NISP) Preliminary Assessment of Glade Dam and Reservoir and Associated Facilities

Technical Memorandum

To: Northern Colorado Water Conservancy District From: GEI Consultants, Inc. Date: May 10, 2006 Re: Technical Memorandum No.1: Northern Integrated Supply Project (NISP) Preliminary Assessment of Glade Dam and Reservoir and Associated Facilities

INTRODUCTION

The proposed Northern Integrated Supply Project (NISP) is a new water project that will develop water resources of the Cache la Poudre River and the South Platte River to meet water needs of 13 cities, towns, and water districts in Northern Colorado. NISP will include several reservoirs as well as water conveyance pipelines and canals. Potential reservoirs include Glade, Cactus Hill, and Galeton (which are water storage reservoirs) the Glade Forebay, and the Galeton Forebay, which are small regulating reservoirs from which water will be pumped to fill available capacity in the storage reservoirs. Cactus Hill Dam and Reservoir is an alternative to the Glade Dam and Reservoir.

The objective of this Technical Memorandum (TM-1) is to provide preliminary feasibility-level information concerning the Glade Dam and Reservoir for use by the NISP EIS consultant in evaluating alternatives. The assessments presented herein are based on existing data. The level of investigation is preliminary in nature and does not include subsurface geotechnical investigations or development of detailed engineering concepts. It also does not include an assessment of how the Glade Dam and Reservoir would be operationally integrated into the other facilities of NISP. Other TMs address the other storage elements being considered for NISP.

This TM includes descriptions of Glade Dam and Reservoir, the Glade Forebay, and modifications to existing facilities that will be required to to divert water from the Cache la Poudre River into the Forebay for pumping into Glade Reservoir and to bypass the Munroe Canal around Glade Reservoir. This bypass would be required because the Munroe Canal will be inundated by Glade Reservoir. The existing Poudre Valley Canal (PV Canal) will be used to deliver water to the Glade Forebay and to bypass the Munroe Canal around Glade Reservoir.

The primary purpose of the Glade Reservoir is to store up to 170,000 acre-feet (af) of water that would be diverted from the Cache la Poudre River. The location of Glade Reservoir and its components in relation to the other proposed NISP facilities is shown on Figure 1.1. The general project features are shown on Figure 1.2.

The Glade Forebay would be located immediately below Glade Dam, as shown on Figure 1.2. The Forebay would be created by excavation and by berm construction around the excavation to create a reservoir of approximately 2,000 af. A pumping station at the Forebay would lift water from the Forebay into storage in Glade Reservoir. Water would be supplied to the Forebay via the PV Canal, which would be upgraded to convey the requirements of both the PV Canal and Munroe Canal water users. The canal upgrading would include diversion dam modifications and improvements to the

1 canal cross-section to provide adequate flow capacity. As shown on Figure 1.2, the PV Canal would be inter-connected to the Munroe Canal by a pumping station and pipeline. The conveyance facilities are described in the Phase II Study by MWH and in reports prepared by Integra Engineering.

DESCRIPTION OF GLADE DAM AND RESERVOIR

The proposed reservoir will store approximately 170,000 af, including 3000 af of inactive storage for future sediment accumulation and active storage contents of 167,000 af. Refinement of these storage allocations and selection of the total volume of storage to be provided at the site will be undertaken during subsequent stages of project design.

By Colorado State statute, the proposed Glade Dam will be a jurisdictional dam, subject to regulatory authority of the Colorado Office of the State Engineer (SEO), Division of Water Resources. The dam must conform to applicable state dam safety rules and regulations as contained in the Rules and Regulations for Dam Safety and Dam Construction (SEO, 1988), and referred to herein as SEO Rules.

The dam is classified as “large” based on a height greater than 100 feet, and “high hazard” based on the potential for loss of life if the dam were to fail. For a new large-size, high-hazard dam, SEO Rules require use of the Probable Maximum Flood (PMF) for the Inflow Design Flood (IDF), comprehensive subsurface geotechnical investigations, stability analyses, and other evaluations and analyses consistent with SEO Rules.

Under SEO Rules and NISP objectives, the dam will require an emergency spillway to pass rare floods up to and including the PMF, a service spillway to pass smaller, more frequent floods, and an outlet works with intake tower and one or more valve houses to accommodate NISP operations, stream releases, and emergency reservoir drawdown requirements.

The Glade Reservoir basin is approximately 1.2 miles wide at its maximum and almost 4 miles long covering portions of an area called Hook and Moore Glade and an adjacent drainage. The reservoir would be “off-channel” and would not inundate the Cache la Poudre River or other perennial streams. The reservoir rim is relatively steep, except at the upper end of the reservoir basin. While the reservoir rim slopes are expected to be stable during reservoir filling and draining, periodic drawdowns below normal pool level will leave relatively large portions of the reservoir rim and upper portions of the reservoir bottom exposed.

Regional and Site Geology The proposed site for the Glade Dam and Reservoir is located in the Southern Rocky Mountains physiographic province near the border of the Great Plains physiographic province to the east. The Southern Rocky Mountains in Colorado consist predominantly of north-south trending mountain ranges once covered with sedimentary strata. The individual ranges have central cores of Precambrian rocks that were uplifted during mountain building episodes causing the Paleozoic and Mesozoic sedimentary rocks to dip away from the central cores. Uplift, faulting, folding, and erosion from Laramide time (tertiary) through late Pliocene time have modified the topography to its present configuration. The Front Range, the easternmost range of the Southern Rocky Mountain system, extends from the Colorado-Wyoming state line to the Arkansas River.

The oldest rocks in the region are Precambrian metasedimentary, metavolcanic (metamorphic), and intrusive (granitic) rocks. In general, these rocks consist of schists, gneisses, and granites of the Idaho Springs Formation. Overlying the Precambrian rocks are mostly late Paleozoic to Mesozoic

2 sandstones, shales, and limestones of continental and marine origin. The dam and reservoir sites are located primarily within these folded and faulted Paleozoic sedimentary rocks. A deposit of Quaternary alluvium covers the floors of the valley formed in the Paleozoic sedimentary rocks.

Numerous north-northwest to south-southeast-trending faults bisect the region. Three of the more prominent faults proximate to the project site include the Bellvue Fault, the Livermore Fault, and the North Fork Fault. All of the faults within the vicinity of the project are considered to be inactive. The Livermore Fault, which was once hypothesized to be potentially active, is now considered to be inactive (Unruh, 1996, and Kirkham and Rodgers, 1981).

The bedrock units at the Glade site include the Precambrian metamorphic and granitic rocks occurring in the upper part of the right abutment, faulted against Lykins siltstone in the right portion of the valley section. The central valley section consists primarily of Sundance and Jelm sandstone, and the steep part of the left abutment contains the Morrison shales and sandstones. The upper left abutment extension consists of two units of the Dakota Group mapped as the Lytle Formation conglomeritic sandstone and the South Platte Formation shales and sandstones.

The crystalline rocks and sandstone/conglomerate units are usually strong and resistant to weathering but they are jointed and fractured and therefore contain potential zones of high hydraulic conductivity. During construction of the dams for Horsetooth Reservoir, excavation into the Sundance sandstone revealed several “open and fractured joints” which subsequently were suspected of diverting drilling water during foundation grouting (USBR, 1950). These zones were grouted with curtain holes spaced on 5-foot centers.

The siltstones and shales are generally weaker rocks forming some of the strike valleys. These materials have generally lower hydraulic conductivity due to the content of silt and clay and the plasticity of these constituents. Several zones of “soft materials” were encountered in the foundation cut-off wall excavations for Horsetooth Reservoir and were over-excavated and backfilled (USBR, 1950).

The Lykins Formation is estimated to be approximately 800 to 1,000 feet thick in the Colorado- Wyoming area (Broin, 1957). The upper 500 to 700 feet of the formation is the Red Hill shale that contains predominantly red shales, siltstones and sandstones and only a few thin limestone layers. The Lykins Formation has been the subject of several geotechnical investigations at Horsetooth Reservoir involving reservoir seepage through one or more of its limestone, gypsum, or anhydrite sub-units contained in the lower 250 feet.

The southern end of the North Fork fault is mapped as intersecting the dam axis in the right valley section (Braddock, 1988). The displacement of this fault may have caused enough offset of the previously described rock units to have removed the lower problematic units of the Lykins from the dam foundation. Shear zones associated with the fault may cause additional issues regarding the construction and performance of the proposed dam, such as poor rock quality and potential seepage paths through the foundation. Additional information concerning the foundation bedrock conditions will be needed to evaluate these issues and finalize designs of a grouting program and other foundation treatment precautions.

Another fault mapped at the site involves the left abutment foundation bedrock and may be related to landslide deposits occurring in that area. The northern end of the Bellvue Fault terminates near the dam site and is probably responsible for the offset of the previously described sedimentary strata that occur immediately upstream of the Main Dam axis (Braddock, 1988). The presence of multiple

3 splays of the Bellvue Fault in the left abutment (see Figure 3.1) may explain the tilted, broken, and discordant nature of large blocks and landslide deposits in this area.

Surficial units on the valley floor include about 30 to 40 feet of undifferentiated Quaternary alluvium and colluvium deposits. The alluvium primarily consists of red to reddish-brown deposits of silt, sand, and gravel. The colluvium includes silt to cobble-sized material with occasional boulders derived from upslope outcrops and mass wasting of landslide deposits.

The region is traversed by faults whose characteristics reflect tectonic features and stress regimes of each province. The principal structural features in the region originated in Precambrian time with repetitive folding, batholithic intrusion, and faulting. Additional deformation occurred in the Paleozoic, but most of the present structural relief formed during the Laramide uplift from later Cretaceous to Eocene gradually ceasing by middle or late Eocene time, some 40 million years ago. Deformation and uplift, however, recurred in the Neogene, primarily as block faulting, producing most of the present physiography in the Front Range. It is believed that some of these same faults may have reactivated during an extensional period of regional stress contributing to the seismicity associated with the Southern Rocky Mountains.

Fault movements continued on a diminishing scale through the Pleistocene, and locally during the Holocene, particularly along the Rio Grande Rift, west of the Front Range. The region including the project site is generally considered to have low to moderate seismic activity.

Most faults are normal dip-slip or strike-slip structures characteristic of the Front Range interior. However, faults that form part of the border fault system of the Front Range uplift are mainly reverse structures.

In accordance with USBR guidelines (USBR, 1987), a return period of 50,000 years is generally considered for high-hazard structures. The proposed Glade Dam is considered a high-hazard structure. The USBR estimated a PHA of 0.3g for a return period of 50,000 years considering the potential effects of earthquakes that range in magnitude from 5.0 to 6.5. Based on the PSHA study by the USBR, a peak ground acceleration of 0.3g is selected for feasibility-level planning of the proposed Glade Dam.

Embankment Alignment The dam axis alignment is depicted on Figure 1.3. The axis generally trends northwest to southeast across Hook and Moore Glade. The final dam axis location has not been selected. An axis about 2000 feet upstream of the alignment shown on Figure 1.3 was identified in the 2002 GEI feasibility study. For permitting purposes, the District has decided to present the dam axis shown on Figure 1.3, because it is considered to be the most likely dam axis at this time.

Geotechnical Considerations The foundation below the maximum section of the dam was investigated by drilling several relatively shallow borings. Under the main section of the dam there are approximately 40 feet of alluvial/colluvial deposits, consisting generally of silty sand, clayey sand, sandy clay, and widely graded sand/gravel with silt, overlying weathered bedrock. SPT N-values within the overburden ranged from 3 to 30. The bedrock consists of decomposed red-brown clayey sandstone and decomposed white to light gray narrowly graded sandstone, the latter interpreted to be the undifferentiated Jurassic/Triassic Sundance and Jelm Formations. SPT N-values within the bedrock ranged from 47 to 100 for 4 inches of penetration.

4 Two borings were drilled near the upstream toe on the dam. Both borings were drilled vertically, to depths of 34.5 feet and 49.5 feet, respectively. A boring near the right abutment encountered about 20 feet of colluvial silty/clayey sand and about 5 feet of alluvial widely graded sand with silt and gravel, overlying weathered bedrock. The bedrock at this location generally consisted of decomposed red-brown clayey siltstone, and was interpreted to be the Pennsylvanian/Permian Fountain Formation. SPT N-values ranged from 6 to 37 within the overburden, and the SPT N-value for one sample in weathered bedrock was 31. A falling head test indicated that permeability within the overburden was generally moderate to high, on the order of 1x10-3 centimeters per second (cm/s). The other boring near the maximum section encountered about 25 feet of colluvial clayey sand and sandy silt, over about 15 feet of alluvial, widely graded sand with clay and 2 feet of alluvial sandy silt, overlying weathered bedrock. SPT N-values within the overburden varied from 2 to 70. The SPT N-values for two samples in the weathered bedrock were 100 for 4 inches of penetration and 50 for no penetration. The bedrock materials consist of decomposed red-brown to yellow-brown clayey sandstone, and were interpreted to be the undifferentiated Jurassic/Triassic Sundance and Jelm Formations.

A number of important geologic and geotechnical challenges have been identified and addressed in the development of feasibility concepts and cost estimates. These challenges include:

1. The location and character of the North Fork Fault, the Bellvue Fault, and related fault splays that cross the site. 2. Potentially liquefiable soils under both the upstream and downstream shells of the dam axis. 3. Soft clays with high settlement potential under both the upstream and downstream shells of the East Dam axis. 4. Soluble rock units in the lower portion of the Lykins Formation that underlie the dam axis.

North Fork Fault, Bellvue Fault and Fault Splays – Previous studies of the Glade site identified a Main Dam axis that crossed both the North Fork and Bellvue Faults, and related fault splays at several locations. As part of this study, an alternative axis alignment has been identified that is slightly downstream of the previously studied axis location. The new axis location appears to avoid the dam axis and footprint crossing the Bellvue Fault and related fault splays. Only one fault crossing of the North Fork Fault will be required. Eliminating the Bellvue Fault crossings substantially reduces foundation treatment costs and change order risks associated with fault crossings. Appropriate treatment provisions, including a multiple line grout curtain, are included in the feasibility design and cost estimate for the Main Dam alternative where it crosses the North Fork Fault.

Potentially Liquefiable Soils – Evaluation of the seismic hazards in the general vicinity of the site indicates a potential Maximum Considered Earthquake (MCE) event that would range in magnitude from 5.0 to 6.5. The associated peak horizontal acceleration (PHA) from such an event would be 0.3g and this level of seismic loading has been used in the evaluation of foundation soils at the site and development of the feasibility-level designs.

Field investigations indicate that foundation soils at the location of the Main Dam axis are potentially liquefiable under the earthquake loading condition described above. Feasibility- level designs and cost estimates include removal and replacement of all foundation soils beneath both the upstream and downstream shells of the Main Dam alternative. Potentially liquefiable soils are also likely under the Forebay area and some foundation treatment may be warranted based on future evaluation and design of this structure. For the purpose of this study, it was assumed that nominal flattening of embankment slopes required along the south side of the Forebay would be sufficient to address liquefaction concerns. Further studies, including additional borings and laboratory testing, should be

5 conducted to further refine and optimize foundation soil treatment requirements at the Main Dam and Forebay sites.

Soft Foundation Clays – Soft foundation clays with relatively high void ratios and compression indices were found at the location of the East Dam axis. Evaluations suggest that settlements of up to 8 feet are possible under loads from a dam if these materials are not removed. This amount of settlement is not acceptable. Therefore, feasibility-level designs and cost estimates for the East Dam axis alternative include complete removal and replacement of these materials.

Soluble Rock Units in the Lykins Formation – Soluble rock units are known to exist in the lower portions of the Lykins Formation that underlies both the Main and East Dam axes. Recent findings at Horsetooth Dam, which is located about 14 miles south of the Glade site, indicate that solution cavities will form through these materials if left untreated and that a critical failure mode may develop along the contact of the embankment with foundation materials. The feasibility-level designs and cost estimates developed for the alternative Glade Dam axis locations in this report include conservative foundation treatment concepts to address this challenge. This includes installation of a multiple line grout curtain to two-thirds to three-quarters of the estimated hydraulic height, and then installation of a concrete cutoff wall to a depth of 60 feet or more into the parts of the Lykins Formation that contain soluble rock units. The grout curtain will provide seepage reduction and will seal any foundation defects for cutoff wall construction. The cutoff wall will substantially increase the seepage pathway required for development of solution features, and will reduce the failure mode potential along the embankment contact with the Lykins Formation to an acceptable level of risk. The potential for solution features to develop around this cutoff wall has not been estimated as part of this study.

Karst Features in the Lower Ingleside Formation – Karst features (solution cavities) were encountered in the lower portion of the Ingleside Formation near the contact with the Fountain Formation during construction of Monroe Canal Tunnel No. 3. Sinkholes and significant seepage losses have also been reported at several locations along the canal associated with localized karst. Feasibility design concepts and cost estimates for the East Dam axis include a multiple-line grout curtain that fully penetrates the critical parts of the Ingleside Formation in the lower right abutment area of the dam.

The karst features in the Ingleside Formation generally consist of a system of isolated voids up to 3 feet in average dimension or systems of voids that are occasionally interconnected by jointing in the rock. While the potential exists for localized seepage associated with the karst features, it is our opinion that there is low potential for significant reservoir losses along the down-dip direction of the Ingleside Formation, or in a westerly direction out of the East Dam reservoir basin, or in a northerly direction out of either alternative reservoir basin. In our opinion further studies, including additional geologic studies and subsurface explorations, are warranted during preliminary and final design phases of the project to characterize this site condition and select appropriate treatments to reduce potential seepage losses under the dam and from the reservoir.

Soluble Rock Units and Karst Features Beneath the Forebay – Borings drilled in the proposed Forebay area indicate the potential for both soluble rock units and karst features. Feasibility designs and cost estimates for the Forebay include grouting of critical portions of the bedrock. A slurry wall will be required around a portion of the perimeter of the Forebay to separate the Forebay operation and water storage from the local groundwater system. We have assumed that the slurry wall would be a soil-bentonite type and extend only a few feet below the top of weathered bedrock. Foundation bedrock defects below the slurry wall would be treated by the grouting program.

6 A zoned earthfill dam was identified as the preferred alternative for feasibility design because of its feasibility of construction, expected lower costs, and ability to accommodate design provisions addressing the key geologic and geotechnical challenges of the sites. The spillway will be constructed in an RCC dike at one abutment. The selection was based on our understanding of the foundation conditions, construction material availability, and earthwork costs along the Front Range.

HYDROLOGY

Inflow Design Flood The IDF for Glade Reservoir will be the PMF, which will be determined following SEO guidelines. A preliminary general storm PMF estimate was developed by the District using HMR 55A and the Great Plains unit hydrograph procedure in the USBR Flood Hydrology Manual. The estimated PMF developed by the District has a peak inflow of 71,000 cfs for each of the alternative dam axis alignments. The required outflow based on reservoir routing is estimated to be 31,500 cfs with 9 feet of water over the spillway (i.e., 1 foot of freeboard).

While the rainfall, runoff, and hydrograph characteristics appear to be reasonable for preliminary engineering, further refinements will be required for final design. The SEO is revising its dam safety rules guidelines, which are scheduled to be finalized some time in 2006. The new rules will allow the IDF for new Class I dams on the Front Range to be 90 percent of the predicted PMF. Procedures for site-specific PMP studies also will be covered.

Elevation-Area-Capacity Curves Elevation-area-capacity relationships were developed by the District based on available mapping. Maximum normal pool for Glade Reservoir is estimated to be El. 5526, assuming a total storage volume of 170,000 af.

PRELIMINARY FEASIBILITY-LEVEL DAM CONCEPTS

Dam Configuration The proposed zoned earthfill embankment would have a 3H:1V upstream slope, a 40-foot-wide crest, a 2.5H:1V downstream slope, and riprap protection on the upstream slope of the embankment. The minimum crest width for a dam as high as Glade that would be acceptable to the Colorado SEO is 25 feet. The USBR would probably use at least a 40-foot-wide crest for a dam of this height and that was used by both MWH and GEI in previous studies. The zoned embankment would include a low permeability core (Zone 1) consisting primarily of lean clay obtained from the upstream reservoir basin area. The shells would consist of random fill (Zone 2) constructed primarily of clayey sand and sand obtained from a variety of borrow sources in the reservoir area, Forebay excavation, foundation excavations, and other sources to be identified. Chimney and blanket drains are shown downstream of the core connected to a toe drain. A key trench is shown excavated into the upper part of the bedrock to create a bond and partial seepage cutoff between the core and the bedrock. The low strength, compressible, and potentially liquefiable soil in the foundation has been removed and replaced with Zone 2 material to improve stability under normal and earthquake loads and to reduce settlement.

7 Embankment Zones: The zoned embankment would consist of 4 material zones or material types: Zone 1 (Core), Zone 2 (Shell), Zone 3 (Filter) and Zone 4 (Drain). The number and geometry of the zones may change in subsequent designs, as more information is obtained about the site, the material properties of the available borrow and the quantities of available materials to construct the dam. The following are descriptions of the currently envisioned embankment zones:

Zone 1 (Core) – The seepage barrier in a zoned embankment consists of a core of compacted “impervious” soil. The core for the proposed dam would consist of either compacted clay or processed weathered bedrock. The geometry of the core is designed to be approximately 10 feet wide at its upper elevation, with side slopes of approximately 1H:4V and a base width of about 160 feet at the maximum section of the dam. The core is located at the centerline of the embankment. The recommended minimum base width of the core for an embankment dam is 25 percent of the maximum difference between the normal reservoir water elevation and tail water elevations (Jansen, 1988). Seepage analyses will be required to develop the final geometry of the core in subsequent design phases.

Zone 2 (Shell) – The shell is an outer zone of material that adds strength and stability to the dam under the various loading conditions experienced over the life of the structure. Alluvial materials, consisting of silty to clayey sand and gravel with some cobbles and boulders, located within most of the proposed reservoir footprint are anticipated for the Zone 2 (Shell). Processed bedrock can also be used as a suitable source for the random fill zone.

Zone 3 (Filter) – The filter zone is a material that provides a transition between the fine grained core material and the relatively coarse gravelly sand drain material. This filter provides protection from internal erosion (piping) of the core material into the drain zone. In addition the filter zone also acts as a chimney drain within the embankment. The filter zone was described to be 3 feet in width between the Zone 1 core and Zone 4 drain and 3 feet thick between the blanket drain and foundation soils/rock. It is anticipated that the filter zone will be constructed with processed alluvial material excavated from the forebay and the reservoir footprint or purchased and hauled to the site. Because of the narrow thickness of the filter zone, a spreader box or some other mechanical means would be anticipated for construction to maintain the design thickness.

Zone 4 (Drain) – Embankment drainage would consist of a combined chimney and blanket drain to enhance stability by lowering the phreatic level in the downstream portion of the dam. The vertical chimney drain will serve to intercept seepage through the upstream shell and Zone 1 (Core) of the dam. In addition the chimney drain would intercept potential seepage on preferential seepage paths, such as compaction surfaces that are inherent in rolled fill earth dams. The blanket beneath the downstream Zone 2 shell would provide a means for seepage intercepted by the chimney drain, and under seepage from the foundation, to be conveyed to the downstream toe of the dam. The chimney and blanket drain were designed to be 3 feet thick based on the expected permeability of the embankment and foundation material. Seepage analysis will be needed in subsequent phases to size the drain thickness. However, 3 feet generally would be considered a practical thickness for construction.

Upstream Slope Protection: Slope protection is provided to protect the upstream face from erosion due to wave action. There are several methods of providing wave protection on the upstream slope of the dam including: riprap; soil cement; or asphaltic concrete or Portland cement concrete. Riprap is typically the most cost-effective method of slope protection for an embankment dam, if a source is nearby. As reported in the 2002 Feasibility Level report, it is believed that approximately 50 percent of the needed riprap for the project could be available on the project site and the remaining 50 percent of the required riprap may need to be imported from off site. We assumed that riprap

8 would be used on the upstream face of the proposed dam to provide slope protection. The upper and lower elevations of the slope protection would be based on the operation of the proposed reservoir. For the feasibility-level design and cost estimate, it was assumed that all of the riprap will be obtained from on-site borrow areas. Detailed borrow investigations and economic analyses will need to be performed during future studies to identify the most economic sources of riprap and the optimal method of slope protection.

Foundation Treatment Based on GEI’s exploratory borings, we anticipate that a weathered bedrock foundation will be encountered approximately 40 feet below the surface of the alluvial materials in the valley bottom at both dam locations. Excavation of alluvial materials and the upper part of the weathered bedrock will be required for the key trench. Similarly, excavation of all alluvial materials is required beneath the shells at the Main Dam axis location due to the liquefaction potential of these foundation soils. Excavation of all alluvial materials is required beneath the shells of the East Dam axis due to the very soft consistency of the clays and their high settlement potential. Bedrock is exposed over much of the left and right abutments. However, rock excavation is anticipated along both abutments to smooth and shape the final foundation surface of the cutoff trench and to remove loose or weak rock beneath the dam shells.

Further investigations and analysis of the potential liquefaction and settlement conditions at each axis location are warranted. Future studies should determine if alternative treatments or stabilization concepts are more economical.

We anticipate multiple phases of foundation treatment will be required to address seepage issues at both dam axis locations. The phases include areas of the foundation where a single line, exploratory grout curtain is appropriate, locations where a multiple-line grout curtain is needed, and areas of soluble rock units where concrete cutoff walls are required and constructed using slurry wall construction techniques. For purposes of our feasibility design, we have assumed that a single line exploratory grout curtain will be drilled along the entire length of the dam and RCC dike to identify zones of high grout take. A multiple-line grout curtain will be constructed by drilling grout holes to address zones of high grout take that are identified by the exploratory grout holes and zones of expected high grout take and soluble rock based on geologic information. The final depths and limits of concrete cutoff walls would be determined based on the grouting program information and constructed in zones of expected soluble rock based on geologic information.

The feasibility costs also include an allowance for foundation preparation, including cleaning and removing loose or weak rock. Foundation preparation will be required to stringent standards in the key trench to ensure a good bond between the core and the foundation rock. Foundation preparation will also be required within the footprint of the dam, but to a lesser standard than applied for the key trench. The foundation preparation program developed for the feasibility design is primarily intended to determine an allowance for cost estimating purposes. More definitive foundation preparation requirements may be identified after foundation investigations are performed. Consolidation grouting is expected to be required beneath the spillway structure at the left abutment of the Main Dam because of expected weak rock based on surficial geologic map information and the presence of faults.

9 Spillway According to SEO Rules, a minimum of 5 feet of normal-pool freeboard and 1 foot of residual freeboard (freeboard remaining at the peak of the IDF) are required. The IDF can be stored and released through a service spillway or the flood surcharge can be reduced by providing an emergency spillway. There is a tradeoff between the crest length of the emergency spillway and the height of the dam required to ensure adequate residual freeboard. During design, an iterative optimization procedure may be appropriate to minimize total construction costs or to target a preferred level of incidental flood control benefits.

The spillway would be located at the left abutment of the dam and would probably be constructed of roller-compacted concrete (RCC) with a conventional concrete stepped facing system. The crest length would be approximately 300 feet. Energy would be dissipated on the spillway steps, and in an energy dissipating basin discharging to a natural drainage below the dam.

Alternative methods for conveying the PMF design flood will be evaluated in subsequent phases of design. Some of the alternatives that should be considered in developing a final design for the Glade Dam and Reservoir would include:

 Optimization of the dam height/spillway size. An increase in the freeboard would reduce the size and cost of the spillway. The PMF could be stored within the reservoir by increasing the freeboard by 16.5 feet above the normal maximum pool.  Modification of portions or all of the concrete chute to include a combination of RCC and reinforced concrete (or all RCC) rather than a chute of reinforced concrete. An RCC concept was developed by GEI in the 2002 Feasibility Study, which also placed the spillway on the opposite side of the reservoir.  Modification of the inlet/outlet structure to incorporate an overflow spillway. This would require a second conduit and an additional tower chamber. The tower design concept would change from the current hexagonal configuration (see below) to a rectangular configuration with a wet chamber and a dry chamber.

Outlet Works The following major components, identified by MWH in the Phase II Study, would satisfy NISP operational requirements:

1. Low-level intake structure and gate. 2. Outlet works conduit, encased in concrete where it passes under the embankment and founded on bedrock. 3. Tower with multi-level intake gates and a tower access bridge. 4. Terminal facilities, including a flow-isolation valve house or vault to direct discharges to either a pipeline into the Glade Forebay or to pipeline leading to the Cache la Poudre River.

Based on site conditions, we expect that the outlet works facility construction may require extensive foundation preparation in order to provide suitable conditions and to avoid potentials for settlement of concrete structures and the conduits.

A free-standing inlet/outlet structure, located upstream of the left abutment was developed by MWH for the feasibility design. The free-standing structure provides a simple method of including multi-

10 level intakes for the reservoir to allow for water quality control. The inlet/outlet structure would be a free-standing hexagonal structure founded on bedrock, with an outside “diameter” of 48 feet and a height of about 230 feet. The outlet works was located by GEI (2002) on the opposite side of the reservoir from the location selected by MWH; however, the left abutment alignment used by MWH was retained for this presentation.

The top of the tower would be at elevation of 5532 and a low level intake invert elevation would be at 5320. The inlet/outlet structure would be founded on bedrock and may need to be anchored to bedrock with post-tensioned anchors. Control of discharges from the reservoir would be provided by eight 48 by 72-inch sluice gates, designed to release flows of 100 cfs each, located at 25-foot vertical spacings. We understand that the CDOW will be expecting the intake ports on the tower to be screened in order to prevent fish entrainment. Sizing and operation of these intake screens will be addressed during project design. A 120-inch-square guard gate would be provided on the downstream side of the tower at the opening to the inlet/outlet conduit. Once the operating criteria for the reservoir are developed, alternative structures can be further evaluated.

The outlet conduit would consist of a 120-inch-diameter steel pipe extending from the outlet tower 1500 feet through the dam to a valve building. Where the outlet pipe is located through the dam, it would be encased in concrete and be founded on bedrock. At the control building the 120-inch pipe would bifurcate with a 72-inch-diameter steel pipe leading to a discharge structure at the Poudre River and the 120-inch-diameter pipe leading to the pump station.

The valve control building would be located immediately downstream of the dam. At this building, the 120-inch-diameter outlet conduit would bifurcate with one leg of the conduit (120-inch-diameter) pipe extending to the pumping station and the other leg to the outlet reducing to a 72-inch-diameter conduit extending to the Poudre River where the outlet would discharge through a 60-inch-diameter fixed cone valve discharge structure. A 72-inch-diameter bonneted slide gate, or similar gate or valve, would be located in the 72-inch outlet line upstream of the fixed cone valve, just down stream of the bifurcation to allow for the operation of the pump station or filling of the reservoir.

GLADE FOREBAY

Water supplied from the Munroe Canal via the Poudre Valley Canal will be temporarily stored in the Glade Forebay for pumping into Glade Reservoir. Feasibility concepts and costs for a Forebay with 2,000 ac-ft of temporary storage capacity were developed by GEI. Feasibility concepts and costs for the pump station were developed by the District.

Foundation Conditions The location proposed for the Forebay consists of approximately 25 to 44 feet of Quaternary alluvium and colluvium deposits overlying Owl Canyon siltstone, Lyons sandstone, Lykins shale, and Sundance sandstone bedrock formations. The alluvium consists of red to reddish-brown deposits of silt, sand, and gravel. The colluvium includes silt to cobble-sized material with occasional boulders derived from upslope outcrops. The bedrock formations are generally weathered and in some areas decomposed and non-cemented.

11 If the excavation for the Forebay remains within the alluvium and colluvium deposits, a slurry cutoff wall connecting to the bedrock will be necessary due to the relatively loose and porous nature of the valley fill material. In addition, some grouting of the bedrock will be required to minimize seepage losses/gains during operation of the Forebay.

Four subsurface borings were performed under GEI supervision for the 2002 study. The objectives of the exploration program were to: a) investigate the condition of the soil and bedrock in the Forebay area; b) establish the elevation of firm rock within area; c) obtain samples of the soil and weathered bedrock for classification and laboratory analysis; d) perform hydraulic tests in the soil and rock portions of the borings to estimate the permeability of the materials; and e) evaluate the suitability and availability of overburden soils as potential borrow material for the Forebay dam embankment.

The north-central portion of the Forebay was drilled vertically to a total depth of about 55 feet, and encountered about 40 feet of colluvial overburden generally consisting of clayey sand. A sample of alluvial widely graded sand was encountered at about 40 feet, and weathered bedrock was encountered at about 45 feet. SPT N-values within the overburden varied from 3 to 25. The weathered bedrock generally consisted of decomposed red-brown clayey siltstone with more resistant intensely weathered siltstone at the very bottom of the hole. SPT N-values within the weathered bedrock ranged from 50 for 4 inches of penetration to 50 for 1 inch of penetration. The bedrock was interpreted to be the Triassic/Permian Lykins Formation. A falling head test performed in this boring indicated that the permeability of the overburden is moderate to low, based on an observed drop in water level of about 10 feet in a 60-minute period and when compared to the results of other falling head tests performed at the site.

The southwest corner was drilled vertically to a total depth of nearly 55 feet, and encountered approximately 25 feet of overburden over bedrock. The overburden generally consisted of colluvial clayey sand, sandy low plasticity clay, and silty sand. SPT N-values within the overburden ranged from 4 to 29. The bedrock consisted of red-brown siltstone, the upper 10 feet of which was sufficiently weathered that it could be penetrated by auguring. SPT N-values for two samples collected within the weathered bedrock were 100 for 6 inches of penetration and 60 for 4 inches of penetration. The bedrock was typically moderately weathered with some very intensely weathered zones. Fractures were moderately to closely spaced, and RQD values varied from 18 to 62 percent. The bedrock contained calcite veins throughout, and a probable slickensided fracture at 51.5 feet. Bedrock at this location was interpreted to be the Permian Owl Canyon Formation. A falling head test performed in the overburden and weathered bedrock portion of the hole indicated that hydraulic conductivity was moderate to low, on the order of 1x10-5 cm/s.

The southeast portion of the Forebay was drilled vertically to a total depth of about 55 feet, and encountered about 40 feet of colluvial/alluvial overburden that generally consisted of silty/clayey sand, widely graded sand with clay, widely graded sand with silt and gravel, and silt over weathered bedrock. SPT N-values within the overburden varied from 2 to 105 for 9 inches of penetration. The weathered bedrock generally consisted of decomposed red-brown clayey sandstone and clayey siltstone. The bedrock is interpreted to be the Triassic/Permian Lykins Formation. A falling head test performed in this boring indicated that the permeability of the overburden is moderately high, on the order of 1x10-3 cm/s.

The eastern portion of the Forebay was drilled vertically to a total depth of about 45 feet, and encountered about 44 feet of colluvial/alluvial overburden, the upper 32 feet of which generally consisted of silty/clayey sand, widely graded sand with silt and variable percentages of gravel, and sandy elastic silt. SPT N-values in this zone varied from 1 to 36. The lower 12 feet of overburden

12 consisted of red-orange to red-brown widely graded sand with gravel and clay, and clayey gravel with sand. The granular fraction (sand and gravel) was typically bound in a clayey matrix. The color of this material was similar in appearance to the weathered bedrock encountered elsewhere around the site; however, the granular fraction included a rounded piece of quartz gravel and a decomposed mica schist cobble, suggesting alluvial deposition. A falling head test performed in this boring indicated that the permeability of the overburden is moderately high, on the order of 1x10-4 cm/s.

Forebay Configuration The Glade Forebay will be created by a combination of excavation and low dam construction on the northern rim of the reservoir. Materials excavated from the Forebay will be used for constructing the low dam and for Glade Dam. The Forebay will be isolated from the ground water regime by installation of perimeter slurry walls keyed into unweathered bedrock. The pumping station at the Forebay will be located on Figure 1.3.

Diversion and Canal Modifications As described previously, the water for storage in Glade Reservoir would be diverted at the existing PV Canal diversion dam, which would need to be modified. Diverted water would be conveyed in the modified PV Canal to the Glade Forebay for pumping into Glade Reservoir. These facilities are described in other project documentation.

CONSTRUCTION MATERIALS AND CONSIDERATIONS

Construction Materials Overview The primary materials required for dam construction are several types of earthfill for the embankments; concrete, structural steel and reinforcing steel for the spillway and outlet works; prefabricated bridge components for the tower access bridge; riprap and bedding for the spillway and the outlet works terminal facilities; riprap and bedding or soil cement for upstream slope protection; grout for the grout curtain; steel pipe; and various mechanical and electrical components such as gates, valves and instrumentation.

On-Site and Imported Materials Based on previous investigations at the project site and geologic field reconnaissance conducted by both GEI and MWH, we believe suitable borrow materials can be obtained in the proposed reservoir area upstream of the dam, from foundation excavations for the dam and spillway, from the Forebay excavation, and excavations in the middle ridge dividing the two valleys. Borrow investigations have not been completed for this study or previous investigations. Quantities and types of available borrow will need to be evaluated to optimize the design of a cost-effective embankment.

Suitable core material can most likely be obtained from the upstream reservoir basin area. Shell material for the embankment could be obtained from excavated alluvium, colluvium, and bedrock on the site. It is also expected that some material that could be processed and used for filter material could be obtained from processed alluvium in the area of the forebay, though this quantity is unknown. Most likely, filter and drain materials and riprap and riprap bedding will need to be imported from off-site sources. These materials will be obtained from existing or new commercial quarries. Materials also need to be imported for construction of the grout curtain, outlet works, and emergency spillway. These materials include cement grout, concrete, reinforcing steel, structural steel, steel pipe, gates, valves, flow meters, and hydraulic controls. Concrete may be batched on

13 site, in which case aggregates and cement, flyash, and admixtures will be brought to the site and stockpiled within the contractor staging and lay-down areas shown on Figure 1.3.

Sources of borrow for riprap may be available on site. Up to 50 percent of the required riprap slope protection may be available from borrow areas established in the reservoir (GEI, 2002). Suitable riprap material can be obtained from the limestones of the Ingleside and Owl Canyon Formations, from the more massively bedded sandstones in the reservoir and from the metavolcanic rock in the massive Precambrian formations along the west rim of the reservoir. We have used the assumption that all of the required riprap slope protection would be obtained from borrow areas established in the reservoir. An “off-site” source for riprap would be the large cut required for the Highway 287 relocation, which would be made through the hogback just north and east of the upper portion of the reservoir. Sandstone of the Lytle Formation would provide suitable riprap, but would require temporary stockpiling and result in “double-handling” of the material, in addition to the haul of approximately 5 miles. Use of this source will be explored further during design of the highway relocation.

Most likely, filter and drain materials and riprap and riprap bedding will need to be imported from off- site sources. These materials will be obtained from existing or new commercial quarries. Materials also need to be imported for construction of the grout curtain, outlet works, and emergency spillway. These materials include cement grout, concrete, reinforcing steel, structural steel, steel pipe, gates, valves, flow meters, and hydraulic controls. Concrete may be batched on site, in which case aggregates and cement, flyash, and admixtures will be brought to the site and stockpiled within the contractor staging and lay-down areas shown on Figure 1.3.

Construction Water Water supply for construction will come either from a well or wells on site, the Munroe Canal, or directly from the Cache la Poudre River. Depth to groundwater has not been determined. Temporary water supply facilities would be needed to convey water from these sources to the point of use.

Access and Construction Facilities Site facilities associated with construction of Glade Dam and Reservoir will include a gravel surfaced access road, staging area(s), and borrow areas for construction materials. The proposed reservoir area and dam alignment are accessible and provision for site access, staging, and access to borrow areas is not considered be an issue. Access roads will be needed to provide access to the pump station control facility, the left abutment, the downstream toe of the dam, and borrow areas. We have assumed that the existing Highway 287 from Fort Collins to the site will be used to provide general access to the site (see Figure 1.3). Potentially, access roads developed for construction could become permanent roads to allow recreational access and access for operation, maintenance, and monitoring at the dam.

Stream Diversion and Site Dewatering Temporary facilities will be required to facilitate stream diversion and dewatering of the site during construction. These facilities will likely include pumps and cofferdams. Saturated soils at the dam site and in potential upstream borrow areas must be dried and/or processed to ensure target moisture contents are met during embankment construction.

14 Other Facilities Other facilities required for the dam and reservoir will include: an access and maintenance road from an existing road to the downstream outlet works facilities and to the dam crest; security fences and gates; and (potentially) a building or buildings to house maintenance equipment. Public access and recreation facilities may be provided but are not part of the engineering aspects of the project presented in this TM.

Construction Operations Construction of Glade Dam will involve on-site excavation and placement of approximately 18,710,000 cubic yards (cy) of earth materials and delivery and placement of approximately 576,000 cy of earth and rock materials from off-site sources, assuming that, if the Highway 287 cut through the hogback provides riprap for the project, this represents an on-site source. Based on similar projects, we estimate that construction would require up to 5 years, assuming some slow down in operations during cold-weather periods.

Initial construction activities would include construction of access roads, establishing staging, stockpile, and storage areas and on-site offices (trailers), and installation of electrical, communications, water, and sanitary facilities. Acceptable locations for these activities will be determined during final design; however, preliminary locations are identified on Figure 1.3 to aid in assessing project impacts for the EIS.

The size of the contractor’s work force and equipment spread for dam construction will depend on the proposed construction plan and schedule. Based on similar projects, we anticipate an average work force of about 90 to 100 persons, with a peak force of approximately double that number at certain times. Construction activities would be confined to the limits of disturbance shown on Figure 1.3. Dozers, scrapers, trucks, and loaders will be the major equipment pieces used during construction of Galeton Dam. We estimate 3,734 equipment months of use during construction (one equipment month is 173 hours of use for that piece of equipment in a month).

Materials trucked from off site are expected to include: cement and concrete aggregates, assuming that concrete is batched on site or pre-mixed concrete if obtained from commercial operations; riprap and riprap bedding; sand and gravel for filters and drains; reinforcing steel; steel pipe; pre-fabricated steel for various structures and the tower bridge; gates, valves, and electrical equipment; and fuel for construction equipment and vehicles. Assuming off-site concrete batching, we expect an average of four mixer trucks per day during outlet works construction, up to 56 semi-tractor trucks for bringing embankment materials from the off-site sources, and up to 100 trucks per day during riprap and bedding deliveries.

15 OPINION OF PROBABLE COST

Costs for constructing Glade Dam and Reservoir were estimated based on major cost categories and estimated quantities of the major construction items. Lump sum costs are representative based on opinions of probable cost for comparable facilities and GEI experience. The opinion of total probable cost is provided in Table 1.1.

DEVELOPMENT ISSUES

General The following sections identify some of the key issues that should be evaluated in subsequent preliminary and final design phases if this storage alternative is selected as part of NISP.

Topographic Mapping A high-resolution topographic map will be required for the embankment, reservoir, and construction areas. Ground control surveys will also be required.

Foundation and Embankment Issues Develop more detailed understandings of the location and character of the North Fork Fault, the Bellvue Fault and related fault splays that cross the site.

Evaluate whether or not there are potentially liquefiable soils under both the upstream and downstream shells of the dam axis.

There are soluble rock units in the lower portion of the Lykins Formation that underlie both the dam axis. Further evaluation of these rock units and the need for grouting, slurry wall cutoffs, and seepage blankets will be critical during design.

Evaluate the potential for the occurrence of soluble rock and karst features under the Glade Forebay.

Additional test pits, geologic mapping, drilling, and laboratory testing will be needed to determine the characteristics and quantities of available embankment material. Excavation requirements will need to be evaluated in greater detail to develop a more reliable opinion of quantities, materials requirements, and probable construction costs.

The leakage potentials of the various geologic formations and features should be thoroughly investigated by coring and packer testing. The extent of fractures, bedding planes, other cavities, and anticipated grout take should also be evaluated. Seepage analyses should be conducted to determine the rate of flow through the system.

Abutment Issues The reservoir rim slopes are relatively flat. However, the potential for sloughing of the reservoir rim during high water, high wind, and drawdown conditions should be investigated.

16 Spillway Issues Evaluate the left and right abutment locations for suitability for construction of an emergency spillway.

Confirm the desirability and cost effectiveness of locating the service spillway in the outlet works tower instead of constructing a separate service spillway structure.

If a service spillway is incorporated into the outlet work tower, an emergency spillway will be needed. It will be desirable to optimize the size of the emergency spillway and embankment relative to total project costs and to perform subsurface investigations and laboratory testing along the emergency spillway alignment to determine excavation and erosion properties.

The PMF and an estimate of the 100-year flood will be needed for design of a service spillway in the tower, emergency spillway, and embankment. The PMF should be based on new rules and regulations for dam safety being published by the SEO. Consideration should be given to performing a site-specific PMP study in order to reduce the spillway requirements as much as reasonably possible in light of the size of the dam.

Outlet Works Issues The outlet works should be founded on competent bedrock or engineered fill to reduce unacceptable deformations. Subsurface explorations should be completed along potential outlet works alignments and to select either a left abutment or right abutment alignment.

The incorporation of a service spillway into the outlet tower will complicate its configuration and design. Further review of this option should be a priority during pre-design work for the project.

17 Table 1.1 Cost Estimate Glade (177,000 AF Storage) - Feasibility Level

Unit Quantity Unit Price Total Embankment Stream Diversion LS 1 $165,000 $165,000 Dewatering LS 1 $550,000 $550,000 Clear and Grub Foundation AC 102 $750 $76,500 Stripping and Unclassified Excavation CY 1,960,000 $2.00 $3,920,000 Rock Excavation CY 270,000 $5.00 $1,350,000 Foundation Preparation SY 60,000 $11.00 $660,000 Concrete Slurry Wall Cutoff SF 18,000 $150 $2,700,000 Concrete Cap at Zone 1/ Foundation Interface CY 4,400 $250 $1,100,000 Foundation Grouting LF 184,000 $40.00 $7,360,000 Grouting Gallery LS 7,000 $400 $2,800,000 Zone 1 (Core) CY 2,240,000 $2.40 $5,376,000 Zone 2 (Shell) CY 16,205,000 $1.90 $30,789,500 Zone 3 (Filter) CY 530,000 $17.00 $9,010,000 Zone 4 (Drain) CY 220,000 $18.00 $3,960,000 Riprap CY 267,000 $25.00 $6,675,000 Riprap Bedding CY 89,000 $20.00 $1,780,000 Treatment of Soft / Liquefiable Soils Excavation of Liquefiable Soils CY 1,956,000 $2.00 $3,912,000 Backfill Of Liquefiable Soils CY 1,956,000 $2.00 $3,912,000 Seepage Control Blanket - Bellevue Fault Stripping and Unclassified Excavation CY 282,000 $2.00 $564,000 Zone 3 (Filter) CY 50,000 $17.00 $850,000 Seepage Control Blanket - North Fork Fault Stripping and Unclassified Excavation CY 137,000 $2.00 $274,000 Zone 1 (Core) CY 184,000 $2.40 $441,600 Zone 3 (Filter) CY 36,000 $17.00 $612,000 Stability Berm over Lykins Formation Stripping and Unclassified Excavation CY 72,000 $2.00 $144,000 Zone 2 (Shell) CY 142,000 $1.90 $269,800 Zone 3 (Filter) CY 16,000 $17.00 $272,000 Zone 4 (Drain) CY 8,000 $18.00 $144,000 Access Roads LS 1 $100,000 $100,000 Reservoir Clearing Acre 1,700 $600 $1,020,000 Stripping Topsoil Acre 102 $750 $76,500 Erosion and Sediment Control LS 1 $100,000 $100,000 Instrumentation LS 1 $250,000 $250,000 Reclamation LS 1 $200,000 $200,000 Outlet Works LS 1 $15,690,000 $15,690,000 Spillway LS 1 $8,760,000 $8,760,000 Subtotal $115,863,900 Unlisted Items Allowance 7% $8,110,000 Base Construction Subtotal (BCS) $123,974,000

18 Unit Quantity Unit Price Total Construction Contingencies & Multipliers Construction Contingency 16% $19,835,840 Mobilization, Bonds and Insurance 2.5% $3,099,350 Direct Construction Subtotal (DCS) $146,909,000 Field Exploration and Design 4% $5,876,000 Permitting 2% $2,938,000 Legal and Administrative 2% $2,938,000 Construction Management and QA 5% $7,345,000

19 I t \ l=\ I \ I ~\ ·...

I • • J • ~ ~ ~ Proposed Reservoirs _.. -- Canals 0 ~ -- Major Rivers E: Minor Rivers .c: ~ -- Carter Pipeline (No Rednmolion Action Sub-A:t.:mulivet --:r------r-----.~~~------__j PROJECT LOCATION ~ Northern Integrated Supply Project --;::: GE I AND PROPOSED ~t----N~o~rth~e-r-n~C~o~lo-ra~d~o~VV~at_e_r_C_o_n_s_eN__a_n_cy ____ _Jj-~~~~ c~on~su~lta~n=ts~----N-I_S_P_F_A_C__ IL_IT_I_E_s ______J ~~------=D~is~tn~-ct~------L-!P~ro~-e~c~t~0~43~7~1~1!M~a~y~2~0~06~----~F~ig~u~re~1~-1~

0 1500 3000 6000 9000 ------Northern Integrated Supply Project GLADE DAM AND RESERVOIR SCALE IN FEET 1----N-o-rth_e_rn_C_ol-o-ra_d_o_W_a_te_r_C_o_ns_e_rv_a_n_cy----1 GE I c onsultants FOOTPRINT a.: District Project 04371 May 2006 Figure 1.2 ~------~------~----~------._~------~----~

FOREBAY DIVERSION STRUCTURE

POTENTIAL RIPRAP BORROW --.-.-..... FOREBAY

PUMPING ~ STATION

GLADE INFLOW PIPELINE FOREBAY IN PIPELINE

RCC SPILLWAY

~~l---1~- INLET /OUTLET 0 250------500 1000 1500 CONDUIT SCALE IN Fi ET

MULTI-LEVEL INTAKI::/OUTLET TOWER

,-- NWS EL 5235± -DAM CREST EL. 5245±

5550

'\1 ~ 5500 __...------5450 ------J ~ .5 § 5400 ~

1w v ·iS 5350 / i .I 5300 rl IJ

5250

5200 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 Reservoir Volume in Acre-Feet

GLADE RESERVOIR Northern Integrated Supply Project ELEVATION- CAPACITY CURVE Northern Colorado Water Conservancy GE I Consultants District Pro'ect 04371 May2006 Figure 1.4

5600 5600 5532 RESERVOIR EL. 5522 L ···--···--···-- - 5500 5500 - tiw tiw LL.. LL.. '-" 3.5' SLOPE PROTECTION '-" z z 0 0 i= I <( < > > ~ 5400 5400 ~ w EXISTING GROUND w

---ZONE 2 ---

5200 5200

5100 5100

0 50 100 200 300 ZONE 1 - LOW PERMEABILITY CORE (CLAY, SANDY CLAY) ------SCALE IN FEET ZONE 2 - EMBANKMENT SHELL (SAND, SILTY SAND, CLAYEY SAND, GRAVEL, COBBLES, POSSIBLY ROCKFILL)

ZONE 3 - FINE FILTER/DRAIN (WELL GRADED SAND) Northern Integrated Supply Project GLADE RESERVOIR ZONE 4 - COARSE FILTER/DRAIN (WELL GRADED SAND) MAXIMUM DAM SECTION ~---N-ort_h_e-rn_C_o-lo-r-ad_o_W--at-er_C_o_n_se-~-a-n-cy----~~~~~GE I co=ns=u lt=a n~ts ~------~ ci.: District Pro·ect 04371 April 2006 Figure 1.5 ------~------~~~------~~~~~~~~--~~~