W912PL19R0011_Amendment0001_Part8.pdf

Preliminary Geotechnical Report

AJO-CAG IFT Geotech Report (12-17-2014).docx

APPENDIX E -

IFT SITE SUMMARIES

Preliminary Geotechnical Report

E-1 AJO-CAG IFT Geotech Report (12-17-2014).docx

APPENDIX E - SITE SUMMARIES

This appendix contains a summary of the geotechnical services for each Integrated Fixed Tower

(IFT) site. Each site summary contains a brief description of the field exploration (borings and geophysical surreys), laboratory testing, and preliminary geotechnical recommendations for the site and access roadway. Figure E-1 shows the locations of the IFT sites. The IFT sites are shown on Figure E-2 through Figure E-17.

AJO-0446 - PRELIMINARY GEOTECHNICAL SUMMARY

CUSTOM AND BORDER PROTECTION TOWERS - TOHONO O’ODHAM NATION LANDS, ARIZONA

SITE DEVELOPMENT

Tower Site Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot-by-50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad grading will require ~7-foot-deep cut with ~10-foot-high 2:1 (H:V) permanent cut slopes (Fig. AJO-446-1).

Access Road Assumptions:

East of Indian Route 21, the access road (including the loop) is ~5.4 miles in length (Fig. AJO-446-2) and crosses ~22 washes of which ~4 washes may need a low water crossing (USACE, 2014).

Up to ~5 feet of fill will be placed to shallow the bedrock hill slope along the ~500 feet of access road east of the tower pad (Fig. AJO-446-1).

The road will be classified as FC-2/FC-3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur.

It is designated generally for 50-foot-wide improvement near the site with portions leading from the main access roads designated for 30-foot-wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Boring AJO-446 (depth=21.5 feet), including Downhole Optical Televiewer; Test Pit AJO-TP8 (depth=3.5 feet); Surface Mapping (Stations 1-8); Seismic Refraction Line (AJO-446); Electrical Resistivity-Wenner Array (AJO-446 W1- W5), see Figs. AJO-446-1&2.

Laboratory Testing: Dry Density (2 total); Moisture (2 total); UCS (2 total).

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

Tower Site AJO-0446 is underlain by Miocene age volcanic bedrock, which is primarily very strong, hard, and slightly weathered. The volcanic bedrock is locally overlain by up to ~3 feet of gravelly/cobbley/bouldery colluvium.

The access road to site AJO-446 is predominantly underlain by alluvial deposits. In the area of the bedrock hill near the Tower Site AJO-0446, the access road is underlain by shallow volcanic bedrock, which is mantled by a thin layer of rocky colluvium.

Groundwater: No groundwater was observed to the maximum depth explored (21.5 feet).

Seismic Velocity:

P-wave velocity of the colluvium is ~2,500 feet per second (ft/sec). The p-wave velocity of the underlying more weathered volcanic rock ranges between ~5,880 ft/sec to 6,900 ft/sec to a depth of between ~3 and 31 feet below ground surface.

Below this depth, the p-wave velocity of the less weathered volcanic rock ranges between ~8,330 ft/sec and 8,630 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using 5, 10, 15, and 20-foot Wenner array spacing were greater than 20,000 ohm-cm.

Rock Mass Discontinuities:

The predominant rock mass discontinuity observed during our field reconnaissance mapping and during the downhole televiewer survey within boring AJO-446 were joints. The observed joints are generally randomly oriented with a high concentration of near vertically oriented joints, see Appendix C.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

Based on the measured p-wave velocities, the more weathered volcanic rock is rippable to marginally rippable and the less weathered volcanic rock is non-rippable using a Caterpillar D8R with a multi or single shank No. 8 ripper or equivalent as published in “Caterpillar Performance Handbook (44 th Edition)” (2014). Based on the seismic velocity measurements, the proposed northwest pad cut may locally encounter less weathered volcanic rock which may require bigger excavation equipment (e.g. Caterpillar D10R) or blasting.

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

If desired, larger material excavated from the site could be crushed and reused as engineered fill. Crushed material should have largest dimension no greater than 1-inch if used as engineered fill, and should be thoroughly mixed with other native granular material. Alternatively, crushed import material could be used provided it meets gradation requirements for fill.

See Section 5.2 of the main report for general earthwork recommendations.

AJO-0446 - PRELIMINARY GEOTECHNICAL SUMMARY

Permanent Rock Slope

Stability:

Some measured joints dip out-of slope relative to the proposed rock slope cuts. However, due to the relatively shallow cuts and relatively high bedrock strength unconfined compression strength (UCS) ranges between approximately 8,500 to 10,500 psi), the potential risk of block or wedge failures is relatively minor.

Colluvial materials should be removed upslope of the permanent cuts as much as practical. If it is not practical to remove all the colluvial materials, cleanup of loose rock falls and slope sloughing may be required, especially after heavy precipitation.

See Section 5.2.4 of the main report for further discussion of permanent rock slope stability.

Corrosion Potential:

Electrical resistivity measurements indicate the on-site soil/rock may be classified as mildly corrosive to ferrous metals (resistivity >10,000 ohm-cm).

See Section 5.6 of the main report for further discussion of corrosion potential.

TOWER AND AUXILERY STRUCTURE FOUNDATION

Rock-Socketed Shafts:

Recommendations for the support of the tower structures by drilled shafts are provided below:

Axial Capacity – The compression and uplift nominal axial capacity of rock-socketed shafts varying in diameter from 6 to 18 inches may be estimated from Figure 7. These capacities are based on the understanding that the tower pad will be graded to remove weathered rock to a depth where competent material is encountered. The minimum required length of the shafts may be determined based on the allowable axial capacities given, however the shafts should be at least 15 feet long.

Settlement – Properly constructed and tested rock-socketed shafts should undergo minor settlements based on the anticipated design compressive axial load of 150 kips.

Lateral Capacity – Properly constructed and tested rock-socketed shafts should undergo minor lateral movements based on the anticipated design lateral load of 15 kips.

Observation of the installation of the rock-socketed shafts should be performed by a geotechnical engineer so that modifications can be made, if necessary, during installation.

The drillability of the volcanic bedrock was evaluated from drilling of Boring AJO-446 using a Mobile CME-850 truck-mounted rig. The uppermost 5 feet of colluvium and weathered volcanic bedrock was drilled with an 8-inch outside diameter hollow-stem auger. Below this depth, this hole was drilled with a 3-7/8-inch HQ diamond-impregnated core bit.

This rig was able to core through generally very strong volcanic bedrock at a rate ranging between ~25 and 60 feet per hour (ft/hr). Based on this information, the drilled shafts will likely require the use of rock drilling or coring methods, such as tricone bit equipment.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill. An allowable bearing capacity of 3,500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 400 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one-foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the understanding that the mat will rest on competent bedrock, settlements of the mat are anticipated to be minor.

ACCESS ROADWAYS:

FC-2/FC-3 -

Access

Roadway Design Criteria:

Based on our understanding of the proposed improvements, we anticipate that a graded gravel road will be built to replace the previously existing access trail.

Further details and recommendations for roadway design are included in Section 5.5 of the report.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site. We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and reduce excessive erosion.

Further details and recommendations for culvert design are included in Section 5.5.2 of the report.

AJO‐0448 ‐ PRELIMINARY GEOTECHNICAL SUMMARY

CUSTOM AND BORDER PROTECTION TOWERS ‐ TOHONO O’ODHAM NATION LANDS, ARIZONA

Assumptions:

180‐foot‐tall lattice tower supported by 3 drilled shafts within a 50‐foot‐by‐50‐foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad will require minimal grading (less than a few feet) and will be built up from the surrounding existing grade.

A drainage swale appears to empty near the northeast corner of the tower pad site.

Access Road Assumptions:

The access road begins at the end of Indian Route 21 (main access point for the Papago Forward Operating Base). The road continues west to the Border road and continues along the border to a turnoff that continues north to tower site (Fig. AJO‐ 448‐1). The road between Indian Route 21 to the border road turnoff is an all‐weather road that is well developed and should require only minimal maintenance. The portion of the road between Indian Route 21 and the Border road crosses ~6 washes of which ~2 washes may need a low water crossing. The border road portion crosses ~12 washes of which ~7 washes may need a low water crossing and one culvert needs replacing.

The road from the Border road turnoff north to the tower site is ~1.4 miles in length (Fig. AJO‐448‐1). This portion of the road will be upgraded by building up the road section. This portion of the access road crosses ~8 washes of which ~2 washes may require stabilization (e.g. articulated matting; USACE, 2014).

The road will be classified as FC‐2/FC‐3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur. A portion about 1 1/3 mile leading to the site from main access roads is designated generally for 50 foot wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Borings AJO‐448A (depth=71.5 feet) and AJO‐448B (depth=71 feet); Test Pit AJO‐TP9 (depth=10 feet);

Seismic Refraction Line (AJO‐448); Electrical Resistivity‐Wenner Array (AJO‐448 W1‐W5), (see Fig. AJO‐448‐1) .

Laboratory Testing: Dry Density (5); Moisture (5); Sieve Analysis (16); Atterberg Limits (5); Direct Shear (6); Compaction (2 total); Expansion Index (2); Consolidation (2); Corrosivity Tests (3).

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

Tower Site AJO‐0448 is underlain by fine‐grained Quaternary alluvium, which primarily consists of very stiff to hard lean clay to sandy lean clay (CL) and silt to sandy silt (ML). Bedrock was not encountered to the maximum depth explored (71.5 feet).

The access road from the Border road turnoff to the tower site is primarily underlain by fine‐grained alluvial soil, which appears to be compressible and low strength. At Test Pit AJO‐TP9 (see Fig. AJO‐448‐1), the alluvium consists of lean clay (CL), sandy silt (ML), clayey sand (SC), and silty sand (SM). Bedrock was not encountered to the maximum depth explored (10 feet).

Groundwater: No groundwater was observed to the maximum depth explored (71 feet).

Seismic Velocity:

P‐wave velocity of the uppermost ~2 feet of relatively loose, surficial alluvium is ~1,000 feet per second (ft/sec). The p‐wave velocity of the underlying alluvium ranges between ~1,330 ft/sec to 1,370 ft/sec to a depth of between ~12 and 18 feet below ground surface. Below this depth, the p‐wave velocity of the alluvium is ~2,580 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using 5‐, 10‐, 15‐, and 20‐foot Wenner array spacing were predominantly less than 1,000 ohm‐cm.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

See Section 5.2 of the main report for general earthwork recommendations.

The on‐site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

Fills should be placed in areas cleared and stripped of all debris, deleterious matter, organics and vegetation.

All fill materials should be compacted to at least 95% of the maximum dry density with moisture content within 2% of optimum.

Temporary excavations up to 4 feet deep can be cut vertically in stable material. Note that dry granular material will tend to slough and cave when cut vertically. Excavations greater than 4 feet deep can be made with slopes of 1½:1 (horizontal to vertical) to a maximum depth of 15 feet, where space is available.

AJO‐0448 ‐ PRELIMINARY GEOTECHNICAL SUMMARY

CUSTOM AND BORDER PROTECTION TOWERS ‐ TOHONO O’ODHAM NATION LANDS, ARIZONA

Corrosion Potential:

Electrical resistivity measurements indicate the on‐site soil is severely corrosive to ferrous metals (field and laboratory measured resistivity <1,000 ohm‐cm).

The chloride content of the on‐site soil indicates corrosive conditions (chloride concentrations >500 ppm).

The on‐site soil may be classified as having a positive sulfate attack potential (sulfate concentrations between 150 and 1,500 ppm).

See Section 5.6 of the main report for further discussion of corrosion potential.

TOWER AND AUXILERY STRUCTURE FOUNDATION

Drilled Shafts:

Axial Capacity – The compression and uplift nominal axial capacity of drilled shafts varying in diameter from 2 to 5 feet may be estimated from Figure 6. The minimum required length of the shafts may be determined based on the axial capacities given, however the shafts should be at least 20 feet long.

Settlement ‐ Settlements of the proposed tower leg foundations will depend on the length and diameter of the shafts selected. Based on the anticipated design compressive axial load of 150 kips, these settlements may be about ½ inch.

Differential settlement between similarly loaded shafts can be taken as ½ the total settlement.

Lateral Capacity – The lateral resistance of the drilled piers can be determined using load‐deflection (p‐y) analyses utilizing LPILE or similar software. The recommended soil input parameters for lateral capacity analyses are summarized in the table below and in the main text in Table 7 of the report.

IFT Site Location

IFT Site Predominant Lithologic Type

LPILE Soil Model Type

Total Unit Weight (pcf)

Effective Friction

Angle (deg)

Cohesion (psf)

E50 (‐)

AJO‐448 Fine‐Grained Alluvium Reese Clay w/o Free Water

105 0 1500 0.007

The drillability of the alluvium was evaluated from the drilling of Borings AJO‐448A and AJO‐448B. These borings were advanced using a Mobile CME‐850 truck‐mounted rig and 8‐in outside diameter hollow stem auger to the total depth with no major difficulties. Based on this information, the drilled shafts can likely be drilled using conventional drilling equipment, such as a flight auger. Depending on the type of drilling equipment some caving and raveling may occur within the drill shaft. Precautions should be taken during drilling and shaft installation to reduce caving and raveling.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill. An allowable bearing capacity of 1500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 200 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one‐foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the anticipated potential size of the proposed mats (generally less than about 500 ft2 area), settlements are estimated to be in the range of ½‐inch to 1‐inch at the center of the mat.

ACCESS ROADWAYS:

FC‐2/FC‐3 ‐

Access

Roadway Design Criteria:

Based on our understanding of the proposed improvements, we anticipate that a graded gravel road will be built to replace the previously existing access trail.

Further details and recommendations for roadway design are included in Section 5.5 of the main report.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the main report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site. We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and reduce

Further details and recommendations for culvert design are included in Section 5.5.2 of the main report.

AJO-0450 - PRELIMINARY GEOTECHNICAL SUMMARY

Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot by 50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad grading will require an up to ~5feetdeep cut and placement of up to ~4feetof engineered fill. Permanent cut and fill slopes will be a maximum of 2:1 (H:V) and 3:1, respectively (Fig. AJO-450-1).

Access Road Assumptions:

The access road begins at the end of pavement of Federal Route 1 and is ~1.3 miles in length (Fig. AJO-450-2). The access road crosses ~9 washes of which ~3 washes may need a low water crossing (USACE, 2014).

An existing ~5-foot-high cut slope is present along the access road that climbs the bedrock hill west of the tower pad.

The road will be classified as FC-2/FC-3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur. A portion about 1 1/3 mile leading to the site from main access roads is designated generally for 30-foot-wide improvement with a small portion at the site designated for 70-foot-wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Boring AJO-450 (depth=21.5 ft), including Downhole Optical Televiewer; Test Pit AJO-TP7 (depth=3.5 ft);

Surface Mapping (Stations 1-12); Seismic Refraction Line (AJO-450); Electrical Resistivity-Wenner Array (AJO-450 W1-W5), (see Figs. AJO-450-1&2)

Laboratory Testing: Dry Density (5); Moisture (5); UCS (5)

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

Tower Site AJO-0550 is underlain by Miocene age volcanic bedrock, which is primarily weak to strong, hard, and highly to slightly weathered. The volcanic bedrock is locally overlain by up to ~3.5 ft of gravelly/cobbley/bouldery colluvium.

The approximate western half of the access road to site AJO-450 is predominantly underlain by alluvial deposits. The approximate eastern half, along the bedrock hill near the Tower Site AJO-0450, is underlain by shallow bedrock mantled by a thin layer of rocky colluvium.

Groundwater: No groundwater was observed to the maximum depth explored (21.5 feet).

Seismic Velocity:

P-wave velocity of the colluvium is ~2,000 feet per second (ft/sec). The p-wave velocity of the underlying more weathered volcanic rock ranges between ~4,590 ft/sec to 5,780 ft/sec to a depth of between ~5 and 54 ft below ground surface. Below this depth, the p-wave velocity of the less weathered volcanic rock is ~5,820 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using 5-, 10-, 15-, and 20-ft Wenner array spacing were greater than 20,000 ohm-cm.

Rock Mass Discontinuities:

The predominant rock mass discontinuity observed during our field reconnaissance mapping and during the downhole televiewer survey within boring AJO-450 were joints. The observed joints are predominantly high angle with a few randomly oriented joints, see Appendix C.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

Based on the measured p-wave velocities, it appears that the more-weathered and less-weathered volcanic rock is rippable using a Caterpillar D8R with a multi or single shank No. 8 ripper or equivalent as published in “Caterpillar Performance Handbook (44 th Edition)” (2014).

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

If desired, larger material excavated from the site could be crushed and reused as engineered fill. Crushed material should have largest dimension no greater than 1-inch if used as engineered fill, and should be thoroughly mixed with other native granular material. Alternatively, crushed import material could be used provided it meets gradation requirements for fill.

See Section 5.2 of the report for general earthwork recommendations.

Permanent Rock Slope

Stability:

Some measured joints dip out-of slope relative to the proposed rock slope cuts at the IFT Site AJO-0450 and along existing cuts along the access road. However, due to the relatively shallow cuts and relatively high bedrock strength (UCS ranges between 4,600 and 16,800 psi), the potential risk of block or wedge failures is relatively minor.

Colluvial materials should be removed upslope of the permanent cuts as much as practical. If it is not practical to remove all the colluvial materials, cleanup of loose rock falls and slope sloughing may be required, especially after heavy precipitation.

See Section 5.2.4 of the report for further discussion of permanent slope stability.

AJO-0450 - PRELIMINARY GEOTECHNICAL SUMMARY

Electrical resistivity measurements indicate the on-site soil/rock may be classified as mildly corrosive to ferrous metals (resistivity >10,000 ohm-cm).

See Section 5.6 of the report for further discussion of corrosion potential.

TOWER AND AUXILERY STRUCTURE FOUNDATION

Rock-Socketed Shafts:

Axial Capacity – The compression and uplift nominal axial capacity of rock-socketed shafts varying in diameter from 6 to 18 inches may be estimated from Figure 7. These capacities are based on the understanding that the tower pad will be graded to remove weathered rock to a depth where competent material is encountered. The minimum required length of the shafts may be determined based on the allowable axial capacities given, however the shafts should be at least 15 feet long.

Settlement – Properly constructed and tested rock-socketed shafts should undergo minor settlements based on the anticipated design compressive axial load of 150 kips.

Lateral Capacity – Properly constructed and tested rock-socketed shafts should undergo minor lateral movements based on the anticipated design lateral load of 15 kips.

Observation of the installation of the rock-socketed shafts should be performed by a geotechnical engineer so that modifications can be made, if necessary, during installation.

The drillability of the volcanic bedrock was evaluated from drilling of Boring AJO-450 using a Mobile CME-850 truck-mounted rig. The uppermost 3.5 feet of colluvium was drilled with an 8-inch outside diameter hollow-stem auger. Below this depth, this hole was drilled with a 3-7/8-inch HQ diamond-impregnated core bit. This rig was able to core through generally very strong volcanic bedrock at a rate ranging between ~38 and 100 ft/hr. Based on this information, the drilled shafts will likely require the use of rock drilling or coring methods, such as tricone bit equipment.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill. An allowable bearing capacity of 3,500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 400 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one-foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the understanding that the mat will rest on competent bedrock, settlements of the mat are anticipated to be minor.

ACCESS ROADWAYS:

FC-2/FC-3 -

Access

Roadway Design Criteria:

Based on our understanding of the proposed improvements, we anticipate that a graded gravel road will be built to replace the previously existing access trail.

Further details and recommendations for roadway design are included in Section 5.5 of the report.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site. We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and reduce

AJO-0452 - PRELIMINARY GEOTECHNICAL SUMMARY

Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot by 50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad will require minimal grading (less than a few feet).

A well defined drainage channel is located within ~300 feet of the tower pad site.

Access Road Assumptions:

The access road begins at Federal Route 1 and continues to the tower site (Fig. D-5). The access road is ~1.7 miles long and crosses ~11 washes of which ~5 washes may need a low water crossing (USACE, 2014).

The road will be classified as FC-2/FC-3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur. It is designated generally for 50-foot-wide improvement with a small portion near the site for 70-foot-wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Borings AJO-452A (depth=71.5 ft) and AJO-452B (depth=72.5 ft); Test Pits AJO-TP5 (depth=3 ft) and AJO-TP6 (depth=10 ft); Seismic Refraction Line (AJO-452); Electrical Resistivity-Wenner Array (AJO-452 W1-W5), (see Fig.

AJO-452-1)

Laboratory Testing: Dry Density (4); Moisture (4); Sieve Analysis (17); Atterberg Limits (2); Direct Shear (2); Compaction (2);

Expansion Index (1); Consolidation (2); Corrosivity Tests (3)

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

IFT Site AJO-0452 is underlain by coarse-grained Quaternary alluvium. Between the ground surface and a depth of ~10 ft, the alluvium primarily consists of loose to medium dense sandy silt (ML), silty sand (SM), and well-graded sand with silt (SW-SM). Below a depth of ~10 ft, the alluvium primarily consists of very dense sands (SC, SM, and SP) and gravels (GC, GM, GP, and GW) with lesser clays (CL) and silts (ML). Bedrock was not encountered to the maximum depth explored (72.5 ft).

The access road is primarily underlain by coarse-grained alluvial soil with some areas of shallow volcanic bedrock. Test Pit AJO-TP5 (see Fig. AJO-452-1), consisted of volcanic bedrock overlain by a 3-ft layer of silty sand (SM) with gravel, cobbles, and boulders. The alluvium observed in Test Pit AJO-TP6 (see Fig. AJO-452-1), primarily consisted of silty sand (SM) and silty sandy gravel/cobbles (GM) that was overlain by a 1.5-ft layer of sandy silt (ML).

Groundwater: No groundwater was observed to the maximum depth explored (72.5 feet).

Seismic Velocity:

P-wave velocity of the uppermost ~2 to 6 feetof relatively loose, surficial alluvium is ~1,100 feet per second (ft/sec). The p-wave velocity of the underlying alluvium ranges between ~2,370 ft/sec to 2,800 ft/sec to a depth of between ~12 and 26-foot-below ground surface. Below this depth, the p-wave velocity of the alluvium is ~4,490 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using 5, 10, 15, and 20-ft Wenner array spacing ranged between ~3,000 and

~17,000 ohm-cm.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

See Section 5.2 of the report for general earthwork recommendations.

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

Corrosion Potential:

Resistivity measurements indicate the on-site soil is moderately corrosive to mildly corrosive to ferrous metals. Laboratory measurements indicate moderately corrosive soils (minimum resistivity between 2,000 and 10,000 ohm-cm). The field measurements predominantly indicate moderately corrosive soils with one Wenner array (AJO-452 W5) indicating mildly corrosive soils (resistivity >10,000 ohm-cm).

The chloride content of the on-site soil indicates non corrosive conditions (chloride concentrations <500 ppm).

The sulfate attack potential may be considered negligible (sulfate concentrations <150 ppm).

See Section 5.6 of the report for further discussion of corrosion potential.

AJO-0452 - PRELIMINARY GEOTECHNICAL SUMMARY

TOWER AND AUXILERY STRUCTURE FOUNDATION

Recommendations for the support of the IFT structures by drilled shafts are provided below:

Axial Capacity – The compression and uplift nominal axial capacity of drilled shafts varying in diameter from 2 to 5 feet may be estimated from Figure 5. The minimum required length of the shafts may be determined based on the axial capacities given, however the shafts should be at least 20 feet long.

Settlement - Settlements of the proposed IFT leg foundations will depend on the length and diameter of the shafts selected. Based on the anticipated design compressive axial load of 150 kips, these settlements may be about ½ inch.

Differential settlement between similarly loaded shafts can be taken as ½ the total settlement.

Lateral Capacity – The lateral resistance of the drilled piers can be determined using load-deflection (p-y) analyses utilizing LPILE or similar software. The recommended soil input parameters for lateral capacity analyses are summarized in the table below and in the main text in Table 7 of the report.

IFT Site Predominant

Lithologic Type LPILE Soil Model Type

Total Unit Weight (pcf)

Friction Angle (degree)

Cohesion (psf)

E50 (-)

AJO-452

Coarse-Grained

Alluvium (AJO sites) Reese Sand 105 35 0 NA

Observation of the installation of the drilled shafts should be performed by a geotechnical engineer so that modifications can be made, if necessary, during installation.

The drillability of the alluvium was evaluated from the drilling of Borings AJO-452A and AJO-452B. These borings were advanced using a Mobile CME-850 truck-mounted rig and 8-in outside diameter hollow stem auger to the total depth with no major difficulties. Based on this information, the drilled shafts can likely be drilled using conventional drilling equipment, such as a flight auger. Depending on the type of drilling equipment some caving and raveling may occur within the drill shaft. Precautions should be taken during drilling and shaft installation to reduce caving and raveling.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill or on deep, dense natural soils. An allowable bearing capacity of 1500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 200 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one-foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the anticipated potential size of the proposed mats (generally less than about 500 ft2 area), settlements are estimated to be in the range of ½-inch to 1-inch at the center of the mat.

ACCESS ROADWAYS:

FC-2/FC-3 -

Access

Roadway Design Criteria:

Based on our understanding of the proposed improvements, we anticipate that a graded gravel road will be built to replace the previously existing access trail.

Further details and recommendations for roadway design are included in Section 5.5 of the report.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site.

We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and reduce excessive erosion.

AJO-0454 - PRELIMINARY GEOTECHNICAL SUMMARY

Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot by 50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad will require minimal grading (less than a few feet of cut/fill). Engineered fill material will be built up from the surrounding existing grade.

A well defined drainage channel is located within ~200feetof the tower pad site.

Access Road Assumptions:

The access road begins at Federal Route 1 and continues to the tower site (Fig. AJO-454-1). The access road is ~0.9 miles long and crosses ~6 washes of which ~5 washes may require stabilization (e.g. articulated matting (USACE, 2014).

The road will be classified as FC-2/FC-3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur. A portion of the road about ¾ of a mile long leading from the main access road is designated generally for 30-foot-wide improvement with a small portion near the site for 70-foot-wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Boring AJO-454 (depth=71.5 ft); Test Pit AJO-TP4 (depth=7 ft); Seismic Refraction Line (AJO-454);

Electrical Resistivity-Wenner Array (AJO-454 W1-W5), (see Fig. AJO-454-1).

Laboratory Testing: Dry Density (4); Moisture (4); Sieve Analysis (8); Atterberg Limits (3); Direct Shear (3); Compaction (1);

Expansion Index (1); Corrosivity Tests (3)

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

Tower Site AJO-0454 is primarily underlain by coarse-grained Quaternary alluvium from the ground surface to a depth of ~20 feet and fine-grained alluvium below a depth of ~20 feet to the bottom of the borehole (~71.5 ft). Between the ground surface to a depth of ~20 feet, the alluvium primarily consists of very dense, silty sand with gravel (SM). Below ~20 feet, the alluvium primarily consists of very stiff to hard, lean and fat clay with sand (CL and CH). Bedrock was not encountered to the maximum depth explored (71.5 feet).

The access road is primarily underlain by coarse-grained alluvial soil. Test Pit AJO-TP4 (see Fig. AJO-454-1), consisted of silty sand (SM) with gravel, cobbles, and boulders and met refusal on a caliche/hardpan layer at a depth of 7 feet below ground surface.

Groundwater: No groundwater was observed to the maximum depth drilled (71.5 feet).

Seismic Velocity:

P-wave velocity of the uppermost ~0 to 5 feet of relatively loose, surficial alluvium is ~1,200 feet per second ft/sec. The p-wave velocity of the underlying alluvium ranges between ~1,960 ft/sec to 2,660 ft/sec to a depth of between ~56 and 83 feet below ground surface. Below this depth, the p-wave velocity of the alluvium is ~3,140 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using a Wenner array were greater than 10,000 ohm-cm at the 5- and 10-foot spacings. The electrical resistivity dropped to as low as ~4,500 ohm-cm at the 15 and 20-foot spacings.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

See Section 5.2 of the report for general earthwork recommendations.

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

Corrosion Potential:

Resistivity measurements indicate the on-site soil is severely corrosive to mildly corrosive to ferrous metals. Laboratory measurements indicate soils that are severely corrosive (minimum resistivity <1,000 ohm-cm) to moderately corrosive (minimum resistivity between 2,000 and 10,000 ohm-cm). Field measurements indicate mildly corrosive soils (resistivity >10,000 ohm-cm) at 5 and 10-ft spacings and moderately corrosive soils (resistivity between 2,000 and 10,000 ohm-cm) at the 15 and 20-ft spacings.

The chloride content of the on-site soil indicates non corrosive conditions (chloride concentrations <500 ppm).

AJO-0454 - PRELIMINARY GEOTECHNICAL SUMMARY

Axial Capacity – The compression and uplift nominal axial capacity of drilled shafts varying in diameter from 2 to 5 feet may be estimated from Figure 5. The minimum required length of the shafts may be determined based on the axial capacities given, however the shafts should be at least 20 feet long.

Settlement - Settlements of the proposed tower leg foundations will depend on the length and diameter of the shafts selected. Based on the anticipated design compressive axial load of 150 kips, these settlements may be about ½ inch.

Differential settlement between similarly loaded shafts can be taken as ½ the total settlement.

Lateral Capacity – The lateral resistance of the drilled piers can be determined using load-deflection (p-y) analyses utilizing LPILE or similar software. The recommended soil input parameters for lateral capacity analyses are summarized in the table below and in the main text in Table 7 of the report.

IFT Site Location

IFT Site Predominant Lithologic Type

LPILE Soil Model Type

Total Unit Weight (pcf)

Effective Friction Angle

(degree)

Cohesion (psf)

E50 (-)

AJO-454

Coarse-Grained Alluvium (0-20-foot depth)

Fine-Grained Alluvium (>20-foot depth)

Observation of the installation of the drilled shafts should be performed by a geotechnical engineer so that modifications

The drillability of the alluvium was evaluated from the drilling of Boring AJO-454. This boring was advanced using a Mobile CME-850 truck-mounted rig and 8-in outside diameter hollow stem auger to the depth with no major difficulties. Based on this information, the drilled shafts can likely be drilled using conventional drilling equipment, such as a flight auger.

Depending on the type of drilling equipment some caving and raveling may occur within the drill shaft. Precautions should be taken during drilling and shaft installation to reduce caving and raveling.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill or on deep, dense natural soils. An allowable bearing capacity of 1500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 200 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one-foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the anticipated potential size of the proposed mats (generally less than about 500 ft2 area), settlements are estimated to be in the range of ½-inch to 1-inch at the center of the mat.

ACCESS ROADWAYS:

FC-2/FC-3 -

Access

Roadway Design Criteria:

Based on our understanding of the proposed improvements, we anticipate that a graded gravel road will be built to replace the previously existing access trail.

Further details and recommendations for roadway design are included in Section 5.5 of the report.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site. We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and reduce

AJO-0458 - PRELIMINARY GEOTECHNICAL SUMMARY

Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot by 50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The IFT pad will require minimal grading (less than a few feet) and will be built up from the surrounding existing grade.

A well defined drainage channel is located within ~300 feet of the tower pad site.

Access Road Assumptions:

No access road improvements. Site is adjacent to Indian Route 5 (Fig. AJO-458-1).

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Boring AJO-458 (depth=70 feet); Seismic Refraction Line (AJO-458); Electrical Resistivity-Wenner Array (AJO-458 W1-W5), (see Fig. AJO-458-1).

Laboratory Testing: Dry Density (1); Moisture (1); Sieve Analysis (7); Direct Shear (1); Compaction (1); Corrosivity Tests (3)

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

Tower Site AJO-0458 is primarily underlain by coarse-grained Quaternary alluvium. The alluvium primarily consists of very dense, silty sand (SM) with varying amounts of gravel and cobbles. Bedrock was not encountered to the maximum depth explored (70 ft).

Groundwater: No groundwater was observed to the maximum depth explored (70 feet).

Seismic Velocity:

P-wave velocity of the uppermost ~3 to 4 feet of relatively loose, surficial alluvium is ~1,250 feet pre second (ft/sec). The p-wave velocity of the underlying alluvium ranges between ~3,340 ft/sec to 3,500 ft/sec to a depth of between ~20 and 29 feetbelow ground surface. Below this depth, the p-wave velocity of the alluvium is ~5,310 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using 5-, 10-, 15-, and 20-ft Wenner array spacing were greater than 10,000 ohm-cm.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

See Section 5.2 of the report for general earthwork recommendations.

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

Corrosion Potential:

Electrical resistivity measurements indicate the on-site soil is moderately corrosive to mildly corrosive to ferrous metals.

Laboratory measurements indicate soils that are moderately corrosive (resistivity between 2,000 and 10,000 ohm-cm).

Field measurements indicate mildly corrosive soils (resistivity >10,000 ohm-cm).

The chloride content of the on-site soil indicates non corrosive conditions (chloride concentrations <500 ppm).

AJO-0458 - PRELIMINARY GEOTECHNICAL SUMMARY

Axial Capacity – The compression and uplift nominal axial capacity of drilled shafts varying in diameter from 2 to 5 feet may be estimated from Figure 5. The minimum required length of the shafts should be at least 20 feet.

Settlement - Settlements of the proposed tower leg foundations will depend on the length and diameter of the shafts selected. Based on the anticipated design compressive axial load of 150 kips, these settlements may be about ½ inch.

Differential settlement between similarly loaded shafts can be taken as ½ the settlement.

Lateral Capacity – The lateral resistance of the drilled piers can be determined using load-deflection (p-y) analyses utilizing LPILE or similar software. The recommended soil input parameters for lateral capacity analyses are summarized in the table below and in Table 7 of the report.

IFT Site Predominant Lithologic Type

LPILE Soil Model Type

Total Unit Weight (pcf)

Effective Friction Angle

(deg)

Cohesion (psf)

E50 (-)

AJO-458

Coarse-Grained Alluvium

(AJO sites)

Observation of the installation of the drilled shafts should be performed by a geotechnical engineer so that modifications

The drillability of the alluvium was evaluated from the drilling of Boring AJO-458. This boring was advanced using a Mobile CME-850 truck-mounted rig and 8-in outside diameter hollow stem auger to the depth with no major difficulties. Based on this information, the drilled shafts can likely be drilled using conventional drilling equipment, such as a flight auger.

Depending on the type of drilling equipment some caving and raveling may occur within the drill shaft. Precautions should be taken during drilling and shaft installation to reduce caving and raveling.

Mat Type Foundation:

Ancillary support structures can be founded on mat slabs resting on a minimum of 2 feet of engineered fill or on deep, dense natural soils. An allowable bearing capacity of 1500 psf can be used for design of these mats.

A vertical unit modulus of subgrade reaction, K, of 200 pounds per cubic inch (pci) may be used in the design of the mat foundations. This value is a unit value for use with a one-foot square area and should be reduced in accordance with the discussion in Section 5.4

Based on the anticipated potential size of the proposed mats (generally less than about 500 ft2 area), settlements are estimated to be in the range of ½-inch to 1-inch at the center of the mat.

ACCESS ROADWAYS:

FC-2/FC-3 -

Access

Roadway Design Criteria:

No access road improvements are required at this site.

Surface Drainage

Further details and recommendations for surface drainage are included in Section 5.5.1 of the report.

Culvert Design: Various small drainage channels, gullies, swales, and washes cross the existing access road and trails leading to the site.

We understand that culverts (steel or concrete) may be installed in some locations to improve existing drainages and

AJO-0460 - PRELIMINARY GEOTECHNICAL SUMMARY

Assumptions:

180-foot-tall lattice tower supported by 3 drilled shafts within a 50-foot by 50-foot pad.

Maximum Uplift = 135 kips/leg; Maximum Compression = 150 kips/leg; and Maximum Shear = 15 kips/leg.

The tower pad will require minimal grading (less than a few feet) and will be built up from the surrounding existing grade..

Access Road Assumptions:

The access road begins at Indian Route 5 and continues to the tower site (Fig. AJO-460-1). The access road is ~2.8 miles long and crosses ~46 washes of which ~12 washes may require stabilization (e.g. articulated matting (USACE, 2014).

The road will be classified as FC-2/FC-3 and will be a crowned, graded earth road with storm water drainage ditches on both sides. Note that this classification assumes ongoing maintenance will be required and some erosion and damage may occur. It is designated generally for 50-foot-wide improvement with a portion approximately 1/3 mile long near the site for 70-foot-wide improvement.

SUBSURFACE CONDITIONS

Field Investigations and Laboratory Testing:

Field Investigation: Borings AJO-460A (depth=71.5 feet) and AJO-460B (depth=71.5 feet); Test Pits AJO-TP1 (depth=3 fee) and AJO-TP2 (depth=2.5 feet); Seismic Refraction Line (AJO-460); Electrical Resistivity-Wenner Array (AJO-460 W1-W5), (see Fig. AJO-460-1)

Laboratory Testing: Dry Density (13); Moisture (13); Sieve Analysis (17); Atterberg Limits (4); Direct Shear (6); Compaction (2); Expansion Index (2); Consolidation (2); Corrosivity Tests (3)

See Appendix A for field investigation results. See Appendix B for laboratory test results.

Geologic Materials:

IFT Site AJO-0460 is underlain by coarse-grained Quaternary alluvium. The alluvium primarily consists of very dense (with occassional medium dense to dense), clayey sand (SC) to silty sand (SM) with varying degrees of gravel. Bedrock was not encountered to the maximum depth explored (71.5 feet).

The access road is primarily underlain by granitic bedrock and coarse-grained alluvial soil. Test Pit AJO-TP1 (see Fig. AJO- 460-1), consisted of granitic bedrock from the ground surface to the refusal depth of 2.5 feet. Test Pit AJO-TP2 (see Fig.

AJO-460-1), consisted of granitic bedrock overlain by a 2.5-foot layer of silty sand (SM) with gravel and cobbles.

Groundwater: No groundwater was observed to the maximum depth explored (71.5 feet).

Seismic Velocity:

P-wave velocity of the uppermost ~5 feet of relatively loose, surficial alluvium is ~1,150 feet per second (ft/sec). The p-wave velocity of the underlying alluvium ranges between ~2,410 ft/sec to 3,000 ft/sec to a depth of between ~28 and 57 feet below ground surface. Below this depth, the p-wave velocity of the alluvium is ~4,070 ft/sec.

Resistivity:

Apparent electrical resistivity values measured using a Wenner array were greater than 10,000 ohm-cm at the 5-foot spacing. The electrical resistivity dropped to as low as ~6,800 ohm-cm at the 10-, 15-, and 20-foot spacings.

PRELIMINARY GEOTECHNICAL RECOMMENDATIONS

Earthwork:

See Section 5.2 of the report for general earthwork recommendations.

The on-site excavated granular materials such as sands and silty sands can be used as engineered fill. Oversized material (greater than 6 inches in largest dimension) should be removed from excavated material prior to reuse as engineered fill.

Corrosion Potential:

Resistivity measurements indicate the on-site soil is severely corrosive to mildly corrosive. Laboratory measurements indicate soils that are severely corrosive (minimum resistivity <1,000 ohm-cm).