CrystalDam(1) -FinalGeotechReport_Signed.pdf

Final

Geotechnical Report

East Portal Road, Crystal Dam Montrose, Colorado

Yeh Project No.: 219-365 October 28, 2020

Prepared for:

Federal Highway Administration, USDOT 12300 West Dakota Avenue

Lakewood, CO 80228 Attn: John Knowles

Jacobs Engineering Group 9191 S. Jamaica Street Englewood, CO 80112

Attn: Erin James

Prepared by:

Yeh and Associates, Inc.

2000 Clay Street, Suite 200

Denver, Colorado 80211 Phone: 303-781-9590

Final

Geotechnical Report East Portal Road, Crystal Dam

Montrose, Colorado

Yeh Project No.: 219-365

October 28, 2020

Prepared by: Reviewed by:

Lauren Southerland, E.I.T. Samantha Sherwood, P.E.

Staff Engineer Project Manager

Independent Reviewer:

Thomas L. Allen, P.E.

Sr. Project Manager

10/28/2020 i

Table of Contents

1. PURPOSE AND SCOPE OF STUDY

2. BACKGROUND AND GEOLOGIC SETTING

3. FIELD OBSERVATIONS

4. ANALYSES

4.1 DIPS ANALYSIS

4.2 ROCKFALL ANALYSIS

5. RECOMMENDATIONS

SCALING

CATCHMENT DITCHES

DRAPED NETTING AND MESH

ROCK REINFORCEMENT

ATTENUATOR SYSTEMS

SLOPE SPECIFIC RECOMMENDATIONS

6. LIMITATIONS

REFERENCES

LIST OF TABLES

TABLE 1 TYPICAL SLOPE CONFIGURATION

TABLE 2. SUMMARY OF POTENTIAL FAILURE MECHANISMS AT SLOPES #4 AND #5

TABLE 3. ROCKFALL CATCHMENT CAPACITY

TABLE 4. SUMMARY OF ROCFALL ASSESSMENT OF ROCK SLOPE #4

TABLE 5. SUMMARY OF ROCFALL ASSESSMENT OF ROCK SLOPE #5

LIST OF FIGURES

FIGURE 1 LOCATION OF SLOPES FOR FIELD INVESTIGATION ALONG EAST PORTAL ROAD

FIGURE 2. ROCK SLOPE #2, A HIGHLY WEATHERED SLOPE ENCOUNTERED ALONG EAST PORTAL ROAD FIGURE 3. SLOPE #3 EXHIBITS LARGE BLOCKS OF HIGHLY‐JOINTED IGNEOUS ROCKS THAT HAVE BEEN DEPOSITED DOWNSLOPE FIGURE 4. EXAMPLE OF FAULT MECHANISMS ALONG SLOPE #4, WEDGE FAILURE IN LEFT PHOTO, FAULT ZONE IN RIGHT PHOTO

FIGURE 5. VISUAL REPRESENTATION OF PLANAR, WEDGE AND TOPPLING FAILURE MECHANISMS

FIGURE 6. EXAMPLE OF ROCFALL MODEL OF ROAD STATION STA 514+00 FOR ROCK SLOPE #4

FIGURE 7. TYPICAL DRAPED MESH INSTALLATION

FIGURE 8. TYPICAL SPECIAL MESH ANCHOR INSTALLATION

LIST OF APPENDICES

APPENDIX A ROCFALL SLOPE STABILITY MODELS

East Portal Road, Crystal Dam Montrose, CO

Project No. 219-365 October 28, 2020

1. PURPOSE AND SCOPE OF STUDY

This report presents the results of our field investigation and rock slope evaluation for selected rock slopes along East Portal Road leading to Crystal Dam near Montrose, Colorado. The study was performed in accordance with our contract scope of work dated April 28, 2020. Yeh and Associates performed our work as a subconsultant to Jacobs Engineering Group (Jacobs).

Fifteen rock slopes were identified for study within the project area as shown in Figure 1. However, the focus of our analysis was specific to Rock Slopes #1 through #5.

Our scope of work included the following for the five priority sites identified (Rock Slopes #1 through #5) along the East Portal Road:

Review existing documentation such as published geologic information, geospatial data, and imagery products available for the project area, etc.

Observe conditions of Rock Slopes #1 through #5 along East Portal Road including taking scaled photos and measurements.

Conduct more detailed mapping of Rock Slopes #4 and #5 including rock geometry measurements, present failure mechanisms and other geologic features along the slope.

Perform stability and rockfall analyses of Rock Slopes #1 through #5.

Provide recommendations for feasible mitigation options.

Project No. 219-365 October 28, 2020

Figure 1. Location of slopes for field investigation along East Portal Road

2. BACKGROUND AND GEOLOGIC SETTING

East Portal Road is a two-lane, paved road that intersects US 50 east of Montrose, Colorado. The

East Portal Road provides access to Crystal Dam from the south side of the Black Canyon of the

Gunnison. The road is owned by the Bureau of Land Management (BLM) and is currently used to provide access for maintenance of facilities in the canyon. The BLM plans to make improvements to the road, specifically for safety and drainage, so it can be used as a public access for recreation. The design of the proposed improvements is being managed by the FHWA Central Federal Lands

Highway Division (CFL). The planned construction will require excavation of rock at Rock Slope #4, resulting in cut heights ranging from about 80 to 130 feet.

Through the project area, the road descends through a series of tight curves and switchbacks from approximate elevation 7780 ft to 7485 ft.

Rock Slopes #1 through #5 were prioritized by CFL for analysis and safety improvements due to

Project No. 219-365 frequent rockfall concerns and maintenance requirements, as well as project goals to improve roadway sight lines and drainage in the area of Rock Slopes #4 and #5. The representative geometry of each of the slopes, based on topographic survey data and cross sections provided by Horrocks

Engineers, Inc. (Horrocks) and Jacobs is presented in the following table.

Table 1 Typical Slope Configuration

Rock Slope

Estimated Height (ft)

Typical Slope Ratio (H:V)

Typical Existing Ditch

Width (ft)

Rock Type

#1 30‐50 1:1 7 Tuff/Diabase

#2 40‐60 1:1 7 Mixed Matrix

#3 30‐50 0.5:1 10 Tuff/Diabase

#4 120‐135 0.5:1 – 0.25:1 3 Tuff/Diabase

#5 50‐90 0.5:1 – 1:1 4 Tuff/Diabase

The bedrock geology of the project area is mapped as a biotite gneiss, schist, migmatite and tuff/diabase units (Tweto, O., et al, 1976, Hansen, 1971). The field investigation conducted April 28-

30, 2020 shows the variation in geologic formations ranging from tuff/diabase deposits, schist and granite units to the more prevalent gneiss that is present throughout the corridor surrounding East

Portal Road.

3. FIELD OBSERVATIONS

A site visit was conducted by Yeh engineers to observe slope conditions along East Portal Road. The field work consisted of geologic mapping of the selected cut slopes to aid in the design of rock excavations for widening the road and for design of rockfall mitigation. More detailed mapping, including scanlines of rock discontinuity measurements and conditions were performed for Rock

Slopes #4 and #5 where the proposed excavation to widen the road will result in tall exposed rock faces and potentially significant rockfall hazards. The lengths of the slopes were measured along the road to determine the likely extents of rockfall hazard zones. Photos were collected using a Samsung

Galaxy tablet, enabling GPS coordinates to be tied to the photos. Rock surface measurements (dip, dip direction) were collected using the smart phone application FieldMove Clino (Petex, 2020). Visible signs of potential failure mechanisms along Rock Slopes #4 and #5, such as faults and adverse rock

Project No. 219-365 joint patterns, were also noted.

Maintenance issues at the rock slopes along East Portal Road vary according to the rock type present. Rock Slope #2, shown in Figure 2, is an example of a weathered slope where soil has continually been deposited into the ditch.

Rock Slopes #1 and #3 are examples of highly-jointed, massive tuffaceous rock producing rockfall of medium to large blocks, with the largest up to approximately 1300 cubic feet in size, that have fallen downslope, as shown in Figure 3. Rocks shed from these slopes generally fall in the existing catchment and shoulder areas.

Slopes #4 and #5 were mapped in more detail to record probable wedge failure mechanisms and local fault zones, examples of which are shown in Figure 4. Wedge failures are rock masses that become dislodged due the intersection of two discontinuities that are inclined out of the slope (Higgins and Andrew, 2013). Fault zones are regions on a rock slope where rock is displaced by offset stresses and can created softened zones of rock that are weak (USGS).

Figure 2. Rock Slope #2, a highly weathered slope encountered along East Portal Road

Project No. 219-365

Figure 3. Slope #3 exhibits large blocks of highly-jointed igneous rocks that have been deposited downslope

Figure 4. Example of fault mechanisms along Slope #4, wedge failure in left photo, fault zone in right photo.

Project No. 219-365

4. ANALYSES

The five priority rock slopes were evaluated and analyzed for slope stability and rockfall potential to determine appropriate rockfall mitigation measures. Components of Roscience© software were used for our computer-aided analysis. DIPS©, a kinematic analysis software was used to evaluate possible failure mechanisms of Rock Slopes #4 and #5 from rock discontinuity data collected in the field.

SLIDE©, a 2D slope stability program, was used to evaluate factors of safety and failure mechanisms for Rock Slope #2, which was comprised of a mixed-matrix of rock and soil. ROCFALL© 2D statistical analysis software was used to evaluate possible rockfall trajectories for Rock Slopes #1, #3, #4 and

#5. Soil and rock parameters used in our analyses were drawn from previously published data and our engineering experience with similar materials. Stationing and cross sections used in the stability software models are from survey information provided by Jacobs. We did not perform subsurface exploration and no subsurface data was available for the slopes along East Portal Road. Therefore, soil and rock strength parameters and other properties were assumed, based on our field observations and engineering experience in similar geologic settings.

4.1 DIPS Analysis

The DIPS© software evaluates potential rock slope failure mechanisms based on rock joint orientation measurements made in the field and rock slope face angles measured from survey data (Rocscience, 2020a). Any potential failure mode associated with the joint patterns that can result in rockfall is reported in terms of probability, or percentage chance that the type of failure can occur.

Slopes #4 and #5 are generally stable but smaller features within the slope face could occasionally dislodge from the exposed face as weathering occurs. Rock Slope #4 exhibited a 5 to 15 percent chance of planar failure, a 30 percent chance of wedge failure, a 10 to 15 percent chance of flexural failure, and 5 to 20 percent chance of direct toppling failure. Rock Slope #5 exhibited a 25 percent chance of planar failure, a 30 to 50 percent chance of wedge failure, no probability of flexural failure, and a 25 percent chance of direct toppling failure.

The cross sections were also evaluated for stability at potential cut slope angles of 53 (1V:0.75H) and

63 degrees (1V:0.5H). The analysis of Rock Slope #4 indicated a reduced probability of failure for both wedge and flexural toppling, but a slight increase in probability for planar and direct toppling failures. Probability of failure was less than 20 percent for all for mechanisms in both cut configurations.

Project No. 219-365

A summary of the evaluated probable failure mechanisms for each slope is shown in Table 2. A visual representation of planar, wedge and toppling failures is shown in Figure 5.

Table 2. Summary of potential failure mechanisms at Slopes #4 and #5

Approximate Stationing

Max Slope Height (ft)

Existing Max Slope Angle

(deg)

Potential Failure Mechanism

Probability of Event (%)

Existing Slope

Cut at 53 degrees

Cut at 63 degrees

R o ck S lo p e

512+00 to 515+00

104 84

Planar 5 4 4

Wedge 30 11 17

Flexural Toppling 15 7 7

Direct Toppling 5 6 6

515+00 to 518+00

135 75

Planar 15 0 6

Wedge 30 1 15

Flexural Toppling 10 0 6

Direct Toppling 20 13 14

R o ck S lo p e

519+00 to 521+00

105 60

Planar 25 0 0

Wedge 50 0 0

Flexural Toppling 0 0 0

Direct Toppling 25 0 0

521+00 to 523+00

75 78

Planar 0 0 0

Wedge 30 4 11

Flexural Toppling 0 0 0

Direct Toppling 0 0 0

Project No. 219-365

4.2 Rockfall Analysis

The rockfall hazards associated with Rock Slopes #1, #3, #4 and #5 were evaluated in their existing condition, based on our field observations and the survey data. The evaluations considered the suitability of the existing ditches at the toes of the slopes for rockfall catchment using the Rockfall

Catchment Area Design Guidelines (FHWA-OR-RD-02-04m). Based on the guidance document, and the target retention of 50 percent for a low volume roadway, Rock Slopes #4 and #5 have substantially inadequate catchment areas at the toe of the slope, as shown in Table 3, below.

Figure 5. Visual representation of planar, wedge and toppling failure mechanisms.

Project No. 219-365

Table 3. Rockfall Catchment Capacity

Rock Slope

Estimated Height (ft)

Typical Slope Ratio (V:H)

Typical Existing

Ditch Width (ft)

Typical Minimum

Ditch for 50% Catchment (ft)

Typical Minimum Ditch for 75%

Catchment (ft) #1 30‐50 1:1 7 6 9

#3 30‐50 1:0.5 10 6 9

#4 60‐135* 1: 0.5–1: 0.25 3 10 14

#5 50‐90* 1:0.5 – 1:1 4 11 18

* cut height exceeds design charts maximum slope of 80 feet

Potential rockfall trajectories along several cross sections of Rock Slopes #4 and #5 were modeled using ROCFALL©. Spherical rocks with sizes ranging from to 0.5 to 1.0 ft diameter were selected for modeling in the software. The average and maximum bounce heights and kinetic energies of the selected rock sizes at the approximate edge of pavement on the rock cut side of the road are summarized in Table 4. An example of a cross section from Rock Slope #4 used in the ROCFALL analysis is shown in Figure 7.

Table 4. Summary of ROCFALL Assessment of Rock Slope #4

Cross Section Stationing

Rock Size (dia. ft)

Ditch Width (ft)

Rocks Reaching Roadway from

Upper to Mid Slope (%)

R o ck S lo p e

514+50 (existing)

0.5 3 35

1.0 3 93

514+50 (1:0.5 cut) 0.5

16 0

1.0 16 0

514+50 (1: 0.75cut)

0.5 15 0

1.0 15 0

Project No. 219-365

Table 5. Summary of ROCFALL assessment of Rock Slope #5

Cross Section Stationing

Rock Size (dia. ft)

Rocks Reaching Roadway from Mid Slope

Rocks Reaching Roadway from 15 feet (%)

R o ck S lo p e

R o ck

520+10

0.5 83 0

1.0 85 0

519+20

0.5 16 ‐

1.0 47 ‐

The figure shows the existing slope profile and the trajectories of several model rocks as they become dislodged from the slope and travel down to the roadway. The model indicates that most rocks will cross the roadway during a rockfall event and that the heights of ‘bounce’ near the toe of the slope would require a mitigation measure to contain the rockfall.

Rock Asphalt

Talus Rock

Figure 6. Example of ROCFALL model of road station STA 514+00 for Rock Slope #4.

Project No. 219-365

5. RECOMMENDATIONS

Based on our field observations of the rock slopes, the topographic survey information provided by

Jacobs, and our analysis, we believe rockfall mitigation measures are warranted for the five Rock

Slopes #4, and #5. No subsurface information was available for these rock slopes. The depth of soil cover and subsurface rock structure were assumed based on our observations.

Our analyses show that suitable mitigation measures that will reduce the rockfall hazards include scaling to remove loose rock, excavation to flatten the slopes and widen catchment areas; and installation of draped netting (either cable net, a twisted mesh, or a combination of both). These mitigation measures are discussed in more detail below. Groundwater seepage was not observed at any of the rock slope locations. However, areas of seepage may be encountered in the cut slopes during construction, especially following periods of heavy precipitation or snowmelt. Seepage will increase the potential for slope failure and rockfall as described in Section 4. If excessive water seepage is encountered, Yeh should be notified to review these recommendations.

Scaling

Scaling is the process of removing unstable rock from a slope with either hand tools and/ or mechanical equipment. This method of rockfall mitigation is used to remove rocks that have become hazards due to excavation or weathering. Scaling generally does not reshape the slope or contribute to the global stability of existing slopes. As a rockfall mitigation measure, scaling is relatively inexpensive and effective. To maintain effectiveness, scaling should be repeated every 2 to 10 years.

This time period is dependent on site-specific conditions including weather, vegetation, natural degradation of the rock face and stability of the face following construction. Scaling is often paired with other mitigation efforts including draped netting and rock reinforcement.

Catchment Ditches

A simple method to contain rockfall from roadside slopes is to construct relatively wide catchment ditches at the toes of slopes. The ditch widths required for catchment to be effective increase with taller slopes, steeper slope angles and larger source rocks. Catchment ditch geometry can be evaluated using charts derived for a range of slope heights and angles or using software such as

ROCFALL© to model site specific conditions. Constraints such as right- of-way and topography will usually limit the design width for catchment areas. Where the required catchment width cannot be provided, supplemental mitigation measures that slow rockfall velocity or control fall height can be

Project No. 219-365 used to reduce catchment widths. Measures that can improve the effectiveness of catchment ditches include draped mesh or net and rockfall attenuator systems.

Draped Netting and Mesh

In areas where constructing the required ditch width is not feasible, we recommend using draped netting or mesh to minimize the potential for rockfall generated from the rock cut that may impact the roadway. The draped net or mesh will contain the rockfall as it moves down the slope and will effectively reduce the fall height, thereby reducing the required catchment width. Draped mesh consists of relatively lightweight steel wire, twisted to form a fabric similar to chain-link fencing. Cable net is a more robust form of draped netting that is composed of steel cables (usually 3/8-inch diameter) that are mechanically connected in a grid pattern to form a heavy net fabric. Both mesh and cable net can be coated with PVC to reduce corrosion and improve appearance. Design of the draped netting requires rockfall analysis to determine netting and anchorage type and height of the bottom of the netting above the roadway for each proposed slope and catchment area. The draped netting material is typically anchored 5 to 10 feet above the top of cut and extends down to about 10 feet above the proposed ditch grade. The special mesh post system, shown in Figure 9, was developed to retain low-energy rockfall that is generated from further upslope and should be considered if the new cuts expose additional risk of rockfall sources beyond the cut lines. This post/anchor system results in the leading edge of the net or mesh being raised a few feet above the ground surface to catch rockfall from above the draped mesh or net.

Project No. 219-365

Figure 8. Typical Special Mesh Anchor Installation

Figure 7. Typical Draped Mesh Installation

Project No. 219-365

Rock Reinforcement

Rock reinforcement may be necessary to stabilize large intact blocks or groups of blocks on the slope face before and after excavation. Depending on the resisting forces required for stabilization, rock reinforcement may be post-tensioned anchors or non-tensioned dowels. Post- tensioned reinforcement would be recommended for these cuts if open fractures are observed in the rock face.

Kinematic stability analyses may indicate rock cuts that would benefit from reinforcement as the design progresses and plans are developed. In the analysis, a Factor of Safety against rock movement of 1.5 will be achieved in most cases with a rock dowel; however due to the uncertainty of the rock blasting techniques, we recommend rock bolts be assumed during design. Additional evaluation of the rock slopes by the geotechnical engineer during construction will provide guidance for the locations, number and types of rock reinforcement.

Attenuator Systems

These systems are installed across the face of hazardous rock slopes to slow the velocity of large falling rocks. The systems consist of a row or series of rows of metal posts supporting mesh or net above and away from the slope face. As rocks enter the attenuator, they contact the mesh and their speed is reduced before they exit the bottom of the attenuator and continue down the slope. Multiple attenuators deployed at critical locations or elevations along the slope reduce rockfall velocity and bounce height, improving the effectiveness of other containment or catchment systems.

Slope Specific Recommendations

Rock Slope #1- #3 – Following our thirty percent field review with the project team, we recommend no mitigation be performed at these slopes. The project team determined that funds allocated for these sites should be used for scaling rock slopes closer to the dam that were not included in our project scope.

Rock Slopes #4 and #5 ‐ Existing rockfall debris observed along Rock Slopes #4 and #5 ranged in size from 0.25 to 1 foot in diameter. However, larger rocks, (up to 5 feet in diameter) have been reported to reach the road. Models indicate the slopes, in their current condition, will continue to generate hazardous rockfall. We recommend that Rock Slope #4 be excavated at a slope ratio of 1:0.5 to improve roadway sight lines, improve drainage and provide room for rockfall catchment ditches as mitigation. Cuts at this slope should provide a minimum ditch width of 10 feet where possible. The ditch should be graded at a 4:1 slope away from the edge of the roadway. After the cut is excavated

Project No. 219-365 the slope should be scaled to remove loose rock. No cut will be performed at Rock Slope #5. Instead, this slope should be draped with a cable net or mesh to provide additional rockfall mitigation and to improve the effectiveness of the existing catchment for rockfall containment.

6. LIMITATIONS

This study was conducted in accordance with generally accepted geotechnical engineering practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report were based upon the data collected from field reconnaissance of the accessible proposed construction location in April of 2020. The nature and extent of subsurface variations across the site may not become evident until excavation is performed. If during construction rock conditions appear to be different from those described herein, this office should be advised at once so reevaluation of the recommendations may be made. We recommend on-site observation of excavations and mitigation installation by a representative of the geotechnical engineer.

In general, the information developed by this investigation is not appropriate for construction estimating and planning. The use of information contained in this report for bidding purposes shall be at the Contractor’s option and risk. Based on the intended use of the report by others, we may require that additional work be performed and a supplemental report be issued.

Noncompliance with these requirements by the Client or anyone else will release Yeh and Associates from any liability resulting from the use of this report by an unauthorized party. The cost of our work to meet with the other users and/or perform additional investigations is not included as part of this investigation.

REFERENCES

Hansen, W.R., 1971, Geologic Map of the Black Canyon of the Gunnison River and vicinity, western

Colorado, Department of Interior US Geological Survey. Miscellaneous Geologic Investigations Maps

I-584. Map.

Higgins, J.D., Andrew, R.A., 2013, Chapter 2: Rockfall Types and Causes, Rockfall: Characterization and Control. Transportation Research Board of the National Academies. Print.

Hoek, E. and Bray, J. W., 1981, Rock Slope Engineering; The Institute of Mining and Metallurgy, London, England, 358 p.

Petex, 2020, Digital Field Mapping Software, retrieved from: [https://www.petex.com/products/move-suite/digital-field-mapping/]. Retrieved June 2020.

Pierson, L., Gullixson, C.F. and Chassie, R. 2001, Rockfall Catchment Area Design Guide, Oregon Department of Transportation, FHWA.

Roscience, 2020a, DIPS, Received from: [https://www.rocscience.com/software/dips].

Received June 2020.

Rocscience, 2020b, SLIDE2, Received from: [https://www.rocscience.com/software/slide2].

Received June 2020.

Rocscience, 2020c, ROCFALL, Received from: [https://www.rocscience.com/software/rocfall] Received June 2020.

Tweto, O., Steven, T.A., Hail, W.J., Moench, R.H., 1976, Preliminary Geologic Map of the Montrose 1֩ x 2֩ ֩ Quadrangle, Southwestern Colorado. Department of Interior US Geological Survey. Miscellaneous File Studies MF-761. Map.

USGS, What is a fault and what are the different types, Received from:

[https://www.usgs.gov/faqs/what-a-fault-and-what-are-different-types?qt-news_science_products=3#qt-news_science_products].

Wiley, Duncan 2017, Rock Fall Engineering; CRC Press.

APPENDIX A

ROCFALL MODELS

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

N u m b er o f R o ck s

Location [ft]

-20

-10

S lo p e

Y L o ca ti o n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description

Block Diameter: 0.5 FT_Initiation Point: 7 - 23 FT below slope break

File Name:

520+10.fal8

Project Number and Description:

East Portal Road Rockfall Evaluation - Slope 5_Sta 520+10

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

N u m b er o f R o ck s

Location [ft]

-20

-10

S lo p e

Y L o ca ti o n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description

Block Diameter: 0.5 FT_Initiation Point: 15 FT above ditch

File Name:

520+10.fal8

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

N u m b er o f R o ck s

Location [ft]

-20

-10

S lo p e

Y L o ca ti o n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description

Block Diameter: 1 FT_Initiation Point: 7 - 23 FT below slope break

File Name:

520+10.fal8

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

N u m b er o f R o ck s

Location [ft]

-20

-10

S lo p e

Y L o ca ti o n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description

Block Diameter: 1 FT_Initiation Point: 15 FT above ditch

File Name:

520+10.fal8

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 99

Rocks Slope Rock Start

Analysis Description Block Diameter: 0.5 ft Initiation Mid Slope CompanyDrawn By SCS File Name 514+50 ex_mid_0.25.fal8Date 10/12/2020, 3:46:03 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta_514+50

ROCFALL 8.011

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter: 1 ft Initiation Mid Slope CompanyDrawn By SCS File Name 514+50 ex_mid_1D.fal8Date 10/12/2020, 3:46:03 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta_514+50

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter: 0.5 ft; Initiation Mid to Upper CompanyDrawn By SCS File Name RocFall Model2Date 10/27/2020, 10:28:19 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta 514+50 0.5 Cut

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter: 1 ft; Initiation Mid to Upper CompanyDrawn By SCS File Name 514+50 0.5 cut 1D.fal8Date 10/27/2020, 10:28:19 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta 514+50 0.5 Cut

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter: 0.5 ft; Initiation Upper Slope CompanyDrawn By SCS File Name RS 4 514+50 0.75 cut 0.5D.fal8Date 10/27/2020, 10:43:57 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta_514+50 0.75 Cut

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

N u m b er o f R oc ks

Location [ft]

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter: 1ft; Initiation Upper Slope CompanyDrawn By SCS File Name RS 4 514+50 0.75 cut 1D.fal8Date 10/27/2020, 10:43:57 PM

Project

East Portal Road Rockfall Evaluation Slope 4 Sta_514+50 0.75 Cut

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

N u m b er o f R oc ks

Location [ft]

-20

-10

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 100

Rocks Slope Rock Start

Analysis Description Block Diameter 0.5 ft_ Midpoint CompanyDrawn By SCS File Name RS 5 STA 519+20 0.5D.fal8Date 10/23/2020, 11:25:33 AM

Project

East Portal Road Rockfall Evaluation Slope 5 Sta_519+20

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

N u m b er o f R oc ks

Location [ft]

-20

-10

S lo p e

Y L oc at io n

Distribution of Rock Path End Locations

Total number of rock paths: 200

Rocks Slope Rock Start

Analysis Description Block Diameter: 1.0 ft Initiation Upper to Mid Slope CompanyDrawn By

File Name RS 5 STA 519+20 1D.fal8Date 10/23/2020, 11:25:33 AM

Project

East Portal Road Rockfall Evaluation Slope 5 Sta_519+20