10-12 Exeter (Wyoming Traynor) Midlantic Eng Prelim Geotech Mine Analysis 06-23-2022.pdf

MIDLANTIC ENGINEERING, INC.

120 COMMERCE ROAD

PITTSTON TOWNSHIP, PA 18640-9552

GEOTECHNICAL ENGINEERING REPORT

PRELIMINARY GEOTECHNICAL ENGINEERING REPORT

DEVELOPMENT SITE

1800 WYOMING AVENUE

EXETER TOWNSHIP, PA

(Project #22111)

PREPARED FOR:

SUMMIT REALTY ADVISORS, LLC

201 SOUTH MAPLE AVENUE

SUITE 100

AMBLER, PA 19002

JUNE 23, 2022

120 Commerce Road • Pittston Twp., PA 18640-9552 • 570/655-2200 (phone) • midlaneng@aol.com

June 23, 2022

Summit Realty Advisors, LLC 201 South Maple Avenue Suite 100 Ambler, PA 19002

ATTENTION: Mr. John Cogan jcogan@summitrealtyadvisors.com

REFERENCE: Preliminary Geotechnical Engineering Report (#22111) Development Site

1800 Wyoming Avenue Exeter Township, PA

Mr. Cogan:

Submitted herewith is our preliminary geotechnical engineering report for the above referenced project. Our services have been performed in accordance with our proposal/agreement dated June 8, 2022 and your subsequent authorization to proceed.

The proposed development is a multi-acre complex located to the north of Wyoming Avenue in Exeter, Pennsylvania. The site is expected to be developed for several commercial type buildings with associated infrastructure and pavement areas.

1. SCOPE OF SERVICES

Services performed for this phase of the study included site reconnaissance, review of geologic mapping, review of archived geotechnical engineering studies in the vicinity of the site, and preparation of our report. Our preliminary geotechnical engineering report for the development site includes the following:

a. Review of available mining survey data to determine the extent of previous mining operations and possible effects on proposed developments.

b. Our evaluation of the estimated subsurface conditions within the proposed development areas based on mapping reviews and site reconnaissance.

c. Preliminary assessment of foundation requirements for support of low-rise buildings and floor slabs-on-grade.

mailto:jcogan@summitrealtyadvisors.com

d. Comments regarding geotechnical construction methods that should be considered both in the preliminary design and in the development of construction plans and specifications.

e. Recommendations for study programs and geotechnical engineering report requirements to address specifically proposed developments.

Services with respect to environmental considerations, wetlands investigations, specific building foundation designs, erosion control, pavement sections, construction cost or quantity estimates, and construction observation and testing are not included in the scope of services under this phase study.

2. DESCRIPTION OF SITE AND PROPOSED DEVELOPMENTS

The proposed development is about a 15-acre parcel located north of Wyoming Avenue in Exeter Township, Luzerne County, Pennsylvania. The project vicinity is indicated on the 1994 USGS map included as Figure No. 1-1 and on a 2019 aerial map included as Figure No. 1-2 in Enclosure (1).

The site is generally cleared or lightly wooded. Portions of the site have been altered by previous site grading activities and infrastructure improvements for previous use of the site as a trailer park. Existing surface grades slope down very gently from northwest to southeast.

The planned development of the site is to include small commercial buildings and related infrastructure. The anticipated buildings will be single-story with slab-on-grade and no basement levels. A site concept plan provided to us for this preliminary study is included for reference as Figure No. 1-3 in Enclosure (1).

The information listed above was provided to us by your office or was obtained during our own site visits.

3. ANTICIPATED SUBSURFACE CONDITIONS

For initial evaluation of subsurface conditions in the proposed development areas, a full site reconnaissance was completed, historical photo documentation was reviewed, soils and geologic mapping were reviewed, and mine mapping was reviewed.

A shallow depth of existing fill materials is expected across the site related to past site grading and site usage. The fill materials may average about 2 feet in depth on the south and east sides of the site and increase to 6 to 8 feet in depth at the northwest side of the site. The composition of the fill materials will be granular shale and silty sand materials of breaker refuse.

The underlying natural soil deposits will be sand and gravel soils and represent glacial outwash deposits of the Pleistocene geologic epoch. These natural soils are moderately over-consolidated. The SCS mapping of the development area is included as Figure No. 2-1 and the surficial geology mapping of the project vicinity is included as Figure No. 2-2 in Enclosure (2).

The underlying bedrock consists of interbedded sandstone, shale, conglomerate, and anthracite coal. This sedimentary rock represents the Llewellyn formation of the Pennsylvanian geologic age. The bedrock geologic mapping of the site is included as Figure No. 2-3 in Enclosure (2).

Mining maps were reviewed at the Department of the Interior’s Office of Surface Mining to study the previous surface and subsurface mining activities in the project area

Subsurface mining was performed through the study area. The subsurface mining was generally completed in the early 1900s by room-and-pillar methods. The sequence of the uppermost mined coal measures within the development area is indicated in the following table:

Item

Approximate Elevation

Comments ground surface El 570± slopes down gently from northwest to southeast top-of-rock El 460 to El 440± in excess of 100’ below original surface grades

Pittston vein El 320 to El 300± room-and-pillar mining; v=7’± Marcy vein El 250± room-and-pillar mining Top Clark vein El 170± room-and-pillar mining Bottom Clark vein El 125± room-and-pillar mining

The approximate extent of the proposed development areas are indicated on the surface mine map, the top-of-rock map, and the uppermost Pittston vein subsurface mine map, included in Enclosure (3). A projected mine level cross-section plan is also included in Enclosure (3).

The Mount Lookout Shaft #1 and Shaft #2 are located on the southwest end of the study site and extend to the Bottom Clark vein. The shafts have been fully backfilled.

4. PRELIMINARY FOUNDATION ENGINEERING REVIEW

Our preliminary foundation engineering review is based upon the subsurface information as developed by our review of geologic and mine mapping data, by the field reconnaissance program, and the site planning information furnished to us.

The building developments are planned as single-story buildings with slab-on-grade.

Shallow depths of excavation and structural fills will be required.

4.1 Assessment of Mining Conditions

Review of the mine mapping data indicates mining related structures of the Mount Lookout colliery on the west side of the site, including two vertical air shafts. None of the former mining related structures such as shafts, slopes, or drifts are noted within the immediate building areas of the preliminary development scheme.

The vertical shafts are noted on the full sequence of mine levels, referenced as the

Mount Lookout Shaft #1 and Shaft #2. The shafts have been backfilled to the surface.

Constructing buildings, other critical structures, or storm-water basins over the vertical shaft locations is not recommended. We recommend planning building and site planning configurations with a minimum 15 feet horizontal offset from the perimeter of vertical shaft locations.

We recommend an additional structural cap be constructed over the defined extent of the shafts. A reinforced structural concrete mat spanning the lateral extents of the shaft cribbing should be placed and further covered with an impermeable geotextile liner for support of grading aggregates. Continued monitoring of the shaft area for any signs of subsidence should be planned.

The profile to the uppermost subsurface mining levels of the Pittston vein includes an excess of 100’ of soil overburden and in excess of 100’ of interlayered sandstone and shale bedrock. The mining data and geologic conditions indicate the specific building areas of the study site will have a very low probability of future mining related subsidence events affecting the developments. The proposed developments will be at no higher risk of subsidence type events than the previous or exiting site developments. Based on conventional cost/risk considerations, no mine level remediation programs are deemed essential for support of the lightly loaded proposed developments.

4.2 Assessment of Foundation Alternatives

The most predominant site feature to consider for development planning is the extent and depths of the fill materials on site. The fill materials primarily consist of shale and coal fragment breaker refuse materials. No specific compaction efforts were noted to have been completed during deposition of this fill. The fill materials may be susceptible to consolidation with new loading or with the loading of new structures.

Conventional shallow foundations can be extended to the underlying natural soil subgrades.

In areas of deeper existing fill, we recommend an earthwork program including limited over-excavation of the existing fill materials and replacement with new compacted structural fill, or a ground improvement program of compacted aggregate piers, for support of conventional shallow spread footings of commercial buildings.

If high point load structures or structures of critical access were planned for specific areas of this site, deep foundations can be considered to transfer loads below existing fill materials. Specific systems and design capacities can be analyzed if required, based on loading data and locations.

4.3 Initial Structural Pad Preparations

We recommend all loose surficial topsoil materials and humus be removed from the structural loading areas prior to placement of structural fill. Tree stumps should be fully removed. We estimate the stripping depths within the construction areas will be in the range of 0.5 foot to 1.5 feet.

After the excavation of the topsoil and humus, the prepared fill subgrades should be observed and proof-rolled to determine the actual suitability of the material for support of new structural fill. Excessively soft or yielding areas should be further undercut to sound bearing and replaced with structural fill.

4.4 Shallow Foundations on Natural Subgrades

We anticipate compact silty sand and gravel soil subgrades at shallow to moderate depths. These natural soil subgrades are generally considered suitable for direct support of shallow foundations. We anticipate maximum allowable net design bearing pressures of about 3 ksf for footings founded on the natural soil materials.

4.5 Shallow Foundations on Compacted Structural Fill

In areas of deeper existing fill on the north and west sides of the site, footings may be planned at typical structural grades on a minimum depth of new compacted structural fill. New structural fill will be placed over compacted and improved existing fill subgrade materials. The new structural fill should be planned to extend to minimum depths of 2.0 feet below the constructed footing subgrade elevations.

After the minimum over-excavation of the fill materials, the prepared fill subgrades should be compacted and stabilized with AASHTO #1 coarse aggregate, using vibratory compaction equipment such as a hydraulic plate compactor. The hydraulic plate compactor used to re-compact the existing fill materials should have a minimum impulse force of 6,500 pounds and a minimum base plate dimension of 23 inch x 23 inch. Models of hydraulic plate compaction which meet these minimum requirements include Caterpillar Model CVP40, Kenco Model KC-20, Allied Model 1600, and TracPac Model MM140. We recommend the contractor be required to monitor adjacent structures for potential damage from compaction equipment. Any soft or yielding areas should be further stabilized with crushed stone aggregate fill.

After the prepared subgrades are stabilized, the footing subgrade over-excavation areas should be replaced with lifts of compacted coarse aggregate structural fill. Footings on compacted structural fill can be planned for a design bearing capacity of about 2 ksf.

4.6 General Shallow Foundation Design Considerations

For frost protection all exterior footings should be planned a minimum of 3.5 feet below adjacent exterior grades.

The site conditions and construction recommendations in this preliminary geotechnical engineering report indicate a seismic design classification of site class 'D', per IBC 2009 table 1613.5.2.

4.7 Alternate – Aggregate Pier Systems

Based on the anticipated composition and depths of the fill materials on the north and west ends of the property, aggregate pier foundations may be considered to reinforce the existing fill materials for support of spread footings. The aggregate pier support elements are constructed by drilling a hole to create a cavity, removing a volume of compressible soil or fill materials, then building a bottom bulb of clean open-graded stone while vertically pre-stressing and pre-straining soils underlying the bottom bulb. The aggregate pier is built on top of the bottom bulb, using well-graded base course stone placed in approximate 12- to 15-inch lifts. Densification of the bottom bulb and of the aggregate lifts is accomplished by using the impact ramming action of a modified hydraulic hammer. In addition to increasing shear resistance at the aggregate pier element perimeter, the increased horizontal stresses in the soil matrix make it more compact.

For this type of development, typical aggregate pier elements with shaft diameters of about 24 inches can be expected to provide a support capacity of 25 to 40 kips each.

The length of aggregate piers may vary with depths of existing fill across the site.

Shallow spread footings can be constructed at nominal depths for an allowable composite net bearing pressure of up to 4 ksf.

A construction monitoring program should be planned with the aggregate pier construction system to verify the depth, volume, and increase in density of the subgrade materials.

4.8 Floor Slabs

We generally anticipate depths of new compacted structural fill will be required to achieve subgrade levels for support of the floor slabs-on-grade. These materials are typically suitable for direct support of building floor slabs. We recommend a maximum design modulus of subgrade reaction of ks = 150 pci for design of concrete floor slabs-on-grade.

Floor slabs-on-grade should be planned with damp-proofing consisting of a granular base course serving as a capillary break. The base course should consist of a minimum of four inches (4”) of coarse open-graded gravel or crushed stone that is well graded between the ¾-inch and the No. 4 sieve size. PennDOT type #57, OGS, or 2A coarse aggregate is considered suitable for this purpose. Prior to placing the base course, the subgrade materials should be thoroughly proof-rolled and compacted on grade to densify and stabilize any areas that may have been disturbed by the preceding construction and exposure.

Areas of concrete floor slabs-on-grade where glued floor coverings are scheduled should be planned with a heavy polyethylene vapor barrier set on the prepared subgrade, below the subbase coarse aggregate. The vapor barrier should be properly installed and protected from damage or puncture. All seams, junctures at walls, and floor penetrations should be sealed to provide an impermeable barrier. A sub-floor aeration system may be considered to further minimize vapor emissions from the concrete slabs-on-grade.

5. RECOMMENDATIONS FOR ADDITIONAL STUDIES

Comprehensive geotechnical engineering analyses are recommended for specific structural element sizes and grades selected. Test borings or test pits may be considered to analyze soil conditions, rock depths, etc. Borings for the type of development being considered in this preliminary analysis should extend to depths of about 20 feet below proposed lowest construction grades.

The comprehensive geotechnical engineering analysis should include evaluation of foundation alternatives, lateral earth pressures, pavement design parameters, and drainage recommendations considering specific construction layout, grades, and loading data.

6. PRELIMINARY STUDY LIMITATIONS

We have prepared this report for the use of your office and the design professionals for preliminary planning purposes in accordance with generally accepted geotechnical engineering practices. No other warranties, either expressed or implied, are made as to the professional services included in this report.

We appreciate the opportunity to be of service to you for this project. Please do not hesitate to contact us for further clarification of any aspect of this study.

Sincerely, MIDLANTIC ENGINEERING, INC.

Timothy Burns, P.E.

President Encls:

(1) Site Plans

- Project Vicinity Plan – USGS 1994, Figure No. 1-1

- Project Vicinity Plan – Aerial 2019, Figure No. 1-2

- Site Concept Plan, Figure No. 1-3

(2) Geologic Mapping

- SCS Mapping, Figure No. 2-1

- Surficial Geology Mapping, Figure No. 2-2

- Bedrock Geology Mapping, Figure No. 2-3

(3) Mine Mapping

- Mine Map – Surface, Figure No. 3-1

- Mine Map – Top-of-Rock, Figure No. 3-2

- Mine Level Cross-Section, Figure No. 3-3

- Mine Map – Pittston Vein, Figure No. 3-4

Enclosure (1)

Drawing Title:

Project Vicinity Plan – USGS 1994 Development Site – 1800 Wyoming Avenue

120 Commerce Road • Pittston Township, PA 18640-9552

Drawn By:

LJ

Checked By:

TB

Scale:

1” = 1,000’

570/655-2200 (phone) • midlaneng@aol.com Date:

06/23/22

Project No.:

22111

Sheet No.

N

Figure No. 1-1

Project Vicinity

Scale:

Project Vicinity Plan – Aerial 2019

LJ

Checked By:

TB

Scale:

1” = 200’

570/655-2200 (phone) • midlaneng@aol.com Date:

06/23/22

Project No.:

22111

Figure No. 1-2

Approximate Property Line

Proposed Building

Proposed Building

Figure No. 1-3

Enclosure (2)

SCS Mapping

Exeter Township., PA

CD

Checked By:

TB

Scale:

as shown

570/655-2200 (phone) • midlaneng@aol.com Date:

06/23/22

Project No.:

22111

Figure No. 2-1

Map Unit Legend Symbol USCS Classifications

ChA – Chenango gravelly loam SM, GM, GW-GM

Mg – Mine Dump ---

CF – Cut/Fill Land ---

Scale:

Surficial Geology Mapping

CD

Checked By:

TB

Scale:

1” = 300’±

570/655-2200 (phone) • midlaneng@aol.com Date:

06/23/22

Project No.:

22111

Figure No. 2-2

Legend:

Wisconsinan Outwash – Stratified sand and gravel. The overall stratification is horizontal with individual strata showing cross-beds or ripples.

Coal Dump – Coal-breaker refuse piles and settling ponds. The refuse piles contain a mixture of coaly and non-coaly rock fragments.

Qwo

Qwo cd

Approximate Property Line

Proposed Building

Figure No. 2-3

Geologic Mapping

Exeter Township, PA Project:

21111 Date:

06/23/22 Scale:

as shown

Legend:

Llewellyn Formation – interbedded sandstone, siltstone, shale, conglomerate, and anthracite coal.

anticline fold pair fault

Pl

Mine Mapping – Surface

Exeter Township, PA Project:

22111 Date:

06/23/22 Scale:

1” = 100’

Enclosure (3) Figure No. 3-1

N

Approximate Property Line

Shaft

Shaft

Proposed Building

Mine Mapping – Top-of-Rock

Exeter Twp., PA Project:

22111 Date:

06/23/22 Scale:

1” = 100’

Enclosure (3) Figure No. 3-2

N

Approximate Property Line

Shaft

Shaft

Surface Elev.

Top of Rock Elev.

(typical)

LEGEND:

= Top of Rock

= Proposed Building

Mine Level Cross-Section

Exeter Township, PA Project:

22111 Date:

06/23/22 Scale:

1” = 100’

Enclosure (3) Figure No. 3-3

Approximate Property Line

N 35°W

Note: Approximate property line is 1,160 feet east of cross-section.

Mine Mapping – Pittston Vein

Exeter Township., PA Project:

22111 Date:

06/23/22 Scale:

1” = 100’

Enclosure (3) Figure No. 3-4

364.0●

LEGEND:

● = Mine Level Elevation

= Proposed Building

386.6●

303.6●

304.7●

319.8●

299.4●

301.8●

284.2●

334.9●

Shaft

Shaft

Approximate Property Line