Inorganic silt of high plasticity, elastic silt

CH

Inorganic clay of high plasticity, fat clay

OH

Organic silt and organic clay of high plasticity

HIGHLY

ORGANIC

SOIL

PT

Peat and other highly organic soil

LABORATORY CLASSIFICATION CRITERIA

GW

D60 D30

CU = greater than 4; CC = between 1 and 3 D10 D10 x D60

GP Not meeting all gradation requirements for GW

GM

Atterberg limits below “A” line or PI less than 4

Above “A” line with PI between 4 and 7 are borderline cases requiring use of dual symbols GC

Atterberg limits above “A” line with PI greater than 7

SW

D60 D30

CU = greater than 6; CC = between 1 and 3 D10 D10 x D60

SP Not meeting all gradation requirements for SW

SM

Atterberg limits below “A” line or PI less than 4 Above “A” line with PI between 4 and 7 are borderline cases requiring use of dual symbols SC

Atterberg limits above “A” line with PI greater than 7

BORING LOG TERMINOLOGY

LIQUID LIMIT (LL) (%)

PLASTICITY CHART

DRILLING AND SAMPLING ABBREVIATIONS

2ST – Shelby Tube – 2” O.D.

3ST – Shelby Tube – 3” O.D.

AS – Auger Sample GS – Grab Sample LS – Liner Sample NR – No Recovery PM – Pressure Meter RC – Rock Core diamond bit. NX size, except where noted SB – Split Barrel Sample 1-3/8” I.D., 2” O.D., except where noted VS – Vane Shear WS – Wash Sample

OTHER ABBREVIATIONS

WOH – Weight of Hammer WOR – Weight of Rods SP – Soil Probe PID – Photo Ionization Device FID – Flame Ionization Device

PARTICLE SIZES

Boulders - Greater than 12 inches Cobbles - 3 inches to 12 inches Gravel- Coarse - 3/4 inches to 3 inches Fine - No. 4 to 3/4 inches Sand- Coarse - No. 10 to No. 4 Medium - No. 40 to No. 10 Fine - No. 200 to No. 40 Silt and Clay - Less than (0.0074 mm)

DEPOSITIONAL FEATURES

Parting – as much as 1/16 inch thick Seam – 1/16 inch to 1/2 inch thick Layer – 1/2 inch to 12 inches thick Stratum – greater than 12 inches thick Pocket – deposit of limited lateral extent Lens – lenticular deposit Hardpan/Till – an unstratified, consolidated or cemented mixture of clay, silt, sand and/or gravel, the size/shape of the constituents vary widely

Lacustrine – soil deposited by lake water

Mottled – soil irregularly marked with spots of different colors that vary in number and size

Varved – alternating partings or seams of silt and/or clay

Occasional – one or less per foot of thickness Frequent – more than one per foot of thickness Interbedded – strata of soil or beds of rock lying between or alternating with other strata of a different nature

VISUAL MANUAL PROCEDURE

When laboratory tests are not performed to confirm the classifica-tion of soils exhibiting borderline classifications, the two possible classifications would be separated with a slash, as follows:

For soils where it is difficult to distinguish if it is a coarse or fine-grained soil:

SC/CL (CLAYEY SAND to Sandy LEAN CLAY) SM/ML (SILTY SAND to SANDY SILT) GC/CL (CLAYEY GRAVEL to Gravelly LEAN CLAY) GM/ML (SILTY GRAVEL to Gravelly SILT)

For soils where it is difficult to distinguish if it is sand or gravel, poorly or well-graded sand or gravel; silt or clay; or plastic or non-plastic silt or clay:

SP/GP or SW/GW (SAND with Gravel to GRAVEL with Sand) SC/GC (CLAYEY SAND with Gravel to CLAYEY GRAVEL with

Sand) SM/GM (SILTY SAND with Gravel to SILTY GRAVEL with

Sand) SW/SP (SAND or SAND with Gravel) GP/GW (GRAVEL or GRAVEL with Sand) SC/SM (CLAYEY to SILTY SAND) GM/GC (SILTY to CLAYEY GRAVEL)

CL/ML (SILTY CLAY)

ML/CL (CLAYEY SILT)

CH/MH (FAT CLAY to ELASTIC SILT) CL/CH (LEAN to FAT CLAY) MH/ML (ELASTIC SILT to SILT) OL/OH (ORGANIC SILT or ORGANIC CLAY)

OTHER MATERIAL SYMBOLS

Topsoil

Void

Sandstone

Asphalt

Glacial Till

Siltstone

Base

Coal

Limestone

Concrete

Shale

Fill

CLASSIFICATION TERMINOLOGY AND CORRELATIONS

Cohesionless Soils

Relative Density N-Value (Blows per foot)

Very Loose Loose Medium Dense Dense Very Dense Extremely Dense

0 to 4 4 to 10 10 to 30 30 to 50 50 to 80 Over 80

Standard Penetration ‘N-Value’ = Blows per foot of a 140-pound hammer falling 30 inches on a 2-inch O.D. split barrel sampler, except where noted.

Cohesive Soils

Consistency N-Value

(Blows per foot) Undrained Shear Strength (kips/ft2)

Very Soft Soft Medium Stiff Very Stiff Hard

0 - 2 2 - 4 4 - 8

8 - 15 15 - 30 > 30

0.25 or less

0.25 to 0.50

0.50 to 1.0

1.0 to 2.0

2.0 to 4.0

4.0 or greater

CL

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IC

IT

Y

I N

D E

X

P I)

0 10 20 30 40 50 60 70 80 90 100

CH

A LINE

PI=0.73 (LL-20)

MH & OH

ML & OL CL+ML

50/5"

100/4"

0.3

0.9

6.0

10.0

3" of BRICK PAVERS

6" of SAND FILL

FILL - LIMESTONE Fragments and Pieces with Sand and Clay- Occasional Brick Fragments- Brown- Medium Dense (GP)

Weathered LIMESTONE- Brown

END OF BORING AT 10.0 FEET.

SB1

SB2

SB3

SB4

DATE STARTED: 12/13/18 COMPLETED: 12/13/18

LOGGED BY: KJR CHECKED BY: JLN

BORING METHOD: Hollow-stem Augers

RIG NO.: CME750DRILLER: TR-Brax Drilling

GROUNDWATER & BACKFILL INFORMATION

GROUNDWATER WAS NOT ENCOUNTERED

NOTES: 1. The indicated stratification lines are approximate. In situ, the transition between materials may be gradual.

2. Brick pavers at the ground surface were removed prior to drilling and replaced upon completion of drilling.

MCPL LL

BACKFILL METHOD: Auger Cuttings

R

EC

O

VE

R Y

LE

N

G

TH

(I N

C H

ES

BORING B 1

E

LE

V

A T

IO

N

F

E E

T

BL

O

W S

PE

R

SI

X

IN

C

H

ES

N-VALUE --

10 20 30 40

PROJECT LOCATION: Mackinac Island State Harbor, Michigan

PROJECT NAME: Mackinac Island Comfort Station PROJECT NUMBER: 080599.00

CLIENT: WTA Architects

S Y

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F

IL

E

SURFACE ELEVATION: 586± FT

PROFILE DESCRIPTION

DRY DENSITY

(pcf) --

90 100 110 120

MOISTURE &

ATTERBERG

LIMITS (%)

10 20 30 40

TRIAXIAL (UU)

HAND PENE.

VANE SHEAR (REM)

UNC.COMP.

REMARKS

SHEAR

STRENGTH (KSF)

1 2 3 4

TORVANE SHEAR

VANE SHEAR (PK)

SA

M

PL

E

TY

PE

/N O

IN

TE

R

VA

L

D E

P T

H

F E

E T

50+

100+

585.7

585.1

580.0

576.0

APPENDIX B

IMPORTANT INFORMATION ABOUT THIS GEOTECHNICAL ENGINEERING REPORT

Geotechnical-Engineering Report Important Information about This

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

While you cannot eliminate all such risks, you can manage them. The following information is provided to help.

The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, clients can benefit from a lowered exposure to the subsurface problems that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed below, contact your GBA-member geotechnical engineer.

Active involvement in the Geoprofessional Business Association exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Geotechnical-Engineering Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client. Those who rely on a geotechnical-engineering report prepared for a different client can be seriously misled. No one except authorized client representatives should rely on this geotechnical-engineering report without first conferring with the geotechnical engineer who prepared it. And no one

– not even you – should apply this report for any purpose or project except the one originally contemplated.

Read this Report in Full Costly problems have occurred because those relying on a geotechnical engineering report did not read it in its entirety. Do not rely on an executive summary. Do not read selected elements only. Read this report in full.

You Need to Inform Your Geotechnical Engineer about Change Your geotechnical engineer considered unique, project-specific factors when designing the study behind this report and developing the confirmation-dependent recommendations the report conveys. A few typical factors include:

Typical changes that could erode the reliability of this report include those that affect:

As a general rule, always inform your geotechnical engineer of project changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.

This Report May Not Be Reliable Do not rely on this report if your geotechnical engineer prepared it: