8.4.0 WOLFORD MOUNTAIN SITE C

8.4.1 LOCATION AND TOPOGRAPHY Wolford Mountain Site C is located on Muddy Creek, 5 miles north of Kremmling, Colorado and 3.8 miles upstream from Site A'. The dam site is a 250-foot wide canyon with sides that rise steeply to a height of approximately 80 feet. At that point, the left abutment is relatively flat for about 500 feet, continuing east to the base of Wolford Mountain. The right abutment slopes gently upwards towards Highway U.S. 40, located 0.7 miles west of the site. Figure 8.4.1 presents a plan view of the Wolford Mountain Site C.

A 120-foot high dam at Site C would impound a reservoir of 60,000 af capacity with a water surface elevation of 7485 feet. This is 10 feet higher than the water surface elevation proposed for an alternative reservoir at Site A'. Approximately 1900 acres would be occupied by the reservoir and lake shore area. An area-capacity curve is presented on Figure 8.4.2.

8.4.2 PRIOR STUDIES Wolford Mountain Site C has been under investigation by the CRWCD. A report titled "Rock Creek Dam Project", prepared by Morrison-Knudsen Engineers, Inc. (1986) for the River District, considered three reservoir capacities for this Muddy Creek Site: 60,000, 46,800 and 30,400 af. The feasibility report illustrates a preliminary design for the selected 46,800 af size. Information from this report has been liberally incorporated into this section on Wolford Mountain Site C.

The report titled "Seismotectonic Hazard Evaluation, Rock Creek Project Near Kremmling, Grand And Routt Counties, Colorado", was prepared by Michael West and Associates (1986) for Morrison-Knudsen Engineers as part of their study for the CRWCD.

A comparative review of capacities and costs of a dam at Site C and the proposed Rock Creek Dam, located 13 miles to the west, was conducted for the Municipal Subdistrict of the Northern Colorado Water Conservancy District (Swaisgood, 1983).

8-4-1 The "Wolford Mountain Reservoir Project Feasibility Report", prepared by Western (1983), provided reconnaissance-level geological, hydrological and construction cost information about the original Site C and three other sites downstream. Because of an old landslide on the left abutment of the original site, the "C" site was moved 1500 feet upstream to the present location.

B.4.3 FIELD AND LABORATORY INVESTIGATION As part of the study of Wolford Mountain Site C by Morrison-Knudsen Engineers (1986), field and laboratory investigations were performed. These included a geophysical survey in the form of seismic refraction lines along the proposed centerline of the dam, across the valley downstream of the dam and on the left abutment along a possible spillway alignment. Three core borings were drilled along the proposed dam axis, with one on each abutment and one in the floor of the valley. Core samples were recovered and in-place permeability measurements taken of the foundation bedrock. Two test pits were excavated downstream, and two upstream, in potential embankment material borrow areas. A 5-foot interval contour map was developed from aerial photographs.

Laboratory tests were conducted on samples of the material obtained from the exploratory program. Standard properties and strength characteristics were evaluated. Sources of construction materials were identified. Roller compacted concrete trial mixes using aggregates from the site were evaluated. Exploratory boring locations, logs and test results are included in the report, Rock Creek Dam Project (Morrison-Knudsen Engineers, 1986).

During this Joint-Use Reservoir and Green Mountain Exchange Study, Chen & Associates reviewed and reported upon geological information from prior studies and other published sources. This was compared with surficial observations during two site visits. Conclusions are included in the geological and geotechnical portions of this study.

B-4-2 B.4.4 REGIONAL GEOLOGY Wolford Mountain Site C is located near the western edge of the Middle Park Basin, a structural sag that formed as the Park Range was uplifted to the west and the Front Range was uplifted to the east. These major geologic structures, along with several north-trending thrust faults, were formed during a period of mountain building, known as the Laramide Orogeny, that occurred in the late to geologic epochs about 40 to 70 million years ago. A time scale and list of geologic formations in the Kremmling area are presented on Table B.4.1.

After the Laramide Orogeny, the , which is comprised largely of sandstone, conglomerate and shale, was deposited as basin fill derived from materials eroded from the adjacent uplifted formations. Igneous rock in the form of volcanic flows and breccias were deposited over the Middle Park Formation. Following this, the Troublesome Formation, which consists primarily of tufaceous siltstone and claystone, was deposited. This constitutes the youngest rock in the basin. The youngest geologic deposits in the basin, however, are alluvium, colluvium and glacial deposits.

Under the Middle Park Formation are older, pre-Laramide sedimentary rocks. Underlying these sedimentary rocks are crystalline rocks, over 600 million years old. Within the basin, the Precambrian rocks are exposed in places where they have been brought up by overthrusting along the Laramide thrust faults. This is displayed on Wolford Mountain, east of the site, where the Williams Range Thrust Fault has brought older, dark Precambrian granite over the younger, light tan shale.

B.4.5 SITE GEOLOGY The Site C Dam would be constructed across a 250 foot wide valley, with nearly vertical shale cliffs. Valley alluvium covers bedrock at the present location of Muddy Creek. Terrace alluvium overlies bedrock above the valley floor. Lower units of the bedrock are exposed in the cliffs on the valley sides, but in most places the valley sides are overlain by colluvial deposits derived from upslope rock as a result of slope wash processes.

8-4-3 TABLE B.4.1

Stratigraphic Column of the Kremmling Area (showing years before present)

ERA PERIOD EPOCH FORMATION C Alluvium E Holocene N 0 Landslide Deposits Z (10,000 years) 0 Terrace Deposits I {1 miJlion years} Pediment C Troublesome Tertiary Rabbit Ears Eocene Middle Park {65 million years} M Upper Pierre Shale E Cretaceous Niobrara S 0 Lower Dakota Sandstone Z 0 Morrison I C

Triassic

(245 miJlion years} P A L E 0 Silurian Z 0 I C (570 miJlion years} .p R E C A M B R I A N

B-4-4 8.4.5.1 Rock Units and Structures The bedrock is a hard, gray mudstone or shale. Surface outcrops are weathered to a friable, flaky, slivery material with separations along bedding planes. Since the rock has been gently folded, the strike and dip of the bedding planes vary from 2 0 to 150 within 1000 feet of the dam axis. The predominant strike near the axis of the dam is N.450 W. and the corresponding dip is 50 to the northeast. This is in the upstream direction.

Three sets of principal joints were identified in the bedrock. One set is parallel to bedding and is probably open and more pronounced at the surface due to stress relief and weathering. Occasionally these joints are oxidized for a width of about one half inch and can be followed for some distance. Spacing of these weathered joints is irregular but generally greater than 10 feet. A second principal joint set is oriented approximately vertically and strikes to the northwest. At the dam axis, the strike is nearly perpendicular to the cliff. Frequency of these joints is about 10 feet at the closest spacing, but they are generally more widely spaced. The third principal joint set is associated with the stress relief that has formed the vertical cliffs. These joints have vertical orientation and are parallel to the canyon. The frequency of these joints cannot be determined by surface mapping since they occur parallel to the outcrops. Other randomly oriented, discontinuous joints can also be observed (Morrison-Knudsen Engineers, 1986).

8.4.5.2 Surficial Deposits The cliffs bordering the valley bottom are capped by alluvial terrace deposits that form pediments, approximately 30 feet thick, which slope gently towards the abutments. The terrace deposits consist of well rounded to subrounded cobbles of sandstone, basalt and crystalline rock covered with two to three feet of weathered, light brown clay and silt. The terraces pinch out abruptly toward the abutments.

The left abutment bedrock is partially overlain by landslide debris originating from high above on Wolford Mountain. The slides appear to be associated with slabbing and toppling of the outcrops of crystalline rock above the Williams Range Thrust Fault (Morrison-Knudsen Engineers, 1986).

8-4-5 B.4.6 DESIGN CONSIDERATIONS This section addresses site factors which affect dam design. Included are foundation conditions, earthquake design, spillway requirements and construction materials. Preliminary evaluation indicated that impermeable earth materials suitable for the core of an embankment dam are available. The topography is suitable for an abutment spillway location. These are factors favorable to selection of an earth embankment design. A roller compacted concrete (RCC) design was also considered, however, laboratory tests of on-site aggregates indicated marginal durability (Morrison-Knudsen Engineers, 1986).

B.4.6.1 Foundation Conditions Selection of dam type and design is affected by depth and properties of the surface material, strength of bedrock and permeability of the foundation as well as the availability of construction materials. The foundation conditions described below are based on the interpretation by Morrison-Knudsen Engineers (1986) of the subsurface investigations, outlined .in Section B.4.3 above, performed as part of that study.

Surface Material The alluvium encountered in the valley floor was 9 to 12 feet thick and consisted of approximately 6 feet of light brown, clayey sand overlying an additional 4 feet of gray, medium grained sand, and about 2 feet of well rounded granite and basalt cobbles. The investigations indicated that the terrace material on the right abutment is about 35 feet thick, overlying a sound dark gray mudstone bedrock. A geophysical survey near the proposed spillway alignment on the left abutment and a left abutment borehole, indicated that approximately 25 feet of terrace material overlies about 15 to 35 feet of slightly weathered but jointed shale.

Rock Strength The Pierre Shale is a hard gray mudstone or shale which has weathered to a friable, flaky, slivery material with separations along bedding planes where it is exposed. Drilling indicates that the upper 8 to 10 feet of bedrock in the floor of the valley is slightly to moderately weathered. Below that depth the bedrock is massive, dark gray, sound mudstone or shale. Little jointing was apparent above a depth of 35 feet and nearly nonexistent below that depth. Most joints logged were parallel to the bedding plane and closed. The top 5 feet of the bedrock of the right abutment was found to be moderately to highly jointed along bedding planes. An angled drill hole showed the rock mass to be nearly joint free below that level.

B-4-6 The top of the bedrock on the left abutment, unlike the right abutment, was highly weathered to 6 feet and moderately jointed to a depth of about 25 feet below the contact with the gravel. Below the weathered zone, the borehole revealed the rock to be sound, massive mudstone, but more highly jointed than that found under the right abutment and in the canyon floor. Most of the joints were parallel to the shale bedding planes and many were oxidized and weathered.

The results of unconfined compressive strength tests performed on intact specimens of rock core varied from 3,153 to 10,667 psi. Based on the information available, for the purpose of preliminary stability analyses, a rock mass rating indicative of a "poor" quality rock mass was estimated for the upper 20 to 30 feet of the foundation, using the Geomechanics Classification System developed by Bieniawski (1976). Such a low rating does not indicate deficiency in the ability of the rock mass to adequately support an embankment dam. It does, however, indicate a potential for settling. In the area under the core zone the removal of several feet of weaker rock should be anticipated.

The unconfined compressive strength in conjunction with the rock mass rating enables an estimate to be developed for the rock mass strength. This rating alone, however, does not necessarily reflect the strength of the foundation. If there exist layers or seams of significantly weaker material or slickensides within the foundation it is possible for these materials to govern the strength of the foundation, depending on the location and relative extent of such layers. No such features were referred to in the available reports; however, such features are common in shales, particularly when subjected to the tectonic forces that have been exerted in the Rocky Mountains. This is an aspect of the design that will require careful attention in subsequent investigations and stability analyses.

Foundation Permeability In-place packer tests conducted below a depth of 14 feet in the bedrock of the valley floor showed the foundation to be very impervious. Tests in the bedrock of the right abutment indicated the foundation was impermeable from 5 to 15 feet below the top of rock and only

B-4-7 slightly permeable below that. Water losses were probably through the bedding plane joints mentioned above. Tests performed in the boring on the left abutment reflected the higher degree of fracturing in the rock through uniformly high water takes, up to 31 gallons per minute at 56 psi effective pressure.

The reservoir area is underlain by relatively impermeable materials and no significant leakage is expected.

8.4.6.2 Design Earthquake To develop dam stability during an earthquake, design criteria must consider the proximity of active faults as well as probable magnitude of the seismic event.

Potentially Active Faults A widely accepted criteria for defining a potentially active fault is evidence of movement, at or near the ground surface, at least once within the last 35,000 years, or evidence of a recurring nature within the last 500,000 years. Evidence of such movement is typically found where relative displacement is apparent in surficial soils overlying a fault.

The Colorado Geological Survey (Kirkham and Rogers, 1981) has made a preliminary evaluation of the earthquake potential In Colorado. In that study faults were identified which show evidence of displacement during the Quaternary geologic period, which was about the last 1 million years of tectonic activity. These faults were classified as potentially active faults. Faults in this category which are located in the vicinity of the Wolford Mountain C Site are the Antelope Pass Fault, the Williams Fork Valley Fault, the Frontal Fault, the Gore Pass Fault, and the Gore and Steamboat Springs Fault Zones which bound the western flank of the Park Range uplift. The Frontal Fault and the Gore and Steamboat Fault Zones are approximately 15 miles from the Wolford Mountain Site C at their closest points. The Williams Fork Valley Fault is approximately 12 miles, the Gore Pass Fault is approximately 4 miles and the Antelope Valley Fault is approximately 2 miles from the dam site.

8-4-8 Reconnaissance surveys have been made by others (Western, 1983; IECO, 1983; West, 1986) which present limited evidence that some of the faults cited above, may not have moved within this period. Chen & Associates recommended that until detailed investigations of the faults pertinent to dam design have been carried out, the more conservative design approach is to assume the nearby faults are potentially active.

Potential Earthquake Hazard It has been concluded by Michael West and Associates (1986) that a conservative assessment of potential earthquake hazard for the Wolford C Site would be represented by a hypothetical floating earthquake of a Richter magnitude 5.5, at an epicenter distance of 10 kilometers (6.2 miles) from the site.

For final design, it is recommended that additional geologic seismic investigations be conducted and a probabilistic analysis be carried out to confirm the design earthquake magnitude and distance from the site. The design dam section can then be analyzed for dynamic loading using the selected accelerogram time histories for both horizontal and vertical earthquake induced forces.

Other Seismic Considerations While reservoir-induced seismicity has been associated with the operation of several large reservoirs, the size reservoir that would be impounded by the dam proposed for the Wolford C Site is well below the range of reservoirs with reported large magnitude induced seismicity. Nevertheless, the potential for smaller magnitude, reservoir-induced seismicity cannot be totally ruled out. Reservoir-induced seismicity should not affect the safe operation of the reservoir where the recommended seismic ground motion is used in dam design.

8.4.6.3 Spillway Requirements The spillway size for Wolford C Dam is based on the PMF of 85,400 cfs estimated by Morrison-Knudsen Engineering, Inc., (1986). Attenuation of the peak flow by routing through the reservoir was calculated with the HEC-1 computer model (COE, 1981). Temporary storage of the storm flow over the reservoir surface to a height of 14 feet over the crest of the spillway would result in a reduced outflow for spillway design of 40,900 cfs. Maximum reservoir surface water elevation would be 7499 feet.

8-4-9 8.4.6.4 Construction Materials Field investigations conducted by Morrison-Knudsen (1986) indicate that low permeability materials, suitable for the core zone of an embankment dam, appear on the right side of the broad valley about one half mile upstream of the dam axis. A deposit of stiff, brown clay of low to medium plasticity, 10 to 15 feet thick, was encountered at elevations above the present stream channel. Material excavated at this level should not require extensive drying to prepare it for compaction. A sample tested in the laboratory showed the material to be more than 90 percent silt and clay with a Liquid Limit of 43 percent and Plasticity Index of 23 percent.

A deposit of material located downstream of the proposed left abutment was investigated as a potential source of material for the shell zones of the embankment. Index property tests on samples obtained from this deposit indicated that the samples were reasonably well graded sands and gravels, with a maximum particle size of 6 inches, containing up to 30 percent fines. Apparently no gradation tests were performed on samples from the terrace deposits on the abutments, but it is anticipated that materials of this type would also be well suited for use as shell material; however, it should be anticipated that the sands and gravels will contain significant quantities of silt owing to the general nature of alluvial deposits.

The terrace deposit on the right abutment at the dam axis was evaluated for use as material for roller compacted concrete aggregate. Tests performed on the samples cast doubt on the durability of the material. Additional tests must be conducted to determine whether local materials are suitable for use as aggregate, filter and drain material. If determined to be suitable, the material would still require processing which would include washing as well as screening. For cost estimates, hauling from sources along the Colorado River was assumed.

There is no proved source of riprap available within the Kremmling area; however, it is possible that a quarry for riprap could be developed in the granitic rocks on Wolford Mountain. Other possible sites include Red Mountain and Junction Butte near the Colorado River upstream from Kremmling. A haul distance of 12 to 15 miles was assumed for cost estimates.

B-4-10 8.4.7 DAM TYPE AND SECTION This section describes the selected dam type and the embankment and spillway section for the dam at the Wolford Mountain C Site. Due to the geologic conditions at the site and the materials potentially available for dam construction, a zoned earthfill dam has been proposed for the Wolford C Site.

8.4.7.1 Embankment Description A zoned embankment design was selected for the Wolford C Site with an interior core zone and granular shells constituting the majority of the volume. The embankment cross section is illustrated in Figure 8.4.3. A moderately sloping core zone has been selected to conserve core material because quantities at the site may be relatively limited. Such a design would also minimize the possibility for adverse deformations in the core resulting from consolidation during and subsequent to construction. The external slopes of the embankment have been set at 2.5:1 for the downstream slope and 3:1 for the upstream slope. The downstream slope would be governed by the strength properties of the embankment material and the foundation rock mass strength. The upstream slope, would be governed by these properties as well the capacity of the embankment material to drain. If the material remained saturated instability might result upon reservoir drawdown.

The upstream face of the embankment would be be covered with riprap, consisting of cobble and boulder size rock, to protect the upstream shell zone from wave action erosion. The riprap would be placed over a zone of bedding material if the potential exists for the embankment material to be washed through the riprap. The downstream face should be planted with natural grasses to control surficial erosion.

Preliminary stability analyses were performed by Boyle Engineering on potentially critical embankment sections using Bishop's Simplified Method of Slices (Bishop, 1955) applied to circular failure surfaces and Spencer's Method applied to noncircular surfaces (Spencer, 1967). Strength and material properties for the embankment were assumed on the basis of experience and are within the range of parameters typically encountered for the materials under consideration. An empirical rock mass strength criterion, developed by Hoek and Brown (1980), was established on the basis of the unconfined compressive strength of the intact rock in conjunction with the rock mass rating previously discussed in Section B.4.6.1.

B-4-11 The preliminary stability analysis focused on potential failure surfaces through both the embankment and upper portion of the foundation. The stability of the upstream and downstream slopes were evaluated at sections where the orientation of the foundation bedding planes appeared to be most unfavorable. The results of the preliminary analyses yielded adequate safety factors for preliminary design, thus confirming that the selected embankment slopes were appropriate.

8.4.7.2 Spillway Description A concrete-lined service spillway and an unlined auxiliary spillway would be provided. Each is designed as an uncontrolled Ogee section. The service spillway sill would be at elevation 7485 feet with a length of 35 feet. During the peak ouHlow of 40,900 cfs, the depth of flow at the service spillway would be 14 feet, and the depth at the auxiliary spillway, 11.5 feet. The service spillway crest structure would be located at the left abutment and positioned to minimize the required abutment treatment. The service spillway would be founded on rock and would require only one core-zone-to-concrete contact, on the right side. A deflector bucket at the downstream end of the service spillway apron would provide energy dissipation.

The auxiliary spillway would be founded in rock on the right abutment. Dam construction would extend beyond, to the right of, the auxiliary spillway. During infrequent maximum flows considerable erosion would be expected in the the lower portion of the auxiliary spillway. Such

erosion should be no threat to the security of the dam. It is expe~ted that erosion-damage repair would be required in these instances.

8.4.7.3 Foundation Excavation While there were apparently no standard penetration tests performed during the limited subsurface investigations, it is reasonable to anticipate that the alluvial sands and silts in the valley will have a low relative density, due to the nature of unconsolidated alluvial deposits. Due to the potential for collapse of the loose deposits subsequent to construction of the dam and reservoir impoundment, as well as the potential for liquefaction of loose cohesion less materials when subject to seismic loading, the approach adopted at this level of study has been to plan to excavate the alluvium from beneath the embankment.

8-4-12 It has been assumed that the entire dam would be founded on the valley floor and on the right abutment. On both abutments, the core and adjacent filter, the drain and the transition zones would need to be carried down to competent rock. The actual amount of material that may have to be excavated should be confirmed during final design with more comprehensive site investigations and stability analyses. The elevation of the water table in the valley indicates that foundation excavation will require dewatering during construction.

8.4.7.4 Seepage Control In order to prevent uncontrolled seepage through the terrace deposit on the right abutment, a positive cutoff to competent rock will be required. This would extend beyond the auxiliary spillway to intercept competent rock at the elevation of the top of the core zone. For this study, estimates have been made for a compacted earth cutoff with appropriate filter protection and provisions for drainage. Additional analysis prior to final design may show that a slurry wall that ties into the sill of the auxiliary spillway might be suitable for this purpose.

The fractured rock on the left abutment would be removed. Concrete under the spillway crest would extend to competent rock below and to the east and tie into the core zone to the west.

On the basis of the limited data available, the permeability of the foundation rock appears to decrease relatively rapidly with depth. Nevertheless, it is considered prudent to construct at least a single line grout curtain in the foundation of major earth structures in order to minimize the possibility of uncontrolled seepage through the foundation. Therefore, estimates have been made for a single line grout curtain with holes each 15 feet beneath the core zone of the dam, and limited rim grouting in the abutments, to seal off the major joints and discontinuities in the foundation rock. The actual requirements of the grout curtain are a matter that must be established on the basis of a more extensive subsurface investigation and testing program.

8.4.7.5 Foundation Treatment In order to reduce the risk of cracks forming in the core from differential settling, considerable rock excavation should be anticipated at the core zone contact with bedrock. Estimated costs include dental concrete to shape the foundation and provide a working surface

8-4-13 to commence core zone compaction. The application of slush grout has also been anticipated as part of the foundation preparation at the core zone contact. Slush grout applied at the surface of the rock can seal off joints and discontinuities that might otherwise serve as paths for the internal erosion of the material in the core zone.

B.4.8 APPURTENANCES TO THE DAM Appurtenances include the outlet works for Muddy Creek and consideration of a potential pumped storage site for hydropower.

B.4.8.1 Outlet Works A portion of the outlet works would initially serve for diversion of Muddy Creek during embankment construction. It would consist of a conduit placed in a cut-and-cover trench excavated into bedrock along the right abutment. Construction diversion is described in Section B.4.9. The 10-foot diameter diversion conduit would be converted to outlet service by insertion of a 4.0-foot diameter outlet pipe leaving an access way alongside to a guard valve installed at the upstream margin of the dam core zone. It would be completed with an intake structure and, at the outlet, a 42-inch Howell-Bunger valve to control the estimated discharge of 620 cfs.

In a cut-and-cover operation, the trench would be excavated in the foundation bedrock beneath the core zone of the embankment. It would be backfilled with concrete to the level of the prepared foundation and pressure grouted to restore the foundation integrity. This measure would not only provide seepage control, but would protect against stress distributions above the conduit that could lead to hydraulic fracturing in the core zone. The remaining length of the conduit trench would be shaped to facilitate backfill with material conforming to the requirements of the embankment zones through which the conduit passes.

B.4.8.2 Pumped-Storage Potential for Hydropower A possible upper reservoir site on Wolford Mountain has been identified, with an estimated capacity of 3000 at. It is 1.4 miles east of the Site C reservoir and 1300 feet higher in elevation. This distance to elevation-difference ratio of 5.5: 1 falls within the generally accepted topographic criteria of reservoir sites which merit analysis for use in development of pumped

B-4-14 storage hydropower. The criteria is reviewed in Section B.2.8.3 in the section on the Red Mountain Site. The site topography indicates a potential plant capacity in the 500 MW range. The practical size may depend more upon the potential market for peaking power and the economics of power transmission than the physical limitations of the site.

The capacity reserved for circulation as pumped storage (in this case approximately 3000 af) would accordingly reduce the yield of Site C reservoir for joint use or replacement purposes.

No field investigation has been conducted of this upper reservoir site, however, as stated in Section B.3.4, Regional Geology, the upper portion of Wolford Mountain is comprised of Precambrian rock overthrust along the Williams Range Thrust Fault. Where this formation was investigated at the Red Mountain Site, 6 miles south, it was found to be highly fractured and presented a relatively low shear strength, but analysis indicated it could be a satisfactory dam foundation. Potential seepage should be investigated. A reconnaissance-level investigation may be justified to indicate the geologic suitability and economic potential of this site.

B.4.9 DIVERSION FOR CONSTRUCTION Diversion of Muddy Creek during dam construction would use a portion of the outlet works conduit as a diversion conduit with upstream and downstream cofferdams. The upstream cofferdam would be incorporated in the upstream face of the dam as construction proceeds. It is estimated that a 10-foot diameter conduit would handle the 10-year spring runoff discharge which was estimated at 1500 cfs by Morrison-Knudsen Engineers (1986) for the Wolford C Site. The portion of the conduit which passes under the dam would be placed within a cut in the dam foundation bedrock. The installation and the conversion to outlet works is described in paragraph B.3.8.1.

B.4.10 HIGHWAY RELOCATION Sections of Highway U.S. 40 cross small arms of the proposed reservoir at elevations of 12 to 23 feet below the maximum water level. The alignment of the highway does not appear to hinder future reservoir operation. It is proposed to construct a new highway section on fill over existing roadway sufficiently high to be above the future water level. The length of the highway involved is approximately 5000 feet.

B-4-15 B.4.11 ESTIMATED CONSTRUCTION QUANTITIES SUMMARY An embankment dam at Wolford Site C, with a dam height of 145 feet and crest length of 1700 feet, would impound a reservoir with 60,000 af capacity. Estimated construction quantities are summarized in Table B.4.2. A detailed description of estimated construction quantities and estimated costs can be found in Chapter B.9.

TABLE B.4.2 WOLFORD C ESTIMATED CONSTRUCTION QUANTITIES SUMMARY

ESTIMATED ITEM QUANTITIES

Land Acquisition 1,900 acres Shell Volume 828,100 cubic yards Core Volume 162,650 cubic yards Drain Volume 54,000 cubic yards Filter Volume 58,800 cubic yards Transition 54,000 cubic yards Excavation 1,092,700 cubic yards Structural Concrete Volume 9,880 cubic yards Mass Concrete 12,300 cubic yards State Highway Relocation 1.0 mile

B-4-16 AND POWER DEVELOPMENT AUTHORITY JOINT-USE RESERVOIR & GREEN MOUNTAIN EXCHANGE PROJECTS WOLF E RESERVOIR

BOYLE ENGINEERING CORPORATION Con.ulling Engln ••,.

DATE NOVEMBER 1986 FIOUREB.4.1

AREA (ACRES) 2000 1600 1200 800 400 0 I Iii i

20 40 60 80 100 120 CAPACITY (1000 at)

1986

ILLWAY EL. 7488.5 100 o 100 200 SCALE FEET SPILLWAY -----\ OOLEL.7~ ~ \ "\ L__

-~ '''i-=------1 COlORADO WATEA RESOURCE. AM) POWER DEVELOPMENT AU'1lf()RITY JOINT-use RESERVOIR & GREEN MOI..tITAIN EXCHANGE PROUECTS WOLFORD C SITE DAM & Sf>ILLWAY LAYOUT ' NORMAL BOYLE ENGINEERING CORPORATION Con,ulU". En...... '. DATENOVEMBER 1986 ',GUIIE B.4.2

gl LOt- o ~ cOu.l-cx: 6'1 ~0 o O>O~O C\l-I-IOI-~3: .~::)I­ 7550 LI ~i <{'::::icoCX: SPILLWAY ·EL. 7485 a..i ~~-<:------7500 . i CRESi OF DAM EL,. 7500 _===----- r \ ~ I _------____------...... ~______fORIGINAL GROUND _--- __ -----_:_ ----- __ --.- DSTIMATED 7450 --_ -_ _------~\ //,-'-- - LIMITS OF EXCAVATION \" /?' TO ROCK 7400 /1 \,,'---... / \ ,,-..,.,,/------/ BACKFI 7350 BLANKET DRAIN AND F~;ER LJ1 ~ 1.5 100 0 100 200 \ PROFILE ALONG DAM AXIS (DEVELOPED) 7300 Ho71Z0NTAL SCALE FEET TRA.NSITII ZONE

TYPICA~RIGHT ABUTMENT SECTION \ NORMAL MAXIMUM W.S. EL. 7485 OUTLET WORKS o 20 40 80 7500 INLET STRUCTURE ~(" INTERNAL EMBANKMENT GEOMETRY SCALE FEET - ~ 2.5 -1 ORIGINAL GROUND 7450 7500 :f>'~ '"J: r- . CREST EL. . 7500 NORMAL MAXI~UMW.S. EL.7485 ESTIMATED ~ 7400 7475 -->~:~El 7350 OUTLET 7450 ~1 ~ DIVERSION STRUCTURE INLET PLUG 100 o 100 200 101 ~ HORIZONTAL SCALE FEET rSHELL ZONE 7300 7425 3'R/_~:::ZONEJ OUTLET WORKS SECTION 10' / \, BLANKET DRAIN 7400 :~:::·ORIGINAL ! ....; .. : GROUND 7500

------''7" 1 -.' ------~ . ~•.. " L --- /::~ FOREBAY POOL 2L,NORMAL --MAXiMU'M---- __ ORIGINAL GROUND 7375 ~ EL. ~ W.S. EL. 7485 \ h.5 .1475 747S=, r\ -.,;,--....:____ I • ESTIMATED ROCK --...... ( TRANSITION ZONE , ELEVATION~ ", 7450 X---:;-::~.-.------~- ...... CONCRETE APRON " TYPICAL DAM SECTIO . • ' . ._ Jr- COlORADO WATER RESOURCES OGEE SPILLWA Y . . DEFLECTOR AfC) POWEA DEVElOPMENT AUTHORITY 7425 CREST EL. 7485 :::;;; ·2· ...... ~ ...... b BUCKET JOINT-USE RESERVOIR & GREEN MOUNTAIN EXCHANGE PROJECTS TYPICAL WEEP HOLES·~-=-··-:;=.·---_ 60 o 50 100 7400 WOLFORD C SITE SERVICE SPILLWAY SECTION HORIZONTAL SCALE FEET DAM SECTIONS & PROFILE BOYLE ENGINEERING CORPORA liON c on .... It'nG E"G,"•• r.

OATE NOVEMBER 1986 "QURE B.4.3