Design Narrative

Fremont Recpath

Summit County Extension Design Narrative

Section 5 Alternatives

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5.0 Summit County Extension: Alternatives

The Summit County Extension: Design Narrative describes the action alternatives for connecting the Tenmile Canyon Recpath at Copper Mountain to the terminus of the Climax segment of the pathway at the northern boundary of the Climax property, as well as alternative routes explored in the field that were reviewed but not advanced for further study due to environmental, physical, or budgetary constraints, or reviewed but not considered to be feasible or constructible.

5.1 Alternative 1: No Action

Under the No Action Alternative, no development of a separated Pathway or expansion of the roadway surface to better accommodate bicycle travel would be pursued over Fremont Pass. The Bicycle Level of Service would remain extremely low, and the local, regional, and statewide goals for improved intermodal connectivity of the Summit and Lake County Bicycle Pathway Systems would remain unsatisfied.

Photo Plate 50 Existing condition

Lack of shoulder width to accommodate safe shared use of the road surface

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5.2 Action Alternative 2: Historic Rail Grade Alignment (Preferred Alternative)

Preliminary pathway layout considerations have prioritized following an alignment that overlays the historic route of the Highline Extension of the Denver, South Park and Pacific Railroad.

5.2.1 Historic Context: DSP&P Highline Extension

Map 4 Historic Rail Lines: Fremont Pass

The preferred alignment for the Summit County Extension of the Fremont Recpath follows the rail bed of the historic High Line Extension of the Denver South Park and Pacific Railroad (DSP&P). The “South Park” railroad started building its High Line Extension in 1881 to tap the vast riches coming from Breckenridge, Leadville, Kokomo, Robinson, and other mining camps along the line.

Route of the DSP&P High Line Extension, reorganized as the DL&G RR, and finally as the C&S RR prior to abandonment in 193712

The route went northwestward from Como, across Boreas Pass to Breckenridge, north to Frisco, then westward along the east side of Tenmile Creek, up Tenmile Canyon to the Summit of Fremont Pass (Map 4).

12 Osterwald, Doris B., High Line to Leadville, 1891 Map of Railroads in the Leadville Area, North Map. 64 Fremont Recpath

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Photo Plate 51 DSP&P Highline Extension, Climax Mill

After crossing the Continental Divide at Climax, 11,318 feet above sea level, the narrow gauge line followed the east side of the East Fork of the Arkansas River southward to the Leadville mining camp.

Engine 641 switching at the Climax Mill, Fremont Pass13

The first DSP&P passenger train to traverse the High Line left Leadville for Denver at 8:45 AM on the morning of September 30, 1884. The “South Park”, known locally as the “Seldom Punctual” railroad, cut 126 miles off of the Denver and Rio Grande (D&RG) route to Denver through Salida and Pueblo, but operations were far more difficult because the Highline crossed the Continental Divide twice, at Fremont and Boreas Passes.

Plate 52 Freight train nearing Climax

High construction and operational costs, coupled with a decline in mining activity and freight traffic forced the DSP&P into receivership, and in May of 1889, the company was reorganized as the Denver, Leadville and Gunnison Railway (DL&G).

Helper engines required to pull the grades to the Fremont Summit.14

With the repeal of the Sherman Silver Purchase Act and crash of the silver market in 1893, the silver mining industry went “bust”, and along with it, the high demand for rail

13 Denver Public Library, Western History Dept. 14 Colorado Railroad Museum 65 Fremont Recpath

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freight. The DL&G railroad was sold at foreclosure to the Colorado & Southern Railroad (C&S) on December 19, 1898.

The C&S continued its narrow gauge operations on the Highline between Leadville and Dillon into the late 1930’s. The last C&S passenger train left the Leadville Station for Denver on April 4, 1937, and the Leadville to Dillon section of the Highline was subsequently abandoned. Only that section of rail between Leadville and Climax remained open for freight traffic. It was converted to Standard Gauge in 1943 to move molybdenum to the market to aid in the war effort. The last run of the C&S freight train to Climax was in October of 1986.

Today, the Leadville, Colorado and Southern Railroad functions as a tourist train on the remnants of the C&S Highline between Leadville and Climax.

Plate 53 Cultural Resources

Although the rail bench itself has been modified from its original condition to accommodate adaptive re- use as an industrial corridor, remnants of the significant railroad history are evident along the route and can be used to interpret the role of railroads in opening the Central Colorado Rockies to exploration and settlement.

Remains of a cabin adjacent to the Highline rail grade

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5.2.2 Historic Context: Blue River Extension, D&RG Railway

Plate 54 Blue River Extension The Denver & Rio Grande Railway (D&RGW) began construction of it’s Blue River Extension from Leadville to Climax along the west side of the Arkansas River in 1880, reaching the summit of Fremont Pass on November 15, 1880. Construction continued northward to the mining camp of Kokomo in December of that year. The mining camps of Kokomo, Robinson and Recen, along with the sections of the D&RG and CSP&P rail lines that served them, are now buried beneath Climax tailings impoundments.

D&RGW Railway, Blue River Extension, Chalk Creek Trestle, Lake County, Colorado

Construction of the Blue River Extension continued down the west side of Tenmile Creek to Wheeler Junction (Copper Mountain) in 1881. The D&RG Railroad opened rail service between Leadville and Dillon on November 13, 1882. The Blue River Extension between Leadville and Dillon was abandoned on December 1, 1923.

Plate 55 Blue River Extension rail bed

Sections of the Blue River Extension, north of the Sorrel Pass Road intersection with Highway 91 (Alternative 5) were reviewed as a possible route for the Fremont Recpath west of Tenmile Creek, but were not advanced for further study due to significant environmental and geologic constraints, and the burial of sections of the historic rail bed as a result of the construction of Highway 91. (See: Section 5.4, Alternatives Reviewed but not advanced for further study)

Rail bed of the D&RGW Blue River Extension buried under the fill slope of Highway 91 67 Fremont Recpath

Summit County Extension Design Narrative

5.2.3 Selection as Preferred Alternative

The Historic Rail Grade was selected as the Preferred Alternative in recognition of its significance as an historic transportation corridor, and its physical characteristics:

 Its historic rail grades (1-5%) and rail geometry are consistent with recommended AASHTO guidelines for safe bicycle travel;  The alignment has already been re-purposed as a utility corridor for electrical, gas, and communications infrastructure;  Timber clearing along the access corridor has been maintained by the utilities, minimizing requirements for new tree clearing;  The rail grade had historically been benched into the hillside in a manner that would accommodate placement of the pathway prism on the topography with minimal new ground disturbance.  The separated Pathway isolates bicyclists from interaction with highway traffic and improves the visual and auditory quality of the mountain riding experience;  The separated Pathway bypasses the section of Highway 91 referred to as the “Narrows”, significantly improving rider safety and the Bicycle Level of Service (BLOS);

In combination, these design elements serve to limit the environmental impact of new pathway construction on the landscape, making adaptive re-use of the historically significant rail line the County’s preferred alternative.

Plate 56 Tenmile Canyon Recpath

The rail line parallels the eastern bank of Tenmile Creek at climbing grades of 1 to 5% that once accommodated narrow gauge passenger and freight trains that ran between Leadville and Dillon from 1884 through 1937. Sections of the historic Highline rail bed are already in pathway use in Summit County, underlying the paved Tenmile Canyon Recpath section from Frisco to Copper Mountain.

Copper to Frisco Section of the Tenmile Canyon Recpath Constructed over the historic rail bed of the DSP&P Highline Railroad 68 Fremont Recpath

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Plate 57 Typical section, DSP&P Railroad, Highline to Leadville

The section of the Highline rail grade between Dillon and Leadville was abandoned prior to the 1983 Congressional amendment of Section 8 (d) of the National Trails System Act that created “rail banking” provisions to preserve rail corridors through conversion to interim trails. As such, the reversionary clause on the Railroad right-or-way transferred ownership of the land beneath the track to the underlying land owner, in this case the U.S.D.A Forest Service, upon abandonment DSP&P Highline to Leadville rail bed, Summit County, Colorado

Plate 58 Historical railway infrastructure

Track and rails along the original rail bed were removed following abandonment of the C&S Railroad line between Wheeler Junction (Copper Mountain) and the summit of Fremont Pass in 1937. Remnants are still visible along the corridor.

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5.2.4 Re-purposing for Industrial Use The corridor currently accommodates overhead and underground electrical, natural gas, communications, and CATV utility line easements.

Plate 59 Industrial Corridor overlaying the DSP&P Highline rail bed

Plate 60 Timber and slash clearing to maintain the corridor

The bench into the hillside has been modified to provide additional width for construction and maintenance of buried and overhead utilities. Standard maintenance of the corridor, including periodic timber removal to provide overhead clearance and allow vehicular travel over the bench, has been performed by the utility providers.

or the purpose of providing an adequate level of topographic detail, the preferred alternative has been divided into three separate maps depicting the northern, middle and southern reaches of the pathway. 70 Fremont Recpath

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Map 5 Preferred Alternative: North Segment

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Map 6 Preferred Alternative: Mid-Segment

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Map 7 Preferred Alternative: South Segment

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5.2.5 Fen

The Historic Rail Grade Alternative passes through a Palustrine Scrub Shrub, Saturated wetland (PSSB) that includes a restored fen wetland. The fen is located between Station’s 15000+00 and 15500+00, as depicted on Map 8. The restoration area is demarcated by fencing and signage at either end of the restoration site.

Map 8 Fen Restoration Area: Area in Detail

Fence locations: Fen Restoration site.

Plate 61 Fen Restoration site: soils

Saturated soils, wetland vegetation, and a thick accumulation of peat soils are evident in select areas within the fen restoration site.

These soil types are highly susceptible to foot and vehicular traffic, that can not only trample sensitive vegetation, but can compact soils, encourage oxidation, interrupt bicarbonate cycling, and alter the natural rate of flow of groundwater through the fen soils, disrupting carbon influx and nutrient loading, and impacting the unique hydrophytic vegetation matrix. Soil plug exhibiting saturated, fibric peat soils 74 Fremont Recpath

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Plate 62 Historic rail corridor passing through fen wetland

The fen was initially damaged by construction of the DSP&P railroad in the 1880’s, prior to recognition of the wetland type as a unique and irreplaceable resource. Recreational traffic and maintenance vehicle travel over the corridor to monitor and maintain the utilities buried under the historic rail bed resulted in further damage to the hydrology, soils, and vegetation of the fen.

Vehicular rutting intercepting groundwater flow

5.2.5.1 Fen Restoration

In 2008, The Eagle River Water and Sanitation District (ERWSD) completed its second enlargement of Black Lake No. 1 on Vail Pass, raising the water surface by 4 feet, inundating 0.755 acres of wetlands, and increasing its storage capacity from 362 to 527 acre-feet. Authorization for inundation of the wetlands came in the form of an Army Corps of Engineers 404 Permit (Public Notice No. 200575151).

To compensate for the loss of 0.755 acres of wetland at Black Lake No. 1, 0.88 acres of emergent wetlands were created on-site, and 0.236 acres of fen-restorative actions were completed off-site at the Tenmile Creek location delineated on Map 8, in the NE ¼ of Section 32, Township 6S, Range 79 W.15

Monitoring and reporting are required have reached 70% wetland vegetative cover. “All sites, with the exception of the Tenmile site have achieved 70% vegetative cover and are developing characteristics of jurisdictional wetlands.”16

15 2014 Annual Monitoring Report on the Status of Wetland Mitigation Sites for the 2009 Enlargement of Black Lake No. 1, United States Corps of Engineers Permit No. 200575151 16 ibid 75 Fremont Recpath

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Plate 63 Fence and signage, fen restoration area

“The Tenmile fen restoration site experienced a setback in development in 2014. ATV vehicles operated by a contractor for Xcel Energy traversed the site over the summer destroying vegetation and creating new ruts.” Corrective actions were taken in coordination with the U.S. Forest Service in the fall of 2014. “In order to prevent damage to this sensitive fen wetland in the future, ERWSD installed buck and rail fences and replaced signage at both ends of the site.”17

Fencing to prohibit vehicular traffic across restored fen wetland

Plate 64 Interpretative Boardwalk Under the Preferred Alternative, the County would propose to span the sensitive fens with an elevated, light penetrating Pathway as described in Section 4.4.3.2. The elevated Pathway: would serve to concentrate recreational traffic onto the deck of the Pathway, rather than promoting random travel through the wetland; could be engineered to support authorized ATV traffic to monitor and maintain the underlying utilities and respond to medical emergencies; would maintain the form and function of the wetland

Interpretive platform, Potters Marsh elevated Wetland Boardwalk, Anchorage, Alaska

The elevated Pathway could also provide a platform for interpretation of the fen and surrounding ecological and cultural resources.

17 ibid 76 Fremont Recpath

Summit County Extension Design Narrative

5.3 Alternative 3 Wetland Bypass

In the event that the light penetrating elevated pathway proposed as fen mitigation along the Historic Rail Alignment does not satisfy Army Corps standards and requirements, an alignment bypassing the fen restoration area has been flagged in the field that moves the alignment up-slope of the wetland onto upland soils.

The alignment, illustrated on Map 9, circumvents the wetland section of the Historic Rail Alignment between Stations 14500+00 and 17250+00 with an upland route roughly paralleling the rail bed, through forested terrain east of the wetland.

The alignment has been laid out with grades of 3 to 4% to comply with AASHTO standards and provide comfortable ascending and descending grades. A stacked switchback has been incorporated with 60’ radius curves to maintain an 18 mile per hour design speed and to gain the elevation necessary to elevate the alignment onto the hillside above the wetlands.

The forest through which the Wetland Bypass Alignment passes has been impacted by Mountain Pine Beetle mortality. Mitigation efforts have included patch cutting of Lodgepole pine east of the proposed alignment at approximate stations 14750+00, 15500+00, 16000+00, 16400+00 and 16750+00 (See Map 9).

Plate 65 Evidence of Pine Beetle Plate 66 Patch cutting of beetle killed timber

Pitch tubes - trunk of a dead Lodgepole Edge of patch cut as viewed from the Wetland Bypass Alternative

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Map 9 Alternative 3 Wetland Bypass

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Plate 67 Ephemeral Streams and Sheet Flow

Pathway layout occurred during the week of peak run-off in June of 2015, and snow melt in the form of sheet flow and ephemeral streams was encountered on the hillside above the Fen Restoration Area. It is assumed that future design and engineering will mitigate these seasonal flows as described in Section 4, Physical and Environmental Constraints and Engineering Assumptions. .

Ephemeral stream and sheet flow, Wetland Bypass Alignment 6/18/15

Alternative 3 bypasses the fen restoration area, reconnecting with the historic DSP&P rail grade at approximate Station 14500+00, and shares the balance of its alignment along the Rail Grade with Alternative 2, as depicted on Maps 6 and 7.

Alternative 3 provides a viable alternative to circumvent the fen wetlands encountered along the Historic Rail Grade, and is advanced for further study.

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5.4 Alternatives Reviewed but not advanced for further study

Several alternative Pathway alignments were reviewed in the field, but for physical, environmental, or financial reasons were not were not advanced for further study at this level of planning.

5.4.1 Alternative 4: Highway 91 Side Path Alternative

At the request of the USFS, field investigation and preliminary path alignment flagging were conducted along the narrow band of terrain between Highway 91 and Tenmile Creek, from the point of intersection with the Tenmile Recreation Path at Copper Mountain, south to a point where sustained steep cross slope gradients and limited distance between the highway and the creek presented unacceptable constructability and environmental constraints to sustainable pathway development (Map 10.)

Plate 68 Physical constraints between Highway 91 and Tenmile Creek

At the point where path development becomes physically infeasible, the canyon of Tenmile Creek becomes deeply incised, constrained by steep slopes and near vertical cliff faces. Fill slopes supporting Highway 91 approximate the angle of repose, terminating in the riparian fringe of Tenmile Creek, eliminating the space necessary to transpose the pathway prism onto the hillside between the Highway and the Creek.

Incised drainage, insufficient space for pathway construction

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Plate 69 Hwy 91 Slope retention, MP 19.75

Stability at the head of the fill slope supporting Highway 91 south of the identified point of termination is augmented by a retaining wall consisting of driven pilings and planking to support the eastern edge of the travel surface. Expansion of the road surface to accommodate additional shoulder width or construction of a parallel side Path was not viewed as being a feasible alternative.

Soil retention to support the highway across steepened fill slopes

Plate 70 Slope termination in Tenmile Creek

The slope below the retention structure is at the angle of repose, and highly susceptible to erosion. The toe of the slope is proximal or directly adjacent to the western margin of Tenmile Creek. Any addition of fill material on the existing slope would be carried by gravity into the creek channel, making expansion of the road shoulders or construction of a parallel Pathway environmentally damaging and subject to permitting under Section 404 of the CWA.

Slope termination in Tenmile Creek Looking downslope from retention structure, MP 19.75

With access along the western bank of Tenmile Creek terminated by physical constraints, the alignment of Alternative 4 is forced to cross the riparian corridor to the east side of Tenmile Creek to access the historic rail grade of the DSP&P railroad at approximate Station 14000+00. (Map 10, Alternative 4) 81 Fremont Recpath

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Map 10: Alternative 4

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Photo Plate 71 Width constraints between Hwy 91 and Tenmile Creek The narrow band of terrain between the east side of Hwy 91 and Tenmile Creek is width constrained at several points along the corridor, between the paved edge of the highway and steep slopes dropping directly into Tenmile Creek. The spatial relationship of the natural and man- made features provides less width than is required to support the standard cut/fill pathway prism footprint (Photo Plate 71). Inadequate width to transpose standard cut/fill pathway prism onto slope

Figure 9 Engineering Assumption: Construction of retaining walls

Placement of the path prism in the width constrained sections of the alignment will require engineering solutions, such as the construction of retaining walls to support the path prism, while providing a physical barrier between riders and vehicular traffic (Figure 9). While possible, such engineering solutions add significantly to the cost of construction.

Potential engineered solution between Hwy 91 and the Tenmile Creek 83 Fremont Recpath

Summit County Extension Design Narrative

In the example shown on Plate 71, inadequate width exists between the edge of the paved road surface and the drop-off into Tenmile Creek to allow standard cut/fill pathway construction. On the upslope side of the existing bench, the road shoulder must be maintained for motorist safety, limiting the ability to cut into the existing shoulder to increase the width of the pathway base. On the down-slope side, grades approaching or exceeding the angle of repose intercept the stream bed at the base of the slope, leaving no toe to catch fill material necessary to increase the width of the pathway base. A fill solution also poses potential wetland and in-stream impacts along the riparian fringe of Tenmile Creek from deposition of side-cast fill.

AASHTO standards refer to pathways adjacent to roadways as “side Paths” and recommend either:

a) A minimum of 5 feet of physical separation between the pathway and road surface18; which cannot be accommodated in this example, or; b) Construction of physical barriers or railings to separate vehicular and bicycle/pedestrian modes of travel. Figure 9 illustrates one potential engineering response to the constraint, using guardrails imbedded in the retaining wall separating the Pathway from the road shoulder.

AASHTO guidelines also recommend the installation of fencing or railings between the edge of the Pathway pavement and the top of slopes steeper than 3:1 if the distance separating them is less than 5 feet, in order to protect trail users from the risk of running off the Path and falling down the steep incline.19 Guidelines further suggest that a reduction in path surface from 12 to 8 feet (2.4 meters) may be used for a short distance due to a physical constraint such as an environmental feature, bridge abutment, and such”, with the application of appropriate MUTCD warning signage20. This provision may be required in identified areas of width constraint to fit within the limited space.

An engineering response to these “pinch points” may take the form of a system of retaining walls to support the down-slope edge of the pathway, with AASHTO compliant railings to protect against cyclists against falling over the steep drop off, and incorporation of guardrails into the up-slope retaining wall to physically separate vehicles from bicyclists and pedestrians while maintaining adequate roadway shoulder width to ensure motorist safety (Figure 9). Specific application of the proposed solution would be determined during the engineering phase of pathway development.

Alternative 4 would also necessitate a river crossing over Tenmile Creek, and disturbance of riverine and palustrine scrub shrub (PSSC and PSSB) wetlands in the floodplain of Tenmile Creek (Figure 10).

18 AASHTO Guide for the Development of Bicycle Facilities, 2012 Fourth Edition, Section 5-4 19 AASHTO Guide for the Development of Bicycle Facilities, 2012 Fourth Edition, Section 5.2.1 20 Ibid 84 Fremont Recpath

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Figure 10 Anticipated Impacts: Alternative 4*

*Source: Summit County 2’ contour interval LIDAR mapping 85 Fremont Recpath

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Plate 72 Crossing Location – Tenmile Creek

As illustrated on Figure 10, the alignment of Alternative 4 would start at the intersection of the Tenmile Recreational Pathway at Copper Mountain, and pass in a southerly direction through the narrow band of terrain between the highway and Tenmile Creek until access is blocked by physical constraints. At this point, the pathway would have to bridge across Tenmile Creek to connect to the historic rail grade.

Potential bridge location across Tenmile Creek looking north

Plate 73 East side of Tenmile Creek crossing

After crossing to the east side of Tenmile Creek, the Pathway would require switching back through riparian wetlands, palustrine shrub scrub wetlands, and mountain meadow habitats to gain elevation in order to intersect with the historic DSP&P Highline rail grade (Figure 10).

Palustrine shrub scrub (PSSB) wetland, east side of Tenmile Creek Looking south

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Alternative 4 would place cyclists and pedestrians in close proximity to the highway at the identified width constrained points, traveling on a separated Pathway parallel to the lanes of traffic with only a minimal physical separation by space or constructed barriers to isolate the bikeway from the roadway (Figure 9). The close proximity of the pathway to the highway would subject riders to the visual and auditory impacts of the vehicular corridor, detracting from the desired riding experience. Alternative 4 would also be highly visible from the Top of the Rockies National Scenic and Historic Byway. Construction of the Pathway immediately adjacent to the Highway would logistically require lane closures during the busy summer tourist season.

The route of Alternative 4 would require construction of a bridge across Tenmile Creek and construction of an elevated grade through identified riparian corridor and palustrine shrub scrub wetland (Figure 10). It would also require all new timber clearing and excavation across the steep cross slopes separating the Highway from Tenmile Creek. Slopes approaching 50% will require extensive timber clearing limits, cuts and fills, and slope stabilization to transpose the pathway prism onto the hillside (Figure 2). Anticipated impacts are delineated on Figure 10.

Figure 10 would estimate:

 Total Length of Alternative 4 = 5,340 linear feet (vs. Alternative 2 = 4,360 linear feet)  Clearing limits and cut/fill slopes would vary with the slope gradient of the hillside being crossed  Total pathway footprint = 5.23 acres (calculated from cut/fill and clearing limits across representative slope gradients – see Figure 2)  Total length of engineered pathway grade (Retaining wall construction as illustrated on Figure 1) = 1,415 linear feet  Total pathway length through riparian and PSSB wetland = 355 linear feet  Total pathway footprint through undisturbed wetland (assuming 18’ pathway prism, 4 foot elevation above river crossing elevation, and 3:1 fill slopes) = 0.31 acres  Timber clearing in mixed conifer forest = 3.45 acres  Total pathway length through shrub / scrub and mountain meadows = 2,605 linear feet

Given the requirement for all new pathway clearing, the presence of physical and environmental constraints, associated construction costs, and proximity to the highway, Alternative 4 was reviewed but not advanced for further study at the Design Narrative level of planning.

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5.5 Alternatives Reviewed but Removed from Further Consideration

Several other alternative Pathway alignments were reviewed in the field, but for physical, environmental, or financial reasons were removed from further study at this level of planning.

The most significant of these alternative routes were analyzed in response to a request from the USFS to review options for utilizing the existing Hwy 91 right-of-way between the intersection of the Sorrel Gulch Road and Highway 91 (MP 18.46) and the termination of the Tenmile Canyon Recpath at Copper Mountain (MP 21.18), through expansion of the road surface to accommodate rideable shoulders, or through construction of a shared Pathway running parallel to either the east or west sides of the highway.

Plate 74 Highway 91 at Milepost 19.00

Highway 91 at Milepost 19: cliffs and rockfall at angle of repose on west side of highway, steep drop off directly into Tenmile Creek on the east side of Highway. Vehicular Travel lanes reduced from 12 to 11’, with riding shoulders limited to less than 2’. Speed limit 65 mph, 4,000 AADT, and 7% truck traffic.21

Physical and environmental constraints encountered within this highway segment included exposed bedrock and rockfall at its angle of repose on the west side of the highway, and steep slopes dropping directly into Tenmile Creek on the east side of the highway. Issues of slope instability, pathway geometry, wetland/riparian impacts, cost, and compliance with the standards and guidelines established in AASHTO led to the decision to remove these alternatives from consideration.

Further discussion follows:

21 Colorado DOT windshield survey photo, Highway 91 at MP 19 88 Fremont Recpath

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5.5.1 Alternative 5: Expansion along East side of Highway 91

The east side of Highway 91 parallels Tenmile Creek through the section of the highway corridor locally referred to as the “Narrows”, where shoulder widths are limited to as little as 2’ between the active travel lane and the guardrail (Figure 11). Vehicular travel lane widths between Mile Post 19.00 and 21.642 are reduced from 12’ to 11’, forcing vehicular traffic to cross the center line when passing cyclists, further limiting the road’s ability to safely and comfortably accommodate vehicular and bicycle traffic.

Figure 11 Typical Profile on East side of Hwy 91 through the “Narrows”, looking north

ROAD SURFACE SHOULDER 12' 2' CL

GUARD RAIL

20' 1:1 SLOPE

TEN MILE CREEK 20'

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Plate 75 Topography: east side of Highway 91

This section of the roadway constrains riders to the narrow shoulder between the 65 mph vehicular traffic lane, and the guardrail, and is often referenced as the prime reason people choose not to ride the Highway between Leadville and Copper Mountain.

Steep drop-offs into the creek limit opportunities to add width to Highway 91

Plate 76 Limited shoulder riding surface, Hwy 91 This condition exists in a number of locations along the east side of Highway 91 between Copper Mountain and the northern boundary of the Climax property The constrained space, riding surface condition, and high speed of traffic overtaking riders from behind provides an unsatisfactory Bicycle Level of Service, severely decreasing safety and the range of cyclists comfortable with riding this section of roadway. Quoting local riders: “If your handlebars aren’t hanging over the guardrail, your butt is hanging out in the traffic lane.”

Limited riding shoulder width through the “Narrows”.

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Plate 77 Traction sand accumulating in shoulders

Traction sand spread on the roadway to facilitate winter vehicular travel on Fremont Pass (Plate 77) also has the tendency to collect on these shoulder areas in the narrow band between the active road surface and the guardrail, reducing traction, increasing stopping distances for cyclists, and further limiting adequate width of the shoulder area to support safe travel and an acceptable BLOS.

Accumulated traction sand reducing the already narrow riding shoulder

Figure 11 also illustrates the topographic limitations of modifying the constraining fill slope to increase shoulder width, or to support the placement of the standard pathway prism on the slope between the existing shoulder and the toe of the steep slope terminating in Tenmile Creek. The addition of side-cast fill material to increase width, without the construction of retaining walls, would predictably result in the deposition of fill material into Waters of the U.S., potentially impacting the stream and riparian fringe, and triggering permitting and mitigation requirements under Section 404 of the CWA. A potential engineering solution is illustrated in Figure 12.

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Figure 12 Example: Engineering Solution to the steep constraining hillside above Tenmile Creek

ROAD SURFACE SHOULDER 12' 2' CL

GUARD RAIL

12' SAFETY RAILING RETAINING WALL TRAIL SURFACE

FILL

15' RETAINING WALL

20' 1:1 SLOPE

TEN MILE CREEK 20'

Construction of a 12 foot wide separated Pathway to provide two way traffic on the constraining slopes between the east side of the highway and Tenmile Creek would necessitate the construction of tall retaining walls as illustrated on Figure 12, or require engineering solutions such as construction of a cantilevered pathway surface. While physically possible to engineer and construct, these solutions could prove to be prohibitively expensive, visually intrusive in their position adjacent to a National Scenic Byway, environmentally damaging, and could interrupt wildlife movement to and from the Creek.

The pathway’s spatial relationship to the highway would also place pathway users in close proximity to the visual and auditory impacts of traffic on the roadway, detracting from the desired character and feel of the mountain Pathway.

Pathway development adjacent to the east side of Highway 91 was, therefore, reviewed but not advanced for further study at this level of planning.

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5.5.2 Alternative 6: Expansion along the West side of Highway 91

Plate 78 Stream/Wetland Crossing Area

Field inspection of alternative routing of a separated Pathway along the west side of Highway 91, starting at the northern boundary of the Climax property, revealed the need to cross over Tenmile Creek and its surrounding wetlands proximal to the intersection of Highway 91 and the Sorrel Pass Road to access the west side of the highway (Figure 13).

Tenmile Creek and associated riparian wetlands between Hwy 91 and the Sorrel Pass Road

The Alternative would also require an on-grade path crossing over the Sorrel Pass road leading to the Water Treatment Plant, an operational component of the Climax Mine.

Plate 79 Geologic Hazard

Once across the Sorrel Pass Road and on the west side of the highway, the alignment would almost immediately encounter a significant geologic constraint in the form of rock fall (See Appendix 2 - Geologic Investigation) beneath a cliff band extending from MP 18.75 to MP 19.19. (Figure 14)

Rockfall at angle of repose extending to Hwy 91, west shoulder.22

22 Colorado DOT windshield survey photo, Highway 91 at MP 18.735 93 Fremont Recpath

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Figure 13 Connection of Climax pathway segment to West Side Alternative

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Figure 14 Geologic Constraints, Highway 91: West Side Pathway Alternative

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Plate 80 Bedrock constraints, west side of Highway 91

As illustrated on Figure 14, the hillside on the west side of Highway 91 north of the Sorrel Pass Intersection, exhibits an extensive band of cliffs and rockfall deposition that, in places, comes right down onto the southbound shoulder of the roadway.

Exposed bedrock directly adjacent to the shoulder of Hwy 91 at MP 19

Plate 81 Rockfall Hazard, west side of Highway 91, MP 19

The rockfall has stabilized at its natural angle of repose, limiting the ability to increase the shoulder width of the existing roadway bench without cutting into and, thereby, destabilizing the toe of the slope. Ongoing rockfall resulting from destabilization of the toe of the slope could range from slow moving creep to rapid movement, posing a human health risk for pathway users and a constant maintenance requirement for the County.

Source cliff and rockfall deposition zone, west side of Highway 91

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Summit County Extension Design Narrative

Plate 82 Signs of slope mobility

Ongoing slope mobility is indicated by sloughing rock, rock scarred tree trunks, and pistol butting of the aspen trees (See: Appendix 2, Geologic Investigation), to the point where crossing the talus slope on foot exerts sufficient force to trigger movement and instability underfoot. Depth of the unconsolidated rock to a competent bedrock or soil foundation to support pathway construction is unknown.

Rock scarring and pistol butting of tree trunks are indications that the slope remains mobile

Plate 83 Constructability on rockfall

Large angular rock defies compaction, and with its significant interstitial spaces would not provide a sustainable foundation for transposition of the pathway prism onto the mobile hillside. Voids formed by the interstitial spaces beneath the sub-base layer could also result in deformation of the pathway surface, posing a human health risk and ongoing maintenance requirement.

Large angular rocks, some weighing tons, between the cliff-face and Hwy 91

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Summit County Extension Design Narrative

Plate 84 Slough from road cuts

Steep road cuts along the west side of Highway 91 constantly slough rock and soil into the drainage ditch and out onto the shoulder of the road, posing a human health risk for riders or walkers and a continuous maintenance requirement for the State. Attempts to widen the shoulder, or add a separated Pathway parallel to the west side of the highway would require significant vegetative clearing and excavation, and would still exhibit the risk of sloughing of rocks rolling onto the pathway surface.

Rocks subjected to freeze/thaw and moisture loading sloughing onto the already narrow west shoulder of Highway 91

Given the geologic hazards, human health risks, issues of constructability, and environmental impacts associated with either widening the shoulders of Highway 91 or constructing a parallel separated Pathway on the west side of Highway 91, Alternative 6 was removed from further study at this level of planning.

Selection of the proposed alignment (Alternative 2) following the existing bench of the C&S Highline Railroad: bypasses the physical constraints encountered on the east and west sides of Highway 91; more effectively isolates the pathway rider from the physical, visual, and auditory impacts of proximity to the Highway; limits new wetland impacts and the requirement for bridging Tenmile Creek, limits new tree clearing and excavation; and represents the County’s preferred alternative.

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