Memo_NV FLAP 400(1) Logandale Trails Access Road_FINAL.pdf

Technical Memorandum

Date: August 24, 2021

To: Emilio Burgos, Project Manager, CFLHD, Lakewood CO

From: Devin T. Dixon, Geotechnical Engineer, CFLHD, Lakewood CO & Ian Johnson, Geotechnical Engineer Trainee, CFLHD, Lakewood CO

Through: Marilyn D. Dodson, Lead Geotechnical Engineer CFLHD, Lakewood CO

Subject: Evaluations and Recommendations for the Logandale Trails Access Road, Logandale Trails System, Clark County, Nevada, NV FLAP 400(1)

1 PROJECT BACKGROUND INFORMATION

This geotechnical memorandum presents the field evaluation results and recommendations for the reconstruction work to be performed on Logandale Trails Access Road. The project is located in Clark County, Nevada and provides visitor access to the Logandale Trails System (LTS) recreation area and the Valley of Fire State Park. This region resides within the Moapa Valley which includes the Muddy River, a tributary of the Colorado River system, that empties into Lake Mead. A project location map is provided in Figure 1.

The general scope of the project includes roadway reconstruction for approximately 3.38 miles beginning in west Logandale and terminating at the Valley of Fire parking lot along Logandale Trails Access Road. The road provides visitors access to an ATV rental facility, a camping and picnic area, bathrooms, and the LTS at the Valley of Fire parking lot. The existing roadway is classified as a rural local road and consists of a gravel 24- to 30-foot wide traveled way. The existing clear zone is minimal, with multiple locations of steep drop-offs and an existing creek near the edge of road. The roadway profile has some steep grades (greater than 8%) and steep slopes adjacent to the road which cause safety hazards by limiting vehicle sight distance on both vertical and horizontal curves. Figure 2 shows the typical existing roadway conditions.

Figure 1:- Project location map.

Figure 2:- Typical roadway conditions.

The entire route will receive new pavement, signing and striping, minor grading, widening, and drainage improvements including low water crossings and barrier with revet mattress where needed to reinforce the roadway shoulder. The geotechnical design elements to be considered for this project include cut slope recommendations, subgrade soil support for both the structural section and proposed drainage improvements, and proper roadway ditch width guidelines.

Guardrail has been proposed to be installed in one section on the fill-slope side between STA 74+00 and STA 79+00 and fill-slopes will be graded to accommodate the proposed clear zone and improve vehicle sight distance. Another improvement includes railroad crossing panels. The typical section for the majority of the project includes a 22-foot traveled way with a 7-foot clear zone consisting of a 2-foot paved shoulder and a 1V:4H graded foreslope. Both graded ditches and paved ditches with full depth concrete curb are proposed for the project. The loop at the end of the project is one way in each direction, with an 11-foot traveled way with 2-foot shoulders.

Refer to the Final Pavement and Materials Report dated October 2020 and the typical sections shown in the plan sheets for the structural section details of the roadway.

2 GEOLOGY AND SEISMICITY

2.1 Regional Geology

The project is located east of Weiser Ridge in the Northern Muddy Mountains and lies northeast of the Valley of Fire State Park. A combination of two published maps outlining the regional geology in the project area is shown in Figure 3 (Bohannon, 1992 & House, 2010). The various geologic units mapped within or in close vicinity to the project are listed in Table 1. The project starts in west Logandale then travels north and curves west over Siltstone Facies of the Muddy Creek Formation (Tms) composed of non-marine, fluvial deposited materials including siltstone, sandstone, claystone, gypsiferous siltstone, and gypsum. Heading west, the route transitions through isolated sheet-like Terrace Deposits (Qt) composed of silt, sand, pebbles, cobbles, and boulders. As the road bends south, the underlying geologic unit transitions to the Overton Conglomerate Member of the Baseline Sandstone (Kbo). This unit is described as a sandy matrix conglomerate with discontinuous, irregular bedding. The conglomerate also contains a variety of clasts including resistant, Devonian-aged Muddy Peak Limestone. Before reaching the Logandale Trails Access Road Loop, the underlying unit transitions to the Aztec Sandstone (Jha), a quartz arenite. This unit is described as moderately indurated and resistant and contains sand that is very well sorted, fine grained, and well rounded (Bohannon, 1992).

Additional information regarding rock identification and properties can be found in the rock descriptions provided in Attachment 2.

Figure 3:- Combined Regional Geologic Map (Bohannon, 1992) & (House, 2010)

Scs

Afx

Table 1:- Mapped Geologic Units in the Project Vicinity (Bohannon, 1992) & (House, 2010)

MAP

SYMBOL NAME AND DESCRIPTION

Qoa

OLDER ALLUVIUM (PLEISTOCENE) – Silt, sand, pebbles, cobbles, and boulders on alluvial fans and along bottoms of moderately wide to wide stream valleys except in the most active channel bottoms, which are filled by Pleistocene and Holocene younger alluvium (Qya). Consists of poorly sorted, angular to sub-rounded, unconsolidated constituents as large as several meters in diameter: local derivation. Older alluvium deposits are generally located 1 m or more above Pleistocene and Holocene younger alluvium (Qya). Incipient soil zones and vegetation common. Holocene and Pleistocene and Holocene younger alluvium (Qya) is included in older alluvium where outcrops are too small to show at map scale. Thickness generally less than 2 m.

Qt

TERRACE DEPOSITS (PLEISTOCENE) – Silt, sand, pebbles, cobbles, and boulders in sheet-like deposits isolated from one another and from other surficial deposited by erosion. Commonly have well-developed flat upper surfaces.

Poorly sorted to moderately sorted, sub-rounded constituents as large as several meters in diameter; unconsolidated;

locally derived. Soil zones and desert varnish incipiently to well developed on flat upper surfaces; vegetation common. Thickness 0-5 m.

Tms

SILTSTONE FACIES – Siltstone, sandstone, claystone, gypsiferous siltstone, and gypsum; pale pink and light brown; non-marine. Bedding is parallel, even, and continuous and varies between 1 cm and 0.5 m in thickness regionally but is moderately uniform in thickness locally. Sandstone and siltstone have clay- and carbonate-rich matrices and moderately sorted grains (0.1 to 0.2 mm in diameter) of quartz, feldspar, calcite, muscovite, biotite, chert, and claystone lithic fragments in a grain-supported fabric. East of Overton Ridge, claystone and siltstone predominate over all other rock types, but in most other exposures gypsum and gypsiferous siltstone compose a large part of unit. More than 900 m thick.

Thrl

LIMESTONE FACIES – Limestone; pale brown to brownish white; resistant, forms hogbacks. Bedding is parallel, continuous, and wavy; ranges between 10 and 50 cm thick. Laterally continuous with magnesite and dolomite facies described in Rainbow Gardens Member by Bohannon (1984) about 2-3 km east of southeast corner of quadrangle, just east of Overton Ridge. More than 100 m thick.

Kbo

OVERTON CONGLOMERATE MEMBER (UPPER CRETACEOUS) – Conglomerate; grayish brown;

moderately resistant; non-marine. Poorly sorted to moderately sorted; clast-supported, sandy matrix conglomerate.

Most Clasts are 1cm in diameter. Several exotic blocks (Kboc), composed of Muddy Peak Limestone (correlative of Sultan Limestone) of Devonian age, occur as clasts within the conglomerate and are large enough to be mapped separately. Smaller clasts chiefly consist of carbonate rocks derived from the upper Paleozoic section and sandstone from the Mesozoic section; clasts of petrified wood derived from the Chinle Formation are common.

Bedding is discontinuous, irregular, and nonparallel except at an outcrop scale where bedding is roughly parallel.

More than 400 m thick.

Jha

AZTEC SANDSTONE (JURASSIC AND TRIASSIC) – Quartz arenite; red and less commonly pale yellow to white; eolian; non-marine; cemented in most places with hematite. Discontinuous, nonparallel, even bedding that has large-scale (as thick as 10m) planar cross-stratification. Moderately indurated and resistant. Sand grains are very well sorted, fine grained, well rounded, and composed entirely of frosted quartz. Lithologically identical to and correlative with the Navajo Sand-stone in southern Utah and northern Arizona. Mostly allochthonous above the Summit-willow Tank thrust fault; pattern overprint used where unit is autochthonous with respect to all thrusts.

More than 1000 m thick.

Afx Extremely old alluvial fan deposits (Pleistocene to late Miocene).

Avy Young alluvial Valley Deposits (Holocene).

Scs Interbedded carbonates and siliciclastic sedimentary rocks.

2.2 Regional Seismicity

The state of Nevada has more mapped Quaternary faults, meaning faults that have moved in the past ~1.6 million years, than any other state and about 1,500 of these faults are considered to be active. The entirety of the state resides between the Sierra Nevada to the west and Colorado Plateau to the east in a physiographic region referred to as the Basin and Range Province (Nevada Bureau of Mines and Geology, 2010). The California Wash fault is the nearest seismic hazard fault to the project site, as it forms the boundary between the California Wash to the west and the Muddy Mountains to the east. This fault strikes in the northeast in its southern section and then curves to a north strike in its northern section (Anderson, 1999). The Frenchman Mountain fault zone is another seismic hazard fault that poses significant danger to the Las Vegas region. This fault strikes north, dips mostly west, and forms the structural boundary between the basin beneath parts of the Las Vegas Valley and the Frenchman and Sunrise Mountain ranges to the east. In addition to the two aforementioned faults, several other known Quaternary faults are mapped within approximately 40 miles of the project area and are summarized in Table 2 below (U.S. Geological Survey, 2017).

Table 2:- Summary of Nearby Quaternary Faults

FAULT OR FAULT ZONE

DISTANCE FROM

CENTER OF PROJECT

FAULT PARALLEL

SLIP RATE

FAULT

LENGTH AGE

(miles) (inch/year) (miles) (years)

California Wash Fault 7.2 0.00787 - 0.0394 19.9 <15,000

Overton Arm Faults 14.4 >0.00787 40.4 <130,000

Wildcat Wash Fault 24.6 >0.00787 13.1 <750,000

Littlefield Mesa Faults 30.9 >0.00787 13.1 <750,000

Sheep Range Fault 31.9 >0.00787 28.6 <130,000

Frenchman Mountain Fault 34.9 >0.00787 11.2 <130,000

Wheeler Fault Zone and Graben 37.2 >0.00787 28.0 <750,000

2.3 Geologic Hazards

The Logandale Trails Access Road is constructed in a desert canyon-type environment on a sequence of sedimentary units including limestone, siltstone, sandstone, and claystone. Gypsum and gypsiferous deposits, which appeared to be evidenced during the 30 percent site visit as surficial white powder in certain areas along the route, can be subject to solution weathering and contribute to sulfates in the site soils. Southern Nevada is also prone to high salt concentrations in certain areas that can contribute to salt heave. This process and its effect on surrounding soils is discussed further in Section IV of the Final Pavement and Materials Report.

Other potential geologic hazards include the following: earthquakes (as discussed in the previous section), abandoned mines and contamination, debris flow & flooding, landslides, liquefaction, hydrocollapsible soils, compressive soils, cemented soils (such as caliche), subsidence, shallow groundwater, and potentially expansive clays below the surface (Bowman, 2016).

Flooding, however, has been an increasing concern in recent years. In early September 2014, about 5-inches of rain, roughly the average annual rainfall for the area, fell over the Moapa Valley area in approximately 2 hours. This event, a one-in-a thousand-year flood, caused water to overflow the Muddy River washing out parts of the I-15 highway, damaging homes, and forcing evacuations of residents (Zeitlow, 2015). The dry, desert soils of the region contribute to flooding and debris flows as they are not able to effectively absorb the excess water. Hazards related to flash floods and debris flows may be mitigated by locating the roadway above the anticipated flood levels. Additional information regarding the local climate can be found in Section II of the Final Pavement and Materials Report.

Naturally occurring asbestos (NOA) has been found in the rocks and dust in Clark County outside of Las Vegas (Sever, 2019). Asbestos was not encountered during the 30 percent site visit, however a contingency plan for managing NOA encountered during construction should be considered.

CFLHD does not take responsibility for development, implementation, or enforcement of any sort of management or abatement plan for NOA.

Erodibility of soil should be considered in the size and layout of surface drainage features.

Differential erosion of the weathered sedimentary units, which is highly variable at the project site, can contribute to the falling hazard along the project alignment and can be temporarily mitigated by scaling of loose and unstable materials from slopes adjacent to the roadway. Soil erosion can be addressed, to an extent, by ensuring the roadside ditches have appropriate width and properly installed check dams to control water velocity and erosive capacity.

3 FIELD EVALUATION

A subsurface investigation targeting the proposed improvements was not performed for this scope of work. A pavement and subgrade investigation was conducted on October 24, 2018 and is discussed in Section III of the Final Pavement and Materials Report. Observations of surficial conditions and reconnaissance mapping was performed in conjunction with the 30 percent design review field visit on March 2, 2020. The CFLHD team that participated in this visit included Emilio Burgos (Project Manager), Ryan Mathis (Roadway Designer), Luis Calderon (Hydraulics Engineer), Devin Dixon (Geotechnical Engineer), and Ian Johnson (Geotechnical Engineer Trainee). The CFLHD team also met with representatives of Clark County and Nevada State Parks.

The geotechnical features that were examined during this visit included existing cut slopes and subgrade soil support for drainage improvements. Evaluations and recommendations presented in this memorandum are based on visual observations and limited measurements taken during the site visit. Drainage improvements will be discussed to a certain degree in this memorandum as they relate to geotechnical concerns. Further discussions are addressed in the Final Hydraulic Report.

At least three or four “formal” low water crossings, meaning concrete pavement with barrier/cutoff walls, are intended at critical drainage locations, and 24-inch pipe culverts are proposed at other locations throughout the project. At least seven “informal” low water crossings, meaning possible erosion protection and likely no significant structural work, have also been proposed according to design recommendations.

3.1 General Observations

The surficial material on site is interpreted to be alluvial material and is classified as sand and silt with varying amounts of gravel, according to soil identification and description guidelines provided in Attachment 1. When handled, the material felt loose and non-plastic, and thus fell apart easily. The material making up the roadside slopes could be sluffed off by hand and showed obvious signs of sediment transport due to storm water erosion, characterizing it as highly erodible material.

The existing Logandale Trails Access Road appears to have been constructed using cut and fill methods on native soil. Native slopes in the area are sparsely vegetated with scant brush, bushes, and typical desert-type vegetation. Areas of exposed weathered bedrock along the roadway are limited but can be distinguished below the roadway near the creek elevation. The degree of weathering of the rock is likely highly and completely weathered according to descriptions provided in Section 4 of the Central Federal Lands Rock Core Description Field Reference provided in Attachment 2. Bedrock and highly eroded rock formations are more prevalent near the west end of the project near the Valley of Fire State Park.

Raveling was noted in the existing cut slopes, but, generally, appeared to be limited to a maintenance level issue. This raveling does not appear to impact the traveled way. The existing roadway surface, cuts, and fills appeared to be in mostly good condition. However, four areas of concern were noted during the site visit and are summarized in the following sections.

3.2 Site #1, STA 39+00+00 – 41+00 RT/LT

The existing cut slope at approximate STA 40+00 LT extends roughly 10 feet above the roadway at a slope ratio of about 1V:1.5H in alluvial soil. Above the cut slope, the native slope extends an additional 20 feet at a slope ratio of about 1V:2H. The lower, steeper segment of the existing cut-slope shows signs of storm water erosion through rilling. The upper, flatter segment of the slope maintains vegetation growth and displays fewer signs of storm water erosion and rilling, as shown in Figure 4. In addition, an existing ATV trail runs parallel to the roadway and climbs to the top of the existing fill slope at about STA 40+00 LT, as shown below in Figure 5. A steep cut-slope adjacent to the roadway on the right side can also be seen in Figure 5.

Figure 4:- Existing cut-slope in alluvial soils at Site 1, facing west.

Figure 5:- Existing cut-slopes in alluvial soils at Site 1, facing north.

3.3 Site #2, STA 55+00 – 58+00 RT/LT

The existing cut slope at approximately STA 55+00 LT – 58+00 LT is located on the inside of a curve and extends roughly 7 feet above the roadway at a slope angle of approximately 1V:1.75H in alluvial soil. Above the cut slope, the native soil extends about 10 feet and flattens out to a roughly 1V:4H slope ratio as shown in Figure 6.

On the right side of the roadway there is an existing cut-slope showing signs of storm water erosion including rilling as shown in Figure 7 below.

Soil and rock conditions are similar those observed at Site 1.

Figure 6:- Existing cut-slope in alluvial soil at Site 2, facing north.

Figure 7:- Existing cut-slope Site 2 in alluvial soil, facing east, and eroded rundown in foreground.

3.4 Site #3, STA 64+00 RT – 69+00 RT

A steep slope adjacent to the roadway begins after the driveway near STA 64+22 RT and continues until approximately 69+00 RT. The aforementioned driveway provides access to ATV rentals and is frequently used by visitors for recreation. The existing native slope was measured to be approximately 65-feet high with varying grade of about 1.5V:1H to near vertical near the crest in alluvial soil and weathered siltstone/sandstone material. The slope shows evident signs of storm water erosion and sediment transport due to rilling as shown in Figure 8.

Figure 8:- Existing slope in weathered sedimentary rock (siltstone) at Site 3, facing north.

3.5 Site #4, STA 73+00 RT – 76+00 RT

Another steep slope adjacent to the roadway exists at this location. The existing cut slope is about 10-feet high with a slope ratio of approximately 1V:1H in a mixture of alluvial soils and weathered sedimentary units. The adjoining native slope then moderately flattens for roughly 15 feet. Figure 9 shows a view of this slope looking down-station. There is an ATV trail that climbs to the top of this slope which can also be seen in Figure 9.

Figure 9:- Existing cut-slope in weathered sedimentary rock (siltstone) at Site 4.

(Looking down-station)

3.6 Shrink/Swell Recommendations

It is estimated that the onsite alluvial soils within the project area will have a 5-10% shrink percentage, corresponding to a shrink/swell factor of 0.95-0.90. Intact sandstone and siltstone have a swell percentage of 34% and a shrink percentage of 11%, respectively. Decomposed or weathered rock, which is abundant throughout the project, has a swell percentage of up to 12% and a shrink percentage of 9%, depending on the ratio of rock to earth material present within the weathered units. The recommended shrink/swell factors are based on a combination of standard tabled values for common materials in the FLH Technical Guidance Manual and experience with other CFLHD projects in similar materials (2007).

4 RECOMMENDATIONS

4.1 Subgrade Soil Support Recommendations

A soil unit weight (γ) of 125 pounds per cubic foot, internal friction angle (φ) of 30, and cohesion intercept (c) of 0 are the estimated design values for the subgrade soil. These properties were estimated based on typical design values shown in the NAVFAC Design Manual 7.01 assuming silty sand material. This material is expected to be underlain by a sequence of weathered sedimentary rocks including siltstone, sandstone, claystone, conglomerate, and limestone. Based on this knowledge of the geologic conditions near the structure site, the presumptive bearing resistance for the assumed soil type can be estimated to be between 4,000-8,000 psf with a recommended value of use of 5,000 psf according to Table C10.6.2.6.1-1 of AASHTO LRFD Bridge Design Specifications, 7th Edition, 2014. The bearing resistance values presented in this table are based on a maximum settlement of one inch and only apply at the service limit state (resistance factor of 1.0). For strength limit state, a resistance factor of 0.45 should be applied. It is recommended that the base of the proposed drainage structures, the “formal” low water crossings and pipe culverts, be constructed below the depth of frost potential, which is estimated at approximately 23 inches according to the state average frost depth and local practices (Hammerpedia, 2020).

4.2 Cut Slope Recommendations

In general, non-saturated coarse-grained granular soil slopes can be constructed at a safe slope ratio of 1V:1.5H or flatter; non-saturated slopes composed of fine-grained, cohesive soils can be constructed at a safe slope ratio of 1V:2H; weathered bedrock slopes can be constructed at a slope ratio of 1V:1H or flatter depending on fracturing and degree of weathering; and combination soil and rock slopes can be cut at 1V:1.5H. Based on the observed conditions of the sites discussed in the previous section, a slope ratio of 1V:2H should be used for cut slopes on the project. Areas of observed springs and seeps encountered during construction may require flattening or additional support and should be evaluated by the CFLHD geotechnical engineer on a case by case basis. Steeper slopes decrease the likelihood of re-vegetation and increase the likelihood and frequency of slumping and raveling; flatter slopes should be utilized where possible.

4.3 Fill Slope Recommendations

The designer has indicated fill slope sections along the route. The highest proposed fill slope is roughly 16-feet high and extends approximately 100-feet long. At least three or four other locations have proposed fill slopes between 10- and 12-feet high. The remaining fill slopes on the project are generally 8-feet or less. It is worth noting that sliver fills should be avoided to prevent differential settlement which could lead to continued raveling and destabilization. The fill slopes included in the project should be constructed at a maximum slope ratio of 1V:2H.

However, a 1V:1.5H slope ratio may be used for select fill slopes as determined by the CFL designer and geotechnical engineer.

4.4 Slope Reconditioning

Slope reconditioning is recommended to establish safe slopes for construction and to preserve the condition of the corridor. Significant cuts are not expected, although mitigation measures are still advisable. Standard earthwork equipment, such as an excavator, is anticipated to be used to round and shape hazardous slopes.

4.5 Rock Rippability

Based on the surface geologic mapping, the rock encountered, primarily weathered sandstone and siltstone, is expected to be rippable through the project area; however, final determination of rock rippability is the responsibility of the contractor. Shear wave velocity of the geologic layers was not evaluated by geophysical methods. However, based on Table A.1 in Attachment 3, the rock encountered can be presumed to be between the soft and hard rock descriptions. Additional information regarding the excavation characteristics of rock and rippability charts can be found in Attachment 3.

4.6 Ditch Recommendations

The existing roadway has little to no ditch width. Therefore, it is recommended that both graded and paved ditches be constructed along the route to improve drainage, collect debris, and reduce impacts to the roadway. The ditches should be installed with 1V:4H slopes and a minimum 4-foot width for graded ditches and 3-foot minimum width for paved ditches. As stated in the 95 percent plans, the gradient and width of the roadway ditches and the excavation and embankment ratios may be adjusted by the CO to assure adequate drainage and stability. Typical section drawings shown in the 95 percent plan set, Sheets A5 through A7, provide further details.

5 DISCLAIMERS/LIMITATIONS CLAUSE

Subsurface exploration was not performed as a part of this scope of work. Interpretation of surface and subsurface conditions is based on limited field reconnaissance and surface mapping of soil and rock outcrops. The Recommendations section of this report includes interpretations and recommendations developed by the Government in the process of preparing the design.

These interpretations are not intended as a substitute for the personal investigation, independent interpretation, and judgement of the Contractor.

Attachments (3)

1) Central Federal Lands Soil Description Field Reference

2) Central Federal Lands Rock Core Description Field Reference

3) Excavation Characteristics of Rock & Rippability Charts

Prepared by:

Devin T. Dixon, P.E., Geotechnical Engineer, CFLHD

Reviewed by:

Marilyn D. Dodson, P.E., Lead Geotechnical Engineer, CFLHD for James M. Arthurs, P.E., Ph.D., Geotechnical Engineer, CFLHD

Approved by:

Marilyn D. Dodson, P.E., Lead Geotechnical Engineer, CFLHD

6 REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 2014, LRFD

Bridge Design Specifications. 7th Edition.

Anderson, R.E., 1999, “Frenchman Mountain fault (Class A) No. 1117,” Quaternary fault and fold database of the United States: U.S. Geological Survey website, <https://earthquake.usgs.gov/cfusion/qfault/show_report_AB_archive.cfm?fault_id=1117 &section_id=>.

Anderson, R.E., 1999, “California Wash Fault (Class A) No. 1118,” Quaternary fault and fold database of the United States: U.S. Geological Survey website, <https://earthquake.usgs.gov/cfusion/qfault/show_report_AB_archive.cfm?fault_id=1118 &section_id=>.

Andrew, Richard D., Bartingale, Ryan, & Howard Hume, 2011, “Context Sensitive Rock Slope Design Solutions,” Federal Highway Administration, Report No. FHWA-CFL/TD-11- 002, dated January.

Bohannon, R.G., 1992, “Geologic Map of the Weiser Ridge Quadrangle, Clark County, Nevada” 1:24,000, U.S. Geological Survey, Geologic Quadrangle Map GQ-1714.

Bowman, Andrew E., 2016, “Geohazards in Southern Nevada,” presented for the Southern Nevada Chapter of the ICC, May 2016, <http://www.snicc.org/wp-content/uploads/2016/09/SNICCGeohazardsinsouthernNevadaAndyBowman.pdf>.

Department of the Navy Facilities Engineering Command, 1986, NAVFAC, DM-7.01, “Soil Mechanics,” Design Manual.

Federal Highway Administration (FHWA), 2007, Geotechnical Technical Guidance Manual, dated May.

Federal Highway Administration (FHWA), 2020, “NV FLAP 400(1) Logandale Trails Access Road Final Pavement and Materials Report,” dated October.

Hammerpedia, 2020, “Nevada Frost Line,” Source: U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), <https://www.hammerpedia.com/nevada-frost-line/>.

House, P.K., Green, Heather, Grimmer, Abbey, & the Nevada Digital Dirt Mapping Team, 2010, “Preliminary Surficial Geologic Map of Clark County, Nevada” 1:150,000, Nevada Bureau of Mines and Geology, Open File Report 2010-07.

Nevada Bureau of Mines and Geology, 2010, “Living with Earthquakes in Nevada,” Special Publication 27, Third Edition, <http://www.seismo.unr.edu/Files/Preparedness/nvguide_2010.pdf>.

Sever, M., (2019), “Asbestos fibers thread through rocks and dust outside Vegas,” Eos 100, Published November 6th, <https://doi.org/10.1029/2019EO136324>.

U.S. Geological Survey (USGS), 2017, “Quaternary Fault and Fold Database of the United States,” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/hazards/qfaults/>.

U.S. Geological Survey (USGS), 2017, “U.S. Seismic Design Web Service Documentation (Beta),” USGS Earthquake Hazards Program, <earthquake.usgs.gov/ws/designmaps/>.

Werle, J.L. & Luke, B., 2007, “Engineering with Heavily Cemented Soil in Las Vegas, Nevada,” Copyright ASCE, GSP 162 Problematic Soils and Rocks and in Situ Characterization.

Zeitlow, Tim., 2015, “Moapa Valley flooding, 1 year later,” 8 News Now Las Vegas, Nexstar Broadcasting, Inc., <https://www.8newsnow.com/news/moapa-valley-flooding-1-year-later/>.

ATTACHMENT 1

CENTRAL FEDERAL LANDS

SOIL DESCRIPTION FIELD

REFERENCE

(Dated February 2013)

Use primary colors or hyphenated compound primary colors. Use "mottled" or "streaked" if necessary.

4. Color Dry Dry to touch, dusty Moist Damp but no visible water Wet Visible free water

5. Moisture Content

Flat Width/Thickness >3 Elongated Length/Width >3

Flat & Elongated Meets both of the above

Applies to sand, gravel, cobbles and boulders.

Length, width and thickness refer to the greatest, intermediate and least dimensions, respectively.

6c. Particle Shape

N Density N Consistency

Unconfined Compressive Strength qu

(tsf)

Undrained Compressive Strength su

(tsf)

Behavior

0-4 Very Loose 0-1 Very Soft <0.25 <0.125 Extrudes between fingers when squeezed

5-10 Loose 2-4 Soft 0.25-0.50 0.125-0.25 Remolded by light finger pressure

11-30 Medium Dense 5-8 Firm 0.50-1.00 0.25-0.50

Imprinted easily with fingers, remolded by strong finger pressure

31-50 Dense 9-15 Stiff 1.00-2.00 0.50-1.00 Imprinted with considerable finger pressure, indented by finger nail

>50 Very Dense 16-30 Very Stiff 2.00-4.00 1.00-2.00 Barely imprinted by fingers or indented by finger nail

>30 Hard >4.00 >2.00 Not imprinted by fingers or difficult to indent with finger nail

SAND & GRAVEL SILT AND CLAY

3. Consistency and Density:

Angular Sharp edges and relatively plane sides.

Subangular Same as angular with rounded edges.

Subrounded Nearly plane sides but well-rounded corners and edges.

Rounded Smooth curved sides and no edges.

Well-

Rounded Very Smooth surfaces, spherical or ovular, no edges.

6b. Particle Angularity Applies to coarse sand, gravel, cobbles and boulders.

Sieve < #200 Flour or smaller

Fine > #200 to #40 Flour to sugar Medium #40 to #10 Sugar to rock salt Course #10 to #4 Rock salt to pea-sized

Fine #4 to 3/4 in. Pea-sized to thumb Coarse 3/4 in. to 3 in. Tumb to fist Cobble 3 in. to 12 in. Fist to basketball

Boulders > 12 in. Larger than Basketball

Material

Gravel

6a. Particle Size

Silt or Clay

Sand

Particle Size Approximate Scale

Example, fine-grained soil: Lean CLAY with Sand (CL)- stiff, brown, moist, medium plasticity, laminated Example, coarse-grained soil: Silty SAND with Gravel (SM)-medium dense, gray, wet, fine to coarse grained, angular to subangular gravel, weakly cemented Example, fine-grained soil (Long Form):

Clayey GRAVEL with SAND (CL-ML)- loose to soft, dark brownish green to pale brownish gray, wet; fine to medium grained, angular, flat sand; coarse grained, rounded elongated gravel, some chert, trace coarse gravel, and cobbles, medium plasticity, dessicated, weak cementation, low dry strength, rapid dilatancy, moderate HCL reaction, hydrocarbon odor, iron oxide staining, alluvium fill, (Quaternary Alluvium), Additional Description.

1. Group Name (Pg. 3) 9.

2. Group Symbol (Pg. 3) 10.

3. Consistency / Relative Density (Pg. 1) 11.

4. Color (Pg. 1) 12.

5. Moisture (Pg. 1) 13.

6. Particle Size / Shape / Angularity (Pg. 1) 14.

7. Plasticity (Pg. 2) 15.

8. Structure (Pg. 2)

Odor (Pg. 2)

Use the following descriptive sequence when classifying soils, both in the field and when entering data into gINT:

Staining (Pg. 2)

Cementation (Pg. 2) Organics Dry Strength (Pg. 2) Dilatancy (Pg. 2) HCL Rxn (Pg. 2)

Weak Crumbles with little finger pressure Moderate Crumbles with considerable finger pressure Strong Will not crumble with finger pressure

Intact coarse-grained soil

9. Cementation

Nonplastic Thread cannot be rolled at any water content.

Low The thread can barely be rolled and the lump cannot be formed when drier than the plastic limit.

Medium The thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. The lump crumbles when drier than the plastic limit.

High It takes considerable time kneading and rolling to reach the plastic limit. The thread can be rerolled several times after reaching the plastic limit. The lump can be formed without crumbling when drier than the plastic limit.

Toughness test: Shape the specimen into an elongated pat and rolled on a smooth surface or between the palms into a thread ~1/8”. If the sample is too wet to roll, it should be allowed to dry. Fold the thread and reroll repeatedly until the thread crumbles at a diameter of ~1/8”. This will be near the plastic limit. Note the pressure required to roll the thread near the plastic limit and the strength of the thread. After the thread crumbles, the pieces should be lumped together and kneaded until the lump crumbles. Note the toughness during kneading.

On the basis of observations made during the toughness test, describe plasticity.

7. Plasticity

None No visible reaction Weak Some reaction, bubbles forming slowly Strong Violent reaction, with bubbles forming immediately

13. HCL Reaction 14. Odor 15. Staining None None

Chemical Hyrodcarbon Hyrodcarbon Iron Oxide

Organic

None No visible change Slow Water appears slowly during shaking and does not disappear or disappears slowly during squeezing.

Rapid Water appears quickly during shaking and disappears quickly during squeezing.

12. Dilatancy

1. Mold soil, adding water if necessary, into ~1/2” diameter ball with soft but not sticky consistency.

2. Smooth in palm of one hand with knife blade. Shake horizontally, striking the side of the hand vigorously against the other hand several times. Note the reaction of water appearing on the surface.

4. After Dilatancy has been determined perform the Toughness test (see explanation in #7).

3. Squeeze by closing the hand or pinching the soil between fingers. The reaction is the speed with which water appears while shaking and disappears while squeezing.

None Crumbles into powder with mere pressure of handling.

Low Crumbles into powder with some finger pressure.

Medium Breaks into pieces with considerable finger pressure.

High Cannot be broken with finger pressure, will break between hard surface and thumb.

Very High Cannot be broken between hard surface and thumb.

1. Mold a ball ~1” diameter until it has the consistency of putty, adding water if necessary.

2. From the ball, make at least 3 ½” diameter balls. Allow to air dry.

3. If the specimen contains natural dry lumps, those that are ~1/2” diameter may be used in place of molded balls.

4. Test the strength of the dry balls or lumps by crushing between the fingers.

11. Dry Strength

Stratified Alternating layers > 1/4 inch, note thickness.

Laminated Alternating layers < 1/4 inch, note thickness.

Fissured Contains shears or separations along planes of weakness.

Slickensided Shear planes appear polished or glossy, sometimes striated.

Blocky Cohesive soil can be broken down into harder, angular lumps.

Lensed Inclusion of small pockets of different soils, note thickenss.

Homogeneous Same color and appearance throughout.

Mottled Spots or patches possessing no apparent pattern Varved Distinct laminations of lacustrine sediments predominantly clayey

Desiccated Shrinkage cracks due to dehydration of fine-clayey soil

8. Structure Terms

ATTACHMENT 2

CENTRAL FEDERAL LANDS

ROCK CORE DESCRIPTION

FIELD REFERENCE

(Dated February 2013)

2. Color For consistency, describe when wet.

Use primary or hyphenated compound primary colors.

1. Rock Type Common classifications; gneiss, granite, shale, etc. A modifier may be necessary to describe a sedimentary rock formed from a combination of soil types, i.e., Silty

SANDSTONE.

V. Coarse Grained > 1/4 in.

Coarse Grained 3/16-1/4 in. Easily distinguished by naked eye Medium Grained 1/16-3/16 in. Can be distinguished by naked eye

Fine Grained Up to 1/16 in. Barley distinguished by naked eye V. Fine Grained Cannot distinguished by naked eye

3a. Grain Size

V. thickly bedded > 3ft Thickly bedded 18 in. - 3 ft Thinly bedded 2-18 in.

V. thinly bedded 3/8- 2 in.

Laminated 3/16- 3/8 in.

Thinly laminated < 3/16 in.

3c. Bedding For Sedimentary Rock

Fresh No visible sign of rock material weathering; perhaps slight discoloration on major discontinuity surfaces.

Slightly weathered Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be discolored by weathering and may be somewhat weaker externally than in its fresh condition.

Moderately weathered Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework as corestones.

Highly weathered More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework as corestones.

Completely weathered (Decomposed)

All rock material is decomposed and/or disintegrated to a soil. The original mass structure is still largely intact.

Residual Soil All rock mass is converted to a soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the volume has not been significantly transported.

4. Weathering

EXAMPLES

GNEISS- Dark gray, moderately weathered, strong. Biotite foliation, low angle, close. Quartz veins, close, low angle, stepped. Primary joint set, close, low angle, tight, moderately weathered, very narrow with rust surface staining and spotty clay infilling, rough planar. (SLIVER PLUME GRANITE) GRANODIORITE- Grey to white, medium grained, slightly weathered, strong, joints are moderate to high angle, very close, rough, open to closed, FE stained joints. Poor Circulation.

SANDSTONE- Tan to reddish brown, fine to medium grained, sub rounded, thinly bedded, moderately weathered, strong, joints are low angle, very close, closed, rough. FE surface staining throughout sample, some organics seen in joint sets.

1 Rock Type (CAPITAL LETTERS) (Pg.1) 6

2 Color (Pg.1) a. Type e. Separation 3 Grain Size or Bedding (Pg.1) b. Stratification f. Infilling & Weathering

4 Weathering (Pg.1) c. Spacing g. Roughness 5 Strength (Pg.1) d. Orientation

Discontinuities (Pg.2)

Miscellaneous (Pg.2) Formation or Unit Name (CAPITAL LETTERS)

Core should be placed in core boxes from left to right, top to bottom. The rock description for each core run should include, in this order:

Angular Show very little wear, grain edges are sharp Subangular Show definite effects of wear, grain edges slightly rounded Subrounded Shows considerable wear , grain edges rounded smooth Rounded Shows extreme wear, grain edges smoothed to broad curves Well-Rounded Very Smooth surfaces, spherical or ovular, no edges.

For Sedimentary Rock 3b. Grain Shape

3d. Structure For Sedimentary Rock

Banded Bedded

Cross Bedded Flow Banded

Foliated Interbedded Laminated Massive

R5 Very strong rock Spec imen requires many blows of geologic al hammer to fracture it. 15,000- 35,000

R2 Weak rock Can be peeled by a pocket knife with difficulty, shallow indentation made by firm blow with point of geologic al hammer. 750- 3,500

R6 Extremely strong rock Specimen can only be chipped with geological hammer. > 35,000

R3 Medium strong rock Cannot be scraped or peeled with a pocket knife, specimen c an be fractured with single firm blow of geological hammer. 3,500-7,500

R4 Strong rock Specimen requires more than one blow of geological hammer to fracture it. 7,500-15,000

R0 Extremely weak rock Indented by thumbnail. 50-150

R1 Very weak rock Crumbles under firm blows with point of geological hammer, can peeled with pocket knife. 150-750

5. Description of Relative Strength/ Hardness

Grade Description Field Identification psi

Core Measurements Recovery = Total length of recovered core / Total length of run RQD = Total length of core pieces > 4 in. / Total length of run (RQD may also be calculated separately for different rock types in one run – be consistent by project.)

RQD, Rock Quality Designation %

Description of Rock Quality

0-25 Very Poor

25-50 Poor

50-75 Fair

75-90 Good

90-100 Excellent

RELATION OF RQD & ROCK QUALITY

Foliation Planar arrangement of textural features, usually applied to schistocity or cleavage Vein A body of minerals intruded into a joint or fault Joint A break of structural origin with no visible displacement

Shear A discontinuity along which sufficient differential displacement has occurred to produce slickensides

Fault Major discontinuity with significant displacement, with gouge or adjacent zone of severely fractured rock

Shear or Fault Zone Band of closely spaced discontinuities along which differential movement has occurred Bedding A layered arrangement within the rockmass predominatly sedimentary rock.

6a. Discontinuities

Lamination Thin beds (<3/8 in.)

Fissile Tendency to break along laminations Parting Tendency to break parallel to bedding, any scale Foliation Segregation and layering of minerals in metamorphic rocks

6b. Stratification Discontinuities

Very Wide Greater than 10 ft Wide 3 – 10 ft.

Moderately Close 1 – 3 ft.

Close 2 in. – 1 ft.

Very Close Less than 2 in.

Perpendicular distance between the planes of the discontinuities.

6c. Spacing Discontinuities

Horizontal (for vertical boreholes) 0° - 5° Low Angle 5°- 35° Moderate Angle 35° - 55° High Angle 55° - 85° Vertical (for vertical boreholes) 85° - 90°

Dip angle of discontinuity should be measured with protractor to perpendicular from core axis (0° is perpendicular, 90° is parallel). To describe range of orientations, use the following terms:

6d. Orientation Discontinuities

6f. Infilling Discontinuities Types of common infilling materials include: clay, calcite, chlorite, iron oxide, gypsum/talc., pyrite, quartz, and sand.

Healed Breaks easily or with difficulty, hairline or seam, usually with infilling.

Closed Seen as a hairline trace, no infilling.

Open Core pieces separated or easily separated, may have staining or mineralization on joint surfaces.

Note: These terms are for core logging, others that describe opening width should be used for outcrop mapping.

6e. Separation Discontinuities

Slickensided Smooth, glassy surface sometime with striations.

Smooth Looks and feels smooth.

Slightly Rough Asperities are distinguishable and can be felt.

Rough Some ridges and steps are evident, asperities are clearly visible, surface feels very abrasive.

Very Rough Near-vertical steps and ridges.

6g. Roughness Discontinuities Large scale – planar, stepped, or undulating. Small scale – use the following terms:

Term % by Volume Some Vesicles 5-25

Highly Vesicular 15-50 Scoriaceous Greater than 50

For volcanics only 7a. Vesicularity 7b. Moisture 7c. Staining 7d. Odor

Damp Iron Oxide None Dripping Hydrocarbon Slight

Dry None Moderate Flowing Strong

Wet

None No visible reaction Weak Some reaction, bubbles forming slowly Strong Violent reaction, with bubbles forming immediately

7e. HCL Reaction

ATTACHMENT 3

EXCAVATION

CHARACTERISTICS OF ROCK &

RIPPABILITY CHARTS

(Provided by Various Sources)

Table A.1: Rock Hardness and Excavation Characteristics1

Rock Hardness

Description

Identification Criteria

Unconfined Compressive Strength

Seismic Compression (P-Wave) Velocity Excavation

Characteristics MPa psi m/s f/s

Very Soft Rock

Material crumbles under firm blows with sharp end of geological pick; can be peeled with a knife; too hard to cut a triaxial sample by hand. SPT will refuse. Pieces up to 3-c, thick can be broken by finger pressure.

1.7-3.0 246-435 450-1,200 1,475- 3,935 Easy Ripping

Soft Rock

Can just be scraped with a knife;

indentations 1-mm to 3-mm show in specimen with firm blows of the pick point; has dull sound under hammer.

3.0-10.0 435-1,450 1,200- 1,500

3,935- 4,920 Hard Ripping

Hard Rock

Cannot be scraped with a knife; hand specimen can be broken with a pick with a single firm blow; rock rings under hammer.

10.0-20.0 1,450- 2,900

1,500- 1,850

4,920- 6,070

Very Hard Ripping

Very Hard Rock

Hand specimen breaks with a pick after more than one blow; rock rings under hammer.

20.0-70.0 2,900- 10,150

1,850- 2,150

6,070- 7,050

Extremely Hard Ripping or Blasting

Extremely Hard Rock

Specimen require many blows with geological pick to break through intact material; rock rings under hammer.

> 70.0 > 10,150 > 2,150 >7,050 Blasting

1Table from Weaver (1975).

Table A.2: Excavation Characteristics of Rock2

Classification Elements

Class I Class II Class III Very hard ripping to blasting Hard ripping Easy ripping

Rock material requires drilling and explosives or impact procedures for excavation may classify as rock excavation (NRCS Construction

Spec. 21). Must fulfill all conditions below:

Rock material requires ripping techniques for excavation may classify as rock excavation (NRCS Construction Spec.

21). Must fulfill all conditions below:

Rock material can be excavated as common material by earth-moving or ripping equipment may classify as common excavation (NRCS

Construction Spec. 21).

Must fulfill all conditions below:

Headcut erodibility index, kh (NEH628.52) kh ≥ 100 10 < kh < 100 kh ≤ 10

Seismic velocity, approximate (ASTM

D5777 and Caterpillar Handbook of Ripping, 1997)

> 2,450 m/s (> 8,000 ft/s)

2,150-2,450 m/s (7,000-8,000 ft/s)

< 2,150 m/s (< 7,000 ft/s)

Minimum equipment size (flywheel power) required to excavate rock. All machines assumed to be heavy-duty, track-type backhoes or tractors equipped with a single tine, rear-mounted ripper.

260 kW (350 hp), for kh < 1,000

375 kW (500 hp), for kh < 10,000

Blasting, for kh > 10,000

185 kW (250 hp) 110 kW (150 hp)

1The classification is a general guide and does not prescribe the actual contract payment method to be used, nor supersedes NRCS contract documents. The classification is for engineering design purposes only.

2Table from USDA (2012).

USE OF SEISMIC VELOCITY CHARTS1

The charts of ripper performance estimated by seismic wave velocities have been developed from field tests conducted in a variety of materials. Considering the extreme variations among materials and even among rocks of a specific classification, the charts must be recognized as being at best only one indicator of rippability.

Accordingly, consider the following precautions when evaluating the feasibility of ripping a given formation:

Tooth penetration is often the key to ripping success, regardless of seismic velocity. This is particularly true in homogeneous materials such as mudstones and claystones and the fine-grained caliches. It is also true in tightly cemented formations such as conglomerates, some glacial tills and caliches containing rock fragments.

Low seismic velocities of sedimentaries can indicate probable rippability. However, if the fractures and bedding joints do not allow tooth penetration, the material may not be ripped effectively.

Pre-blasting or “popping” may induce sufficient fracturing to permit tooth entry, particularly in the caliches, conglomerates and some other rocks; but the economics should be checked carefully when considering popping in the higher grades of sandstones, limestones and granites.

Ripping is still more art than science, and much will depend on operator skill and experience.

Ripping for scraper loading may call for different techniques than if the same material is to be dozed away. Cross-ripping requires a change in approach. The number of shanks used, length and depth of shank, tooth angle, direction, throttle position all must be adjusted according to field conditions. Ripping success may well depend on the operator finding the proper combination for those conditions.

1Text and the following tables from Hawthorne Cat (2018).

Ripper Performance

● D8R/D8T

19-76

Rippers

D8R/D8T

● Multi- or Single Shank No. 8 Ripper

● Estimated by Seismic Wave Velocities

11111 51 61 2 3 4 7 8 9 10 11 12 13 14 15

2 3 410

TOPSOIL

CLAY

GLACIAL TILL

IGNEOUS ROCKS

GRANITE

BASALT

TRAP ROCK

SEDIMENTARY ROCKS

SHALE

SANDSTONE

SILTSTONE

CLAYSTONE

CONGLOMERATE

BRECCIA

CALICHE

LIMESTONE

METAMORPHIC ROCKS

SCHIST

SLATE

MINERALS and ORES

COAL

IRON ORE

Seismic Velocity Meters Per Second × 1000

Feet Per Second × 1000

RIPPABLE MARGINAL NON-RIPPABLE

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19-77

RippersRipper Performance

● D9R/D9T

D9R/D9T

● Multi- or Single Shank No. 9 Ripper

● Estimated by Seismic Wave Velocities

11111 51 61 2 3 4 7 8 9 10 11 12 13 14 15

2 3 410

TOPSOIL

CLAY

GLACIAL TILL

IGNEOUS ROCKS

GRANITE

BASALT

TRAP ROCK

SEDIMENTARY ROCKS

SHALE

SANDSTONE

SILTSTONE

CLAYSTONE

CONGLOMERATE

BRECCIA

CALICHE

LIMESTONE

METAMORPHIC ROCKS

SCHIST

SLATE

MINERALS and ORES

COAL

IRON ORE

RIPPABLE MARGINAL NON-RIPPABLE

Seismic Velocity Meters Per Second × 1000

Feet Per Second × 1000

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19-78

Rippers Ripper Performance

● D10T2

D10T2

● Multi- or Single Shank No. 10 Ripper

● Estimated by Seismic Wave Velocities

11111 51 61 2 3 4 7 8 9 10 11 12 13 14 15

2 3 410

TOPSOIL

CLAY

GLACIAL TILL

IGNEOUS ROCKS

GRANITE

BASALT

TRAP ROCK

SEDIMENTARY ROCKS

SHALE

SANDSTONE

SILTSTONE

CLAYSTONE

CONGLOMERATE

BRECCIA

CALICHE

LIMESTONE

METAMORPHIC ROCKS

SCHIST

SLATE

MINERALS and ORES

COAL

IRON ORE

Seismic Velocity Meters Per Second × 1000

Feet Per Second × 1000

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19-79

RippersRipper Performance

●…